A magnetically levitated fine motion wrist: kinematics, dynamics and control

Reference is made to a previous paper by the authors and A.P. Allan (1988) in which the motivation for and the design of a magnetically levitated robot wrist have been described. The kinematic and dynamic transformations that are required for the control of this `magic´ wrist are presented. The wrist´s dynamics are formulated in terms of the Euler quaternion, and the advantages of such a formulation, as well as control schemes based on it, are discussed. The prototype magic wrist was successfully controlled with a simple PD (proportional differential) feedback compensator, both in position and compliance modes. The result obtained, including synthesis of several mechanisms, establish the feasibility of the approach proposed in the original paper