Impedance control of robot manipulator with model reference torque observer

The impedance control is an effective way to adjust both the position and the force of the manipulator of the robot so as to accommodate the request of the application in some fields such as industry and aerospace. The algorithm is implemented into two control loops. The inner loop is the position control to ensure the precision operation of the manipulator, which uses the forward and inverse kinematics solution and rely on the closed-loop control of the joint driver. The outer loop is the impedance control which achieves the implementation of the force control between the manipulator and the environment by adjusting the impedance model. This loop outputs a correction to the position loop that includes the force control information. One problem of impedance control is that the force sensors used to measure the react force of the environment increase the complexity and reduce the reliability of the system. A model reference torque observer of the joint, which using permanent magnet synchronous motor (PMSM) as the actuator, is presented and applied to the impedance control loop. The simulation results show the correctness and feasibility of this algorithm.