Dynamic modeling and sliding mode control of 3-RSS coaxial layout polishing robot

This paper proposes a 3-RSS coaxial layout polishing robot (CLPR), aiming to expand the workspace of the parallel mechanism and improve the stiffness and repeatable positioning accuracy of the polishing robot. The work presents the dynamic modeling and controller designing of the CLPR. Considering that specific structure and characteristics of polishing robot, it is considered as a multi-body system with asymmetric configuration, whose dynamic model is derived via principle of virtual work and screw theory. On the foundation of dynamics analysis, a second-order sliding mode controller is designed by improving the strategy of control law on ground of dynamic model. Based on the second-order model of the velocity-loop controller, a finite-time control method is used to implement the tracking following of the controller. The controller is utilized to improve robot’s dynamical performance. Finally, simulation tests are carried out and compared with the PID controller. The test results show that the sliding mode controller designed in this paper can achieve precise motion tracking control within 0.006 s with smooth dynamic performance. The control algorithm improves the dynamic performance of the motor, shortens the time required for motion tracking, and can be applied to the control of the robot.