The Design And Research Of Direct Drive Proportional Cartridge Valve

As a core element in electro-hydraulic control system,electro-hydraulic proportional/servo valve is widely used in industrial applications.Proportional/servo cartridge valves basically have two or three grades of structures with a high-performance servo valve as its pilot stage.Usually these valves have complex structures,and they are sensitive to oil pollution,cost a lot in manufacture and maintenance.With the continuous improvement of the performance of AC servo system,AC servo motor fully demonstrated its advantages of high accuracy,high dynamic performance,and high reliability and so on,which also further expand its application fields.In the field of electro-hydraulic control,AC servo motor is considered to be an ideal electricity-mechanical conversion element due to its typical characteristics such as closed/semi-closed loop control,low inertia with large torque,suitable power weight ratio and reasonable performance price ratio.In this project,a permanent magnet synchronous motor(PMSM)is used to directly drive the main stage of cartridge valve.Thus,the direct-drive proportional cartridge valve with PMSM is developed,and meanwhile,some key technical issues have been solved.In the first chapter,the research reviews among proportional cartridge valves,direct-drive hydraulic servo valve and direct-drive hydraulic valve with PMSM are summarized and compared.For the existed problems of proportional cartridge valve,the significance of direct-drive proportional cartridge valves with PMSM is raised.And then the research objectives and contents of this subject are confirmed,which pointed out the direction of future work.In the second chapter,the basic scheme design of the valve is completed,and a series of principle study on direct drive valve is conducted.In order to directly drive main stage of cartridge valve with PMSM,the key technical issue lies in decreasing the control difficulty by reducing or compensating the steady-state flow force in spool.Thus,the mechanical properties of the main spool need to be studied,the magnitude of steady flow force in spool should be figured out.Using theoretical analysis and simulation tools,the flow force's dynamic characteristics of cone valve under inlet flow is analyzed,the nonlinear saturation characteristic of flow force is proposed,and finally one kind of structure is designed to achieve the compensation of flow force in cone valve under outlet flow.All above work provide theoretical support for valve design.In the third chapter,the mathematical models of each module of the system are established on the base of the design of direct drive proportional cartridge valve.Valve design includes overall scheme design and the selection and check of servo motor and ball screw.The vector control model of servo motor and the mathematical model of the whole system are built.In the fourth chapter,the control strategy of direct drive proportional cartridge valve was studied.Firstly,the parameters of current loop,velocity loop and position loop of servo motor are designed,and the effects and characteristics of different design methods are also be estimated;and then the parameters of screw drive system are calculated.Eventually the whole model of system is established in Matlab/Simulink.In the fifth chapter,experimental methods were taken to analyze the direct-drive proportional cartridge.The steady flow force of cartridge with a 40mm dimension of spool was test.The experiment results fit well to theoretical analysis.Finally some specifications of the direct-drive proportional cartridge were test under no load and load.In the sixth chapter,the main work of this project are summarized and some existing problems and furthermore research issues have also been proposed.