Observer-based adaptive robust control scheme of ship-mounted 3-SPS/U parallel platform for wave compensation

Wave-induced ship motions profoundly impact and even threaten the operational effectiveness of ship-mounted equipment. To compensate for the wave-induced ship motions in heave, roll, and pitch directions, this paper proposes an innovative drive scheme and stabilization control algorithm for a ship-mounted 3-SPS/U parallel platform, while accounting for model and parameter uncertainties. Specifically, a dual-valve parallel hydraulic system is employed to drive the platform, enhancing its driving capability and engineering applicability. Furthermore, using the Kane’s method, a comprehensive non-inertial dynamics model is established in the task space, accounting for the influence of inertial forces on the platform. Based on it, by constructing a detailed mechanical-hydraulic model, a novel observer-based adaptive robust scheme is designed using the backstepping method. Specifically, the high-performance nonlinear observer is designed to simplify and solve the complex multi-parameter uncertainties problem in the multi-input non-inertial dynamics model, and the adaptive robust controller is designed to handle the unknown proportional valve dead-zone problem and other nonlinearities, ensuring precise control. The stability of the system is verified through the Lyapunov method, with co-simulation results corroborating the superior compensation performance of the proposed methodology.