Infinity norm approach for precise force control of manipulators driven by Bi-articular actuators

In recent years there has been increasing interest in manipulators presenting animal muskuloskeletal characteristics such as bi-articular actuators. Manipulators driven by bi-articular actuators usually have more actuators than joints, presenting therefore actuator redundancy. In this paper a new approach based on ∞-norm to resolve actuators redundancy is proposed. The proposed method is compared with the Phase Different Control (PDC) approach, which is based on human muscle activation level patterns. It is shown that the infinity norm approach produces no error in output force, while the PDC approach produces non-zero error. Moreover, in this paper, a PDC approach with non-linear model that eliminates error in output force is also proposed. However the PDC approach with non-linear model is more complex than the proposed infinity norm approach.