Load transfer control for a crane with state constraints

For the problem of controlling a crane with variable rope length, a saturating control is developed that satisfies the constraints on the sway angle of the load and the speed of the trolley. The length of the rope can change at a piecewise constant velocity. The control law is designed based on a linear time-invariant system with a constrained input, obtained applying a feedback compensation and a coordinate transformation to the crane system. The control law has a simple form and is easily implemented; moreover it is robust against modeling errors and observation noise. The effectiveness of the control law is demonstrated by experiments and simulations.