Handling Torque Input Constraints Under Robust Nonlinear Regulation Control of Robotic Systems with Parametric Uncertainties

This paper proposes a methodology of handling torque input constraints under robust nonlinear regulation control synthesis for robotic systems with parametric uncertainties. The proposed method is composed of: (i) an inner loop controller design applying a nonlinear geometric control via  feedback linearization to transform uncertain robotic systems into worst-case uncertain linear system, (ii) a new method of torque input constraint mapping the constraints on the input torques into a constraint on new control inputs of the uncertain linear system through the feedback linearizing control law, and (iii) a new approach of outer loop controller design using robust H∞ static state feedback controller to handle the remaining uncertain nonlinear parts and to satisfy the mapped input constraints. In order to verify the correctness and the performance of the proposed method, it is demonstrated via simulation of position control problem for a two-link robotic system.