Contribution to the research of oscillatory loads of sprung and unsprung masses in order to create conditions for laboratory tests of heavy motor vehicles

Introduction/purpose: Motor vehicles are complex dynamic systems due to spatial displacements, changes in the characteristics of components during their lifetime, a large number of influences and disturbances, the appearance of backlash, friction, hysteresis, etc. The aforementioned dynamic phenomena, especially vibrations, cause driver and passenger fatigue, reduce the lifetime of the vehicle and its systems, etc. Methods: In general, the movement of vehicles is carried out on uneven roads and curvilinear paths in the road. Not only do oscillatory movements cause material fatigue of vehicle parts, but they also have a negative effect on people's health. That is why special attention must be paid to the coordination of the mutual movement of the subsystems, and in particular, the vehicle suspension system, even at the stage of the motor vehicle design. For these purposes, theoretical, experimental or combined methods can be used. Therefore, it is very useful to have the experimental results of the oscillations of the vehicle subsystem in operating conditions, so the aim of this work was to use the movement of the 4x4 drive FAP 1118 vehicle in operating conditions (due to higher speeds - in road conditions) to define the conditions for testing oscillatory loads in laboratory conditions. Results:This is made possible by registering and identifying statistical parameters of registered quantities. Conclusion: Based on the measured data, the research can be programmed on shakers in laboratory conditions, and, at the same time, the size to be reproduced can be chosen as well

Observation of optical feedback dynamics in single-mode terahertz quantum cascade lasers: Transient instabilities

We provide an experimental evidence of transient instabilities (TIs) in a terahertz (THz) quantum cascade laser (QCL) under optical feedback, in contrast to the widely accepted claim that THz QCLs are ultrastable against feedback. The TIs appear as periodic oscillations in emitted power or terminal voltage of the laser with an increasing oscillation frequency as feedback increases. The absence of relaxation oscillations and low linewidth enhancement factor in THz QCLs makes them a platform uniquely suitable for exploring external-cavity-related dynamics in semiconductor lasers. This work opens a pathway to a THz sensing and imaging modality based on these TIs, which has much reduced complexity compared to existing approaches using laser feedback interferometry

Numerical simulation of thermal loads of the truck’s power train mounting system due to vibrations

© The Author(s) 2018. Dynamic simulation based on modelling has a significant role during a vehicle development process. It is especially important in the first design stages, when relevant parameters are to be defined. Power train mounting system is exposed to thermal loads which can lead to damage and degradation of its characteristics. Therefore, this paper aims to analyse conversion of mechanical work into heat energy in power train mounting system using a method of dynamic simulation. Considering the presence of classic–mechanical and hydraulic power train mounting systems in modern trucks, analysis of power train mounting thermal loads of FAP 1213 vehicle was conducted. Thermal loads of vehicle power train mounts were calculated by dynamic simulation, while their cooling process was not analysed

Prilog istraživanju sila prigušenja u klasičnim amortizerima - A CONTRIBUTION TO INVESTIGATION OF THE DAMPING FORCES IN CLASSICAL SHOCK ABSORBERS

Shock absorbers are fundamental part of the vehicle suspension. Suspensions are needed to guarantee vehicle handling, passenger riding comfort and braking. Bearing that in mind, the tire-road contact forces need to be as stable as possible. Each wheel should always remain in contact with the ground. Comfort means that vibrations, induced by road profile during riding, are of a minimal nuisance to the passengers. When designing a new vehicle, a lot of development effort is focused on the optimal choice of the suspension parameters, stiffness (including stabilisers) and damping. In this paper will be presented the results of influence of the cinematic parameters (relative: displacement, velocity and acceleration) to the force that occurs in the shock absorber. The experimental results are obtained by testing of three types of classic shock absorbers from the production of Magneti-Marelli - Turin, under the influence of random excitation. To determine the level of influence of individual cinematic parameters, the theory of the partial coherence functions was used

Doprinos modeliranju pneumatskog poluaktivnog upravljanja sistema oslanjanja vozila / Contribution to the modeling of a pneumatic semi-active control of vehicle suspension / Вклад в моделирование устройства управления пневматической полуактивной подвеской транспортного средства

This paper contributes to the modeling of a semi-active control of a quarter vehicle model using air springs. A conventional mass-spring-damper model has been used along with an air spring. Based on the theory of thermodynamics, the dynamic equation of the air springmodelwas established. The simulation model was implemented using MATLAB and the transfer functions with varying parameters were calculated. The simulation results show that air spring pressure, the valve diameter, the dumping coefficient and the mechanical stiffness affect the dynamic response of the system. A semi-active control methodology was then established by controlling the valve diameter using two declinations of an on-off logic switch based on the velocity of the suspended mass and the relative velocity at both ends of the air spring. The obtained results show reduced oscillation amplitudes around the natural frequency of the system. / В статье описано моделирование системы полуактивной пневматической подвески транспортного средства с применением четвертноймодели автомобиля. Рассматривалась подвеска традиционного типа (подрессоренная масса – масса- пружина-амортизатор) с применением пневматической пружины. Динамические уравнения пневматического упругого элемента выведены на основе законов термодинамики.Имитационная модель была разработана при использовании программного обеспечения MATLAB. В моделиприведены передаточные функции вертикального смещения подрессоренных масс с переменными параметрами. Результаты моделирования показывают, что на динамические характеристики системы влияют следующие факторы: давление в пневмокамере, диаметр клапана, коэффициент затухания и механическая жесткость пружины. Метод управления системой полуактивной подвески заключается в переменном диаметре клапана с использованием двухпозиционного переключателя, с учетом скорости смешения подрессоренных масс иотносительной скорости края пневмокамеры. Полученные результаты показывают, что примененные способ управления и конфигурация подвески обеспечивают снижение амплитуды колебаний подвески и равновесное положение системы. / U radu je prikazano modeliranje poluaktivnog pneumatskog sistema elastičnog oslanjanja korišćenjem četvrtinskog modela vozila. Korišćen je konvencionalni model oslanjanja (ovešena masa – masaopruga-amortizer), u kombinaciji sa vazdušnom oprugom. Dinamičke jednačine pneumatskog elastičnog elementa izvedene su na osnovu zakona termodinamike. Simulacioni model razvijen je korišćenjem programskog paketa MATLAB. U modelu su date prenosne funkcije vertikalnih pomeranja ovešene mase sa promenlјivim parametrima. Rezultati simulacije pokazuju da na dinamičko ponašanje sistema utiču pritisak u vazdušnom jastuku, prečnik ventila, koeficijent prigušenja i mehanička krutost opruge. Metodologija poluaktivnog upravlјanja sistemom oslanjanja zasniva se na kontroli prečnika ventila korišćenjem dva stanja jednog on-off prekidača, na osnovu brzine kretanja ovešene mase i relativne brzine krajeva vazdušnog jastuka. Dobijeni rezultati pokazuju da usvojeni način upravlјanja i konfiguracija sistema oslanjanja obezbeđuje smanjenje amplitude oscilacija oko ravnotežnog položaja sistema

A Contribution to Optimizing the Power Train Suspension

Contemporary passengers motor vehicles have to achieve a great deal of comfort requirements. Problems of noise and vibration reduction in vehicles may be solved by choice of optimal power train (PT) suspension. In this paper an analytical method is developed. Also, a global model of both vehicle and PT is developed and analyzed. Experimental investigations (laboratory and in field conditions) were done to verify the model. The adopted model was initially used to form the optimization method. Modified Hooke Jeeves method of optimization was combined with results obtained in the experimental research and modeling to form the optimization method. Obtained results from the optimization were a base for PT reconstruction of the analyzed vehicle.https://journals.sagepub.com/doi/10.1177/026309239801700402Publishe