Multi-objective design of optimal higher order sliding mode control for robust tracking of 2-DoF helicopter system based on metaheuristics

摘要

This paper deals with the trajectory tracking of a 2 Degrees of Freedom (DoF) helicopter system. The control strategy is designed by the combination of the robust control strategy (Higher Order-Sliding Mode Control (HO-SMC)) and the optimal control technique (Linear Quadratic Regulator (LQR)). Combining these two methods lies in the fact that the robust controllers tackle the uncertainties when the optimal controller performances are unaffected. As the performances of the Sliding Mode Control (SMC) greatly depends on the choice of the sliding surface, a novel method based on the solution of a Sylvester equation is proposed. Furthermore, the problem of deciding the optimal configuration of the LQR controller as well as the gain of the discontinuous control is considered as an optimization problem, which can be solved by the application of an efficient metaheuristic. The adequacy of the specific choice of the discontinuous gain is exhibited through general analysis. The main contribution of this paper is to consider a multi-objective optimization problem. For that, a novel dynamically aggregated objective function is proposed. As a result, a set of non-dominated optimal solutions are provided to the designer and then he selects the most preferable alternative. The proposed control strategy is applied for pitch and yaw axes control of the Quanser helicopter. Experimental results substantiate that the combination of the HO-SMC with the LQR method and metaheuristics results in not only reduced tracking error but also improved tracking response with reduced oscillations. (C) 2019 Elsevier Masson SAS. All rights reserved.