Electro-hydraulic Proportional Valve Research Articles

Characterization and modeling of a novel electro-hydraulic variable two-terminal mass device

Much effort has been devoted to developing variable stiffness and variable damping devices for semi-active structural vibration control. However, little research has been done for variable inertial mass mainly caused by the mechanical terminal limit of the mass component. Based on the two-terminal mass scheme, we propose an electro-hydraulic approach to realizing a novel device with variable two-terminal mass. In this study, the flywheel that is traditionally handled by one physical terminal is manipulated by two terminals of a hydraulic cylinder-control-motor system. The transmission ratio of the system is adjusted using an electro-hydraulic proportional valve. Through modeling the ideal dynamic behavior, it is confirmed that the equivalent inertial mass between two terminals of the component can be made variable. To further understand its mechanical characteristics, a prototype device is developed and tested on a test rig. Triangular and sinusoidal excitation signals are employed respectively to identify the model parameters. The results show that the proposed model can describe the dynamic characteristics of the variable two-terminal mass device well. The proposed design and modeling schemes pave the way towards the semi-active variable inertial mass control of vibration systems.

The Modeling of Electrohydraulic Proportional Valves

The present work describes the modeling of a proportional relief valve actuated by an electromagnet. Two models were developed and compared each other: a detailed nonlinear model and its linearized version. The modeling approach presented has a general nature and can be applied to various types of electrohydraulic proportional valves (EHPV). The comparison between nonlinear and linear model results shows the limits of the linear approximation to study the real component. Substantially, the nonlinear model is composed by three submodels: the fluid-dynamic model (for the evaluation of the main flow features), the mechanical model (which solves the mobile body motion), and the electromagnetic model (which evaluates the magnetic forces and the electric transient). All submodels are based on a lumped parameter (LP) approach and they implement a specific set of nonlinear equations. However, to carefully model the main electromagnetic phenomena that characterize the proportional electromagnet behavior (including: magnetic losses, fringing effects, and magnetic saturation), a finite element analysis (FEA) 3D model was developed by the authors. The LP electromagnetic model is based on a particular use of the FEA 3D model steady state results. A series of transient simulations were performed through the FEA 3D model in order to quantify the effect of the eddy currents and to determine a second order transfer function used in the linear model to describe the electromagnet dynamics. The remaining parts of the linear model are obtained by linearizing the nonlinear model equations. The FEA 3D model was experimentally validated in steady-state conditions, while the results of the overall model of the valve were verified in both steady-state and dynamic conditions.

Study on Decreasing Vibration of High-Speed Train Semi-Active Suspension System

Lateral semi-active damper is designed by author based on the electro-hydraulic proportional valve, from the perspective angle of improving vehicle comfort; its purpose is to ensure vehicle driving safety. At the same time, the neural network adaptive control strategy is used for joint simulation of semi-active damper. The results show that lateral semi-active damper with the train body has significantly improved compared to the traditional passive lateral damper acceleration.

Study Control System Based on Creep Test in High Density Baler

Hydraulic transmission system controls hydraulic cylinder forward and backward movement freely, in order to achieve high density hydraulic baler work circulation. Creep test required hydraulic system to output constant stress, and study creep tests can not be completed when used succeeding the electrical contact style in the past time. The system used programmable logic controller (PLC) to instead of succeeding the electrical contact style and realized freely forward and backward movement of hydraulic cylinder, electro-hydraulic proportional relief valve can adjust hydraulic system and make it stepless pressure regulation and then degree of automation and reliability in hydraulic control system to be improved. This paper introduces aspects: including the selection, hardware configuration and program of PLC, meanwhile, giving specific realization method. Through the control system to study creep test in hydraulic baler, adopting the National Instrument (NI) company's multi-channel data acquisition card, which type is USB-6251,applying Labview8.2 to write data acquisition program on my own, the versatility and flexibility of system was verified, which was able to complete creep test successfully.

Investigation of Dynamic Performance of an Electro-Hydraulic Proportional System

Proportional and servo valves are used to control the velocity, or force of an actuator. In some cases, two or more parameters have to be controlled. For example, as a cylinder is extended, its velocity might be controlled. At the end of the cylinder’s stroke, the servo system may be used to either position the cylinder or to control the exerted force on thework piece. In present study the dynamic performance of an electrohydraulic system, containing a proportional directional valve, has been investigated theoretically and verified experimentally. The electro-hydraulic system, under investigation, contains an electrohydraulic proportional valve which is used to control a hydraulic cylinder velocity under constant load. The electrohydraulic system consists of a hydraulic tank, a gear pump; a relief valve; a proportional directional valve; a hydraulic cylinder with vertical load; and connecting hoses. Experimental works have been carried out to measure the pump-relief valve characteristics and the pressure losses in the connecting hoses. These measured data have been curve fitted to simulate the characteristic of the pump-relief valve and the connecting hoses. A verified theoretical model of the directional proportional valve, which was previously presented and published in [Menshawy, T.M., “Investigation of Dynamic Behavior of an Electro-hydraulic Proportional System”, M.Sc. Thesis, Military Technical College, Cairo, Egypt, 2006.], has been used here. The simulation model of the hydraulic cylinder with vertical load has been carried out. All these models have been introduced within the MATLAB-SIMULINK environment in order to obtain the theoretical simulation program of the electrohydraulic system operation. The model of the electrohydraulic proportional system has been validated experimentally and has been used to investigate the performance of the system when works under different operating conditions.

Uncertainty learning and compensation: An application to pressure tracking of an electro-hydraulic proportional relief valve

In this paper, uncertainty learning and a compensation technique are incorporated into a classical sliding mode control for a pressure tracking control of a low-cost electro-hydraulic proportional valve. Unknown nonlinear characteristics and disturbances of the valve system can be eliminated and surmounted by the proposed uncertainty compensation and conventional boundary layer technique, respectively. Lumped-system uncertainty is calculated from the first derivative of a sliding function, which can be determined by feeding an equivalent control into the system. It is then used to eliminate the uncertainty of the system. However, this technique requires a proper control distribution matrix. Therefore, a new adaptation of the control gain is introduced. The adaptation law uses a linear combination of magnitude of the calculated lumped-system uncertainty as an adaptive function. As a result, even with an inaccurate actuator model, tracking control is possible and the stability in the boundary layer is guaranteed everywhere outside the uniform ultimate bound, which is dependent on the accuracy of the uncertainty estimation.

Modeling and parameter estimation for hydraulic system of excavator’s arm

A retrofitted electro-hydraulic proportional system for hydraulic excavator was introduced firstly. According to the principle and characteristic of load independent flow distribution(LUDV) system, taking boom hydraulic system as an example and ignoring the leakage of hydraulic cylinder and the mass of oil in it, a force equilibrium equation and a continuous equation of hydraulic cylinder were set up. Based on the flow equation of electro-hydraulic proportional valve, the pressure passing through the valve and the difference of pressure were tested and analyzed. The results show that the difference of pressure does not change with load, and it approximates to 2.0 MPa. And then, assume the flow across the valve is directly proportional to spool displacement and is not influenced by load, a simplified model of electro-hydraulic system was put forward. At the same time, by analyzing the structure and load-bearing of boom instrument, and combining moment equivalent equation of manipulator with rotating law, the estimation methods and equations for such parameters as equivalent mass and bearing force of hydraulic cylinder were set up. Finally, the step response of flow of boom cylinder was tested when the electro-hydraulic proportional valve was controlled by the step current. Based on the experiment curve, the flow gain coefficient of valve is identified as 2.825 × 10−4 m3/(s·A) and the model is verified.

Dynamic characteristics of large flow rating electro-hydraulic proportional cartridge valve

A kind of cartridge servo proportional valve is discussed,which can be used for controlling large flow rate with high performance.By analyzing the structure principle of the valve,the transfer function of the valve is derived.With the transfer function,some structure elements that may affect its performance are investigated.Through the numerical simulation and test study,some principles of optimality and effective methods for improving the dynamic performance of the valve are proposed. The test results conform to the results of the theoretical analysis and simulation,which proves the correctness of the study and simulation works.The paper provides theoretical basis for engineering applications and series expanding design works.

Realization of modularized friction welding measure and control system

The module of pressure measure control circuit and the module of rotation speed measure control circuit based on the microcontroller P89C51RD2 are designed. The closed loop control system of pressure and rotation speed which are two key parameters of inertia friction welding is achieved. The electro-hydraulic proportional relief valve which has a perfect controllable property is used in the hydraulic pressure control system of the friction welding machine. The actual pressure signal sampled by a pressure sensor enters the module of pressure measure and control circuit. Through A/D conversion, computation and D/A conversion, the signal is inputted to the electro-hydraulic proportional relief valve, so that the pressure in friction welding process could be adjusted continuously. The transducer which has a perfect property of speed adjustment is used for main axes motor drive of the machine.The pulse signal of the main axes rotation speed sampled by a photoelectric rotary coder enters the module of rotating speed measure and control circuit. Through computation and D/A conversion, the signal is input to the transducer, so that the main axes rotation speed could be adjusted steadily and exactly. The application of practical production indicate that the control system of pressure and rotation speed is very steady in working, convenient in operating, and has a good effect in running.

Load characteristics of π-bridge electrohydraulic proportional relief valve

A new type electro-hydraulic proportional relief valve with G-πbridge pilot hydraulic resistance network is designed. The principle of the valve operation is analyzed. The construction and parameters of the valve are determined. The steady state equations are written out, which describe the flow pressure performances about the hydraulic resistances and force balance characteristic on the main poppet and pilot poppet. Furthermore, the relational equation of the parameters for the valve with zero override is obtained, which offers the calcula- tion method for the design of the valve. The load characteristic of the valve with different hydraulic resistances is simulated by numerical computation. The new valve is developed and the steady state performance of the valve with different hydraulic resistances is measured. The results of experiment and simula- tion show that load characteristic of the n bridge elec- tro-hydraulic proportional relief valve is much better than tradi- tional proportional relief valve.

비례솔레노이드 액추에이터를 이용한 압력제어밸브

This paper presents an experimental characteristics of electro-hydraulic proportional pressure control valve. In this study, poppet and valve body which are assembled into the proportional solenoid were designed and manufactured. The constant force characteristics of proportional solenoid actuator in the control region should be independent of the plunger position in order to be used to control the valve position in the fluid flow control system. The stroke-force characteristics of the proportional solenoid actuator is determined by the shape (or parameters) of the control cone. In this paper, steady state and transient characteristics of the solenoid actuator for electro-hydraulic proportional valve are analyzed using finite element method and it is confirmed that the proportional solenoid actuator has a constant attraction force in the control region independently on the stroke position. The effects of the parameters such as control cone length, thickness and taper length are also discussed.

Modeling and control of hydraulic excavator’s arm

In order to find a feasible way to control excavator’s arm and realize autonomous excavation, the dynamic model for the boom of excavator’s arm which was regarded as a planar manipulator with three degrees of freedom was constructed with Lagrange equation. The excavator was retrofitted with electrohydraulic proportional valves, associated sensors (three inclinometers) and a computer control system (the motion controller of EPEC). The full nonlinear mathematic model of electrohydraulic proportional system was achieved. A discontinuous projection based on an adaptive robust controller to approximate the nonlinear gain coefficient of the valve was presented to deal with the nonlinearity of the whole system, the error was dealt with by robust feedback and an adaptive robust controller was designed. The experiment results of the boom motion control show that, using the controller, good performance for tracking can be achieved, and the peak tracking error of boom angles is less than 4°.

Electro-hydraulic compound control method and characteristic of control for tension system with high inertia loads

Based on the pressure regulation circuit adopting electro-hydraulic proportional relief valve to control tension, a new type of electro-hydraulic compound control circuit with throttle control unit is presented, which can obtain optimal dynamic damping ratio through real-time altering pressure-flow gain of the throttle control unit, improve the dynamic characteristic of tension follow-up control for the tension system with high inertia loads. Moreover, the characteristic when the cable linear velocity variation causes change of tension is investigated, and a compound control strategy is proposed. The theoretical analysis and experimental results show that the electro-hydraulic compound control circuit is effective and the characteristic of the compound control strategy is satisfactory.

Testing device with opened hydrostatic circuit for dynamic loading of the tractor engine by power take off shaft

The developed loading device with opened hydrostatic circuit for measurement of speed and dynamic characteristics of the tractor engine by power take off is presented. This loading device may also be used as a portable type for field measurement. At present for development of these loading devices controlled hydrogenerators and electro-hydraulic proportional pressure valves directed by computer may by used to adjust geometrical volume of the hydrogenerator from zero to maximum value. There is a possibility to built these devices which consist of one hydrogenerator and one by-pass valve for the maximum power of internal combustion engine 420 kW which is sufficient from the point of view of practical need. Thus optional loading regime may be used according to the tractor engine horsepower to achieve the required accuracy of measurement.

Electrohydraulic Proportional Metering Valve for Common Rail System

In the common rail system with direct injection equipment in diesel engine, a proportional metering valve to control the fuel flow into the high pressure pump is used. The proportional solenoid actuator is suitable for metering valve because it has a constant attraction force in the control region independently on the stroke position and a fast motion response of the plunger. The force characteristics with respect to the stroke of the proportional solenoid actuator is strongly depending on the shape of the control cone, but it is difficult to design the control cone. In this paper, a proportional solenoid actuator of electrohydraulic proportional metering valve for common rail system was analyzed using finite element method and the shape of the control cone of the proportional solenoid actuator was optimized to get the constant force in the control region. The analysis results of the optimized proportional solenoid actuator were compared with the experimental results of the manufactured one.

Development of an unconventional electro-hydraulic proportional valve with fuzzy-logic controller for hydraulic presses

In this study, an unconventional electro-hydraulic proportional flow control valve based on a switching solenoid and a fuzzy-logic controller is proposed for application to hydraulic presses. The main purpose of this study is the attempt to develop an electro-hydraulic proportional flow control valve with lowest cost. Since the switching solenoid possesses quite nonlinear force/stroke characteristics, it is basically not suitable for the development of hydraulic proportional valves. Therefore, the fuzzy-logic controller is employed to linearize the force/stroke characteristics. The basic idea is the utilization of the numerically estimated pseudo-force as the feedback signal. Finally, this newly developed electro-hydraulic proportional flow control valve is installed in a hydraulic press. Experimental results show that the control of the ram velocity of the press cylinder using the proposed electro-hydraulic proportional flow control valve is quite successful.

Model-Following Controller Based on Neural Network for Variable Displacement Pump.

The variable displacement axial piston pump (VDAPP) is inherently nonlinear, time variant and subjected to load disturbance. The controls of flow and pressure of VDAPP are achieved by changing the swashplate angle. The swashplate actuators are controlled by an electro-hydraulic proportional valve (EHPV). It is reasonable for swashplate angle of a VDAPP to employ neural network based on adaptive control. In this study, the nonlinear model of the VDAPP with a three-way electro-hydraulic proportional valve is proposed, and a neural network model-following controller is designed to control the swashplate swivel angle. The time response for the swashplate angle is analyzed by simulation and experiment, and a favorable model-following characteristic is achieved. The proposed neural controller can conduct nonlinear control in VDAPP, enhance adaptability and robustness, and improve the performance of the control system.

A parsimonious model for the proportional control valve

A generic non-linear dynamic model of a direct-acting electrohydraulic proportional solenoid valve is presented. The valve consists of two subsystems—a spool assembly and one or two unidirectional proportional solenoids. These two subsystems are modelled separately. The solenoid is modelled as a non-linear resistor-inductor combination, with inductance parameters that change with current. An innovative modelling method has been used to represent these components. The spool assembly is modelled as a mass-spring-damper system. The inertia and the damping effects of the solenoid armature are incorporated in the spool model. The model accurately and reliably predicts both the dynamic and steady state responses of the valve to voltage inputs. Simulated results are presented, which agree well with experimental results.

RESEARCH ON COMPENSATION FOR VARIABLE DEAD-ZONE CHARACTERISTIC OF ELECTRO-HYDRAULIC PROPORTIONAL DIRECTION VALVE IN POSITION CONTROL

In this paper, a self-learning control stratagem based on digital control is put forward to compensate the variable dead-zone of electro-hydraulic proportional direction valves. Experiments show that the positioning accuracy together with the anti-disturbance ability and the steadiness of the electro-hydraulic proportional positioning system is improved considerably. Being used in real-time control system, the application of electro-hydraulic proportional system is widened in the field of high accurate positioning.

Programmable electrohydraulic mobile valve

Nestepaine Oy has introduced a new electrohydraulic proportional valve, which is also suitable for cheap mobile applications. The valve construction and function is based on a microcontroller integrated in the valve. This paper describes some benefits and new characteristics, which can be offered to the client by using this kind of valve construction.