| The effectiveness and real-time characteristics of vehicle dynamic stability control are directly affected by the control accuracy of the high-speed on-off valve in braking system.The aim of this study was to improve the safety and operation stability of automobiles.the characteristics of the high-speed on-off valve which was the key component of automotive ESP,was studied and optimized.Thereby,we aim at improving the model accuracy of high-speed on-off valves,enhancing the controllable range of flow rate of on-off valves and solving the pressure regulation problem of ESP system.Firstly,the electromagnetic field model,temperature field model and flow field model of high-speed on-off valve were established,and then the three sub-models were verified by simulation and experiment.Based on the experimental results,the more accurate sub-models were obtained,and then the three sub-models were coupled by the dynamic equation.Mathematical model of flow and pressure in coupled field was established.Current,pressure and displacement response,pressurization and flow characteristics of on-off valves were simulated and experimentally studied.Based on the results above,the coupling field model was modified and the temperature-based electromagnetic force control strategy was proposed.The sub-model of electromagnetic field was studied by means of Maxwell simulation and test of electromagnetic force test platform.The exact relationship between current,main air gap,top air gap of coil case,bottom air gap of coil cover and thickness of shell on electromagnetic force was obtained.Besides,the electromagnetic force model is optimized according to the experimental results.Under specific conditions,The model error rate reduced from more than 10% before optimization to less than 5% after optimization,which greatly improved the model accuracy.The sub-model of temperature field was analyzed by ANSYS simulation and temperature test platform.The temperature distribution of coils in different skeleton materials,different skeleton structures under different duty cycle voltage excitation were described.According to the results of simulation and experiment,the temperature coefficient function of resistance was fitted and the mathematical model of temperature field was optimized.Under specific conditions,the model error rate decreased from more than 12% before optimization to less than 7% after optimization,and the accuracy of the model was improved as well.By optimizing the coil skeleton structure and coil cover size,the temperature of coil reaching thermal equilibrium decreased by about 30-40%,the time increased by 25%,the heat dissipation efficiency significantly improved,thereby the performance of coil working continuously for a long time was increased.The sub-model of flow field was studied by using computational fluid dynamics.The distribution of pressure and velocity field around the valve and the fluid force was analyzed.The effect of opening,cone angle,diameter of the inlet and pressure difference between the two ends of valve on fluid force were studied.Besides,the dynamic test bench of the spool was built to test and study the motion characteristics of the spool.The visualization of the high-speed on-off valve was realized,and the fluid force on the spool in the process of motion was calculated.The experimental results were compared with the theoretical values of simulation and mathematical model,and the fluid force model was optimized by the variable flow coefficient correction method.Under specific working conditions,the error rate of flow force model was decreased from about 12% to less than 5%.The dimensionless decision utility function was used to optimize the structure of the valve.Under specific conditions,the optimized structure enlarged the controllable range of flow characteristics from 22%-43% to 24%-68%,the controllable range increased by about one time,and the saturated range reduced from 43%-100% to 68%-100%,and the controllability was enhanced.The coupled field model was analyzed by the combination between theory and experiment.The electromagnetic force characteristics,the on-off valve current,the pressure and displacement response characteristics,turbocharging characteristics and flow-rate characteristics were quantitatively analyzed.Then,a comprehensive performance test bench for the high-speed on-off valve was built and relevant tests were carried out,which were compared with theoretical analysis and simulation results.Finally,according to the theoretical and experimental results,the influence of temperature on the damping force was corrected.Under specific working conditions,the error rate of hydrodynamic model was decreased from about 5% before optimization to less than 2.5%.The control strategy of the influence of temperature on electromagnetic force was put forward.When the target electromagnetic force was 25 N,the decreasing rate of electromagnetic force with temperature decreased from 52% to less than 2% after adopting the control strategy.In this paper,the multi-field coupling characteristics of the high-speed on-off valve were studied by interdisciplinary approach,i.e.theoretical analysis,simulation and experimental study.The coupling laws among temperature field,electromagnetic field and flow field were revealed,and an accurate mathematical model was established.Besides,the mechanism of the influence of electromagnetic coil heating on electromagnetic force was demonstrated,and a temperature-based electromagnetic force compensation method and control strategy were proposed.Furthermore,by developing a test platform for the dynamic characteristics of high-speed on-off valve spool,a visual research method for the spool was established,and the kinematics and dynamics of the spool of high-speed on-off valve were revealed.This paper provided a method for real-time feedback control of the high-speed on-off valve,and offered technical basis for further study of high-speed onoff valves. |
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