Pick-and-place trajectory tracking control for cable-driven gangue sorting robots

The cable-driven parallel robots have the advantages of fast moving speed, large workspace and strong dynamic load carrying capacity, so they are employed to perform the pick-and-place operation of the target gangues quickly and accurately. However, due to the flexibility and the unidirectional characteristics of the cables, the cables must be kept in tension all the time, which makes the control of the robots face great challenges. At the same time, the dynamic impact, uncertainty of dynamic parameters, external interference and other factors caused by the process of the pick-and-place the target gangues will inevitably affect the motion accuracy of the end-grab of the robot, and even lead to the failure of the sorting of target gangues. Therefore, a robust adaptive fuzzy control strategy, which can ensure the motion accuracy of the end-grab of the cable-driven gangue sorting robots, is presented to overcome the disturbances of dynamic parameters and the influences of external interference in the process of picking and placing the gangues. Based on Lyapunov stability theory, the stability of the proposed control strategy is proved. The simulation analysis of the proposed control strategy is carried out through a spatial spiral trajectory and practical pick-and-place trajectory for the robot. The results show that the end-grab of the robot has a good tracking effect on the predetermined trajectory, and the maximum position tracking error and root mean square error are 2×10⁻² m and 8.9867×10⁻⁴ m, respectively; and furthermore, the cable tensions are smooth and continuous, which satisfies the constraint conditions of the cable tensions. It is proved that the proposed robust adaptive fuzzy control strategy in this paper is effective and reliable for the trajectory tracking control of the cable-driven gangue sorting robots. This study can lay a good theoretical foundation for the further application of the cable-driven gangue sorting robots.