Load distribution algorithms and experimentation for a redundantly actuated, singularity-free 3-DOF parallel haptic device

Parallel-type mechanisms provide many advantages over serial-type mechanisms. However, in case of using parallel structures as a haptic device, it is sometimes hard to ensure the performance of the force reflection due to many singular points existing in workspace. In this paper, we propose a redundantly actuated parallel 3-DOF haptic device, which is singularity-free in the workspace and also has an improved force reflection capability. Using two sets of actuators with different size and different force resolution, we propose several useful load distribution algorithms considering force resolution and torque limit. We confirm the performance of the force reflection capability throughout simulation and experimentation.