Optimal torque distribution for a redundant 3-RRR spherical parallel manipulator used as a haptic medical device

An optimal torque distribution approach for a redundant 3-RRR spherical parallel manipulator (SPM) with haptic capabilities is presented. The redundancy increases the number of solutions for the actuated joint torques for a given SPM configuration and given reference torques. The values of the joint torques are optimized, first, to eliminate the effect of singularity on the SPM and, second, to minimize the torque developed by the actuators. A SimMechanics model is used to validate the proposed approach. Experimental validation is also carried out. The results show the advantage of introducing redundancy of actuators to improve the behavior of the SPM.