Design And Control Method Of Valve-controlled Asymmetrical Servo Cylinder System

The valve-controlled asymmetrical cylinder system,which has the advantages of small working space,large bearing capacity,simple structure and fast response,is widely used in industrial technology.In order to meet the requirements of high performance occasions,such as high accuracy,high response,high frequency and strong robustness,it is very necessary to carry out the further studies of new design,modeling and control methods on the valve-controlled asymmetrical cylinder system,which has good engineering application value.The valve-controlled asymmetrical cylinder are the object of study in this article,and studies are carried out from three aspects of structure design,mathematical modeling and control strategy.The main contents and achievements are as follows:(1)In view of the overpressure and cavitation phenomenons caused by irrational matching of parameters of servo cylinder and servo valve and the frictional heating problem caused by irrational sealing mode,this study completed the structure and seal designs of the asymmetric servo cylinder according to the optimal load matching and the hydrostatic supporting and sealing mechanisms.Theoretical analysis and simulation research show that the optimal load matching realizes effective matching between output characteristics of power mechanism and load characteristics,avoiding overpressure and cavitation.In addition,the use of the small hole throttle hydrostatic bearing enhances the radial bearing capacity of the servo cylinder and improves the sealing performance of the servo cylinder.(2)Aiming at the influence of initial motion position change of the piston on the natural frequency of long stroke hydraulic servo cylinder system,the static and dynamic characteristics of asymmetrical hydraulic servo cylinder system in two directions of extension and retraction are analyzed.Both calculation analysis and experimental results show that the increase of initial moving position of the servo hydraulic cylinder will lead to gradual decrease of the natural frequency of the system in the forward movement,while lead to gradual increase in the reverse contraction motion.The dynamic response characteristics of the servo hydraulic cylinder system also change greatly at the different piston starting position.(3)Considering the influence of oil compressibility,the mathematical model of the system with variable effective bulk modulus is established.The simulation results show that in the low pressure section,the effective bulk modulus of oil decreases sharply with the increase of gas content,which results in slow response,increasing oscillation and even instability of the system.In the high pressure section,most of the air is dissolved in the oil,and the value of the effective bulk modulus is little difference,so the response characteristics of diffirent systems are very similar.(4)For the control of the valve-controlled asymmetrical cylinder system,proposed a fuzzy adaptive PID control method based on particle swarm optimization(PSO_FPID).The results of simulation and experiment show that PSO_FPID,which combines the high precise advantage of PID controller and the flexible character of fuzzy controller,can effectively suppress the nonlinear influence caused by the system parameters' perturbation and enables the system to maintain a good dynamic and static quality.