Model-based PID control of a crane spreader by four auxiliary cables

Abstract

This article presents the anti-sway and anti-skew control of a container crane that is widely used in cargo terminals. A four-cable suspended spreader is used to load and unload the container. In such a loading/unloading process, the spreader has usually residual oscillation, the sway and skew, due to the motion of the trolley and the gantry or an external disturbance such as wind. Thus, it is difficult to locate the container at the desired position quickly and precisely. In order to suppress the residual oscillation, this article proposes the use of four auxiliary cables added to four main cables. Using null space, the tension of the redundant auxiliary cables, i.e. the optimal tension distribution among four auxiliary cables, is achieved. The inverse dynamic control and a model-based proportional and integral and derivative (PID) control is applied to derive the control law. The effectiveness of the proposed tension assignment for the auxiliary cables and the model-based PID control algorithm are verified by computer simulations.