Position synchronization tracking of multi-axis drive system using hierarchical sliding mode control

The rising trend of large-scale industrial equipment widens the range of the requirement of multi-axis drive system. These systems dynamically track the desired trajectory, which suffer from poor overall synchronization. A control algorithm using the hierarchical sliding mode control is proposed to achieve the synchronization tracking performance for the multi-axis drive system, which is composed of multiple servo valve-controlled hydraulic motors. In the first layer, adaptive backstepping tracking controller and the neural network synchronization controller based on the position average error are investigated to satisfy separately the tracking and synchronization requirement against the uncertainty factors. In the second layer, the global sliding surface based on the two first-layer sliding mode surfaces is defined, in which the switching control law is obtained to guarantee the asymptotic stability of the whole system. The proposed control algorithm can guarantee the overall synchronization accuracy during the dynamic tracking of each axis, which avoids the pull and drag phenomenon among the multiple axes. Finally, the performance of the proposed controller is evaluated by conducting the synchronization tracking experiment test on scraper conveyor, which is composed of three hydraulic motors, xPC control system and sensors.