Electro-hydraulic Control Valve Research Articles

Evaluation of Hydraulic Characteristics of Electrohydraulic Proportional Valve (EHPV) for an Auto-Steering Tractor Application

The performance of the electrohydraulic proportional control valve (EHPV) employed in a tractor’s automatic steering system directly influences the steering performance. To develop a highly reliable EHPV, it is essential to analyze the hydraulic characteristics of the EHPV for several working conditions of tractors. This study aimed to measure and analyze the hydraulic characteristics of the EHPV according to tractor working conditions. The flow rate and pressure data of the EHPV were computed through the valve measuring system, and the required power was computed. The experimental conditions were selected based on engine rotational speed and tractor steering angle. As a result, it was discovered that the flow rate, pressure, and power all increased when the engine rotation speed and steering angle conditions increased. Furthermore, the rates of increase in flow rate, pressure, and power based on the increase in the steering angle were higher than when the engine rotation speed increased. In the regression analysis results between the two variables and the hydraulic characteristics of EHPVs, the steering angle demonstrated a higher correlation than the engine rotation speed. In conclusion, the steering angle and engine rotational speed are the major variables in the hydraulic characteristics of EHPVs, and the influence of the steering angle is greater.

Design & Development of Electro Hydraulic Control Valve for Integration of Hoist and Steering System of a Dump Truck (35t)

The intent of this paper is to propose a system to control the steering operation and hoist operation of the Dump truck through combination of electro hydraulic valves and priority valve housed in Integrated manifold block. Electro hydraulic control valve(EHCV), and Electronic controller unit (ECU) for steering and hoist operation of the dump truck. The orbitrol valve consists of load sensing line, when the Orbitrol valve sense an effort on the steering wheel by the operator, the load sensing line will give a feedback signal to the electro hydraulic valve, which will divert the pressurized hydraulic oil to the steering system for steering operation, else the hydraulic oil is available for hoist operation. The hoist operation is control through Electronic Controller Unit (ECU). If there is no signal from the controller for hoist operation the hydraulic oil will flow back to tank. The Electronic controller will energize the combination of solenoid operated valves, depending upon the input received from operator through the momentary switch (Raise Switch, Lower/Float Switch, Hold Switch) mounted inside the cabin, which will allow the flow of pressurized hydraulic oil to the hoist cylinder for body raise and lower operation through electro hydraulic control valve. The electronic controller memorizes the signal from momentary switch and energizes the solenoids as per the logic till the next input signal receive by controller.

Design and Simulation of Electro-hydraulic Control Valve Based on AMESim

In this paper, the electro-hydraulic control valve commonly used in ships is taken as the research object, the working principle of the valve is introduced, the model of the valve is established by AMESim software, the model parameters are set and the simulation analysis is carried out. By changing the relevant parameters of the valve, the response speed of the valve can be improved. The simulation results show that the pressure area of load sensitive cavity and the diameter of damping hole have obvious influence on the response speed of valve.

Modeling, simulation and experimental validation of flow rate of electro-hydraulic hitch control valve of agricultural tractor

Advances in non-linear control theory have made it possible to develop controllers for non-linear dynamic systems in their nature. The low-cost proportional control valves of the hydraulic control system are examples of such a system where there is no linearity due to the structure of the valves and the flaws in the spool. However, the non-linear analysis and regulation of these hydraulic systems cannot be done without a proper valve model. This paper presents a methodology for the development of an efficient unified model of a three-point hitch (TPH) electro-hydraulic proportional control valve control system for agricultural tractors by means of a parameter estimation technique. Modeling and simulation of the proportional control valve was performed using MATLAB Simulink software. Parameter estimation methodology was used to optimize the effective orifice opening of the solenoid valve to meet the flow characteristics available in the manufacturer's technical data sheet for the proportional control valve model parameters. Such unified Simulink models are useful for simulation, practical capability testing, and non-linear control design. Modeling and simulation of electro-hydraulic hitch (EHH) control valve were made and simulation results were compared with actual experimental results. The simulation results of the TPH lifting and lowering time were found to vary 4 and 12.5 %, respectively with the experimental results. This type of parameterized valve models facilitates their implementation in dynamic simulation models of complex hydraulic systems.

Understanding and Measuring the Decomposition Products in Phosphate Ester Fluids Using Linear Sweep Voltammetry (Remaining Useful Life Evaluation Routine)

Abstract Critical applications such as electrohydraulic control (EHC) systems in steam turbines use phosphate ester fluids. EHC valves regulate the flow of steam in a steam turbine and hence maintain the efficiency of the turbine. These fluids undergo degradation during their life cycle, the primary degradation mode being hydrolysis. This article describes the hydrolysis reactions of phosphate ester fluids, hydrolysis byproducts, and the measurement of the species involved (i.e., alkylphenols). Hydrolysis byproducts affect the fluid’s performance, and, hence, their analysis is critical for proper condition monitoring of the phosphate ester fluid. An electroanalytical method, linear sweep voltammetry, is described to measure the alkylphenols generated during the decomposition process. Monitoring the alkylphenols serves as a leading indicator tool for monitoring the hydrolysis extent and as a leading indicator for the varnish potential of the in-service phosphate ester fluid.

Uncertainty Modeling Using a Dimension Search and a Genetic Algorithm With Application to Robust Stability Analysis

This work uses a new method of determining a parameterization, resampling, and dimension search of an uncertainty model that can be used for efficient engineering models in control design. An algorithm using the Cayley–Menger determinant as a measure of the dimension test geometry (volume/area/length) of the parametric data points is presented to search for a reduced number of dimensions that can be used to represent the parameters of a model that captures the uncertainty in a dynamic system (uncertainty model). A genetic algorithm (GA) is utilized to solve the nonconvex problem of finding the coefficients of a parameterization of the uncertainty model. A resampling approach for the uncertainty model is also presented. The methods presented here are demonstrated on an electrohydraulic valve control system problem. This demonstration includes consideration of the dimensional search, data resampling, and parameterizing of an uncertainty class determined from test data for 30 replications of an electrohydraulic flow control valve which were experimentally modeled in the lab. The suggested resampling method and the parameterization of the uncertainty are used to analyze the robust stability of a control system for the class of valves using both frequency domain h-infinity methods and analysis of closed-loop poles for the resampled uncertainty model.

Preliminary results of the study of the effect of a multi-cycle load on the hardness of a high-pressure fuel pipe

Investigation of the effect of internal pressure on the distribution of hardness in the fuel pipe wall was conducted. In the high pressure circuits of Common Rail systems, the fuel pressure is much higher than the pressure level in conventional fuel systems. Thas is why it is of practical interest to change the mechanical properties of the component materials during operation. In the present work, an attempt was made to evaluate the influence of the multi-cycle loading of the fuel pipe with a high internal pressure on the hardness of the material from which the fuel line was made. The loading was carried out under the conditions of a non-motorized test bench with a pressure of diesel fuel of 160 MPa. The test duration was 500 hours. With the selected pump shaft speed and the response frequency of the electrohydraulic control valves this was equivalent to approximately 96x106 cycles. Before and after the tests, hardness measurements were made in the cross section of the fuel lines. The distributions of hardness values are obtained, which testify the existence, under the given loading conditions of a self-hardening process of the material. In the initial state, fuel lines are characterized by a certain anisotropy of hardness and, accordingly, strength characteristics. In this case, the inhomogeneity of the field of values of hardness decreases with decreasing radius of location of the material layer. Dispersion of hardness values takes place both along the axis of the fuel pipe and in the circumferential direction. Loading of fuel pipes of the Common Rail type with pulsating hydraulic pressure leads to a redistribution of the hardness values in the fuel pipe wall. It is found that in the layers of material located closer to the central channel of the fuel pipe, the hardness equalization occurs to a greater extent as it is used, than in layers located far from the central channel. In general, the hardness is increased, which can be interpreted as the hardening of the fuel line during operation.

Energy Saving Potential of the Independent Metering Fluid Power System

Electro-hydraulic proportional control valves are widely applied for motion control in the electro-hydraulic fluid power system. Normally, a sliding spool is used in the proportional control valve to control the flow direction and flow rate passing through the valve, as a result, the meterin and meter-out orifices are mechanically connected . The sliding spool makes the system robust and easy to control, but a number of types of losses have been produced with this kind of valve. Therefore, the conventional electro-hydraulic proportional spool valve control system provides precise motion control, but cannot achieve energy saving performance

Development of an Auxiliary Engagement System for Earth Moving Equipment Hydromechanical Transmission

The scope of this paper is to study the failure of hydro-mechanical transmission in earth moving equipments and introducing an auxiliary system to overcome the transmission disengagement on working sites. The main aim of the auxiliary system is to get the transmission in gear in order to get the machine to move and avoid the crane cost lift the machine for maintenance. A 936F caterpillar wheel loader is used as a case study where mostly for the hydromechanical transmission under study; the speed selector spool is failure in the transmission hydraulic controls causes the loader cannot move. So an auxiliary control module to engaged No.6 clutch has been presented and have first speed forward only to rescue the equipments. In the present work, a mathematical model has been developed to simulate the electrohydraulic control system for an auxiliary control module to engage the first speed. An auxiliary module consists of an electrohydraulic directional control valve that used to engage the first speed by actuated the clutch engagement piston. Experimental setup has been conducted to study the dynamic behavior of auxiliary controller on the engage and disengage of the first speed train. The experimental test rig included an auxiliary pump as well as directional control valve where the transmission input and output speeds are monitored as well as the actuating pressure. The results of both simulation and experimental test shows that the purposed auxiliary system is able to engage the transmission into first gear in case of main system pressure leakage. Mathematical model has been proposed for the electrohydraulic control system that used to be the auxiliary engagement system.

A dead-band model and its online detection for the pilot stage of a two-stage directional flow control valve

The dead-band in the electro-hydraulic proportional control valve is one of the main factors that affect its dynamic performance. Especially in the pilot stages of two-stage directional flow control valves, the insistent dead-band will result in a conservative valve controller design. In this paper, a detailed dead-band model describing the relationship between pilot valve spool and the flow rate of the pilot control valve is proposed. And an improved dead-band description involved with the housing clearance of the valve spool is developed to prove the dead-band uncertainty for a single valve system. Then a simple and effective method is proposed to detect the varying dead-band values in the pilot stage. This method is specially designed with a limited main spool displacement and short time interval so that it can be used for online detection without affecting the hydraulic system where the two-stage valve is involved. With the regular dead-band inverse function, comparative experimental results show that this method is effective to attenuate the large trajectory tracking error caused by the varying dead-band. This dead-band detection also can be applied to other electro-hydraulic proportional valve-controlled position control systems with unknown dead-bands.

Study on Hydraulic System of Test Stand for Subsea Control Module

This paper firstly explained the working principle of Subsea Control Module (SCM) and function and performance of the electro-hydraulic control valves, and then mathematical model of the electro-hydraulic control valve in SCM was analyzed. The test board was designed according to characters of hydraulic system of the test stand. And on the basis of these, an effective testing method of the electro-hydraulic control valve in SCM has been defined. According to the test method of hydraulic system, we built and analyzed a model of the hydraulic test system by using the AMESim software. Based on the analysis results, the judgments whether or not the test stand could meet the requirements is made.

The Electro-Hydraulic Control Directional Valve Based on Magneto-Rheological Fluid

The electro-hydraulic control directional valve based on magneto-rheological fluid using in hydraulic support is proposed. The magneto-rheological fluid represents favorable flow liquid state without external magnetic field, but it can represent mechanics quality of similarity solid in strong magnetic field. The magneto-rheological fluid may become solid within milliseconds under the action of an external magnetic field, which can realize intelligent control of hydraulic system and overcome shortcoming of traditional hydraulic valve. The electro-hydraulic control directional valve uses magneto-rheological fluid as controlling fluid, and adjusts pressure difference of action main control valve between left end and right end though changing excitation coil current of magneto-rheological valve. The electro-hydraulic control directional valve based on magneto-rheological fluid can satisfy the self-feeding hydraulic support using requirements and has low manufacturing cost. The installation and using of the electro-hydraulic control valve is more convenient and fast. It reduces the point of failure of the hydraulic supports piping system and makes hydraulic support more secure and reliable.

Prediction Model of Control Valve Characteristics

Control valves are generally present whenever fluid flow regulation is required. The control valve reliability is critical to the control quality and safety of a plant. An improved dynamic and static valve behaviour would have a major impact on the process output. In order to assess the dynamic performance of the control valve, a computer model of an electro-hydraulic control valve is developed. And the control valve characteristics are investigated through the use of mathematical simulations of the control valve dynamic performance. The results show that the electro-hydraulic driven control valve, which is developed to regulate the mixed-gas pressure in combined cycle power plant, can meet the challenge of the gas turbine.

Design of Hydraulic System of Sway Machine Based on Electro-Hydraulic Proportional Control Technology

According to the problems of hydraulic system of sway machine, such as commissioning and maintenance are inconvenient, impact of change direction is big, system speed is slow, production efficiency is low, etc. It used electro-hydraulic proportional control valve to improve design in hydraulic system of sway machine. Application of electro-hydraulic proportional control valve has realized automatic adjustment of the hydraulic motor speed; it is effective to solve variable speed movement of sway machine frame and no impact of changing direction smooth. Commissioning and maintenance of sway machine are more convenient, and it improves performance of sway machine.

Design and Analysis of a Two-Valve Control Hydraulic System for Controllable Pitch Propeller

This paper designs a two-valve control hydraulic system for controllable pitch propeller which consists of an electro-hydraulic directional control valve and a proportional directional control valve. The parallel control strategy is proposed and respective controllers are determined for the system. It yields out the relationship between the control parameters and valves characteristics by modeling and simulation analysis. Also the influence of the proportional valve flow rate on pitch control accuracy is discussed.

Pressure Pulsation System in Electro-Hydraulic Control Valve of Engineering Mechanical

In order to overcome steady-state error and low-velocity scrawl problems caused by friction in electro-hydraulic control system of engineering mechanical, method for overcoming nonlinear friction force of pressure pulsation system is adopted in this study. A new pressure pulsation system is proposed, mathematical model of the pressure pulsation system is established, based on the MATLAB fuzzy control strategy and simulation. The results show good dynamic performance of the system.

Research on Intelligent Synchronization Control of Erecting System Driven by Two Hydraulic Cylinders

The synchronization control problem of a large equipment erecting system driven by two oil cylinders side-by-side is analyzed. A closed loop control scheme of hydraulically driven erecting system based on electro-hydraulic proportion control valve is given. Considering the existence of time-varying parameters of hydraulic system, intelligent PID control algorithm is implemented by adding neurotic adaptive element control approach to improve the adaptive control capacity of the controller. Simulation results show that the intelligent PID control algorithm is more effective than conventional method for the erecting system synchronization control.

Effect of Internal Leakage on an Electro-Hydraulic Servo-Driven Control Valve Performance

The principle of an electro-hydraulic servo-driven control valve used to regulate mixed-gas pressure in combined cycle power plant is introduced. The mathematic model for describing the dead-band characteristics of the electro-hydraulic servo-driven control valve is built. The effect of driving system leakage of the control valve on the performances of the control valve is analyzed. The results show that the dead band of the electro-hydraulic servo-driven control valve increases with the rise of the system leakage, the leakage affects the response rapidity and the control accuracy of the control valve, and the valve control effect on the pressure pulsation of the mixed gas decreases with the increase of the system leakage.

Magneto-rheological driving based numerical simulation on colliery hydraulic support directional valve

Based on application actuality for colliery hydraulic support directional valve, we put forward a magneto-rheological (MR) driving based directional valve. Firstly, accounting of the MR driving mechanism, the frame model of the electro-hydraulic directional control valve is established based on MR fluid, and the feasibility of this new directional valve is expatiated based on the MR driving. Secondly, a mathematical model of the MR valve is established for the numerical simulation. Finally, the computational fluid dynamics (CFD) technique is adopted for the numerical simulation of the inner flow field of the directional valve to obtain the pressure, velocity, and other parameters. Comparing the new directional valve with the traditional one, it has features of simple structure, less moving parts, fast motion response, and high dependability.

Power Scaling Bond Graph Approach to the Passification of Mechatronic Systems— with Application to Electrohydraulic Valves

In many applications that require physical interaction with humans or other physical environments, passivity is a useful property to have in order to improve safety and ease of use. Many mechatronic applications (e.g., teleoperators, robots that interact with humans) fall into this category. In this paper, we develop an approach to design passifying control laws for mechatronic components from a bond graph perspective. Two new bond graph elements with power scaling properties are first introduced and the passivity properties of bond graphs containing these elements are investigated. These elements are used to better model mechatronic systems that have embedded energy sources. A procedure for passifying mechatronic systems is then developed using the four-way directional electrohydraulic flow control valve as an example. The passified valve is a two-port system that is passive with respect to the scaled power input at the command and hydraulic ports. This is achieved by representing the control valve in a suitable augmented bond graph, and then by replacing the signal bonds with power scaling elements. The procedure generalizes a previous passifying control law resulting in improved performance. Similar procedure can be applied to other mechatronic systems.