Electro-hydraulic Control Valve Research Articles

EFFECTS OF MULTI-MODE FOUR-WHEEL STEERING ON SPRAYER MACHINE PERFORMANCE

A self-propelled agricultural sprayer with four-wheel steering (4WS) was developed. A digital controller was designed and built to control the rear steering angle based on that of the front wheels through electrohydraulic control valves. Three modes of steering were enabled and investigated. Experimental methods were developed to determine what potential 4WS has in improving machine performance. In particular, machine performance of the sprayer was evaluated by measuring turning radius and performance metrics in headland turning and lateral path shift procedures. Coordinated 4WS resulted in smaller turning radii than conventional two-wheel steering (2WS). In the headland turning tests, significant mean increases in aligning distance of 5.58 m and significant mean decreases in rear wheel off-tracking area of 9.3 m2 were observed in 4WS over 2WS. In lateral path correction tests, crab 4WS substantially decreased the area and magnitude of estimated application errors over conventional 2WS, while coordinated 4WS resulted in increased application errors. These results provide evidence that 4WS could enable improvement in sprayer machine performance.

MULTI–FUNCTION REALIZATION USING AN INTEGRATED PROGRAMMABLE E/H CONTROL VALVE

This article reports the development of an integrated programmable electrohydraulic (E/H) control valve. Thisvalve consists of five individually controlled spooltype twoway cartridge subvalves and exchangeable control softwarefor controlling those subvalves. This programmable E/H control valve is capable of changing valve characteristics andoperation functions by changing control logics. Laboratory experimental results validated that this integrated programmableE/H control valve could realize different center characteristics, such as opencenter, closedcenter, tandemcenter, andfloatcenter. It could also realize a flow regeneration function by simply switching appropriate control logics in the softwarewithout modifying the hardware. With appropriate control algorithms, this integrated valve will be able to replace theconventional proportional E/H control valves in many hydraulic systems.

반능동 현가시스템용 자기동조 게인조절형 스카이훅 제어기의 구현 및 실험

In this paper, a self-tuning gain-scheduled skyhook control for semi-active suspension systems is investigated. The dynamic characteristics of a continuously variable damper including electro-hydraulic pressure control valves is analyzed. A 2-d.o.f. time-varying quarter-car model that permits variations in sprung mass and suspension spring coefficient is considered. The self-tuning skyhook control algorithm proposed in this paper requires only the measurement of body acceleration. The absolute velocity of the sprung mass and the relative velocity of the suspension deflection are estimated by using integral filters. The skyhook gains are gain-scheduled in such a way that the body acceleration and the dynamic tire force are optimized. An ECU prototype is discussed. Experimental results using a 1/4-ear simulator are discussed. Also, a suspension ECU prototype targeting real implementation is provided.

Realization of Programmable Control using a Set of Individually Controlled Electrohydraulic Valves

AbstractThis paper reports a study of electrohydraulic valve function programmability and characteristic interchangeability using a set of individually controlled cartridge type electrohydraulic (E/H) control valves. Such an integrated individually controllable E/H valve is defined as the programmable E/H control valve. A hybrid control algorithm was developed to realize different valve functions via programmable logic and to realize different interchangeable valve characteristics via a programmable valve modulation function. Evaluation test results verified that the programmable E/H control valve was capable of replacing different types of conventional proportional control valves and, more importantly, capable of realizing the flow regeneration function. The programmability of the programmable E/H control valve provides the flexibility of using the same firmware of an E/H control valve on various applications by simply downloading different control software.

Technical Status of Pressure, Flow, and Electrohydraulic Control Valves in Hydraulic Systems

Technical Status of Pressure, Flow, and Electrohydraulic Control Valves in Hydraulic Systems

Squeeze-Film Damping of the Motion of a Control Flapper-Nozzle

A squeeze film used in a flapper-nozzle affords stand-alone properties to the flapper motion, meaning that it behaves in a dynamically stable manner. The device constitutes the first stage of a new family of two-stage electrohydraulic control valves. Successful mathematical modelling of it has been reported by Lin and Akers (1,2). Because of the expense of maintaining close manufacturing tolerances within the damper, the investigation included the extent of deterioration of dynamic response when the dimensions of the damper are varied, when the tolerances on the squeeze-film annular area are relaxed and when the annular clearance is increased. As a result of the investigation, the dimensions and other variables, chosen by trial-and-error procedures, appeared to be optimum from the point of view of dynamic performance, convenience of installation and cost.

Algorithm modeling the operation of an automatic alignment system for coal-cutting equipment

Automatic alignment systems (AAS) are a very promising class of devices for keeping coal-cutting equipment on a straight line. Experience in the design of AAS and preliminary tests have revealed that the choice of fundamental parameters for the system--such as the zone of permissible curves and the spacing of linearity-monitoring transducers and electrohydraulic control valves--depends largely on the construction of the coal-cutting machine itself. But the influence of these parameters on the effectiveness of AAS has not been studied. As the construction of such systems, together with the coal-cutting machines, and their testing are very time-consuming and expensive, it is important to find methods of studying AAS which can be used as the design stage. Using the fundamental principles of statistical investigation of automatic alignment systems for the bases of coal-cutting machines, with the use of the techniques used in research on the movement of the bases in the plane of the seam, we have devised an algorithm for computer simulation of the operation of an AAS.

Effects of control valve nonlinearity on the output of hydro-acoustic transducers

An underwater sound source using a hydraulic-drive mechanism is subject to signal distortion produced by the electrohydraulic control valve. The nonlinear characteristics of the commonly used valves are described reasonably accurately by a well-known equation derived from Bernoulli's law. A numerical study was made of the effects of the valve nonlinearity on transducer performance, using the Runge-Kutta-Gill algorithm to solve the nonlinear differential equations. Load lines and waveforms were plotted and Fourier distortion components computed for typical operating conditions. The results show that the limitations necessary on the pressure modulation coefficient for low output distortion and show the benefits of resonance in providing a favorable load line, thus confirming and quantifying the design principles used by those who developed the hydroacoustic transducer art.

In technical perspective

The high capacity and fast response of Moog electrohydraulic flow control valves has allowed a difficult test specification to be met at low cost. The two Moog Series 60 valves are fitted to a hydraulic test rig in British Airways' engineering centre at Heathrow Airport, London.

The Modelling of Electrohydraulic Control Valves and its Influence on the Design of Electrohydraulic Drives

The modelling of the control valve is shown to be a factor of prime importance in the design of electrohydraulic systems. The process required to model a commercially available valve is described in detail, with equal attention to the production of the experimental data and the identification of the model parameters. The quality of the decisions made in the construction of a model is shown to be most critically evaluated when derivative feedback loops are employed. A study of a system with negative transient acceleration feedback is included to illustrate the effectiveness of a third-order model. It is demonstrated that the use of a digital computer is essential for this type of system design.

Application of Volterra series analysis to an electrohydraulic control valve

Application of Volterra series analysis to an electrohydraulic control valve

A describing function for the multiple nonlinearities present in 2-stage electrohydraulic control valves

AN EARLIER PAPER1 introduced a method for handling multiple nonlinearities through describing functions, and developed such describing functions for single-stage electrohydraulic control valves. This work is extended in this paper to 2-stage valves of the type shown in Fig. 1. Most of the essential nonlinearities are included in the describing function which is brought to a form similar to that for the single-stage valve.1 Precalculated charts are utilized which help to make reasonable the amount of labor of computing the describing function for a specific valve. An example in the paper illustrates the use of the describing function, and very good agreement with analog computer studies is demonstrated.

Generalized charts of the effects of nonlinearities in 2-stage electrohydraulic control valves

Generalized charts of the effects of nonlinearities in 2-stage electrohydraulic control valves

A describing function for multiple nonlinearities present in electrohydraulic control valves

A SPECIFIC and a general objective are jointly pursued by this paper. The specific aim is the development of a describing function1 to represent the principal nonlinearities occurring in single-stage 4-port electrohydraulic control valves of the type sketched in Fig. 1. For maximum usefulness of the describing function towards this specific objective, it is expressed in a generalized and dimensionless form. Consequently it is applicable to the analysis or design of electrohydraulic control valves for any individual application. Precalculated curves reduce to very reasonable amounts the labor of computing the describing function for a given valve.

Generalized charts of the effects of nonlinearities in electrohydraulic control valves

THIS paper, which is an extension of previous work,1,2 presents a collection of charts derived from full instrumentation on an analog computer of the equations of a closed-loop control system controlled by a 2-stage electrohydraulic control valve of the type shown in Fig. 1. The curves included in this paper show variations in the performance of the control system under the effect of variations of the individual linear and nonlinear parameters of the valve itself and of the other parts of the control system. Usually just one parameter was varied at a time while the other linear and nonlinear components had a constant, nominal value. In some cases, however, as many as three parameters were varied simultaneously. The resulting curves are presented in a general normalized way which permits the use of these results in drawing conclusions on valves of different physical dimensions. As a whole these results are believed to promote a better understanding of the performance of valves of this type. The results listed have also been used to test the accuracy of theoretical investigations.3