Comparison of various active impedance control approaches, modeling, implementation, passivity, stability and trade-offs

Impedance control, as method to improve the interaction ability of robotic systems, has gained great attention by the robotic community and a large number of different implementations have been reported in the literature. Most implementations are based on an outer impedance loop and a number of nested inner loops. In this paper, various active Impedance Control (IC) schemes are designed, analyzed and tested based on different inner control loops, namely velocity, position and torque. IC on link and motor side are considered. Stability, passivity, safety and performance of the different IC schemes are presented. All the IC schemes are evaluated and tested on a 1-dof series elastic actuator. The system dynamics are modeled including gearbox meshing friction and harmonic drive torque ripple. Simulation and experimental results are compared.