Design of a Spherical Motor with Three Degrees of Freedom

Abstract

In this paper the development of a new spherical motor which provides multi-coordinate movements in one drive module is presented. Due to the ever increasing demands on product quality and the need to machine free form surfaces modern machine tools and robotic devices require five degrees of freedom. Thus there is the need for new machine tool concepts and drive technologies. The spherical motor is able to eliminate most disadvantages of conventional open kinematics consisting of sequential axes. It is based on a spherical rotor, which is - like a ball joint - guided in a sphere. Thus three-dimensional movements can be performed. A high torque in all positions is achieved by permanent magnets on the rotor and electromagnetic coils in the stator which are separately controlled by single power converters. Possible applications are the replacement of a robot hand axis unit or the integration in a machine tool to perform five axis milling operations. This paper reports on the development of the mechanical components, the power converter and control hardware as well as the magnetic design.