Wyniki wyszukiwania - BazTech

1

Analysis and control of nonlinear vibration of autonomous vehicle passing through hybrid consecutive speed control humps

Yang Zhiyong, Wang Long, Yu Yanjun, Mou Zhenping, Ou Minghui

Bulletin of the Polish Academy of Sciences. Technical Sciences

|

2022

|

Vol. 70, nr 6

art. no. e143643

EN

In order to improve the safety and comfort of autonomous vehicles passing through the expressway, relevant departments of expressway construction often design and lay consecutive speed control humps (SCHs) with cross-sections of different shapes according to different road conditions, such as the combination of trapezoidal and sinusoidal SCHs. In this paper, we conduct a study about the nonlinear dynamic characteristics of the autonomous vehicle passing through hybrid SCHs. Firstly, a four-degree-of-freedom (4-DOF) nonlinear model of the vehicle suspension and the speed coupling excitation model under hybrid SCHs are established. Then the fourth-fifth order Runge–Kutta method is used to simulate the nonlinear system, and its nonlinear dynamic characteristics are analyzed. The results show that chaotic motion occurs when the vehicle passes through hybrid SCHs, and the speed range of chaotic motion is obtained. Then, a direct variable feedback control method is used to suppress the chaotic vibration of semi-active suspension vehicles, and the effect is verified by simulation experiments. Finally, this paper presents a multi-objective optimization model based on a genetic algorithm (GA) for active suspension vehicles. The optimization model selects the vertical displacement and pitching angle of the vehicle body as the objective function. The research results of this paper can provide information on the ride comfort’s optimization for autonomous vehicles passing through hybrid SCHs and on the design of vehicle suspension system.

2

Frequency of free vibration in systems with power-law restoring force

Grega Ivan, Grega Robert, Homisin Jaroslav

Bulletin of the Polish Academy of Sciences. Technical Sciences

|

2021

|

Vol. 69, nr 2

art. no. e136723

EN

To model the nonlinear behaviour of vibrating systems, Taylor expansion with integer powers is often used. Some systems, however, are inherently nonlinear. In the case of a non-integer real exponent, the power-law system cannot be linearised around the equilibrium position using Taylor expansion. The approach presented here provides a simple estimate of the principal frequency of free vibration in systems with power-law restoring force. Without seeking the precise mathematical form of the output waveform, we only focus on the principal frequency. The first step is the use of dimensional analysis to reduce the number of parameters. Two independent non-dimensional groups are formed and functional dependence between them is sought using numerical simulations. Once this dependence is known, the principal frequency of free vibration can be readily determined for any system properties and any initial conditions. Finally, we compare the numerical results to analytical expressions for a few restoring force exponents.

3

Numerical studies of nonlinear gearing models using bond graph method

Margielewicz J., Wojnarowski J., Zawiślak S.

International Journal of Applied Mechanics and Engineering

|

2018

|

Vol. 23, no. 4

885--896

EN

The present paper is dedicated to computer simulations performed using a numerical model of a one-stage gear. The motion equations were derived utilizing the bond graph method. The formulated model takes into consideration the variable stiffness of toothings as well as an inter-tooth clearance which has been represented via discontinuous elements with so called dead zones. As a result of these assumptions, the nonlinear model was obtained which enables representation of the dynamic phenomena of the considered gear. In the paper, an influence of errors of gear wheels’ co-operation on the character of excited dynamic phenomena was studied. The methodology of the analyses consists in utilization of the following tools: color maps of distribution of the maximal Lapunov coefficient and bifurcation diagrams. Based upon them, the parameters were determined, for which the Poincare portrait represents a structure of the chaotic attractor. For the identified attractors, the initial attractors were calculated numerically - which along with the changes of the control parameters are subjected to multiplication, stretching or rotation.

4

Free and forced large amplitude vibrations of periodically inhomogeneous slender beams

Domagalski Ł.

Archives of Civil and Mechanical Engineering

|

2018

|

Vol. 18, no. 4

1506--1519

EN

Considered are free and forced transverse vibrations of slender periodic beams of finite length. It is assumed that the vibration amplitude is of the order of cross-section dimensions, still much smaller than the beam length. An averaged non-asymptotic model is proposed as a tool in analysis. The description is based on the tolerance approach to averaging of differential operators, using the concept of weakly slowly-varying function. The resulting differential equations with constant coefficients involve the effect of periodicity cell length. The model is verified by comparison of linear frequencies and mode shapes with Finite Element Method results, and then applied in analysis of free and forced vibrations of beam with variable cross-section. The method employed in obtaining the solution involves Galerkin orthogonalization and Runge–Kutta (RKF45) method. The results of nonlinear vibrations analysis are presented by backbone and amplitude-frequency response curves, time series, Poincare sections and bifurcation diagrams.

5

Dynamic response of rectangular prestressed membrane subjected to uniform impact load

Li D., Zheng Z. L., Liu C. Y., Zhang G. X., Lian Y. S., Tian Y., Xiao Y., Xie X. M.

Archives of Civil and Mechanical Engineering

|

2017

|

Vol. 17, no. 3

586--598

EN

This paper investigated the dynamic response of rectangular prestressed membrane subjected to uniform impact load theoretically and experimentally. The dynamic response proceeds in two stages, namely, forced vibration and free vibration. Firstly, the maximal displacement for forced vibration is obtained by means of the principle of minimum potential energy based on the theoretical model proposed. Then, equations of motion for the transverse free vibration are derived based on thin-plate theory, and simplified by using Galerkin method. Consequently, the analytic solutions of dynamic parameters, such as frequency, displacement, amplitude, velocity, and acceleration, for free vibration are obtained by means of the multiple-scale perturbation method. In order to identify the reliability of theoretical model, the corresponding experimental study is carried out based on the developed experimental system. Furthermore, the effects of pretension force and load on the dynamic response of membrane are discussed, respectively. The present work provides a theoretical model to calculate the dynamic response of prestressed membrane subjected to uniform impact load, and a set of experimental system to study this problem.

6

Quantitative estimation of the tool wear effects in a ripping head by recurrence plots

Litak G., Gajewski J., Syta A., Jonak J.

Journal of Theoretical and Applied Mechanics

|

2008

|

Vol. 46 nr 3

521-530

EN

We investigate the time series of a torque applied to the ripping head in the process of a cutting concrete rock with sharp and blunt tools. By applying nonlinear embedding methods and the recurrence plots technique to the corresponding time series, we indicate the changes in nonlinear dynamics lying behind the ripping process, and we propose a test of the ripping machine efficiency and a way of monitoring the state of tools.

PL

W artykule przedstawiono wyniki badań nad zastosowaniem nieliniowych metod zanurzenia oraz wykresów rekurencyjnych do oceny zmian dynamicznych zachodzących w procesie urabiania. Przebadano przebiegi czasowe momentu urabiania głowicą uzbrojoną w ostre oraz stępione narzędzia górnicze. Proponowane metody mogą okazać się przydatne w kontekście oceny wydajności oraz monitorowania stanu narzędzi głowicy urabiającej.