254
-E F F -E C T S OF V I S U A L AND V -E S T I B U L A R MOTION P -E R C -E P T I O N ON CONTROL T A S K P E R F O R M A N C E R . J . A . W . H o s m a n * ) J . C . v a n d e r V a a r t * ) A b s t r a c t T h e i n f l u e n c e o f v i s u a l a n d v e s t i b u l a r m o t i o n p e r c e p t i o n o n p i l o t ' s b e h a v i o u r i n a c o n t r o l t a s k h a s a r o u s e d m a n y d i s c u s s i o n s d u r i n g t h e l a s t d e c a d e s w h i c h h a v e n o t y e t come t o a n e n d . T h i s i n f l u e n c e i s o f d i r e c t r e l e v a n c e t o t h e m o d e l l i n g o f p i l o t c o n t r o l b e h a v i o u r a n d t o f l i g h t s i m u l a -t i o n . R e s u l t s o f e x p e r i m e n t s i n t h i s f i e l d a s r e p o r t e d i n t h e l i t e r a t u r e a p p e a r e d t o b e s o m e w h a t d i f f e r e n t f r o m t h e e x p e r i e n c e g a i n e d i n t h e r e s e a r c h f l i g h t s i m u l a t o r o f t h e D e p a r t m e n t o f A e r o s p a c e E n g i n e e r i n g o f t h e D e l f t U n i v e r s i t y o f T e c h n o l o g y . T h e a i m o f t h e e x p e r i m e n t d e s c r i b e d i n t h e p r e s e n t P a p e r w a s t o o b t a i n a d a t a b a s e o n p i l o t ' s b e h a v i o u r u s i n g c e n t r a l a n d p e r i p h e r a l v i s u a l a n d m o t i o n c u e s . I n a f o l l o w i n g t a s k ( o r c o m p e n s a t o r y t r a c k i n g t a s k ) a n d i n a d i s t u r b a n c e t a s k ( b o t h r o l l t a s k s ) u s i n g a d o u b l e i n t e g r a t o r a s t h e c o n t r o l l e d e l e m e n t , a l l p o s s i b l e c o m b i n a t i o n s o f c e n t r a l v i s u a l , p e r i p h e r a l v i s u a l a n d v e s t i -b u l a r m o t i o n c u e s w e r e p r e s e n t e d t o t h e s u -b j e c t s . T h e r e s u l t s s h o w s i g n i f i c a n t i n f l u e n c e o f t h e p e r i p h e r a l v i s u a l a n d v e s t i -b u l a r c u e s o n s u -b j e c t ' s p e r f o r m a n c e a n d d y n a m i c -b e h a v i o u r i n -b o t h c o n t r o l t a s k s . 1 . I N T R O D U C T I O N T h e o r i e s o f c o n t r o l b e h a v i o u r o f a p i l o t o r a h u m a n c o n t r o l l e r a r e g e n e r a l l y b a s e d o n t h e c o n c e p t o f a c o n t r o l l e r a s a p r o c e s s o r o f i n f o r m a t i o n . I n t h e s e t h e o r i e s a s w e l l a s i n q u i t e a n u m b e r o f m a t h e m a t i c a l m o d e l s o f h u m a n c o n t r o l b e h a v i o u r t h r e e m a i n f e a t u r e s a r e u s u a l l y d i s t i n g u i s h e d : o b s e r v a -t i o n , d e c i s i o n m a k i n g a n d o u -t p u -t g e n e r a -t i o n . T h e p e r c e p t i o n o f p o s i t i o n a n d m o t i o n b y w a y o f v i s u a l , v e s t i b u l a r , t a c t i l e a n d p r o p r i o c e p t i v e c u e s c a n be c o n s i d e r e d a s a f i r s t s t a g e i n t h e o b s e r v a -t i o n p r o c e s s . R e s e a r c h i n -t h e f i e l d o f c o n -t r o l b e h a v i o u r a -t -t h e A e r o s p a c e D e p a r t m e n t o f D e l f t U n i v e r s i t y i s m a i n l y c o n c e r n e d w i t h m o t i o n p e r c e p t i o n . A n e x a m p l e o f e a r l i e r w o r k a r e t h e e x p e r i m e n t s ( r e p o r t e d i n R e f . 1) o n v e s t i b u l a r t h r e s h o l d s o f m o t i o n p e r c e p t i o n . I n t h e s e t e s t s , s u b j e c t s w e r e p a s s i v e a n d w e r e o n l y r e q u i r e d t o g i v e v e r b a l r e s p o n s e s t o s e l e c t e d m o t i o n s t i m u l i i n a t y p i c a l f l i g h t d e c k s i t u a t i o n . Of c o u r s e m o t i o n p e r c e p t i o n b y a p i l o t i n a s i t u a t i o n w h e r e h e a c t i v e l y c o n t r o l s a n a e r o p l a n e i s q u i t e d i f f e r e n t f r o m t h a t o f a p a s s i v e o b s e r v e r . T h e w o r k r e p o r t e d i n t h e p r e s e n t P a p e r w a s u n d e r t a k e n t o g a t h e r m o r e i n s i g h t i n t o t h e m o t i o n p e r c e p t i o n i n a c o n t r o l s i t u a t i o n . I n t h i s a r e a e s p e c i a l l y t h e r e i s a c o n s i d e r a b l e l a c k o f k n o w l e d g e . V e r y l i t t l e i s k n o w n i n f a c t , a b o u t e x a c t l y w h a t a r e t h e m o s t v i t a l s e n s e s f o r a n a i r c r a f t c o n t r o l t a s k a n d o n h o w t h e i n f o r m a t i o n p r o c e s s i n g t a k e s p l a c e s . * ) D e l f t U n i v e r s i t y o f T e c h n o l o g y , D e p a r t m e n t o f A e r o s p a c e E n g i n e e r i n g .Knowledge of a l l thèse aspects i s e s s e n t i a l f o r formulâting the mathematlcal models that are not only to be t o o l s f o r a l r c r a f t development but a l s o f o r m o t i o n s i m u l a t i o n .
I t i s c o n c e i v a b l e t h a t much of the présent m o t i o n v e r s u s non-motion c o n t r o v e r s y i n the f i e l d of f l i g h t s i m u l a t i o n p a r t l y S p r i n g s from a gênerai l a c k of knowledge about the rôle of m o t i o n p e r c e p t i o n i n the c o n t r o l of a l r -c r a f t .
I t i s o b v i o u s t h a t t h e r e i s a c e r t a i n degree of o v e r l a p p i n g (redundancy) i n s e n s o r y i n f o r m a t i o n . Furthermore i t i s c l e a r t h a t the amount and q u a l i t y o f s e n s o r y i n f o r m a t i o n needed dépend on the nature and d i f f i c u l t y of the c o n t r o l t a s k , a l t h o u g h q u a n t i t a t i v e d a t a a r e a g a i n e i t h e r s c a r c e or l a c k i n g a l t o g e t h e r .
An i d e a l t o o l i n the quest f o r answers to the q u e s t i o n s posed above i s a m o d e m moving base f l i g h t S i m u l a t o r i n which i t i s p o s s i b l e t o s i m u l a t e a wide v a r i e t y of System c h a r a c t e r i s t i c s , to d e l e t e or a l t e r différent s e n s o r y eues and to v a r y s y s t e m a t i c a l l y the n a t u r e and d i f f i c u l t y o f a c o n t r o l t a s k . I n t h i s way the i n f o r m a t i o n p r o c e s s i n g t a s k of the p i l o t can be i n f l u e n c e d and s t u d i e d .
I n the l i t e r a t u r e a number of e x p e r i m e n t s on the i n f l u e n c e of m o t i o n i n c o n t r o l t a s k s i s r e p o r t e d , see R e f s . 2 t h r o u g h 7. The r e s u l t s of thèse e x p e r i m e n t s are not always c o n s i s t e n t , however. Différences i n the r e p o r t e d r e s u l t s can be a t t r i b u t e d to différences i n the dynamic c h a r a c t e r i s t i c s o f Systems to be c o n t r o l l e d , i n the c h a r a c t e r i s t i c s of the m o t i o n s i m u l a t i o n Systems and i n the expérimental s e t - u p s . E x p e r i m e n t s on the i n f l u e n c e o f p e r i p h e r a l v i s u a l eues on p i l o t c o n t r o l b e h a v i o u r a r e r e p o r t e d i n R e f s . 8 t h r o u g h 10. I t i s r e p o r t e d t h e r e t h a t , under c e r t a i n c i r c u m s t a n c e s , p e r i p h e r a l v i s u a l eues can p a r t i a l l y S u b s t i t u t e f o r vestibulär m o t i o n eues.
Because no work has been r e p o r t e d c o v e r i n g s y s t e m a t i c v a r i a t i o n o f a v a i l a b l e s e n s o r y eues, i t was d e c i d e d t o do an experiment i n the A e r o s p a c e D e p a r t -ment's moving base f l i g h t S i m u l a t o r , i n which a s i m p l e r o l l c o n t r o l t a s k and t h e v a r i o u s 'sensory d i s p l a y s ' - i . e . c e n t r a l C R T - d i s p l a y , p e r i p h e r a l f i e l d d i s p l a y and S i m u l a t o r c o c k p i t m o t i o n - were s y s t e m a t i c a l l y v a r i e d . Two différent c o n t r o l t a s k s (see S e c t i o n 4) were used, the c o n t r o l l e d élément c h a r a c t e r i s t i c s b e i n g the same i n b o t h c a s e s (see S e c t i o n 3 ) .
A l t h o u g h the b a s i c p h y s i c a l q u a n t i t y t o be c o n t r o l l e d i n a r o l l c o n t r o l t a s k i s the r o l l a n g l e , the q u a n t i f i e s p e r c e i v e d t h r o u g h the différent d i s p l a y s w i l l d i f f e r due to the différent c h a r a c t e r i s t i c s of the s e n s o r y organs i n -v o l -v e d and the p a r t i c u l a r way i n w h i c h the s e n s o r y i n f o r m a t i o n i s processed.
F o r i n s t a n c e , i t i s u s u a l l y assumed t h a t a human C o n t r o l l e r i s a b l e to dérive, from a c e n t r a l v i s u a l d i s p l a y , some measure of r a t e of change ( r o l l r a t e ) from the b a s i c r o l l angle i n f o r m a t i o n . A f a r b e t t e r i m p r e s s i o n of r o l l r a t e may be o b t a i n e d , however, from the p e r i p h e r a l v i s u a l f i e l d , which i s known to y i e l d m a i n l y v e l o c i t y i n f o r m a t i o n ( R e f . 11).
F u r t h e r m o r e , the o t o l i t h s i n the vestibulär system a r e a l s o s e n s i t i v e t o the S i m u l a t o r r o l l angle, due to the g r a v i t a t i o n a l i n f l u e n c e s , while the s e m i c i r c u l a r c a n a l organs are s e n s i t i v e t o r o l l accélération.
2. INSTRUMENTATION AND DATA REDUCTION
A i l measurements w i t h m o t i o n were c a r r i e d out i n the D e l f t U n i v e r s i t y of T e c h n o l o g y Department of A e r o s p a c e E n g i n e e r i n g f l i g h t S i m u l a t o r (see F i g . 1 ) . The t h r e e degrees of freedom m o t i o n system of t h i s S i m u l a t o r has unique
h i g h f i d e l i t y m o t i o n c h a r a c t e r i s t i c s , m a k i n g t h e s i m u l a t o r a v e r y s u i t a b l e t o o i f o r t h e p r e s e n t e x p e r i m e n t s . The a p p l i c a t i o n , i n t h i s m o t i o n S y s t e m , o f so c a l l e d ' h y d r o s t a t i c ' h e a r i n g s i n t h e h y d r a u l i c s e r v o a c t u a t o r s r e s u l t s i n v e r y s m o o t h and a l m o s t r u m b l e f r e e s i m u l a t o r m o t i o n s , s e e R e f . 1 2 . U n d e r n o r m a l o p e r a t i n g c o n d i t i o n s m o t i o n n o i s e i s w e l l b e l o w t h e t h r e s h o l d s o f m o t i o n p e r c e p t i o n , as d e t e r m i n e d by t h e t e s t s r e p o r t e d i n R é f . 1. F o r t h e p r e s e n t r o l l a x i s c o n t r o l t a s k , a c e n t r a l ( f o v e a l ) CRT d i s p l a y ( s i m u l a t i n g a n a r t i f i c i a l h o r i z o n ) was i n s t a l l e d i n t h e i n s t r u m e n t p a n e l i n f r o n t o f t h e s u b j e c t ' s s e a t i n t h e s i m u l a t o r c o c k p i t , as shown i n F i g . 2 . P e r i p h e r a l v i s u a l m o t i o n c u e s w e r e p r o v i d e d by two T . V . m o n i t o r s m o u n t e d a g a i n s t t h e s i d e Windows o f t h e s i m u l a t o r c o c k p i t ( F i g s . 2 and 3 ) . T h e s e m o n i t o r s d i s p l a y e d a m o v e a b l e c h e c k e r b o a r d p a t t e r n . The r e l a t i v e p o s i t i o n s o f t h e d i s p l a y s and t e s t s u b j e c t ' s e y e p o s i t i o n a r e g i v e n i n F i g . 3 , t h e t e c h n i c a l d e t a i l s o f w h i c h a r e d e s c r i b e d i n R e f . 1 3 . S u b j e c t s u s e d a s p r i n g c e n t e r e d s i d e - a r m c o n t r o l l e r t o c o n t r o l t h e d y n a m i c s o f t h e S y s t e m ( s e e S e c t i o n 3 ) . D e t a i l s o f t h e s i d e - a r m c o n t r o l l e r c a n b e f o u n d i n R e f . 1 4 . The d y n a m i c s o f t h e c o n t r o l l e d s y s t e m w e r e s i m u l a t e d o n a h y b r i d c o m p u t e r t h a t a l s o g e n e r a t e d t h e q u a s i - r a n d o m d i s t u r b a n c e s a c t i n g o n t h e s y s t e m ( s e e S e c t i o n 4 ) , as w e l l as t h e s i g n a i s c o n t r o l l i n g t h e d i s p l a y s and t h e s i m u l a t o r m o t i o n s y s t e m . The c o m p u t e r a l g o r i t h m s d r i v i n g t h e v i s u a l d i s p l a y s and t h e m o t i o n s y s t e m w e r e i m p l e m e n t e d s u c h t h a t t i m e d e l a y s b e t w e e n t h e s e S y s t e m s w e r e s m a l l e r t h a n 0 . 0 1 s e c o n d . D u r i n g t e s t r u n s m e a s u r e m e n t s w e r e t a k e n a t a r a t e o f 25 p e r s e c o n d . I r | . t h e c a s e o f t h e ' d i s t u r b a n c e t a s k ' t h e r o l l a n g l e l p , t h e r o l l r a t e (p and t h e c o n t r o l s t i c k d e f l e c t i o n 6 w e r e r e c o r d e d . I n t h e s o - c a l l e d ' f o l l o w i n g t a s k ' a ( s e e S e c t i o n 4) t h e r o l l a n g l e e r r o r e was r e c o r d e d i n a d d i t i o n t o (p , cp a n d 6 . a S h o r t l y a f t e r t h e end o f a t e s t r u n , d a t a a n a l y s i s was c o m p l e t e d b y a d i g i t a l p r o g r a m y i e l d i n g s t a n d a r d d é v i a t i o n s o f t h e r e c o r d e d v a r i a b l e s . S i m u l t a -n e o u s l y Bode p l o t s o f t h e huma-n o p e r a t o r t r a -n s f e r f u -n c t i o -n s w e r e o b t a i -n e d by u s i n g a F a s t F o u r i e r T r a n s f o r m ( F . F . T . ) r o u t i n e , R e f . 1 5 . A l l c o m b i n a t i o n s o f d i s p l a y c o n f i g u r a t i o n s u s e d i n t h e e x p e r i m e n t , a r e shown i n T a b l e 1. Due t o l i m i t e d a v a i l a b i l i t y o f t h e f l i g h t . s i m u l a t o r , a l l n o n -m o t i o n c o n d i t i o n s w e r e r u n i n a s i -m i l a r f i x e d b a s e e x p é r i -m e n t a l s e t - u p i n a n a c o u s t i c a l l y i s o l a t e d r o o m . A n a n a l y s i s o f v a r i a n c e r e v e a l e d no s i g n i f i c a n t d i f f é r e n c e s when a number o f t h e s e n o n - m o t i o n c o n d i t i o n s w e r e r e p l i c a t e d i n t h e f l i g h t s i m u l a t o r .
3 . ROLL CONTROL TASK DYNAMICS
T h e r o l l c o n t r o l t a s k was c h o s e n b e c a u s e i t was f e i t t h a t any i n f l u e n c e o f t h e p e r i p h e r a l d i s p l a y s w o u l d be more d r a m a t i c i n c o m p a r i s o n w i t h t h e o t h e r p o s s i b l e modes o f t h e f l i g h t s i m u l a t o r - i . e . p i t c h and h e a v e . The d y n a m i c s o f t h e c o n t r o l l e d s y s t e m w e r e t h o s e o f a d o u b l e i n t e g r a t o r h a v i n g t h e t r a n s f e r f u n c t i o n
H ( s ) ( 1 )
The dynamics of eq. (1) are r o u g h l y s i m i l a r to the r o l l c o n t r o l of a s l o w l y r e s p o n d i n g a i r c r a f t , such as a medium to l a r g e s i z e d j e t t r a n s p o r t f l y i n g a t low speeds. There i s , however, a minor différence between the m o t i o n to be sensed i n an a i r c r a f t and i n the s i m u l a t o r . When the s i m u l a t o r i n the p r e s e n t e x p e r i m e n t a l s e t - u p i s made to r o l l by a c o n t r o l s t i c k d e f l e c t i o n , the s u b j e c t sensés, i n a d d i t i o n to the r o t a t i o n a l r o l l accélération, a l a t e r a l f o r c e component due to the s i m u l a t o r t i l t . Due to the p a r t i c u l a r dynamics of an a i r c r a f t and i t s l a r g e r number of degrees of freedom, t h i s l a t e r a l f o r c e component i s v i r t u a l l y absent i n a c t u a l f l i g h t .
4. DISTURBANCE AND FOLLOWING TASK
I t i s known t h a t human c o n t r o l b e h a v i o u r i s a l s o i n f l u e n c e d by the manner i n which d i s t u r b a n c e s a c t on the c o n t r o l l e d l o o p , see Ref. 6. T h e r e f o r e two d i s t i n c t c o n t r o l t a s k s were used i n the p r e s e n t e x p e r i m e n t s .
I n the f i r s t one, the d i s t u r b a n c e t a s k , the d i s t u r b i n g s i g n a l was made t o a c t on the c o n t r o l l e d system, as shown i n F i g . 4a. I n t h i s s i t u a t i o n , which i s q u i t e comparable t o the case i n which a p i l o t s t a b i l i z e s an a i r c r a f t i n rough a i r , the r o l l a n g l e , or a t t i t u d e , p e r c e i v e d through the p e r i p h e r a l d i s p l a y by the c o c k p i t m o t i o n e x a c t l y c o r r e s p o n d s to the r o l l a t t i t u d e p r e s e n t e d on the c e n t r a l d i s p l a y . A l l ' s e n s o r y d i s p l a y s ' t h e r e f o r e y i e l d a t t i t u d e r e l a t i v e t o the o u t s i d e w o r l d .
I n the second c o n t r o l t a s k , the f o l l o w i n g , or t r a c k i n g t a s k , the d i s p l a y e d s i g n a l on the c e n t r a l d i s p l a y , e^, i s the différence between the d i s t u r b a n c e s i g n a l , i , and the r o l l a n g l e , cp , of the c o n t r o l l e d system, see F i g . 4b. The p e r i p h e r a l d i s p l a y and the m o t i o n system, however, c o r r e s p o n d w i t h the r o l l a n g l e (p o f the c o n t r o l l e d system. The m o t i o n of the system i n t h i s case dépends on the s u b j e c t ' s c o n t r o l a c t i o n o n l y and t h e r e i s no d i r e c t s i m p l e r e l a t i o n s h i p between r o l l a n g l e e r r o r as p r e s e n t e d by the c e n t r a l d i s p l a y and r o l l a n g l e and r o l l r a t e as p r e s e n t e d by the m o t i o n system and p e r i p h -e r a l d i s p l a y s .
I f o n l y one of the c o n t r o l l e d v a r i a b l e s cp or i s p r e s e n t e d on the c e n t r a l d i s p l a y , a w e l l t r a i n e d s u b j e c t i s a b l e t o discrimínate between a d i s t u r b -ance and a f o l l o w i n g t a s k , even though the t a s k g o a l , which i s to keep the d i s p l a y e d v a r i a b l e as s m a l l as p o s s i b l e , i s the same. The a d d i t i o n o f p e r i p h e r a l v i s u a l and m o t i o n eues s e r v e s to a m p l i f y the différence between the two t a s k s . I n the d i s t u r b a n c e t a s k , the t a s k g o a l can be a c h i e v e d by k e e p i n g the m o t i o n of the c o n t r o l l e d system as s m a l l as p o s s i b l e . T h i s can be a c h i e v e d by a v o i d i n g h i g h r o l l r a t e s , as would be caused by q u i c k and l a r g e c o n t r o l s t i c k d e f l e c t i o n s . T h i s i s c o n t r a r y to the. s i t u a t i o n i n the f o l l o w i n g t a s k , where the s u b j e c t i s f r e e t o i n d u c e l a r g e changes i n r o l l a t t i t u d e and r o l l r a t e i n o r d e r to m i n i m i z e the d i s p l a y e d e r r o r magnitude.
The d i s t u r b i n g s i g n a l used i n a l l t a s k s was a quasi-random one, c o n s i s t i n g o f the sum of 10 s i n u s o i d s whose f r e q u e n c y , a m p l i t u d e and phase are g i v e n i n
T a b l e 2. The s t a n d a r d déviation of the d i s t u r b i n g s i g n a l was a. = 1.875
5. SUBJECTS AND TEST PROCEDURE
Three s u b j e c t s , a l l u n i v e r s i t y s t a f f members and q u a l i f i e d j e t t r a n s p o r t p i l o t s , v o l u n t e e r e d f o r the e x p e r i m e n t s . E x t e n s i v e t r a i n i n g was done u n t i l s t a b l e performance, as e x p r e s s e d by r o l l a n g l e or r o l l a n g l e e r r o r Standard d e v i a t i o n , was r e a c h e d .
As the non-motion t e s t runs were performed o u t s i d e the s i m u l a t o r i n a s e p a r a t e e x p e r i m e n t a l s e t - u p , the a c t u a l e x p e r i m e n t s were r u n i n two p a r t s . W i t h i n each p a r t , c o n t r o l t a s k s and d i s p l a y c o n f i g u r a t i o n s were p r e s e n t e d i n random o r d e r . The d u r a t i o n of a s i n g l e t e s t r u n (one p a r t i c u l a r t a s k under one c o n f i g u r a t i o n ) was 110 seconds. Measurements were t a k e n o n l y d u r i n g the l a s t 82 seconds of a r u n . F i v e r e p l i c a t i o n s were performed, r e s u l t i n g i n a t o t a l of 4 x 3 x 5 = 60 t e s t runs f o r the f o l l o w i n g t a s k and 7 x 3 x 5 = 105 f o r the d i s t u r b a n c e t a s k .
E a c h s e r i e s of t e s t runs p r e s e n t e d to a s u b j e c t (6 o r 7 r u n s ) l a s t e d approx-i m a t e l y 20 to 25 m approx-i n u t e s . For the purpose of t r a approx-i n approx-i n g a l o n e , 420 t e s t runs were completed among the t h r e e s u b j e c t s b e f o r e s t a r t i n g the main t e s t program.
6. RESULTS
Two d i s t i n c t a s p e c t s of the c o n t r o l t a s k a r e c o n s i d e r e d h e r e : Task p e r f o r m -ance and c o n t r o l b e h a v i o u r . Task perform-ance i s e x p r e s s e d by the S t a n d a r d d e v i a t i o n of the c o n t r o l l e d v a r i a b l e s . C o n t r o l b e h a v i o u r i s a s s e s s e d by u s i n g the computed human c o n t r o l l e r Bode p l o t s .
Performanee D i s t u r b a n c e _ t a s k
From F i g . 5 an i m p r e s s i o n can be o b t a i n e d of the performance as e x p r e s s e d by the r e l e v a n t Standard d e v i a t i o n as a f u n c t i o n of d i s p l a y c o n f i g u r a t i o n . Adding the p e r i p h e r a l d i s p l a y s to the c e n t r a l d i s p l a y ( C o n f i g u r a t i o n 2) i s seen to have a b e n e f i c i a l e f f e c t on the performance of the d i s t u r b a n c e t a s k , but the i n f l u e n c e of m o t i o n i s seen t o be most d r a m a t i c ( C o n f i g u r a t i o n s 4, 5, 6 and 7 ) . Q u i t e remarkable i s the performance f o r the case of m o t i o n a l o n e ( C o n f i g u r a t i o n 7 ) . Once m o t i o n i s p r e s e n t l i t t l e appears to be g a i n e d by a d d i n g p e r i p h e r a l d i s p l a y s ( C o n f i g u r a t i o n s 4 and 5 ) . A d d i t i o n of t h e c e n t r a l d i s p l a y i n the case of m o t i o n ( C o n f i g u r a t i o n s 5 and 6) g i v e s a s m a l l but s i g n i f i c a n t improvement. The Standard d e v i a t i o n s of the a n g u l a r r a t e <p and the c o n t r o l output 6 a l s o demonstrate the c o n s i d e r a b l e i n f l u e n c e of m o t i o n . I n summary i t can be o b s e r v e d t h a t a d d i t i o n of the p e r i p h e r a l d i s -p l a y s i n the d i s t u r b a n c e t a s k im-proves t h e -performance of the s u b j e c t s j u s t as m o t i o n does, the i n f l u e n c e of m o t i o n b e g i n s t r o n g e r . No f u r t h e r improve-ment c a n be o b t a i n e d by a d d i n g the p e r i p h e r a l d i s p l a y s once m o t i o n i s p r e s e n t .
F o l l o w i n g _ t a s k
A s i m i l a r d e c r e a s e of a6 ( p - i . e . improved performance - i s seen f o r the
f o l l o w i n g t a s k due to the a d d i t i o n of e i t h e r the p e r i p h e r a l d i s p l a y s , m o t i o n or b o t h , see F i g . 5. I n t h i s t a s k the p e r i p h e r a l v i s u a l and m o t i o n cues a r e not i n c o r r e s p o n d e n c e w i t h the c e n t r a l l y d i s p l a y e d e r r o r s i g n a l e^. However, the same t r e n d of d e c r e a s i n g S t a n d a r d d e v i a t i o n s i s found f o r b o t h tp and <P a l t h o u g h these v a r i a b l e s a r e not the d i r e c t l y c o n t r o l l e d ones, see F i g . 5.
The s t a n d a r d déviations f o r ô f o l l o w a s i m i l a r t r e n d . From thèse d a t a i t a p p e a r s t h a t the i n f l u e n c e of the p e r i p h e r a l d i s p l a y s i s s t r o n g e r t h a n i n the case of the d i s t u r b a n c e t a s k whereas t h e i n f l u e n c e o f m o t i o n i s s l i g h t l y l e s s .
A n a l y s i s of v a r i a n c e on the measured v a r i a b l e s of the 105 t e s t r u n s f o r t h e d i s t u r b a n c e t a s k and the 60 t e s t runs f o r t h e f o l l o w i n g t a s k a r e summarized i n T a b l e 3. These a n a l y s e s show t h a t the changes i n performance, as e x p r e s s e d by and ae^)> dueto changes o f t h e d i s p l a y c o n f i g u r a t i o n s , a r e s i g n i f i c a n t f o r b o t h t a s k s .
T h i s a l s o h o l d s f o r the s t a n d a r d déviations of ip and ô f o r the d i s t u r b -ance t a s k and cp , <p and ô f o r t h e f o l l o w i n g t a s k . I n a d d i t i o n a s i g n i f i c a n t i n f l u e n c e o f the s u b j e c t s and the i n t e r a c t i o n between s u b j e c t s and c o n f i g u r a t i o n s i s demonstrated f o r thèse v a r i a b l e s . T h i s i n d i c a t e s t h a t s u b j e c t s , w h i l e o b t a i n i n g a p p r o x i m a t e l y e q u a l performance, used différent c o n t r o l s t a t e g i e s and r e a c t e d d i f f e r e n t l y on t h e changes o f t h e d i s p l a y c o n -f i g u r a t i o n s .
The mean e f f e c t s o f a d d i n g p e r i p h e r a l d i s p l a y s o r m o t i o n c a n be summarized by t h e f o l l o w i n g r e l a t i v e d e c r e a s e s i n s t a n d a r d déviations o f t h e c o n t r o l l e d v a r i a b l e s a.n and a~. . Task P e r i p h e r a l d i s p l a y M o t i o n D i s t u r b a n c e t a s k F o l l o w i n g t a s k 12% 16% 59% 32% C o n t r o l b e h a y i o u r
Bode p l o t s of the t r a n s f e r f u n c t i o n H (GO) r e l a t i n g the s u b j e c t ' s i n p u t tp or e^j t o t h e s u b j e c t ' s o u t p u t ô were* c a l c u l a t e d f o r a i l c o m b i n a t i o n s o f d i s p l a y c o n f i g u r a t i o n s and c o n t r o l t a s k s t e s t e d .
D i s t u r b a n c e _ t a s k
The bode p l o t s of the t r a n s f e r f u n c t i o n K (co) f o r the d i s t u r b a n c e t a s k a r e p r e s e n t e d i n F i g s . 6 and 7. Due t o t h e
addition
o f p e r i p h e r a l v i s u a l and m o t i o n eues the modulus o f the t r a n s f e r f u n c t i o n i s seen t o i n c r e a s e a t low f r e q u e n c i e s . As c o u l d be e x p e c t e d from t h e performance d a t a , the i n f l u e n c e o f m o t i o n on the t r a n s f e r f u n c t i o n i s the s t r o n g e s t . Of a i l t h e c o n f i g u r a -t i o n s w i -t h o u -t c e n -t r o l d i s p l a y ( C o n f i g u r a -t i o n s 3, 6 and 7 ) , C o n f i g u r a -t i o n 3 ( p e r i p h e r a l d i s p l a y o n l y ) shows a d r e c r e a s e of the modulus a t the low f r e -q u e n c i e s . T h i s c a n be e x p l a i n e d by the f a c t t h a t i n t h i s c o n f i g u r a t i o n , s u b j e c t s c o u l d h a r d l y dérive any r o l l a t t i t u d e i n f o r m a t i o n from thèse d i s -p l a y s , e s -p e c i a l l y a t the low f r e q u e n c i e s . I n the C o n f i g u r a t i o n s 6 and 7 however, t h e s u b j e c t s c a n p e r c e i v e the s i d e , f o r c e due to the bank a n g l e tp. From thèse d a t a i t f o l l o w s t h a t the s i d e f o r c e i s ä good S u b s t i t u t e f o r the c e n t r a l v i s u a l d i s p l a y . I n F i g . 8 the c r o s s o v e r f r e q u e n c y and the phase m a r g i n cpm have been p l o t t e d as a f u n c t i o n o f the seven c o n f i g u r a t i o n s . As c o u l d be e x p e c t e d , t h e c r o s s o v e r f r e q u e n c y i s i n c r e a s e d when the p e r i p h e r a l260
-d i s p l a y s an-d m o t i o n a r e a-d-de-d to the c e n t r a l -d i s p l a y . The phase m a r g i n remains a p p r o x i m a t e l y c o n s t a n t .
F o 1 l o w i n g _ t a s k
F o r the f o l l o w i n g t a s k , see F i g . 9 the changes due t o a d d i t i o n of p e r i p h e r a l v i s u a l and m o t i o n cues a r e o p p o s i t e t o the ones i n the d i s t u r b a n c e t a s k . The modulus d e c r e a s e s e s p e c i a l l y at the low f r e q u e n c i e s , the phase a n g l e i n c r e a s e s a t low f r e q u e n c i e s and d e c r e a s e s a t h i g h f r e q u e n c i e s .
I n F i g . 8 the c r o s s o v e r f r e q u e n c y w and the phase marging u?m have been
p r e s e n t e d as a f u n c t i o n of the f o u r dísplay c o n f i g u r a t i o n s . I n t h i s case oo i s h a r d l y i n f l u e n c e d by t h e a d d i t i o n o f the p e r i p h e r a l d i s p l a y s o r m o t i o n . However, the phase m a r g i n i s seen t o i n c r e a s e . F i n a l l y , F i g s . 10 and 11 may s e r v e t o s t r e s s the d i f f e r e n c e s i n the changes of the s u b j e c t ' s c o n t r o l b e h a v i o u r . I n these F i g u r e s the open l o o p t r a n s f e r f u n c t i o n s H (co).H (OJ) f o r two d i s p l a y c o n f i g u r a t i o n s a r e p l o t t e d f o r b o t h the d i s t u r b a n c e anct t h e f o l l o w i n g t a s k .
Summarizing the r e s u l t s c o n c e r n i n g the c o n t r o l b e h a v i o u r i n both t a s k s i t can be c o n c l u d e d t h a t the performance improvement due t o the a d d i t i o n o f p e r i p h e r a l d i s p l a y s and/or motion, c o i n c i d e s w i t h changes i n the s u b j e c t ' s t r a n s f e r f u n c t i o n i n both t a s k s .
F o r the d i s t u r b a n c e t a s k the performance improvement can e a s i l y be e x p l a i n e d by t h e i n c r e a s e o f to a t n e a r l y c o n s t a n t o? .
C i ü
F o r the f o l l o w i n g t a s k , however, the performance improvement i s seen t o be accompanied by an i n c r e a s e i n phase m a r g i n , the c r o s s o v e r f r e q u e n c y r e m a i n i n g n e a r l y c o n s t a n t .
7. DISCUSSION AND CONCLUSIONS
That m o t i o n as w e l l as p e r i p h e r a l v i s u a l cues s h o u l d , i n g e n e r a l , have a c o n s i d e r a b l e i n f l u e n c e on s u b j e c t ' s c o n t r o l performance and c o n t r o l b e h a v i o u r c o u l d be expected c o n s i d e r i n g the r e s u l t s r e p o r t e d i n t h e l i t e r a t u r e ( R e f s . 2 through 1 0 ) . I n t h e p r e s e n t experiment, however, t h e d i s t u r b a n c e s i g n a l was s m a l l , r e s u l t i n g i n v e r y low valúes o f the s t a n d a r d d e v i a t i o n of the r o l l angle and r o l l a n g l e r a t e (o"(p = 1-3 d e g r e e s , 0^= 1 , 5 5 d e g r e e s / s e c ) . I n s p i t e o f these low valúes, a c o n s i d e r a b l e i n -f l u e n c e , e s p e c i a l l y o -f m o t i o n , was -found on per-formance and c o n t r o l b e h a v i o u r .
Ref. 6 d e s c r i b e s d i s t u r b a n c e and f o l l o w i n g t a s k s u s i n g c o n f i g u r a t i o n s
s i m i l a r t o no's 1 and 4 ( c e n t r a l d i s p l a y o n l y and c e n t r a l d i s p l a y w i t h m o t i o n ) . The r e s u l t s a r e q u i t e comparable t o the p r e s e n t ones: a performance improvement and a c o n s i d e r a b l e i n c r e a s e o f the c r o s s o v e r f r e q u e n c y f o r t h e d i s t u r b a n c e t a s k . The f o l l o w i n g t a s k of R e f . 6 showed a s l i g h t improvement of t h e performance t o g e t h e r w i t h a 1 arge i n c r e a s e o f the phase l e a d a t low f r e q u e n c i e s due t o the a d d i t i o n of m o t i o n .
Another experiment w i t h a f o l l o w i n g t a s k o n l y , see R e f . 9, showed the same t r e n d as the p r e s e n t one a l t h o u g h the c o n t r o l l e d system of R e f . 9 was a much more d i f f i c u l t one to c o n t r o l .
The remarkable d i f f e r e n c e between the changes of c o n t r o l b e h a v i o u r f o r both c o n t r o l t a s k s brought about by the a d d i t i o n o f p e r i p h e r a l v i s u a l and m o t i o n cues c a n p r o b a b l y be e x p l a i n e d i n terms of a d i f f e r e n c e i n the s u b j e c t i v e c o s t f u n c t i o n t h a t the s u b j e c t s t r i e d to m i n i m i z e . I f t h e s u b j e c t t r i e s t o m a i n t a i n the r o l l a n g l e (p on the c e n t r a l d i s p l a y i n the d i s t u r b a n c e t a s k as
s m a l l as p o s s i b l e , the p e r i p h e r a l d i s p l a y e d r o l l r a t e tp and the s i m u l a t o r m o t i o n w i l l a l s o be s m a l l . I n the case o f the f o l l o w i n g task, however, r e l a t i v e l y l a r g e r o l l a n g l e s and r o l l r a t e s w i l l o c c u r , when the s u b j e c t m i n i m i z e s the c e n t r a l l y d i s p l a y e d r o l l a n g l e e r r o r . From the p r e s e n t experiment i t turns out that f o r the f o l l o w i n g t a s k , the s u b j e c t s d e v e l o p e d a c o n t r o l s t r a t e g y t h a t r e s u l t e d not o n l y i n a d e c r e a s e i n r o l l a n g l e e r r o r e^p but a l s o i n an a c c u r a t e c o n t r o l of the r o l l a n g l e cp and r o l l a n g l e r a t e (p, i f p e r i p h e r a l v i s u a l and m o t i o n cues were p r e s e n t . A p p a r e n t l y , s u b j e c t s
tended t o keep the r o l l angle and r o l l angle r a t e at r e l a t i v e l y low v a l u e s . T h i s means t h a t they somehow i n c l u d e d these v a r i a b l e s i n t h e i r s u b j e c t i v e c o s t f u n c t i o n .
Summarizing the r e s u l s of the p r e s e n t experiments i t c a n be c o n c l u d e d t h a t :
1. Performance i s improved s i g n i f i c a n t l y i n b o t h d i s t u r b a n c e and f o l l o w i n g t a s k by adding p e r i p h e r a l v i s u a l cues and/or m o t i o n cues.
2. C o n t r o l b e h a v i o u r as e x p r e s s e d by human o p e r a t o r t r a n s f e r f u n c t i o n s i s i n f l u e n c e d by a d d i n g p e r i p h e r a l v i s u a l cues and/or m o t i o n cues i n both d i s t u r b a n c e and f o l l o w i n g t a s k .
3. I n the d i s t u r b a n c e t a s k the i n c r e a s e i n performance due t o the a d d i t i o n of p e r i p h e r a l v i s u a l and/or m o t i o n cues i s r e a d i l y i n t e r p r e t e d by t h e i n c r e a s e i n the c r o s s o v e r f r e q u e n c y .
4. I n the f o l l o w i n g o r t r a c k i n g t a s k the i n f l u e n c e of p e r i p h e r a l and/or m o t i o n cues on t h e human o p e r a t o r t r a n s f e r f u n c t i o n shows a t r e n d o p p o s i t e to the one i n the d i s t u r b a n c e t a s k . As a consequence improve-ments i n performance cannot r e a d i l y be i n t e r p r e t e d i n terms of human o p e r a t o r t r a n s f e r f u n c t i o n s .
A l t h o u g h improvements i n performance and changes i n dynamic b e h a v i o u r were d e f i n i t e l y demonstrated as a r e s u l t of the a d d i t i o n of p e r i p h e r a l v i s u a l cues and m o t i o n cues, i t i s not c l e a r what e x a c t l y a r e the causes f o r these improvements and changes.
M o t i o n p e r c e p t i o n may have been improved i n e i t h e r of two ways.
F i r s t l y i t may be t h a t by a d d i t i o n o f p e r i p h e r a l v i s u a l and/or m o t i o n c u e s , redundant I n f o r m a t i o n i s made a v a i l a b l e to the s u b j e c t thus improving t h e a c c u r a c y of the m o t i o n p e r c e p t i o n p r o c e s s .
Another p o s s i b i l i t y i s t h a t due t o d i f f e r e n c e s i n the dynamic c h a r a c t e r -i s t -i c s o f the v e s t -i b u l a r system and the p e r -i p h e r a l v -i s u a l system on the one hand, and those o f the f o v e a l v i s u a l system on the o t h e r , a s u b j e c t r e c e i v e s a d d i t i o n a l i n f o r m a t i o n t h a t e n a b l e s him t o improve m o t i o n p e r c e p t i o n .
F u r t h e r r e s e a r c h i n t o the m o t i o n p e r c e p t i o n p r o c e s s i n p a r t i c u l a r i n t o the s e p a r a t e a s p e c t s of c e n t r a l v i s u a l , p e r i p h e r a l v i s u a l and v e s t i b u l a r m o t i o n p e r c e p t i o n and t h e i r i n t e r a c t i o n s i s c a l l e d f o r .
8. REFERENCES
1. Hosman, R.J.A.W. and Van der V a a r t , J.C. V e s t i b u l a r models and t h r e s h -o l d s -of m -o t i -o n p e r c e p t i -o n . R e s u l t s -of t e s t s i n a f l i g h t s i m u l a t -o r . D e l f t U h i v e r s i t y of Technology, Department of Aerospace E n g i n e e r i n g , Report LR-265, 1978.
262
-2. S e c k e i , E., H a l l , I.A.M., McRuer, D.T. and Weir, D.H. Human p i l o t dynamic r e s p o n s e i n f l i g h t and s i m u l a t o r . WADC T e c h n i c a l Report 57-520. W r i g h t - P a t t e r s o n AFB, Ohio, 1958.
3. N e w e l l , F.D. Human t r a n s f e r c h a r a c t e r i s t i c i n f l i g h t and ground s i m u l a t i o n f o r the r o l l t r a c k i n g t a s k . AFFDL-TR-67-30. W r i g h t - P a t t e r s o n AFB, Ohio, 1968.
4. S t a p l e f o r d , R.L., P e t e r s , R.A. and A l e x , F.R. E x p e r i m e n t s and a model f o r p i l o t dynamics w i t h v i s u a l and m o t i o n i n p u t s . NASA CR-1325, 1969. 5. M e i r y , J . L . The v e s t i b u l a r system and human dynamic space o r i e n t a t i o n .
NASA CR-628, 1966.
6. L e v i s o n , W.H. and J u n k e r , A.M. A model f o r the p i l o t ' s use of m o t i o n cues i n r o l l - a x i s t r a c k i n g t a s k s . B o l t , Beranek and Newman I n c . R e p o r t no. 3528. Cambridge, M a s s a c h u s e t t s , 1977.
7. L e v i s o n , W.H. Use of m o t i o n cues i n s t e a d y s t a t e t r a c k i n g . P r o c e e d i n g s of the T w e l f t h Annual C o n f e r e n c e on Manual C o n t r o l . NASA TM-X-73, 170, 1976.
8. Z a c h a r i a s , G.L. and Young, L.R. I n f l u e n c e of combined v i s u a l and v e s t i -b u l a r cues on human p e r c e p t i o n and c o n t r o l of h o r i z o n t a l r o t a t i o n . P r e s e n t e d a t the S o c i e t y f o r N e u r o s c i e n c e , 8 t h Annual M e e t i n g . A S a t e l l i t e Symposium. " V e s t i b u l a r F u n c t i o n and Morphology" i n P i t t s b u r g , 1978.
9. M o r i a r t y , T.E., J u n k e r , A.M. and P r i c e , D.R. R o l l a x i s t r a c k i n g improve-ment r e s u l t i n g from p e r i p h e r a l v i s i o n m o t i o n c u e s . P r o c e e d i n g s of t h e T w e l f t h Annual C o n f e r e n c e on Manual C o n t r o l , NASA TM-X-73, 170, 1976. 10. J u n k e r , A.M. and P r i c e , D.R. Comparison between a p e r i p h e r a l d i s p l a y and
m o t i o n i n f o r m a t i o n on human t r a c k i n g about a r o l l a x i s . P r o c e e d i n g s AIAA V i s u a l and M o t i o n S i m u l a t i o n C o n f e r e n c e , 26-28 A p r i l 1976.
11. Hood, J.D. and Leech, J . The s i g n i f i c a n c e of p e r i p h e r a l v i s i o n i n t h e p e r c e p t i o n o f movement. A c t a O t o l a r y n g 77, 72-79, 1974.
12. Den H o l l a n d e r , J.G. and B a a r s p u l , M. Measurement of m o t i o n q u a l i t y of a moving base f l i g h t s i m u l a t o r . D e l f t U n i v e r s i t y o f T e c h n o l o g y , Dept. o f
A e r o s p a c e E n g i n e e r i n g , Memorandum M-264. 1977.
13. Hosman, R.J.A.W. and Van der V a a r t , J.C. T h r e s h o l d s of m o t i o n p e r c e p t i o n and parameters of v e s t i b u l a r models o b t a i n e d from t e s t s i n a m o t i o n s i m u l a t o r . E f f e c t s of v e s t i b u l a r and v i s u a l m o t i o n p e r c e p t i o n on t a s k p e r f o r m a n c e . D e l f t U n i v e r s i t y o f T e c h n o l o g y , Department of A e r o s p a c e E n g i n e e r i n g , Memorandum M-372, 1980.
14. M o o i j , H.A. A i r b o r n e equipment used d u r i n g i n - f l i g h t measurements of human p i l o t d e s c r i b i n g f u n c t i o n s . Memorandum VS-72-001. N a t i o n a l A e r o s p a c e L a b o r a t o r y NLR, Amsterdam 1972.
15 R e i d , L.D. and K u i l , R . J . An i n v e s t i g a t i o n i n t o some p r o p e r t i e s o f t h e b i o m o r p h i c model of the human p i l o t . Department of Aerospace E n g i n e e r -i n g , Report LR-278. D e l f t U n -i v e r s -i t y o f T e c h n o l o g y , 1979.
T a b l e 1; D i s p l a y c o n f i g u r a t i o n s C o n f i g u r a t i o n no/code C e n t r a l d i s p l a y P e r i p h e r a l d i s p l a y M o t i o n t a s k J ) i B t u r b a n c e _ F o l l o w i n g 1 C X D, F 2 CP X X D, F 3 P X D A CM X X D, F 5 CPM X X X D, F 6 PM X X D 7 H X D
T a b l e 2: F r e q u e n c y , a m p l i t u d e and phase o f the s l n u s o i d s uaed t o g e n e r a t e the quasl-random d i s t u r b a n c e s i g n a l
Frequency Amplitude Phase
u ( d e g r e e s ) ( d e g r e e s ) ( r a d / s e c ) 0.153 1.106 4 0.230 1.099 151 0.383 1.083 43 0.537 1.058 122 0.997 0.957 324 1.457 0.842 184 2.378 0.646 281 4.065 0.428 194 7.440 0.247 162 13.576 0.136 43 T a b l e 3: R e s u l t s o f the a n a l y s l s o f v a r i a n c e on the s t a n d a r d déviation o f the meaBured v a r i a b l e s
D i s t u r b a n c e t a s k °<P %
\
1 C o n f i g u r a t i o n s 2 S u b j e c t s 3 I n t e r a c t i o n s u b j e c t s -c o n f i g u r a t i o n s 4 R e p l i c a t l o n s **** **** **** **** * **** **** **** * F o l l o w i n g t a s k 0 % a 1 C o n f i g u r a t i o n s 2 S u b j e c t s 3 I n t e r a c t i o n s u b j e c t s -c o n f i g u r a t i o n s 4 R e p l i c a t l o n s **** ** **** **** ** **** **** *** **** **** **** *** o < 0.01 **** a < 0.05 *** a < 0.1 ** o < 0.25 *-
266-F i g . 3 . P o s i t i o n s o f d i s p l a y s r e l a t i v e t o t h e t e s t s u b j e c t ' s eye p o s i t i o n . C e n t r a l d i s p l a y i m a g e .
disturbing function
i
Controlled
element
H
c(s)
motion cues
peripheral cues
central visual cues
r o l l angle
©
Disturbance task
sturbing
function
1
i
central (CRT)
display
P i l o t
Hp(*>
©
Controlled
element
Hc(s)
motion
çues
peripheral cues
r o l l angle q>
Following task
r o l l angle
Fig- 4; Block diagram of controller and controlled element for
the disturbance task and the following task.
D i s t u r b a n c e t a s k P 168
[de
grées)
C
é c p
0
C M CPM
PM M
_J L .C central display
P peripheral display
M motion
4
3
2
1(degrees/sec)
O0
0 12
idegrees)
C) C ) O4>
3 A 5 6 7
0)
Following task
(degrees)
C
C)
C P
© CM CPM
C y
1 2
(degrees)
3>
CT,1 2 4
(degrees/sec)
C)G
3
2
1 01 2
(degrees)
0
0
_i : — L-1 2 3 4 5 6 7 -1 2
D i s p l a y c o n f i g u r a t i o n sF i g . 5: Standard d é v i a t i o n s of c o n t r o l l e d v a r i a b l e s and control
d e f l e c t i o n s as a function of d i s p l a y c o n f i g u r a t i o n .
A
G• •
9
• 9 •
: •
Display configuration
• 1 ( C )
A2 ( CP)
o 4 ( CM)
O 5 ! CPM)
0.1
10 100
G j (rad/sec)
. 4
f í •
o ¿
é l
6® s
•
•
0.1
10
Í
*> (rad/»ec)
6: Bode plots of the transfer function
Hp(oj)of the test
~~ subjects in the disturbance task.
Display configurations 1, 2 , 4 and 5.
270 100 10 0.1
© o
• CE A A 0.1 0 . A A«4
i
A D i s p l a y c o n f i g u r a t i o n•
1 ( C ) A 3 ( P )•
6 { P M )O
7 ( M ) 10 100 CL) ( r a d / s e c ) 9 0 ( d e g r e e s )f .
- 9 0 180. A
£ AS
Q
A * ¿ ô 8 S Q © A •©
B • A 0.1 10w ( rad/sec)
F i g . 7: Bode p l o t s of the t r a n s f e r f u n c t i o n Hp(oa) o f th e t e s t
s u b j e c t s i n the d i s t u r b a n c e t a s k . D i s p l a y c o n f i g u r a t i o n s 1, 3, 6 and 7.
Disturbance task
5 4 ( r o d / s e c )4 4 4 0
3 430
1 410
(dvgrees)
î
C2 420
C P PQ H H
CPM CM & P M•
U M•
A crossover freq. u>
c• phase margin
Following task
5 4 ( d*gr**s J
(rad/s»c)
| 4 --40
3 430
2420
1410
t
C C P•
•
C P M CM•
D i s p l a y c o n f i g u r a t i o n sFig- 8: Phase margins and crossover frequencies of H ( s ) . H (s) as a
272 -10 Hp(u>) 0.1 0.01
