Research On The Flow Control Method Of Electro-hydraulic Pro-portional Valve Based On Flow Soft-sensing

Electrohydraulic proportional valves are widely used in hydraulic systems such as construction machinery,and one of their core functions is to proportionally control the valve port flow rate based on input electrical signals to achieve control of the actuator speed.Due to defects such as large volume and slow response of flow sensors,it is not possible to directly use flow sensors to measure and feedback valve port flow.To address this issue,the valve port flow formula is usually used for flow calculation,which indirectly obtains the valve port flow,namely the flow soft measurement method.In existing soft measurement methods for valve port flow,the flow coefficient is considered a fixed value related to the shape of the valve port,but the actual valve port flow coefficient is a variable related to temperature,valve port flow area,and valve inlet and outlet pressure drop.In this paper,a new structure of a high-speed on-off valve bridge pilot electro-hydraulic proportional valve is taken as the research object,and the valve port flow simulation based on CFD(computational fluid dynamics)method is proposed.By simulating and obtaining valve port flow rates under different valve port opening,pressure drop,and temperature conditions,the equivalent valve port flow coefficient was obtained through experimental correction,which improved the accuracy of valve port flow soft measurement.In response to the problem of slow speed in traditional table lookup methods,the binary iteration method and piecewise function fitting method were applied to calculate the equivalent flow coefficient table lookup,and this method was applied to flow closed-loop control,achieving flow control of electro-hydraulic proportional valves based on this flow soft measurement.The specific research content is as follows:(1)Based on CFD flow field simulation,Solid Works was selected to model the main valve in 3D and capture the 3D model of the fluid domain.The fluid domain model of the main valve is meshed using ICEM,and finally,the grid is imported into Fluent.By setting boundary conditions,the valve outlet flow values are calculated under different valve core openings,different oil temperatures,and different valve inlet and outlet pressure drop conditions.Finally,the experimental results of the valve port flow rate proved that the experimental data had a high overlap with the simulation data.Based on the analysis of the experimental results,the simulation data was subjected to flow compensation.After flow compensation processing,the maximum error between all experimental data and the corresponding simulation data under corresponding conditions was less than 6.1%,and the average error was 0.97656%.The experimental results prove that the simulation results have high credibility.(2)This article proposes the concept of equivalent flow coefficient and calculates the equivalent flow coefficient under corresponding boundary conditions through the flow formula,and tabulates it.By interpolating and simplifying the equivalent flow coefficient table,the accuracy of the equivalent flow coefficient can be effectively improved.The experimental results show that through interpolation and simplification,the accuracy of flow closed-loop control based on table lookup feedback can be improved by up to 46.7%,and the accuracy of flow closed-loop control based on segmented function fitting feedback can be improved by up to 33.875%.(3)In response to the problem of slow speed in traditional table lookup methods,this paper proposes a table lookup interpolation calculation method based on the binary iteration method and an equivalent flow coefficient interpolation calculation method based on the piecewise function fitting method.Compared to traditional table lookup methods,the above two methods can effectively improve the speed of obtaining an equivalent flow coefficient.(4)Based on the above two methods for obtaining equivalent flow coefficients,a closed-loop control method for the flow of electro-hydraulic proportional valves is studied,and an extrapolation method for the equivalent flow coefficient when the valve core is in the zero position is proposed.And it has been proven that both flow closedloop control methods have the advantages of speed and accuracy.The experimental results demonstrate that under the accuracy conditions of the equivalent flow coefficient table in this paper,the flow closed-loop control based on piecewise function fitting feedback has high accuracy,with a maximum flow error of 9.25% and a minimum flow error of 2.1%.However,after further improving the accuracy of the equivalent flow coefficient table,the piecewise function fitting method has a faster speed than the binary iteration method,and the accuracy of the binary iteration method is slightly better than the piecewise function fitting method.