A Hierarchical Sliding Mode Control Method for Bridge Crane System

Bridge crane system is widely used in production and life. Even so, we still have a lot of problems to solve on it, such as trajectory planning for the large vehicle and small vehicle and anti-swing of the hoist. However, the anti-swing problem of the bridge crane system is an issue of great value. A sliding mode control method is designed to solve this problem. Because of the characteristic that the bridge crane system is an under-actuated system, it is modeled on Lagrangian dynamics. The effect of the ordinary sliding mode control method for under-actuated systems is no longer satisfactory. A hierarchical sliding mode control is used instead of the ordinary sliding mode control. For under-actuated systems, the basic idea of the hierarchical sliding mode control method is to separate the driving part and under-acting part of the system into different subsystems. In this control method, the slip surface is divided into two layers. The first layer of slip surface includes two parts: one is the displacement error sub-sliding surface of vehicle, and the other is the suspended swing error sub-sliding surface. The second layer is the total slip surface. It contains two sub-sliding surfaces in the direction of the vehicle. The equivalent input term in the sense of Filippov is obtained according to the sliding mode surface of the first layer, and the switching control function term is obtained from the sliding mode surface of the second layer using the Lyapunov feedback function design method. The total system input can be got by combining the equivalent input term and the switching control function term. The simulation experiment by using the simulation module of Matlab is operated, and the simulation results prove the method has good control effect and robustness.