Wyniki wyszukiwania - BazTech

1

Rapid design of a hydraulic damper valve system

Wszołek G., Czop P., Skrobol A., Sławik D.

Systems : journal of transdisciplinary systems science

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2012

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Vol. 16, nr 1

45-56

EN

This paper proposes an analytical tool that supports the design process of a disc spring valve system used in hydraulic car dampers. The proposed analytical tool obtains a key design characteristic of a valve, which is the flow rate and the corresponding maximum stress level in the stack of plates. The tool is prepared based on the cases produced by a first-principle model using a finite element approach. The finite element model was calibrated based on experimental results to provide accurate results in the entire range of input parameters.

2

Automatic shape identification by data-driven algorithms with applications to design optimizing in hydraulics

Włodarczyk T. H., Czop P., Sławik D., Wszołek G.

Systems : journal of transdisciplinary systems science

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2012

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Vol. 16, nr 1

35-43

EN

A measurement methodology based on differential-geometric properties of certain characteristic curves frequently used in hydraulics is presented. An iterative process that underlies construction of the methodology and its fully automatic application is universally applicable to identifying, and ultimately optimizing, behavior of any device which can be characterized by a 2D, nonlinear curve. Illustrative examples are used to clarify the topic and its usefulness in optimizing performance of a design with respect to oil aeration effects.

PL

Prezentowany artykuł przedstawia metodę pomiarową stosowalną do automatycznego wyznaczania opisu ilościowego kształtów krzywych charakterystyk typowych dla urządzeń hydraulicznych. Proces iteracyjny dzięki któremu możliwe jest osiągnięcie założonego celu jest uniwersalnie stosowalny do optymalizacji zachowania dowolnego urządzenia posiadającego dwuwymiarową, nieliniową krzywą charakterystyki. Praca niniejsza koncentruje się na ilościowym opisaniu tak zwanego efektu aeracji - niekorzystnego zjawiska obserwowanego w urządzeniach w których olej hydrauliczny pozostaje w bezpośrednim kontakcie z rozpuszczalnym w nim gazem. Iteracyjne, lub adaptacyjne, zastosowanie filtrów wygładzających Savitzky'ego i Golay'a (S-G) leży u podstaw przedstawionej tu metodologii wyznaczania dominującego kształtu zaszumionej funkcji skalarnej jednej zmiennej. Dzięki szczególnym własnościom filtrów S-G możliwe jest dokładne rozpoznanie kształtu danej krzywej nawet w obecności znaczącego szumu. Przykładem takiego szumu są, mające dużą amplitudę, wysokoczęstotliwościowe oscylacje sygnału siły, które obserwujemy w trakcie otwierania się zaworów dyskowych.

3

Fluid-structure simulation of a valve system used in hydraulic dampers

Czop P., Gąsiorek D., Gniłka J., Sławik D., Wszołek G.

Modelowanie Inżynierskie

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2012

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T. 14, nr 45

197--205

EN

The aim of this paper is to develop a method for optimizing the design of a disc spring valve system by reducing the aeration and cavitation effect which negatively influences the performance of a shock absorber. A fluid structure interaction (FSI) model is used in order to modify the geometry of the valve interior and, in turn, to achieve better performance of a shock absorber. The paper analyzes the pressure distribution along theflow paths inside the valve cavity to reduce the risk of aeration and cavitation, while other important engineering aspects are omitted, e.g. durability of disc-spring valve systems as discussed in [1]. A key measure of valve improvement was chosen as deterioration of the damping force level generated by a shock absorber vs. the number of cycles during continuous cycling of the damper . The objectives of this work are as follows: (i) to present a process for reducing the complexity of the geometry of a disc spring valve system in order to perform a combined fluid-structure simulation, (ii) to show keysteps of the simulation process focusing on interactions between fluid and structure domain and to review relevant simulation results, (iii) to describe practical aspects of the simulation process, including basic parameters and boundary conditions related to the applied commercial software, (iv) to make an optimization case study to show the application scope for the simulation methodology proposed in the paper, and to confront the simulation results with experimental investigations.

4

Adjustment method of parameters intended for first-principle models

Czop P., Kost G., Sławik D., Wszołek G., Jakubowski D.

Journal of Achievements in Materials and Manufacturing Engineering

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2012

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Vol. 55, nr 2

446--453

EN

Purpose: This paper demonstrates a process of estimation phenomenological parameters of a first-principle nonlinear model based on the hydraulic damper system. Design/methodology/approach: First-principle (FP) models are formulated using a system of continuous ordinary differential equations capturing usually nonlinear relations among variables of the model. The considering model applies three categories of parameters: geometrical, physical and phenomenological. Geometrical and physical parameters are deduced from construction or operational documentation. The phenomenological parameters are the adjustable ones, which are estimated or adjusted based on their roughly known values, e.g. friction/damping coefficients. Findings: A phenomenological parameter, friction coefficient, was successfully estimated based on the experimental data. The error between the model response and experimental data is not greater than 10%. Research limitations/implications: Adjusting a model to data is, in most cases, a non-convex optimization problem and the criterion function may have several local minima. This is a case when multiple parameters are simultaneously estimated. Practical implications: First-principle models are fundamental tools for understanding, optimizing, designing, and diagnosing technical systems since they are updatable using operational measurements. Originality/value: First-principle models are frequently adjusted by trial-and-error, which can lead to nonoptimal results. In order to avoid deficiencies of the trial-and-error approach, a formalized mathematical method using optimization techniques to minimize the error criterion, and find optimal values of tunable model parameters, was proposed and demonstrated in this work.

5

Six Sigma methodology applied to minimizing damping lag in hydraulic shock absorbers

Czop P., Sławik D., Włodarczyk T. H., Wojtyczka M., Wszołek G.

Journal of Achievements in Materials and Manufacturing Engineering

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2011

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Vol. 49, nr 2

243--250

EN

Purpose: The aim of this paper is to identify the root cause of the temporary decrease of the damping force during the early stage of the compression phase of the stroking cycle, the so called damping lag, to describe measures of the phenomenon and to present methods for optimizing the design towards minimizing this (negative) effect. Design/methodology/approach: Theoretical background is presented in a constructive and computable manner with emphasis on measurement data analysis and MATLAB/Simulink modeling. Six Sigma tools were used to validate the model statistically and, more importantly, to propose a method of data-driven optimization of the design. Findings: Root cause of the occurrence of the damping lag was confirmed during model validation to be caused by oil aeration. The dependence of the damping lag on parameters is nonlinear. Six Sigma methodology proved to be useful in achieving design optimality. Research limitations/implications: Statistical model and conclusions drawn from it are only valid in the interior of the investigated region of the parameter space. Additionally, it might not be possible to find a local minimum of the aeration measure (damping lag) inside the selected region of the parameter space; global minimum located at the boundary might be the only possible solution. Practical implications: Optimal value of parameters is not unique and thus additional sub-criteria (cost/ durability) can be imposed. Conducting tests in an organized manner and according to the Six Sigma methodology allows for expediting the design optimization process and eliminating unnecessary costs. Originality/value: : Improvements in understanding and measuring aeration effects constitute a clear foundation for further product optimization. Signal post-processing algorithms are essential for the statistical analysis and are the original contribution of this work.

6

Formulation and identification of First-Principle Data-Driven models

Czop P., Kost G., Sławik D., Wszołek G.

Journal of Achievements in Materials and Manufacturing Engineering

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2011

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Vol. 44, nr 2

179--186

EN

Purpose The paper consists of two parts. The first part presents and discusses a process of formulation and identification of First-Principle Data-Driven (FPDD) models, while the second part demonstrates numerical examples of identification of FPDD models. Design/methodology/approach: First-Principle (FP) model is formulated using a system of continuous ordinary differential equations capturing usually nonlinear relations among variables of the model. The considering model applies three categories of parameters: geometrical, physical and phenomenological. Geometrical and physical parameters are deduced from construction or operational documentation. The phenomenological parameters are the adjustable ones, which are estimated or adjusted based on their roughly known values, e.g. friction/damping coefficients. Findings A few phenomenological parameters were successfully estimated from numerically generated data. The error between the true and estimated value of the parameter occurred, however its magnitude is low at level below 2%. Research limitations/implications Adjusting a model to data is, in most cases, a non-convex optimization problem and the criterion function may have several local minima. This is a case when multiple parameters are simultaneously estimated. Practical implications: FPDD models are an excellent tool for understanding, optimizing, designing, and diagnosing technical systems since they are updatable using operational measurements. This opens application area, for example, for model-based design and early warning diagnostics. Originality/value: First-Principle (FP) models are frequently adjusted by trial-and-error, which can lead to non-optimal results. In order to avoid deficiencies of the trial-and-error approach, a formalized mathematical method using optimization techniques to minimize the error criterion, and find optimal values of tunable model parameters, was proposed and demonstrated in this work.

7

Demonstration of First-Principle Data-Driven models using numerical case studies

Czop P., Sławik D., Wszołek G.

Journal of Achievements in Materials and Manufacturing Engineering

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2011

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Vol. 45, nr 2

170--177

EN

Purpose: The paper consists of two parts. The first part presents and discusses a process of formulation and identification of First-Principle Data-Driven (FPDD) models, while the second part demonstrates numerical examples of identification of FPDD models. Design/methodology/approach: First-Principle (FP) model is formulated using a system of continuous ordinary differential equations capturing usually nonlinear relations among variables of the model. The considering model applies three categories of parameters: geometrical, physical and phenomenological. Geometrical and physical parameters are deduced from construction or operational documentation. The phenomenological parameters are the adjustable ones, which are estimated or adjusted based on their roughly known values, e.g. friction/damping coefficients. Findings: A few phenomenological parameters were successfully estimated from numerically generated data. The error between the true and estimated value of the parameter occurred, however its magnitude is low at level below 2%. Research limitations/implications: Adjusting a model to data is, in most cases, a non-convex optimization problem and the criterion function may have several local minima. This is a case when multiple parameters are simultaneously estimated. Practical implications: FPDD models are an excellent tool for understanding, optimizing, designing, and diagnosing technical systems since they are updatable using operational measurements. This opens application area, for example, for model-based design and early warning diagnostics. Originality/value: First-Principle (FP) models are frequently adjusted by trial-and-error, which can lead to non-optimal results. In order to avoid deficiencies of the trial-and-error approach, a formalized mathematical method using optimization techniques to minimize the error criterion, and find optimal values of tunable model parameters, was proposed and demonstrated in this work.

8

Optimization of hydraulic dampers with the use of Design For Six Sigma methodology

Sławik D., Czop P., Król A., Wszołek G.

Journal of Achievements in Materials and Manufacturing Engineering

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2010

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Vol. 43, nr 2

676--683

EN

Purpose: The aims of this paper are to identify the root cause of the temporary decrease in the damping force which occurs during the early stage of the stroking cycle’s compression phase, the so-called damping lag, to describe measures of the phenomenon and to present methods for optimizing the design towards minimizing this (negative) effect. Design/methodology/approach: A theoretical background is presented in a constructive and computable manner with emphasis on data-driven modeling. The Design For Six Sigma (DFFS) approach and tools were used to validate the model statistically and, more importantly, to propose a method for data-driven optimization of the design. Findings: The root cause of the damping lag was confirmed during model validation as being a result of oil aeration. DFFS methodology proved to be useful in achieving design optimality. Research limitations/implications: The statistical model and conclusions drawn from it are only valid in the interior of the investigated region of the parameter space. Additionally, it might not be possible to find a local minimum of the aeration measure (damping lag) inside the selected region of the parameter space; a/the (depending on the context) global minimum located at the boundary might be the only possible solution. Practical implications: The optimal value of parameters is not unique and thus additional sub-criteria (cost/durability) can be imposed. Conducting tests in an organized manner and according to the Six Sigma methodology allows the design optimization process to be expedited and unnecessary costs to be eliminated. Originality/value: Improvements in understanding and measuring aeration effects constitute a clear foundation for further product optimization. Signal post-processing algorithms are essential for the statistical analysis and are the original contribution of this work.

9

Application of off-line error correction method software to reproduce random signals on servo-hydraulic testers

Braska D., Czop P., Sławik D., Wszołek G.

Journal of Achievements in Materials and Manufacturing Engineering

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2010

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Vol. 40, nr 1

41-49

EN

Purpose: This paper presents an approach towards improving the test rig performance for road signals used in automotive shock absorber tests. The goal is to develop a method for correction of the test signal profile in the off-line mode. The method is intended to be implemented as a software solution without any changes either in hardware or the settings of the servo-hydraulic tester. Design/methodology/approach: A two-stage validation of the proposed correction method was conducted using a servo-hydraulic test rig and its first-principles model. The model is capable of capturing key dynamical properties over a wide operating range while being only moderately complex. Both simulation and experimental performance results are presented and discussed. Findings: The proposed method, both in the frequency and time domain, improves the tracking of the test signal by 10-20% and allows an accuracy of more than 90% to be gained using the best fit measure in the case of reproduction of white noise signals. Research limitations/implications: It is possible to consider more advanced model-based methods for performing off-line error correction. These methods can be used if an accuracy close to 100% is expected. Practical implications: The result of the investigations is the algorithm implemented in the LabView software to automatically perform the correction of the test signal before the test. Originality/value: The paper proposes a modern approach towards the validation process by applying a simulation environment. This ensures the involvement of arbitrary disturbance models to investigate key parameters of the correction method without expensive and time-consuming experimental validation. The developed model can be extended to a model of a shock absorber to simulate full interaction between the servo-hydraulic test rig and the tested product.

10

Simplified and advanced models of a valve system used in shock absorbers

Czop P., Sławik D., Śliwa P., Wszołek G.

Journal of Achievements in Materials and Manufacturing Engineering

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2009

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Vol. 33, nr 2

173-180

EN

Purpose: The aim of this paper is to develop a model of a valve system applicable for strain and stress prediction. Design/methodology/approach: The analytical and numerical approaches are presented to provide an overview for available methods and prediction accuracy. Findings: An equivalent numerical model of a disc valve system of different complexity was developed and discussed. Research limitations/implications: It is important to provide a model functionality allowing for calculation of disc stacks supported by a coil spring and stack settings having the opening limiter. Disc stack stress and opening characteristics vs. applied pressure may be determined with simplified analytically derived model and full 2D model including almost all significant forces and moments in a stack of circular plates. An advantage of a simplified disc stack model is possibility of its implementation in an environment supporting matrix operations, e.g. Matlab. Practical implications: A valve system has to withstand the cyclic pressure load across the piston. The number of discs, their diameters and thicknesses directly affect durability of a valve system. Damper force and valve durability expressed in life-cycles are the optimization criteria considering during selection and tuning of a valve system. Originality/value: A new valve system was developed in two versions, i.e. simplified and advanced. The model allows durability prediction at the design stage reducing the testing costs of low-performance valve systems.

11

Temperature control strategy for a seal fatigue tester

Czop P., Sławik D., Wszołek G., Związek M.

Journal of Achievements in Materials and Manufacturing Engineering

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2008

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Vol. 29, nr 2

155-158

EN

Purpose: The aim of the paper is optimization of a control strategy used in a seal fatigue tester. Design/methodology/approach: Analytical approach has been applied to get an understanding of a heat exchange process. It is required to optimize the control process algorithm. Findings: The initial control algorithm has been improved regarding numerous tests under different operating conditions. The final version of the control program allows to maintain the temperature according to the on-off strategy minimizing the temperature oscillations and potential overshoots. Research limitations/implications: It should be considered a new control strategy based on PID controller. Practical implications: The major component of the tester is the heat exchanger. It consists of a tube and embedded pipe circuit feeding with the external heating or cooling medium. The tube is a cylindrical housing where the seals are assembled at both sides. Two main pumps circulate the medium at a specified flow rate and pressure. The temperature is maintained to hold it almost constant during heating and cooling phases. Two thermocouples are placed close to the seals, and the one in the middle of the heat exchanger tube. The tester is equipped with a control system consisting of a PLC controller and LabView data acquisition application. It is possible to control the device remotely through LAN/WAN networks. The LabView application communicates with the controller via software with the use of PPI (Point-To-Point Interface) protocol. A new control algorithm has allowed to perform tests according to testing specification without significant overshoots. Originality/value: On-off control algorithm has been proposed for a combined heating-cooling installation rarely using in the industrial solutions.

12

Design and development of seal components fatigue tester

Czop P., Sławik D., Wszołek G., Związek M.

Journal of Achievements in Materials and Manufacturing Engineering

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2008

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Vol. 30, nr 1

67-74

EN

Purpose: The aim of the paper is research and development concerning a fatigue tester of shock absorber seal systems. Design/methodology/approach: Analytical approach has been applied to get an understanding of a heat exchange process. The mathematical model has been formulated and validated based on the available measurements. Numerical simulation has been carried out to illustrate a heat exchange process performance. Findings: It is possible to control a seal temperature and mechanical friction related to the rod movement into the seal at the specified velocity. The model accuracy is sufficient to perform sensitivity analysis and optimize the design. Research limitations/implications: The components of a fatigue tester have to withstand the significant temperature differences in the range ~30;+140*C, e. g. hydraulic hoses, fittings, and pumps. Practical implications: We combine the analytical and experimental approach to provide customized and reliable engineering solution in the area of damper component seal development. A typical seal has a lip-like design protecting the moving parts against the leakage. It can be tested in a shock absorber or externally with use of a customized test rigs. Seal tests inside a shock absorber have numerous disadvantages. A shock absorber temperature rises during longer tests and cooling phase is required. This dramatically increases tests duration performed with the use of an expensive general-purpose hydraulic testing machinery. A compressed air or water jacket is used to accelerate the cooling process. Nevertheless, there are limitations related to the physics behind the cooling process. A seal component fatigue tester allows to perform the seal component tests out of the shock absorber. Originality/value: A new testing method provides possibility to quantify the main contributors of seal usage.

13

Przykład zastosowania analizy wrazliwości w optymalizacji zbioru cech sygnałów

Sławik D.

Pomiary Automatyka Kontrola

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2005

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R. 51, nr 9 bis

29--31

PL

Analiza wrażliwości znajduje zastosowanie w wyborze cech sygnałów zawierających najwięcej istotnych informacji o stanie lub klasie stanu badanego obiektu. Wybierane za jej pomocą cechy mogą służyć do budowy prostszych, sprawniejszych i wydajniejszych systemów diagnostycznych. W ramach badań określono jakość budowanego, na podstawie wybranych cech, modelu diagnostycznego. Zrobiono to dla przypadku, gdy cechy sygnału wybierano w sposób, który mógł wydawać się najbardziej poprawny oraz dla przypadku, gdy w wyborze cech posłużono się analizą wrażliwości. W obu przypadkach do określenia zbioru uczącego i testowego zastosowano metodę leave one aut oraz uwzględniono przypadek, w których zbiór danych testujących był równy zbiorowi danych uczących.

EN

Sensitivity analysis finds practical application in selection of signal features, which contains the most important information about state orstate class of researched object. Selected signal features may be used to design and perform simpler and more efficient diagnostic systems. Quality of built diagnostic model was determined based on chosen features. It was made in the case of signal features choice that seems to be the most correct, and in the case of features choice with application of sensitivity analysis. The "leave one out" method and method in which test set was equal to train set where applied in the both cases.

14

Optymalizacja zbioru cech sygnałów diagnostycznych maszyny wirnikowej

Sławik D.

Diagnostyka

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2005

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Vol. 33

163--167

PL

W referacie opisano wyniki testów modeli diagnostycznych zidentyfikowanych na podstawie wartości cech sygnałów oraz informacji o stanie obiektu. Rozpatrzono dwa przypadki. W pierwszym do celów optymalizacji zbioru cech skorzystano z miar wrażliwości. W drugim przypadku uwzględniano wszystkie cechy sygnałów. Prowadząc badania, do określenia zbioru uczącego oraz testującego, skorzystano z metody leave one out. Zaproponowana w referacie metoda optymalizacji zbioru cech sygnałów znajduje zastosowanie w wyborze cech sygnałów zawierających najwięcej istotnych informacji o stanie lub klasie stanu badanego obiektu. Wybierane za jej pomocą cechy mogą służyć do budowy prostszych, sprawniejszych i wydajniejszych systemów diagnostycznych.

EN

The results of tests of diagnostics models are described in the paper. Those models are identified based on value signal feature and information of object state. Two cases were considered. The measures of sensitivities to optimization of signal features were used in the first case and all the signals features were considered in the second one. The 'leave one out' method was applied to the both cases. Sensitivity analysis can be used in selection of signal features. Such the signal features contain the most important information about state or state class of researched object. Selected signal features may be used to design and perform simpler and more efficient diagnostic systems.

15

Przykład zastosowania analizy wrażliwości w diagnostyce maszyn

Sławik D.

Diagnostyka

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2004

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Vol. 30, T. 2

101--104

PL

Obecnie w systemach nadzoru maszyn często monitorowanych jest wiele cech sygnałów diagnostycznych. Wybierane są one na podstawie wiedzy i intuicji projektanta, a nie w wyniku sformalizowanego procesu optymalizacji. Wiąże się to z tym, iż wybór cech sygnałów jest jednym z najtrudniejszych zadań diagnostyki. Mając na celu automatyzację tego zadania opracowano metodę badania wrażliwości cech sygnałów diagnostycznych. Przedstawiona w referacie metoda pozwala na wybór z dostępnego zbioru cech sygnałów pewnego podzbioru cech, istotnego z punktu widzenia diagnostyki maszyn. Otrzymany podzbiór cech ma zapewnić wysoką jakość rozpoznawania stanu technicznego diagnozowanego obiektu.

EN

Nowadays, features of diagnostic signals are very often determined in maintenance systems. They are not usually chosen as a result of formalized optimization process, but they are based on knowledge and intuition of a designer. It is an effect of a fact that selection of signal features is one of the most difficult tasks of technical diagnostics. A method of sensitivity examination of di-agnostic signal features was developed for the needs of automation of this task. The method de-scribed in the paper makes it possible to select a certain subset of signal features, which are meaningful from the diagnostic point of view. They are selected from a set of signal features. An obtained subset should assure height quality of technical state classification of an examined object.