The Modeling of Electrohydraulic Proportional Valves

2011 ◽  
Vol 134 (2) ◽  
Author(s):  
Davide Cristofori ◽  
Andrea Vacca
Keyword(s):  
Steady State ◽  
Linear Model ◽  
Nonlinear Model ◽  
3D Model ◽  
Fluid Dynamic ◽  
Body Motion ◽  
General Nature ◽  
Relief Valve ◽  
Real Component ◽  
Electromagnetic Model

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.

Steady State Characteristics of a Flapper-Nozzle Relief Valve

1987 ◽  
Vol 201 (2) ◽  
pp. 135-144 ◽  
Author(s):  
J S Yun ◽  
H S Cho
Keyword(s):  
Steady State ◽  
Pressure Control ◽  
Effective Area ◽  
Body Motion ◽  
Model Parameters ◽  
Dynamics Model ◽  
Relief Valve ◽  
Load Pressure ◽  
Hydraulic Load ◽  
The Relationship

The static and dynamic characteristics of flapper-nozzle type electromagnetic relief valves have not so far been investigated analytically in depth, although they have been widely used for hydraulic load pressure control. In this paper a non-linear model of the relief valve is formulated explicitly, based upon rigid-body motion and fluid dynamics. Model parameters such as discharge coefficients, effective area of the nozzle and the electromagnetic constant were identified from the steady state characteristics and physical dimensions of the valve. Based upon this constructed model the static characteristics such as the pressure override and the relationship between input current and main pressure were obtained analytically and compared with those obtained experimentally. The comparison shows that this constructed analytical model can precisely predict such characteristics.

Analysis of Single Buffer Random Polling System With State-Dependent Input Process and Server/Station Breakdowns

2018 ◽  
Vol 9 (1) ◽  
pp. 22-50 ◽  
Author(s):  
Thomas Y.S. Lee
Keyword(s):  
Steady State ◽  
Linear Model ◽  
Repair Process ◽  
Polling System ◽  
Steady State Analysis ◽  
Relaxation System ◽  
Polling Model ◽  
State Dependent ◽  
Non Linear ◽  
State Analysis

Models and analytical techniques are developed to evaluate the performance of two variations of single buffers (conventional and buffer relaxation system) multiple queues system. In the conventional system, each queue can have at most one customer at any time and newly arriving customers find the buffer full are lost. In the buffer relaxation system, the queue being served may have two customers, while each of the other queues may have at most one customer. Thomas Y.S. Lee developed a state-dependent non-linear model of uncertainty for analyzing a random polling system with server breakdown/repair, multi-phase service, correlated input processes, and single buffers. The state-dependent non-linear model of uncertainty introduced in this paper allows us to incorporate correlated arrival processes where the customer arrival rate depends on the location of the server and/or the server's mode of operation into the polling model. The author allows the possibility that the server is unreliable. Specifically, when the server visits a queue, Lee assumes that the system is subject to two types of failures: queue-dependent, and general. General failures are observed upon server arrival at a queue. But there are two possibilities that a queue-dependent breakdown (if occurs) can be observed; (i) is observed immediately when it occurs and (ii) is observed only at the end of the current service. In both cases, a repair process is initiated immediately after the queue-dependent breakdown is observed. The author's model allows the possibility of the server breakdowns/repair process to be non-stationary in the number of breakdowns/repairs to reflect that breakdowns/repairs or customer processing may be progressively easier or harder, or that they follow a more general learning curve. Thomas Y.S. Lee will show that his model encompasses a variety of examples. He was able to perform both transient and steady state analysis. The steady state analysis allows us to compute several performance measures including the average customer waiting time, loss probability, throughput and mean cycle time.

QUALITATIVE PROPERTIES OF A POPULATION DYNAMICS SYSTEM DESCRIBING PREGNANCY

2005 ◽  
Vol 15 (04) ◽  
pp. 507-554 ◽  
Author(s):  
G. FRAGNELLI ◽  
P. MARTINEZ ◽  
J. VANCOSTENOBLE
Keyword(s):  
Population Dynamics ◽  
Asymptotic Behavior ◽  
Linear Model ◽  
Nonlinear Model ◽  
Total Population ◽  
Type A ◽  
Qualitative Properties

We study a model of population dynamics describing pregnancy: our model is composed by an equation describing the evolution of the total population, and an equation describing the evolution of pregnant individuals. These equations are of course coupled: one coupling expresses that the total population varies with the number of born people, and another coupling says that the number of fecundated individuals depends on the total population. We study three models of that type: a linear model without diffusion, a nonlinear model without diffusion and a linear model with diffusion. For these three models, we study precisely the qualitative properties and the asymptotic behavior of the solutions.

scholarly journals Efficient Market Hypothesis and the RMB-Dollar Rates: A Nonlinear Modeling of the Exchange Rate

2018 ◽  
Vol 10 (2) ◽  
pp. 150
Author(s):  
Hongxing Yao ◽  
Abdul Rashid Abdul Rahaman
Keyword(s):  
Exchange Rate ◽  
Root Mean Square Error ◽  
Linear Model ◽  
Mean Square Error ◽  
Root Mean Square ◽  
Nonlinear Model ◽  
Efficient Market Hypothesis ◽  
Mean Square ◽  
Forecast Performance ◽  
The Exchange Rate

This paper uses a SETAR model to determine threshold(s) in the RMB/US$ exchange rate from 1981 to 2016 using monthly data. Also, it compares the forecast performance of the univariate nonlinear model to a univariate linear model. We further analyze the forecast performance of the SETAR model to a multivariate linear model, e.g., a Reduced-form VAR. In addition, the research assesses the claim by Boero and Marrocu (2002) that the root mean square error masks the superiority of the nonlinear models.We found five significant thresholds in the RMB/US$ exchange rate, and this result reflects five major episodes of policy reforms or structural changes in the renminbi exchange rates from the period 1981 to 2016. We also found that the univariate nonlinear model out performs both the univariate and multivariate linear models in predicting the exchange rate movements. This finding is consistent with the results in Kyei and Gyamfi (2016), Boero and Marrocu (2002), Krager and Kugler (1993), Peel and Speight (1994) and Chappell et al. (1996). Furthermore, we did not find any evidence of the root mean square error masking the superiority of the nonlinear model.

scholarly journals Comparison of Linear and Nonlinear Behavior of Track Elements in Contact-Impact Models

2018 ◽  
Author(s):  
Jabbar Ali Zakeri ◽  
Mosab Reza Tajalli
Keyword(s):  
Linear Model ◽  
3D Model ◽  
Linear Models ◽  
Wave Length ◽  
Short Wave ◽  
Contact Forces ◽  
Reliable Estimate ◽  
Impact Forces ◽  
Linear Behavior ◽  
Non Linear

Existence of short wave length irregularities and discontinuities in the rail, such as corrugation, isolated rail joints, crossings and rail breakage, result in impact forces and an increase in wheel-rail contact force. Extreme forces in such could result in non-linear behavior of ballast and pads, and as a result, employing common linear models mihgt over/under estimate contact forces. A 3D model of wheel and rail is developed in this paper, and by considering rail breakage, validity of linear models and considering non-linear behavior of materials are studied. Wheel-rail interactions are studied for two common pads with high stiffness (HDPE) and low stiffness (Studded) for speeds of 20 to 160 km/h. Three behavioral patterns are considered for the developed 3D model: linear pad and ballast (LP-LB), nonlinear pad and linear ballast (NLP, LB), and nonlinear pad and ballast (NLP, NLB), and results are compared. According to the results, for HDPE pads and impact forces of up to 30 tons, linear model for material could estimate acceptable results. Yet for studded pads, linear model estimates forces that are comparably less than those estimated by non-linear model. Moreover employing NLP-LB model overestimates pad and wheel-rail contact forces by a rather small margin, compared to those estimated by NLP-NLB model, and hence, could be a suitable replacement for it. It is also observed that in order to have a reliable estimate of ballast forces, using non-linear ballast models are mandatory, and neither LP-LB nor NLP-LB could be acceptable replacements.

scholarly journals Estuarine Exchange Flow Is Related to Mixing through the Salinity Variance Budget

2018 ◽  
Vol 48 (6) ◽  
pp. 1375-1384 ◽  
Author(s):  
Parker MacCready ◽  
W. Rockwell Geyer ◽  
Hans Burchard
Keyword(s):  
Steady State ◽  
3D Model ◽  
Exchange Flow ◽  
Volume Flux ◽  
Estuarine Exchange ◽  
The Relationship ◽  
Total Exchange

AbstractThe relationship between net mixing and the estuarine exchange flow may be quantified using a salinity variance budget. Here “mixing” is defined as the rate of destruction of volume-integrated salinity variance, and the exchange flow is quantified using the total exchange flow. These concepts are explored using an idealized 3D model estuary. It is shown that in steady state (e.g., averaging over the spring–neap cycle) the volume-integrated mixing is approximately given by Mixing ≅ SinSoutQr, where Sin and Sout are the representative salinities of in- and outflowing layers at the mouth and Qr is the river volume flux. This relationship provides an extension of the familiar Knudsen relation, in which the exchange flow is diagnosed based on knowledge of these same three quantities, quantitatively linking mixing to the exchange flow.

scholarly journals Flux Reflection Model of the Ferroresonant Circuit

2009 ◽  
Vol 2009 ◽  
pp. 1-13 ◽  
Author(s):  
Kruno Miličević ◽  
Ivan Flegar ◽  
Denis Pelin
Keyword(s):  
Physical Model ◽  
Linear Model ◽  
Nonlinear Model ◽  
Steady States ◽  
Reflection Model ◽  
Proposed Model ◽  
Simulation Results ◽  
Ferroresonant Circuit ◽  
Nonlinear Coil

The paper presents a linear model of ferroresonant circuit with flux reflection. The proposed model—flux reflection model—derives from observations of typical flux waveforms of nonlinear coil during ferroresonant steady states. Simulation results of the flux reflection model are compared with simulation results of the usual nonlinear model as well as with measurements carried out on the physical model of the ferroresonant circuit. The flux reflection model enables a novel comprehension of the ferroresonant circuit behavior and simplifies the modeling of the nonlinear coil in the ferroresonant circuit.

Steady-State Theoretical Model of an Electro-Hydraulic Single-Disk Pilot Valve

1992 ◽  
Vol 114 (2) ◽  
pp. 293-298 ◽  
Author(s):  
Y. Sun ◽  
G. A. Parker
Keyword(s):  
Steady State ◽  
Theoretical Model ◽  
Experimental Verification ◽  
Control Device ◽  
Null Condition ◽  
Electromagnetic Model ◽  
Disk Valve ◽  
Single Disk ◽  
Electromagnetic Characteristics ◽  
Pilot Valve

The paper describes an electro-hydraulic single floating-disk valve suitable for use as a pilot control device. For this type of application proportional action involving small movements of the disk for the null condition is required. The theory for the steady-state linearized analysis of both the fluid and electromagnetic characteristics is developed. Experimental verification of the electromagnetic model is also described.

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