Design and analysis of an absolute non-contact orientation sensor for wrist motion control

In this paper, aspects of the design and analysis of a vision-based non-contact absolute orientation sensor with application to wrist-like actuator motion control, are presented. This work is primarily motivated by the need for the measurement of the absolute orientation of a spherical rotor present in wrist-like actuators for the motion control of such systems. Current orientation measurement approaches increase the complexity of the mechanical structure through additional contact with the spherical rotor. To eliminate this additional complexity, a noncontact vision-based technique that realizes an absolute orientation measurement using a specially designed grid pattern that allows the absolute orientation information to be encoded onto the spherical body has been developed. Aspects of the design and implementation of this specially designed grid pattern are also discussed. Improved techniques for transferring the grid pattern to a spherical object are presented, and issues related to the use of such a vision-based system for motion control are also discussed.