Ship longitudinal stabilization control based on CGSA and nonlinear switch modification

To further improve the ship's longitudinal motion stabilization control effect and the energy saving and robustness of the control method, this paper takes the training ship “YuKun” of Dalian Maritime University as the controlled plant. It analyzes the causes of the severe longitudinal motion of “YuKun”. In ship longitudinal pitch reduction control, the unstable controlled plant is transformed into a stable generalized controlled plant by Nyquist shaping, using the introduced mathematical tool of power function and gain adjustment. The controller is designed with a third-order closed-loop gain shaping algorithm (CGSA) and a switch nonlinear modification function. In the verification process, the performance index, Nyquist stability analysis, model perturbation simulation, and comparative. simulation experiments are used to prove that the designed control method has the advantages of stability, robustness, and improvement. The simulation results show that when the model is perturbed, the improved control method has the advantages of more energy saving, stability, and robustness. •The proposed third-order closed-loop gain shaping algorithm (CGSA) and nonlinear switch modification approach substantially enhances the control performance for ship longitudinal pitch reduction compared to existing control methods.•By employing Nyquist shaping, the weight function is carefully designed to effectively convert the initially unstable MIMO system into a stable MIMO system.•This study utilizes a simplified sea wave disturbance model, to simulate the input for ship longitudinal pitch control, enhancing the physical significance of the experiment.