Design of air bearing system for fine motion application of multi-DOF spherical actuators

Fluid bearings play active roles in precision devices, supporting large loads in machinery thereby extending the lifetime of components by reducing wear and tear. Many potential industrial applications of spherical actuators require fine motion control of the output shaft. A noncontact bearing design for such spherical devices offers an interesting method of achieving precision positioning of the output shaft and yet has the potential to enhance their performance in more advanced applications. This paper presents an analytical investigation on the design, modeling of a practical air bearing system for ball-joint-like actuators. Specifically, it discussed design issues and kinematics, and characterizes the air bearing forces of a variable reluctance (VR) spherical actuator. The air bearing system introduces three linear degrees of freedom (DOF) motion to the rotor dynamics and the paper addresses a method of regulating the translations in order to improve the orientation manipulations. The performance of the design is evaluated through improvements in the torque output and dynamic performance of the orientation motion. It is expected that this research will be a basis for designing and evaluating an improved VR spherical motor with enhanced torque capability by eliminating mechanical friction