Dynamic stability of a tripod parallel robotic wrist featuring continuous end-effector rotation used for drill point grinder

This paper deals with the dynamic stability problem of a tripod parallel robotic wrist by means of monodromy matrix method. This robotic wrist can generate a continuous end-effector rotation in any configuration within its orientation workspace, which allows the manipulator to function as a machine tool head used for a drill point grinder. The system's linearized equations of motion are established in terms of both lateral and torsional vibrations to analyze the stability problem, resorting to the Floquet theory. As a result, the stable regions of the manipulator are visualized, and the stability charts are constructed on various parameter planes to detect the parametric instabilities and to reveal the effect of the selected pairs of system parameters onto the stability. Critical parameters, such as the rotating speeds of the driving shaft and the actuation stiffness, are identified for the prototyped grinder.