Stability and robustness analysis of frequency-shaped impedance control for reference tracking and compliant interaction

There have been several design methodologies of impedance control without using force sensors, most of which use an observer to estimate external forces and conduct impedance control based on the observed external force. Since the external forces are estimated in a feedback way in this type of force observer-based impedance control, it has been impossible to achieve reference tracking performance when the impedance is designed low for compliant interaction. This paper proposes a novel frequency-shaped impedance control which can perform compliant motions and reference tracking simultaneously. The proposed algorithm is based on the disturbance observer design which allows a straightforward design of compliant interactive force and employs feedforward controller to compensate for the frequency bandwidth that can be sacrificed due to low impedance design. Experiments with an industrial robot verify the effectiveness of the proposed controller.