| Nowadays,the control method of hydraulic system is generally divided into two kinds,pump control and valve control.Since the application of hydraulic system,pump control and valve control has been occupy their own half of the respective applications,but early with the rising requirements of precision control,valve controlled system applications gradually became more urgent than pump control system,thanks to the general valve control system's control accuracy is higher than that of the ordinary pump control system's sake.However,with the increase of human energy consumption,pump control system saving more energy began to rewin people's attention.Because of the energy,the pump control system eliminates the need for a part of the energy loss caused by the valve control,and this part of the valve control system occupys more than 44% of the energy loss.Therefore,if we can promote the high efficiency to a level that can make us ignore the high precision of the valve control system,various types of hydraulic system can be used by the human in greatly increased number of occasions.Pump control system for open and closed systems can be directly controlled by the constant changeable servo moter.It can directly control the motor or cylinder actuators to do certain actions.Compared with the valve control system,the advantages of the valve control system is simple,which can make full use of the power of the driving machine,the energy being small,the energy efficiency being high.But the disadvantage is that the dynamic characteristics are relatively poor,and the control accuracy is not high.Therefore,if the pump control system and proportional valve controlled organic combination,I believe that not only can significantly improve the control accuracy of hydraulic systems,but also significantly reduce the energy loss of the system.In view of this,this paper aims to seek a reasonable pump-control method and a control algorithm,which can significantly improve the response characteristics of the system and the control precision with direct servo motor driving pump control.In order to accomplish this goal,this paper designs a good system with variable load based on variable speed servo motor control.The system with axial piston pump is directly driven by a servo motor,again by the plunger pump directly driving load through a directional control valve,which directly collects control data from output.For the design of the control system,there being four control algorithm in different working conditions(open loop,a simple closed loop,traditional PID,fuzzy self-tuning PID)under no-load,with-load controlling experiments,the control algorithm is continuous improved according to record,finally obtained the optimal control results and output curve.The paper completed the following specific research work.1)Three-dimensional UG modeling had been achieved for the test bench,built the system test bench from the servo motor drive to the axial piston pump to the valve to the load.During this perieod the paper first analyzed the basic principle of the plunger pump,analyzed the basic control mode of servo motor,which involved the traditional PID control,adaptive control,fuzzy control and iterative learning control,and the organic combination of several control methods of control.The servo characteristics and response characteristics of proportional valve are analyzed.2)First,the servo motor type of the control system is selected,and the necessary proportional valve being appropriate selected.Then the data had been colected under the three working conditions with different speed and load.The verification of the plunger pump is carried out according to the theoretical conclusion.3)Secondly,put on changeable load and set the control target,the data under specified working condition with the controlling characteristics load was tested and recorded.With the analysis of these data the general rules were find out.Compared with the experimental data of three kinds of conditions,the degree of the improvement of the performance of the composite system had been analyzed.4)Analysis of the experimental data had been done,contrasted with the settings control objectives and evaluated control characteristics of the constant speed control.In order to solve the problem of the control characteristics,control algorithm had been rewrited under different control objectives for the variable speed.Their advantages and disadvantages were compared and improved the algorithm according to the record of the data of control characteristic of composite system.5)According to the output curve of the final control results,the gap between the control objectives was analyzed.the possible reasons of the gap were analyzed.Finally the direction that can improve the performance of the composite system was put forward.The pump control system can be promoted to a higher level.The research results and theoretical models and methods,will provide a reference for the subsequent prototype of pump control system.It also provides the basis for the deeper theoretical research and experimental analysis of composite system in a more effective way. |
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