Nonlinear PID control with sliding modes for tracking of robot manipulators

It is well-known that PD controller plus gravity compensation yields the global asymptotic stability for regulation tasks for robot manipulators. The impressive success of these controllers in real-time tasks lie in the fact that they do neither compensate inertial nor coriolis forces, so neither inertial nor coriolis matrices are needed to implement the controller. However these linear state feedback controllers with gravity compensation cannot render asymptotic stability for tracking tasks. In this paper, a simple decentralized continuous nonlinear PID controller that yields local exponential stability for tracking tasks is proposed