Control of impact disturbance by redundantly actuated mechanism

When a robot system collides with its environment, unexpected position errors occur due to the effect of impact. Large actuation effort may grow up to compensate for these errors. The sudden increases of actuator torque may violate the torque limit. We propose to employ a redundant actuation mode to facilitate disturbance rejection. An optimal load distribution algorithm for redundantly actuated system is introduced to reduce the effect of shocks. This scheme distributes the compensating effort to the system actuators in consideration of the torque limit. The disturbance rejection capability of the proposed scheme is compared with those of other load distribution methods by simulation and experiment. A five-bar mechanism is employed as an exemplary plant.