Application Research On The Electro-hydraulic Proportional Servo System

The electro-hydraulic proportional servo system is widely used in the field of metal processing equipment,metallurgical machinery,engineering machinery and drive,with its advantages of simple structure,convenient operation,easy control and suitable for highpower,etc.The nonlinear factors such as variable flow gain and dead zone exist in the electrohydraulic proportional servo system which make it difficult to obtain good control effects.The dissertation makes research on the electro-hydraulic proportional servo system and establishes a mathematical model of it.In addition,the control strategy is made to achieve the positioning control and tracking control.What's more,the construction of the experimental platform and the software design are completed in order to finish the experimental research and analysis.In chapter 1,the emergence and development of electro-hydraulic proportional technology are introduced.The features of the electro-hydraulic proportional control system and electro-hydraulic proportional valve are also elaborated.The application researches of the electro-hydraulic proportional servo system at home are included,too.And the advantages and disadvantages of the intelligent algorithm in the researches are explained.The nonlinear problem and the research content of the system are analyzed.In chapter 2,the dissertation builds a model of the electrohydraulic proportional servo system.At the same time,owing to the analysis of the mathematical model of each module,the transfer function of each module is obtained,which can deduce the block diagram of the total system.According to the mathematical model,the system features are analyzed.In chapter 3,the composition and basic working principle of the electro-hydraulic proportional servo system are analyzed.And the hardware of the project is selected.For the sake of accomplishing the construction of the hardware platform,the input,output and connection must be clear.In chapter 4,the dissertation explains why the project selects Visual C++ as the software platform of the system and shows the design of man-machine interface.From the principles of the PID control and fuzzy control,the dissertation puts forward the Fuzzy-PID Composite Control and analyzes its control principle.The project is focused on the design method of fuzzy controller.Besides,a method for linear compensation of electro-hydraulic proportional valve with dead zone is proposed which is variable gain method.In chapter 5,some experiments are conducted on the actual closed-loop system.Under the condition of no-load,the experiments of the positioning control and tracking control are carried out with PID algorithm,fuzzy algorithm and Fuzzy-PID Composite Control algorithm respectively,which conclude that the Fuzzy-PID Composite Control can achieve the best control effect.By the way,the control effects of the control algorithm are tested in the tracking control under different frequencies.Subsequently,under the condition of the load,the dissertation verifies the effectiveness of the compound control algorithm.Lastly,the factors which influence the control accuracy of the system are analyzed,such as proportional valve dead-zone,friction,inertia load and hysteresis.