Nonlinear Motion Control of Underactuated Three-Dimensional Boom Cranes With Hardware Experiments

In practical applications, boom cranes are widely used as useful transportation tools in various fields, owing to such advantages as high flexibility, good mobility, strong operability, and so on. As a typical nonlinear underactuated system, a boom crane presents complicated dynamical characteristics mainly due to its complex multidimensional movements like rotational motions, pitching motions, as well as payload swings, which brings much difficulty for controller design. In this paper, a new nonlinear controller is proposed for underactuated boom cranes. Specifically, the presented control scheme can achieve 2-D rotary positioning and 2-D swing suppression simultaneously, with an additional coupling term as well as an overshoot-limiting term being incorporated to increase the transient performance. Consequently, the asymptotic stability of the closed-loop system's equilibrium point is proven by utilizing Lyapunov techniques and LaSalle's invariance theorem. To the best of our knowledge, the proposed approach is the first closed-loop control method to solve the positioning and anti-oscillation problem for 3-D boom cranes without needing to linearize the original nonlinear dynamics for controller design or analysis, which is of great significance. Finally, hardware experimental results are presented to demonstrate the efficiency of the proposed control method.