Analytical Method for Defining Pressure Compensator Dynamics

2000 ◽  
Author(s):  
Timo J. Käppi ◽  
Asko U. Ellman
Keyword(s):  
Fluid Power ◽  
Time Domain Simulation ◽  
First Order ◽  
Lack Of Information ◽  
Valve Dynamics ◽  
Accepted Practice ◽  
Component Models ◽  
Hydraulic Valves ◽  
Power Component ◽  
Stationary Behavior

Abstract Computer simulation is a powerful and generally accepted practice to carry out research in the area of fluid power. However, accurate parameterization of the component models is required to achieve correct simulation results. The parameters describing the stationary behavior of hydraulic valves are easily available from valve manufacturers’ catalogues. The dynamics are presented typically for the servo valves only. The dynamics of pressure valves are usually more or less unknown even for the manufacturers. Numerical values for simulation purposes are very rarely available. The lack of information concerning valve dynamics makes the component measurements unavoidable. This is time consuming and costly and the benefits of simulation concept in general are reduced. In this paper a method for defining first order dynamics for the pressure compensator is presented. This method can be used in time-domain simulation of fluid power components and systems. The method is based on the analytical dimensions of valve such as diameter of damping orifice, spring constant and mass. Pressure compensated mobile valve is measured for method verification. The presented method can be applied to any type of commercially available well damped single-stage pressure valves. It makes the fluid power component parameterization considerably easier and thereby the advantages reached by simulation are increased.

A Simple and Robust Sliding Mode Velocity Observer for Moving Coil Actuators in Digital Hydraulic Valves

2016 ◽  
Author(s):  
Christian Noergaard ◽  
Lasse Schmidt ◽  
Michael M. Bech
Keyword(s):  
Binary Operation ◽  
Sliding Mode ◽  
Coil Current ◽  
Estimation Errors ◽  
First Order ◽  
Fast Switching ◽  
Velocity Estimate ◽  
Parameter Values ◽  
Hydraulic Valves ◽  
Position Estimate

This paper focuses on estimating the velocity and position of fast switching digital hydraulic valves actuated by electromagnetic moving coil actuators, based on measurements of the coil current and voltage. The velocity is estimated by a simple first-order sliding mode observer architecture and the position is estimated by integrating the estimated velocity. The binary operation of digi-valves enables limiting and resetting the position estimate since the moving member is switched between the mechanical end-stops of the valve. This enables accurate tracking since drifting effects due to measurement noise and integration of errors in the velocity estimate may be circumvented. The proposed observer architecture is presented along with stability proofs and initial experimental results. To reveal the optimal observer performance, an optimization of the observer parameters is carried out. Subsequently, the found observer parameters are perturbed to assess the robustness of the observer to parameter estimation errors. The proposed observer demonstrates accurate tracking of the valve movement when using experimentally obtained data from a moving coil actuated digi-valve prototype and observer parameters estimates in the vicinity of the optimized parameter values.

scholarly journals Can We Trust Score Plots?

Metabolites ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 278 ◽  
Author(s):  
Marta Bevilacqua ◽  
Rasmus Bro
Keyword(s):  
Discriminant Analysis ◽  
Least Squares ◽  
Partial Least Squares ◽  
Partial Least Squares Regression ◽  
Classification Models ◽  
Least Squares Regression ◽  
Calibration Models ◽  
Accepted Practice ◽  
Component Models

In this paper, we discuss the validity of using score plots of component models such as partial least squares regression, especially when these models are used for building classification models, and models derived from partial least squares regression for discriminant analysis (PLS-DA). Using examples and simulations, it is shown that the currently accepted practice of showing score plots from calibration models may give misleading interpretations. It is suggested and shown that the problem can be solved by replacing the currently used calibrated score plots with cross-validated score plots.

Partitioned Simulation of Fluid Power Systems—an Approach for Reduced Communication between Processors

1996 ◽  
Vol 210 (4) ◽  
pp. 221-230 ◽  
Author(s):  
K Pollmeier ◽  
C R Burrows ◽  
K A Edge
Keyword(s):  
Power Systems ◽  
Fluid Power ◽  
System Model ◽  
Interprocessor Communication ◽  
Time Step ◽  
Transport Delay ◽  
Computational Performance ◽  
Modelling Method ◽  
Fluid Power Systems ◽  
Component Models

Parallel simulation of fluid power systems using the transmission line modelling method offers the benefit of increased speed of execution, but requires the system model to be partitioned on to individual processors. Fluid power systems are characterized by a transport delay in the pipelines connecting physical components, which allows component models to be decoupled; this leads to simulations involving frequent interprocessor communication and low computational performance. This paper describes a method that enables faster simulations by reducing the communication bottleneck. By adjusting the line impedance it is possible to use a larger time step for the communication between processors than the global time step. This approach requires a new filter for the approximation of frequency-dependent friction. Potential gains and the accuracy of the method are estimated. A hydraulic example circuit is partitioned in two subsystems and the new scheme leads to valuable reductions in run time without compromising accuracy.

The Design and Theoretical and Experimental Study of the Plastic Hydraulic Valves

2016 ◽  
Author(s):  
Lubomir Marciniak ◽  
Michał Banaś ◽  
Jarosław Stryczek
Keyword(s):  
Flow Analysis ◽  
Major Elements ◽  
Fluid Power ◽  
Pressure Relief Valve ◽  
Future Research ◽  
Relief Valve ◽  
Pressure Relief ◽  
University Of Technology ◽  
System 1 ◽  
Hydraulic Valves

The overall popularity of plastics has not reached the industrial hydraulics yet. They are already widely used as a material for seals and minor parts, such as handles, covers, caps, etc., but still the dominant material for the making of the key elements is steel. The main project carried out by the Fluid Power Research Group of Wroclaw University of Technology is a fluid power system with the major elements made of plastics. The primary goal is to make a set of prototype plastic elements that within a low pressure range will perform comparably well to the elements which are traditionally made of steel and are available on the market. That set includes two basic hydraulic valves: the pressure relief valve and the on/off valve. The authors present the research that has been done on them so far, as well as evaluate the possible advantages and problems associated with the application of plastics for the making of the system.1 The analysis of the traditional, metal valves’ designs was done as the theoretical base for the plastic valves’ design. All the main parts were studied, especially the main operating elements (poppet and its seat or a piston). In the paper, the references have been provided where possible. All the analyzed features are discussed in terms of using plastics as the main material. In the summary, it is pointed out which of them could easily be transferred, which need to be tested and which are clearly non-transferable and need to be redesigned. Based on guidelines resulting from the analysis of the traditional metal valves, the first plastic prototypes of the pressure relief valve and the on/off valve were designed, constructed and tested by the FPRG. Details of the design are discussed, focusing on its versatility achieved by the usage of interchangeable parts. The early design problems are also shown, as well as the way how they were dealt with. The steady state characteristics are presented and compared to industrial metal valves of the similar size available on the market. A part of the improvement process was an analysis of the flow inside the valve conducted by means of Computational Fluid Dynamics (CFD). The results and conclusions of the flow analysis are presented. The main differences between the plastics and steel are the mechanical properties, especially the lower rigidity. Much larger deformations of the loaded elements can possibly cause problems. Using the CFD results as loads, a structural analysis by means of the Finite Element Method was also carried out. The results and the discussion on whether the deformations are substantial or not and what kind of problems they may cause are presented in the paper. In the summary, the authors draw conclusions from the conducted design process and tests on the first generation prototypes, as well as discuss the reachability of the research objectives defined at its beginning, which regarded the plastic valves. The design of the second generation prototypes is also briefly discussed and the future research plans outlined.

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