Search Results (4)

The hydraulic support liquid supply system provided power for the hydraulic support, serving as the core to ensure safe support of the coal mining face and to maintain continuous, efficient, and stable advancement of the coal mining operations. The hydraulic support faced complex loads while operating on the fully mechanized mining face. To meet the requirement of rapidly following the coal mining machine’s movement, numerous actuators of the hydraulic support frequently performed sequential actions, and the liquid demand of the hydraulic support varied strongly over time, causing the hydraulic system to endure constant pressure and flow shocks, making it difficult to ensure the production efficiency and equipment reliability of comprehensive working face. This study analyzed the pressure and flow characteristics of the liquid supply system during the periodic actions of the hydraulic support. To address the strong time-varying load and liquid demand during the simultaneous actions of the hydraulic support, an Extended State Observer (ESO) was designed for observation and compensation. An Active Disturbance Rejection Control (ADRC) method suitable for the configuration of a rapid pump-controlled liquid replenishment and pressure stabilization system was proposed, and a co-simulation model of the mechanical and control systems was developed by comparing indicators such as the pressure fluctuation amplitude and the execution time of the hydraulic support actions. The pressure stabilization control effects of the ADRC method, the PID control method, and the traditional multi-pump coordinated liquid supply mode under typical time-varying conditions were analyzed and compared. A simulation test system was constructed to validate the results, demonstrating that the ADRC rapid fluid replenishment and pressure stabilization control method can suppress load disturbances, reduce the system pressure fluctuation amplitude by 20.8%, and shorten the hydraulic support operation time by 2.6%. Full article

In order to solve the problems of frequent pressure fluctuations caused by frequent action of the unloading valve of the pump station and serious hydraulic shock due to the variable amount of fluid used in the hydraulic support system of the coal mining face and the irregularity of the load suffered by the system, a pump–valve cooperative multi-mode stabilizing control method based on a digital unloading valve was proposed. Firstly, a prototype of a digital unloading valve under high-pressure and high water-based conditions was developed, and a digital control scheme was proposed to control the pilot valve by a servo motor to adjust the system pressure in real time. Then, an experimental platform for simulating the hydraulic bracket and a co-simulation model was constructed, and the validity of the co-simulation model was verified through experiments. Secondly, a collaborative multi-mode pressure stabilization control method for the pump valve based on a GRNN (General Regression Neural Network) was established to control the flow and pressure output of the emulsion pumping station according to the actual working conditions. Finally, numerical research and experimental verification were carried out for different working conditions to prove the effectiveness of this method. The results showed that the proposed pressure stabilization control method could adaptively adjust the working state of the digital unloading valve and the liquid supply flow of the emulsion pump station according to the working condition of the hydraulic support, effectively reducing the frequency and amplitude of the system pressure fluctuations and making the system pressure more stable. Full article

In order to solve the problem of frequent pressure fluctuations caused by fluid quantity variation in hydraulic support liquid supply systems and the pressure response lag caused by long-distance pipelines, an online updated radial basis function neural network (RBF neural network) control method was proposed for the long-distance liquid supply system. Based on the analysis of the measured pressure fluctuations of the mining face and the process of the stable pressure liquid supply system, the influencing factors of the stable pressure liquid supply flow demand were obtained. The flow set of the stable pressure liquid supply system was established and fitted in the SimulationX–Simulink co-simulation model and the online correction was carried out by using the characteristics of the repeated action of the hydraulic support. Finally, the online updating RBF neural network regulator was established to realize the pressure regulator control of the pumping station, and the experimental platform was set up for verification. The results show that this method can effectively reduce the pressure fluctuations caused by the change in the flow demand of the mining face, and can adjust the flow rate of the mining face, reduce the pressure impact, and improve the efficiency of the machine. Full article

Magnetic-liquid double suspension bearing (MLDSB) is a new type of suspension bearing with electromagnetic suspension as the main part and hydrostatic supporting as the auxiliary part. It can greatly improve the bearing capacity and stiffness of rotor bearing system and is suitable for medium speed, heavy load, and frequent starting occasions. The electromagnetic system adopts PD control, and hydrostatic system adopts constant pressure supply model to adjust and control the rotor’s displacement in real time. Once bearing electromagnetic system fails, the “dropping-collision” phenomenon of the rotor will be triggered in operation process, leading to cracking and shedding of magnetic sleeve plating and magnetic pole plating. Then the operational reliability and stability of MLDSB will be greatly reduced. So in this paper, Firstly, the drop impact-rubbing equation of the single DOF bearing system under four failure models (upper unit failure, lower unit failure, bilateral failure, and power amplifier failure) is established. Secondly, the paper simulates influence laws of different structure and operation parameters (plating/liquid film thickness and oil pocket pressure, bias current) on falling rotor impact-rubbings behavior. The results show that: (1) the degree of “dropping-collision” of the rotor under the four failure models is successively as follows: power amplifier failure > upper unit failure > bilateral failure > lower unit failure. (2) Due to the impact-rubbing damping effect of hydraulic oil, it plays a certain inhibitory and buffering role on the phenomenon of “drop-collision”. The degree and probability of “dropping-collision” of rotor can be effectively reduced by increasing the pressure of oil chamber appropriately. (3) The rotor drop impact-rubbing behavior obtained from the test is basically consistent with the theoretical simulation, and the correctness of the theoretical simulation can be effectively verified. The research provides a theoretical basis for fault prevention and diagnosis of MLDSB. Full article