| As the most important element in a hydraulic control system, the servovalve is both an electro-hydraulic converter and power amplification, and it’s the characteristics and reliability determine the performance of hydraulic control system. So, to improve the performance of hydraulic control systems, it is essential to develop new types of servovalves based on new technology and new materials.With the development of smart materials, the new type electromechanical actuators based on smart materials appeared which have the following characteristics of high reliability, large energy density, fast response speed, broad response bandwidth, and large blocked force. Making these smart material electromechanical actuators as the control element of the servovalve by replacing the torque motor to realize the improvement of the performances of servovalve has become a research hotspot in fluid control valves. A novel deflector-jet servovalve is presented in this research by applying the giant magnetostrictive actuator in the deflector jet servovalve for driving the deflector jet hydraulic amplifier. The basic theory of deflector jet servovalve and giant magnetostrictive actuator is researched by multidisciplinary approach and multi-physical field analys is, modelling and simulating with computer, finite elements numerical simulation. In addition to the theoretical research, the performance characteristics of deflector jet servovalve driven by giant magnetostrictive actuator were measured by experiments, and the static and dynamic characteristics of the novel deflector jet serovalve were given.The work in this research comprises the following six parts:The first part illustrates research background, problem statement, state of the art, and the research work of deflector-jet servovalve driven by giant magnetostrictive actuator.The second part introduces the application characteristics of giant magnetostrictive material and the optimal theory of deflector jet servovalve driven by giant magnetostrictive actuator, and its s tructure is proposed based on the application characteristics of giant magnetostrictive material. Through multidisciplinary approach and multi-physical field analysis, the following results can be obtained:(1)the unevenness of the magnetic field distribution of the giant magnetostrictive rod’s axis is more than the value in its direction;(2) the temperature increment of the giant magnetostrictive rod is less than 0.1℃ and the giant magnetostrictive actuator ’s displacement error from temperature change is less than 0.1μm if the flow rate of oil surrounding the giant magnetostrictive rod is more than 0.1m/s;(3) the taper angle of jet nozzle is 13.4°, the included angle of the receive holes is 30°,the distance from the jet nozzle to receiving surface equals to 0.63 times the value of diameter of the receive hole, and the area ratio between the receive hole and the jet nozzle is 1.6.The third part gives the nonlinear model of giant magnetostrictive actuator and its performance. Based the relationship between complex permeability and magnetization, the nonlinear dynamic model with magnetic hysteresis and eddy current is improved. The simulation and experiment show the output displacement is 20.2 μm and the rise time is 3ms at the input currret of 1 A, and the steady state error between simulation and experiment is less than 0.4μm; the rising time of step response is about 1.32 ms and the output displacement is 10μm at the control current of 0.5A; the bandwidth(-3d B) is more than 150 Hz at the control current’s amplitude of 1A, and the bandwidth(-3d B) can reach up to 550 Hz at the control current’s amplitude of 0.25 A.The forth part is the work about designing the power amplif ier and inverse compensator. Based on the performance requirements of the power using in giant magnetostrictive actuator and servo amplifier using in serovalve, a new-style power amplifier is designed for giant magnetostrictive actuator applied in serovalve. The simulation and experiment show under rated load, the linearity of power amplif ier is 3.3%; the settling time of step response is less than 0.5ms at output current of 2A. Based on the dynamic inverse model with hysteresis, eddy current and anomalous loss, the inverse compensator for nonlinear of giant magnetostrictive actuator is given. The experiment shows with the help of inverse compensator, the linearity between input control signal and the output displacement can be improved significantly.In part 5, the model of deflector-jet hydraulic amplifier is discussed in detail, and the model is verified and modified by numerical flow simulation. After the working principle and the model of flow area are given, two models are derived based on momentum theorem and the law of orifice flow, respectively. The simulation results show that at the diameter of jet nozzle 0.6mm and the diameter of receive holes 0.8mm, the distance between the jet nozzle and receiving plane changes from 0 to 0.6mm, if the displacement of the jet nozzle is less than 0.03 mm, the performance of deflector-jet hydraulic amplif ier can be held.Under the design parameters, the simulation result of the model based on the law of orifice flow shows the maximal dimensionless pressure is 0.65, the maximal dimensionless flow rate is 0.7, and the simulation result of the model based on momentum theorem shows the maximal dimensionless pressure is 0.8, the maximal dimensionless flow rate is 0.5. Compared with the results of numerical simulation, it shows that at the displacement of the jet nozzle ranging from 0 to 100μm, the pressure value obtained from the model based on the law of orifice flow is needed to multiply a factor of 2.2 for correction, and the flow rate value obtained from the model based on momentum theorem is needed to multiply a factor of 0.7 for correction.In the last part, the theoretical and experiments performances of deflector jet servovalve driven by giant magnetostrictive actuator are given. The theoretical performances show at the supply pressure of 7MPa and the control current changing from-1A to 1A, the theoretical control pressure ranges from-0.6MPa to 0.6MPa, and the theoretical control flow rate ranges from-0.10L/min to 0.10 L/min; the rising time of step response is 3ms at the control current of 1A,and the rising time is less than 1ms at 0.25A; the bandwidth is less than 200 Hz at the control current’s amplitude of 1A, and the bandwidth is more than 550 Hz at the control current’s amplitude of 0.25 A.The static experments results show that at the supply pressure of 7MPa and the control current varying from-1A to 1A, the increment of control pressure is 0.92MPa; the output pressure to control current curve is at the linear ity of 40%, the hysteresis of 52.8%, the threshold of 12.8%, and null bias of 20%, but with the help of inverse compensator, the performance is improved with the linearity of 12%, the hysteresis of 16.8%, the threshold of 10% and null bias of 5.8%。When the control current varies from-0.5A to 0.5A, the increment of control pressure is 0.39MPa; the output pressure to control current curve at the linear ity of 6.2%, the hysteresis of 23%, the threshold of 3.12%, and null bias of 3.42%, but the corrected performance of deflector jet servovalve driven by giant magnetostrictive actuator is at the linearity of 5%, the hysteresis of 9.6%, the threshold of 3%, and null bias of 2.9%.The dynamic performance tests of deflector jet servovalve driven by giant magnetostrictive actuator show that at the supply pressure of 7MPa, the output pressure is 0.92 MPa and the rising time is about 5ms at the control current stepping from-1A to 1A; at unit step response, the output pressure is 0.37 MPa and the rising time is 3ms; when the control current stepping from 0 to 0.25 A, the rising time of step response can be reach 1.05 ms and the output pressure is 0.076MPa; the bandwidth(-3d B) is less than 150 Hz at the control current’s amplitude of 1A, and the bandwidth(-3d B) can be up to 400 Hz at the control current’s amplitude of 0.5A, but the waveform isn’t distorted at the frequency of less than 300 Hz.This research work was supported by the National Natural Science Foundation of China(grant number 50805080, 1175243); the Aeronautical Science Foundation of China(grant number 20090752008, 20110752006); and the development Foundation of State Key Lab of Fluid Power Transmission and Control(grant number GZKF-201116). |
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