Research on high water-based digital valve with dual-spool and control strategy

The straightness control of the working face is the key technology to realize intelligent production of coal mines. However, the discontinuity of on–off hydraulic components of the existing underground working face cannot meet the needs of intelligent straightness control. A new type of dual-spool high water-based digital valve with a motor ball screw as the driving element is proposed as a solution to this problem. In this paper, the force of the valve is firstly analyzed, and it is found that the force of the movement of the valve core can be equivalent to the disturbance of the motor. The control of the valve core is essentially displacement control. In addition, a mathematical model of the valve is established, and sliding mode control with a high-gain observer is proposed to overcome time-varying characteristics of the load. Theoretical analysis indicates that the proposed controller ensures asymptotic stability with existing uncertain disturbances. Moreover, a system based on MATLAB/Simulink simulation model is developed to further verify the performance of the proposed algorithm. Compared with traditional sliding mode control and proportional integral derivative, the proposed algorithm can still improve the tracking accuracy and robustness along with 0.05 mm error under strong time-varying interference. The valve reaches the required flow in around 0.2 s, which is sufficient for the majority of work surface application situations. The research proposes a novel design concept and control approach for straightening coal mine scraper conveyors.