Nonlinear servo control for precise tracking systems

Abstract

This paper with the problem of parameter identification and trajectory tracking of a nonlinear electro-mechanical system, which consists of a DC motor that drives a nonlinear load that resembles a one-degree-of-freedom robotic manipulator. The system presents two types of nonlinearity; one of a discontinuous nature, due to static and Coulomb frictions, and the other continuous, due to non-linear loading. Only the angular position of the nonlinear load is available for feedback purposes. Static and Coulomb frictions are modeled and compensated using a nonlinear compensation scheme that depends on the speed of the load. The unknown parameters of the nonlinear compensating and unloaded system are identified open loop in the frequency domain using Feedback Linearization. Finally, the implementation of the designed control system is presented, together with its experimental results, which are compared with those obtained when the nonlinear controller is replaced by a linear PID controller.