I need to control an robot hand through keybord to grasp an object(ball or polyhedron ),but I don''t know how to judge and computer the exactly coordinate of the hand-end how to detect the collision? Is there any example?

How about making code to test whether the outline of the hand model lies within the outline of the ball. Basically see if the coordinates of the hand touch the coordinates of the ball, then group or synch the movement of the ball to the movement of the hand.

a possible solution is the selection buffer. see the demo on my site

http://members.xoom.com/myBollux

look at Romka''s site (romka.demonews.com) for the robot example.
its great, simple and useful!

enjoy.