Electro-hydraulic Proportional Directional Valve Research Articles

Recent advances in control strategies and algorithms for pilot-operated electro-hydraulic proportional directional valves

Pilot-operated electro-hydraulic proportional directional valve is a key hydraulic component to control the motion of large power equipment such as construction machinery and agricultural equipment. The control accuracy and response speed of the valve control element are very important to the performance of the hydraulic system. In this paper, control strategies for dead-zone control and valve control systems are reviewed. In order to eliminate the dead-zone of pilot-operated proportional valve control, the current control schemes for dead-zone detection and dead-zone compensation are summarized, and the control schemes are evaluated. The proportional–integral–derivative-related control, nonlinear control, and robust control of the pilot-operated electro-hydraulic proportional directional valve control system are reviewed, the relationship between the control strategies is analyzed, and the different control algorithms are evaluated. The shortcomings of the research program are analyzed, and the corresponding solutions are proposed. Based on the current research, future research progresses for eliminating the control dead-zone and optimizing control strategies are presented.

Research on the performance of a novel electro-hydraulic proportional directional valve with position-feedback groove

Accurate posture control of hydraulic roof supports, which use pressurized water as their fluid power source, is an important part and research direction of intelligent fully mechanized mining face. At present, the large flow on/off directional valve used on the hydraulic roof support cannot meet the requirement of precise posture control of the roof support. To overcome the conundrum, a novel two-position three-way electro-hydraulic proportional directional flow valve for hydraulic roof support is proposed. The new valve contains two pilot stages and two main spools. The two pilot stages cooperate with each other to control the movement of the two main valve spools, which are the inlet valve spool and the outlet valve spool. The inlet valve spool adopts the Valvistor principle. The valve can realize manual pilot control and electro-hydraulic proportional flow control of the passage P-A, which has been verified by a simulation model. In this paper, the static and dynamic mathematical models of the new proportional valve are established, and the key parameters affecting the valve performances are analyzed and verified by the simulation model. An optimization control scheme is proposed to overcome the influence of supply pressure, P-A pressure difference, and nonlinear interference force on steady-state displacement and response speed of the valve. The results show that this optimization method can significantly improve the response speed of the spool and promote the linearity of spool displacement under a slope signal. In addition, the fluctuation of chamber pressure and spool displacement caused by the discontinuous flow of a fast switching valve is systematically analyzed. The analysis shows that increasing pulse-width modulation carrier frequency is an effective way to reduce fluctuation amplitude. The research provides a new design idea and control method for an electro-hydraulic proportional directional valve of hydraulic roof support.

Experimental and numerical investigations of the ball-screw-type coupling in two-dimensional electro-hydraulic proportional directional valve

To realize rotary and linear motions of a single spool for improving a proportional displacement of the spool, a new structure of ball screw compression–torsion coupling is proposed, which is used in the two-dimensional electro-hydraulic proportional directional valve. Its principal is based on changing the spiral angle of the raceway to magnify the thrust of a wet proportional electromagnet and realize the rotary to linear motion of a single spool. In addition, because of the rolling friction instead of the sliding friction, the friction resistance is reduced. The mathematical model of the valve is established and the characteristics of the valve are simulated and analyzed by MATLAB. Theoretical and experimental results show that the no-load hysteresis of the ball screw compression–torsion coupling is up to 1% under the flutter compensation. At the system pressure of 21 MPa, the flow hysteresis of the valve is less than 5%, and the nonlinear degrees of the input displacement of electromagnet and the output displacement of the valve core are both less than 1%. The width of the valve corresponding to −3 dB and −90° is about 12 Hz, and the step response time of the valve is about 0.45 s without overshoot.

Two-dimensional Electro-hydraulic Proportional Directional Valve

Two-dimensional Electro-hydraulic Proportional Directional Valve

Linear Analysis of Hydraulic Control System of an Electric-Hydraulic Proportion

1780 mm hot rolling transport chain electro-hydraulic proportional hydraulic control system of Shanghai Meishan Iron and Steel Co., LTD. Of Baosteel is taken as an example in this paper. The features, the controlling method, the electro-hydraulic proportional directional valve selection and the decision of the specific circuits of this kind of metallurgical equipment are introduced in this paper.

Hydraulic System Research of the Pumping Unit Based on Electro-Hydraulic Proportional Control Technology

Trapezoidal curve is selected as the hydraulic pumping unit load running speed curve. Designed a new hydraulic system of hydraulic pumping unit according to the electro hydraulic proportional control technology and then expounded its working principle, in which the electro-hydraulic proportional directional throttle valve have been used. The system is feasible on the theory by analyzing its mathematical model. It would meet the requirement of hydraulic pumping unit and realize the advantages of it via controlling the input current signal of the amplifier.