I want to clarify that I am really beginner with blender. I modeled a fairly simple .blend with balls that are supposed to be retrieved by a robot. At first I tried with a ball made with "rigid body" but it slipped in all directions. So I tried with ball "soft body". The ball is therefore much "catchable" but the problem is that the arms of the robot pass through (see image). What's bizarre is that when I roll on it with the robot, it does not pass through but climbs and crushes the ball.
If you have any idea how to solve this problem, I would be grateful