Dithering Based Actuation of a Miniaturized Active Ball-And-Socket Joint

Actuation of ball-and-socket joints has been a challenge owing to the multiple degrees of freedom they possess. In the recent past, active ball and socket joints have been proposed but their sizes have generally been large. This paper discusses a novel method to precisely actuate a miniature ball-and-socket joint, where the ball is a permanent-magnetic sphere seated in a socket. It is proposed to employ a dithering to avoid dead zone, and hysteresis nonlinearities. Simulations have been performed in order to confirm that hysteresis can be eliminated by means of dithering. possible. Finally, a miniaturized ball and socket joint with a ball of diameter 5 mm is fabricated and is experimentally demonstrated to achieve much better linearity by applying dithering, with 6-times lesser dead-zone, and negligible hysteresis, in comparison to the case without dithering.