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NASA

AVRADCOM'technic al Memorandum 82979

Technical Report 82-C-14

AHS-RWP-7

Amy/NASA Small TurboshaftEngine Digital ControlsResearch Program -OOW%4

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R^ I ^ UV

J. F. Sellers and A. N. BaezLewis Research Center

^^^^ZZlZ 6`°Cleveland, Ohio

and

G. A. BobulaPropulsion LaboratoryAVRADCOM Research and Technology LaboratoriesLewis Research CenterCleveland, Ohio

(NASA — TH — S)- y 79) ALAY/NASA ScAi.L TURb(:SfiaFTENGINE DIGITAL LI NTROLS Rzz;tAhCfl etWBAM(NASA) 16 p HC AO^/tlF A01 LSCL 21E

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Prepared for theRotary Wing Propulsion System Specialist Meetingsponsored by the American Helicopter SocietyWilliamsburg, Virginia, November 16-18,1982

ORIGINAL PAGE ISOF POOR QUALITY

ARMY/NASA SMALL TURBOSHAFT ENGINE

DIGITAL CONTROLS RESEARCH

by J. F. Sellers and A. N. BaezNASA Lewis Research Center

andG. A. Bobula

Propulsion LaboratoryU.S. Army Research and Technology Laboratories

Cleveland, OH 44135

Abstract

A cooperative Army/NASA program to conductdigital controls research for small turboshaftengines is described. The participating agenciesare the Army RTL Propulsion Laboratory and NASALewis Research Center. The emphasis of theprogram _s on engine test evaluation of advancedcontrol logic using a flexiblemicroprocessor-based digital control system.

The engine test facility is an indoorsea-level stand. It includes a 2500-hpeddy-current dynamometer to absorb engir,: , shafthorsepower. The dynamometer control systemprovides capability to change the torque vs.speed characteristics of the load, thuspermitting varies rotor systems to besimulated. Flywheels are used to simulatevarious rotor moments of inertia. Thedynamometer controls are designed to provid=full-range load changes in less than one second.This provides the capability to evaluate systemresponse to rapid load changes such as thoseinduced by collective or cyclic pitch transientsin actual flight.

The digital control system used in thisprogram is designed specifically for research onadvanced control logic. Control software isstored in programmable memory. New controlalgorithms maybe stored in a floppy disk andloaded directly into memory. This featurefacilitates comparative evaluation of differentadvanced control modes. The central processor inthe digital control is an Intel 8086 16-bitmicroprocessor. Control software is programmedin assembly language. Software checkout isaccomplished prior to engine test by connectingthe digital control to a real-time hybridcomputer simulation of the engire.

The engine currently installed in thefacility is a General Electric YT700. Thisengine has a hydromechanical control for fuelflow and compressor variable geometry (VG). Thehydromechanical control has been modified toallow electrohydraulic fuel metering and VGactuation by the digital control. The researchobjective for this engine test is to demonstrateimproved power turbine speed governing comparedto the baseline control. The improvements resultfrom the application of modern control theory.

Simulation results are presented which show that

the modern control reduces the transient rotorspeed droop caused by unanticipated load changes

such as cyclic pitch or wind gust transients.

Introduction

Fuel control design has been a challengingproblem since the first application offree-turbine engines to helicopter propulsion.

The challenge arises because of the difficultrequirements imposed on the fuel control system.First, the fuel control is responsible for

maintaining rotor speed at the level requested bythe pilot, even in the face of large changes in

load imposed by extreme maneuvers such as powerrecovery from autorotation. Second, thetransmission/rotor system has complex,lightly-damped torsional dynamics within thebandwidth of the fuel control. These dynamicscan easily cause instability in a closed-loop,turbine-speed-governing system unless they arefully modeler in the analytical phase of controldesign. References 1-5 provide an excellentsummary of some of the problems encountered inpast helicopter development programs.

Design requirements for helicopter fuelcontrols are becoming even more demanding as are.>ult of the desire for improved helicoptermaneuverability, especially in nap-of-the-earthmilitary missions. Combined with the need forimproved maneuverability is the need for reducedpilot workload. Ideally, the pilot should beable to perform extreme maneuvers with confidencethat rotor spend will remain within safe limits.This would free his attention from monitoringrotor speed and enable him to concentrate on

other tasks. Several studies, (e.g., referencew6 and 7) have begun to explore the importantrelationship oetween engine control andhelicopte, handling qualities. Related work isalso underway (ref. 8) to develop genericmodeling techniques for predictingrotor,;ropul.sion system dynamic interactions.Accurate rotor/propulsion system models areessential for helicopter fuel control design andhandling qualities studies.

Fortunately, the emerging technology ofdigital control for helicopter engines holdssignificant promise for meeting the requirementsof improved maneuverability and reducel pilotworkload. Digital electronic fuel controls willallow greater freedom to transmit informationacross the flight/propulsion control interfaceand will permit the development o! functionally

integrated flight/propulsion controls. Further,digital control will permit more sophisticated

O

HW

IORIGINAI. PA-JC '.:'OF POGR QUALITY

6

TORQUE J

POWER TURBINESPEED

DISTURBANCETORQUE

TORQUEC0M AAND +-^ D yNAMOMETER

TORQUE

POWER COLLECTIVETURBINE PITCH

S PEED 9

Figure4. - Dynamometer control system.

ENGINE TORQUEPOWER TURBINE SPOWER TURBINE Ih

PRESSURE

REFERENCE

TURBINE SPEED ELECTRONIC F UEL FLOW FLOWCONTROL ENGINE

REFERENCE

PIFUEL

UNIT CONTROL CONTROLPOWER TURBINEINLET TEMPERATURE POWERAIN ROTOR

AVAILABLE COLLECTIVEINPUTS PITCH SETTING

Fl u re 5. - YT700 control system.

3 I

ORIGINAL PAGE 13

OF POOR QUALITY

nap-of-the-earth hel !opter missions. The

simulator is driven a digital computer which

solves the vehicle equations of motion in realtime. In order to evaluate integratedflight/propulsion control modes, the equations ofmotion must include fairly detailed models of thepropulsion system and its controls, as wall as acomplete representation of the vehicle and flightcontrols. The use of detailed propulsion modelsfor piloted simulation is a recent technologydeveloped at NASA Lewis to support research onthe AV-8A Harrier V/STOL aircraft (refs. 13-14).Accurate propulsion modeling can be important forvehicles such as V/STOL and helicopters whichdepend on their propulsion systems for basic liftand attitude control forces. A detailed model ofthe engine control system is essential if fuelcontrol effects on handling qualities are to befully evaluated.

As shown in figure 1, a flight/propulsior.control integration program should logically leadto flight experiments using a researchhelicopter. Flight testing would be used forfinal evaluation of integrated c. •ntrol modeswhich have been screened and refin,d throughanalysis and simulation. As envisio..-d Sere, theflight test veh'.cle would use a flexible researchcontrol system capable of evaluating a variety ofintegrated control modes. Thus far, the plannedAmes/Lewis program extends only through pilotedsimulator evaluation of _ntegrated control modes,since this can be accomplished at a reascnablylow cost. Funding for flight iardwaredevelopment is not yet available.

Engine testing, as shown in figure 1, is an

essential element of the overall program. Enginetesting will be used to validate math models ofengine dynamics. Integrated control modes willbe evaluated through engine testing, to the

extent that this is possible in the absence ofreal rotor and transmission hardware. In theremainder of this paper, the plans and status ofthe engine test program will be described ingreater detail.

Fngine Test Facility

Figure 3 is a photograph of the smallturboahaft engine test facility which is nowoperational at NASA Lewis. This facility wasdeveloped cooperatively by Lewis and the ArmyPropulsion Lab. The engine currently installedin the facility is a General Electric YT700,although the test cell can be used for otherengines in the future. The test cell is limitedto sea level operating conditions and includes adynamometer to absorb shaft output power. Theengine inlet duct includes a hydrogen burner tosupply inlet temperature distortion.

The YT700 was selected as the first enginefor use in this program because it was the latesttechnology engine available with an ample supplyof spare parts. The YT700 contains components

representative of other current technology smallturboshaft engines. It has a five-stage

axial/single-stage centrifugal compressor with

variable stators and bleeds. The core compressor

in driven by a two-stage, air-cooled turbine.The two-stage power turbine drives the outputshaft which exits through the front of the engineto a gearbox and then to the dynamometer.

The facility uses an eddy-current dynamometersupplied by Eaton Corporation. it has a maximumrating of 2500 horsepower. Helicopter rotorinertia is simulated by flywheels which can bechanged to represent different rotors. A unigrefeature of this dynamometer is its control systemwhich was designed specifically to simulate thetorque vs. speed characteristics of a helicopterrotor. A schematic of the dynamometer controlsystem is shown in figure {. The torque outputof the dynamometer is measured and fed back toform a closed-loop torque control system. Thetorque command signal to the dynamometer is afunc• ion of power turbine speed and collectivepitcn of the simulated rotor. The collectivepitch signal is also sent to the engine controlsystem. The torque command can be changed tosimulate load changes such as those induced bycyclic pitch or wind gusts. The torque controlloop is designed for maximum speed of response.The design goal was to be able to change thetorque load over its full range in less than onesecond. This will permit evaluation of theresponse of control modes to large, rapid loadchanges.

Research Control System

The baseline YT700 control system is shownschematically in figure S. This system `s ahydromechanical/analog electronic control. Thehydromechanical unit (HMU) provides gas generatorspeed governing, variable geometry (VG)scheduling and actuation, and fuel pumping and

metering. The electronic unit (ECU) providespower turbine speed governing, temperaturelimiting, and torque matching in multiple engineinstallations. An excellent description of theYT700's control system is provided in ref. 15.

To use the YT700 as a testbed for digitalcontrols research, it was necessary to add aresearch digital control unit and to modify theHMU so that the research digital control wouldhave full authority over the fuel metering and VGactuation functions. The approach taken was toellpinate the mechanical computing functions fromthe HMU, but to retain the fuel pumping/meteringand VG actuation hardware. Electrohydraulicservoval-es were added to drive the fuel meteringvalve and VG actuators. Linear variabledifferential transformers (LVDT's) were added tomeasure fuel metering valve and VG actuatorpositions. The actuators are driven by fuelpressure supplied by the fuel pump. Since theactuation hardware is, for the most part,identical to that used in production T700engines, the actuator response capability can beconsidered representative of state-of-the-art

flight hardware. The modified HMU was developed

OaMNAL PAGE 13Of POOR QUALI"N

under contract by General Electric and HamiltonStandard. A photo of the modified HMU is shown

in figure 6.

A separate unit, referred to as the 'loopcloser" was developed to close the LVDT positionfeedback loops and drive the electrohydraulicservovalves. These loops are closed using analogelectronics. V:-.:z, the digital control unitsimply sends a 0-10 volt analog command signal tothe loop closer for each of the two actuators.The loop closer can also be configured to closethe actuator loops through the digital control,should this be desired for research purposeslater in the program. The loop closer was also

developed by General Electric and HamiltonStandard. A photo of the loop closer is shown infigure 7.

A schematic of the overall research controlsystem is shown in figure 8. For the most part,the existing sensors in the YT700 control systemare used. Exceptions are gas generator speed(Ng), compressor dischar , _ pressure (P5 3), andcompressor inlet tempera`:re (T2 ). Thesesensors are hydromechanikal in the YT700 control

and had to be replaced with electrical sensorsthat could communicate with the digital control.Ng is now derived from alternator frequency,Ps i is measured with s:rain gage pressuretransducers, an9 T2 is measured by athermocouple rake at the compressor inlet.

Since the research control system is designedto evaluate control modes rather than digitalcontrol architecture, no attempt was made todevelop a fault-tolerant control system.Instead, the system is designed to be fail-safe. The strategy is to cut back fuel tominimum flow and to move the compressor variablegeometry to closed vane position whenever afailure is dete-ted in the sensors or theelectronics. External safety systems, com-pletely independent of the digital control,protect the engine in the event of overspeed,overtemperature, off-schedule VG transients, orexcessive vibration.

The heart of the resea —h control system isthe digital computer its if, referred to as theEngine Monitoring and Control (EMAC) unit. TheEMAC was designed to provide maximum flexibilityfor changing the input/output configuration andcontrol software.

EMAC System Description

The engine monitoring and control (EMAC) unitconsists of two main systems, the monitoring unitand the control unit. The main function of themonitoring unit is to display, either in volts orengineering units (EU), all the information thatccmes into and out of the EMAC unit. This unitalso allows the user to interrogate the controlsystem while it is running. The monitoring unitcontains status and warning lights to be used by

the control engineer and switches to initializethe control and select the control mode. The

control unit's main function is to execute the

control algorithms required for engineoperation. A more detailed description of theEMAC unit is presented below.

A block diagram showing the main componentsof the monitcring unit is illustrated in figure9. The heart of the monitoring unit is a customdesign microcomputer. This microcomputer isbased on the Intel Corp. 8695A-2 micro-

proc ;sor. The 8085A-2 has a 0.8 microsecondinstruction cycle and a 5 MHz internal clock.The microcomputer system consists of 81 bytes ofProgrammable Read Only Masonry (PROM), lK byres ofRandom Access Memory (RAM), six 8-bit parallelinput/output ports, and a programmablekeyboard/display controller.

The cons:ol unit consists of acommercially-available, single board micro-computer, an analog input multiplexer (ML'R)board, an analog output board, a discrete inputboard, and a floppy diskette hardware system.Communication between the user and the controlmicrocomputer is accomplished by means of aDecwriter.

The single board microcomputer is the InteliS8C 86/12A. w►:!ch is based on the 8086 16-bitmicroprocessor. °he 8086 has a basic instructioncycle of 400 nanoseconds and a 5 MHz internalsystem clock. The iSBC 86/12A board contains 64Kbytes of RAM, 16K bytes of EPROM, 24 programmableparallel I/O ports, 2 programmable 16-bit BCD orbinary timers/event counters, 9 levels ofvectored interrupt control, and an iSBC 337 high

speed numeric data processor. The iSB 337provides high speed fixed and floating pointfunctions and is based on the 8087 numeric datAprocessor.

The memory size and processing capability ofthe control unit exceed the requirements forsmall turboshaft engine control.. The excesscapability was designed into the EMAC tofacilitate the pro, amming of new controlalgorithms, and to permit on-line data processinSand storage. The floppy disk system serves twofunctions: storage of software for convenientdownloading intc program memory, and storage ofdata taken during engi..e testing. These featuresenhance the EMAC • s capability as a research tool.

A signal flow diagram of the EMAC unit isshown in figure 10. A total of 100 channels areavailable as inputs. Eighty of these channelsare split and fed to a switching matrix and to apatct panel in the EMAC unit. The other 20channels are dedicated to strip chart recordersand analog data recorders. All input and outputsignals are fed to the patch panel. This featurepermits user selection of any configuration ofinputs and outputs, which could change withdifferent applications of the EMAC unit.

Software Description

The monitoring unit software is all

4

ORIGINAL Pj^r:^,OF Pour, `. ,

programmed in assembly lanquaae and is stored in

EPROM. The software package includes a mainprogram or executive, an initialisation routine,an input routine, a computational routine, a

table look up routine, an output routine, and a

data storage routine.

The control unit support software includes aCPM/P6 operating system, a bootstrap loader, in

analog input/output diagnostic, and a discre.+,input/output diagnostic. CP14/86 is a single useroperating system for the Intel 8086 16-bitmicrocomputer family. Control unit software iscurrently programmed in 16 -bit fixed-pointarithmetic using assembly language, althoughfuture plans include the evaluation of

floating -point arithmetic and high-orderlanguages. Assembling .7nd linking the vari.,ussoftware modules is done using an Inteldevelopment system. The final software is storedon floppy disks. Use of the development system

permits software to be edited and assembledwithout using the EMAC itself.

The flexibility of .he EMAC's design makes ita useful research tool for evaluating a varietyof advanced digital control modes. A photo ofthe EMAC is shown in figure 11.

Real-Time Engine Simulation

A real-time engine simulation is a valuabletool for evaluating advanced control mo ,.zs. Itcan -)e used during thz study phase of a researchprogram, during which v , rious control modes erecompered and the most promising are selected forengine test evaluation. Once the final controlmodes are selected and programmed into thedigital control, the real-time simulation becomesa valuable aid in debugging the digital controlsoftware. For this program, the Hybrid ComputerSimulation facility at NASA Lewis is being usedto provide real-time simulation of smallturboshaft engines Such as the YT700. A photo ofthis facility is shown in figure 12. The hybridcomputing equipment is supplied by ElectronicAssociates, Inc. (EAI).

A real-time simulation of the YT700 anddynamometer is currently operational on thehybrid computers at NASA Lewis. The simulationincludes compressor and turbine maps derived fromactual engine test data using the YT700 in thesea level stand. The use of actual engine datawas desirable for this program because the YT700is configured for compressor inlet distortionexperiments and has higher compressor blAe tipclearances than do production engines.Consequently, compressor performance is differentthan for a nominal specification T70G.Preliminary results indicate excellent agreementbetween simulated and measured performance.Figure 13 shows one example of the agreementbetween the simulation and engine data. Sincethe simulation is intended for use in evaluatngcontrol modes prior to engine test, close

a g reement is highly desirabl es to ensure asuccessful test.

Program Status and Plans

The first test of the YT700 under EMACcontrol is scheduled for December 1982. Controllogic for the first engine test will be a digitalemulation of the baseline YT700 control logicwhich is currently implemented in thehydromechanical/analog electronic control shownin figure S. Use of the baseline YT700 control

logic will guarantee minimum risk while enginetest experience is gained with the modified HMU,the loop closer, and the EMAC. When confidenceis established in 'he research control hardware,work on advanced control modes can begin.

Figure 14 shows the schedule for developingand testing advanced control logic. Work onintegrated control modes will be conductedcooperatively by the Army, NASA, and GeneralElectric. The objective of the engine testprogram is to evaluate integrated control modesfor reducing transient rotor speed droop duringmaneuvers (e.g. power recovery from autorotation)or unanticipated disturbances such as windgists. One aspect of this effort will be todetermine if additional control inputs,specifically compressor variable geometry, can beused in a multiloop control mode to help reducetransient rotor speed droop. In the baselinecontrol mode, compressor variable geometry isscheduled with respect to gas generator correctedspeed and :a not affected by power turbinespeed. Since compressor variable geometryaffects engine airflow, it may provide a usefulcontrol input in combination with fuel flow.

Another aspect of the research effort will beto co; ,sider additional sensors, specificallytorque, as inputs to a multiloop control.Preliminary analysis performed by GeneralElectric indicates that a multivariable controlsystem can reduce transient rotor speed drooprelative to the baseline control logic. Figure15 shows simulated power turbine speed and torqueresponses for an unanticipated load change suchas might be induced by a cyclic pitch transientduring a steep turn maneuver. As shown in figure15, the multivariable control re :uces rotor speeddroop by about half in comparison co the baselinelogic. The multivariable control uses torque andpower turbine sped measurements to suppress themain and tail rotor torsional resonances, therebypermitting a higher gain control loop on powerturbine speed.

The research control hardware fabrication andtest phase of the Army/NASA digital controlsprogram is essentiall : • complete. The EMAC unitis now being used to control the real -time YT700hybrid simulation using the baseline controllogic. Future work will concentrate on advancedcontrol modes. Continuous EMAC software updateswill be required as advanced control modes aredeveloped to the point of engine test. Thehybrid simulation will also be updated asadditional engine data is acquired.

5

ORIGINAL PAGE L

OF POOR QUALITY

Concluding Remarks

The rationale and approach for an Army/NASA

helicopter integrated flight/ propulsion control

program have been presented. The approach

emphasizes:

1. Development of generic math model- of

engine/rotor/vehicle dynamics

2. Evaluation of a variety of integratedcontrol modes using total system simulationsincluding eventual pilot-in-the-loop simulationsat NASA Ames

3. Experimental validation of math modelsand integrated control modes using engine testsand eventual flight tests with flexible research

control systems.

The plans and status for the engine testphas, of the program were discussed in detail.Engine testing will be performed cooperativel y by

the Army and NASA using a sea level test stand atNASA Lewis. The engine currently installed iiithe facility is a General Electric YT700. Thefacility includes a dynamometer designed tosimulate rapid load transients typical of heli-

copter operations.

A unique aspect of the program is the use ofan Engine Monitoring and Control (EMAC) unit, aresearch digital control system designed topermit the implementation and evaluation of avariety of integrated control modes. Another keyaspect of the program is real-time enginesimulation using the hybrid computing facility atNASA Lewis. The real-time engine simulation per-mits extensive checkout of control logic prior to

engine test.

A specific objective of the engine testprogram is to evaluate improvements in powerturbine speed control made possible through theapplication of modern multivariable controltheory. Results were presented which indicatethat multivariable control can provide reduced

power turbine speed droop, compared to thebaseline control, f-)r unanticipated load changes.

By late 1982, the small turboshaft enginedigital controls research facility is scheduledto be fully operational. The facility willprovide capability to support a variety offlight/propulsion control integratior experimentsfor the Army and NASA.

REFERENCES

1. Ri0ardson, D.A. and Alwang, J.R.,"Eng'.:a/Airframe/Drive Train DynamicInterface Documentation," USARTL-TR-78-11,April 1978.

2. Needham, J.F. and Banerjee, D.,"Engine/Airframe/Drive Train Dynamic

Interface Documentation,' USARTL-TR-78-12,May 1978.

3. Twomey, M.J. and Sam, E.B., "Review of

Engine/Airframe/Drive Train Dynamic Interface

Development Prob4as," USARTL-TR-78-13, June

1978.

6. Bowe*, K.A., 'Engine/Airframe/Drive Trait.Dynamic Interface Documentation,"USARTL-TR-78-14, June 1978.

5. Hanson, H.N., Balks, R.W., Edwards, B.D.,Riley, W.W., and Downs, B.D.,"Engire/Airframe/Drive Train DynamicInterface Documentation," USARTL-TR-78-15,October 1978.

6. Kuczynski, W.A., Cooper, D.E., Twomey, N.J.and Howlett, J.J., "The Influence ofEngine/Fuel Control Design On HelicopterDynamics and Handling Qualities," Journal ofthe American Helicopter Society, Vol. 25. No.2, April 1980, pp. 26-34.

7. .Corliss, L.D., "A Helicopter HandlingQualities Study of the Effects of EngineResponse Characteristics, Height ControlDynamics, and Excess Power OnNap-Of-The-Earth Operations," Paper Presentedat the AHS/NASA Specialists' Meeting onHelicopter Handling Qualities, Palo Alto,

California, April 1982.

8. Warmbrodt, W., and Hull, R., "Development ofa Helicopter Rotor/Propulsion System DynamicAnalysis," Paper Presented at AIM/ASME/SAE

18th Joint Propulsion Conference, Cleveland,Ohio, Jump 1982.

9. Morrison, T.; Howlett, J.t and Zagranski, R.:"Adaptive Fuel Control FeasibilityInvestigation for Helicopter Applications,"ASME-82-GT-205, April 1982.

10. Bolton, R. L.: "Adaptive Fuel ControlFeasibility Investigation," AHS PaperA-82-38 15-7000, presented at 38th Annual AHSForum, May 1982.

11. Zeller, J., Lehtir.en, B. and Merrill, W.,"The Role of Modern Control Theory in theDesign of Controls for Aircraft TurbineEngines," NASA TM-82815. Jan. 1982.

12. Howlett, J.J., 'UH-60A Blackhawk EngineeringSimulation Program," NASA CR-166309, Dec.1981.

13. Mihaloew, J.R., Roth, S.P.. and Creekmore,R., 'A Real-Time Pegasus Propulsion SystemModel for VSTOL Piloted SimulationEvaluation," NASA TM-82770, Dec. 1981.

11. Mihaloew, J.R. and Roth, S.P., "A PiecewiseLinear State Variable Technique for Real-TimePropulsion System Simulation,' NASA TM-82851April 1982.

15. Curran, J.J., 'T700 Fuel and Control System,Paper Presented at 29th Annual ANS Forum, Me

1973.

6

ORUNAL PARE !'°

OF POOR QUAL-111"

NASA LEWISARMY PROPULSION LAB

PROPULSION ENGINEMODELING TEST

INTEGRATED CONTROLMODE DEVELOPMENT

PLANS I HOPES

PROPULSIONCONTROL ENGINEHARDWARE TESTDEVELOPMENT [

PILOTEDFLIGHT

DEVELOPMENROL

FLIGHTHARDWARETESTSIMULATION

VEHICLE/ROTORMODELING

NASA AMESARMY AEROMECHANICS LAB

Figure 1. - Rotorcraft integrated flightlpropulsion control.

KiN

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4

ORIGINAL PAGE ISOF POOR QUALITY

ORIGINAL. PA a<OF POOR QIJALI "t'1r'

DISTURBANCE

A'

TORQUECOMMAND

TORQUE J

POWER TURBINESPEED

D YNAMOMETERTORQUE

POWER COLLECTIVETURBINE PITCH

SPEED 9

Fiyure4. - Dynamometer control system.

ENGINE TORQUE

f GAS GENERATOR SPEED

REFERENCE +TURBINE SPEED ELECTRONIC F UEL FLOW HYDRO- FUEL FLOW

CONTROL MECHANICAL ENGINEREFERENCE UNIT CONTROL UNIT CONTROLPOWER TURBINEINLET TEMPERATURE POWER MAIN ROTOR

AVAILABLE COLLECTIVEINPUTS PITCH SETTING

Figure 5. - MOO control system.

0 1

ORIGINAL PAGE SOF POOR QUALITY

Figure 6. - Modified hydromechamcal unit.

Figure 7. - Loop closer.

ORIGINAL PAGE ISOF POOR QUALITY

r----- r----IENGINE W F LVDT FIB^T, MONITORING WF DEMAND LOOP VG LVDT FIB

AND CLOSERCONTROL VG DEMAND ,-- W TIM CURRENT HMUUNIT RELAY; V TIM C URRENT

PS 3 lEMAC! ^__ i J

LOOP CLOSER STATUS SIGNALSFACILITY

FMERGENCY TIM CUTOUT FUEL BYPASSVALVE

CONTROL

LOGIC/ NG OVERSPEED; Th. 5 OVERTEMP: STALL

NP OVERSPEFD SEQUENCEVALVE

FAILURE

LOGIC T4 5

TORQUE TECU YT 700N

ENGINE c

V G LINEAR POT STALLDETECTION

V G POSITION TRANSDUCERSTALL DETECTION

Figure & - Y'700 research digital control system.

DIGITAL

--- ANALOGALPhANUMERICDISPLAY

C^IANNELtl085 Di SPLAY

KEYBOARD MICRO-

COMPUTER

EUIV

SWITCH L _

MATRIX _ SCALING __ DTClRCU^TRY

Figure 9. - EMAC monitorirg unit

ORIGIN AL PAGE 12

OF POOR QUALITY

^^ IIU ^^nr;til ti uPROCESSo,tDE HA20 RECORR CNN .ti PAICH iSBC 660

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Figure 12.- Hybrid computer facility.

inn

FUEL FLOW LBlhr

Figure 13. - Comparison of real-time hybrid simulationwith engine dzta.

ORIGINAL

POOR QV^

OF "yCY81 82 83 84

REAL-TIME ENGINE SIMULATION

DIGITAL CONTROL HARDWARE

DIGITAL CONTROL SOFTWARE

INTEGRATED CONTROL MODES

NASAIARMY ENGINE TEST

GENERAL MECHANICAL INTERFACE HARDWARE

ELECTRIC

I INTEGRATED CONTROL MODES I

Figure 14. - Small turboshaft controls program.

110

Z 100

NP (POWER TURBINE SPEED)

300 1^Q (SHAFT TORQUE)

200

a'

100 (a)0 2 3 4 5 6 7 8 9

TIME, sec

85

a110

z

100

300

Cr

200

TIME(a) Typical steep turn or approach transient for baseline system.

(b) Typical steep turn or approach tra lcient for multi-input system.

Figure 15 - Comparison of rotor speed responses for base-line and multivaviable control systems,