Through the analysis for the kinetic equation of over-actuated parallel manipulator, it is proved that the partial actuator failure can be avoided by reasonably distributing torque output of each actuator, thus the first occurrence of failure can be deferred. The capacity of each actuator is first discussed in this paper, and then the concept of the output margin is proposed. The drive torque optimization model is accordingly put forward. With the selection criteria of the weighted coefficient constructed from output margin, independent mediation of each drive is achieved. The torque distribution method under balanced output margin and mean output margin of partial actuator is conducted, so the loading of each actuator is coordinated. With a planar three DOF redundant actuated parallel manipulator, the result of calculation and analysis shows that the proposed method is helpful to regulate the balanced margin output of each actuator and thus prevent partial actuators from over loading.
