Discrete-Time Optimization of Collision-Free Rotary Crane Motion with Load-Sway Suppression

Load-sway suppression and obstacle avoidance are main tasks in handling heavy objects using rotary cranes for safety purposes. The crane's motion is normally accompanied with undesirable load-sway and constrained by obstacles, which may cause collision and accidents. Therefore, fast and smooth motion without collision is a main demand for reducing operation time and suppressing load-sway. This study proposes a discrete optimization method for collision-free rotary crane motion with suppressing load-sway using a simple nonlinear dynamics. The proposed trajectory can be achieved by two different algorithms; the first one is the A* algorithm, which is used to generate a shortest-distance load path without collisions, and the second algorithm is to generate a time-optimal trajectory for the A* paths under crane dynamics and load-sway constraints. Although many previous works have a similar objective and their trajecto-ries have been generated with minimizing motion time and load-sway, they have several limitations on the trajectory profiles and assigned load-sway constraints. Therefore, a new time-optimal trajectory based on a discrete approach has been designed by dividing the load path into several positions, which are able to be any number of points until obtaining much simpler and practical motion. The proposed trajectory is compared with a polynomial-based trajectory to confirm the effectiveness for suppressing residual load-sway and obstacle avoidance.