Wyniki wyszukiwania - Biblioteka Nauki

1

The influence of shock absorber characteristics’ nonlinearities on suspension Frequency Response Function estimation and possibilities of simplified characteristics modelling

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Ślaski G. , Klockiewicz Z.

Archiwum Motoryzacji

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2022

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tom Vol. 96, nr 2

77--95

EN

The paper shortly presents shock absorber design evolution and resulting achieved characteristics. The way in which suspension performance is evaluated is described giving information about models used for suspension parameter tuning during simulation testing of suspension transmissibility (FRF - Frequency Response Function) for most important suspension assessment criteria. More detailed information about models of shock absorber (damper) nonlinearities of characteristics allows for description of methods of linear and nonlinear suspension models FRF estimation. Testing linear suspension model is possible with the use of analytical transfer function formulas which were used to verify methods for estimation FRF using estimated power spectral density functions of excitation and response signals. Designing appropriate input signal allowing to get useful response signals was necessary to for the success of this research. Proposed FRF estimation method was used for linear estimation of nonlinear suspension for a given range of working condition. It was demonstrated that there is no single value of a damping coefficient which would make the linear model responses similar to the responses of the nonlinear one. Then the bilinear model was proposed, giving good damper static nonlinear characteristic.

2

Comparison of vehicle suspension dynamic responses for simplified and advanced adjustable damper models with friction, hysteresis and actuation delay for different comfort-oriented control strategies

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Klockiewicz Z. , Ślaski G.

Acta Mechanica et Automatica

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2023

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tom Vol. 17, no. 1

1--15

EN

Throughout the years, many control strategies for adjustable dampers have been proposed, designed to boost the performance characteristics of a vehicle. Comfort control strategies such as Skyhook (SH), acceleration-driven damping or power-driven damping have been tested many times using simulation models of vehicles. Those tests, however, were carried out using simplified damper models – linear or simple bilinear with symmetric characteristics. This article presents the results of examination of the influence of using more complex damper models, with friction, hysteresis and time delay of state switching implemented, on the chosen dynamic responses of a suspension system for excitations in the typical exploitation frequency range. The results of the test are compared with those found in the literature and with the results of simulations performed with a simplified version of the advanced model used. The main conclusion is that friction and hysteresis add extra force to the already existing damping force, acting like a damping increase for all analysed control strategies. The actuation delays limit the effectiveness in a sense of comfort increasing to only some frequencies. The research shows the importance of including the proposed modules in testing for both adjustable and passive dampers.

3

The influence of friction force and hysteresis on the dynamic responses of passive quarter-car suspension with linear and non-linear damper static characteristics

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Klockiewicz Z. , Ślaski G.

Acta Mechanica et Automatica

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2023

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tom Vol. 17, no. 2

205--218

EN

Vehicle passive suspensions consist of two major elements generating force – spring and passive damper. Both possess non-linear characteristics, which are quite often taken into account in simulations; however, the friction forces inside the hydraulic damper and the damping force’s hysteresis are usually left out. The researchers in this paper present the results of examination of the influence of using complex damper models – with friction and hysteresis; and with linear and non-linear static characteristics – on the chosen dynamic responses of a suspension system for excitations in the typical exploitation frequency range. The results from the simulation tests of the simplified and advanced versions of the damper model – different transfer functions and their relation to the reference model’s transfer functions – are compared. The main conclusion is that friction and hysteresis add extra force to the already existing damping force, acting similar to damping increase for the base static characteristics. But this increase is not linear – it is bigger for smaller frequencies than for higher frequencies. The research shows the importance of including non-linear characteristics and proposed modules in modelling passive dampers.

4

The method of estimating kinematic road excitation with use of real suspension responses and model

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Klockiewicz Z. , Ślaski G.

Vibrations in Physical Systems

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2019

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tom Vol. 30, nr 2

art. no. 2019214

EN

The paper deals with the problem of vertical kinematic excitations in road vehicle dynamics simulation, with the main focus on reconstruction of random excitations using measured dynamic responses of a car suspension. The possibility of causing excitations adequately in terms of chosen conditions of exploitation and in reliable way is crucial to properly asses ride comfort, ride safety as well as rattle space and fatigue strength of suspension elements. The paper presents a method of generating equivalent kinematic excitation allowing for reconstruction of suspension dynamic responses in simulation. The method uses unsprung mass accelerations acquired during test rides and a model of vertical suspension dynamics. The method uses estimated displacements of unsprung mass as a preliminary approximation of kinematic excitation and tracking control system with a PID controller, which causes corrections of kinematic excitations transforming it to the form that allows for faithful reconstruction of unsprung mass accelerations and, in turn, kinematic excitations. The paper presents the basic structure of kinematic excitations’ reconstruction system as well as a method of tuning PID controller’s coefficients so that the error in estimation is minimized. Research and verification of results were done using a sine chirp signal and constant frequency sine waves. The similarity of estimated road profiles is high with error no larger than 8% of the original signal’s amplitude.

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Simulation study of the method of random kinematic road excitation’s reconstruction based on suspension dynamic responses with signal disruptions

80%

Klockiewicz Z. , Ślaski G. , Spadło M.

Vibrations in Physical Systems

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2019

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tom Vol. 30, nr 2

art. no. 2019208

EN

The paper presents the results of simulation studies of the method of random kinematic road excitation’s reconstruction based on the dynamic responses of the suspension acquired in road tests. The method uses registered unsprung mass accelerations as well as model of suspension’s vertical dynamics and tracking control with PID controller to monitor unsprung mass accelerations’ signal in simulation. In the simulation the quality of reconstruction of random irregularities of the road profile was tested. The road profiles were generated based on their power spectral density of road profile heights that is in line with the description given in ISO 8608 standard. Four road classes had their profiles estimations tested – A, B, C and D (corresponding to highways through city roads to the very bad quality roads). The influence of the simulated noise in the suspension’s dynamic response signal – i.e. unsprung mass acceleration – was also tested. The methods of processing of the initial acceleration’s signal from the road tests were proposed and achieved accuracy was defined. Lastly, the necessary requirements to use the method effectively were defined and its limitations were listed.