Collision Detection and Avoidance in Computer Controlled Manipulators

The p r o b l e m o f p l a n n i n g s a f e t r a j e c t o r i e s f o r compute r c o n t r o l l e d m a n i p u l a t o r s w i t h two movab le l i n k s and m u l t i p l e deg rees o f f r eedom i s a n a l y z e d , and a s o l u t i o n t o t h e p r o b l e m p r o p o s e d . The key f e a t u r e s o f t h e s o l u t i o n a r e : 1 . t h e i d e n t i f i c a t i o n o f t r a j e c t o r y p r i m i t i v e s and a h i e r a r c h y o f a b s t r a c t i o n spaces t h a t p e r m i t s i m p l e m a n i p u l a t o r m o d e l s , 2 . t h e c h a r a c t e r i z a t i o n o f empty space b y a p p r o x i m a t i n g i t w i t h e a s i l y d e s c r i b a b l e e n t i t i e s c a l l e d c h a r t s t h e a p p r o x i m a t i o n i s dynamic and can b e s e l e c t i v e , 3 . a scheme f o r p l a n n i n g m o t i o n s c l o s e t o o b s t a c l e s t h a t i s c o m p u t a t i o n a l l y v i a b l e , and t h a t s u g g e s t s how p r o x i m i t y s e n s o r s m i g h t be used to do t h e p l a n n i n g , and 4 . t h e use o f h i e r a r c h i c a l d e c o m p o s i t i o n t o r e d u c e t h e c o m p l e x i t y o f t h e p l a n n i n g p r o b l e m .