Switching Control for Load Sway Suppression of a Rotary Crane Using Only Horizontal Boom Motion

The paper deals with automatic load sway reduction for boom cranes, an increasingly important topic in the field due to its use towards increased productivity and safety. Boom cranes are a type of rotary crane, where the load is suspended by a rope from the tip of a boom based at the crane centre. This allows for vertical movement by adjusting the inclination of the boom, and horizontal movement through rotation around the base of the boom. In most research, both vertical and horizontal boom motion are used to control load sway. However, the vertical motion expends more energy as it moves against gravity. Our task is to use only the horizontal motion to perform positioning of the boom and load sway reduction in two directions, thus reducing energy cost. In order to achieve this, a new two mode switching controller is developed, which uses logical arguments to switch between goal-specific modes. Mode 1 focuses on the correct positioning of the boom through the use of a trajectory and a linear quadratic controller, Mode 2 focuses on load sway reduction through the use of a linear quadratic controller. Two different approaches for scheduling the switching times between the modes are developed. The resulting controller is successfully verified both in simulation and experiments on a laboratory crane.