Download pdf - A FOR - CORE · the processor control, the system processor unit, ... The closed circuit wind tunnel ... under the control of a microprocessor

A MICROPROCESSOR BASED SYSTEM FOR W I N D TUNNEL MEASUREMENTS

C. Ravikumar, lbl. B a l a k r i s h n a n a n d V . S . Hol la

Depar tment of Aeroepaco E n g i n e e r i n g I n d i a n I n s t i t u t e o f S c i e n c e , B a n g a l a r e , I n d i a .

b b a t r a c t :

A 1 6- b i t m i c o p r o c e s s o r based s y s t e m h a s been d e s i g n e d and deve loped f o r a u t o m a t i c f l o w f i e l d p r e s s u r e s u r v e y and f o r c e measurements i n t h e low speed wind t u n n e l a t t h e I n d i a n I s t i t u t e of S c i e n c e . The i n s t r u m e n t a t i o n sub sys tems t h a t a r e r e q u i r e d f o r t h e above measurements u n d e r t h e p r o c e s s o r c o n t r o l , t h e sys tem p r o c e s s o r u n i t , i n t e r f a c e s t o s t a n d a r d p e r i p h e r a l s , f u t u r e e x p a n s i o n p r o v i s i o n s a n d communicat ion c h a n n e l t o o t h e r compute r sys tems have a l l been d e v e l o p e d in- house . S o f t w a r e h a s been d e s i g n e d t o p r o v i d e a p o w e r f u l f r i e n d l y a n d r e c o n f i g u r a b l e i n t e g r a t e d i n s t r u - m e n t a t i o n . The s o f t w a r e a l s o e n s u r e s q e a l t ime d a t a a c q u i s i o n , o n- l i n e 'pre- p r o c e s t l i n g and s t o r a g e o f t h e d a t a on a f l o p p y . S o f t w a r e h a s a l s o been d e v e l o p e d on a n i n e x p e n s i v e PC f o r t h e d a t a p r e s e n t a t i o n i n c o l o r g r a p h i c s . The d e s i g n , development and i m p l e m e n t a t i o n d e t a i l s , o f t h e syatem have been p r e s e n t e d l a thie p a p e r .

X n t r o d u c t i o n :

The c l o s e d c i r c u i t wind t u n n e l (CCWT) a t t h e d e p a r t m e n t of Aerospace E n g i n e e r i n g , I n d i a n I n s t i t u t e o f S c i e n c e , h a s been e s t a b l i s h e d i n 1947. The t e s t s e c t i o n o f t h e t u n n e l has an e l l i p t i c a l c r o s s - s e c t i o n o f d i m e n s i o n s 7 ' x 5' and i s b e i n g used f o r f l o w f i e l d s u r v e y s , force/moment and p r e s s u r e s u r v e y measurements . Recen t i n s t r u m e n t a t i o n s e t - u p i n c l u d e d a 3-D t r a v e r s e mechanism powered by i n d u c t i o n m o t o r s , p r e s s u r e p r o b e s , manometer banks t o r e a d t h e p r e s s u r e s and a m e c h a n i c a l b a l a n c e f o r f o r c e measurements . The p r o b e t r a v e r s i n g i s done t h r o u g h a s e t o f ON/OFF s w i t c h e s o o n t r o l l e d manua l ly t o move t h e p robe i n t h e r e q u i r e d d i r e c t i o n over a t e s t s e c t ' i o n o f 96" x 48" x 3 6 " . A se t o f m e c h a n i c a l c o u n t e r s a r e u s e d t o i n d i c a t e t h e t r a v e r s e p o s i t i o n . T h i s a r r a n g e m e n t p r o v i d e d a r e s o l u t i o n of 0.0025t1 and 0.1l' o v e r a l l a c c u r a c y i n p robe p o s i t i o n i n . The pre8sure p r o b e used f o r f l o w f i b f d s u r v e y

54-IClASF '87 RECORD

i s a b l u n t e d c o n i c a l n o s e 5 h o l e p r o b e . Both U-tube manometer banks and r e s e r v o i r t y p e manometer banks a r e a v a i l a b l e f o r p r e s s u r e d a t a c o l l e c t i o n . F o r a c c u r a t e p r e s s u r e measurements a s e t of p r o j e c t i o n manometers i n d i g e n e o u s l y deve loped a t t h e d e p a r t m e n t a r e a l s o a v a i l a b l e . T h e s e m a n u a l l y r e a d manometers have a r e s o l u t i o n of 0 . 2 ~ ~ . I n a t y p i c a l t u n n e l r u n , t h e t e s t model i s mounted on t h e m e c h a n i c a l b a l a n c e ' s t r u t s and t h e aerodynamic f o r c e s and moments a r e measured m a n u a l l y by c o u n t e r b a l a n c i n g t h e unknown l o a d s wi th dead w e i g h t s . Flow f i e l d d a t a i s c o l l e c t e d t h r o u g h t h e p r e s s u r e p r o b e , f i t t e d t o t h e m a n u a l l y o p e r a t e d t r a v e r s e meachanism and a manometer bank o r t h r o u g h a s e t o f 6 p r o j e c t i o n manometers. The p r e s s u r e s u r v e y f rom t h e body t a p p i n g s is made w i t h a manometer bank. For t h e d a t a r e d u c t i o n , t h e g a t h e r e d d a t a i s f i r s t punched on compute r c a r d s and t h e n f e d t o t h e main frame computer DEC sys tem 1090 a t t h e c e n t r a l comput ing f a c i l i t y o f t h e i n s t i t u t e .. System Overview

demand f o r t h e i n s t r u m e n t a t i o n been upgraded

I n o r d e r t o meet t h e i n c r e a s i n g t u n n e l a v a i l a b i l i t y , t h e

Rystem i n t h e t u n n e l have t o au tomate moat o f the

e x p e r i m s n t a l p r o c e d u r e s [ I 1. The imminen t a d v a n t a g e s due' t o t h i e a r e f a t i t e r a n d a c c u r a t e d a t a a c q u i s i t i o n t h a t i s f r e e from human e r r o r s , and r e d u c t i o n i n t o t h e ae rodynamic q u a n t i t i e s , which make t h e system s e l f c o n t a i n e d and improve t h e t u r n a r o u n d time.

The modern t e c h n o l o g y i n t h e f i e l d s o f wind t u n n e l i n s t r u m e n t a t i o n a n d compute r b a s e d s y s t e m s , o f f e r a wide c h o i c e o f i n s t r u m e n a t i o n and programmable c o n t r o l l e r s t o a u t o m a t e a t e s t f a c i l i t y . On t h e i n s t r u m e n a t a t i o n f r o n t , however , f o r most o f t h e small- and medium-range t e s t f a c i l i t i e s , t h e c h o i c e i s l i m i t e d by s e v e r a l f a c t o r s l i k e t h e p r e s e n t c i r c u m s t a n c e s of t h e t u n n e l o p e r a t i o n , , t h e e x h o r b i t a n t c o s t f a c t o r s i n v o l v e d i n t h e i n a t r u m e n t a t i o n and t h e r e q u i r e d

1 1

CX2449-7/87/0000-004 $1.00 @ 1987 UJB

m o d i f i c a t i o n s t o t h e t u n n e l t o accomodat new i n s t r u m e n a t i o n . Due t o such r e a s o n s , t h e i n s t r u m e n t a t i o n i n t h e above t u n n e l h a s been upgraded t o f a c i l i t a t e a u t o m a t i o n i n s t e a d o f a c q u i r i n g modern equipment l i k e l a s e r d o p p l e r v e l o c i m e t e r s , e t c . [Z -81 . T h i s u p g r a d a t i o n work i n c l u d e d t h e d e s i g n and i n t e r f a c e s t o c o n t r o l t h e mechan ica l i n s t r u m e n t s , t h e deve lopment o f a new p r e s s u r e measur ing d e v i c e and tin an t i log DAS. A d i g i t a l i n t e r f a c e h a s been d e s i g n e d and deve loped t o a u t o m a t e t h e 3 - D p r o b e t r a v e r s e o p e r a t i o n . A new 6- c h a n n e l d i g i t a l manometer h a s been d e s i g n e d a n d d e v e l o p e d t o a c q u i r e t h e p r e s s u r e d a t a f rom t h e 5- hole p robe and t h e t u n n e l f r e e stream. T h i s s e n s o r i s based on a u t o m a t i n g t h e p r a s s u r e measurement p r o c e s s o f a c o n v e n t i o n a l U- tube manometer u n d e r t h e c o n t r o l o f a m i c r o p r o c e s s o r . I n s t r u m e n t s l i k e s c a n i v a l v e o r a n ESOP [ 7 1 would a l s o c l a i m a p l a c e i n such a n a p p l i c a t i o n . However, t h e a b i l i t y t o r e a d a c c u r a t e l y all t h e 6 c h a n n e l s s i m u l t a n e o u s l y o v e r a wide dynamic r a n g e , and t h e r e l a t i v e l y low c o s t makes i t a more s u i t a b l e one f o r t h e p r e s e n t

To f a c i l i t a t e t h e a u t o m a t i c c o n t r o l o f t h e model a t t i t u d e , a new model mount ing r i g h a s been i n s t a l l e d . The model mount ing r i g d e s i g n e d and deva loped by a n o t h e r g r o u p i n t h e d e p a r t b e n t p r o v i d e s t h e model c o n t r o l i n t h e d i r e c t i o n s of p i t c h and yaw. F o r a c c u r a t e force measurements , as a n obv ious c h o i c e , a 6-component s t r a i n gauge b a l a n c e h a s been a c q u i r e d . The p r e s e n t and t h e f u t u r e e x p e r i m e n t a l n e e d s a t t h e CCWT d i c t a t e t h a t t h e d a t a f rom t h e s t r a i n g a u g e b a l a n c e be a c q u i r e d a t a 1 KHz s a m p l i n g r a t e and a r e s o l u t i o n o f a t l e a s t 12-b l t t l . In view o f t h i s and t h e p o s s i b l e f u t u r e e x p a n s i o n s , a 32-channe1, 1 2 - b i t d a t a a c q u i s i t i o n sys tem (DAS) h a s i been i n c l u d e d .

8 p p l i C a t i O n .

I n o r d e r t o c a t e r t o t h e needs o f p r e s s u r e p l o t t i n g e x p e r i m e n t s and wake p r e s s u r e s u r v e y s , a 48 p o r t s c a n i v a l v e v i t h a n LVDT t y p e p r e s s u r e s e n s o r h a s also been i n c l u d e d i n t h e sys tem. The LVDT o u t p u t i a a c q u i r e d by t h e DAS.

The t a s k of a u t o m a t i n g t h e e x p e r i m e n t a l p r o c e d u r e s c o u l d be e f f e c t e d by i n t e g r a t i n g t h e above i n d i v i d u a l s u b a y s t e m s w i t h a n a p p r o p r i a t e l y s e l e c t e d programmable c o n t r o l l e r a n d DAS f r o v t h e s e v e r a l h i g h p e r f o r m a n c e , commerb ia l ly a v a i l a b l e , o f f - t h e s h e l f compute r b a s e d s y s t e m s . For example , s y s t e m s l i k e MACSYM, m a n u f a c t u r e d by Analog D e v i c e s , U.S.A. o r DATA TRANSLATE ( D a t a T r a n s l a t e C o r p o r a t i o n , U . S . A . ) [91 e t c . , o f f e r h i g h pe r fo rmance s p e c i f i c a t i o n s and a t t r a c t i v e c a p a b i l i t i 6 s . However, most o f t h e s e modules are o f g e n e r a l p u r p o s e n a t u r e .

e B e s i d e s , t h e r e q u i r e m e n t s i n a wind t u n n e l c a l l f o r s e v e r a l s p e c i a l i s e d a c q u i s i t i o n and c o n t r o l f u n c t i o n s t h a t c o u l d n o t be met e a s i l y by t h e commercia l ly a v a i l a b l e sys tems . For example, t h e i n t e r f a c e s t o t h e 3-D t r a v e r s e mechanism and t h e d i g i t a l manometer a r e t o o s p e c i f i c t o wind t u n n e l a p p l i c a t i o n s . Commercial sys tems g e n e r a l l y do n o t meet t h e s e r e q u i r e m e n t s and o f t e n r e q u i r e e x t e n s i v e t c t i l u r i n g , i f c h o s e n .

A l t e r n a t i v e l y , t h e above t a s k can be implemented by d e s i g n i n g a d e d i c a t e d c o s t e f f e c t i v e system p r o c e s s o r u s i n g t h e e a s i l y a v a i l a b l e advanced m i c r o p r o c e u s o r s . A 1 6- b i t m i c r o p r o c e s s o r system has been d e s i g n e d a n d deve loped t o meet t h e s e r e q u i r e m e n t s . The p r e s e n t c o n f i g u r a t i o n of t h e system i n c l u d e s a CRT t e rmina l f o r usor i n t e r a c t i o n , an i n t e r f a c e t o s t a n d a r d p r i n t e r s f o r h a r d copy o u t p u t s , a MULTIBUS i n t e r f a c e f o r any f u t u r e w p u n s i o n s and t\ f l o p p y d i s c c o n t r o l l e r f o r d a t a a t o r a g e . The b l o c k d iagram of t h e s y s t e m c o n f i g u r a t i o n i s g i v e n i n F i g u r e 1 .

P o w e r f u l hardware w i l l be o f l i t t l e u s e w i t h o u t a p p r o p r i a t e s o f t w a r e . I n many a p p l i c a t i o n s t h e s o f t w a r e deve lopment b e a r s a d i r e c t r e l a t i o n s h i p w i t h t h e a v a i l a b l e ha rdware . T h i s o f t e n l e a d s t o a s i t u a t , i o n wherein an i n t e g r a t e d a p p r o a c h t h a t c a t e r s , w i t h e q u a l emphas i s t o b o t h h a r d w a r e a n d s o f t w a r e a s p e c t s would be needed f o r a s u c c e s s f u l d e s i g n e x e r c i s e .

The s o f t w a r e duvtiloped i n assembly l a n g u a g e i n i t i a l i z e s t h o p e r i p h e r a l I/O c h i p s and t h e i n t e r f a c e s t o t h e i n s t r u m e n t s . The s o f t w a r e f o r u s e r i n t e r a c t i o n , p r o v i d e s a f r i e n d l y env i ronment f o r t h e user. In t h e s e t - u p mode, a s e t of prompt and h e l p messages a l l o w s t h e user t o e a s i l y c o n f i g u r e t h e i n s t r u m e n t s t o t h e s pe c i f i c exp e r i m en tal. n e e d s . The s o f t w a r e t o c o n t r o l t h e e x p e r i m e n t h a s been des igned ts s e q u e n c e t h e c o n t r o l o p e r a t i o n s th rough t h e d r i v e r r o u t i n e s f o r , each o f t h e i n t e r f a c e s , a c q u i r e t h e dn'ta i n r e a l t ime and p r o c e a s i t o n- l i n e . The p r o c e s s e d d a t a i 6 e i t h e r p r i n t e d o r s t o r e d on a f l o p p y i n t h e IBM f o r m a t . The d a t a on t h e f l o p p y c a n a l s o be t r a n s f e r r e d t o t h e mainframe compute r DEC 1090 f o r d e t a i l e d a n a l y s i s , i f needed.

The data p r e s e n t a t i o n i n an e a s y t o i n t e r p r e t fo rm, i s also a n i m p o r t a n t a s p e c t of an i n t e g r a t e d system. The c o l o r coded g r p h i c s t e c h n i u8 deve loped by Winkleman e t . a l . I l O C f , i s a v e r y u q e f u l t o o l f o r f l o w f i e l d v i s u a l i s a t i o n and i n t e r p r e t a t i o n , But as i t r e q u i r s s s o p h i s t i c a t e d computer systems a n d image p r o c e s s i n g s y s t e m s i t becomes u n a f f o r d a b l e f o r s m a l l s c a l e sys tems . However f o r t h u p r e s e n t s y a t e n , g r a p h i c 8 s o f t w a r e has b e e s d e v e l o p e d on a n IBM PC c o m p a t i b l e machine, t o p r e s e n t t h e p r o c e s s e d d a t a in c o l d r

I

ICIASF '17 HL;COHL)-SS

g r a p h i c s con tour p l o t s and v e l o c i t y v e c t o r p l o t s . The package e x p l o i t s t h e c a p a b i l i t i e s of t h e PC and s i m p l i f i e s t h e f low f i e l d a n a l y s i s .

A d e t a i l e d d e s c r i p t i o n o f t h e ha rdware and s o f t w a r e f o r t h e u s e r i n t e r a c t i o n , o v e r a l l e x p e r i m e n t a u t o m a t i o n and d a t a p r e s e n t a t i o n is givun below.

System P r o c e s s o r U n i t :

The b lock d iagram of t h e sys tem p r o c e s s o r u n i t h a s been shown i n F i g u r e 2 . The h e a r t %f t h i s u n i t i s a 1 6- b i t m i c r o p r o c e s s o r a n d numer ic d a t a p r o c e s s o r p a i r , 8086-8087. The 8086, a t h i r d g e n e r a t i o n m i c r o p r o c e s s o r , is c a p a b l e of a d d r e s s i n g u p t o IMb 1113. I t o p e r a t e s on and t r a n s f e r s 1 6 b i t d a t a a t a t i m e . The i n c l u s i o n of 8087 i n t h e d e s i g n * i m p r o v e s t h e p r o c e s s i n g s p e e d phenomena l ly . B e s i d e s , t h e 8087's i n h e r e n t c a p a b i l i t i e s t o o p e r a t e w i t h 8 0 b i t words , p r o v i d e h i g h e r a c c u r a c y . T h e u n i t h a s been d e e i g n e d t o accommodtite t h e n e c e s s a r y memory and o t h e r programmable p e r i p h e r a l c h i p s t o i n t e r f a c e t h e s u b s y s t e m s . N o t a b l e amongest them a r e -

a Programmable p o r i p h o r a l t i m o r s ( I n t e l 825.3) - t o lt,.t.mv utuinp' ~ t i c i I t o q u i k i J d d a t a titid t o g e n e r a t e t l n i r i r I n t e r r u p t s f o r t h e data sampling p u r p a s a s ,

0 Programmable i n t e r r u p t c o n t r o l l e r ( I n t e l 8259) - t o r o c e s s m u l t i p l e i n t e r r u p t 6 ( u p t o 87 from t h e sub- syiit'Fm niodulev and t i n i e r i n t . e r r u p t 3 and draw t o t h e a t t e n t i o n o f t h e p r o c e s s o r when r e q u i r e d (121.

0 U n i v e r s a l synchron ous and a 3 y n c h r on o u s t r a n s m i t t e r / r e c e i v e r Y ( I n t e l 8251) - t o s u p p o r t a C R T t e r m i n a l f o r u s e r i n t e r f a c e , and t o p r o v i d e a programmable a u x i l i a r y RS- 232C communicat ion c h a n n e l [I31 f o r l i n k i n g t h e sys tem t o o t h e r compute r s (a PC h a s been c o n n e c t e d t o t h i s c h a n n e l ) .

A MULTIBUS i n t e r f a c e - t o f a c i l i t a t e any f u t u r e e x p a n s i o n s ( u p t o 6 ) .

F u t u r e e x p a n s i o n p r o v i s i o n s have been s i m p l i f i e d by d e s i g n i n g a MULTIBUS i n t e r f ace t o t h e p r e s e n t sys tem [ 14 ,151 . The bus s t r u c t u r e p r o v i d e s a common e l e m e n t f o r communicat ion between a w i d e v a r i e t y o f sys tem modules which i n c l u d e memory, d i g i t a l and a n a l o g I/O e x p a n s i o n b o a r d s and p e r i p h e r a l c o n t r o l l e r s . It c o m p r i s e s o f 20 d a t a l i n e s ( e q u i v a l e n t t o a n a d d r e s s s p a c e o f 1 Mb,), 1 6 b i - d i r e c t i o n a l d a t a l i n e s , 8 m u l t i l e v e l i n t e r r u p t l i n e s and s e v e r a l bus c o n t r o l ,

t i m i n g and power s u p p l y l i n e s . Modules t h a t U Y ~ t h e MULTIBUS h a v e a m a s t e r - s l a v e r e l a t i o n s h i p . The system p r o c e s s o r , which i s t h e bus m a s t e r , d r i v e s t h e command a n d a d d r e s s l i n e s and c o n t r o l s t h e b u s . The p r c o a n t d e s i g n p r o v i d e s s i x a l o t , a for t h o s l a v e u n i t s , o u t of which t h e f i r s t s l o t h a s been used f o r t h e 32 c h a n n e l a n a l o g d a t a a c q u i s i t i o n s y s t e m . A f l o p p y d i s c c o n t r o l l e r has buun u u u d i n the s u a o n d s l o t .

3- D T r a v e r s e Automat ion :

T r a v e r s e mechanisms may employ e i t h e r stepper motors o r i n d u c t i o u niotars . One of t h e i m p o r t a n t f a c t o r s t h a t i n f l u e n c e t h e c h o i c e o f motors i s t h e c a r r i a g e l o a d . S t e p p e r m o t o r s a r e s u i t a b l e f o r d r i v i n g l i g h t c a r r i a g e s . B u t u o s t o f t e n t h e c a r r i a g e w e i g h t e n c o u n t e r e d i n ti t y p i c a l medium and l a r g e s i z e wind t u n n e l s e t u p i s c o n s i d e r a b l y more. I n such s i t u a t i o n s i n d u c t i o n m o t o r s a r e p r e f e r r e d t o s t e p p e r m o t o r s . S e v e r a l i n t e r e s t i n g p o s s i b i l i t i e s do e x i s t for a u t o m a t i n g t h e probe t r a v e r s e mechanism employ ing i n d u c t i o n motors . The t e c h n i q u e employed t o i n t e r f a c e t h e t r a v e r s e mechanism t o t h o 1 6- b i t p r o c e s s o r makes i t s i m p l e r t o p o s i t i o n t h e p r o b e p r e c i s e l y .

'1'11e t 3 ~ ~ ~ v ~ ? t r s t j mechanism dtnployrtd i n t h a C C l i T h a s t h r e e n o t o r s t o move t h e p robe 9ott a l o n g t h e f l o w d i r e c t i o n (X- d i r e c t i o n ) , 48" a l o n g t h e l a t e r a l d i r e c t i o n ( Y- d i r e c t i o n ) and 12" i n v e r t i c a l d i r e c t i o n ( 2 - d i r e c t i o n ) . I n o r d e r t o k e e p t h e t r a v e r s e mechanism ups t ream e f f e c t s t o a minimum, t h e movement o f t h e c a r r i a g e i n t h e Z- d i r e c t i o n i s l i m i t e d t o 1 ' . To c o v e r t h e c o m p l e t e 2 - d i r e c t i o n t h e p r o b e h o l d e r r o d c a n be changed t o e x t e n d t h e p r o b e movement downwards.

Automat ing t h e above t r a v e r s e mechanism u s i p g t h e m i c r o p r o c e s s o r i n v o l v e s :

( i ) P robe d i s p l a c e m e n t s e n s i n g o v e r a maximum d i s t a n c e o f 96 i n c h e s .

(ii) C o n t r o l l i n g t h e t h r e e motors t o move t h e p r o b e t o t h e r e q u i r e d p o s i t i o n In a l l t h e t h r e e d i r e c t i o n s

(iii) C a r r i a g e l i m i t s e n s i n g a t e i t h e r ends o f e a c h o f t h e three d i r e c t i o n s , and

S o f t w a r e f a r e a s y programming o f t h e ( i v ) module

One o f t h e w e l l known and a c c u r a t e methods f o r p o s i t i o n s e n s i n g i s by u s i n g t h e Gray code s c a l e . But c o n s i d e r i n g t h e

. . I

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56-ICIASF '87 RECORD

s p a n o f t h e p r e s e n t s y s t e m , a 0.01" r e s o l u t i o n w i l l need a 1 4 - b i t Grey code s c a l e . Due t o t h e o b v i o u s d i f f i c u l t i e s i n v o l v e d i n f a b r i c a t i n g a 1 4 - b i t Gray code s c a l e w i t h O.O1ll l i n e s , o f t e n a p o t e n t i o m e t r i c method i s u s e d f o r p o s i t i o n s e n s i n g [ 1 6 ] . However, i n t h e p r e s e n t s y s t e m , i n o r d e r t o a d h e r e t o t h e s i m p l i s t i c d e s i g n g o a l , a n a l t e r n a t e method h a s been d e v e l o p e d . I n t h i s method, p r o v i s i o n s h a v e b e e n made t o counL t h e number o f r e v o l u t i o n s o f t h e l e a d s c r e w o f e a c h moto r w i t h t h e r e q u i r e d r e s o l u t i o n , u s i n g I R o p t i c a l s e n s o r s , MCT- 8 [ 1 7 ] . The number o f r e v o l u t i o n s a r e c o u n t e d u s i n g a s o f t w a r e programmable i n t e r v a l t i m e r (8253) i n t e r f a c e d t o t h e p r o c e s s o r . This a v o i d s t h e p r o b l e m s assoc la t t rd w i t h t h o t i nu log toohniquas. To c o n t r o l t h e 3 m o t o r s , a b i d i r e c t i o n a l mo to r c o n t r o l c i r c u i t r y i s d e s i g n e d u s i n g a s i m p l e l o g i c c i r c u i t a n d r e l a y s . I n o r d e r t o s a f e g u a r d t h e m o t o r s a g a i n s t t h e p rogram and human q r r o r s , f e a t u r e s l i k e , c a r r i a g e l i m i t s e n s i n g , a u t o- m o t o r OFF and i n t e r r u p t t o t h e p r o c e s s o r a r e i n c o r p o r a t e d i n t h e d e s i g n . The e l e c t r o n i c i n t e r f a c e i s shown i n t h e F i g u r e 3 .

The s o f t w a r e f o r t h i s i n t e r f a c e f a c i l i t a t e s c a l i b r a r t i o n o f t h e t r a v e r s e a n d f o r m s a l o o k- u p t a b l e f o r 4 t h e c a l i b r a t i o n c o n s t a n t s . T h i s c a l i b r b t i o n c o m p e n s a t e s f o r t h e e r r o r s d u o t o t h e i n e r t i a o f t h e i n d u c L i o n m o t o r s , m e c h a n i c a l g e a r s a n d a l s o t h e m i s a l i g n m e n t e r r o r s i n e a c h a x i s .

F o r p r o b e p o s i t i o n c o n t r o l t h e s o f t w a r e a l l o w s t h e u s e r t o d e f i n e t h e s c a n volume i n t h e t e s t s e c t i o n a n d o t h e r p a r a m e t e r s . The f e a t u r e s o f f e r e d by t h i s a o f t w g r e i n c l u d e -

P r o b e movement M A N U A L / A U T O M A T I C s e l e c t i o n s .

d i r e c t i o n s . e Scan limits on e a c h o f t h e t h r e e

I, Number o f s e g m e n t s w i t h i n t h e l i m i t s i n e a c h d i r e c t i o n .

D i f f e r e n t g r i d s i z e s f o r d i f f e r e n t s e g m e n t s w i t h i n t h e s c a n l imits .

O t h e r o p t i o n s i n c l u d e

I, D e f a u l t g r i d s e l e c t i o n .

G r i d s i z e d y n a m i c a l l y a l t e k a b l e w i t h o u t d i s c o n t i n u i n g t h e e x p e r i m e n t .

a C a l i b r a t i o n and f o r m i n g a new l o o k- u p t a b l e f o r t h e c o r r e c t i o n t e r m s t o

6- Channel D i g i t a l Manometer :

The i n s t r u m e n t is based o n d i g i t a l r e n d i n g o f t h e d i s t a n c e between t h e l i q u i d l e v e l s i n a U-tube manometer by m e c h a n i c a l l y t r a v e r s i n g a c a r r i a g e t o w h i c h a r e f i x e d a p a i r o f l i q u i d l e v e l s e n s o r s . The c a r r i a g e t r a v e r s e i s s e n s e d by a d i s t a n c e s e n s o r which p r o d u c e s a p u l s e p e r O . l m m movement o f t h e c a r r i a g e . T h e s e p u l s e s a r e c o u n t e d by a f r e e r u n n i n g c o u n t e r . The m i c r o p r o c e s s o r r e a d s t h e l e v e l s e n s o r s ' s t a t u s and a t t h e i n s t a n t s o f t h e c a r r i a g e c r o s s i n g t h e l i q u i d l e v e l m e n i s c u s , s a m p l e s t h e f r e e r u n n i n g c o u n t e r . The r e a d i n g s a r e s t o r e d i n t h e s y s t e m memory. Once t h e s e r e a d i n g s a r e t a k e n f o r a l l t h e c h a n n e l s , t h e d i f f e r e n c e in ruadingu fLJr each o f t h u nilrnornetora i e computed by t h e m i c r o p r o c e s s o r a n d t h e d a t a i s a v a i l a b l e f o r p r i n t i n g o r any f u r t h e r p r o c e s s i n g .

A s e m i a u t o n i a t i c v e r s i o n o f t h i s i n s t r u m e n t , i n wh ich T T L h a r d w a r e h a s b e e n u s e d t o r e a d t h e l i q u i d column h e i g h t in a U- tube h a s b e e n d e v e l o p e d i n 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 , I I S c [ I 81. However, i n t h i s p r o t o t y p e i n s t r u m e n t , t h e motor c o n t o l i s m a n u a l a n d a cam mechanism i s used f o r t h e c a r r i a g e movement. I n v i ew o f t h e r e l a t i v e l y l a r g e r a n g e o f movement r e q u i r e d f o r t h e p r e s e n t i n s t r u m e n t , t h e m e c h a n i c a l d e s i g n o f t h i s p r o t o t y p e h a s been changed c o n s i d e r a b l y i n t h e new I n s t r u m e n t t o f a c i l i t a t e r e l i a b l e o p e r a t i o n u n d e r t h e c o n t r o l o f t h e m i c r p r o c e s s o r .

T h e m a c h a n i c a l c o n s t r u c t i o n a n d t h e e l e c t r o n i c s i n t e r f a c e t o t h e p r o c e s s o r h a v e been shown i n t h e F i g u r e s 4 1791. The l e n s e e f f e c t o f a g l a s i i t u b e f i l l e d w i t h a l c o h o l i s c o n v e n i e n t l y made u s e o f , t o s e n s e t h e l i q u i d l e v e l u s i n g I R o p t i c a l s e n s o r s (MCT-8). The d i s t a n c e t r a v e r s e by t h e c a r r i a g e i s s e n s e d as a f u n c t i o n o f t h e moto r d r i v e s o t h e r e a d i n g s a r e i n d e p e n d e n t 04 t h e motor s p e e d v a r i a t i o n s . A l t h o u g h t h e p r e s e n t d e s i g n i n c l u d e s o n l y 6 - c h a n n e l s , w i t h minor e x t e n s i o n s , t h e i n t e r f a c e c a n be implemented f o r a s many c h a n n e l s a s r e q u i r e d w i t h a s u i t a b l e m e c h a n i c a l s e t - u p .

The r e s o l u t i o n o f t h e s y s t e m i s O . l m m of l i q u i d column. With t h e p r e s e n t mechan i sm, i t may be n o t e d t h a t t h e a c c u r a c y o f t h e r e a d i n g s i s i n d e p e n d e n t of t h e s p e e d v a r i a t i o n s o f t h e m o t o r . T h i s e l i m i n a t e s t h a need f o r a p r e c i s i o n m o t o r a n d s p e e d c o n t r o l c i r c u i t r y . The a c c u r a c y o f t h e u n i t i s f o u n d t o be b e t t e r t h a n 0.2mm. The r a n g e o f t h e i n s t r u m e n t is +1000mm. The p r e s e n t d e s i ne r e q u i r e s 2 . 5 s e c t o a c q u i r e one s e t o f s a m p l e s .

.. .. . , . ?

ICLASF '87 HECOKD-57

I n e t r u m u n t a t i o n f o r Force Moasurumente and Preasure 3urvey0 ;

F o r c e meaaurement i n s t r u m e n t a t i o n h a s buan implemuntud t h r o u g h CI u t r i i i ng:’*ugu

p o s i t i o n encoder and a motor c o n t r o l i n t e r f a c e h a s been d e s i g n e d t o c o n t r o l t h e model on t h e new mounting r i g d e s i g n e d by a s e p a r a t e group [ r C O l .

A 48- por t s c a n i v a l v e h a s been i n t e r f a c e d t o t h e s y s t e m p r o c e s s o r a s a p a r t of t h e p r e s s u r e s u r v e y i n s t r u m e n t a t i o n .

b a l a n c e and a 32-channe l a n a l o g UAS. A

6-Component S t r a i n Gauge B a l a n c e :

For a c c u r a t e f o r c e measurements , 6 component s t r a i n g a u g e b a l a n c e h a s been a c q u i r e d . It h a s e i g h t s t r a i n gauge b r i d g e s t o i n d i c a t e a l l t h e s i x components of fo rce /moments . These e i g h t s t r a i n gauges p r o v i d e e l e c t r i c a l s i g n a l s i n t h e r a n g e o f 22 rnv f u l l s c a l e w i t h e x c i t r r t i o n v o l t a g e o f 4 V d c . T h e s t r a i n g a u g e b a l a n c e h a s been c a l i b r a t e d f o r use i n t h e p r e s e n t sys tem [213.

32-Channel Data A c q u i s i t i o n System :

The 32- channe l d a t a n c q u i s i t f o n s y s tern ( e x p a n d a b l e t o 256 c h a n n e l s ) h a s been shown i n F i g . . .. It c o n s i s t s o f 8 c h a n n e l p r e a m p l i f i e r s which a r e t a i l o r e d t o r e a d t h e s i g n a l s from t h e s t r a i n gauge b a l a n c e , a 32 c h a n n e l m u l t i p l e x e r , a g a i n s e l e c t a b l e i n s t r u m e n t a t i o n a m p l i f i e r , a sample and h o l d c i r c u i t and a b u f f e r e d 12- b i t s u c c e s v i v e a p p r o x i m a t i o n a n a l o g t o d i g i t a l “ c o n v e r t e r . The t i m i n g s i g n a l s t o s e q u e n c e t h e o p e r a t i o n o f t h e s e b l o c k s have been p r o v i d e d by a c o n t r o l l e r c i r c u i t r y . T h i s module i s c o n f i g u r e d f o r memory mapped I / O and t h e a d d r e s s is jumper s e l e c t a b l e . The module h a s bean i n t e r f a c e d t o t h e s y s t e m p r o c e s s o r t h r o u g h i t s MULTIBUS. The b l o c k diagram o f t h e DAS is g i v e n i n F i g u r e 5.

Expansiori u p t o 256 c h a n n e l s may be e f f e c t e d by u t i l i z i n g t h e expander ’

c i r c u i t r y w i t h minimum a d d i t i o n a l ha rdware o f p r e a m p l i f i e r s and m u l t i p l e x e r s . O t h e r h a r d u a r e f e a t u r e s i n c l u d e s i g n a l c o n d i t i o n i n g a t t h e i n p u t end i n t h e s h a p e o f ha rdware l ow p a s s f i l t t i r s , nnd i n p u t o v e r v o l t a g e p r o t e c t i o n . I n i t s c p n f i g u r a t i o n , t h e 8 l o w i n p u t c h a n e e l s a c c e p t i n p u t s i n t h e r a n g e o f 2 2mv w h i l e t h e h i g h l e v e l i n p u t s ~ ~ l l o w i n p u t s o f +5v f u l l s c a l e . The s e t t l i n g t i m e s o f e z c h component p u t t o g e t h e r w i l l amount t o 38 u a e c when t h e o v e r a l l a m p l i f i e r g a i n i s 1 , b u t w i l l i n c r e a s e u p t o 100 u D ~ J C f o r a maximum gtiin o f 1000. These f i g u r e s imply

ri

t h u t :;uolpLiirlC: r * t l t u u u p t u 10 KJIZ Ul‘d

c ti i ev Z I b 1 o w ti i 1 u o p u i-.~ 1. i r i g th v ti III 1) 1 i i’ 1 u r u u t iiiuximiirr guJ.11. ‘The 1 2 bit dt i tu a c q u i s i t i o n s y s t e m p r o v i d e s an o v e r a l l u o c u r t i c y at. 0 .1%. T h i i 3 w o d u l u hus beon w i r e d f o r i n t a r r u p t modu 01’ o p u r u t l O r i i i r t h e s y s t e m .

The a n a l o g d a t a a c q u i s i t i o n s o f t w a r e r r l l aw3 tdhu i IBoc t o o o n f i p u r o t h e module t o t h e s p e c i f i c requiremari t of the e x p e r i m e n t . The c h a n n e l numbers t o be sampled , bounds on i n p u t l e v e l s , s c a n r a t e and number o f samples f o r a v e r a g i n g a r e programmable. The a c c u r a c y o f t h e a c q u i r e d d a t a i s f u r t h e r improved by a u t o m a t i c d r i f t and g a i n e r r o r c a n c e l l a t i o n s . Once t h e module i s d e f i n e d f o r an e x p e r i m e n t , i n o r d e r t o a c q u i r e t h e d a t a , t h e s y s t e m p r o c e s s o r i s s u e s a command t o i n i t i a t e t h e d a t a c o n v e r s i o n . Once t h e d a t a c o n v e r s i o n i s comple te , t h e d a t a a c q u i s i t i o n System w i l l i n t e r r u p t t h e p r o c e s s o r s o t h a t t h e p r o c e s s o r may r e a d t h e c o n v e r t e d d a t a . D u r i n g t h e c o n v e r s i o n t ime, t h e p r o c e s s o r can e i t h e r p r o c e e d w i t h o t h e r t u s k s a s s i g n e d , o r wait for t h e c o n v e r s i o n t o cornplete . T h i a f e a t u r e c o n t r i b u t e s t o f u r t h e r processor t i m e s a v i n g s when t h e module i s used i n t h e t i m e r i n t e r r u p t mode. When t h e d a t a a c q u i s i t i o n i s completct , t h e i n p u t l e v e l s on t h e s e l e c t e d c h a n n e l s a r e compared a g a i n s t t h e s e t l i m i t s .

S c a n i v a l v s Pressure Measurement System :

P r e s s u r e s u r v e y expur lments a t t h e CCWT r e q u i r e m u l t i p l e p r e s s u r e measurement from a r a k e o f p i t o t t u b e s t r a v e r s e d i n a v e r t i c a l p l a n e , i n t h e wake o f the m o d e l , o r from t h e t a p p i n g s drawn from t h e modo l s u r f a c e . I n t h e sys tem, a 48-port s c a n i v a l v e (model 4Sd3) e n a b l e s t h e s e measurements t o be made u s i n g a s i n g l e p r e s s u r e t r a n s d u c e r . F i g u r e 6 shows t h e b l o c k diagram o f t h e e l e c t r o n i c i n t e r f a c e t o t h e s y s t e m p r o c e s s o r . I n o r d e r t o o b t a i n t h e por t ‘ .numbers p r e c i s e l y , a 6-bit o p t i c a l s h a f t p o s i t i o n Gray e n c o d e r h a s been used on t h e s c a n i v a l v e motor s h a f t . O p t i c a l Gray e n c o d e r h a s been d e s i g n e d u s i n g s i x s e t s of I R emit ter and s e n s o r p a i r s ( M C T - 8 ) mounted a c r o s s an o p t i c a l c i r c u l a r Gray code d i s c . The Gray c o d e p a t t e r n on t h e d i s c w i t h 48 l e v e l s , has been made u s i n g ‘a c o o r d i n a t o- g r a p h t o e n s u r e h i g h p r e c i s i o n , A b i - d i r e c t i o n a l motor d r i v e c i r c u i t r y htls been d e s i g n e d and d e v e l o p e d ( u s i n g t r a n s i s t o r s ) t o c o n t r o l t h e s c a n i v a l v e motor o p e r a t i o n . Based on t h e d i r e c t i o n arid ON/OFF i n p u c s t o t h i s b l o c k , t h e c i r c u i t d r i v e s t h e motor i n t h e u p p r o p r i a t e d i r e c t i o n , and t h u s p r o v i d e s a random a c c e s s o f 8 p a r t i c u l a r p o r t .

#--ICIASF ‘117 HECOHD

Th B pr i u u in u L I (I 111 u J, L 1 p 1 w x IJ J o u L pu L i d f e d t o a LVDT t y p e p r e s s u r e t r a n s d u c e r which p r o v i d e s a +5v o u t p u t f u l l sca le w i t h a n a c c u r a c y o f 0 .1% o v e r a r a n g e of 0 t o 0.1 p s i . Channel 10 o f t h e oarliur d e s c r i b e d d a t a a c q u i u i t i o n s y Y tem h a s be en used t o r e a d t h e a n a l o g o u t p u t o f t h i s t r a n s d u c e r . As a r e s u l t , a l t h o u g h t h e s a m p l i n g r a t e on e a c h c h a n n e l o f t h e d a t a a c q u i s i t i o n aystem is u p t o 10 KHz, t h e s a m p l i n g r a t e of t h e p o r t s is l i m i t e d t o 0.4Hz. T h i s l i m i t a t i o n i s p r i m a r i l y due t o t h e maxiarum motor s p e e d of t h e e c a n i v a l v e u s e d , which i s 3 rpm.

The s o f t w a r e t o c o n t r o l t h e p r e s s u r e s u r v e y d a t a a c q u i s i t i o n o f f e r s two modes o f s c a n i v a l v e o p e r a t i o n . I n t h e f i r s t mode, s c a n i v a l v e is o p e r a t e d i n s e q u e n t i a l p o r t s e l e c t i o n . I n t h i s mode t h e p o r t numbera t o be sampled and t h e sampl ing r a t e on e a c h p o r t a r e s e l e c t a b l e by t h e user b e f o r e s t a r t i n g t h e e x p e r i m e n t . When t h i s mode of o p e r a t i o n i s s e l e c t e d , t h e sys tem homes t h e s c a n i v a l v e t o i t s p o r t 0. Then t h e s c a n i v a l v e motor i s a c t i v a t e 6 f o r B c o n t i n u o u s o p e r a t i o n and t h e p o r t numbers a r e a o n t i n u o u a l y snmpled. The d a t a is a c q u i r e d w i t h i n t h e d w e l l t i m e , when t h e p o r t number c o r r e s p o n d s t o t h e p o r t s t o be sampled. The second mode p r o v i d e s a random a c c e s s o f a p a r t i c u l a r p o r t . For t h i s mode a l s o , se lec tcbb lp p a r a m e t e r s a re t h e same. However, i n t h i s mode, t h e s c a n i v a l v e c u r r e n t p o r t number i s r e a d and compared a g a i n s t t h e p o r t t o be sampled. T h e p r o c e s s o r d e t e r m i n e s t h e d i r e c t i o n i n which t h e motor h a s t o be r o t a t e d t o r e a c h t h e nex t p o r t from which t h e d a t a h a s t o be r e a d . Based on t h i s , t h e p r o c e e s o r c o n t r o l s t h e motor a p p r o p r i a t e l y t h r o u g h t h e i n t e r f a c e . On a c c e s s i n g t h e r e q u i r e d p o r t , t h e d a t a i s a c q u i r e d a8 p e r t h e s e l e c t e d mode.

Software Design :

The s o f t w a r e d e s i g n e d f o r o v e r a l l s y s t e m o p e r a t i o n may be g rouped i n t o t h r e e p a r t s , i.e., ( i ) s y s t e m s s o f t w a r e , (ii) u s e r i n t e r a c t i o n s o f t w a r e , ( i i i ) e x p e r i m e n t d r i v e r s o f t w a r e and ( i v ) d a t a p r e s e n t a t i o n s o f t w a r e . The s o f t w a r e , e x c l u d i n g f o r t h e d a t a p r e s e n t -a t i o n h a s been deve loped i n 8086 a s s e m b l y l angauago . The s o f t w a r e f o r t h e d a t a p r e s e n t a t i o n has been deve loped on a n I B M PC c o m p a t i b l e machine s o t h a t t h e c o l o r g r a p h i c s c a p a b i l i t i e s o f t h e PC c o u l d be e x p l o i t e d . B e s i d e s i t would ease t h e n e c e s s a r y m o d i f i c a t i o n s t o t h e a p p l i c a t i o n s o f t w a r e , which a r e o f t e n r e q u i r e d from time t o time.

The u s e r i n t e r a c t i o n s o f t w a r e f o r s e t t i n g - u p t h e e x p e r i m e n t a t i o n p r o v i d e s a f r i e n d l y i n t e r f a c e , which e n a b l e s t h e u s e r

Lu progr.trei t h 3 r iyi tam f o r his a x p r i m a n t . D u r i n g t h i s e x e r c i s e , t h e s o f t w a r e e n s u r e s e r r o r - f r e e p a r a m e t e r s e l e c t i o n t h r o u g h a s e t o f h e l p messages and solf e x p l a n a t o r y q u u r i i i u . Onto l h o tlyutum i u l l ~ e t " f o r t h e e x p e r i m e n t , t h e c o n f i g u r a t i o n o f t h e e x p e r i m e n t i s s t o r e d on t h e f l o p p y a n d t h e e x p e r i m e n t d r i v e r t a k e s- o v e r t h e c o n t r o l t o i n i t i a t e t h o actuci l conduc t o f t h e e x p e r i m e n t . T h i s p a r t i n i t i a l i z e s and c o n f i g u r e s t h e subsystems i n s t r u m e n t a t i o n , and p e r f o r m s r e a l - t i m e d a t a a c q u i s i t i o n and c o n t r o l . The d a t a i s s t o r e d i n t h e f l o p p y d i s c . The s o f t w a r e p r o c e s s e s t h e d a t a o n - l i n e and a l s o r e s p o n d s a p p r o p r i a t e l y t o t h e i n t e r r u p t s f rom t h e s u b s y s t e m s i n s t r u m e n t a t i o n . The s o f t w a r e a l s o c o n t i n u o u s l y u p d a t e s t h o d i s p l a y of t h e s t a t u s i n f o r m a t i o n on t h e CRT t e r m i n a l . The u s e r may i n t e r r u p t t h e p r o c e s s , t h r o u g h t h e t e r m i n a l k e y b o a r d , e i t h e r t o h o l d / t e r m i n a t e t h e e x p e r i m e n t o r t o modi fy t h e s e t - u p i n f o r m a t i o n . On s u c c e s s f u l c o m p l e t i o n o f t h e e x p e r i m e n t , t h e c o n t r o l i s t r a n s f e r e d t o t h s d a t a p r e s e n t a t i o n e o f t w a r e .

The d a t a p r e s e n t a t i o n m e t h o d o l o g i e s h a v e been f ramed based o n t h e common e x p e r i m e n t s conduc ted i n t h e CCWT. These have been sub- div ided i n t o t h r e e c a t o g o r i e s i . e . , f l o w f i e l d da ta p r e s e n t a t i o n , f orce/rnoment d a t a p r e s e n t a t i o n and p r e s s u r e s u r v e y d a t a p r e s e n t a t i o n . The exper iment d r i v e r s o f t w a r e s t o r e s t h e d a t a on a f l o p p y , which c a n be r e a d i l y p r e s e n t e d i n t h e form o f t a b l e s . The d a t a p r e s e n t a t i o n i n t h e fo rm o f p l o t s c a n be o b t a i n e d e i t h e r t h r o u g h t h e mainframe computer DEC s y s t e m 1090 o r t h r o u g h an IBM PC c o m p a t i b l e machine. The i n t e r a c t i v e n a t u r e o f t h e p a c k a g e s d e v e l o p e d improves t h e u s e r ' s comprehens ion o f a l a rge volume of d a t a by a c h o i c e o f c o l o r s / p a t t e r n s ,

i ) Sya tems software :

The sys tem s o f t w a r e i n i t i a l i z e 8 t h e p e r i p h e r a l i n t e r f a c e s and submodules f o r a p p r o p r i a t e mode o f o p e r a t i o n . It also i n i t i a l i z e s t h e i n t e r r u p t v e c t o r t a b l e f o r i n t e r r u p t s e r v i c e h a n d l e r . The s o f t w a r e a l s o e n s u r e s a p p r o p r i a t e p r o c e e s o r r e s p o n s e f o r i n t e r f a c e s o f t w a r e and t h e a p p l i c a t i o n s o f t w a r e .

ii) User interaction software :

The h a r d w a r e h a s been d e s i g n e d , as d e s c r i b e d e a r l i e r , t o c a t e r t o a wide s p e c t r u m o f e x p e r i m e n t s l i k e i ) f l o w f i e l d s u r v e y , i i ) force/moment measurements and iii) p r e s s u r e s u r v e y s , where in the r a n g e o f s e v e r a l p a r a m e t e r s , l i k e t h e mode o f o p e r a t i o n o f t h e s u b modules, ' d a t a

ICliASF '87 HKCOHD - 59

n c q u i i i t i o n s p o c i f i c a t i o n u u t c . , w o u l d v a r y . Hence, f o r any t ; p a c i F i c e x p e r i m e n t a t i o n needed by t h e u s e r , t h e r e i s a need t o r e - c o n f i g u r e , by s o f t w a r e , t h e i n d i v i d u a l sub- sys tems and t h e s o f t w a r e- g e n e r a t e d t ime- markers . The p r e c i s e r o l e of t h e u s e r - i n t e r f a c e s o f t w a r e i s t o a c q u i r e t h e s e t - u p d a t a f r o m t h e u s e r t h r o u g h a s e t of q u e r i e s and use i t t o c o n f i g u r e t h e sub- sys tems a c c o r d i n g l y .

The q u e r i e s a r e s e l f - e x p l a n a t o r y and e a s i l y u n d e r s t a n d a b l e . The p e r m i s s i b l e answers, p a r a m e t e r r a n g e e t c . a r e d i s p l a y e d a l o n g w i t h e a c h q u e r y . I n o r d e r t o ensure e r r o r - f r e e s e t - u p e n t r i e s , t h e s o f t w a r e a c c e p t s t h e p a r a m e t e r s t h a t a r e a l l o w a b l e and i n t h e c a s e o f i n c o r r e c t e n t r i e s , an e r r o r message i s f l a s h e d on t h e CRT t o warn t h e u s e r and r e q u e s t s f o r a p e r m i s s i b l e answer . F i g u r e s 7 d e p i c t s t h e s e l e c t i o n o f t h e measurement o p t i o n s . F o r t h i s s e l e c t i o n , t h e u s e r i s a l s o prompted w i t h t h e e x p e c t e d a n s w e r s . Once t h e r e q u i r e d e x p e r i m e n t i s s e l e c t e d , t h e system draws t h e u s e r ' s a t t e n t i o n t o v e r i f y t h e e n t r i e s ( F i g u r e 7 ) . The u s e r 1s a l l o w e d t o make any a l t e r a t i o n s t o h i s s s l a c t i o n . On c o n f i r m i n g t h e o u l u c t i o n , d e p e n d i n g on t h e e x p e r l m e n t e s u l a c t u d , q u e r i e s f o r c o n f i g u r i n g t h o i n d i v i d u t i i e x p e r i m e n t s a r e i n i t i a t e d . For example,- t o e n t e r t h e s e t - u p p a r a m e t e r s f o r t h e DAS, t h e ayst4em d i s p l a y s t h o d t t f a u l t p a r a m e t e r s r e q u i r e d f o r t h e d a t a a c q u i o i t i o n and t h e mode o f r t i w d a t a o u t p u t . F o r t h u convan iuncu of' L h u u t l u r , t h e c u r s o r , l s p l a c e d a g a i n t i t e a c h of tho p a r a m e t e r s 'on t h e s c r e e n , i n t h e o r d e r shown, a n d waits f o r t h e u s e r r e s p o n s e . The e e l e c t i o n o f t h e r e s p e c t i v e p a r a m e t e r ' s v a l u e i s f u r t h e r s i m p l i f i e d by showing t h e a d m i s s i b l e r e s p o n s e / r a n g e a t t h e bot tom of t h e s c r e e n .

S i m i l a r p r o c e d u r e h a s been a d o p t e d t o c o n f i g u r e e x p e r i m e n t s f o r f l o w f i e l d survey and t h e p r e s s u r e s u r v e y s . For f l o w f i e l d survey, t h e u s e r h a s t o s e l e c t t h e mode of t h e probe t r a v e r s e c o n t r o l , e i t h e r Manual o r Automat ic . T h i s i s f o l l o w e d by d e f i n i n g t h e p robe t r a v e r s e r a n g e a n d t h e g r i d s i z e i n t h e t h r e e d i r e c t i o n s . B e s i d e s , t h e p r e s s u r e d a t a a c q u i s i t i o n t h r o u g h t h e 6- channe l d i g i t a l manomster has t o be c o n f i g u r e d . I n t h e c a s e of t h e p r e s s u r e s u r v e y e x p e r i m e n t a t i o n , t h e u s e r is r e q u e s t e d t o s e l e c t t h e p o r t numbers ( o f t h e 48 a v a i l a b l e p o r t s on t h e s c a n i v a l v e ) t o be sampled , t h e s a m p l i n g p e r i o d , and t h e number of samples f o r a v e r a g i n g . I n t h i s f a s h i o n , t h e u s e r i n t e r a c t i o n f o r c o n f i g u r i n g t h e e x p e r l m a n t a hcls besn made s e l f - e x p l a n a t o r y a n d s i m p l e .

The above u s e r i n t e r a c t i o n s o f t w a r e

f o r . t t r t t y u t - u p has been deve loped i n t h e

t h e b a s i c c e n t r a l p r o c e s s o r board and t h e a s s o c i a t e d h a r d w a r e h a v e been i n t e r f a c e d t o a n 1BbI PC compcl t ib lc i i ~ i c h i n u , n s u p a r t l t c u z e r i n t e r a c t i o n r o u t i n e w h i c h u s u s IBM PC a s a s t a n d- a l o n e c o l o r t e r m i n a l h a 5 a l s o b e e n deve loped . The p h o t o g r a p h p r e s e n t e d i n F i g u r e 7 i s f r o m t h e I B M PC t e r m i n a l , which hau an in iproved a p p e a r a n c e a s compared t o t h e b l a c k a n d w h i t e t e r m i n a l d e v e l o p e d as p a r t o f t h e sys tems hardware .

iii) Exper iment D r i v e r :

'I'he e x p e r i m e n t d r i v e r p a r t o f t h e s o f t w a r e c o n f i g u r e s a n d c o n t r o l s t h e s u b s y s t e m s , based on t h e p a r a m e t e r 8 p r o v i d e d by t h e u s e r , a n d a c q u i r e s d a t a i n r e a l t i m e , The s o f t w a r e a l so m o n i t o r s t h e h e a l t h of t h e i n s t r u m e n t s a n d c o n t i n u o u s l y u p d a t e s t h e s t a t u s o f t h e e x p e r i m e n t s on t h e C R T s c r e e n . The u s e r may a l s o i n t e r r u p t t h e p r o c e s s o r a t any s t a g e o f t h e e x p e r i m e n t , v iew t h e s o t - u p p a r a m e t e r s t h r o u g h s i m p l e commands and a l t e r them f o r t h e r e s t o f t h e e x p e r i m e n t . The e x p e r i m e n t d r i v e r s o f t w a r e f o r each o f t h e a x p e r l m e n t v i s d i s c u s s e d balow.

For f o r c e measuremunta , d e p e n d i n g o n t h e user s e t p a r a m e t e r s , t h e i n t h e manual mode, sys tem prompts t h e u s e r t o s e t t h e model p o s i t i o n i n t h e r e q u i r e d p i t c h a n d yaw. The u s e r i s t h e n r e q u i r e d tQ s e t t h e m o d u l p o s i t i o n and p r e s s ' r e t u r n ' on t h e k u y b o u r d ( I n t h u uu t ,on i t i L io modu t h u etiiiie w i l l btt d o n e by t he t lyutum). Whuri t h e ktly i s p r e s s e d , t h e s y s t e m i n i t i a t e s A / D c o n v e r s i o n o n e a c h of t h e a n a l o g c h a n n e l s by f i r s t i n i t i a l i z i n g t h e t i m e r f o r s a m p l i n g p e r i o d and t h e n by issuing a s t a r t c o n v e r s i o n command t o t h e d a t a a c q u i s i t i o n sys tem. When t h e a n a l o g t o d i g i t a l c o n v e r s i o n i s c o m p l e t e , t h e DAS i n t e r r u p t s t h e p r o c e s s o r S O t h a t t h e c o n v e r t e d d a t a i s r e a d by t h e p r o c a s s o r . The p r o c e s s o r t h a n l o o k s f o r t h e a c q u i r e d d a t a , and i f t h e d a t a is a v n i l a b l e i n t h e memory, i t w i l l be p r o c e s s e d . A t t h e i n t e r v a l s o f t h e sampling p e r i o d , t h e t i m e r i n t e r r u p t s t h e p r o c e s s o r t o a c q u i r e t h e d a t a p r e c i s e l y a t t h e s a m p l i n g i n t e r v a l s . The p r o c e s s o r k e e p s t r a c k o f t h e number o f s a m p l e s a c q u i r e d a n d when t h i s number r e a c h e s t h e s a t v a l u e , t h e t ime r i n t e r r u p t i s d i s a b l e d and t h e above p r o c e s s c o n t i n u e s u n t i l t h e da ta c o l l e c t i o n a t a l l t h e r e q u i r e d ang les i s c o m p l e t e .

When f l o w f i e l d s u r v e y i s s e l e c t e d , t h e d r i v e r s o f t w a r e i n i t i a l i z e s t h e 3- D t r a v e r s e i n t e r f a c e module f o r a u t o m a t i c probe p o s i t i o n i n g . T h u probo i u

i n f o r m a t i o n a t t h e t o p l e f t c o r n e r o f t h e

usuuf l l I ,Ly LUIl~ULLgU 01' t i08L. I I l > W U V l ~ I . , CiJ I I U W

p o s i t i o n e d u s i n g t h e user set-up


f i r s t c r o s s - s e c t i o n a l p l a n e i n t h e t e s t s e c t i o n . Depend ing on t h e s t e p s i z e ( g r i d s i z e ) , i n e a c h o f t h e t h r e e d i r e c t i o n s , t h e p r o b e i s moved i n t h e l a t e r a l d i r c e t i o n ( Y - d i r e c t i o n ) i n t h e c r o s s - f l o w p l a n e . A t e a c h s t e p , a f l o w s e t t l i n g t i m e o f a b o u t 1 s e c o n d i s a l l o w e d a n d t h e n t h e d a t a a c q u i s i t i o n i s e f f e c t e d t h r o u g h t h e 6- c h a n n e l manometer. When t h e p r o b e rurraohuu thrr l u r i t gr*Itl pui . r i t r i l o n y l,tIiAt, l i n e , t h e p r o b e i s raoved t o t h e n e x t s t e p i n t h e v e r t i c a l d i r e c t i o n (downwards) a n d t h e p r e s s u r e d a t a i s c o l l e c t e d . The d i r e c t i o n o f t h e p r o b e movement a l o n g t h e l a t e r a l p l a n e is t h e n r a v u r s u d . T h i ~ i p r o c e s s i s c o n t i n u e d t o c o m p l e t e t h e s c a n n i n g o f e a c h c r o s s - f l o w p l a n e . A f t e r c o l l e c t i n g t h e f l o w f i e l d d a t a f rom t h e f i r s t p l a n e , t h e p r o b e t r a v e r s e i s moved in t h e a x i a l d i r e c t i o n t o p l a c e t h e p r o b e i n s u c c e s s i v e c r o s s - f l o w p l a n e s and t h e data c o l l . e c t i o n i s c o m p l e t e d . The p r e s s u r e d a t a f rom t h e 5- ho le p r o b e t h r o u g h t t h e manometer s u b s y s t e m i s a c q u i r e d i n i n t e r r u p t mode. T h i s a p p r o a c h makes t h e b e s t u s e o f p r o c e s s o r t i m e a n d f a c i l i t a t e s o n - l i n e d a t a r e d u c t i o n w h i l e t h e d a t a i s a c q u i r e d ' .

I n t h e c a s e o f p r e s s u r e s u r v e y e x p e r i m e n t s , t h e s c a n i v a l v e motor i s c o n t r o l l e d t o a c c e s s t h e r e q u i r e d p o r t s , i n s u c c e s s i o n , as p e r user r e q u i r e w n t s . A t e a c h o f t h e r e q u i r e d p o r t s , t h e p r e s s u r e d a t a f rom t h e LVDT p r e s s u r e s e n s o r i s a c q u i r e d t h r o u g h t h e a n a l o g DAS a a d e s c r i b e d a b o v e .

Once t h o da ta a c q u i s i t i o n f o r t h e s e l e c t G d e x p e r i m e n t a i s c o m p l e t e d , t h e d a t a p r o c e s s i n g a n d p r e s e n t a t i o n s o f t w a r e r e c e i v e s t h e c o n t r o l . T h i s p a r t h a s been d e s c r i b e d i n t h e n e x t s e c t i o n .

The a c q u i r e d d a t a , d e p e n d i n g on u s e r r e q u e s t s , h a s t o be bound c h e c k e d , a v e r a g e d a n d n o r r n a l i s e d . T h i s p r o c e s v i n g i s c a r r i e d o u t by t h e c e n t r a l p r o c e s s o r . I f t h e d a t a a c q u i s i t i o n r a t e s a r e l o w , t h e p r o c e e s o r would h a v e s u f f i c i e n t time t o c o m p l e t e this p r o c e s s i n g w h i l e t h e d a t a i s b e i n g a c q u i r e d . However, i f t h e i n t e r v a l be tween t h e a c q u i r e d d a t a i s small , t h e p r o c e s s o r would c o n t i n u e t o c o m p l e t e ' t h e p r o c e s s i n g a f t e r c o m p l e t i o n o f t h e d a t a a c q u i s i t i o n . The a c q u i r e d and t h e p r o c e s s e d d a t a a r e t h e n w r i t t e n i n t h e a u x i l l a r y s t o r a g e i n a f o r m a t a c c e p t a b l e t o IBM PC c o m p a t i b l e m a c h i n e s f o r f u r t h e r p r o c e s s i n g a n d p r e s e n t a t i o n .

iv) Data P r e s e n t a t i o n :

T h i s p a r t of t h e s o f t w a r e t h a t r u n s on t h e PC h a s t h e f o l l o w i n g f u n c t i o n s t o p e r f o r m on t h e a c q u i r e d d a t a .

( i ) R e d u c t i o n o f ae rodynamic q u a n t i t i e s

( i i) G r a p h i c a l - - V e l o c i t y v e c t o r a n d c o n t o u r c o l o u r maps o f t h e measu red d a t a ,

a n d ( i i i) F o r c e and p r e s s u r e d i s t r i b u t i o n

Uuta p r o c e s v i t i g soPtwt l re f o r f o r c e m e a s u r e m e n t s i n c l u d e s c o m p u t a t i o n o f t h e a e r o d y n a m i c c o e f f i c i e n t s . The l o c a l f l o w a n g l e and t h e v e l o c i t#y magni tude h a v e been o b t a i n e d from t h e Plow f l u l d d a t a , s u n s e d b y t h e f i v e h o l e p r o b e and t h e p r o b e c a l i b r a t i o n d a t a [221. From t h i s d a t a o t h e r p a r a m e t e r s o f i n t e r e s t a r e a l s o computed . P r e s s u r e s u r v e y d a t a f r o m t h e model o r f rom t h e model wake i s p r o c e s s e d t o y i e l d t h e l o a d d i s t r i b u t i o n o v e r t h e b o d y o r t h e p r e s s u r e l o s s i n t h e wake. T h e s e r e s u l t s a r e used t o c a l c u l a t e t h e n e c e s s a r y a e r o d y n a m i c q u a n t i t i e s .

The d a t a p r e s e n t a t i o n s o f t w a r e f o r t h e f o r c e a n d p r e s s u r e results i s i m p l e m e n t e d i n t h e u s u a l manner t h r o u g h w h i c h m u l t i p l e c o l o r p l o t 8 o f c o m p u r a b l e p a r a m e t e r s c o u l d be o b t a i n e d . I n t h e cc18e o f f l o w f i e l d d a t a p r e s e n t a t i o n , t h e s o f t w a r e d e v e l o p e d p r o v i d e s t h e u s e r w i t h t h e v e l o c i t y v e c t o r p l o t s on a HP7470 c o l o r g r a p h i c s p l o t t e r . F o r a q u i c k v i s u a l i s a t i o n o f t h e flow f i e l d a r o u n d t h e m o d e l , a s o f t w a r e package h a s b e e n d e v e l o p e d t o p r e s e n t t h e v e l o c i t y d a t a ( o r l o c a l head l o s s ) i n t h e fo rm o f c o l o u r g r a p h i c c o n t o u r p l o t s on t h e PC. U a i n g t h i s pcickage~, t h e c o n t o u r s o f s e l e c t i v e m a g n i t u d e s o f t h e f l o w f i e l d may b e p l o t t e d . C o r r e s p o n d i n g t o t h e u s e r ' s c h o i c e , t h e s o f t w a r e f i r s t s e a r c h e s f o r a n d s e p a r a t e s o u t t h e i s o- m a g n i t u d e d a t a f r o m t h e v e l o c i t y d a t a . Then t h e e q u i v e l o c i t y c o n t o u r s a r e d i s p l a y e d i n c o l o u r g r a p h i c s . The r a n g e be tween t h e a d j a c e n t c o n t o u r s i s shaded w i t h d i f f e r e n t c o l o u r p a t t e q n s . T h i s p r o v i d e s a q u i c k , v i s u a l a p p r e c L a t i o n of t h e f l o w f i e l d a r o u n d t h e t e s t model i n a n e a s y a n d i n e x p e n s i v e way. However, i f some c o n t o u r s a r e c l o s e l y s p a c e d , d e p e n d i n g o n t h e a c t u a l l a y o u t o f t h e c o n t o u r s , t h e p a t t e r n s u s e d t o s h a d e t h e r e g i o n s may l e a d t o c o n f u s i o n . T h i s h a s been ove rcome by p r o v i d i n g t h e u s e r w i t h an o p t i o n t o c h a n g e t h e c o l o u r p a t t e r n s a f t e r e x a m i n i n g t h e c o n t o u r p l o t s p r e s e n t e d on t h e s c r e e n . The a v a i l a b l e c o l o u r p a t t e r n s a re shown a d j a c e n t t o t h e p l o t w i t h an i n d i c a t i o n o f t h e d e f a u l t colours a s s i g n e d t o t h e s e l e c t e d m a g n i t u d e r a n g e s . Through t h e k e y b o a r d , t h e u s e r can s e l e c t a p a t t e r n a n d g i v e a command t o f i l l u p t h e s e l e c t e d c o n t o u r r e g i o n . R e p r e s e n t a t i v e p h o t o g r a p h s o f t h e c o l o r g r a p h i c s d i s p l a y s

from t h e a c q u i r e d d a t a ,

p l o t s .

(CIASF '87 RECORD-41

o f t h e f low f i e l d d a t a have been g i v e n i n F i g u r e s 8 and 9. The f i n a l formu o f Lha d i s p l a y s oould a l s o be saved f o r f u L u r e r e f e r e n c e .

C o n c l u s i o n s :

The hardware and t h e s o f t w a r e o f t h e i n t e g r a t e d i n 8 t rumen t a t i o n s y s tem t h a t i s s u i t a b l e t o small s c a l e wind t u n n e l a p p l i c a t i o n s h a s been s u c c e s s f u l l y d e s i g n e d and r e a l i s e d . The sys tem has been i n s t a l l e d i n t h e CCWT a t 1 . 1 . S ~ . and t e s t e d , R e p r e s e n t a t i v e c o l o r g r a p h i c s p l o t s have been p r e s e n t e d . S i n c e t h e i m p o r t a n t f e a t u r e , i n t h e s e p l o t s is t h e d i f f e r e n t c o l o r s , t h e same may n o t be e f f e c t i v e l y s e e n i n t h e f i n a l form of t h e p a p e r . However, we e x p e c t a d i s t i n g u i s h a b l e g r a d a t i o n i n t h e c o n t o u r levels i n t h e f i n a l p i c t u r e s .

Acknowledgements :

The a u t h o r s g r e a t f u l l y acknowledge t h e A e r o n a u t i c a l Research and Development Board f o r f u n d i n g tiis p r o j e c t . The a u t h o r s wi8h t o acknowledge P r o f . Ramssuamy, P r o f . S . P . C o v l n d a r a j u arid Prof, P.R. Mahapatra f o r t h e i r u s e f u l s u g g e s t i o n s . The a u t h o r 8 wish t o t h a n k Mi-. B . A . Mtldankumclr f o r h i 8 a c t i v u o u p p o r t i n t h e p r e p e r a t i o n o f t h e m a n u s c r i p t . 4

R e f e r e n c e s :

[ 1 ] C . Ravikumar, " A M i c r o p r o c e s s o r baaed I n t e g r , a t e d System f o r Wind Tunne l A p p l i c a t i o n s t ! , M. Sc. (Engg. ) T h e s i s , 1986.

[2] M. Konig and H . J . P f e i f e r , "LDA d a t a a c q u i s i t i o n s y s t e m s w i t h h i g h a c c u r a c y and h i g h d a t a r a t e " , ICIASF '77 Record, pp. 13- 21, 197'7.

[ 3 ] A . B o u t i e r , C. F e r t i n and J . L e f e v r e , " L a s e r v e l o c i r n u t e r f o r wind tunnel. measurementsf t , ICAISF ' 7 7 Record , pp.

[ 4 ] W.J. Yanta , " A t h r e e d i m e n s i o n a l l a s e r d o p p l a r v e l o c i m e t e r f o r u s e i n wind t u n n e l s b 1 ICIASF ' 7 9 , Record, pp. 294-301, 1479.

[ 5 ] D.W. Schmid t , " A c c o u s t i c a l methods f o r f a s t d e t e c t i o n and measurement o f v o r t i c e s i n wind t u n n e l s " , ICIASF ' 7 5 Record , pp. 216-228, 1975.

[6] R . H . E n g l e r , H . H o l s t , D.W. Schmidt and R I Wulf, "Measurement o f v o r t i c e s i n wind t u n n e l e x p e r i m e n t s by U B ~ o f u l t r a s o n i c p u l s e a l l , ICIASF ' 7 9 Record , pp. 163-170, 1979.

[ 7 ] C . Meyer, "Wind t u n n e l measurements w i t h a n e l e c t r o n i c a l l y s c a n n e d m u l t i p o r t p r e s s u r e s e n s o r l l , ICIASFI81 Record , 1981.

1-12; 1977.

[81 C.F. Coe, C . T . P a r r a and R . C . Kuuf'firiun, " A naw e l u c t r o n i c t i c u n n u r o f p r e s s u r e des igned for i n s t a l l l a t i o n i n wind t u n n e l modelstl, ICIASF '81 R e c o r d , 1981.

[ 9 ] IIMACSYM 20 - Users Manualft , Analog D e v i c e s , I n c o r p o r a t e d , USA.

[ l o ] A.E. Winkelmann, and C . P . TSAO, " A c o l o r v i d e o d i s p l a y t echn ique f o r f l o w f i e l d s u r v u y e t f A I A A Journal, v o l . 2 3 ( 9 ) , p . 1 3 8 1 , September 1985.

[113 t r i A P X 8 6 , 8 8 User 's Manual", I n t e l C o r p o r a t i o n , Augus t 1981.

[ 121 Robin J i g a u r , "Using t h e 8259A p r o g r am ma b 1 e i n t e r r u p t c on t r o 11 a r I t , A p p l i c a t i o n Note AP- 59, I n t e l C o r p o r a t i o n , 1979 .

[131 "Using t h e 8251 U n i v e r s a l Synchronous / Asynchronous R e c e i v e r / T r a n s m i 1 t e rll P e r i p h e r a l d e s i g n handbook, h t e l C o r p o r a t i o n , pp. 2.241-2.270, Augus t 1981.

[ 1 4 ] David B .Gus tavson , tfComputer Buses-A T u t o r i a l t 1 , I E E E Micro , August 1984.

[ 1 5 1 J o e B a r t h m a i e r , t f X n t e l m u l t i b u s i n t e r f a c i n g f t , A p p l i c a t i o n Note , AP 284 , I n t e l C o r p o r a t i o n , 1979.

[ I 6 1 Z . M . Rtimly, E I and W.J. R a n b i r d , ItGomputer controlled system f o r t h e i n v a u t i g a t i o n o f t h e f low beh ind wingsl l , J o u r n a l o f A i r c r a f t , v o l .

[171 l l O p t o - u l e c t r o n i c s cornporittnt Hund B o o k t f , G e n e r a l I n s t r u m e n t s , U S A ,

[ I 8 1 S.P. G o v i n d a r a j u , N. B a l a k r i s h n a n and C . Ravikumar , "Development of a p r e s s u r e a e n s o r w i t h d i g i t a l o u t p u t b a s e d on a l i q u i d manometer" , P r o c . o f 1 1 t h N a t i o n a l symposium on f l u i d mechan ics and f l u i d power, pp. A P l 4 - 1 9 , December 1982 .

[ 1 9 ] C . Ravikumar a n d N . B a l a k r i s h n a n , " A low c o s t m i c r o p r oc e s s o r based m u l t i p l e p r e s s u r e measur ing system!', t o a p p e a r i n J o u r n a l of Microcomputer A p p l i c a t i o n s , Academic P r e s s , v o l . 1 0 , 1987.

[ 2 0 ] S .P . G o v i n d a r a j u , and V.S. I i o l l a , "Design o f k h e p i t c h and t h e yaw mechanism f o r a wind t u n n e l w ' , T e c h n i c a l R e p o r t No; AE-380/A, 1984.

L21.1 C . Ravikumar , M . A . Ramaswaruy and V.S. H o l l a , " C a l i b r a t i o n of the s i x component s t r a i n gauge b a l a n c e for t h e CCWTII T e c h n i c a l Repor t No .AE- 397/A, 198b .

[ 2 2 ] R . Wickens , P. S o u t h , R.S. Rangi and D . Henshaw, " E x p e r i m e n t a l development i n V/STOL wind t u n n e l t e s t i n g a t t h e n a t i o n a l a e r o n a u t i c a l e s t a b l i s h m e n t t t , Canad ian a e r o n a u t i c s and s p a c e j o u r n a l , v o l . 1 9 , pp. 145-154, A p r i l

1 4 ( 7 ) , pp. 668-674, J ~ l y . 1 9 7 7 .

1979 .

/

1973.


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BRIEF BIOGRAPHIES OF AUTHORS

C. Ravikumar graduated in 1979 from Nagarjuna University, Guntur, India and received M.Sc. degree in engineering physics and instrumentation in 1981 from Osmania University, Hyderabad, India. In 1981 he joined the department of Aerospace Engineering, Indian Institute of Science, Bangalore, India where he was employed as a Scientific Assistant. At the Indian Institute of Science he had also completed a research oriented M.Sc. (Engg) degree. His fields of interest include microprocessor based instrumentation, microcomputer systems and computur orig inuering .

N. Balakrishnan received the BE degree in electronics and communications from the University of Madras, India in 1972 and the Ph.D. degree from the department of Aerospace Engineering, Indian Institute of Science, Bangalore, India in 1979.

In 1973 he joined the Department of Aerospace Engineering where he is currently employed as Associate Professor. His fields of research interest include numerical electromagnetics, space craft antennas, computer science and microprocessor systems. '

Prof. Balakrishnan is a life member of the Instrument Society of India and is on the editorial board of the Current Science Journal. He is the recipient of the UNESCO/ROSTCA award for outstanding contributions in the area of computers and informatics for the year 1985. He is the Convener of the Centre for Microprocessor Applications and also the Centre for Science Information at' the Indian Institute of Science. He is also a consultant to lhading Government and Private industries

. .

V.S. Holla received the B.Sc. (1956) and B.Ed. (1960) degrees from Mysore University, India, the M.Sc. (Mathematics) degree from Karnataka University in 1961 and the Ph.D. degree from Indian Institute of Science, Bangalore, India, in 1969. He joined the department o f Aerospace Engineering, Indian Institute of Science in 1965 as a Technical Assistant and is currently an Associate Professor in Aerodynamics. His interests are in Theoretical and Experimental Aerodynamics and has been working in this area for the last 2 2 years.

Prof. Holla l a a member of the'Aeronautica1 Society of India. He is also on the Editorial Boar4 of the Journal of Aeronautical Society of India, as an Associate Editor since 1980.
