Fractional impedance control for reproducing the material properties of muscle

We reported a novel impedance control method based on a fractional calculation inspired by the viscoelastic properties of biomaterials such as muscle. This fractional impedance controller was found to realize superior impact absorption for the purpose of flexible contact for assistive and rehabilitation robots. This paper presents a preliminary evaluation of this concept using simulations and experiments. The numerical analysis results demonstrate that a fractional impedance controller has superior impact absorption performance than a conventional controller for contact with the elastic objects, especially for high stiffness objects and high velocity movement. The numerical analysis also reveals that using a fractional controller improved the robustness with respect to the robot dynamics. Moreover, the experimental results demonstrate that the fractional controller effectively suppresses the force between a person and a robot.