Redundant actuation means that there are more actuators than system's mobility. For example, the human arm has 29 muscles for 7 mobilities, and redundant system is also used in multi-fingered robot, mobile robot, and cooperating robot. There are many advantages in redundant actuation. First, actuation redundancy can increase the force, velocity and acceleration of end-effector. Second, if some actuators are out of order, that system can work well. This fault tolerant capability is useful for the remote control robot in space or the nuclear plant. And then, modulating the arbitrary stiffness without feedback control, impulsive force can decrease. Optimizing redundancy, the performance of system can be improved. But, there are some issues on economic efficiency and minimization of system, because redundant actuation can use more actuators than non-redundant actuation. In addition, there are the infinite torque sets of motors for the same work. I used the weighted pseudoinverse matrix for torque distribution. To reduce the maximum torque, I suggested to use the minimum norm torque value as the weighting value. Reducing the maximum torque can contribute to economic efficiency and minimization of system.
