Flatness Based Control of a 3-DOF Overhead Crane with Velocity Controlled Drives

As an example of a spatial manipulator with large work space a 3-DOF overhead crane is considered. A nonlinear model of the overhead crane, including drive dynamics, is derived. The drives of trolley and winch are controlled by velocity controllers. Therefore the dynamics of the drives can be approximated and thus included into the model description. The states of the system are parameterized by the position of the load and its derivatives, therefore a flatness based trajectory tracking controller is derived. The controller achieves good tracking behavior and oscillation damping. It is shown that the controller is independent of the load mass and includes changes of the rope length. The strategy is implemented on an exemplary 3-DOF overhead crane and measurement results are presented.