Digital Sliding Mode Control via a Novel Reaching Law and Application in Shipborne Electro-Optical Systems

Abstract

The alignment accuracy and stability of shipborne electro-optical system are affected by external attitude disturbance and internal non-linear disturbance. Therefore, this study examined a new digital sliding mode control based on a novel reaching law with an n-order disturbance compensator to solve this problem. Specially, the proposed novel reaching law was a chatter-free method, in which, as the switching gain was replaced by an adaptive function, chattering on the sliding surface tended to zero. For perturbed systems, the new sliding mode controller was able to guarantee a narrow quasi-sliding-mode domain and the ultimate width was the order of O(T 3 ), such that the narrower the quasi-sliding-mode domain width was, the more robust toward nonlinear disturbances. Both mathematical calculations and simulations verified the convergence and stability of the new controller. Finally, based on a compound control strategy that combined feedforward control with a sliding mode control position loop and proportional-integral velocity loop control structure, shipborne equivalent dynamic target tracking experiments were performed. The results, compared with existing controllers, showed that the robustness of the new controller to nonlinear disturbances was stronger and the tracking system accuracy clearly improved, while the influence of sliding mode chattering on the system was avoided.INDEX TERMS Shipborne electro-optical system, nonlinear disturbance, digital sliding mode control, chattering, reaching law, disturbance compensator, chattering-free, quasi-sliding-mode domain.

Application of bilateral sliding mode predictive compound control in photoelectric tracking system

“…The NRL incorporates the power term and switching gain term of system state variables into the Conventional Exponential Reaching Law (CERL) and eventually suppresses the sliding mode chattering and increases the convergence rate of system state reaching the sliding mode surface. Zhang et al 2019(a) developed a novel chatter-free reaching law, in which, as the switching gain was replaced by an adaptive function, chattering on the sliding surface tended to zero.…”

An adaptive reaching law of chattering‐free discrete‐time sliding mode control for systems with external disturbance

“…The reaching law can drive sliding variables monotonically toward switch plane and cross it without increase in every successive sampling period. It is well known that chattering occurs near the switch plane due to the existence of the discontinuous term $$$ \operatorname{sign}\left({s}_k\right) $$$ and thus leads to both performance degradation and potential damage to the actuators [21]. Based on Gao's reaching law, various forms of reaching laws have been proposed thereafter to depress chattering and increase reaching speed.…”

Digital sliding mode controllers for active control of ground vehicles

“…Various works have appeared in the last years to fill the gap between the continuous and the discrete-time counterparts; see previous studies [28][29][30] just to cite a few. Nowadays, discrete-time SMC is popular among control engineers, as one can find in the literature many examples of applications in various fields of industrial interest [31][32][33][34][35][36][37].…”