The conventional impedance control uses a second order differential equation to address the interaction between the robot arm and the environment. Reasonable estimation of mass(M), stiffness(K) and damping(B) coefficients is applied. However, the force measurement at the robot wrist not only includes the force exerted from the environment but gravity and Coriolis force. And the mass, stiffness and damping coefficients are subject to change with time. It is necessary to improve the conventional impedance control structure as shown below.