Research On Giant Magnetostrictive Materials-based High Speed On/Off Valve And Its Valve-Controlled Cylinder System

Digital hydraulic technology has the advantages of good robustness;high efficiency;simple and reliable structure of hydraulic control components;and higher flexibility and programmability.High-speed on-off valves are the key components of digital hydraulic technology.At present,the high-speed on-off valves on the market are mostly Solenoid ones.Lower switching frequency is one of the main factors limiting their performance.The bandwidth and the control accuracy of the high speed on/off valve can effectively be improved by combining it with smart materials.In this thesis,a giant magnetostrictive-based high speed on/off valve is designed;moreover,its characteristics and performance in both open-loop and closed-loop systems are studied.Firstly,according to the characteristics of giant magnetostrictive material,its working principle,and the control principle of high speed on/off valves,the structure of a giant magnetostrictive-based high speed on/off valve is designed,and the main functional characteristics and design principles of key components are introduced.Secondly,a hydraulic system with the designed giant magnetostrictive-based high speed on/off valve as the core control component is built.It mainly consists of hydraulic power station,high speed on/off valve,directional switching valve,hydraulic cylinder and corresponding pipelines.Mathematical model of each component is established and simulation model of the open-loop system is established by MATLAB/Simulink.The movement characteristics of the poppet,flow characteristics of high speed on/off valve and the displacement characteristics of the hydraulic cylinder are studied.Furthermore,the position tracking performance of a high speed on/off valve-controlled hydraulic cylinder is theoretically analyzed.Based on the simulation model of the open-loop hydraulic system,the closed-loop position control simulation model of the high speed on/off valve-controlled hydraulic cylinder is established,and the influence of the directional switching valve on the position tracking of various targets under different conditions is analyzed.After minimizing the influence of the directional switching valve on the position tracking performance,the closed-loop position control characteristics of the high speed on/off valve-controlled hydraulic cylinder are studied by simulation.Finally,an experimental test bench of the giant magnetostrictive-based high speed on/off valve is set up.The characteristics of the high speed on/off valve,and open-loop and closed-loop high speed on/off valve-controlled cylinder are studied.The experimental results show that the opening time of the giant magnetostrictive-based high speed on/off valve is less than 0.69 ms,the closing time is less than 0.2ms.When the frequency of the PWM control signal is 200 Hz,the flowrate graph of valve can still maintain a good linearity in the range of 5%-100% duty cycle.When the oil supply pressure is 4MPa,the tracking curve can still keep a good shape for the target signal with peak to peak amplitude of 40 mm and frequency of 1 Hz.In addition,in order to reduce the volume of the giant magnetostrictive-based high speed on/off valve and improve its flow control range,a piston-slice type of hydraulic micro-displacement amplifier is designed.The large deflection model of the slice is established by means of "Qian weichang method" and "S.Way solution".Considering the influence of the effective bulk modulus of oil,the input-output model of the displacement amplifier is established.The simulation and experimental results show that when the input displacement of the amplifier is 0-51.1?m,the output displacement is 0-470?m;thus,the amplification factor is more than 9;The frequency response is about 150 Hz,and the frequency of the first mode is 2888.1 Hz.The main innovations of this thesis are as follows: Aiming at the technical problems of low efficiency,high failure and slow response of traditional proportional servo valve,a high response magnetostrictive digital high speed on/off valve is proposed,its simulation model is established,and a prototype is developed.The simulation and experimental research are carried out.The results show that the proposed high speed on/off valve has the advantages of fast response and can realize hydraulic closed-loop position control.