Variable stiffness force tracking impedance control using differential-less method

As robot manipulators are widely used in contact with the environment, force tracking control is becoming more and more important. Variable stiffness impedance control can achieve force tracking by adjusting the stiffness of robot manipulators to get adapted to various environments just like human control to contact force. Most of the variable stiffness forces tracking impedance control methods need to obtain contact force differential information, but in fact there are high-frequency noise interferences in force sensor resulting in a big error of force differential. In order to make the strategy more feasible in practice, this paper proposes a differential-less method of variable stiffness force tracking impedance control. Analogously, the proposed control scheme achieves a contact force regulation control without force differential information. Moreover, the stability of the proposed control scheme is proved with a quadratic Lyapunov function. Extensive simulation studies with a two-degree-of-freedom robot manipulator are conducted to demonstrate the validity of the proposed method.