Cascade NMPC-PID control strategy of active heave compensation system for ship-mounted offshore crane.

In this paper, the problem associated with active heave motion compensation during heavy-lift operations performed by ship-mounted offshore cranes beneath rough marine environment is investigated. To effectively decouple the correlated motion of the suspended payload from the support vessel via the secondary regulated active heave compensation (SRAHC) system, a novel hierarchical control strategy is proposed by integrating a cascade control structure with an adaptive robust control scheme that incorporates a vertical motion forecast algorithm based on autoregressive integrated moving average (ARIMA) model, a conventional proportional-integral-derivative (PID) framework, and a nonlinear model predictive control (NMPC) method. The introduction of the cascade structure is motivated by its prompt error response against control lag and efficient system order reduction for computational burden alleviation, which forms a crucial foundation for the NMPC-based real-time regulation of PID gains, ensuring optimal evolution of the SRAHC system while improving its practical feasibility. Furthermore, the enhancements in heave compensation and trajectory tracking performance, noise resistance, constraint satisfaction, and engineering application potential of the proposal are demonstrated through a thorough comparative analysis conducted in a practical co-simulation research system. • A novel hierarchical control strategy is proposed for the secondary regulated active heave compensation system. • A joint mechanical-electrical-hydraulic research system is employed for practical heave compensation analysis. • NMPC-PID is retained to ensure superior compensation accuracy, accounting for system nonlinearities and model constraints. • The response speed and computational efficiency of NMPC-PID are enhanced through the introduction of a cascade control structure. • The noise resistance performance of cascade PID controller is improved by the NMPC-based regulation mechanism, synthesized with an ARIMA-based heave motion prediction. [ABSTRACT FROM AUTHOR]