Intelligent fully mechanised mining faces impose high requirements on the straightness of scraper conveyors, which are essential for improving automation levels and operational safety in underground coal mines. However, motion control of scraper conveyors employs on/off electrohydraulic directional valves, making precise position control challenging. A novel high-pressure large-flow water hydraulic digital flow valve with a dual-pilot valve is proposed in this study to address the aforementioned issues. The pilot valve consists of double two-position three-way ball valves, which achieve independent control of load ports for the main spool. The main valve adopts a symmetric cylinder-type cone valve structure. First, a third-order integrator-type mathematical model of the flow valve is established through coordinate transformation. An active disturbance rejection control (ADRC) controller and an extended state observer designed to estimate and compensate for system uncertainties and disturbances are built for main spool displacement. The stability of the digital valve’s closed-loop control system is verified through inverse Lyapunov methods and disturbance theory. Second, the effects of ADRC parameters on step response performance are studied via simulation, and optimal control parameters are identified. Finally, a prototype of the flow valve is developed, and a corresponding test bench is constructed. Experimental results demonstrate that with the proposed control strategy, the 8-mm step response of the main spool achieves a delay time of 0.076 s, representing a 19.1% reduction compared with the delay time under the proportional–integral–derivative (PID) control algorithm. Moreover, the rise time is reduced to 0.146 s, showing a 50.5% improvement compared with that under the PID algorithm. The proposed system offers other remarkable practical advantages, including strong anti-disturbance capability and high tracking accuracy, which contribute directly to enhanced equipment reliability and operational safety in mining environments.
Zhang et al. (Sun,) studied this question.