Improved extended state observer-based global sliding-mode finite-time control for displacement tracking of a hydraulic roofbolter

The dead-zone nonlinearity and uncertain dynamics inevitably weaken the tracking performance of the displacement system for a hydraulic roofbolter. To solve the above problem, a global sliding-mode controller based on a reduced-order proportional-derivative-type (PD-type) extended state observer (GSMC-PDESO) is proposed. Firstly, the displacement system model of a hydraulic roofbolter is built by using a compensation technique to suppress the effect of dead-zone nonlinearity on control performance. Following that, a novel extended state observer that has less dimensions and few gains than standard one, called reduced-order PD-type extended state observer, is designed, with the purpose of improving the estimation performance and suppressing noise amplification. Moreover, a global sliding-mode unit mainly composed of a novel global integral sliding-mode surface and a novel global sliding-mode control law is developed, which aims to improve global robustness, eliminate the chattering and adverse impact on estimation error of disturbances, as well as provide an effective and continuous control law. By comparing the proposed GSMC-PDESO with ten control methods, the comparative experimental results verify the effectiveness of the proposed GSMC-PDESO and strategies.