Design of a power assist system with consideration of actuator's maximum torque

This paper proposes a control method for a power assist system which attenuates the load force. In the system, the question of how to select a power assist ratio is important. This ratio must be selected with consideration of the maximum torque of each actuator used in the system, otherwise the actuator saturation may occur and cause the lack of the manoeuvrability and instability. To avoid such saturation problems, we propose a new control method which, after dividing an operated load into gravity load and dynamic load, selects a power assist ratio for the dynamic by considering the remaining actuator torque after the ratio for the gravity load is determined basing on the operator's capability. The control law is formulated for a single axis power assist system and the effectiveness of the method is confirmed by experiments.