Research On Digital Valves Group Controlled By PWM And PCM

In recent years,with the development of microelectronic technology and people's increasing demand for green and intelligent industry,digital hydraulic technology has gradually become a hotspot of scholars.The core digital hydraulic valves in the digital hydraulic components is studied in this paper.The digital hydraulic valve can be divided into PWM control high-speed on-off valve and PCM control parallel valve group.Among them,PWM control high-speed switching valve has good dynamic characteristics but small output flow,while PCM control parallel valve set has large output flow but poor dynamic characteristics.In this paper,PWM and PCM combined control digital valve is proposed.A digital valve configuration design method based on the optimal matching coefficient is proposed to lay a theoretical foundation for the control optimization of the system.In addition,the time-delay control method is proposed to improve the control characteristics of the system.The specific research contents of this paper are as follows:(1)Configuration designs method of digital valve group.According to the method of flow area division,the principle of equal step length of on-off valve group cod form is putting forward,and then the design method and evaluation indexes of digital valve group configuration are putting forward,including flow deviation,average impact degree,redundancy degree and state switching flow impact degree under various cod forms.On this basis,a method of configuration designs of digital valve group based on the best matching coefficient is proposed.The significance of this method is to provide a quantitative judgment on the matching degree of each cod f orm of the system and lay a theoretical foundation for the control optimization of the system.(2)Modeling and characteristic analysis of high speed on-off valve.The mathematical model and simulation model of electromagnetic field,flow field and mechanical part of high-speed on-off valve are established by using mathematical modeling method,and its dynamic and static characteristics are analyzed.In addition,the formation mechanism of each region in the static characteristic curve is analyzed.On this basis,the functional relationship between each region and duty cycle in the static characteristic curve of high-speed on-off valve is obtained and verified by simulation.The simulation results show that the accuracy is high when the theoretical frequency is not exceeded,but the error increases obviously when the theoretical frequency is exceeded.(3)Research on flow control method of digital valve group.Based on MATLAB / Simulink,the simulation model of digital valve group is established,and through analysis,the impact in the process of digital valve group state switching is caused by the delay of high-speed on-off valve control signal and the delay time of on-off valve group opening and closing.In addition,the impact flow function of different del ay time of opening and closing is derived,which provides theoretical basis of impact compensation control.Based on the impact flow function,the control method based on the control delays and the control method based on the on-off valve delay is proposed to compensate respectively.Finally,the control method based on the cost function is obtained,which provides a feasible scheme for the precise flow control of the digital valve group.