Development of a Spherical Air Bearing Positioning System

In line with the general trend of the automation, spherical motion systems are increasingly required in applications such as robot joints, manipulators, orientation control systems, and angular alignment systems. In this paper, a spherical air bearing positioning system (SABS) aiming at providing highly precise rotational motions in two degrees of freedom is designed. The SABS mainly consists of direct-drive voice coil actuators and pneumatic bearing. This paper presents the mechanical structure and control system of the SABS. The model of the SABS is identified based on adaptive control concepts. To eliminate the measurement noise, a noise filter is designed on the basis of the model. Then, an observer-based PID controller is designed and implemented on a dSPACE development card. The experiment results show that the designed controller can achieve higher precision and better tracking performance of about ten times compared to that from a traditional PID controller.