An Antiswing Trajectory Planning Method With State Constraints for 4-DOF Tower Cranes: Design and Experiments

As a kind of indispensable equipment widely applied in construction sites, tower crane systems have complicated nonlinear dynamical characteristics, which make controller design challenges. Apart from the primary control objective of accurate slew/translation positioning and effective swing elimination, another important task is to ensure the satisfactory state transient performance, and simultaneously, the transportation time also needs to be as short as possible. To solve the above issues, in this paper, a new time-(sub)optimal trajectory planning method is proposed, which is the first solution to generate antiswing trajectories for four-degree of freedom (DOF) tower crane systems with state constraints. In particular, three auxiliary signals are constructed, and the reference trajectories for the jib slew and trolley translation can be obtained by the elaborately designed trajectories related to auxiliary signals. Hence, based on the reference trajectories for the jib/trolley, the payload can be driven to the desired location accurately with rapid payload swing elimination; moreover, the state variables, payload displacement, and their velocities are all restricted within the specific ranges. Finally, a series of hardware experiments are implemented to verify the effectiveness of the proposed method.