Research On Cylinder Digital Valve Control Technology

Cylinder drive system is widely used in industrial automation because of its simple structure,low cost and easy maintenance.The cylinder controlled by throttle has some shortcomings,such as unable to stop in the middle position,poor speed stability and so on.Using proportional or servo valve control can achieve accurate intermediate positioning and smooth operation of cylinder,but the disadvantage of proportional or servo valve is its complex structure,high price,sensitivity to pollution and so on.Therefore,it is of practical significance to study a simple and inexpensive control element to achieve more accurate intermediate positioning and stable operation of the cylinder under the premise of low cost.Aiming at this goal,an integrated digital valve structure design scheme with simple structure,low cost and small volume is proposed.A series of research has been carried out including the structural design,the mathematical modeling,the control strategy research and experimental research,etc.Firstly,an integrated digital valve structure design scheme is proposed to solve the problems of small output flow and large volume.The structure of a single on-off valve is studied and the parallel connection mode of the switch valve is determined by theoretical analysis.The flow field of the valve is simulated by CFD simulation software to determine the optimal position sequence of the on-off valve.The characteristics of the prototype valve of the integrated digital valve were tested.The maximum flow rate is 106.5L/min,the minimum output flow rate is 4.7L/min,the opening response time is 7.4ms and the closing response time is 10.5ms,which can meet the technical requirements of the integrated digital valve.Through theoretical analysis,the mathematical model of integrated digital valve-controlled cylinder system is established,and the position and speed control strategy of the system is designed according to the characteristics of the system.Based on the mathematical model of the system,the position control and speed control of the integrated digital valve-controlled cylinder are simulated.It lays a foundation for the follow-up experimental research.The hardware required for the system is selected and the system control program is compiled.Then the test system was designed and system debugging was completed.The position control experimental results show that the system has small overshoot,fast response speed,good stability and good dynamic performance when using the PID + fuzzy hybrid control strategy.The repetitive positioning accuracy of the system can reach 0.3mm and the whole positioning time is less than 1.3s.Velocity regression test results show that the velocity fluctuation value of the system is between 0.08 and 0.12 under different working conditions.the velocity fluctuation value is reduced by 70.4%~83.6%,compared with throttle valve controlled cylinder.Cylinder motion smoothness is greatly improved.The integrated digital valve developed in this paper has the advantages of simple structure and small volume.The cost is only about one fifth of the pneumatic servo valve and one third of the proportional valve.It realizes more accurate intermediate positioning and stable operation of cylinder under the premise of low cost.It has broad application prospects.