Multivariable control of 3D movement of an overhead crane with non-linear dynamics: Comparison between Pole-placement & MPC approaches

Document Type : Article

Authors

Department of Mechanical Engineering, Sharif University of Technology, PO Box 11155-9567 Tehran, Iran

Abstract

In nonlinear 4DOFs overhead crane systems, the trolley can move both longitudinally and transversely. To achieve precise control over the trolley's movement and minimize load fluctuations, suitable controllers are essential. This research focuses on developing and implementing two types of controllers: one based on pole-placement theory and another using a model predictive controller (MPC). Designing a pole-placement controller involves linearizing the system, and since the controllability reveals the system to be underactuated, two additional inputs are introduced. These additional inputs help determine alternate poles with desired conditions, and then the controller is designed by eliminating the extra inputs. For the MPC controller, various parameters, such as sample time and prediction horizon, are selected based on design criteria, making the controller functionally applicable. The pole-placement controller achieves rapid system response, exceeding expected input limits. Conversely, the system modeled with the MPC controller exhibits a slower tracking process with a consistent 1º vibration in the suspended load, but it stays within input limits. Furthermore, we compare the response of each controller to uncertainties. As a result, the pole-placement and MPC controllers are found to create a robust system for specific regions and a system with variable vibration frequencies and low amplitudes, respectively.

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