Improvement of Design and Motion Control for Motion Platform Based on Spherical Wheels

In this paper, a six-degree-of-freedom (DOF) motion platform based on spherical wheels is presented to improve design and motion control from the earlier design. The motion platform developed here is capable of 3-DOFs unlimited rotation and 3-DOFs translation, which has large workspace of linear motion with better stability and high rigidity. In particular, the new design offers better motion control, uniformity, and safety in motion range by additional actuators providing better motion capability for virtual reality. Kinematic analysis of the platform is investigated to provide a basis for motion controllability. In particular, the rotational motion can be independently controlled from the translation by the active driving control. The design and motion analysis are demonstrated from both numerical simulation and experiment using a prototype in an open-loop control. Slipping motion and friction as a main driving torque are experimentally evaluated for a nonslip condition. The comparison results prove the design feasibility and motion control capability.