19880002298 · Flight propulsion control integration for V/STOL aircraft

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NASA Technical Memorandum 100226 I

Flight Propulsion Control Integration

for V/STOL Aircraft

- ~ _ _ (NAS A-TH- 180226) FLIGHT PROPCJLS Z O F CONTROL N88- 11680 I N T E G R A T I O N F O R V/STOL A I R C R A F T (NASA) 22 p A v a i l : NTIS HC AO3/HF A Q 1 C S C L O l C t h c l a s G3/Q8 0107321 I

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Santa Clara, California, Decemkr 7-10, 1987

FLIGHT PROPULSION CONTROL INTEGRATION FOR V/STOL AIRCRAFT James R. Mihaloew N a t i o n a l Aeronautics and Space A d m i n i s t r a t i o n Lewis Research Center Cleveland, Ohio 44135 ABSTRACT The goal o f t h e p r o p u l s i o n community i s t o have t h e e n a b l i n g p r o p u l s i o n a t o p e r m i t a low r i s k d e c i s i o n r e g a r d i n g t h e i n i t i a t i o n technologies i n p l a c e o f a research STOVL supersonic a t t a c k l f i g h t e r a i r c r a f t i n t h e mid-1990's.

This technology w i l l e f f e c t i v e l y i n t e g r a t e , enhance, and extend t h e supersonic c r u i s e , STOVL, and f i g h t e r / a t t a c k programs t o enable U . S . i n d u s t r y t o develop a r e v o l u t i o n a r y supersonic s h o r t t a k e o f f i v e r t i c a l l a n d i n g f i g h t e r i a t t a c k a i r - 4 c r a f t i n the post-ATF p e r i o d . The r a t i o n a l e , methods, and c r i t e r i a used i n I v) developing a j o i n t NASA Lewis and NASA Ames research program t o develop t h e d technology element for i n t e g r a t e d f l i g h t - p r o p u l s i o n c o n t r o l through i n t e g r a t e d % methodologies i s presented. This program, t h e Supersonic STOVL I n t e g r a t e d w I F l i g h t - P r o p u l s i o n C o n t r o l s Program, i s p a r t o f t h e o v e r a l l NASA Lewis Super- sonic STOVL P r o p u l s i o n Technology Program. I t uses an i n t e g r a t e d approach t o an i n t e g r a t e d program t o achieve i n t e g r a t e d f l i g h t - p r o p u l s i o n c o n t r o l technology.

During the 1970's many i n n o v a t i v e a i r c r a f t c o n f i g u r a t i o n s were proposed as v i a b l e s o l u t i o n s t o V/STOL m i s s i o n requirements. High-performance propul- s i o n systems w e r e conceived f o r these V/STOL a i r c r a f t . These p r o p u l s i v e l i f t concepts c o n s i s t e d o f remote l i f t fans d r i v e n by r i g i d s h a f t s or ducted h i g h energy gas, l i f t l c r u i s e n a c e l l e s , t h r u s t v e c t o r i n g swivel nozzles, remote aug- mentors, and r e a c t i o n c o n t r o l /compressor bleed s y s t e m s . The p r i m a r y problem i n developing p r o p u l s i o n system concepts i s t o design s y s t e m s which p r o v i d e the r e q u i r e d a i r c r a f t h a n d l i n g q u a l i t i e s i n p o w e r e d - l i f t modes w i t h o u t r o b b i n g the powerplant o f i t s a b i l i t y t o perform s a f e l y and economically. During low speed o p e r a t i o n s V/STOL a i r c r a f t a r e n o t o n l y dependent upon these p r o p u l s i o n systems f o r lift, b u t a l s o for the f o r c e s and moments needed f o r f l i g h t p a t h a n d a t t i t u d e c o n t r o l . T h u s , h i g h l y c o o r d i n a t e d f l i g h t a n d p r o p u l s i o n c o n t r o l systems a r e c r i t i c a l t a the success of these advanced V/STOL a i r c r a f t .

The need f o r new, i n t e g r a t e d V/STOL a i r c r a f t and p r o p u l s i o n c o n t r o l con- cepts has developed a t the same t i m e t h a t g r e a t changes a r e t a k i n g p l a c e i n t h e f i e l d o f aerospace c o n t r o l s . The microprocessor r e v o l u t i o n i s producing v e r y low c o s t , high-speed computation which w i l l make many c o n t r o l s y s t e m implementation concepts f e a s i b l e t h a t j u s t a few years ago would have been economically impossible and p h y s i c a l l y i m p r a c t i c a l due t o c o n t r o l f u n c t i o n com- p l e x i t y . This technology development has d r a m a t i c a l l y improved computer r e l i a - b i l i t y and f u n c t i o n a l c a p a b i l i t y and w i l l have a profound impact on a l l f u t u r e engine and a i r c r a f t designs. However, t h e main problem i n f l i g h t - p r o p u l s i o n i n t e g r a t i o n f r o m a r e l i a b i l i t y v i e w p o i n t i s t h a t p r o p u l s i o n c o n t r o l r e l i a b i l - i t y must reach f l i g h t c o n t r o l r e l i a b i l i t y l e v e l s .

H i s t o r i c a l l y , a i r c r a f t design has been based on t h e p h i l o s o p h y t h a t f l i g h t and p r o p u l s i o n c o n t r o l s can be designed independently. This p h i l o s o p h y assumed t h a t the p i l o t c o u l d e f f e c t i v e l y i n t e g r a t e these subsystems by h i s con- t r o l i n p u t s . Future m i s s i o n requirements, e s p e c i a l l y for p o w e r e d - l i f t a i r - c r a f t , demand improved o p e r a t i o n a l c a p a b i l i t i e s so t h a t t h e p i l o t ' s a t t e n t i o n can no l o n g e r be d i r e c t e d t o i n t e g r a t i n g t h e f l i g h t and p r o p u l s i o n c o n t r o l sub- systems. He must i n s t e a d d i r e c t h i s a t t e n t i o n to h i g h e r l e v e l s o f concern as demanded by h i s m i s s i o n and m o n i t o r the progress o f h i s m i s s i o n through t h e o f t h e f l i g h t and p r o p u l s i o n subsystems w i l l imposed t h r e a t s . The i n t e g r a t i o n a l l o w t h e p i l o t g r e a t e r a t t e n t i o n t o those h i g h e r l e v e l s o f concern by sup- p l a n t i n g a good p a r t of t h e p i l o t ' s i n t e g r a t i o n f u n c t i o n and thereby reduce p i l o t workload.

F u n c t i o n a l subsystem i n t e g r a t i o n holds n o t o n l y t h e promise o f a c h i e v i n g reduced p i l o t workload b u t a l s o o f improving t h e performance o f the t o t a l f l i g h t system. I n t e g r a t i o n w i l l c o o r d i n a t e v a r i o u s system f u n c t i o n s associ- a t e d w i t h a i r f r a m e , i n l e t , engine, nozzle, a t t i t u d e c o n t r o l , and o t h e r t h r u s t e f f e c t o r s . The a i r c r a f t c o n t r o l a c t i o n s w i l l be c o o r d i n a t e d i n a g l o b a l sense t o o p t i m i z e o p e r a t i o n i n a l l f l i g h t modes. I n the process, system e f f i c i e n c y should increase which should r e s u l t i n s m a l l e r p r o p u l s i o n systems w i t h a subse- quent lower V/STOL p e n a l t y .

C l a s s i c a l design methods and approaches a r e g e n e r a l l y inadequate t o a t t a c k i n t e g r a t e d c o n t r o l s i n c e they do n o t account for, i n a systematic man- t h e i n h e r e n t cross-couplings of an i n t e g r a t e d s y s t e m . I t w i l l o b v i o u s l y ner, be necessary to t r e a t t h e e n t i r e a i r c r a f t as one dynamic system. Therefore, advanced design methods w i t h i n t h e c o n t e x t o f an i n t e g r a t e d c o n t r o l design methodology must be employed t o achieve t h i s h i g h l e v e l o f a i r c r a f t systems i n t e g r a t i o n and t h e degree o f c o o r d i n a t i o n r e q u i r e d between a i r f r a m e and engine c o n t r o l designers w i l l have t o be increased w e l l beyond t h a t of conventional programs.

This paper w i l l present t h e r a t i o n a l e , methods, and c r i t e r i a i n develop- i n g a j o i n t NASA Lewis and Ames research program t o develop the technology for i n t e g r a t e d f l i g h t - p r o p u l s i o n c o n t r o l through i n t e g r a t e d methodologies. This program, t h e Supersonic STOVL I n t e g r a t e d F l i g h t - P r o p u l s i o n C o n t r o l s Program, i s p a r t o f t h e o v e r a l l NASA Lewis Supersonic STOVL P r o p u l s i o n Technology Pro- gram. It uses an i n t e g r a t e d program approach to achieve i n t e g r a t e d f l i g h t - p r o p u l s i o n c o n t r o l technology.

HISTORICAL PERSPECTIVE - Several p a s t and c o n t i n u i n g research programs have addressed i n t e g r a t e d f l i g h t - p r o p u l s i o n c o n t r o l . The f i r s t o f these, the I n t e g r a t e d P r o p u l s i o n C o n t r o l System ( I P C S ) ( r e f . 1 ) begun i n the l a t e 1960's, was a f l i g h t t e s t program t o i n t e g r a t e t h e i n l e t and engine c o n t r o l systems f o r i n l e t shock and automatic r e s t a r t c o n t r o l . An F-111 w i t h an airframe-mounted d i g i t a l computer was used t o t e s t a f u l l - a u t h o r i t y c o n t r o l on t h e l e f t i n l e t and engine.

Soon a f t e r , the Q u i e t Clean Short-haul Experimental Engine (QCSEE) was evaluated i n c o n j u n c t i o n w i t h a p i l o t e d s i m u l a t o r i n v e s t i g a t i o n o f engine f a i l - The study ure compensation for p o w e r e d - l i f t STOL a i r c r a f t ( r e f s . 2 and 3 ) .

p o i n t e d up the requirement f o r an i n t e g r a t e d a i r c r a f t p r o p u l s i o n system approach for h i g h response, close-coupled powered lift s y s t e m s .

In-depth s t u d i e s o f f l i g h t - p r o p u l s i o n c o n t r o l i n t e g r a t i o n w e r e conducted A i r Force i n t h e mid-1970's. The s t u d i e s i n c l u d e d t h e F l i g h t by the P r o p u l s i o n C o n t r o l Coupling (FPCC) program, t h e dynamic i n t e r a c t i o n i n v e s t i g a - t i o n ( r e f s . 4 and 5) and were f o l l o w e d by t h e C o n t r o l Configured P r o p u l s i o n (CCP) design c r i t e r i a d e f i n i t i o n ( r e f . 6). Other s t u d i e s by NASA i n c l u d e d t h e Cooperative A i r f r a m e / P r o p u l s i o n / C o n t r o l System program ( r e f . 7) and the I n t e - g r a t e d Research A i r c r a f t Technology (INTERACT) p r o j e c t ( r e f . 8 ) . The former demonstrated d i g i t a l l y i n t e g r a t e d i n l e t l a u t o p i l o t / a u t o t h r o t t l e c o n t r o l on a YF-12. INTERACT was a f u r t h e r f l i g h t / p r o p u l s i o n i n t e g r a t i o n program which a l s o demonstrated s i g n i f i c a n t b e n e f i t s of c o n t r o l i n t e g r a t i o n .

I n t h e l a t e 197O's, NASA pursued a c o n t r o l concept d e f i n i t i o n program to i n v e s t i g a t e t h e b a s i c changes i n f l i g h t and p r o p u l s i o n c o n t r o l design r a t i o n - a l e , c r i t e r i a and methodology needed t o take maximum advantage o f advances i n c o n t r o l technology. The V/STOL C o n t r o l s A n a l y s i s Program, conducted by NASA Lewis, was i n i t i a t e d i n 1979 w i t h t h e r e a l i z a t i o n t h a t b a s i c and profound changes i n f l i g h t and p r o p u l s i o n c o n t r o l design were needed t o take maximum advantage o f advanced c o n t r o l technology for t h e n e x t g e n e r a t i o n , b o t h sub- sonic and supersonic, V/STOL a i r c r a f t . The i n i t i a l s t e p o f t h i s c o n t r o l con- cept i n v e s t i g a t i o n was t o review t h e V/STOL p r o p u l s i o n c o n t r o l technology requirements. Emerging from the myriad of v i a b l e V/STOL a i r c r a f t c o n f i g u r a - tions were many g e n e r i c p r o p u l s i o n components t h a t must be c o n t r o l l e d and i n t e - g r a t e d w i t h t h e f l i g h t c o n t r o l laws. A s a r e s u l t , many c h a l l e n g i n g c o n t r o l issues were found t h a t needed t o be r e s o l v e d .

The V/STOL C o n t r o l s A n a l y s i s Program ( r e f s . 9 and 10) p r o v i d e d an i n i t i a l s t e p toward t h e development o f the methodology and technology base r e q u i r e d for the i n t e g r a t i o n o f V/STOL a i r c r a f t - p r o p u l s i o n c o n t r o l systems. The pro- gram c o n s i s t e d of a t e c h n i c a l e f f o r t d i v i d e d i n t o two phases t o i n i t i a t e the development of t h e technology base r e q u i r e d for V/STOL a i r c r a f t p r o t o t y p e development. Phase I pursued f o r m u l a t i o n of a l o n g range p l a n t o e s t a b l i s h t h e technology base for t h e design of V/STOL i n t e g r a t e d a i r c r a f t - p r o p u l s i o n c o n t r o l , e s t a b l i s h e d p r e l i m i n a r y V/STOL p r o p u l s f o n c o n t r o l requirements, and developed mathematical modeling and s i m u l a t i o n techniques a p p l i c a b l e t o t h e design o f V/STOL i n t e g r a t e d a i r c r a f t - p r o p u l s i o n c o n t r o l s . A technology p l a n from one o f t h e two s t u d i e s , as d e p i c t e d i n f i g u r e 1, was one o f the p r i m a r y o u t p u t s of t h i s phase. Phase I 1 e f f o r t s addressed i n t e g r a t i o n o f a i r c r a f t requirements i n t o V/STOL p r o p u l s i o n c o n t r o l technology development , develop- ment of mathematical modeling and s i m u l a t i o n techniques for i n t e g r a t i o n o f the f l i g h t and p r o p u l s i o n c o n t r o l o f v a r i o u s V/STOL t h r u s t e f f e c t o r s , development o f p r o p u l s i o n c o n t r o l design methodology and l o g i c capable o f m o d u l a t i n g t h e v a r i o u s V/STOL t h r u s t e f f e c t o r s w i t h i n safe p r o p u l s i o n system 1 i m i t s , and t h e assessment o f t h e a b i l i t y o f V/STOL t h r u s t e f f e c t o r s t o meet a i r c r a f t c o n t r o l requirements. The research represented t h e completion o f 2 years o f a formu- l a t e d 6 year technology p l a n producing r e s u l t s a p p l i c a b l e t o t h e i n t e g r a t i o n o f f l i g h t and p r o p u l s i o n c o n t r o l s y s t e m s .

As a c o n t i n u a t i o n o f the concept o f i n t e g r a t e d f l i g h t - p r o p u l s i o n c o n t r o l i n t e g r a t i o n , t h e A i r Force Wright A e r o n a u t i c a l Laboratory (AFWAL) sponsored a program wherein teams o f a i r c r a f t , engine and c o n t r o l s s p e c i a l i s t s conducted i n t e g r a t e d c o n t r o l design e f f o r t s aimed a t e s t a b l i s h i n g a c o n t r o l d e s i g n meth- odology. The Design Methods for I n t e g r a t e d C o n t r o l Systems (DMICS) was a dual-award e f f o r t ( r e f s . 10 and 1 1 ) . General Dynamics, P r a t t & Whitney A i r - c r a f t , Honeywell Systems Research Center, and Hami 1 ton-Standard c o n s t i t u t e d one team w h i l e Northrop Corporation, General E l e c t r i c A i r c r a f t Engine Group, and Systems C o n t r o l Technology formed t h e o t h e r . T w o design methodologies were produced, o n e involving a global approach and the o t h e r , a partitioned approach. Specific o u t p u t s of t h i s study included a comprehensive a i r c r a f t / propulsion/integrated control simulation, mathematical algorithms f o r t h e design of integrated control laws, and evaluation of t h e effectiveness of t h e integrated control design, and preliminary assessments of integrated control impact o n control architecture.

The DMICS program consisted of four phases as shown in f i g u r e 2. Phase I was directed a t the development of integrated control system d e s i g n require- ments. Phase I1 involved t h e development of a simulation t o be used a s a tool in t h e design of integrated control logic. Phase I11 consisted of t w o primary I tasks. T h e f i r s t involved t h e design of the integrated control logic and the second was an evaluation of how a n integrated flight-propulsion control system could b e effectively implemented. Phase IV involved the evaluation of the integrated control logic o n a simulation basis. The methodology developed under D M I C S has y e t t o be applied t o a n actual design case and demonstrated experimentally.

T h e NASA Ames/Dryden Highly Integrated Digital Electronic Control ( H I D E 0 program, a NASA sponsored program t o develop and f l ight demonstrate integrated flight propulsion control modes o n a McDonnell Douglas F-15 Eagle aircraft, T w o high-payoff integrated modes were developed (ref. 13).

began in 1983.

T h e Trajectory Control /Energy Management mode demonstrated not o n l y increased weapon system effectiveness through fuel savings a n d increased intercept ranges, but a l s o served as a stepping stone t o o t h e r control a p p l i c a t i o n s such a s terrain following-terrain avoidance and automated air combat. T h e Variable Operating Line mode demonstrated benefits of increased thrust without increas- T h e flight control a n d engine m o d i f i c a t i o n s m a d e ing e n g i n e size and weight.

t o implement these m o d e s will a l s o support f u t u r e NASA programs f o r o p t i m i z i n g flight propulsion control interactions.

M o s t integrated control done up t o t h i s point has involved o n l y special- ized purposes such as weapons control and in the up-and-away f l i g h t regime.

With the exception of DMICS, no generalized approach has been t a k e n in t h e design of integrated flight-propulsion control o n a global basis. Further, with the exception of t h e V / S T O L Controls Analysis program, virtually n o inte- grated control concepts have been applied o r developed for powered-lift air- craft. Powered-lift aircraft differ f r o m wing-borne f l i g h t o n l y in terminal o p e r a t l o n modes, that i s , short-takeoff, transition t o hover, hover, a n d verti- cal landing. Transition is generally without complication of mission require- ments o r duress. However, t h i s mode requires considerable c o o r d i n a t i o n and pilot integration and thus, high workload. Propulsion requirements in this flight phase can a l s o determine propulsion system size. From t h e s e considera- tions, t h e Supersonic S T O V L Integrated Flight-Propulsion Control P r o g r a m has The approach t o formulate t h e program is basically the continuation evolved.

and extension of the V / S T O L Propulsion Controls Analysis program using t h e integrated flight-propulsion controls methodologies developed under DMICS.

INTEGRATED CONTROL Phi l o s o p h i c a l Foundations Before launching i n t o a d i s c u s s i o n of i n t e g r a t e d c o n t r o l , perhaps a d e f i - n i t i o n o f the s u b j e c t would be i n o r d e r t o s e t t h e stage. The word " i n t e - g r a t e " i n i t s broadest form means t o form, coordinate, or blend i n t o a func- t i o n i n g or u n i f i e d whole. As a p p l i e d to the a i r c r a f t and p r o p u l s i o n i n d u s t r y , i n t e g r a t i o n has been used t o d e s c r i b e several f u n c t i o n s . For example, t h e process o f d e s i g n i n g p h y s i c a l i n t e r f a c e s between a i r f r a m e and engine has been r e f e r r e d t o as p r o p u l s i o n system i n t e g r a t i o n . The same i d e a has been a p p l i e d to c o n t r o l hardware where the p h y s i c a l r e l a t i o n s h i p between f u e l d e l i v e r y sys- tems, sensors, a c t u a t o r s and computational elements a r e considered i n an i n t e - g r a t e d manner t o f a c i l i t a t e e f f i c i e n t i n f o r m a t i o n exchange. I n t e g r a t i o n i n t h e same sense can a l s o occur i n f u n c t i o n a l c o n t r o l design, t h a t i s , t h e exchange and use o f i n f o r m a t i o n among computational elements t o e x p l o i t i n t e r - a c t i o n s between the subsystems b e i n g c o n t r o l l e d . I n t h i s regard, as i n d i c a t e d b r i e f l y i n the previous s e c t i o n , c o n t r o l i n t e g r a t i o n has taken p l a c e between f l i g h t , a v i o n i c s , weapons, and, t o a l i m i t e d degree, p r o p u l s i o n subsystems.

I n t e g r a t e d f l i g h t - p r o p u l s i o n c o n t r o l , then, as used w i t h i n the c o n t e x t o f t h i s i s d e f i n e d as t h e complete f u n c t i o n a l u n i f i c a t i o n o f i n f o r m a t i o n f l o w , paper, on a c o n t r o l law basis, between force and moment effectors o f t h e a i r c r a f t and p r o p u l s i o n subsystems t o e x p l o i t t h e i r i n t e r a c t i o n s for t o t a l system perform- ance improvement. Levels o f c o n t r o l system i n t e g r a t i o n a r e d e p i c t e d i n V/STOL system. On one end o f t h e spectrum f a l l s the f i g u r e 3 for a t y p i c a l use o f two separate systems and on the o t h e r end a combined computer system t h a t performs a1 1 f l i g h t and p r o p u l s i o n c o n t r o l f u n c t i o n s . The optimum proba- b l y l i e s somewhere i n between. There i s no general body o f c o n t r o l t h e o r y which can be a p p l i e d d i r e c t l y t o s o l v e t h i s problem so t h a t design methodolo- g i e s are necessary t o p e r m i t t h e a p p l i c a t i o n o f general t h e o r y .

I n l i k e manner, the n o t i o n of a s y s t e m should be i n v e s t i g a t e d . I f one asked d i v e r s e people what the word " s y s t e m " means, many d i v e r s e answers i n each o f t h e i r p a r t i c u l a r p r o f e s s i o n a l languages would r e s u l t . When compared and reduced, however, t h e n o t i o n common t o a l l o f them c o u l d p r o b a b l y be s t a t e d as ''a system i s something which accomplishes an o p e r a t i o n a l pr0cess.I' The sys- tem i s an o p e r a t i n g e n t i t y t h a t operates upon t h a t which I s c a l l e d i n p u t , to produce t h a t which i s c a l l e d o u t p u t . A system i s t h e r e f o r e a device, proce- dure, or scheme which behaves according t o some d e s c r i p t i o n , i t s f u n c t i o n b e i n g t o operate on i n f o r m a t i o n i n a time r e f e r e n c e t o y i e l d i n f o r m a t i o n . The t e r m " s y s t e m " emphasizes t h a t an o v e r a l l o p e r a t i o n a l process is under c o n s i d e r a t i o n r a t h e r than a c o l l e c t i o n o f pieces. This concept i s i m p e r a t i v e i n any study o f i n t e g r a t e d c o n t r o l methodology and i t i s o f utmost importance t o d e f i n e t h e f l i g h t - p r o p u l s i o n system.

The l a r g e degree of dynamic cross-coupling t h a t e x l s t s between t h e a i r - frame and p r o p u l s i o n subsystems for V/STOL a i r c r a f t p r o v i d e s t h e main impetus for i n t e g r a t i n g f l i g h t and p r o p u l s i o n c o n t r o l systems. I n p o w e r e d - l i f t a i r - c r a f t , t h e dynamics o f the p r o p u l s i o n system become as i m p o r t a n t as those o f t h e a i r c r a f t since f o r c e s and moments a r e generated d i r e c t l y or i n d i r e c t l y by t h e p r o p u l s i o n system on the airframe. An e f f e c t i v e i n t e g r a t i o n must o p t i m i z e t h e f a v o r a b l e i n t e r a c t i o n s to enhance a i r c r a f t m a n e u v e r a b i l i t y , f l i g h t p a t h c o n t r o l , and f a u l t t o l e r a n t systems design. The f a u l t t o l e r a n t design aspect i n v o l v e s the s u b s t i t u t i o n of secondary or s u b s i d i a r y c o n t r o l f u n c t i o n s t h a t can be used t o e f f e c t s a t i s f a c t o r y c o n t r o l w i t h o u t a prime f a i l u r e . For exam- c o u l d be e f f e c t e d w i t h aerody- p l e , i n a p r o p u l s i v e - l i f t concept, p i t c h c o n t r o l namic surfaces or f o r w a r d and a f t t h r u s t s p l i t between nozzles. This p r o v i d e s a l e v e l o f redundancy and, i f a f a i l u r e i n e i t h e r one occurs, the c o n t r o l func- t i o n would n o t be compromised, a t l e a s t n o t to a c a t a s t r o p h i c degree.

I n t e g r a t e d c o n t r o l imposes the s y s t e m s approach on t h e t r a d i t i o n a l prob- l e m o f separate f l i g h t and p r o p u l s i o n c o n t r o l by c o n s i d e r i n g the a i r c r a f t as With t h i s an o v e r a l l s y s t e m w i t h t h e a i r f r a m e and p r o p u l s i o n as subsystems.

i n essence, a h i g h l y s o p h i s t i c a t e d concept then, the p r o p u l s i o n system becomes, a c t u a t o r a c t i n g w i t h i n t h e framework of a f l i g h t c o n t r o l . C e r t a i n r e q u i r e - * ments a r e i m p l i e d i n t h i s approach, m o s t o f which center about the r e l i a b i l i t y o f the p r o p u l s i o n c o n t r o l s subsystem.

T r a d i t i o n a l l y , a i r c r a f t dynamicists tend t o use a s o p h i s t i c a t e d a i r f r a m e for the engine when ana- dynamic model i n c o n j u n c t i o n w i t h a rudimentary model l y z i n g t h e f l i g h t c o n t r o l s y s t e m since t h e engine i s considered t o have l i t t l e This i s t h e so-called b i g - a i r f r a m e , i n f l u e n c e i n the f l i g h t c o n t r o l design.

l i t t l e engine approach. On t h e o t h e r hand, p r o p u l s i o n system manufacturers have t r a d i t i o n a l l y used the o p p o s i t e approach. That i s , they use the b i g - engine, l i t t l e - o r - n o - a i r c r a f t a n a l y s i s approach. The a p p l i c a t i o n o f i n t e g r a t e d c o n t r o l methodology w i 11 r e q u i r e s i m u l a t i o n s o f comparable l e v e l s o f d e t a i 1 i n both t h e a i r f r a m e and propulsion system. I n t e g r a t e d c o n t r o l methodology demands an i n t e g r a t e d s i m u l a t i o n approach.

Operational Requirements V/STOL a i r c r a f t have unique o p e r a t i o n a l requirements ( r e f . 14) i n addi- t i o n t o those o f conventional a i r c r a f t . The p r o p u l s i o n requirements a r e sum- marized here from t h a t r e f e r e n c e as background t o t h i s paper. Among these requirements are the a b i l i t y t o t a k e o f f and c l i m b f r o m r e l a t i v e l y c o n f i n e d spaces, accomplish t r a n s i t i o n from aerodynamic l i f t t o p o w e r e d - l i f t and vice-versa, and t o hover p r e c i s e l y for p o s i t i o n i n g and l a n d i n g . C o n t r o l i n these modes a r e i n f l u e n c e d n o t o n l y by t y p i c a l low-speed i n s t a b i l i t i e s , b u t a r e complicated by f o r c e s and moments associated w i t h t h r u s t - i n d u c e d e f f e c t s , ground-effects, h o t gas i n g e s t i o n , and t h r u s t e f f e c t o r dynamics. P r o v i d i n g s u f f i c i e n t c o n t r o l power to compensate for the l a c k o f i n h e r e n t s t a b i l i t y and t o c o u n t e r a c t these v a r i o u s sources of disturbances u s u a l l y c r e a t e s a p e n a l t y because c o n t r o l power f o r low-speed o p e r a t i o n must, i n one form or another, be This c o n t r o l power can come a t consider- e x t r a c t e d from t h e p r o p u l s i o n system.

a b l e cost t o p r o p u l s i o n system performance and subsequently from a i r f r a m e weight which r e f l e c t s on o v e r a l l a i r c r a f t performance.

C o n t r o l A u t h o r i t y For each mode i n t h e f l i g h t spectrum o f p o w e r e d - l i f t a i r c r a f t , t h e force and moment a u t h o r i t y needed t o develop the r e q u i r e d a c c e l e r a t i o n s must be defined. I n hover, the e n t i r e c o n t r o l c a p a b i l i t y i s d e r i v e d from t h e p r o p u l - s i o n system, e i t h e r through d i r e c t t h r u s t o r bleed a i r from the engine compres- sor. This combined c o n t r o l i n p i t c h , r o l l , yaw and t r i m i s o f major concern t o the f l i g h t c o n t r o l designer since the combined requirement c o u l d be as h i g h as one-fourth o f the t h r u s t - t o - w e i g h t r a t i o needed t o simply hover and t h e r e f o r e penal i z e the a i r c r a f t ' s payload and range performance. I n f a c t , any t h r u s t h e l d i n reserve f o r c o n t r o l w i l l reduce m i s s i o n e f f e c t i v e n e s s and c o u l d .

even prevent t h e a i r c r a f t from proceeding beyond t h e design phase.

Other o p t i o n s may be considered as a means for a l l e v i a t i n g t h i s substan- t i a l demand on t h e p r o p u l s i o n system for c o n t r o l . These i n c l u d e u s i n g s h o r t t a k e o f f and p r i o r i t i z a t i o n o f c o n t r o l command f o r each o f the c o n t r o l axes.

I n the case o f the l a t t e r , t h i s means t h a t when t h e a i r c r a f t i s o p e r a t i n g below maximum t h r u s t , each i n d i v i d u a l c o n t r o l a x i s would have f u l l a u t h o r i t y . A t maximum t h r u s t w i t h more than one c o n t r o l demanding, a p r o p o r t i o n a l r e d u c t i o n i s appl l e d t o each a x i s depending on t h e c o n t r o l p r i o r i t y . A t t i tude c o n t r o l I systems which reduce bleed dependency or e l i m i n a t e i t completely should be o f any f u t u r e p o w e r e d - l i f t concept. This c o u l d be accomplished or a t t h e goal l e a s t a b e t t e d through use o f d i f f e r e n t i a l t h r u s t i n t h e primary and augmentor t h r u s t e f f e c t o r c o n t r o l . These e f f e c t o r s can i n c l u d e t h r u s t v e c t o r i n g - t h r u s t r e v e r s i n g , s p l i t d e f l e c t i n g , and v e n t r a l nozzles.

One concept t o e x p l o i t reduced bleed was developed i n the V/STOL C o n t r o l s A concise d e s c r i p t i o n and d i s c u s s i o n o f t h i s con- A n a l y s i s Program ( r e f . 15).

c e p t i s a l s o presented i n r e f e r e n c e 16. I n t h i s study, a b a s e l i n e p r o p u l s i o n s y s t e m was s e l e c t e d as shown i n f i g u r e 4. I t c o n s i s t e d o f a v a r i a b l e c y c l e engine (VCE) w i t h a remote augmented lift system (RALS). Nominal p r i m a r y and remote augmentor o p e r a t i o n produces 45 percent o f t o t a l engine t h r u s t i n the remote nozzle and the remaining 55 p e r c e n t i n t h e augmented d e f l e c t e d exhaust n o z z l e (ADEN). Primary and remote augmentor f u e l flow modulation produces a 212 p e r c e n t t h r u s t modulation c a p a b i l i t y i n each nozzle, which i s used i n con- I j u n c t i o n w i t h t h r u s t v e c t o r i n g for h e i g h t , p i t c h , and yaw c o n t r o l d u r i n g v e r t i c a l and low-speed f l i g h t o p e r a t i o n s . Only r o l l c o n t r o l i s p r o v i d e d by compressor bleed a i r which i s ducted t o w i n g - t i p p u f f e r j e t s .

F i g u r e 5 shows t y p i c a l steady-state t h r u s t capabi 1 i t i e s f o r t h e system.

Changes i n t o t a l t h r u s t demand a r e accommodated by p r i m a r y changes i n engine f u e l flow and rotor speeds which s l i d e the o p e r a t i n g box t o the l e f t along a c o n s t a n t t h r u s t s p l i t l i n e . Thrust s p l i t i s s e t by modulating the amount o f bypass d u c t a i r t o the remote system which s l i d e s the o p e r a t i n g box downward along a c o n s t a n t t o t a l t h r u s t l i n e . The i n d i v i d u a l p r i m a r y and remote t h r u s t l e v e l s a r e v a r i e d by t h e f l i g h t c o n t r o l i n response t o a t t i t u d e c o n t r o l correc- t i o n demands which t r a n s l a t e s t h e o p e r a t i n g p o i n t w i t h i n the o p e r a t i n g box.

T r a n s i t i o n from the v e r t i c a l f l i g h t regime t o h o r i z o n t a l f l i g h t i s accomplished i n a s i m i l a r f a s h i o n .

I n t r a n s i t i o n from wing-borne t o f u l l y propulsion-sustained f l i g h t , f l i g h t p a t h c o n t r o l i s u s u a l l y o b t a i n e d from d e f l e c t e d t h r u s t and a t t i t u d e p i t c h con- t r o l . I t i s i n t h i s f l i g h t regime t h a t the h i g h e s t i n t e r a c t i o n between a i r - frame and p r o p u l s i o n system occur. The degree o f c o o r d i n a t i o n between a x i a l a c c e l e r a t i o n and f l i g h t p a t h a u t h o r i t y determines how q u i c k l y t h e a i r c r a f t can t r a n s i t i o n f r o m wing-borne f l i g h t t o p o w e r e d - l i f t and reverse. A s i m p o r t a n t here, i s t h e use o f systems t o augment t h r u s t . The major impact on p r o p u l s i o n s y s t e m s i n t h i s f l i g h t regime i s the use of systems t o augment t h r u s t .

Augmen- t a t i o n s y s t e m s add system c o m p l e x i t y b u t p r o v i d e a1 t e r n a t e c o n t r o l f o r c e sources.

The low i n h e r e n t s t a t i c and dynamic s t a b i l i t y a t low airspeed, c o n t r o l cross-coupling, and s e n s i t i v i t y t o disturbances a r e a l l s i g n i f i c a n t i n f l u e n c e s on t h e p r e c i s i o n o f c o n t r o l t h a t t h e p i l o t can achieve and the e f f o r t t h a t must be devoted t o c o n t r o l undesired responses. D e f i c i e n c i e s i n the low-speed f l y i n g q u a l i t i e s o f V/STOL a i r c r a f t r e q u i r e the use o f the f l i g h t - c o n t r o l sys- tem t o improve the p r e c i s i o n o f c o n t r o l and reduce t h e e f f o r t the p i l o t must devote t o a i r c r a f t c o n t r o l d u r i n g hover and t r a n s i t i o n .

To accomplish these h i g h e r l e v e l s o f c o n t r o l augmentation on a V/STOL con- f i g u r a t i o n , i n t e g r a t i o n o f t h e f l i g h t and p r o p u l s i o n c o n t r o l system i s r e q u i r e d . This i n t e g r a t i o n c o u l d be implemented as simply as having servos Even i n d r i v e t h e power and t h r u s t v e c t o r l e v e r s w i t h i n the f l i g h t c o n t r o l .

t h i s case, t h e dynamic response c h a r a c t e r i s t i c s of p r o p u l s i o n system elements i n c l u d i n g i t s t h r u s t e f f e c t o r s must be considered i n t h e f l i g h t c o n t r o l design.

S i m i l a r l y , t h e f o r c e s and moments imposed on t h e a i r c r a f t by the p r o p u l s i o n system must be considered and the p r o p u l s i o n system t r e a t e d as a primary f l i g h t c o n t r o l element as t o r a t e s , response, accuracy, and r e 1 i a b i 1 i t y . To achieve t h i s l e v e l o f i n t e g r a t i o n , e s p e c i a l l y i n v i e w o f some o f the advanced V/STOL concepts, i t i s necessary t o conduct a more systematic study o f the i n t e g r a - t i o n o f the f l i g h t and p r o p u l s i o n systems and t o determine t o what e x t e n t i t i s b e n e f i c i a l . D i g i t a l c o n t r o l technology and modern c o n t r o l design t h e o r y coupled w i t h the c u r r e n t technology l e v e l of i n t e g r a t e d design methodologies make i t f e a s i b l e t o undertake such a design study.

SUPERSONIC STOVL INTEGRATED FLIGHT-PROPULSION CONTROL PROGRAM Over 25 years o f sporadic U . S . research and technology involvement i n powered-1 ift i n c l u d i n g VTOL, STOL, V/STOL, and now, STOVL, has generated sev- e r a l p r o p u l s i o n concepts. S o m e have been taken t o f l i g h t , w i t h some success- f u l and o t h e r s n o t . A l l c u r r e n t successful a i r c r a f t , however, a r e subsonic.

The o p p o r t u n i t y now e x i s t s t o i n v e s t i g a t e the i m p l i c a t i o n s o f supersonic f l i g h t on p o w e r e d - l i f t v e h i c l e s . Although the i n t e g r a t i o n o f f l i g h t and pro- p u l s i o n c o n t r o l s must e v e n t u a l l y be considered throughout t h e e n t i r e f l i g h t envelope o f t h e v e h i c l e , the p r i m a r y concern remains i n the subsonic f l i g h t phase and t e r m i n a l o p e r a t i o n s . C o n f i g u r i n g powered-1 i f t a i r c r a f t t o minimize induced lift and drag, which e f f e c t t h e f o r c e s and moments o f the a i r c r a f t , i s a l s o a p r i m a r y c o n s i d e r a t i o n . The major importance t o STOVL i n the supersonic regime, however, i s c o n f i g u r i n g the a i r c r a f t to accommodate the v a r i o u s p r o p u l - s l o n concepts f o r minimum drag.

There a r e c u r r e n t l y f i v e supersonic STOVL p r o p u l s i o n concepts being con- Four o f these concepts w i t h t y p i c a l a i r c r a f t con- s i d e r e d for STOVL a i r c r a f t .

f i g u r a t i o n s , shown i n f i g u r e 6, are: e j e c t o r augmentation, d e f l e c t e d or vectored t h r u s t , remote b u r n i n g augmented lift, and tandem f a n . The f i f t h i s t h e 1 i f t - p l u s - c r u i se concept. The goal o f the p r o p u l s i o n community i s to have the e n a b l i n g p r o p u l s i o n technologies i n p l a c e t o p e r m i t a low r i s k d e c i s i o n r e g a r d i n g the i n i t i a t i o n o f a research STOVL supersonic a t t a c k / f i g h t e r a i r - c r a f t i n the mid-1990's. This technology w i l l e f f e c t i v e l y i n t e g r a t e , enhance, and extend t h e supersonic c r u i s e , STOVL, and f i g h t e r l a t t a c k programs t o enable the U.S. i n d u s t r y t o develop a r e v o l u t i o n a r y supersonic s h o r t t a k e o f f / v e r t i c a l l a n d i n g f i g h t e r i a t t a c k a i r c r a f t i n t h e post-ATF p e r i o d . The b e n e f i t s i n c l u d e runway independence and basing f l e x i b i l i t y f o r a i r c r a f t w i t h h i g h s u r v i v a b i l - i t y and m a n e u v e r a b i l i t y . Since the successful development of a supersonic STOVL a i r c r a f t i s p r o p u l s i o n d r i v e n , p r o p u l s i o n technology issues a r e the key c r i t i c a l technologies r e q u i r e d t o achieve t h i s g o a l . W i t h i n these technology issues, i n t e g r a t e d f l i g h t - p r o p u l s i o n c o n t r o l s i s considered one of the ena- b l i n g technology which w i l l p e r m i t demonstration of t h e design c a p a b i l i t y t o p r o v i d e v i a b l e p o w e r e d - l i f t p r o p u l s i o n systems.

from f l i g h t c o n t r o l I n t e g r a t e d c o n t r o l technology d e r i v e s p r i m a r i l y requirements and o t h e r technology elements common t o advanced STOVL a i r c r a f t .

I .

A s discussed p r e v i o u s l y i n a r a t h e r condensed form, these i n c l u d e c o n t r o l force/moment generator performance, t h e i r e f f e c t on s t a b i 1 i t y and c o n t r o l , and i n t e g r a t e d f l i g h t - p r o p u l s i o n c o n t r o l design methodology. I t becomes necessary then, t o i n v e s t i g a t e these elements i n a program t h a t w i l l determine t h e i r to a i r c r a f t performance and t o a i r c r a f t h a n d l i n g q u a l i t i e s specif- r e l a t i o n s h i p i c a l l y . O b j e c t i v e s should i n c l u d e : ( 1 ) t h e e v a l u a t i o n o f c o n t r o l f o r c e and moment c a p a b i l i t y o f t h r u s t e f f e c t o r s which may be used i n STOVL p r o p u l s i o n c o n f i g u r a t i o n s , ( 2 ) t h e e v a l u a t i o n o f t h e s t a b i l i t y and c o n t r o l c h a r a c t e r i s t i c s u s i n g aerodynamic and a e r o p r o p u l s i o n p r e d i c t i o n s , and ( 3 ) t h e d e f i n i t i o n o f i n t e g r a t e d f l i g h t - p r o p u l s i o n c o n t r o l concepts. The second o b j e c t i v e i s w i t h i n t h e realm o f f l i g h t d y n a m i c i s t s . The f i r s t and t h i r d , however, r e q u i r e an i n t e r d i s c i p l i n a r y approach w i t h t h e r e s u l t s i n j e c t e d i n t o t h e second o b j e c t i v e .

i s a prime technology area then i t fol- I f i n t e g r a t e d f l i g h t - p r o p u l s i o n c o n t r o l lows t h a t an i n t e g r a t e d program approach i s necessary.

On the b a s i s of t h e f l i g h t c o n t r o l technology requirements and t h e s t r e n g t h o f t h e V/STOL C o n t r o l s A n a l y s i s and DMICS programs, a j o i n t NASA Lewis and Ames c o n t r o l s program f o r supersonic STOVL a i r c r a f t was developed t o generate t h e r e q u i r e d i n t e g r a t e d c o n t r o l technology and t o v a l i d a t e i t s effec- t i v e n e s s . The o v e r a l l o b j e c t i v e o f the NASA Supersonic STOVL I n t e g r a t e d F l i g h t - P r o p u l s i o n C o n t r o l Program i s t o d e f i n e and develop i n t e g r a t e d c o n t r o l technology for a c h i e v i n g supersonic STOVL f l i g h t - p r o p u l s l o n c o n t r o l s i n t e g r a - tion: ( 1 ) t o enable c o n t r o l l e d t r a n s i t i o n from t a k e o f f t o f o r w a r d f l i g h t t o hover w i t h reduced p i l o t workload, ( 2 ) t o enhance a i r c r a f t h a n d l i n g q u a l i t i e s through p r o p u l s i o n c o n t r o l , ( 3 ) t o extend c o n t r o l l o g i c across t h e t o t a l f l i g h t environment, ( 4 ) t o assess unique supersonic STOVL o p e r a t i n g requirements, and (5) t o r e f i n e p r o p u l s i o n s y s t e m and c o n t r o l modeling f o r p i l o t e d s i m u l a t i o n .

The approach w i 11 use c o o p e r a t i v e design, s i m u l a t i o n , and experimental f a c i l i t i e s o f a i r c r a f t and p r o p u l s i o n centers t o j o i n t l y develop, e v a l u a t e , and v a l i d a t e supersonic STOVL i n t e g r a t e d f l i g h t - p r o p u l s i o n concepts. Elements o f t h i s program approach i n c l u d e : ( 1 ) a n a l y t i c a l modeling o f non r e a l t i m e and r e a l t i m e models of supersonic a i r c r a f t (NASA Ames) and p r o p u l s i o n systems (NASA Lewis) for c o n t r o l s a n a l y s i s and p i l o t e d s i m u l a t i o n , ( 2 ) i d e n t i f i c a t i o n o f i n t e g r a t e d c o n t r o l design approaches and concepts by appl i c a t i o n o f advanced and modern c o n t r o l methods and t h e o r i e s , ( 3 ) performance e v a l u a t i o n s o f con- t r o l system concepts u s i n g p i l o t e d s i m u l a t i o n on t h e NASA Ames V e r t i c a l Motion S i m u l a t o r (VMS) and experimental system e v a l u a t i o n s on t h e NASA Lewis Powered L i f t F a c i l i t y (PLF) i n c l u d i n g a i r c r a f t s i m u l a t i o n s t o v e r i f y a n a l y s i s , and ( 4 ) use of planned supersonic STOVL c o n t r o l e f f e c t o r component/engine i n t e g r a t i o n t e s t s on t h e PLF t o determine t h e i r t r a n s i e n t e f f e c t s on a i r c r a f t f o r c e and moments and t o improve modeling and c o n t r o l concept f i d e l i t y . Also i n c l u d e d i s p r o p u l s i o n support f o r f l i g h t e v a l u a t i o n .

Specific E emen t s S p e c i f i c elements of t h e program a r e shown o n f i g u r e 7. T h e s e are: ( 1 ) Control Effector Dynamics, ( 2 ) Integrated Flight-Propulsion Control Concepts, and (3) Integrated C o n t r o l s Methodology. A n additional planned e l e m e n t is Flight P r o g r a m Propulsion Control S u p p o r t A brief discussion of each element fol lows.

Control Effector Dynamics T h e Controls Effector D y n a m i c s element Is basica ly an in-house program t o determine the transient and dynamic performance of thrust effectors unique t o STOVL. These effectors include e j e c t o r augmentors remote and f a n f l o w burners, and vectoring, reversing and ventral nozzles. Associated flow switch- ing valves and bleed-flow extraction a r e a l s o of interest and a r e being obtained in j o i n t efforts with the A i r Force. Propulsion induced effects cre- ated by t h e s e thrust effectors have a primary impact o n aircraft stability and control and f o r m a n important link t o integrated control design. O b j e c t i v e s include the definition of ( 1 ) f o r c e / m o m e n t envelopes in takeoff, t r a n s i t i o n and hover modes, (2) thrust modulation/deflection capability, and (3) reaction control demand effects o n bleed requirements and engine performance. T h e approach i s to f i r s t determine which d a t a a r e available t o d e f i n e t h e effector performance and then t o execute tests i f necessary. D a t a such a s s t a r t u p tran- sients, modulation a b i l i t y and range, f l o w deflection a b i l i t y and f r e q u e n c y response will be sought. T h e primary product of t h e s e investigations will be verified simulation models which can be used in systems and c o n t r o l s a n a l y s e s and overall systems evaluations. T h e f o r c e s and moments produced f r o m the effectors and their propulsion induced effects o n t h e aircraft will be deter- mined in wind tunnel programs.

Thus f a r , a simulation modeling effort has been initiated and a transient performance test o n a full s c a l e e j e c t o r planned. The test is part of the U.S.-Canada Focused Ejector program which has been on-going f o r the last f e w years. A more complete description of that program will be presented later.

Concern with ejector augmentation f r o m a controls viewpoint lies primarily with its start-up transient characteristics and its ability t o deflect o r vec- tor thrust.

A n investigation i n t o t h e remote burner augmentation c o n c e p t is c u r r e n t l y At this point it a p p e a r s that transient characteristics a r e suffici- underway.

The major unknown in t h i s augmentor concept is its propulsion ently defined.

induced effects o n t h e aircraft which must be determined t o e v a l u a t e its effects on the transition envelope and stabi 1 i t y requirements before real i stic integrated control studies can proceed.

Integrated Flight-Propulsion Control Concepts The issues involved in this element revolve about the t e c h n o l o g y valida- tion of Integrated control concepts while stressing the generic a s p e c t s of its In the validation issue, advantage m u s t be taken of existing tech- technology.

nology programs while applying current methodologies such a s DMICS in t h e con- trols discipline with the goal of extending and validating integrated control 1 0 technology. The g e n e r i c issues i n c l u d e system c o m p l e x i t y and design methodol- I t i s t h i s l a s t i s s u e which i s of most importance t o t h e program element.

ogy.

t o take advantage o f concepts o f The approach t o s a t i s f y i n g these issues was o p p o r t u n i t y by c o n s i d e r i n g e x i s t i n g databases, s t a t u s o f s i m u l a t i o n s , p r o p u l - s i o n system a v a i l a b i l i t y , e x i s t i n g experimental programs, o v e r a l l system com- p l e x i t y , and the a p p l i c a t i o n t o a p o s s i b l e f l i g h t program. The U.S.-Canada Focused E j e c t o r program p r o v i d e s one concept o f o p p o r t u n i t y . I t should be stressed here t h a t t h e augmented e j e c t o r p r o p u l s i o n concept may n o t be t h e con- c e p t of choice f o r f u r t h e r s p e c f f i c development and t h a t i t i s being used o n l y as a means t o accomplish an i n t e g r a t e d c o n t r o l s a p p l i c a t i o n . I n f a c t , any par- t i c u l a r concept has o n l y a minor e f f e c t on the development o f i n t e g r a t e d con- . trols. Since c o n t r o l s a r e h i s t o r i c a l l y s y s t e m s o r i e n t e d , issues such as system complexity, m u l t i v a r i a b l e and i n t e r a c t i v e c h a r a c t e r , design methodology and broadness o f methodology appl i c a b i 1 i t y a r e t h e major i t e m s o f i n t e r e s t and the e j e c t o r augmentor concept m e e t s these c r i t e r i a .

The U.S.-Canadian Focused E j e c t o r Program i s an on-going program between these governments to v a l i d a t e t h e technology and e v a l u a t e a v i a b l e e j e c t o r - augmented powered-1 ift p r o p u l s i o n system f o r supersonic STOVL a i r c r a f t a t f u l l - s c a l e . The program i n v o l v e s DeHavi 1 land, General Dynamics and General E l e c t r i c as c o n t r a c t o r s . Prior research has shown t h a t adequate e j e c t o r t h r u s t performance can be achieved b u t t h a t e f f i c i e n t movement o f p r i m a r y a i r f r o m the engine t o t h e e j e c t o r i s a b s o l u t e l y necessary f o r concept success.

From a p r o p u l s i o n v i e w p o i n t , t h e approach used i n t h e program i s t o design, f a b r i c a t e , t e s t and e v a l u a t e a fan a i r c o l l e c t o r , v a l v i n g , d u c t i n g , and e j e c - tor s y s t e m which meets t h e performance requirements of an e j e c t o r augmented supersonic STOVL a i r c r a f t u s i n g t h e l a t e s t analyses and experimental r e s u l t s from component t e s t s . Large-scale experimental e v a l u a t i o n s i n v o l v e , s p e c i f i - c a l l y , t h e General Dynamics E-7D a i r c r a f t design and a General E l e c t r i c F l l O engine w i t h DeHavilland e j e c t o r s . The l a r g e - s c a l e a i r c r a f t model and p r o p u l - s i o n system w i l l be evaluated on the NASA Lewis Powered L i f t F a c l l i t y (PLF) and the NASA Ames 40x80 wind t u n n e l . The program forms a unique research capa- b i l i t y on which t o conduct i n t e g r a t e d c o n t r o l s research.

The I n t e g r a t e d C o n t r o l s Research Demonstrator becomes, then, an i n t e - g r a t e d a d j u n c t t o the on-going program t o the e x t e n t t h a t i t does n o t d u p l i - c a t e common e f f o r t s . I t s o b j e c t i s to develop and v a l i d a t e t h e a p p l i c a t i o n o f an i n t e g r a t e d fl i g h t - p r o p u l s i o n c o n t r o l design methodology. The program i s d e p i c t e d i n f i g u r e 8. Using a i r c r a f t model data, a s i m u l a t i o n o f t h e a i r c r a f t and p r o p u l s i o n system w i l l be generated f o r use i n i n t e g r a t e d c o n t r o l s analy- s i s and e v a l u a t i o n . The a i r c r a f t model and p r o p u l s i o n system hardware i n c l u d - i n g c o n t r o l s w i l l be mounted on t h e NASA Lewis PLF. A l r c r a f t dynamics and t h e f l i g h t c o n t r o l segment o f t h e i n t e g r a t e d c o n t r o l w i l l be s i m u l a t e d on t h e NASA Lewis C o n t r o l s and S i m u l a t i o n Laboratory which c o n s i s t s o f two A p p l i e d Dynam- i c s I n t e r n a t i o n a l (AD11 System 100 d i g i t a l computers. System e v a l u a t i o n w i l l be accomplished by u s i n g a s i m u l a t i o n o f a human p i l o t t o f l y t h e a i r c r a f t through p r e s c r i b e d f l i g h t e x e r c i s e s . Subsequent t o t h i s experimental program, a f i n a l phase o f e v a l u a t i o n w i l l i n c l u d e the t e s t i n g of t h e E-7D on a s t a t i c t e s t stand and the 40- by 80-Foot Wind Tunnel a t NASA Ames and an i n t e g r a t e d c o n t r o l e v a l u a t i o n for h a n d l i n g q u a l i t i e s on t h e NASA Ames V e r t i c a l Motion Simulator ( V M S ) .

Another program w i t h i n the i n t e g r a t e d f l i g h t - p r o p u l s i o n c o n t r o l concept element, as shown on f i g u r e 9, i s a DMICS-type design a p p l i c a t i o n t o a 1 1 vectored thrust configured aircraft. T h e objectives here a r e t o not o n l y reveal integrated control related problems, but t o provide a n a l t e r n a t i v e con- cept f o r integrated flight-propulsion control design methodology validation and subsequently determine i f t h e design methodology is configuration depend- ent. The program consists of a definition of system requirements, simulation development, generation o f integrated control laws for a hybrid vectored thrust configuration including fault tolerance logic, and a piloted flight sim- ulation evaluation. T h e program may eventually be extended t o include advanced control hardware with bench test and a n iron-bird experimental e v a l u a t i o n in a collaborative program with the A i r Force.

I Integrated Control Methodology T h e Integrated Control Methodology element is a n in-house program t o establ ish and investigate, both analytical ly and experimentally, a l t e r n a t e integrated flight-propulsion control design methodologies. In DMICS, t w o design approaches were taken In the dual-award effort, o n e by each of t h e t w o teams o n separate system designs. T h e f i r s t was a global approach wherein all input-output relationships were defined f r o m an integrated linear system. T h e integrated control was synthesized using a reduced-order linear model by applying a Linear-Quadratic-Gaussian (LQG) Loop Transfer Recovery (LTR) tech- nique in a centralized approach. The o t h e r study used a hierarchical decen- tralized LQG approach with multi-objective optimization. A basic philosophy of t h i s design approach is that subsystem partitioning is not assumed prior t o analysis but is a n o u t p u t of the design process. T h e design starts o u t a s a centralized process in a high-level design and the results used t o establish a decentralized control design followed by overall system optimization. T h e decentralized system reduces t h e control complexity by distributing control authority t o local controllers which attempt t o m e e t o n l y part of t h e overall performance requirements.

Although both methodologies resulted in a kind of design manual f o r inte- grated control, it is still undetermined i f a different methodology applied t o t h e same operational system would produce the same, different o r better results. A n effort t o examine a l t e r n a t e methodologies o n t h e same system would a p p e a r in order. While o n e of t h e o b j e c t s in the Integrated Flight-Propulsion Concept element described earlier is t h e application and evaluation of a DMICS-type design methodology t o different propulsion concepts, t h e o b j e c t of the Integrated Control Methodology element is t o e x a m i n e a l t e r n a t i v e d e s i g n methodologies on the same system. Current alternatives f o r integrated control design methodology include: ( 1 1 a centralized multi-objective o p t i m i z a t i o n technique, and ( 2 ) an optimized introduction of cross-feeds process. Concep- tual f l o w paths f o r these processes a r e shown i n f i g u r e 10. These a l t e r n a t i v e processes f l o w f r o m common sense permutations of t h e D M I C S methodologies. For example, t h e first alternative combines the centralized approach of t h e D M I C S global methodology with the partitioned feature of the o t h e r D M I C S d e s i g n process.

In the execution of t h i s research element, design methodologies will be applied t o the ejector augmented configuration used in t h e previously described research demonstrator program. An integrated control wi 1 1 be designed and evaluated experimentally in the same manner as in that element e x c e p t that a pilot station with real pilots may be used in a ground-based preliminary e v a l u a t i o n p r i o r t o a moving-base p i l o t e d s i m u l a t i o n e v a l u a t i o n on t h e NASA Ames VMS. I n a d d i t i o n , t h e o p p o r t u n i t y w i l l be taken t o a p p l y advanced f a u l t t o l e r a n t concepts.

CONCLUDING REMARKS The p r i m a r y problem i n developing p r o p u l s i o n s y s t e m concepts i s t o design systems which p r o v i d e t h e r e q u i r e d a i r c r a f t h a n d l i n g q u a l i t i e s i n p o w e r e d - l i f t modes w i t h o u t r o b b i n g t h e powerplant of i t s a b i l i t y t o perform s a f e l y and eco- n o m i c a l l y . During low speed o p e r a t i o n s V/STOL a i r c r a f t a r e n o t o n l y dependent * upon i t s p r o p u l s i o n system for lift, b u t a l s o for t h e f o r c e s and moments needed f o r f l i g h t p a t h and a t t i t u d e c o n t r o l . Thus, h i g h l y c o o r d i n a t e d f l i g h t and pro- systems a r e c r i t i c a l t o t h e success o f these advanced V/STOL p u l s i o n c o n t r o l a i r c r a f t .

The l a r g e degree of dynamic cross-coupling t h a t e x i s t s between t h e a i r - for V/STOL a i r c r a f t p r o v i d e s the main impetus frame and p r o p u l s i o n subsystems for i n t e g r a t i n g f l i g h t and p r o p u l s i o n c o n t r o l s y s t e m s . I n p o w e r e d - l i f t a i r - c r a f t , t h e dynamics of the p r o p u l s i o n system become as i m p o r t a n t as those o f t h e a i r c r a f t s i n c e forces and moments a r e generated d i r e c t l y or i n d i r e c t l y by t h e p r o p u l s i o n system on the airframe. C o n t r o l a u t h o r i t y requirements p l a c e s i g n i f i c a n t demands on t h e p r o p u l s i o n system. An e f f e c t i v e i n t e g r a t i o n must o p t i m i z e t h e f a v o r a b l e i n t e r a c t i o n s t o enhance a i r c r a f t maneuverabi 1 i t y and f l i g h t p a t h c o n t r o l . The p o t e n t i a l payoff i n m i s s i o n payload w i t h o u t t h e sac- r i f i c e o f c o n t r o l a u t h o r i t y or p r o p u l s i o n system r e l i a b i l i t y i s worth i nvest i g a t i ng .

To achieve t h i s l e v e l o f i n t e g r a t i o n , e s p e c i a l l y i n view o f some o f t h e advanced V/STOL concepts, i t i s necessary t o conduct a more systematic study o f t h e i n t e g r a t i o n of the f l i g h t and p r o p u l s i o n systems and t o determine t o what e x t e n t i t i s b e n e f i c i a l . D i g i t a l c o n t r o l technology and modern c o n t r o l design t h e o r y coupled w i t h the c u r r e n t technology l e v e l of i n t e g r a t e d design methodologies make i t f e a s i b l e t o undertake such a design study.

On t h e b a s i s o f t h e f l i g h t c o n t r o l technology requirements and t h e s t r e n g t h o f p r e v i o u s programs, a j o i n t NASA Lewis and Ames c o n t r o l s program f o r supersonic STOVL a i r c r a f t has been developed t o generate the r e q u i r e d i n t e - g r a t e d c o n t r o l technology and t o Val i d a t e i t s e f f e c t i v e n e s s . The o v e r a l l o b j e c t i v e o f the NASA Supersonic STOVL I n t e g r a t e d F1 ight-Propul s i o n C o n t r o l Program i s t o d e f i n e and develop i n t e g r a t e d c o n t r o l technology for a c h i e v i n g supersonic STOVL f 1 i ght-propul s i o n c o n t r o l s i n t e g r a t i o n .

ACKNOWLEDGMENTS The author wishes t o express h i s a p p r e c i a t i o n t o D r . James A. F r a n k l i n , NASA Ames Research Center, for h i s c o n t r i b u t i o n s t o t h e f l i g h t requirements s e c t i o n o f t h i s paper, and t o D r . Bruce Lehtinen, NASA Lewis Research Center, f o r h i s c o n t r i b u t i o n and comments on a l t e r n a t i v e i n t e g r a t e d c o n t r o l methodologies.

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10. W.B. K e r r , S.P. Roth, R.J. M i l l e r , and R.E. Creekmore, V/STOL P r o p u l s i o n Control A n a l y s i s - Phase I1 F i n a l Report," NASA CR-165522, 1981.

i

11. K.L. Smlth, W.B. K e r r , and G.L. Hartmann, "Design Methods for I n t e g r a t e d C o n t r o l Sys tems , I' AFWAL-TR-84-2088 , Apr . 1984.

12. D.S. J o s h i , P.D. Shaw, S.M.,, Rock, and W.S.C. F i s k , "Design Methods for I n t e g r a t e d C o n t r o l Systems," AFWAL-TR-84-2037, Feb. 1985.

13. W.A. Yonke, " I n t e g r a t e d F l i g h t / P r o p u l s i o n C o n t r o l : HIDEC Modes," NAECON 1984, Vol. 1, I E E E , New York, 1984, pp. 472-478.

14. J.A. F r a n k l i n , " C o n t r o l of V/STOL A i r c r a f t , " A e r o n a u t i c a l J o u r n a l , Vol. 90, May 1986, pp. 157-173.

15. "V/STOL P r o p u l s i o n C o n t r o l A n a l y s i s - Phase I F i n a l Report, 'I NASA CR-165207, 1 980.

16. H. Brown, "V/STOL P r o p u l s i o n C o n t r o l Technology," Journal o f Guidance, Con- t r o l , and Dynamics, Vol. 7, Mar.-Apr. 1984, pp. 183-189.

FIGURE 1, - INTEGRATED V/STOL FLIGHT/PROPULSION CONTROL TECHNOLOGY DEVELOPMENT PLAN.

SYSTEM REQUIREMENTS 0 MISSION ANALYSIS TECHNOLOGY ASSESSMENT PRELIMINARY CONTROL STRUCTURE PERFORMANCE I I ICItHI lVL \\ CONTROL DESIGN I I / ..r...-., CONTROL LAW EVALUATION 0 EVALUATION CRITERIA 0 D I G I T A L EVALUATIONS 0 PILOTED FLIGHT SIMULATION

DESIGN METHODS FOR INTEGRATED CONTROL v SYSTEMS

FIGURE 2. - DMICS PROGRAM PHASES.

I F. 4 FIGURE 3. - LEVELS O F V/STOL CONTROL SYSTEM INTEGRATION.

CORE DRIVEN 3RD STAGE FAN

y REMOTE AUGMENTOR

f-

\ /

v_ FORWARD VABl

OVERSIZE FAN FIGURE 4 . - VCE/RALS BASELINE ENGINE.

C o n s t a n t T o t a l

,/ 5 0 ' 5 / 5 , 5 5 /cc n s t n n t

T h r u s t L i l t T h r u s t Max. Fan Sueell 4"1(*0 S p l i t I I I 1 I I 1 0 1 2 1 4 1 6 0 2 4 6 8 ADEN T h r u s t x FIGURE 5. - RALS THRUST MODULATION VTOL MODE.

ORIGINAL PAGE I S OF POOR QUALITY EJECTOR SYSTEM DEFLECTED THRUST SYSTEM FIGURE 6. - SUPERSONIC V/STOL PROPULSION SYSTEMS.

REMOTE AUGMENTED L I F T SYSTEM TANDEM FAN SYSTEM FIGURE 6. - CONCLUDED.

. r , FISCAL YEAR ELEMENT CONTROL EFFECTOR DYNAMICS (LERC) EJECTOR, BLEED, RALS, PCB INTEGRATED FL IGHT-PROPULSION CONTROL CONCEPTS (LERCIARC)

TECHNOLOGY 1

AUGMENTED EJECTOR (GE) DEVEL P E N T VECTORED THRUST (PWA) REMOTE L I F T (GE/USAF) INTEGRATED CONTROLS METHODOLOGY ( LERC ) SIMULATION EVALUATION ( LERC) CONTROLS RESEARCH DEMONSTRATOR (LERC PLF) DEMONSTRATION WIND TUNNEL EVALUATION (ARC 40x80) PILOTED SIMULATION EVALUATION (ARC VMS) FLIGHT TEST DEMONSTRATION

- I 111 111111 1 1 1 1 1 1 11 1 1

FIGURE 7. - ADVANCED SUPERSONIC STOVL CONTROLS PROGRAM.

, ENGINE SYSTEM/CONTROLS AMES 40x80 FT WIND TUNNEL MATHEMATICAL MODEL I NG

\

J ; : ; ) D Y N A M I C PILOTED SIMULATION AIRCRAFT - NASA AMES VERTICAL MOTION SIMULATOR NASA AMES PROPULSION - NASA LEWIS FIGURE 8. - INTEGRATED CONTROLS RESEARCH DEMONSTRATOR PROGRAM.

MATHEMATICAL MODELING PILOTED SIMULATION AIRCRAFT - NASA AMES VERTICAL MOTION SIMULATOR NASA AMES PROPULSION - NASA LEWIS FIGURE 9. - STOVL INTEGRATED CONTROL CONCEPT RESEARCH.

ORIGINAL P W E IS OF FOQR QUALITY

c w

f

Report Documentation Page NaIicmaI Aeronautics and 2. Government Accession No. 3. Recipient's Catalog No.

1. Report No.

NASA TM-100226 5. Report Date Flight Propulsion Control Integration for V/STOL Aircraft 6. Performing Organization Code 8. Performing Organization Report No.

7. Author@) E-3845 James R. Mihaloew 10. Work Unit No.

505-62-71 9. Performing Organization Name and Address 11. Contract or Grant No.

National Aeronautics and Space Administration Lewis Research Center Cleveland, Ohio 44135-3191 13. Type of Report and Period Covered 12. Sponsoring Agency Name and Address Technical Memorandum National Aeronautics and Space Administration 14. Sponsoring Agency Code Washington, D.C. 20546-0001 15. Supplementary Notes Prepared for the International Powered Lift Conference sponsored by the Society of Automotive Engineers, Santa Clara, California, December 7-10, 1987.

16. Abstract The goal of the propulsion community is to have the enabling propulsion technolo- gies in place to permit a low-risk decision regarding the initiation of a research STOVL supersonic attack/fighter aircraft in the mid-1990's. This tech- nology will effectively integrate, enhance, and extend the supersonic cruise, STOVL, and fighter/attack programs to enable U . S . industry to develop a revolu- tionary supersonic short takeoff/vertical landing fighter/attack aircraft in the The rationale, methods, and criteria used in developing a post-ATF period.

to develop the technology ele- joint NASA Lewis and NASA Ames research program ment for integrated flight-propulsion control through integrated methodologies is presented. This program, the Supersonic STOVL Integrated Flight-Propulsion Controls Program, is part of the overall NASA Lewis Supersonic STOVL integrated approach to an integrated program to achieve integrated flight-propulsion con- trol technology.

18. Distribution Statement 17. Key Words (Suggested by Author@))

Unclassified - Unlimited

Controls 19. Security Classif. (of this report) 20. Security Classif. (of this page) 21. No of pages 22. Price' 21 A02 Unclassified Unclassified