负载敏感变量泵结构建模与性能分析.

In recent years, to meet the development requirements of green production and energy efficiency of modern agriculture, the closed-center load-sensing hydraulic system has been widely used in the domestic and overseas agricultural machinery because of its low energy consumption and strong adaptability. As a key power component of the hydraulic system of the modern agricultural equipment, the performance of the load-sensing variable pump plays an important role in the performance of the whole hydraulic system. At present, the domestic scholars have mainly concentrated in the optimization and characteristics analysis of hydraulic valve, while have done little about the hydraulic pump. Therefore, this paper focused on the mathematical modeling, performance simulation and testing of the load-sensing variable pump, which was composed of swashplate piston pump, plunger cylinder, pressure control valve, flow control valve, load feedback check valve, and so on. In order to better analyze the performance of the pump, the mathematical models of these parts were established by using the pressure-flow equation, flow continuity equation, force balance equation, and so on. Taking into account the effective travel range of the moving parts such as valve spool and swashplate, the nonlinear mathematical model of the load-sensing variable pump based on the boundary conditions was constructed by using the state space method. Then, the simulation model of the pump was established using MATLAB/Simulink based on the mathematical model. By using the fourth order Runge-Kutta algorithm, the steady-state and dynamic performances of the pump were simulated. At the steady state, the compensating pressure of the variable pump was about 1.6 MPa. And in the dynamic state, the outlet pressure and swashplate angle of the pump could respectively follow the step changes of the load and system flow very well, the adjustment time of which was about 0.4 and 0.5 s, respectively. The simulation results showed that the load-sensing variable pump could adjust the inclination angle of the swashplate in real time according to the required flow and pressure of the load, and thus had a good pressure-flow compensation characteristic. Finally, to verify the correctness of the mathematical model and the simulation analysis, an indoor test platform of the load-sensing hydraulic system was built, including hydraulic pump station, proportional control valve, proportional relief valve, flowmeter, pressure sensor, and so on. The dynamic performance test of the load-sensing variable pump was carried out by using the platform. Among them, the step change of the load pressure could be achieved by controlling the proportional valve’s opening pressure, while the step change in flow could be achieved by controlling the spool opening of the proportional relief valve. The test results showed that the load-sensitive pump could output its required flow when the proportional valve spool encountered a step change. And when the load made a step change, the outlet pressure of the variable pump changed almost synchronously with the load pressure. Compared with the simulation results, the steady-state error of the compensation pressure was about 0.1 MPa, which verified the correctness of the nonlinear mathematical model of the load-sensing variable pump. It can be seen that the output flow and pressure of the load-sensing variable pump can be adapted to the load in real time, thus effectively improving the efficiency of the hydraulic system and reducing the system heat, which meets the field work demands of the modern agricultural equipment operation unit. [ABSTRACT FROM AUTHOR]