Sliding mode control method suitable for variable-rope-length double-pendulum ship crane

The invention provides a sliding-mode control method suitable for a variable-rope-length double-pendulum type ship crane, and aims to solve the problems that a nonlinear ship crane system is poor in anti-pendulum effect and low in response speed due to a traditional linear control method. The method comprises the following steps: firstly, under the condition that the length of a cable can be changed and the quality of a lifting hook cannot be ignored, establishing a kinetic model of the ship crane with the double-pendulum characteristic, then, estimating and compensating unknown wave bounded interference by adopting an interference observer, and finally, calculating the dynamic model of the ship crane. And a sliding mode surface containing a lifting hook swing angle derivative and a load swing angle derivative is constructed according to the drivable state vector of the system so as to ensure that the state output of the system is corrected as soon as possible, and control laws based on the trolley position a