Adaptive fractional-order terminal sliding mode control of rubber-tired gantry cranes with uncertainties and unknown disturbances

Using three actuators for tracking five outputs, rubber-tired gantry (RTG) crane is found to be a highly under-actuated system subject to random wind due to working outdoors. Applying fractional calculus to sliding mode control (SMC), we construct an adaptive robust control system for RTG cranes under parametric variations and unknown wind. The adaptive feature is achieved by using an estimation mechanism for approximating five crane parameters and wind disturbances. The core of the sliding mode displays robust behavior against uncertainties. For comparison, another robust controller is proposed based on finite-time sliding mode. Simulation and experiment results show the superiority of adaptive fractional-order sliding mode control, in which the controller well tracks actuated states and stabilizes unactuated states despite parametric uncertainties and unknown disturbances. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

This study presents an adaptive robust control system for rubber-tired gantry (RTG) cranes using fractional calculus combined with sliding mode control to deal with parametric variations and unknown wind disturbances. Simulation and experiment results demonstrate the superiority of the proposed control system in tracking actuated states and stabilizing unactuated states, despite uncertainties and disturbances.