Abstract：Moving-iron proportional electromagnet is the mainstream electro-mechanical converter of electro-hydraulic proportional valve.Its electromagnetic force is not constant to the displacement of iron core.Constancing the force is one of the key jobs for researchers.And because of the existence of iron core, the coil inductance is very large, which is disadvantageous to improve the response speed of the circuit.In order to develop high-performance electro-hydraulic proportional valve / servo proportional valve, A high-performance moving coil proportional electromagnet has been developed based on the study of the moving coil proportional electromagnet and its related theories in the early study stage.A structural scheme of electro-hydraulic proportional valve composed of moving coil proportional electromagnet is proposed.The main performance of electro-hydraulic proportional valve based on the scheme is analyzed.The corresponding experimental research scheme of dynamic and static performance is proposed, and the structural scheme is studied with the test system.The research results show that the structural scheme of moving coil proportional valve that is developed has high dynamic and static performance.The proportional electromagnet has very strict constant force characteristics.The step response time of spool displacement to the 100% input signal is less than 15 ms in the open loop.The research results are beneficial to develop high performance electro-hydraulic servo proportional valve.
In view of the shortcomings of the existing technology of electro-hydraulic servo edge and center position control system extensively used in the strip production line,such as low efficiency of energy utilization,easy heat generation,and production interruption caused by easy failure of core devices servo valve and deviation sensor,the hardware redundancy control principle using two servo valves for master-slave control and combined photoelectric sensor and capacitance sensor for detection of strip deviation is proposed.With this new technology,the probability of failure of deviation rectification system is reduced,and in turn the loss caused by production interruption is decreased.To improve the energy efficiency of the system,the constant flow pump with variable speed drive,cooperated with the energy accumulator,to work in the pressure control mode is proposed.During the research,a redundancy detection principle by using both serial and parallel sensors is formulated.The dynamic and static characteristics and control accuracy of photoelectric detection and capacitance detection are tested.The energy consumption and dynamic response performance in the deviation rectification process of hydraulic pump with variable speed drive and that with constant speed drive are compared;and the deviation rectification process of system under continuous disturbance is tested.The research results show that with the new control scheme,the requirements of dynamic and static performance during deviation rectification can be satisfied on the basis of reducing 70% of system energy consumption,thus reaching the expected goal.
A new scheme for electrohydraulic proportional servo valves with switching solenoids was presented. A method of the adaptive feed forward compensator (AFFC) to correct static nolinear characteristic of the switching solenoids is proposed based on closed loop control. The transient time duration is shortened significantly by using the anti-saturation integral control (ASIC) techniques, while the static error is maintaining at zero. The principles of AFFC and ASIC are explained theoretically and tested in experiments. Moreover, the results show that the transient time duration is even shorter when the gain of the close feedback loop was increased in the scheme, the scheme has the advantages of simple design and low cost.
Due to the limitation of the proportional solenoid which is costly,with complex magnetic circuit and high processing technique,the switching solenoid may replace the proportional solenoid to control the electro-hydraulic proportional valve,and possesses quasi-constant force characteristics as well.As the strong non-linear characteristics of switching solenoid,it's difficult to obtain mathematics analytic expression between the electromagnetic force and stroke.Bilinear interpolation algorithm was introduced to calculate the switching solenoid output force at any position.Based on the magnetic hysteresis theory of soft magnetic material,the nonlinear characteristic was improved with two-way adjustment of core voltage.Force features in the effective stroke became flat,and the hysteresis effect was decreased.Experimental results show that the introduction of new ways to make the switching solenoid with the proportional solenoid electromagnet to achieve similar control effect.
Due to the influence of material characteristics and winding power, single output electromagnet has limited ability to improve the dynamic characteristic of electro-hydraulic valve. Therefore, an electromechanical converter with double push rods is proposed in this paper, which can simultaneously output two electromagnetic forces, can push or pull the valve core and sleeve according to the current direction and realize rapid operation of load. According to the electromagnetic principle and the magnetic circuit analysis method, the mathematical model and equivalent circuit of the electromechanical converter with double push rods are established. Through the finite element simulation model of the electromechanical converter with double push rods with the same magnetization directions, the changing rules of its magnetic field distribution and force–displacement behaviors are studied and analyzed. According to the analysis results, the electromagnetic mechanical parameters and mechanical structure of the electromechanical converter with double push rods are determined, and the prototype is made. The test platform for the push-pull characteristics of the electromechanical converter with double push rods is built, and its static and dynamic characteristics are tested and analyzed. The results show that the thrust and pull output characteristics of the internal and external push rods are basically consistent with the simulation output, and proportional to the current density of the coil; the push-pull hysteresis of internal and external push rods output force is less than 5%; and the dynamic time response characteristics of the displacement and force are obtained. The hysteresis effect of output force is improved effectively through the H bridge drive control circuit modulated by PWM. Compared with the displacement response of a single-winding electromagnet with a similar volume, it can effectively improve the dynamic displacement response. Follow-up work will further optimize the structure of the electromechanical converter and test the corresponding pilot valve. The research results provide a new theory for improving the output characteristics of electro-hydraulic pilot valve and have an extremely high engineering application value and broad application prospect.
To improve the efficiency of proportional solenoid analysis, a novel analysis method for complex magnetic circuit of proportional solenoid combining magnetic circuit analysis method with finite element method (FEM) is proposed. The FEM analysis results of proportional solenoid's complex magnetic circuit were fitted with algebraic equations. These equations were applied in simulation software which can directly use algebraic equations. The output characteristics of proportional solenoid were analyzed. With comparing the results of simulation software and FEM analysis software, it was proved that complex magnetic circuit can be quickly and accurately analyzed with this method.
A novel 2-degree-of-freedom electro-mechanical transformer (2-DOF EM) with two moving parts was proposed to meet the high speed response of electro-mechanical transformer required by servo proportional valves. The principle on which it decreased the response time of a servo proportional valve was explained. Three of its several possible structures were introduced. The magnetic circuit of one typical structure, a hybrid two-input 2-DOF EM was analyzed, and its output characteristics in every case were derived with finite element method (FEM). Analysis results indicate that the 2-DOF EM can control the two linear moving parts simultaneously, drive them to move in the same or opposite direction. It can be used in the control of servo proportional valves and other equipments which have two linear moving parts.
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