Passivity based control of flexible joint robot with dynamic friction compensation

As the friction has a great effect on the performance of low speed and low stiffness impedance control of flexible joint robot, a modified Dahl friction model is adopted, and a friction observer is proposed to compensate the friction based on interconnection and damping assignment passivity based control (IDA-PBC) method. The dynamics friction compensation not only improves the position and force tracking performance, but also assures the stability of the system. Finally, experiments are carried out on a 6-DOF anthropomorphic manipulator to verify the compensation. The results show that position accuracy as well as torque vibration of the flexible joint system are evidently improved in the position control. In addition, the force tracking ability of impedance control is also improved by the friction compensation.