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Overhead cranes are essentially a kind of complex underactuated nonlinear mechanical systems, and it is a challenge to design an anti-swing controller for overhead cranes, hence, many people design controllers of overhead cranes ignoring the changing of the rope length and other parameters. In this study, we propose a multi-sliding mode controller to solve the problem of anti-swing and positioning controller for an overhead crane with rope length variations. This controller can provide a simultaneous trolley-position regulation, sway suppression, and load hoisting control. Also, this paper adopts a new method to decrease the chattering of the control input. Stability analysis of the proposed controller is given in the paper. The proposed controller does not rely on the accurate knowledge of overhead crane system model, and it is simple and easy to apply, and robust to disturbances. The simulation results show the good performance of the proposed controller.

Compared with a traditional single-container overhead crane, the double-container overhead crane is a type of new efficient container stevedoring machinery, however, it is actually a complicated nonlinear system. In this brief, both the kinematic and dynamic characteristics concerning the double-container crane are investigated, and then an accurate dynamic model of the underactuated double-container overhead crane is established by utilizing Euler-Lagrange's method. Not only is the variation of the rope and payloads, but also some uncertainties such as mechanical frictions and air-resistance in the environment are taken into account in modeling. Simulation results show the validity of the established double-container overhead crane model.