A novel concept and impedance schematic analysis for nonlinear stiffness compliant actuator (NSCA)

This paper proposed a new concept about compliant actuators used in robot and environment interaction that is “high load, high stiffness and low load, low stiffness” with respect to the decoupled variable stiffness actuators (VSA), because most of VSA could control position and stiffness independently, where some performance is not necessary in robot and environments or human interaction. To explicit tradeoff between external load and actuators stiffness, the novel nonlinear stiffness compliant actuator (NSCA) based on nonlinear stiffness elastic components was designed. On one hand, sense tiny force in low interaction; on other hand, ensure systematic bandwidth in high interaction force. In this paper, the mechanical structure of the NSCA, dynamic equations of the SEA are established. Impedance control algorithm and hardware circuit are then presented. At last, simulation and experiment are conducted to validate the performance of the NSCA. The results show high performance of controlling the NSCA.