NASA Technical Reports Server (NTRS) 19800001984: Electromechanical flight control actuator

The feasibility of using an electromechanical actuator (EMA) as the primary flight control equipment in aerospace flight is examined. The EMA motor de...

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THIS DOCUMENT HAS BEEN REPRODUCED FROM MICROFICHE. ALTHOUGH IT IS RECOGNIZED THAT CERTAIN PORTIONS ARE ILLEGIBLE, IT IS BEING RELEASED IN THE INTEREST OF MAKING AVAILABLE AS MUCH INFORMATION AS POSSIBLE

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R79-2 FEBRUARY'1979

NASA CR-

(NASA-Cft--'(6034$) 'EL,2CTR01 4, ;CHANICAL FLIGHT

N80-10224 :^:-^

C^39TR4L iCfiCtA^CflR Final Report (Delco Electronics, Santa ,Barb^^ k a,' Calif.) 129 p HC g 07,lMa'

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FINAL REPOR (IN TH't 7

ELECTROMECHANICAL FLIGHT CONTROL ACTUATOR

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CONTRACT NAS 9-14952 MODIFICATION NO. FIVE (5S) 1l Submitted to NATIONAL AERONAUTICS and SPACE ADMINISTRATION L.B. Johnson Space Center Houston, n Texas

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FINAL REPORT Ok THE

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FLIGHT CONTROL ACTUATOR CONTRACT NAS 9-14952 MODIFICATION NO. FIVE (5S) o c

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Submitted to NATIONAL AERONAUTICS AERONAUTICS and SPACE ADMINISTRATION -% L.B. Johnso-,i, Space Center Houston, Texas F.

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TABLE OF CONTENTS' Section I

Page INTRODUCTION

1-1

0 21

II

CONCLUSIONS AND RECOMMENDATIONS = ;

2-1

°3 f

III

2.1 ° -C,oncl^t\^';ons

2-1

2.2 `

2-2

SYSTEM FUNCTIONA L D9SCRIPTION

3 -1

3.1.

3-1 3-2 3-4 3-6 3-6 3-7

"r

3.2

IV

4.1

471 4-5 4-9 4-10

4.2

Motor-Gearbox Assembly Motor 4. 1. 1 Shaft" Encoder 4.1.-2 4.1.3 Gearbox 4, 1.4 Tachometer 4. 1.5 Position Transducer Electronics 4.. 2. 1 Power `Electronics 4.2 2 Low - Level Electronics

EQUIPMENT MECHANIZATION 5.1

5.2

Electromechanical Actuator Current Command Rate Lim'ater r` 5. 1. 1

Power Electronics Mechanization High Power Motor Driver 5.2Y 1 5.2.2 Base Driver Power Supply 5,.,2.3 Base Driver Circuit 5.3 .-Power Converter Control Current Protection `` 5a 3. 1 a

._

4-1

`

V

EMA Functional Description System Operation 3. 1 1 3. 1.2 Current Source Power Converter PowerConverter Functional Description _ Motoring.Operation _ 3, 2. 1 Regenerati'Ve Braking 3.2.2

EQUIPMENT DESCRIPTION

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T,;ecox i adations

4-11

4-12 4-12 4-13 4-15 5 1`' , ` 5-1

5-1 5-8 5-8 5-10,. 5-12 5-12 5-14

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TA13LE Or CONTENTS (cont'd) J

Section

VI

Page

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Chopper Control

Rotor Position Sensor; Tachometer Monitoring Points and Controls

5-15 5-22 6-1

6.1 6.2

Safety Considerations Start-Up Operations

6-1 6-2

6.2. X' 6.2.2 G'. 2.3

6-2 6-3 6-3

Cooling Air Input Command Signal

Turnon

Shutdown Operations

6-3

TESTS AND TEST RESULTS

7-1

7.1 7.2

Introduction Motor Performance Tests

7-1 7-1

7.2.1 7.2.2 7. y.3 7.2.4

Ritll Power Motoring Tests

Motor Torque Characteristic Tests Motoring Tests ;

7-1 7-4 7-4 7-4

7.2.5

Regeneration Tests

7-8

7.2.6 7.2.7

EMA Torque Control Tests Motor Speed Anomaly

7-8 7-11

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7.3

Commutation Angle Control Tests

Servo Performance Tests 7.3.1 7. 3. 2 7.3.3 7.3.4 7.3.5 7.3.6 7.3.7

.,

5.14

4,'^IKA OPERATING INSTRUCTIONS

6.3 VII

5.3.2

5.3.3 5.3.4

Appendix:

frequency Response Tests Step Response Tests Linearity Tests Hysteresis Tests Threshold Tests Output Velocity Test Position Null Test

System Schematics

_ 7-11 7--11 7-17 7-35 7-38 7-38` 7-41 7-43

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LIST OF ILLU'STRATION ` S ' ,. Page

Figure 1-1 0°-1 3-2 3-3 3-4 3-5 4-1 4-2 4-3 °4-4 4-5 4-6 4-7 4-8 4-9

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4-10

Rotor

4-11 .

Rotor After Banding

4-12 4-13 4=14 4-15 4-16

Stator Without Windings Stator with"Windings _ Digital Shaft Encoder Side View of Motor-Gearbox View of Motor-Gearbox Showing Tachometer and Position Feedback Transducers-, 'l Single-Channel Electronics Test Setup Single-Channel Power Electronics Assembly, Power Transistor Side Single-Channel Power Electronics Assembly, Driver Side Transistor Base Drive Power Output Circuit Card Assembly Transistor Base Drive Power Oscillator Circuit Card Assembly Lover-Level Electronics Enclosures, Rear View Low-Level Electronics Enclosures, Front View Idealized EMA Block Diagram EMA Mechanization Diagram Adjustable Current Command Hate Limiter EMA Operating Regions INI < LXI and_INI > I X I

4-17 4-18° ;.

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Four-Channel Electromechanical Actuator Bloch-biagram Idealized Motor Phase Currents Simplified' Block Diagram of the EMA Controller Block Diagram Typical Power Converter Waveforms Power Converter Motor-Gearbox Assembly Output Shaft View of Motor Motor and Shaft Encoder Side View of Dynamometer Top View of Dynamometer Close-Up View of Delco Dynamometer EMA Motor with Shalt Encoder Motor Shaft Rotor

4-19 4-20 4-21 4-22 4-23 5-1 5-2 5-3 5-4 5-5

Before

Banding..„

1-2 3-2 A 3-3 ^13-4 3-5 3-6 4-1` 4-2 4-2 4-3 4-3 4-4 4-4 4-5 4-5 4-6

4-7

4-7 4-8 4-9 4-10 - 4-11 4-13 4-14 4-14 4-15_ 4-3.5" 4-16 4-17 5 -2 5-4 5-5 5-6

NCCW and NCW Conditions TCCW and TCW Conditions High Power Motor Driver Base Driver Power Supply

5-7 5-7 5-8 5-9 5 - 11

5-10

Base Driver Circuit

5-13

5-11 5-12

Derivation of Computation Decoding from the Optical Encoder Decoder Timing Diagram

5-19 5-20

5-6 5-7 5-8 5-9

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LIST OF ILLUSTRATIONS (contld) gage

5-13 7-1 7-2 7„-3 7-4(a) 7-4(b) 7-4(c) 7-4(d) 7-5(a) 7-5 (b) 7-5(c) 7-5(d) 7-6(a) 7-6(b) k

7-P(c) i 7-6(d) 7-1O a 7-7(b) 7-7(c) 7-7(d) 7-8 7-9 7-10 7-11

Derivation of Velocity (Rate) Signal from the Optical Encoder Motor Currents for Several Commutation Angles Typical Frequency Response Measurements Position Transient Response Design Goal Step Response to 2% Command (I =6,100 A/deg, Kv 0. 17 A/r/min, 7 = 0.00 seco^d) Step Response to 3% Command (K =6,100 A/deg, Kv = 0. IT A/r/min, r = 0.00 second) Step Response to 4% Command (K + 6100) A/deg, K = Q. 17 A/r/min, T = 0. 00 secelid) Step Response to 5% Command (K + 6100) A/deg, K v 0. 17 A/r/min, T = 0.00 second) Step Response to 2% Command (I = 12,000 A/deg, I^v = 0.27 A611/min, T = 0.00 sec nd) Step Response to 3,9o' Command (K = 12,000 A/deg, 0. 00 second) Kv = 0.27 A/r/inin 12,000 A/deg, Step Response to 4 6 Command ( Kv = 0.27 A/r/min, 'P = 0.0.0. sec(Ynd) 12,500'A/deg, Step Response to-5% Command ( T' = 0, 00 second) v = 0.27 A/x/min, T iStep Response to 2% CommarAd •(Kp = 6,100 A/deg, K = 0.22 A/r/min, 7- 0.00` 'second) Step Response to 3 17o Command (K = 6,100 A/deg,' K': = 0.22 A/r/man, T = 0. 00 second) Step Response to 4% Command (Kp = 6, 100A/deg, K = 0.22 A/r/min, T 0. 00 second) Step Response to 5% Command( 6,100 A/deg, ^',f^r Kv = 0.22 A / r / min 7 = 0. 00 second ) Step Response to 2%Command K_ 6 100 / A de ? g^z ( Kv 0.22 A/r/min, r = 0.00 second) Step Response to 3% Command (K 6. 100 A/deg, K = 0.22 A/r/min, 7- - 0. 00 second) Step Response to 4% Command ( = 6,100 A/deg, Kv = 0.22 A/r/min, t = 0. 00 second) Step Response to 5% Command (K 6,100 A/deg, Kv = 0. 17 A/r/min, r = 0. 00 second) Response Time of EMA as a Function of Step Command Size Hysteresis Test Displays 5 Input and Output Waveforms from Threshold Tests at an Amplitude of 0. 016% of Full Travel Waveforms from Output Velocity Test

5-21 7-3 7-12 7-17

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7-20 7-21 7-22 7-23 7-24 "

7-25 7-26-:-)

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LIST OF TABLES Table 4-1 4-2 5-1 7-1

7-2 7-3 7-,4 7-5'^- 7-6 7 , 7-(a) 7-7(b) 7-7(c) 7-7(d) 7-7(e) 7-7(f) 7-8

Title

Page

Tachometer Specifications Position Transducer Specifications Definitions Data from Comm i is aa,--paontrol Tests

a

4-12 4-12, 5`-3

7-2 7.5 7-6 7-7 7-9 7-10 7-14 7-14 7-15 7-15 7-16 7-16 7-37

Data from Full POr r motCl'C - Tests Data from Motor Toque Characteristic Tests Data from Motoring Tests Data from Regeneration Tests Data from Torque Control Test Data from Frequency, Response Tests Data from Frequency Response Tests Data from Frequency Response Tests Data from Frequency Response Tests Data from Frequency Response Tests Data from Frequency Response Tests Data from Linearity., Tests

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SLTION I

3

INTRODUCTION

A technology program has been conducted to investigate the feasibility of using electromechanical devices as primary flight control actuators for aerospace vehicles.

This program was initiated after

Studies of electrohydraulic and

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electromechanical systems had indicated that a highly efficient battery-powered u

electromechancial actuation system hadp otentially significant ad*' st ages over the electrohydraulic actuation system.

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In addition`to its potential weight

reduction (extremely important in many aircraft, missile, and spacecraft applications) the Electromechanical Actuator (EMA) shows great promise in terms of reliability and maintainability.

However, before such an°ap proach could be

seriously considered, hardware feasibility of electromechanical actua'c r concepts suitable for aerospace vehicle applications had to be demonstratedr

The feasibility demonstration has been'conducted in two phases.

},1

Delco's earlier<.,

efforts (reported in R78-1, "Final Report on the Electromechanical Flight Control Actuator", January 1978) resulted in the development of a four-channel electro:s

,

4`

mechanical actuator (Figure 1-1).

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This actuator follows a proportional control

command with minimum wasted energy.

Each of the four channels has independent

drive and control electronics, a brushless electric motor with brake, and velocity andposition feedback transducers. r

putput velocities of the motors.

A differential gearbox sums the

Normally, two motors are active and the other

two are braked.. A 270 Vdc battery powers the actuator.

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The major tasks conducted in the initial phase of the program included: f

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Design and fabrication of the four-channel actuator,

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Design and installation of nL. cessary test instrumentation,

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Modification of the NASA-furnished actuator test stand,

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Development of mathematical models of the actuator and its

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major subsystems, r

The design, fabrication, and testing of a state-of-the-art singlechannel power electronics breadboard

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a CONTROL COMMANDOELECTRONICS COMMAND

CONTROL ELECTRONICS MOTOR

MOTOR

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BRAKE w

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(GEAR BOX (ASSEMBLY POS IT ION TRANSDUCERS----

DIFFERENTIALS

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OUTPUT HINGE

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ACTUATOR I L— BRAKE BRAKE MOTOR

COMMAND

COMMAND

MOTOR

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CONTROL ELECTRONICS _

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CONTROL ELECTRON ICS

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Four-Channel Electromechanical Actuator Block Diagram

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Planning and cducti`ng des'^gn- verification tests of the four-channel a tuator,



Participation



Documentation of the program with plans, reports,,,and an

formal program reviews,

operations manual.

The initial phase of the program was highly successful. As a result, a second phase of the program was initiated in March,,1978. The major tasks for this phase of the program included:



Redesigning the EMA motor to utilize improved permanent magnet materials,



}

Fabricating, assembling, and testing the improved motor,



Designing, developing, and testing an improved rotor position ^f

sensor/tachometer, •

Analysis and design of the necessary equipment to complete'a << gi'ngl e-c'nannei

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EMA using the si ngl e-channel power electronics

breadboard, U

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Fabrication and assembly of the single-chantlel EMA,



Planning and conducting system tests to, determine,the performance' characteristics of the single-channel EMA,



Participating in conferences and documenting the program activities

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with necessary plans and reports.

This report summarizes the results of the second phase of the EMA development program. , However, ;or purposes of clarity and completeness, some of the material reported earlier is also included in this report.

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SECTION II CONCLUSIONS AND RECOMMENDATIONS

2.1

CONCLUSIONS

The Electromechanical Flight Control Actuator prq.T*-ram has clearly demonstrated the feasibility of meeting stringent space vehicle flight control actuator performance requirements using advanced motor and power electronics concepts.

During the most recent phase of the program, a single-channel Electromechanical Actuator`-t'EMA) has been developed and tested at full output power levels (17 hp). .

The

These'tests have shown that the EMA exceeded virtually all its design goals. design goal for displacement linearity is 1% of full travel,

` The worst-case

measured deviation was found to hQ 0.07%, and the standard deviation was determined to be 0,018%. __-

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The ci ,,,s 9 n g 9 oal for system threshold is 0.0275'de 9ree, and

the EMA easily met this requirement. The measured threshold was well under l1ll 0.005 degree. The position null^;design goal is"0.275 degree, and this require- meat was also met.

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The hyst^^res ,k. . design goal is..0.0275 degree, p.nd-measured

hysteresis was 0.002 degree .\

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The measured frequency response characteristics of the single-channel EMA also exceeded the system design goals.

By adjusting system gains, time constants,

and other parameters, the frequency response can be adjusted over rather wide limits.

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Fora typical,set of adjustments,, the -3 dB bandwidth was slightly

greater than 6 Hz compared with a design goal of atleast least 4 (iz.

The

phase characteristics for the same conditions also met the design goals, with the measured phase lag of 45 degrees occurring at 2.4 Hz compared with a design goal of ;at least 1.6 Hz.

The measured step response characteristics of the EMA

were the only characteristics that did rot exceed system design goals. , , The two w

most critical step response design goals are overshoot and time to reach 85% of steady-state travel.

The design goal for overshoot is 25% or less and the EMA

can easily meet this requirement with a variety of gain , and compensation adjustments.

The design goal for the time to reach 85% of steady-state travel is 150

milliseconds.

The EMA,can achieve this goal for step amplitudes less than 3.8%

of full travel, but the design goal was to meet this :requirement for step input R79-2.

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DELCO ELEC IRON S DIVISION a SANTA BARBARA OPERATIONS s GENERAL MOTORS CORPORATION °

commands ranging from 2 to 5^ of full travel.

To meet this design goal, the gear

ratio of theEMA,p,, uld have to, be reduced by about

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(5.0

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3.E)f 5:0^= 24%

`Since the EMA gear ratio is-very large, the reflected load characteristics are negligible, and have little effect on the acceleration or velocity response of d`

the

_system,



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Perhaps the most important conclusion that can be drawn is that thi s program' has clearly flight control actuator Y demonstrated that a high-power,hi h i gh-performance 9 h- p 9 is feasible using the

technology available today. y.

3

With the continuing impro+re--

ments which are being made in magnetic materials and in power semiconductirs, it

^.-

is clear that EMA appr;aoches are technically sound.

For certain applications,

they may well become the most suitable, choice from among the wide'range of available actuation methods. i

4

2.2 °

RECOMMENDATIONS

-

The feasibility of the EMA has been demonstrated during this program.

The next

recommended major effort is the design, fabrication, and testing of a prototype unit suitable for flight testing. " ;^•

This effort+ would a"stablish the size, weight,

and environmental characteristics

of a state-of-the-art electromechanical actuator

concept, and would[also demonstrate the performance capabilities that can be achieved.

After laboratory tests have been made (i eluding flight simulation

tests), actual flight tests should be conducted.

Thet,e tests should be made on

an aircraft having suffi ^;ient space;; avai 1 abl a for moni £orjng `-"and recording the

'

behavior of the actuat^' Ii f`under the full range of flight conditions typical of high performance aircraft.

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SECTION III SYSTEM FUNCTIONAL DESCRIPTION

3.1

EMA FUNCTIONAL 'DESCRIPTION

The most unique feature of the EMA is its use of a brushless synchronous motor having a permanent magnet rotor. The stator of this machine is similar to that of a conventional three-phase synchronous'or induction motor, and is simple in construction and windings. The rotor has permanent magnet poles made of samarium cobalt, which is an extremely effective magnetic material, resulting in a lightweight, low-inertia machine with very high efficiency. The ceramic-like magnets are bonded to a solid steel shaft. A fiberglass band is wrapped around the rotor to aid in resisting centfffugal forces, and provides a smooth, cylindrical rotor surface to minimize windage losses. Brushes and commutator are eliminated in this machine through the use of the rotor position sensor (RPS) and solid-state electronics. The stator windings of the motor are excited by three-phase waveforms to create a rotating magnetic field. As the rotor moves, the RPS sends signals to the control electronics to indicate which windings should receive excitation to produce the torque required by the load. Thus, the machine operates in a manner similar to a conventional do motor, except that the conventional commutator and brushes are replaced by the RPS and control electronics. The resulting machine is capable of operating at much higher speeds than one having rotor windings and a commutator. Because the permanent magnet rotor has o 'virtually no losses, the thermal problems associated with cooling the machine ' are greatly simplified. Virtually all losses in the machine occur in the stator; therefore, cooling ­'_i"s easily accomplished by forcing air to flow througi? the stator slots which are only partially filled by the machine's windings.

The ,power control electronics for the machine are relatively simple,

For servo

control p^ljrposes it is very convenient to provide a controlled torque mode of opera

on.

This is easily accomplished in the permanent magnet motor because its

output torque is proportional to the current in the stator windings. -

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rotor position, two of the stator windings receive excitation.

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Idealized motor

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Figure 3-1. Idealized Motor Phase currents

phase currents are shown in Figure 3-1. For example, at electrical angles be-

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tween 0 and 60 0 , the motor current flows into winding A and out through winding B. `During the next interval, from 60 to 120

0 , the current continues to flow into

wijiding A, but..out through winding C. The current is thus commutated at intervals of 60 electrical degrees to provide three-phase current waveforms. The„magnitude U

of, f the current is controlled to produce the desired torque, and the rotor posit-un'sensoy.-a,nd control electronics switch the controlled current through the

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appropriate pai`'r' of windings ,.

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3.1.1 SYSTEM OPERATION

Figure 3-2 is a simplified system block diagram -of the electromechanical actuator. For convenience, all torque, inertia, and motion variables are referenced to the load., Linearized load effects (viscous damping, load spring and steady-state hinge moments) are represented, and the velocity and position feedback paths are also shown. ,a

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The position coniniand ap# position feedback signals are compared to form a position error signa l. This signal is amplified and combined with the velocity feedback

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° signal to develop a current command signal. The current source develops a motor current in response to the current command signal. The motor current produces ,a torque which accelerates the reflected inertia of the system and overcomes the

reflected hinge moment of the load CURRENT SOURCE POWER CONVERTER

3.1.2

ronous motor is driven bY a currentt source power convertp The brushless, self-synchronous er. The

.,

is achieved with an inductor-coupled pulse

current source pow or

width modulator (chopper) and inverter (Figure 3-3). The chopper establishes!a do current level in the coupling inductor in response to a torque error signal.

The inductor current ,--is processed by the inverter to form a si x-step motor current f

waveform (Figure 3-4).

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TORQUE1CURREIT) COMMAND

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TORQUE ERROR FIELD MAGNET •_

270 Vdc

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INPUT FILTER

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CURRENT

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INVERTER

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SIGNALS

SENSOR

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SIGNAL

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A. COUPLING INDUCTOR CURRENT

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60

90

120 150 180 210 240 270 300 330 8 — ►

B. MOTOR PHASE CURRENTS

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Figure 3-4. Typical Power Converter Waveforms

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DELCO ELECTRONICS DIVISION + SANTA BARBARA OPERATIONS • GENERAL MOTORS CORPORATION 3.2

POWER CONVERTER FUNCTIONAL DESCRIPTION

Figure 3-5 is a simplified schematic diagram of the power converter. QAP through QCN are connected to form a three-phase inverter. The inverter controls the currents in the motor stator windings. Switches QM1 and QM2 control the current through the inverter during motoring operation, and QB1 and QB2 control the inverter current during regenerative braking.

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Figure 3-5. 3.2.1

Power Converter

MOTORING OPERATION

'During 9 motori n 9 g o pperation, if the current in the current source inductor LM is Tess than the commanded value, either QM1 or QM2 is turned on; this applies full battery voltage to the coupling inductor LM. i

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in the inductor as indicated in Figure 3-4.

Therefore, current increases

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Hysteresis in the control

circuit allows the current to "^bu Id up to a preestablished level which is R%9-2

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DELCO ELECTRONICS DIVISION SANTA 13ARBARA OPERATIONS

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slightly greater than the commanded current. At this point, the transistor'is turned off. ,The current which is flowing through the inductor at the switching

f

time then flows through diode DRM. The current then decreases to value slightly, below the commanded current, at which point eitherQM1 or QM2is again turned on, thus restarting the cycle. QM1,.,-and QM2 operate alternately, thereby reducing

3

their av6 age dissipation.

Figure 3-4 shows the coupling inductor current waveform, as well as the motor phase currents.,

The current in the inductor is routed through the proper motor windings°by the inverter transistors QAP through QCN. These transistors are turned on and off by C

signals which are derived from the Rotor Position Sensor.

2,_2

REGENERATiVE BRAKING

When the load is capable of returning energy to the battery, the power converter operates in a regenerative mode. In this mode, the inverter transistors (QAP ,3

through QCN in Figure 3-5) are all turned off. The antiparallel diodes of QAN, QBN, and QCN in conjunction with diodes DRE, DRF, and DRG then act as a threephase full-wave rectifier load on the motor (which is operatingas a permanent magnet generator). Current through the coupling inductor LB is controlled by transistors Q81 and QB2 and the braking diode, DRB. If the current in the coupling inductor LB is less than the commanded current, one of the braking transistors is turned on. Again, hysteresis designed into the control circuitry

r

allows the current to build up in the inductor to a level slightly greater than the commanded value. At this point, the braking transistor is turned off, and the current flowing in the inductor now flows through diode DRB back into the battery. When the current decreases to _a value somewhat lower-than the commanded

r

value, the braking' transistor is again turned on, thus restarting the current

} n

,control cycle. The braking transistors QB1 and QB2 are operated alternately to reduce their average power dissipation.

R79-2 ti

3-7

WC

w^ DELCO ELECTRONICS DIVISION • SANTA BARBARA OPERATIONS • GENERAL MOTORS CORPORATION

i SECTION IV EQUIPMENT DESCRIPTION

i i

4.1

MOTOR-GEARBOX ASSEMBLY

The motor-gearbox assembly is shown in Figure 4-1. The shaft encoder is located

at the right end of the assembly, and it is attached to the shaft of the EMA motor by a bellows coupling. The motor windings are brought out to a terminal

i

block on the stand. The instrument gear train is shown at the left side of the assembly. A dial indicates the position of the output stage of the gearing.

i i az

t i w.

i i i i

Figure 4-1. Motor-Gearbox Assembly

Figures 4-2 and 4-3 are two views of the motor and shaft encoder before attaching the gearbox assembly.

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R79-2

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DELCO ELECTRONICS DIVISION • SANTA BARBARA OPERATIONS • GENERAL MOTORS CORPORATION

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Figure 4-2. Output Shaft View of Motor

I I 1 1 1 1

I t 1

Figure 4-3. Motor and Shaft Encoder

R79-2

4-2

'I OELCO ELECTRONICS DIVISION • SANTA BARBARA OPERATIONS • GENERAL MOTORS CORPORATION

During performance testing of the EMA motor it was mounted on Delco's dynamometer

I

(see Figures 4-4 through 4-7).



fir' AC 1

s

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VIA Figure 4-4. Side View of Dynamometer

i i t

WAS

r ^ V

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Figure 4-5. Top View of Dynamometer

R79-2

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DEL-CO ELECTRONICS DIVISION • SANTA BARBARA OPERATIONS • GENERAL MOTORS CORPORATION

a^ 1 1

1 i I Figure 4-6. Close-Up View of Delco Dynamometer

1

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P79-2

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DELCO ELECTRONICS DIVISION • SANTA BARBARA OPERATIONS • GENERAL MOTORS CORPORATION 4.1.1

MOTOR

Figure 4-8 shows the motor shaft before the permanent magnets are attached. Since the motor is an eight-pole machine, the central portion of the shaft has an octagonal ,Cross section. Figure 4-9 shows the rotor with the samar = um cobalt

i a

i i Figure 4-8. Motor Shaft

K

Figure 4-9. Rotor

R79-2

4-5

DELCO ELECTRONICS DIVISION • SANTA BARBARA OPERATIONS • GENERAL MOTORS CORPORATION

M magnets attached. The samarium cobalt material has a high energy product (26 '

million. Gauss oersteds). The magnetic blocks, approximately 118 inch long, are bonded to the rotor shaft and then ground to a cylindrical form. Brass end discs

'

are bonded to the magnet assembly and retained by snap rings (Figure 4-10).

J i

Figure 4-10. Rotor Before Banding The end discs provide material which can be removed during dynamic balancing; they 1

also reduce windage losses and provide a termination point for the rotor banding.

y The banding ', , high-strength glass filament winding which is wound under tension. The banded rotor (Fi gure 4-11) is ground to provide an accurate diameter for mechanical clearance in the stator bore.

The stator is shown in Figure 4-12; the stator laminations are 7 mils thick and are Vanadium Permendur. Figure 4-13 shows the stator with windings in place.

The motor assembly is 9.25 in. long. The motor frame diameter is 3.75 in. and the rotor weighs 17.2 1b.

I

R79-2

4-6

DELCO ELECTRONICS DIVISION • SANTA BARBARA OPERATIONS • GENERAL MOTORS CORPORATION

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Ii OLI C 0 ELECTRO 4CS CIVISION • SANTA BARBARA OPERATIONS • GENERAL MOTOR S CORPORATION

I 11

I Figure 4-13. Stator With Windings

R79-2

I

1 1 i

DELCO ELECTRONICS DIVISION • SANTA BARBARA

4. 1.2

OP ERATIONS • GENERAL MOTORS CORPORATION

SHAFT ENCODER

The shaft encoder is shown in Figure 4-14.

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r,gure 4-14. Digital Shaft Encoder R79-2

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4-9

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DELCO ELECTRONICS DIVISION - MANTA BARBARA OPERATIONS - GENERAL MOTORS CORPORATION

The encoder has a three-bit output. An absolute reference point is provided (once each revolution), and the other two bits provide incremental position data with a resolution of 0.25 mechanical degrees (1,440 pilses per revolution).

4.1.3 i

GEARBOX

The gearbox is shown at the left end cf the motor-gearbox assembly (Figure 4-15).

i

i r 7

A

i ix i

i

i

Figure 4-15. Side View of Motor-Gearbox i

The tachometer is mounted on the lower left section of the gearbox, and the r

position feedback transducer is located on the upper left section of the geartrain.

i

The gear reduction from nx)tor to output is approximately 3600:1. Figure 4-16 is a vie!J of the motor-gearbox assembly showing the position feedback transducers and the tacnoinet.er.

i

R79-2

i

4-10



DELCO ELECTRONICS DIVISION • SANTA HARBARA OPERATIONS • GENERAL MOTORS CORPORATION

131

^0 ^uW 3

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Figure 4-16. View of Motor-Gearbox Showing Tachometer and Position Feedback Transducers

4.1.4

TACHOMETER

The electromechanical tachometer is directly coupled to the nx)tor shaft. It has a highly linear speed/voltage characteristic, operates bidirectionally, and is designed for long operating life. Important specifications for the tachometer are listed in TaJle 4-1.

In addition to the electromechanical tachometer there is an output position rate signal which is derived from the rotor shaft position encoder. This circuitry is described in paragraph 5.3.

R79-2

4-11

DELCO ELECTRONICS DIVISION • SANTA BARBARA OPERATIONS *GENERAL MOTORS CORPORATION

Output voltage gradient

7.0 V/1000 r/min

Output impedance, maximum

350 ohms

Output linearity, 100 to 6,000 r/min

0.1 )

Ripple voltage, maximum "is

3%

Bidirectional output voltage error

0.25%

Maximum speed

12,000 r/min

Friction torque, maximum

;; 0.25 oz-in.

Armature inertia, maximum

6.5 gm-cm

Weight, maximum

M, nx

Mechanical natural frequency, minimum

1,000 Hz

Life expectancy at 3,600 r/min

10,000 h

Table 4-1.

4.1.5

^

j

Tachometer Specifications

POSITION TRANSDUCER

' p osition transducer consists o f two precision servo potentiometers ganged on The a single shaft.

The transducers utilize a;film,resistive element to achieve

virtually infinite resolution.

Some of the aJor features of the position trans-

ducer are listed in Table 4-2.

2.0 i

Resistance (each element)

10K ohms

Linearity

0.25

El ectri ca1^ ' Travel

3400

Standard Ulfe Expectancy

10 M revolutions

Table 4-2.

4.2

n.

Diameter

Position Transducer Specifications

ELECTRONICS

The electronic equipment for the EMA i s shgyn in Figure 4-17. electronics are housed in the black enclosures,

The low-level

and the power electronics

breadboard is the large assembly on the table in the foreground.

.

_

R79-2



4•-12

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DELCO ELECTRONICS DIVISION • SANTA BARBARA OPERATIONS • GENERAL MOTORS CORPORATION

C1

t i i i i i t t

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Figure 4-17. Single-Channel Electronics Test Setup

4.2.1

POWER ELECTRONICS

A closer view of the power electronics assembly is presented in Figure 4-18. The power transistors are mounted on the heat sinks which are located on the top side of the assembly. Figure 4-19 shows the reverse side of the power electronics

assembly. This view shows the power transistor driver circuit cards. Close-up views of this card are presented in Figure 4-20. The power oscillator circuit card assembly is shown in Figure 4-21.

R79-2

4-13

DELCO ELECTRONICS DIVISION* SANTA BARBARA OPERATIONS • GENERAL MOTORS CORPORATION

Figure 4-18. Single-Channel Power Electronics Assembly, Power Transistor Side

to

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Figure 4-19. Single-Channel Power Electronics Assembly, Driver Side R79-2

4-14

DELCO ELECTRONICS DIVISION • SANTA BARBARA OPERATIONS • GENERAL MOTORS CORPORATION

Fiyure 4-20. Trdnsistor Base Drive Power Output Circuit Card Assembly

Figure

4 - 21. Transistor Base Drive Power Oscillator Circuit Card Assembly

R79-2

4-15

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DELCO ELECTRONICS DIVISION • SANTA

4.2.2

13AR13ARA

OPERATIONS • GENERAL MOTORS CORPORATION

LOW-LEVEL ELECTRONICS

The low-level electronics circuits are contained in the four enclosures shown in Figures 4-22 and 4-23. One box contains the rotor position sensor electronics, one houses the servo electronics, and the other two boxes control the chopper and

inverter power switches. As can be seen in these figures, test jacks are avail5'

able on the panels, and the RPS panel displays the motor shaft speed, the rotor

ancle, and the inverter switch drive conditions.

L . L.i_ p

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1:1

^:.. 13

Figure 4-22. Low-Level Electronics Enclosures,

Rear View I

R7°-2

4-16

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DELCO ELECTRONICS DIVISION • SANTA BARBARA OPERATIONS • GENERAL MOTORS CORPORATION

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T' ,-r-11 .,. l 'I'TIT''4•-T.l.,, I II .j^^ ». ,41,4.7 L_.:.1.1.?'.2- ;_:.'t. I1_^ T i

Figure 4-23. Low-Level Electronics Enclosures, Front View

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4-17



C, DELCO ELECTRONICS DIVISION S SANTA BARBARA OPERATIONS a +GENERAL. MOTORS CORPORATION

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SECT I O N V

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EQUIPMENT MECHANIZATION 5.1

ELECTROMECHANICAL ACTIATOR

The electromechanical actuator (EMA) is a positioning servo system, and its output motion is proportional to an analog input command. An idealized block diagram of the EMA is shown in Figure 5-1. Table 5-1 defines the symbols used in this diagram. Both position and velocity feedback are used for control purposes, and the motor is controlled by means of its armature current. In the idealized case,,the deflection command is compared with the actual output position to provide a position error. Velocity feedback is also used, and the resulting system error signal is used to develop a motor current command. The idealized current controller forces the motor current to follow.the command ,, resulting9 in motor output torque. This output torque accelerates the system inertia and produces output motion.

Figure 5-2 i.s a block diagram showing the actual EMA mechanization. Most of the transfer functions are self-explanatory. The definitions for the symbols a

used 7-, this system are given in Table 5-1. Although most of the subsystems

k

showrn Figure 5-2 are straightforward, several are somewhat complex, and are therefore discussed in detail in the followi,n,p pa ►=agraphs.

5.1.1

CURRENT COMMAND RATE LIMITER

The current command rate limiter, shown to block diagram form in Figure 5-3, prevents sudden changes in the commanded control current.

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DELCO ELECTRONICS DIVISION • SANTA BARBARA OPERATIONS • GENERAL MOTORS CORPOkATION

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SYMBOL MBOL

DEFINITION

DC

Load deflection'command, degrees

PERR

Load position error, degrees

DE

Load,,deflection angle, degrees

KE

Gain coefficient, A/degree

KR

Gain coefficient, A/r/min

K

Position gain, A/degree

p

K

Velocity gain, A/r/min

ICMD

Current command (prior to limiting), amperes

ICMD1

Current command (after command rate limiting Yo amperes

IT

,ICMDL

s

c

= J

=

Current command (after amplitude limiting) amperes

IMC

Motoring current command,, amperes

Al

Gear ratio, motor-to-load deflection

A2

Gear ratio, position pickoff potentionleter-to-load

IM

Motor current (current into,inverter); •. amperes

DDOTE

Angular velocity of load, deg/s

.

7

Dominant time constant, second

T

Table 5-1. Definitions

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DELCO ELECTRONICS DIVISION SANTA BARBARA OPERATIONS

• Ga ENEIRAL MOTORS CORPORATION Adjust

E

in

tCMD

10

13.5

—13.5

0.5

700 to x;000 1 S «^

E out

Figure 5-3. Adjustable Current Command Rate Limiter

When the system is operating in its linear region, its transfer function is

1

1

Eout _

E

in

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I+T

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rider C::.

Tmin

27(2j000)

.000019

and r

T max _27 180

.00021

P,

When limiting action takes place iii, for example, a sudden large change in_. current command occurs); the output voltage changes at a rate given by

out'

to

`

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R79-2

max 13.5 x 2,000 = 27000 V/s

out m in

= 13.5 x 180 = 2,430 V/s

5-5



• DELCO ELECTRONICS DIVISION

S ANTA BARBA RA .OPERATIONS • OENiERAL MOTORS CORPORATION

With the scaling used in this circuit, 1 V represents 10 A; therefore, the current I.

command rate limit i s I

10 x 27,000 A /s = 270 Aims

-

calr^^and max

`

.

and

I

5.1,2

= 10 x 2,430 A/s = 24.3 A lms

command min

SYSTEM OPERATING MODES

The EMk operates in three different modes:

y `

a



Motoring,



Plugging,

9

Regenerating.

These basic operating regions are illustrated in Figure 5-4. In the first quadrant, the` torqu,7. produced by the machine is"in the same direction the rotor is turning, resulting in normal motoring operation. If the motor is operating at low speed in the second quadrant, the motor torque opposes the velocity, and plugging operation

MOTOR TORQUE OR CURRENT

REGENERATING

PLUGGING

MOTORING

-► SPEED

MOTORING

NPLUGGING

REGENERATING/

Figure 5-4. EMA Operating Regions

R79-2



„ OEL.CO ELKCT"ONICS DIVISION SAh i A BAROARA OPERATIONS • GENERAL, MOTORS CORPORATION

results, At higher speeds in the s ►„cond quadrant, a regenerative braking mode is used during which ener0Y from the system is returned to the battery, Similar modes are indicated in Figure 5-4 for the this'd and fourth operating quadrants.

Since the EMA operatgs somewhat differently ip each operating region, it i` neces-' sary for the low-level control circuits to establish which region is currently being encountered. This is accomplished by comparators that establish which one of the following speed regimes (as illustrated in Figures 5--5 and 5-6 exists:



INI
4 00

r/min)

s

(:1NI>jX) N`sCW

• a

N is CCW CURRENT

1 ED

x

-X

It

Figure

5-5.

(NI

JX( and `'(N(

JXJ

CURRENT

f

CW

ccw

SPEED

,t

Fig ure 5-6, NCCW and NCW Conditions

1 In addition, the current command is testedJy a comparator to establish which of F.

4.

the following regimesj^as illustrated in Figure 5-7) is active: Y ® TCCW

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DELCO ELICC7RONICS DIVIW', N SANTA lo'TARDARA OPERATIONS • GENERAL MOTORS CORPORATION

CURRENT

'[D

Figure 5-7. TCCW and TCW Conditions The regenerative and plugging modes are then determined using the following Boolean relationships; 6

RGN2 RGN4

r

RGN

r

• •

TCCW-NCW•INI

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TCW•NCCW-INI>IXI RGN2 + RGN4

PLUG2 = TCCWNCW.INI
I,.

= TCW*NCCW•'INI'
PLUG ='PLUG2 + PLUG4

j

5.2

POWER ELECTRONICS MECHAN^ZAATIQN

The power electronics for the EMA consists of the three major subsystems described in the following paragraphs,

5.2.1

HIGH POWER MOTOR DRIVER

i The schematic diagram of the motor drive circuit is given i'n Figure 5-8. The inverter uses six power transistors (QAP, QAN, QBP, QBN QCP, and QCN). During' motoring, the current through the motoring inductor, LM, is controlled by the two mota^ing chopper transistors, QM1 and QM2. It Is possible to drive QM1 and QM2 in several ways, but in this system they are time-shared, operating alternaT t

tely. Braking current through LB is controlled by the two braking chopper transistors QB1 and Q82. Noninductive current viewing resistors (CVRs) are used_to.sense 'currents IMB, IAN, IBN a and ICN

Motoring and braking control

circuits use the signals from these CVRs for control purposes.

R79-2 }



DELCO ELECTRONICS DIVISION • SANTA BARBARA OPEI RATION^ hw,•GENERAL MOTORS CORPORATION

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DELCO ELECTRONICS DIVISION SANTA BARBARA OPERATIONS *GENERAL MOTORS CORPORATION

In mechanizing the power switches, several alternatives were considered. The use of paralleled devices would require that they all, turn on and off simultaneous ly. The required matching of turn-on, storage, and static operating characteristics is very difficult to achieve, thus making it desirable to avoid the use of paralleled devices. The use of Darlingtons in parallel-creates further problems, because the input stage must absorb most of the high energy associated with turnoff if the device is operated in a saturated mode. For these reasons, it was clear that the use of a single, large geometry device wa`s most desirable in" mechanizing the power switch. Three very different large-geometry devices were tested for use in this application. Of the three devices tested, two were found

IT

suitable for the EMA switching. However, the Westinghouse D60T type .transistor was selected„because its characteristics were slightly better than the other device for the EMA application.

5.2.2 r

BASE DRIVER POWER SUPPLY

The schematic diagram of the base driver power supply is given in Figure 5-9. The output of the circuit is a 250 kHz square wave (QDRIVE and QDRI E which is used to control the currents in the base driver circuit (described fin the next paragraph). The output is transformer-coupled through T1. The primary of T1 is center-tapped, and this point is connected to the 28 Vdc supply. In operation, the two ends of T1.±s primary are alternately driven toward ground by the power FETs.

Q1 through Q3 operate in parallel to drive one side of T1, while Q4

through Q6 drive the other side of T1, The FETs are excellent devices for this application, since they are easily driven by CMOS logic buffers, are very fast, : q and tend to act as a current si.nk., The hex buffer U1 ` drives the FETs, and the amount of drive which is provided is controlled by potentiometer R8. R8 thus controls the base drive for the"b60T transistors. Zener diodes CR7 and CR8 1

assure that the drain voltages on the FETs cannot exceed 75V. Diodes CR1O and `CR11 assure that the logic signals driving the hex buffer Ul do not exceed safe input limits for U1. The input control-signals

(QIN and W) are square waves

with'an exact 50% duty cycle established by counting down a higher frequency waveform. x

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5-10



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DELCO ELECTRONICS DIVISION s SANTA BARBARA OPERATIONS GENERAL MOTORS CORPORATION

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OELCO ELECTRONICS DIVISION • SANTA BARBARA OPERATIONS • GENERAL MOTORS CORPORATION 5.2.3

i

BASE DRIVER CIRCUIT

The schematic diagram of the base driver circuit is given in Figure 5-10. This circuit uses the QDRIVE and QDRIVE signals from the base driver power supply, and an RF drive signal for control. The RF drive signal is a 500 kHz waveform, synchronous with the 250 kHz QDRIVE „ waveform. When the RF drive signal is present, the base driver turns on the power transistor it controls. When the RF drive signal is absent, the base driver turns the power transistor off.

The QDRIVE waveforms are coupled into the circuit through transformers TI and T2. The rectified outputs of these transformers result in a nominal 4 V across capacitors C1 through C4, and 10 V across C5 and C6. When the RF drive signal is present, transistors,Q1 and Q4 are turned on. The turn-on of Q1 results-in Q2 And Q3 being turned on, thus placing a positive voltage on the base of the power transis Vis en torwhich. a istor being drive.,

RF d rive si by the circuit. WW hile thegnat

is

present, Q4 is on, and Q5 and Q6^'are off. When the RF drive signal is removed, \\

Q4 t urns u n„ of, off, .and Q 5

nu° 16 Qv are turn e d on. T (ii ^ CdU5e8 t h e gand

_. ter he "pow

case Ot

transistor to be (,about -10 V with respect to its base, thus turning it off.

The driver, provides excellent control of the power transistor. At turn-on, the 3

base-emitter voltage rises very quickly, and the base current rises rapidly. After turn-on, the - driver maintains a base current into the power transistor of about 15 A to assure that the,-power transistor remains conductive. At turn-off, the base is rapidly driven to -10 V, and the base charge is quickly removed to

}`

minimize turn -off time. Diodes CRl and CR2 provide the base drive current during the "on” state. Schottky rectifiers have been selected for this application to minimize circuit losses.

-5.3

POWER CONVERTER CONTROL

The power converter performs two major functions. It controls the magnitude

'

of the motor current, and (during motoring or plugging) allows current to flow in the correct pair of windings to provide proper torque for the load. The power converter control methods are discussed in the following paragraphs.

4 R79-2

5-12

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DELCO ELECTRONICS DIVISION SANTA, BARBARA OPERATIONS • GENERAL MOTORS CORPORATION

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DELCO ELECTRONICS DIVISION • SANTA BARBARA OPERATIONS *GENERAL MOTORS CORPORA'] 9O 5.3.1

CURRENT PROTECTION

In order to achieve adequate protection for the ten power circuit transistors in the event of a power converter control failure, currents are sensed in four locations. Chopper current is sensed by the IM current viewing resistor (CVR). The three negative phase currents, TAN, IBN; and ICN are sensed by CVRs in the emitter circuits of QAN, QBN, and QCN, respectively. There are separately adjustable positive and negative. ' 1imits for IM, corresponding to motoring/plugging and regenerating protection, respectively. IAN, IBN, and ICN share another adjustable pair of positive and negative limits.

If operative peak currents exceed any one of the limits, within approximately one microsecond the base drive to all transistors is inhibited and an indication of which limit was exceeded is given on the rear panel;of the QAP-QCN box or the QM-QB box. Protection limits, which may be checked on the rear panel of the a=;

appropriate box, are normally set at 100 amperes.

1

The only action taken when a current limit is exceeded is the inhibition of base

4

f

drive. Reset for resumption of normal operation mu^,t be accomplished manually by depressing the reset button located on either of the aforementioned boxes. It is not mandatory, but it is safer if this is done with the high voltage removed from the power circuit.

5.3.2

CHOPPER CONTROL

In controlling the QM1 and QM2 choppers for motoring or plugging and the QB1 and +

QB2 choppers for regenerating, comparators are used to determine whether the motor current is greater or less than the commanded value.

The motoring,

transistor comparator is in its high state if the motor current, IM, is less than the commanded value, IMC.

In equation form this is related by

QMC -,JIM/101 < (IMC/101 For plugging control the equation becomes QMC -r2'J IMX/10 < i IMC/101

JIMXJ is the absolute value of the greatest phase current as sensed by IAN, IBN, or ICN CVRs. Similarly, the braki ng transistor comparator described by

9

DELCO ELECTRONICS DIVISION • SANTA BARBARA OPERATIONS • GENERAL MOTORS CORP0RATi0N

QBC

IM/10I > IIMC/10^.

The two comparators used for chopper control employ adjustable hysteresis to .reduce chopper sensitivity to noise. The amount of hysteresis used controls the chopper operating frequency. The hysteresis being used corresponds to about 6 s r

amperes at IM. The peak operating frequency is under 10 kilohertz.

s! QMC and QBC toggle flip-flops each time they go from 0 to 1. The complementary output of each flip-flor,Q and Q are logically ANDed with QMC or QBC to form the logic drive signals for the four chopper transistors. s

In equation form these are related by

QM1 - Q 1 •QMC'

QM2 T. QMC QB1

Q2•QBC

QB

: Q -QBC

2



2

1

,,

k..

5.3.3

ROTOR POSITION SENSOR/TACHOMETER

An optical encoder which is connected directly to the EMA motor shaft is used for shaft position sensing for°commutation°control and for generating a shaft velocity signal. A description of the requirements_ for this device and a suitable ^r decoding mechanization for its use are given in the following sections. ^o o 5.33.1

ENCODER ENVIRONMENTAL REQUIREMENTS

The design goal is for the encoder to be ,capable of meeting the operating per-

y

formance requirements during and after exposure to any feasible combination of the following environmental conditions`:

Pressure

R79-2

2

Maximum: 15.23 Win (a) 10 Minimum: 10' Torr

5-15

DELCO ELECTRONICS DIVISION

Temperature ,

>

la

`

®

I

SANTA BARBARA OPERATIONS



GENERAL MOTORS CORPORATION

l 1

.Ambient: -40°F to +200°F

Humidity

Ambient. 0 to 100%

Vibration

Excitation acting along each of three orthogonal axes: +6d3/octave from " 20 to 60 Hz;

constant at 0.025g

>

Acceleration J

2

/Hz to 300 Hz;

+6dB/octave from 300 to 700 Hz; 2 constant at 0.15g /Hz to 2000.. Hz

Excitation acting along each of three°orthogonal,` axes;

It

4;

y

o

_t,Sg and - 5g for a minimum of 5 minutes

This environment is suitable for the use of hermetically sealed-components-and hermetically sealed CMOS or low power Schottky logic, silicon photo diodes, and „} light emitting diodes in ceramic and metal or glass and metal packages.,; An optical encoder constructed with these components in a sealed enclosure (where no condensation could take place ,) 'is certainly potentially capable of meeting environmetal needs. Other needs are a suitable output cgde and error-free

output with input shafts speeds up to 10,000 r/mina While it is clear that an _^. e

encoder can be designed to meet all needs, this phase of - the EMA development program used an optical encoder with much more restrictive environmental capability with respect to pressure, temperature, and humidity:

l

`

n

Pressure

Unspecified

Temperature

+32°F to +155°F

Humidity

Ambient: O to 98% (no condensation)

fi

5.3.3.2 ENCODER°ELEMICAL REQUIREMENTS When operating the four-channel EMA developed during the earlier phase, 'it was observed that motor phase current waveforms were strongly dependent upon comd mutation angle. It was concluded that good resolution of this angle would be

R79-2

5 - 16

'

^i

^

1

DELCO' ELECTRONICS DIVISION

s

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SANTA BARBARA OPERATIONS

• GENERAL MOTORS CORPORATION

highly desirable. Accordingly, one electrical degree (one-fourth of a mechanical degree) was set as a requirement. Furthermore, proper operation to 10,000 r/min, as confirmed by the manufacturer's testing, was set as another requirement->>

t

Since the decoded output of the encoder must have absolute shaft position infor-

mation some sort of indexing output was required of the encoder. In other respects the particular coding format was left open. 1

5.3.3.3

SELECTION ,- OF THE ENCODER,

In general optical encoders have the following four differeilt output formats, and combinations thereof;



Analog incremental,

III( Analog absolute,

r



Digital incremental,

a

Digital absolute.

Analog output types were felt to be undesirable because of restrictions in

capability and poor noise immunity. A digital absolute type is most attractive because it requires less decoding logic than does the digital incremental: It was found, however, that c

a major

development was necessary to build 4 d gital

absolute encoder with both the required resolution and top operating speed.

Thus `'the encoder selected.-was a digital incremental type with a single index bit. An industry standard type was procured, which provides quadrature squarewaves on two channels at 360 cycles per revolution and a single-index bit of /1,440 j

duty cycle per revolution,

a

5.x.3.4

DECODING TECHNIQUE

Since the type of digital encoder used is not an absolute type, shaft position at t

sys;tem

°-startup is unknown. Thus the motor, at start up,.i,s operated in a

step,pi ng mode ` until the i ndex,,is found. Whenever the 'index, Channel I, is a one, the absolute shaft position is known. For all--other shaft positions-, decoding is O'ccomplishedby counting transitions of the quadrature A and'B waveforms. o There are 1,440 counts per mechanical revolution.

}. ,

R79-2

5-17

0

4

t. i

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DELCO ELECTRONICS DIVISION

• SANTA BARBARA OPERATIONS • GENERAL MOTORS CORPORATION

A siTplified block diagram of the mechanization of the commutation decoding is given in Figure 5 ,=11.

A corresponding timing diagram is given in Figure 5-12.

The mechanization is based upon the u,se of up/down counters to provide shaft -

posi-tion information in between index, I, pulses. The commutation angle)fiay be adjusted from 1 to 58 degrees advance by means of a selection switbh'-on the front panel of the RPS decoder box.

By a somewhat similar mechanization, shaft position relative to the index, I, is decoded and then displayed with quadrant, sign, and angle information.

K

r

There is

also:digi`tal-to-analog conversion of this information so that shaft position is {

a`

indicated with a triangular wave having a scaling of 10 degrees mechanical per

"

volt in the format-shown in ' 'Figure 5-12.

This signal is available on the rear '

of the-RPS decoder box.

r

i

5.3.3.5

VELOCITY SIGNAL

A

signal

VPln^it^

, , derived from t h- opt i%ai

i s

frequency to voltage.

encoder b

,

^conv

erting its

Figure 5-13 is a diagram of this subsystem.

output

Pulses are

generated at both the positi=ve and negative going transitions of A and B phases of the encoder output.

Each phase has 360 cycles per revolution; thus the

maximum pulse frequency-is given by

f

max

o

_ 2x2x36Ox9 , 000 / 64 = 216,000 Hz

_

The frequency is divided by two to scale it for the full range of the F to V converters used.

Output is bidirectional and scaled for N/1;000 r/min.

This derivation of a ` velocity signal has been shown to work reasonably well"'in spite of its inherent output gran6larity(2 degrees, electrical) and ripple at low speed.

Use of higher frequency V to F converters and elimination of the

divide-by-two "stage would give a 50% reduction in granularity and ripple,

The EM1A is configured such that an alternate velocity signal may be obtained from an electromechanical tachometer simply by°removing the rate tachometer

R79-25-18 (

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DELCO ELECTRONICS DIVISION ^

• SANTA 13ARF9ARA OPERknONS„ • GENERAL MOTORS CORPORATION

^ r

N'MECH s,

OPTICAL ENCODER B A

i 1

^

I

}

PULSE GENERATOR

J^ i

a

tP HASE ECTOR

A?+Aj+B1+B

f1CCW o^ C U/

C

R

U/1)

R CCW UP/DOWN

I

COUNTER

COMMUTATION: ADVANCE SWITCH

0 59

01.58

A' Z -

T

C

R

DIGITAL COMPARATOR,

C

U/D

CW UP/DOWN

U/D

R CCW UP/DOWN

COUNTER

COUNTER

I

R

TCCW _.

(Torque Direction Command from Servo Box)

AND

AND

I 7

OR

F

i

DRIVE DECODER 1

2

3

4

Inhibit 5

6

1

(Overcurrent Protection from DAP • QCNI and QM•QB Boxes)

t

QAP

QAP

QBP

QBP

QCP'

QCP

QBN

QCN

QCN

DAN

(IAN

QBN

l

Figure 5-11. Derivati(y r of Commutation Decoding from the. Optical Encoder

R79-2

I

5-19



'

DELCO ELECTRONICS DIVISION

MOTORS • SANTA' 9ARBARA OPERATIONS GENERALCORPORATION

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DELCO ELECTRONICS DIVISION • SANTA BARBARA OPERATIONS • GENERAL. MOTORS CORPORATION F

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.x OPTICAL', EN,000ER A

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LP FILTER

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LP FILTER

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N/1,000

(Rate Signal to Servo Box)

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Figure 5-13.r Derivation of Velocity (Rate) Signal from the Optical Encoder

5-21

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GENERAL' MOTORS

C ORPOR ATION



dummy pl ug and i nser-ti ng the el ectromechani cal tachometer plug. With th i s operation a `scali ng network is connected to the electromechanical tachometer's output such that scaling is N/1,000 volts, just its is the rate tachometer scaling.

A digital readout of motor r/min is given oh'the front panel of the RPS decoder, J F

box.

This readout

i s derived from the encoder output frequency by means of ` a

simple 'Frequency counter. 5.3,4

'

MONITORING POINTS AND CONTROLS

The following four sections convey features of the four low level, black boxes. c

The ;boxes are considered with regard to their visual indicators, controls, input signals, and output signals.

5.3.4.1

THE RPS DECODER BOX

The RPS decoder box has



j

_

following front panel^ features:

Digital display of motor r/min (derived by digital count of the encoder output pulses).

4

a

Digital display of motor shaft position in electrical degrees.

``

0.

CCW and CW indicators -"indicate instantaneous directiow of shaft

rotation.

-J

M indicator - indicates a missing index pulse from the encoder, and As



extinguished when the motor has turned sufficiently far so that the-indexi,

is

found.,,.

• "Z-,I) I indicator - indicates the shaft is in the index posi tion. °



ID indicator - indicates the"shaft is in the index position or was less

than approximately one second ealrlIer. 7

a

Advance - thumbwheel switches adjust ,4ommutation timing and must be set between 01 and 58 (degrees, electrical); normally set at 20 (degrees,

f

electrical). Switch Drive indicators - on when base drive is available for the particular`

• `

transistors indicated (i.e.-QAP-QCN).

s, R79-2

5-22

}

T

Di:LCO ELECTRONICS DIVISION

°

• SAi'!TA BARBARA OPERATIONS • GENERAL MOTORS CORPORATION

The rear of the RPS decoder box contains the following four monitor points: •

Position — shaft position with a waveform format as indicated in Figure I

5-12. (•

r/min - analog output derived from the encoder with a scaling of-N/1,000 volts with positive being CCW rotation.

• lle /

J

4F - ,,pulses with a repetition rate of 4 times the channel A(or B) frequency, , 216,000 pulses/s at 9,000 r/min.

a

TRIG - a°trigger pulse derived.from°the encoder's index,.1 pulse/mechanical revolution., V

5.3.4.2

THE SERVO AMPLIFIER BOX

The front panel servo amplifier box has the,,following features':

°



Torque, CCW, and CW indicators -indicate direction of commanded torque.



mode', motor, plug and regenerate indicators - indicate commanded mode of operation.



`

Position potentiometer and switch used to provide a manually controlled position command, CCW with switch in CCW position or CW with switch in CW position.

Normally the pot is out of the circuit, with the switch in

the center (off) position (may be used for position offset). •

Velocity potentiometer and switch - used to provide a manually controlled

t

velocity command, CCW with the switch in the CCW position or CW with the switch in the CW position. `

Normally„the pot ?a out of the circuit, with

the switch in,the center (off) position (may be , used for velocity offset). •

Command In - the main position command input (scaling: 4 9 output per n volt command).

The rear of the servo amplifier box contains the following: ^_



Rate Limit adjustment - used to adjust the maximum rate-of-change of command current (min CCW is 25A/ms, max CW is 250A/ms),

'



Position Zero adjustment - used to adjust output deflection for zero.



Position Output - output position analog signal, 4 /volt, DE.

•I

Speed Output - output velocity analog signal, 1,000 r/min/volt, N (derived from the rate tachometer or the electromechanical tachometer).

5•-23

R79-2

4f,___

._'I

{ DELCO ELECTRONICS DIVISION

• SANTA BARBARA OPERATIONS a GENERAL MOTORS CORPORATION

1

i •

Tach Connector - used to connect an electromechanical tachometer or, with a dummy plug, to connect the rate tachometer derived from the optical

I

u

encoder;, 0

I

Torque Command Output - used to mod for the torque command which goes to the , QAP-QCN control box (scaling, IOA/volt).

5.3.4,3 .,

THE QM-QB CONTR O BOX

1,

The ( s

Drive Motor indicator - indicates when there is the availability of base drive to QM1 or QM2.

9

Drive Regenerate indicator - indicates when there is the`availabil 'ity of base drive to QB1 or QB2. Overcurrent indicators - MTR indicates overcurrent in the IM CVR in the motor direction; RGN indicates overcurrent in the IM CVR in the

1

regenerating direction; SE'S indicates a-protection shutdown caused by

v

overcurrent in the IM CVR or the AN, BN, or CN CVRs.

Overcurrent Reset button - may be used to reset an overcurrent shutdown

A

I

.

caused by excessive current in'either `direction in any of the four CVRs. Drive Sync output - +12V on the QM or QB connector indicates one of the QM transistors or one of the QB transistors, respectively, has base drive.

i

IM/10 output - signal derived from the IM CVR (scaled O,1V per ampere).



Limits/10 outputs - used to monitor the protection thresholds for chopper motoring current or regenerating current, IM/la or IR/10 (=-IM/10), respectively (scaled O.1V per ampere).

i



t

Torque Command input - connects to the torque command output signal from t the servo amplifier box.

5 ° 3..4.4

i.

THE gAP-QCN CONTROL BOX

The QAP-QCN control box has the following rear panel features;

a



Test X1 a n^ X2' indicators U available for internal connection for testi^^ but not used.



Overcurrent indicators - MTR indicates overcurrent in the AN, BN, or CN CVRs in the motoring.(or plugging) direction; RGN indicates overcurrent

{

R79-2

5-24

a

0

9 C"J

DELCO ELECTRONICS DIVISION S SANTA 13ARBARA OPERATIONS • GENERAL. MOTORS CORPORATION

in the same CVRs in the regenerating direction; SYS indicates a protection

shutdown caused by overcurrent its the IM CVR or the AN, BN, or CN CVRs. •

Overcurrent Reset button - may be used to reset an overcurrent shutdown caused by excessive current in either direction in any of the four CVRs..

a

IAN/10,,IBN/10, ICN/10 outputs - dgnals derived from the respective 1 CVRs (scaled 0. 1V per ampere).

e

Limits/10 outputs p p

- protection used threshold to monitor for IAN, IBN, the

or ICN currents in motoring/plugging or regenerating directions, IM/10 or IR/10, respectively (scaled 0.1 V per ampere). •

'Test X3 output - available for internal connection for a test output but normally connected for JIMX/101 (see paragraph 5.6.1.2) monitoring.

i

a

..

Q,

.

R79-2

5-25



^J

DELCO ELECTRONICS DIVISION

0 SANTA=, BARBARA OPERATIONS 6 GENERAL MOTORS CORPORATION C'

SECTION VI EMA OPERATING INSTRUCTIONS

6.1

SAFETY CONSIDERATIONS

All persons permitted to be in the`-,'vicinity of the EMA should be fully aware of the hazards associated with high power electronic and mechanical equipment. The voltages and currents,are large and potentially dangerous. The rotating elements n aree also potentially store large amounts of energy ever and g potent a ly hazardous.

b

All reasonablerecautions should be taken in setting9u p facilities for the EMA. ; p Persons not familiar with the equipment should be prevented from entering dangerous areas. Adequate grounding, fused circuits and high-voltage matting should'

be provided. The batteries which furnish the high voltage power should be adequately ventilated and protected from accidental shorts._ Cabling_ should be

j

protected, and necessary fencing or other constraints should be used to keep personnel away from dangerous voltages, rotating equipment, or batteries. Warning signs should be provided for all dangerous areas.- No one should work on this i equipment alone. Personnel who work on the equipment should be very familiar with r

the life-saving techniques (such as mouth-to-mouth resuscitation) which may be

required for electrical shock victims.

Battery servicing and maintenance (including fl-11ing and charging) should be

; F

accomplished by experienced personnel in accordance with the battery manufacturer's r

3

recommendations.

t7

Clear access to power switchgear, fire extinguishers and exits should be main u

tained at all times. Test equipment, work tables or other similar equipment should be placed in locations which do not interfere with equipment operation nor

'

;.

limit access to exits or safety-related equipment.

Whenever it is necessary for personnel to be close,,to the power electronics or motor stand, all input power to the EMA should be disconnected. In addition,

6-1

R79-2'• iRY

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iiRATI^III

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DELCO ELECTRONICS DIVISION

z

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• SANTA B ARBARA OPERATIONS • GENERAL MOTORS CORPORATION

the energy storage capacitors should be permitted to discharge. Bleed resistors automatically provide for capacitor discharge, but several minutes are required for the capacitor voltages to reach safe levels.

The 115 Vac power for the EMA should be of good commercial quality. The 28 Vdc supply must be capable of supplying at least 10 amperes, and the high voltage supply should provide 270 Vdc nominally. The 270 Vdc source should be current limited at 200 A (to prevent excessive inrush current to the energy storage, capacitors). The high voltage source should never be allowed to exceed 325 volts 0

under any conditions, since higher voltages could damage the power electronics. Appropriate voltage Timiting circuits must be provided on the battery charger so that it cannot supply excessive voltage under any condition (including inadvertent operation without the battery bank connected to the EMA).

Although operating the EMA is very simple, it must be recognized that large amounts of power and energy are involved, and it is therefore essential that all .,

personnel involved in EMA operations or maintenance use great care to make sure no unsafe conditions ever exist.

During tests, it is recommended that buffered

signals be used for display or recording purposes.

If direct access to other

signals is necessary, the operator should use great care to minimize the possibility of inadvertent shorts or disturbances that might cause excessive motor currents or other dangerous cond°itiof^s. J :'

p

°

As part of the EMA operations, all Auipment should be periodically examined for loose parts, adequate clearances, and other mechanical or electrical problems. Unusual noises or other indications of erratic operation should be investigated

a:

immediately.

6.2 '.

6.2.1

START-UP OPERATIONS

COOLING AIR'

Before startup-is initiated, cooling air for the EMA motor should be turned on if extensive tests at high power levels are planned.

6-2

-R79-2

r

Ov

-

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.:d

DELCO ELECTRONICS DIVISION SANTA BARBARA OPERATIONS • GEN_ER `L MOTORS CORPORATION

6.2.2

INPUT COMMAND SIGNAL

The EMA input command signal is introduced through a BNC connector located on the front panel of the servo electronics enclosure. The signal i ,s scaled to provide four degrees of EMA load motion for each volt of input command signal. The EMA load motion is nominally ± 40 degrees, hence the input, , comrriand voltage range is 10 V. However, input signals of ± 20 V will not cause any damage to the equip-

ment. volts.

Prior to

6.2.3

startup, it is

good practice to set the input command at zero

TURNON

1

i Turnon is accomplished by applying power in the proper sequence. }

The 115 Vac

power is first applied, thus allowing the logic and low level circuits °to become active.

The 28 Vdc supply is then turned on to provide power for the driver

elements.

Th y 270 Vdc power is applied last, at which time the system is fully

operational.

It is

permissible, with the system fully powered_, to adjust any

the potentiometers Located on the electronics enclosures.

of

The commutation

advance angle, which may be adjusted using the thumbwheel switches on the front panel of the RPS enclosure, must not be changed when the system is operating. Failure to heed this warning may result in motor power drive circuit damage.

L

k"5„

6.3

SHUTDOWN OPERATIONS

Shutdown is achieved in the following sequence:

0

Set input command to zero,



Turn off h.igh voltage power,



Turn off 28 Vdc power,



Turn off 115 Vac power,

al

Turn off, cooling air.

OEI

R79-2

6=3

i

DELCO ELECTRONICS DIVISION • SANTA BARBARA OPERATIONS • GENERAL MOTORS, CORPORATION v

SECTION VII TESTS AND TEST RESULTS

7.1

INTRODUCTION

^^

Several types of testa=were conducted on the EMA, but all tests could basically be, considered either motor performance tests or servo performance tests.

The fol-

lowing p^ragraphs summarize the results obtained during the system tests.

7.2

MOTOR PERFORMANCE TESTS

The motor performance tests were conducted on Delco's dynamometer stand (shown in Figures 4-4 through 4-7).

The dynamometer consists of a dc machine, its associa-

ted,field and armature controls, load resistance banks, torque and speed transducers, and the necessary instrumentation and controls to allow the dynamometer K

either to drive the EMA . motor (with the EMA -machine acting as a permanent-magne .generator) t `

i

t

or act as 'a- mechanical load for the EMA motor. ,

7.2.1

COMMUTATION ANGLE; CONTROL TESTS

As was indicated in Paragraph 5.1.2, the EMA control electronics allows the ' commutation an g gl e to be adjusted b y means of thu mb-wheel switches mounted on the

front panel of the rotor position sensor (RPS) electronics enclosure (see ` Figures 4-22 and 4-23 for photos = of this equipment).

Tests were conducted at

several power levels to determine the effects of the commutation angle on power current waveforms and system efficiency. the tests.

Table 7-1 summarizes the results of

For a given power level,, the commutation angle does not have a°major

effect on system efficiency.

However, the current waveforms , in the motor windings

are affected significantly by the commutation angle setting (see Figure 7-1 for typical motor phase current waveforms for various commutation advance angles). `

At low speeds no commutation angle advance is needed, but at high motor speeds

the commutation time becomes significant, and the motor "current waveforms are improved by providing commutation advance.

R79-2

7-1

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DELCO ELECTRONICS,, DIVISION

3

• S ANTA BARBARA OPERATIONS • GENERAL MOTORS CORPORATION

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7.2.2

FULL POWER MOTORING TESTS

Tests were performed to evaluate the system at full rated power (17 hp). 7-2"summarizes the results of these tests.

Table

The "efficiency" figures shown are

1

the ratio of mechanical output power to that provided by the high voltage supply (hence the low level electronics losses and cooling fan losses are not included in these data).

The full power tests show an "efficiency" of between 86 and

88%, with almost no change in efficiency when operating at either 20 0 or 280 commutation angle advance.

In conducting the full power motoring tests it was noted that the peak voltage

stresses on the inverter's anti-parallel diodes were approaching their ratings when operating at a supply voltage of 27G' Vdc. 'r

To assure adequate margins for

these devices, the supply was reduced to 240 Vdc for most of the subsequent system

tests.

If high power tests are to be conducted at supply voltages greater: than

270 Vdc, the anti-p^ral.lel diodes in the system should be replaced

i%r'ith

de vic es-

having reverse voltage ratings significantly greater than 400 V (the rating of the present units),

7.2.3

-

MOTOR TORQUE CHARACTERISTIC TESTS

The motor torque characteristic was°examined to see if the Wtput torque remained y

proportional to current for large currents.

7-3. -

These tests are summarized in Table

For torques well beyond the nominal design value of 120 in-lb, the m or's

torque coefficient remained about 1,.9 in^lb /A, independent of output t,^rque.

7.2.4

MOTORING TESTS

Motoring tests were conducted at torque levels of approximately 40, 80, and 1120 in-lbs,`using speeds of approximately 2,500, 5 1,000, and 7,500.r/min }

test results are summarized in Table 7-4.

The

The nominal supply voltage for these.

tests was 240 Vdc, and the commutation angle was set for 20 0 ,advance.

R79-2 ` 7-4

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Torque

Torque Control Current Coefficient

(A)

(ir:^lbs)

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7.2.5 REGENERATION TESTS

TA

Tests were also conducted with the EMA operating in the regenerative mode. In

=

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this` ase the c!ynamoma ter acted as a driving motor, and the EMA machine operated as a permanent magnet generator. Again, torque levels of approximately 40 and 80 in-lbs were used, but, with current commantds limited to slightly over 60A, the regenerative torque was limited to slightly over 100 in-lbs. Nominal speeds of

2,500, 5,000, and 7,500 r/min were used in these tests. The test results are shown in Table 7-5,

C

x

y

7.2.6

i

EMA TORQUE CONTROL, TESTS

Torque control tests w&e conducted on the EMA at several current-levels. In these tests a. constant current command was applied, and torque measurements were made as the system gent through its motoring, plugging, and regenerative

modes. The test data from these - , runs are presented" in Table 7-6.

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MOTORS CORPORATION CELCO ELECTRONICS DIVISION • SANTA BARBARA OPERATIONS GENERAL •

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Current Command (A)

21.5

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Motor Torque (in-lb)

Motor Sreed (r/min

40 39.8 39.8 81.9 1Q1 62 33 28 29 48.5

1,000 750 500 260 336 200 100 60 0 100

73.3 73.6 74.3 99.1 82 65 47 87 86 86

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Control Mode REGENERATING

PLUGGING

.MOTORING REGENERATING

PLUGGING

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DELCO ELECTRONICS DIVISION • SANTA BARBARA OPERATIONS *GENERAL MOTORS CORPORATION

7.2.7

MOTOR SPEED ANOMALY

During the motor tests it was found that the motor could not be driven at speeds greater than about 8,300 r/min. At very light loads the maximum obtainable speed was slightly lower (7,800 - 8,000 r/min). At the present time, the reason for the speed limitation ' is not `''clear. It may be caused either by some limitation of the electronics or by a combination of the motor and electronics, but time restrictions have prevented any extensive investigation

7.3

of

this anomaly,

SERVO PERFORMANCE TESTS

The servo performance tests were conducted with the EMA disconnected from the dynamometer. The gearbox was attached to the motor assembly (as shown in Figures 4-15 and 4-16.) ,J 7.3.1

"FREQUENCY RESPONSE TESTS

Frequency response tests were conducted using an EMn 1410 Frequency Response Analyzer and an HP 740W-Recorder. The velocity and torque limits of the machine

j,

limit the amplitude of the motion (see pages 6-15 through 6-19 of Delco Report R78-1 for an analysis of these effects). For an"ideal system with a torque limit of 120 in-lbs, a velocity limit of 9,000 r/min, an inertia of 0.006 in-lb-s 2 , and .

a gear ratio of 2,700:1, the amplitude of the output which producesvelocity limiting is given

by

A V - 3.18/f

(deg)

where f is the frequency of the motion in Hz. Similarly, the torque (or acceleration) l i milt results in an ampl i.tude limit

of

A - 10.75/ }f 2 (deg) A

>

At low frequencies,

velocity ,,;limiting dominates,

and at 'higher frequencies (ideal-

ly, above 3.4 Hz) acceleration limiting restricts.the output motion. In the actual hardware, backlash, time lags and other effects limit the output motion g

still further.

R79-2

7-11

b. 1

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DELCO ELECTRONICS DIVISION • SANTA BARBARA OPERATIONS

GENERAL MOTORS CORPORATION



Because of these nonlinear effects, when frequency response measurements are made it is desirable to limit the output travel to amplitudes that enable the EMA to operate in a reasonably linear manner.

In the frequency response tests conducted,

the input command was varied as a function of the frequency being used, and the readings of amplitude and phase for both the input and output were recorded.

Frequency response data were , obtained for several system( gains and with several -

different time constants for the dominant system lag (the filter for the position For this run,

A typical frequency response is shown in Figure 7-2.

error signal). ,

FREQUENCY (Hz) A

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FREQUENCY

I^jII!

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Figure 7-2.

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PositionGain, 6100 A/dg Velocity Gain: 0.22A/r/ min Time Constant: 0.01 second

50

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RESPONSE

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Typical Frequency Response Measurements

the position gain was set at 6,100 A/degree-of position error, and the velocity gain was 0.22 A/r/min (with speed referenced to the motor sh4ft)'.

The time

constant for the position error break was set at 0.01 second (which would provide a first order lag at 15.9 Hz), and the current command rate 'limiter, was adjusted ,

.to provide the slowest available current command rate.

For frequencies below

4.0 Hz, the gain and phase measurements were made using the position command

r

7-12

R79-2 wa

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-

-...

DELCO ELECTRONICS DIVISION • SANTA [BARBARA OPERATIONS *GENERAL MOTORS CORPORATION input and the measured output .response.

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At frequencies above 4.0 Hz, the tacho-

meter output signal was used to , measure the system output, because the position output motion is restricted to very small amplitudes if the velocity and torque "

limits of the EMA are to be avoided.

a'

The frequency response shown in Figure 7-2

is well within the design goal boundaries (which are also shown on the figure). By adjusting the system parameters, the ` frequency response characteristics of the

o

EMA can be adjusted over-rather wide limits.

Tables 7-7 (a) through (f) show

typical frequency response data obtained during sytem tests.

As can be seen from

these runs, the gain and phase ., characteristics of the system can be adjusted over a considerable range, and can be made to remain well within the design goal limits.

As a matter of interest, frequency response measurements were also taken-with the

^a

position loop open - in order to determine the gain and phase characteristics of the tachometer loop.

The dominant characteristic of the°tachometer loop is a

well-damped, second-order response°(for normal gain adjustments) with a damped natural frequency of approximatelyHz. „ 65

The tachometer loop is very stable,

and either the output=of the . mpchanical tachometer or the signal from the rotor position sensor (RP§Y, may be used for velocity feedback purposes.; The use of the RPS velocity signal results in a small-amplitude (less than ± 5 degree) l'imitcycle motion at the motor shaft (this would correspond to about ± 0.0014 degree

o -

of output motion with an ideal gear train having a 3600:1 ratio).

In most

applications, system backlash and other nonlinearities would undoubtedly mask \1

this 'limit cycle^6completely. _

In systems using redundant actuators, it may be

possible toa bias the system in such a manner that each'motor_,would operate at a small percentage of its rated speed, , with :no net output motion, thus providing a continuous rate signal from the RPS even though the EMA output is stationary. If this is done; the limit cycle should be eliminated.

rr .,.

R79=2

7-13

1. o.

DELCO ELECTRONICS DIVISION • SANTA BARBARA OPERATIONS • GENERAL MOTORS CORPORATION i System Gains and

Time Constants: 6100 A/deg 0.22 A/r/min 0.01 second Slowest

Position Gain: Velocity Gain: Time Constant: Current Command Rate Limit

a

i

{

I J 0 "

*Phase lag at frequencies greater than 3

Hz may be any value

Table 7-7 (a). Data From Frequency Response 'rests System Gains and Time Constants; 6100 A/deg 0.22 A/r/min = 0.01 second Fastest

Position Gain: Velocity Gain: Time Constant: Current Command Rate Limit:

i

De sign Goa l

Measured Frequency

Gain

(Hz)

(dB(deg)- -

0.15

0.65

-1.7

Phase Lag

Gain

Phase Max

Min dB

Max

+1.0

-1.0

-4.0

1.00

0.40

-9.2

+1.0

-1.0

-20.0

2.00

1.58

-32.1

+&0

-58.0

3.00 4.00

2.37 1.40

-68.6 -100.6

+3.0 3-0

1-3.;0 -3.0 -3.0

-80.0

j s h

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DELCO ELECTRONICS DIVISION



i

SANTA BARBARA OPERATIONS • GENERAL MOTORSCORPORATION e

System Gains and Time Constants: ,- p,

:Position Gain .

6100 A/deg

Velocity Gain:

0.22 A/r/min

Time Constant:

0.00 second

-

Fastest,'z

Current Command RateLimits: Ilk,

Design Goal

Measured

Frequency (Hz),

0

^.

Gain

Phase

( d B) _

(de g )

Gain - Al -(dB)

(d6^

Phase Lag (deg) Y

0.15

0.07

-1.7

+1.)

1.00

0.24

-9.2

+1Ir 0

-1.0

-20.0

2.00

1.17c'

-32.1

+3.0

-3.0

-58.0

3.00

0.67

-73.0

+3.0

-3.0

-80.0

4.00

L-3.21

_. -111.5 +

__

-1 1 0

-4.0

=3 D

* Phase lag at frequencies greater than 3 Hz may be any Table 7-7 (c):

ua

value

from Frequency Response Tests

System Gains and Time Constants:

'"..

Position Gain: Velocity Gain:

6-100-',A/deg 0.11 A/r/min

`me Constant:

0.00 second

Current Command Rate Limits:

V

Fastest

,u Design Goal

Measured Frequency

Ga' Min

Phase

Lag

Gain

Phase

(Hz)

(dB)

(deg)

0.15

0.02

-1.1

+1.0.

-1.0

-4.0

1.00

0.16

-4.1

+1.0

-1.0

-20.0

2.00

0.98

-14.9

+3.0

-3.0_

-58.0

3.00

1'.91

-27.6

+3.0 `}

-3,,0

-80.0-

3.2

-37.9 1 +3.0

.4.00

Max

en {GB) ,

(deg)

1. -360„

Table 7--7 (d). Data from Frequency Response Tests-,

R7.9-2

7 -15

,,'

OELCO ELECTRONICS DIVISION • SANTA BARBARA OPERATIONS' S GENERAL MOTORS CORPORATION

Stem Gains and Time Constants " Position Gain: Time Constant:

6100 A/deg 0.17 A/r/min

_

Velocity Gain:

0.00 second

-

Current Command Rate Limit;

j

Fast6st

Design Goal

Measured

I 'n i in ^

Phase Lay _' Max

(dB)

(deg)

Gain

Phase

(Hz)

(dB)

(deg)

--M-ax (dB) .

0.15

0.02

-1.6

+1.0

-1`: 0 .

-4.0

1.n0

0.24

-7.5

+1.0

-1.0

-20.0

°2.00

1.17

> -23.8

+3.0

-3.0

-58.0

3.00

1.39

-53.3

+3,0

-3.0

-80.0

4.00

0.93

-72.3

+3.0f

-3.0

Frequency

u

Table-7-7 (e).

Ai

Data from Frequency Response Tests

System Gains and Time Constants:Position Gain: Velocity Gain: Time Constant: Current Command Rate Li.mi.t:

12,000 A/deg 0.27 A/r/min 0.00 second Fastest

Design Goal

Measured Gain

Frequency

= =_

Gaiv

Phase

(dB)

­ Max (deg)

a

(dB)

(deg)

Max (dB)

0.15

0.05

-1.6

+1.0

-1.0

-4.0

1.00

0.20

-5.7

+1.0

-1.0

-20.0

2.00

1.05

-18.3

+3.0 l -3.0

-58.0

3.00

1.50

-40.0

+3.0

-3.0

-80.0

2.46

-45.1

+3.0 1

-3.0

(Hz) (^1)

4.00

1

DELCO ELECTRONICS DIVISION • SANTA BARBARA OPERA TIONS • GENERAL MOTORS CORPORATION I

7.3.2

STEP RESPONSE_ TESTS

The EMA was tested to determine its std response characteristics.

The design

goals for the EMA step response envelopes are shown in Figure 7-3.

The two most

p

i.

140 is

120

NOTE; COMMAND AMPLITUDE = 2 to 6% FULL STROKE

TYPICAL

100

fc

r

i

FINAL STEADY STATE POSITION ---"

SF

c

' r

88

POINTS OF INTEREST TIME

y o° Q60 °

0 0.025 0,075 0.150 0,250

40

ENGINE DEFLECTION (PERCENT) UPPER CURVE LOWER CU R'.E 0 0 80 0 125 40 125 85 125 85

0.300

"

120 See Note

0.500

4

85= '.

NOTE: Limit cycling shell not exceed 3.0 percent of rated stroke peak to peak during a 10 second period. Hunting or drifting during a one minute $erlod shell not exceed the threshold requirements,

20

( I

00

0

0,1 j

0,2

0.3

0.5 0.4 TIME (seconds)

#

8,6

0.7

018

,

..

I f"

:.1

a

0.0

t

Figure 7-3..

Position Transient Response Design

Goal

/

r'

critical parameters are peak overshoot (the design goal is 25%) and time to reach 85% of steady-state travel

(0.150 seconds is the design goal).

The scaling

for the original design was based upon a , gear ratio of 2885.5;1, and command amplitudes between 1.1 degrees and 2.75 degrees were to meet the design goal (these values repreOwnt 2% and 5% respectively of the 55 0

which is +40

to -15°).

0

full stroke motion,

Wi ,jrh the 3,600:1 gear ratio of the,instrumentation^•^

gearbox, the corresponding ,;{travel is given by;

Y

/ ry

,.

-

7-17

R79-2

z. •

^".

_

fir%-^^.-

i t

DELCO ELECTRONICS DIVISION* SANTA 6ARUARA OPERATIONS •

GENERAL MOTORS

Output

Output Motion for,'-'2,685. I

Output .Motion for 3,600:1

Travel

gearbox

gearbox

2%_

1.10 deg

0.8206 deg

0%

1.65

1.231

4%

2.20

1.641

5%

2.75

2.051

:y

CORPORATION

3r

}

The overshoot which is measured in response to a step command is a function '

of

the

system gains and adjustment parameters.;, Figures 7-4 through 7-7 show typical measuroments "of ~the BMA's response to 2, 3, 4, and,5% commands. The overshoot requirements can be met very easily.

For example, with a position gain (K P ) of

6,100 A/deg, a velocity gain (K v ) of 0.17 A/r/min, a . time constant (r) of 0.00 second, and with the current command rate limiter set for its fastest response (see Figure 7-4), the overshoot in response to a step command was found. to be:

Step Command

Measured

J

Overshoot

2%

o

a 14 %

3%

7%

4%

5/ 3a/,o

5% o

By`appropriate adjustment, the system step response can be varied from rather lightly damped (see Fi.gure 7-7) to highly damped (see Figure 7-6). J! The time required

for

the system to reach 85% of its steady- , state output motion

is determined.,primarily by the acceleration and velocity limits of system. In addition, backlash,.mechanical windup, and other

effects

add to the response

,time (See Paragraph 7.3.6 for additional discussion of these effects).

F

typical gains, the response times to 170 milliseconds for a 5% step

7

vary

from about

Fo'r

90 milliseconds for a 2% step

(see Figure 7-8).

7-18

R79-2

s

DELCO ELECTRONICS DIVISION • SANTA BARBARA OPERATIONS • GENERAL MOTORS CORPORATION

-•., I

1

INPUT COMMAND (degrees)

0

1

OUTPUT MOTION (degrees)

-

0

1

"1

4t---

--

- _ _

_ -_ __

-_

-

44-

= -

1 = -=t

12,500

MOTOR SPEED (r/min)

0

:t=-_ -12,500

125

MOTOR CURRENT (A)

0

-125 9280.0293

PRINTED IN U S A

Figure 7-4 (a). Step Response to 2% Command (K p = 6,100 A/deg, K v = 0.17 A/r/min, T = 0.00 second) R79-2

7-19

OELCO ELECTRONICS DIVISION • SANTA OARSANA OPERATIONS • GENERAL MOTOPS CORPORATION

1

INPUT COMMAND (degrees)

0

-1

1

OUTPUT MOTION (degrees)

- '

0

-

--

TrT

-1 ^

12,500

MOTOR SPEED (r/min)

I —f

0

-1.2,600 125

t

MOTOR CURRENT (A)

0

-125

Im ow

maw [email protected] mini

MOWN

9280-0293

PRti

Figure 7-4 (b). Step Response to 3% Command (Kp = 6,100 A/deg, K v = 0.17 A/r/min, -r = 0.00 second) R79-2

7-20

DELCO ELECTRONICS DIVISION • SANTA BARBARA OPERATIONS • GENERAL MOTORS ZORPORATiON

2

INPUT COMMAND (degrees)

-

0

-2

-

_

_

L

2

OUTPUT MOTION (degrees)

-

-N

0 -

_

_

_ 1

12,500

MOTO r;

0

SPEED

(r/min)

Y

12,500 , I . ^^^ I ^ ^^^^,^^I^^^,I^,,,I,^^^I^^^^ ^^^^I^^^^I^„^I ^^^ I „^, ^,^^I^^^^I^^^^I,^„I^^„

^,,,I,^,^I^^^^I^^^^I^^^^• ,., I „

. I „

125

MOTOR CURRENT -

M-T

-125

92800293

PRINTED IN

Figure 7-4 (c). Step Response to 4% Command

(K P + 6100) A/deg, K

= 0.17 A/r/min, r = 0.00 second)

R79-2

.i ''

7-21

DELCO ELECTRONICS DIVISION • SANTA BARBARA OPERATIONS • GENERAL MOTORS CORPORATION

2

0 INPUT

COMMAND (degrees) -2 'I

!'

I

^

i

i

'I,

I .

^^,

^^

i ^

. I .

,^ i „ „ I• „^

^

i „ .. I .

^ I ,

.

I . ^^

.. I ,

.

I . ,^ I ,

, I ^^^

i

2a-

OUTPUT MOTION (degrees)

0

-2

12,500

I MOTOR SPEED (r/min)

9F

4-12,500 .. i „

. i

,,, „ I , I ..„ I „ I

,,,I„

I

^... i .... I ..., I ,^^ I

I „ I

„i. .

125

,&J

own

Ni_^ JT_

f_1 __ -

_. - -

im

se to 5% Command lin, r = 0.00 second) i-22

Am

f DELCO ELECTRONIC* DIVISION • SANTA BARBARA OPERATIONS • GENERAL MOTORS CORPORATION r7l 1

INPUT COMMAND

i

-

T17

-

-

I

(degrees)

I

1_4

-1 1

1 a 3

[7

-._

-



-

-

0 OUTPUT MOTION (degrees) -1

12,500

1 0

J

MOTOR SPEED (r/min)

-M4 -12,500

125

f MOTO R CURRENT

1

0

A)

i _t:X

-

- -

-125

Figure 7-5 (a). Step Response to 2% Command

^I

(K p = 12,000 A/deg, K R79-2

= 0.27 A/r/min, 7'0.00

second) 7-23

DELCO ELECTRONICS DIVISION • SANTA "ARBARA OPERATIONS • GENERAL MOTORS CORPORATION

^7777T--- -

1 }

-

#.

0- --^

INPUT

COMMW_

(degrees)

1

-

1

-

- - --



- - -

OUTPUT MOTION (degrees)

0

-

-

12,500

MOTOR SPEED

0

-

-12,500. 125-

MOTOR

0

CUR` ENT - 125 "ARe

Figure 7-5 (b). Step Response to 3% Coninand

(Kp = 12,000 A/deg, K v -- 0.27 A/r/min, 'r = 0.00 second) R79-2

7-24

Ij

wry ^^

DELCO ELECTRONICS DIVISION • SANTA BARBARA OPERATIONS + GENERAL MOTORS CORPORATION

i 2

^_

O

INPUT COMMAND (degrees)

-ffi I -2

2

OUTPUT MOTION (degrees) _I

-2

12,500-

0 MOTOR SPEED (r/min) -12,500-

125

i le 9280-0293

PRINTED IN U S A

;ep Response to 4% Command ).27 A/r/min, T = 0.00 second) 7-25

'

DELCO ELECTRONICS DIVISION • SANTA !BARBARA OPKRATIONS • GENERAL MOTORS CORrORATiON

2

s

0 INPUT COMMAND (degrees)

Tl

-2 i

.:7T-

2

--.m =. 0 OUTPUT MOTION (degrees)

. ..

. -

-2 W

I.I.P.1.11-1...

I

I I

12,500

MOTOR i

0

SPEED (r/min)

-12,500

125-

i

i

r

MOTOR CURRENT (A)

0

77

-125 r

Figure 7-5 (d). Step Response to 5% Command (K p = 12,500 A/deg, K V = 0.27 A/r/min, T = 0.00 second) 7-26

I

DELCO ELECTRONICS DIVISION • SANTA BARBARA OPERATIONS • GLNERAL MOTORS CORPORATION

-

r

-^ r Yr«

rl

Z

^I

0 INPUT

COMMAND (degrees)

i

-1

1

i 0

OUTPUT MOTION

(degrees) -1

t

12,500

t MOTOR SPEED

i

0

(r/min)

i

-12,500

125

MOTOR CURRENT

0

(A)

1 -125

t

Figure 7-6 (a). Step Response to 2% Command

t

^i

HFA

(K p = 6,100 A/deg, K v = 0.22 A/r/min, T = 0.00 second)

R79-2

1-27

DELCO ELECTRONICS DIVISION • SANTA BARBARA OPERATIONS • GENERAL MOTORS CORPORATION 1

T-

1

L

0 INPUT COMMAND (degrees) -1

71

1 OUTPUT MOTION (degrees)

0

-

-1

12,500

_

0 MOTOR SPEED (r/min) - 12,500

125

MOTOR CURRENT (A)

0

-125

Figure 7-6 (b). Step Response to 3% Commar (K p = 6,100 A/deg, K v = 0.22 A/r/min, 'r = 0. 00 sE R79-2 I



!

GELCO ELECTRONICS DIVISION • SANTA BARBARA OPERATIONS • GENERAL MOTORS CORPORATION I

2 .

F

1

^—_

1

0-

INPUT COMMAND (degrees) -2 .I

I

I

I

I

I

I

I

„.I ... 1 ^,

I

I ., I

^

I .

^ ... I .

I „•. I „ .^

2

OUTPUT MOTION (degrees)

0 I

sG

-2 I

—_

12,500

I

I

I

I ,

,I

I ,



I ,

.,

I , — . _ I , I .

I

. ^^

I

^^^

^„1^-

_

1 1

MOTOR SPEED (r/min)

U

-12,500-

'

125

MOTOR :URRENT

0-

(A)



1 2 5 -

NFWI F FT PACKARD

Figure 7-6 (c).

'

Step Response to 4% Command

(Kp = 6,100 A/deg, K v = 0.22 A/r/min. T = 0.00 second) R79 -2 7-29

L



— ^,-

- - fffi!S

- - --

----

-AJL-

'

DELCO ELECTRONICS DIVISION • SANTA SARSARA OPERATIONS • GENERAL MOTORS CORPORATION

I '

2

0 INPUT COMMAND

(degrees)

--

2 OUTPUT MOTION (degrees) D-

1

-2-

_ =--_

_-_-

-_

12,500-

0 MOTOR SPEED

(r/min) -12,50G125-

MOTOR

0-

CURRENT (A)

125

HEWLETT -PACKARD

Figure 7-6 (d). Step Response to 5% Command = 0.00 second) (Kp= 6, 1 00 A /deg, KV = 0.22 A/r/min,

` R79- 2

7-30

n

i

DQLCO EL[CTROR"CS DIVISION

i

V

SANTA BARBARA OP[RATIONS • GENKRAL MOTORS CORPORATION

1

- _-

i 0

INPUT COMMAND (degrees)

i

-1

t

_-

1

__

_

____

11T

i OUTPUT MOTION (degrees)

0 _

-_ -

i -112,500

i MOTOR

0

SPEED

t

(r/min) --

t

-

-

j

_

-12,500 .^

i 1

I'll.

ml

1 i 11,1111,111, 1111111.1

^^i,1^ • 1,^1^^,1r11,i111

^„ 1,1^^^,^1^1,11•I,i ^^^

1^11,1^1 i,^^^i, 1111,1111

^.i,,.

125

MOTOR CURRENT (A)

0

-115-

' 1

) IN USA

Figure 7-7 (a). Step Response to 2% Command !Kp 6,100 A/deg, K V 0.22 A/r/min, r= 0.00 second)

i ^, f

-

=

R79-2

=

-

7- 31

DELCO ELECTRONICS DIVISION • SANTA 19ARSA

'T----r--1--T7-

i

^r-T

1

0 INPUT

COMMAND (degrees) -1

1

0 OUTPUT MOTION

(degrees) -1

12,500

MOTOR SPEED (r/min)

0

-12,500 125

MOTOR CURRENT (A)

0

I

-a

-125

-

_

Jt

LA HEWI

Figure 7-7 (b). Step Response to 3% Command (K p = 6,100 A/deg, K v = 0.22 A/r/min, T = 0.00 second) R79-2

7-32



DELCO ELECTRONICS DIVISION • SANTA SARSARA OPERATIONS 09HERAL MOTORS CORPOPATION

1 '

2

'

0 INPUT COMMAND

(degrees)

1

=

=

_- ILL;

2

'

OUTPUT

0

MOTION

(degrees) -2 12,500

MOTOR

1

SPEED

!

(r/min)

0

-12,500 125 i MOTOR

-

0

CURRENT (A)

i

125 -

l

ACKARD

Figure 7-7 (c). Step Response to 4% Command (Kp = 6,100 A/deg. K v = 0.22 A/r /min, T = 0.00 second) R79-2

7-33

ATION

47f

:

-_

0 INPUT

_

COMMAND

-

-

^-

(degrees) --

-2

i

2

_

OUTPUT MOTION (degrees)

I .... I .

.

I ... W

.

T

1

. 1

I

1

1

,

1 „ , 1

11. „

V .

,I

12,500

MOTOR SPEED

0

-12,500



125

MOTOR CURRENT

6"r

0 -

f

(A)

i

-t at--t HEWLETT-PACKARO

Figure 7-7 (d).

Step Response to 5% Command

(K p = 6,100 A/deg, K 0.17 A/r/min, T = 0.00 second) R79-2 P

C

_ ^

7-34

DELCO ELECTRONICS DIVISION s SANTA BARBARA OPERATIONS • GENERAL MOTORS CORPORATION

r

200

woo

o

Or

®'

3t

`

O E ^. W_ Vi`^

!

Z V

A

t

^

^ O.

E

OLU^loe Cr

0 LU

Q

W

I

I

I

4 STEP COMMAND'AMPLITUDE (pe3 rceni^ of Full Travel

,5

o U

.J^



_'

a

°

Figure 7-8.

1

Response Time of EMA as a Function of Step Command

Si ze

From the.figure it can be seen that for step command magnitudes less than 3.8% of {

full travel, the system reaches 85% of its steady-state output_-_-otion in 150

milliseconds., To meet the design goal for response time of 150 niti °l 1 i seconds; for a 5% step, the output gear ratio for the EMA would have to be reduced approximately

(5.0-3.8)/5.0 = 24% T

7.3.3

LINEARITY TESTS_

The purpose of this test was to show that thexlnear displacement of the EMA,;^ defined as the relationship between the input position,,command signal and the output position as measured byrthe output position transducer, is linear within <<

+ 1% of full travel.

e

7-35

_R79-2

#

,,

4

v^

t

.. -....

...

_......—.^..."s.*'^r.-e^..^s.--.; .yam-ac.wr.lw.• i

DELCO

ELECTi^^NICS = DIVISION • SANTA BARBARA OPERATIONS + GENERAL MOTORS CORPORATION

The Frequency Response Analyzer was used in this test to provide an input command. WN

The EMA output shaft was rotated in one- degree increments from null to full travel in „ one direction.

At each position, the input command voltage and the EMA

position transducer output were measured using digital voltmeters.

The-measure-

ments were also repeated for commands in the opposite direction.

As a simple method of demonstrating the linearity of the system, a straight line was placed through;-the data points' taken at

+

39 degrees,'arld the deviations of

; The data from The maximum deviation was . Mound to"be

all other data points from th ,,-straight line were calculated-

these tests are summarize` "d in 1 'le 7. 8.

0.010 Va since the scaling is 4 degrees per volt, this would correspond to a n

_

deviation of 0.040 degree.

In terms of 5^5 degrees of full travel,

t,

Lfhe.largest

deviation was

(0.010)(4)(100)/55 = 0.073%

The standard deviation, was found to bet

r

(0.00254)(4)(100)/55 _ 0.018%

^".The mean deviation .,for these data-was,

-(0.00243)(4)(100)/55 = 0.018%

and the root mean square deviation was e r

L

„(0.00350)(4)(100)/55 = 0.025%

From the test measurements it was found that the linearity:of the EMA was well within the design goad" of 1%. t

j r

r

^^

1

R79-2 ^T

7-36 ^^

U

1.

1

DELCO ELECTRONICS DIVISION • SANTA BARBARA OPERATIONS • GENERAL MOTORS CORPORATION n

Commanded Deflection (volts) (4 deg/V)

r.

0.000 -0.=250 -0.500 -0.750

° ,

-0.994

-X1..250 -1.501 -1.750 -2:002 -2.250 -2.500 -2.750 -3.004 -3.255 -3.500 -3.753 -4.005

>

3

"X

-4.248

-4.501

-4.754 +'10.004

` =

llii

r :;

r

9.748° 9.501 9.244 9.005 8.756 8..506 8.242 `8.003 7.753 7.500 7.248 6.996 6.752 6.502 6.252 6.002 5.748 5.501 5,.252 4.995 4.747 4.494°

Measured Deflection (Vol ts) (4 deg/V)

Calculated

-0.,004 -0.'258 -0.506 -0.759 -1.003 -1., 157 -1.510 -1.765 -2.017 :-2.265 -2.514 -2.770 -w2.02' -3.275 -3.519 -3.776 -4.030 -4.278 4.533 -4.787 +10.060 9.806 9.558 9.`304 9.058 8.803 8.556 ,. 8.294 8.050 7.796 7.543 7.290 7.036 6.790 6.539 6.287 6.036 5.780 5.532 5.282 5.022 4.773 4.519

.004 .0,06 .0"02 .n04 .0103 -.001 -.001 .004 .002

Commanded--

Deviation

Deflecti4'n

from Straight Line (volt )

.001

-.002 .003.004 .000 -.003 .000 .000 .004 ` .004 .004 _ 0.004 0.000 0.000 -.005 0.001 0.005 0.001 -:003 0.001 0.003 0.002 .001 0.001 0.002 0.1002 0.002 0.002 0.002 0.002 0.001 0.002 0.002 .001

(volts) (4,,deg/V)

-500 -5.244 -5.'502 -5.746 -6.x 006 -6.24q -6.504 -6.746 -7.003 -7.247 -7.504 -7.745 -8.002 -8.250 -8.503 -8.752 -9.004 -9.242< -9.498 -9A.748 -9.952 4.248 4.000 3.751 3.501 3.252 3.004 2.752 2.500 2.250 2.003 1.746 1.500 1.256 1.002 0.747 0.497 0.258 0.002

Measured

Deflections (volts) (4 deg/V)

Calculated Deviation from Straight

Line (volts)

-5.035 -5.278 -5.540

.004 .002 .004

-5.780

-.001

-6,045 -6.287 -6.552 -6.791 -7.045 -7.399 -7.553 -7.797 -8.060 -8.306 -8.553 -8.810 -9.059 -9.308 -9.558 -9.807 _- 10.017 4.271' 4.022 3.770 3.519 3.269 3;,019 ? 2.766 2.512 2.260 2.012 1.753 1,.505 1.260 1.004 0.748 0.497 0.255 -0.002

} j

;.

.002.. .005 .008 -.004 -.001 .008 .003

,005

.009

.006 =.-002 005 .000 .010 .003 .000 .005 -0.002 0.002 0.003 0.003 0.002 0.003 0.002 0.003 0.003 0.003 0.003 0.004 0.003 0.004 0.003 0,-:^002 0.004 0.004

3,.

-`

>

;'

n

Table 7-8.

Data from Linearity Tests

0

R79 -2

-

7-37 1`



DELCO ELECTRONICS DIVISION;, • SANTA BARBARA OPERATIONS "*GENERAL MOTORS CORPORATION

°7.3.4

HYSTERESIS fESTS

The purpose of this test was to demonstrate that the hysteresis of the EMA,;defined as the maximum difference between;;output positions obtained when traveling clockwise then counterclockwise in response to 0.01 Hz sinusoidal input, does not exceed 0.05% of full travel.

The 'input signal for this test was provided by the Frequency Response Analyzer. -

The input and output signals were filtered using single-lag, low-pass filters with

y

break frequencieso f ap app pro roximately 0 1 Hz x

T he

fil te red in i pu ut si s i gnal na and the

filtered output signal were recorded using a Nico1et digital storage oscilloscope, Model 206. Figure 7-9 shows the output plotted against the input with a peak-to-

J

peak output, amplitude of 0.64 degree (at an input frequency of 0.01 Hz). On this scale, no hysteresis can be' noted. Figure 7-9 also shows a segment of the saif^e display expanded by a factor of 16. On this scale some separation can be seen. The equivalent hysteresis was found to be 400 microvolts out of 160 millivolts peak-to7peak. _

The angular equ iv a

lent is

(0.4)(0.64 degree)/160 = 0.002 degree

'4

in terms of full travel) the ( 55 degrees) g

ysteresis was found to be hY

(0.002)(100)/55 = 0.004%

The measured hysteresis was therefore much less than the design goal of 0.05%. i

7.3.5

THRESHOLD TESTS

The purpose of this test was to demonstrate that the system threshold, defined as

r

the largest sinusoidal input amplitude that may be applied at 0.01 Hz without producing output motion is less than 0.05% of°the input signal requiredto achieve k

h

full travel.

,.

The Frequency Response Analyzer was used to provide a 0.01 Hz sinusoidal_ input

}

command. Both the input and output signals were filtered using low pass filters with single lags at approximately 0.1 Hz. Several of the waveforms recorded on R79-2

7-38

OELCO ELECTRONICS DIVIS'ON • SANTA BARBARA OPERATIONS • GENERAL MOTORS CORPORATION

Output vs Input Motion with 0.7 Degree

q_1q `G!^

Peak-to-Peak A-^.plitude at 0.01 Hz

C I

Segment of Above Display Expanded 16 Times

Figure 7-9. Hysteresis Test Displays

R79-2•

n

t^

DELCO ELECTRONICS DIVISION • SANTA BAnSARA OPERATIONS • GENERAL MOTORS CORPORATION

r

OUTPUT INPUT

OUTPUT INPUT

Fi q ure 7-10. Input and Output Waveforms From Threshold Tests at an Amplitude of 0.016% of Full Travel

R79-2

7-40



DELCO ELECTRONICS DIVISION SANTA BARBARA OPERATIONS GENERAL MOTORS CORPORATION o

the storage oscilloscope are shown in Figure 7-10. The input waveform had an

-

f

amplitude of 0.009 degrees for the motion, which corresponds to ^J

^l (0.009)(100)/55

0.016%

of full travel. o

_

a i

The threshold was therefore found to be much less than 0.05% of full travel.

7.3.6

OUTPUT"VELOCITY TEST

The purpose of this test was to determine the maximum output velocity of the EMA. ,F

The system was driven at 0.2 Hz by the Frequency Response Analyzer with a square wave command having an amplitude large enough to cause velocity limiting. The input command and the output, position were recorded on a strip-chart rep-order

(see Figure 7-11). By measuring the slope of the output waveform, ^ output

:4

velocity of the EMA was determined

(4 degrees(/(0.295 second)

to h-

13.6 degrees/second

As an additional check on this measurement, the slewing speed of the motor (again from Figure 7-11) was found to be approximately 8,200 r/min. With a gear ratio of about 3,600:1 for the instrumentation gearbox, the output speed is found to be

(8,200 r/min)(360 deg/rev)(1 min/60s)/3,600 = 13.7 degrees/second

Figure 7-11 also shows the effects of^rbacklash and windup. The motor current builds up very rapidly after the step change in the input command The motor rpm trace also responds quickly to the input command, but the output motion (as sensed by the potentiometer coupled to the output shaft) shows _a dead time of °

bly a result of backlash in the approximately 0,05 second. This effect is proba ,N;

instrumentation geartrain and the effects of stiction and windup associated with the potentiometer's wiper and film e l ement. With anti-backlash gearing and an output position sensor having no sliding contact, these effects could undoubtedly be reduced significantly: _

t R79-2

1_

:,

7-41

c



DELCO ELECTRONICS DIVISION • SANTA BARBARA OPERATIONS • GENERAL MOTORS CORPORATION

+2 deg

.

-

t

INFUT COMMAND } ►

_

1

Run 17, 12 21-78,

_

-

2 deg

TL --

+2 deg

-

- -

-

--

-! -

OUTPUT MOTION-

2 deg I ^^„

^,.,^^,.„

1 ..„

.,,1 .,..1..,.1..

C^

0.295 second

^

+12500

-

-



-

n

1 __

7-7 - _

i

-

MOT OR RPM

_.

__

_.

•12500 1 ,...1.,.

1....

1.

1

1 .... 1 . ,

1

„^, ,^,.

0.1 second.

+125 A

MOTOR_CURRENT

i

- -

•125 A Figure 7-11. Waveforms from Output Velocity Test

R79-2

7-42

^u} u

DELCO ELECTRONICS DIVISION

SANTA BARBARA OPERATiONS



_.

o

GENERAL MOTORS CORPORATION 0

7.3.7

POSITION NULL TEST

\^

The purpose of this test was to demonstrate that with the input signal at zero, and with the positfion offset control set at zero, the output position of the EMA measured from its neutral position does not exceed 0.5% of full travel.

The null position of the EMA was measured and was found to be less than ± 0.2 degree.

The 0.5% position null design ,goal corresponds to an output of

(55 degrees)(0.005)=0.275 degree

J

The EMA therefore met the design goal for position null accuracy.

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