Adaptive Anti-Swing Control for 7-DOF Overhead Crane With Double Spherical Pendulum and Varying Cable Length

Three dimensional (3D) overhead crane is a typical multi-input multi-output (MIMO) and underactuated mechatronic system. Complex double spherical pendulum dynamics and varying cable length increase the difficulty of the swing suppression control for overhead crane. Moreover, it would be a great challenge for considering friction uncertain and overshoot issues of the actuators. In this article, an adaptive anti-swing controller is proposed for seven degrees of freedom (7-DOF) overhead crane with double spherical pendulum and varying cable length. First, we use Lagrange's method to establish an accurate dynamic model of 7-DOF overhead crane. The complex nonlinear dynamic model includes trolley moving, bridge moving, cable length varying, hook swing and payload swing in 3D space. Then, by analysis the system energy function, an adaptive control method is designed to control the trolley, bridge and suspension cable simultaneously. Moreover, we elaborately design some nonlinear terms (such as overshoot limiting term, adaptive term and anti-swing term), which can be used to handle the actuator overshoots, friction uncertain and unactuated swing suppression. As far as we know, it is the first nonlinear closed-loop controller for 7-DOF overhead crane without any linearization. Finally, a group of the hardware experiment results prove that the proposed adaptive anti-swing controller has better effectiveness and robustness than the existing state-of-the-art controllers.Note to Practitioners-This paper studies the anti-swing control problem of the 7-DOF overhead crane system. To improve the efficiency of overhead crane, the trolley moving, the bridge moving and the payload hoisting/lowing are carried out simultaneously in practice. Due to the complex dynamics of the double spherical pendulum and varying cable length, the anti-swing control of the 7-DOF crane remains an open problem. Moreover, most existing control methods ignore the friction uncertain and actuator overshoot, which is not feasible in practice. To tackle these problems, this paper designs a novel adaptive anti-swing controller, which can solve the issues of friction estimation, overshoot limitation, actuators positioning while suppressing the unactuated swing in the 7-DOF overhead crane system. The control performance of the proposed anti-swing controller is verified on the self-build 7-DOF overhead crane platform in the laboratory. In the future, the proposed anti-swing controller will be applied in the industrial overhead crane system to improve the control performance.