Adaptive Sliding Mode Control Based on Time-Delay Estimation for Underactuated 7-DOF Tower Crane

Tower cranes are complex multi-input multioutput underactuated mechatronics systems. The anti-swing control issue of tower crane with varying suspension cable length and double spherical pendulum effect is still open. Furthermore, the system parameters uncertainty makes it more challenging to implement anti-swing control. In this study, we present an adaptive sliding mode anti-swing control approach based on time-delay estimation for underactuated tower crane with varying suspension cable length and double spherical pendulum effect. First, we employ the Lagrange’s method to develop a seven-degree-of-freedom (7-DOF) tower crane dynamic model that comprehensively accounts for jib slewing, trolley motion, payload hoisting/lowering, and payload/hook spherical swing within a three-dimensional (3-D) space. Then, a sliding mode surface is constructed by analyzing the nonlinear coupling relationship between the unactuated states and actuated states. The time-delay estimation technique with adaptive scheme can adapt and predicate unknown system parameters online. An adaptive sliding mode anti-swing control method with time-delay estimation is designed for 7-DOF tower crane system subject to the parameter uncertainties. The convergence of the closed-loop control system is carefully demonstrated through the Lyapunov stability theory. Finally, the hardware experiments verify the anti-swing control performance and robustness of the designed adaptive sliding mode controller. The superiority of the proposed adaptive sliding mode anti-swing controller is confirmed by a decrease of at least 42.09% and 58.33% in the maximum and residual payload swing, respectively, over state-of-the-art control methods.