Model Reference Adaptive Sliding Mode Control of a Laser Beam for Jitter Correction

Abstract

In this paper, a model reference adaptive sliding mode control is designed to improve the robustness of a fast steering mirror (FSM) which is used to track the reference signal in the presence of jitter. The FSM steers the deviated beam to the desired target. Here, sliding mode control is implemented which operates under nominal conditions. Due to ageing, it leads to parametric matched uncertainties of the FSM model. It deteriorates the performance of the nominal sliding mode control. Hence, an adaptive controller is designed to retain the desired performance in tracking the reference signal. A reference model is designed using dynamic inversion. Further, an adaptive sliding mode controller (with proportional-integral sliding surface) is designed and implemented on the perturbed system such that it negates the effects of uncertainties to improve the overall tracking performance. This makes the actual (perturbed) model follow the reference model. The proportionalintegral sliding surface proves out to be more robust towards parameter uncertainties. Moreover, the reference signal is filtered with FSM’s actuator bandwidth as the cut-off frequency of the low pass filter so that it carries the utmost frequency component that can be tracked by FSM. A comparative study has been done between nominal and model reference adaptive sliding mode control. Their performances are tabulated in detail and concluded with appropriate observations from simulation results.