Output Feedback Control for Offshore Cranes Subject to Ship Rolling Disturbances

Marine crane systems are usually fixed on the ship’s deck. Due to the disturbance of ocean waves, it is often difficult to precisely control the position of the payload. In addition, if a speed sensor is not equipped, it will be difficult to obtain the speed signal for feedback control. To address practical problems related to crane control, such as unmeasurable speed and noise amplification by numerical differentiation, a virtual spring-mass system can be constructed, enabling the achievement of control objectives even without measuring the speed signal. For the complex disturbances caused by ship motion, the dynamic model is transformed by constructing new state variables. Based on this, a pseudo-energy function is constructed, and by designing auxiliary signals, an output feedback control method is proposed. Finally, a rigorous mathematical analysis is carried out, and the effectiveness and robustness of the scheme are verified through simulation.