Output Feedback Robust Control of Direct Current Motors With Nonlinear Friction Compensation and Disturbance Rejection

Abstract

High accuracy tracking control of direct current (DC) motors is concerned in this paper. A continuously differentiable friction model is adopted to account for the friction nonlinearities, which allows more flexible and suitable practical implementation. Since only output signal is available for measurement, an extended state observer (ESO) is designed to provide precise estimates of the unmeasurable state together with external disturbances, which facilitates the controller design without any transformations. The global stability of the controller is ensured via a certain robust feedback law. The resulting controller theoretically guarantees a prescribed tracking performance in general, while achieving asymptotic output tracking in the absence of timevarying disturbances, which is very important for high accuracy control of motion systems. Comparative experimental results are obtained to verify the highperformance nature of the proposed control strategy.