Position domain nonlinear PD control for contour tracking of robotic manipulator

Contouring control is most important in machining applications to ensure the quality of the final product. In this paper, the contouring control problem for a multi-dof robotic manipulator is studied, and a nonlinear PD (NPD) control law is proposed in position domain and applied to contour tracking control. To develop the position domain control system, the robotic motions are viewed as the combination of a master motion, controlled in time domain, and slave motions controlled in position domain. The master motion is used as a reference for the slave motions, and the slave motions are controlled by the developed NPD and synchronized with the master motion so that a good contour tracking performance can be achieved. Stability analysis is conducted based on the Lyapunov theory for the developed position domain NPD control. Linear and nonlinear contour tracking problems are simulated and compared with existed PD controllers. It is demonstrated that the position domain NPD control can achieve much better contour tracking performance compared with the counterparts in time domain and the linear PD-type position domain control. Furthermore, the proposed NPD controller is much efficient for nonlinear contour tracking problems.