Precise Control of Elastic Joint Robot Using an Interconnection and Damping Assignment Passivity-Based Approach

Vibration suppression and precise tracking are the two main challenges in the control of elastic joint robots. In this study, an elastic joint robot with precise position sensors on both the motor and link sides is developed to tackle these challenges. With a two-mass model for elastic joint and a LuGre friction model for joint friction, the elastic joint robot system is modeled and analyzed as an underactuated port-controlled Hamiltonian system with dissipation (PCHD). The proposed elastic joint controller is integrated with friction compensation using the interconnection and damping assignment passivity-based control method, leading to a PCHD closed loop system that can be effectively tuned to suppress vibration associated with elastic joints. In addition, integral control is employed to achieve high tracking precision. Experiments have been conducted and the results have demonstrated high performance of the proposed control method.