Improvement of integrator backstepping control for ships with concise robust control and nonlinear decoration

Abstract

Course-keeping control through normal integrator backstepping method has defects of introducing many adjustment parameters and not considering the energy cost of actuator. In order to enhance the performance of integrator backstepping controller, a control law formed by closed-loop gain-shaping algorithm is adopted to replace the linear terms in the original control law. The energy cost is reduced by nonlinear decoration of sine function to the controller output, and the steering interval is lengthened according to the analyzation of full-scale sea trail data from training vessel Yukun. To decrease overshoot, the desired course is filtered by a first-order inertial component. Then a performance index is proposed to verify the performance of each control strategy combination. Simulation results show that the proposed controller has good robustness to the perturbation of steering mechanisms and ship model in rough sea states. At the same time, mean rudder angle is decreased by 17.3%, so energy consumption is reduced. The algorithm proposed in this paper has good theoretical analysis, satisfactory robustness with less parameters, reasonable steering frequency and remarkable energy saving effect.