Contact transition stability in the impedance control

Contact stability has been considered based on simplified linearized models of a robot and its environment. It is shown that the most crucial parameter for contact stability is the target damping ratio. When a high compliance is required, the stability boundary requires a significantly overdamped impedance to ensure a stable contact with a stiff environment. These conditions for a SISO system are defined in the analytic form. Obtained minimal damping ratio values are significantly lower than those previously proposed in the literature.