Vibration characteristics are one of the most important criteria to assess performances of agricultural tractors. Since vibration excitation primarily arise from short wavelength ground unevenness, tire enveloping behaviour plays significant role in determining effective excitation transmitted to the tractor and human operator. In order to be able to influence tractor vibration behaviour in early stage of computer simulation based development, appropriate tire model is needed that is able to account for this phenomenon, characterized at the same time by high computational speed. In this work, two quasistatic enveloping models of the tractor tire were developed and compared to each other. Main purpose of quasistatic enveloping model is to pass effective excitation to the dynamic model of tire viscoelastic structure. For one of the models, novel approach that makes use of artificial neural network for empirical modelling is introduced. In the second case modelling approach is of physical nature, based on analytical description of the simplified tire structure represented by radially distributed springs. It was concluded that neural network based model fulfils requirements for use in vehicle dynamics simulations, due to high computational speed and satisfactory accuracy. Physically based model, due to low computational speed, is not appropriate for vehicle dynamics but can serve as auxiliary model to obtain broader set of empirical data for neural network model development, hence reducing laboratory work needed.

In order to reduce the greenhouse effect caused by CO2 emissions, a lot of car manufacturers are developing battery electric vehicles (BEVs). Almost all of these vehicles have a traditional powertrain layout with the drive unit located in the car body. However, in recent years, a new technology called in-wheel motors has appeared. It significantly improves handling and manoeuvrability of vehicles but it also presents a challenge for both researchers and manufacturers. Since the motors are fitted into a limited space, they must provide high torque and high efficiency. When a reducer is used, the amount of torque needed is decreased several times, hence the overall dimensions of the motor are reduced. This paper studies a number of issues such as the basic concepts of the in-wheel hub drive systems, traction balance, preliminary gear ratio and possible design solutions for reducers used in in-wheel hub drive units. Characteristics of single-stage planetary and cycloidal reducers are analysed in detail. The results show that planetary reducers have an advantage if a lower gear ratio is needed.

The paper outlines the development and optimization of an aerodynamic device for a semi-trailer truck model to reduce aerodynamic drag force. The optimization procedure involves the selection of a basic aerodynamic device shape, using airfoil profiles, and refining its shape and position through established optimization techniques like Full Factorial Design and Response Surface Method within the Design of Experiments framework. The test subject is a 1:10 scale model of the semi-trailer truck. To validate the results obtained from the Computational Fluid Dynamics (CFD) simulations, experimental measurements of aerodynamic drag forces were performed in a wind tunnel. This combination of simulation and experimental testing ensures the reliability and effectiveness of the optimization process for improving vehicle aerodynamics.

Novel oscillator model is introduced whose kinetic energy is inversely proportional to the generalized coordinate. System is referred to as "Oscillator with Hyperbolically Variable Inertia" (OHVI), since its inertia undergoes hyperbolic growth. Concept of comparison of free OHVI with the behaviour of simple harmonic oscillator (HO) via contraction and deformation of a 3D energy surface is introduced. Analysis of phase orbits and fixed point is performed. Obtaining an exact analytical solution for motion of free OHVI is shown. Main features of the system are demonstrated by numerical experiment performed for kinematically excited OHVI using appropriate mechanism design. It is shown that OHVI has an exact solution in the form of Jacoby elliptic function. Also, phase orbits of OHVI show characteristic oval ("egglike") shape. Motiontime histories and amplitude-frequency (AF) characteristics for forced oscillations were determined. Analysis of solutions for free system indicates possibility of realization of oscillatory system that has very long period i.e. low natural frequency. Comparison of system behaviour with typical nonlinear oscillator with restoring force of hardening type was carried out. Presented analysis shows that such system can be successfully applied for attenuation of low frequency vibrations or their detection.

This paper presents a research on the noise intensity and vibrations in the cabin of a self-propelled machine with high clearance, Hidromatiks S-PST, designed for specific farming operations in crop growing. Noise inside the cabin was measured at operator's head level. In order to determine the intensity of "whole body vibrations" that the operators are exposed to while using the self-propelled machines, the vibrations were measured at the seat of the machine."Hand-arm vibrations" were measured at the steering wheel and control stick of the machine. The measurings were performed during travelling on different surfaces: asphalted road, dirt road, and furrows. The results of measured noise level indicated that the effective values obtained from the cabin of a self-propelled machine travelling over asphalted surface, dirt road and furrows were below the limit values of exposure to noise set by the Rulebook. The results showed that travelling of a self-propelled machine on asphalted road, dirt road and furrows had "whole body vibrations"and "hand-arm vibrations", i.e. Daily values of exposure to vibrations (A(8) (m/s2 )), far below the Daily limit values of exposure, and even below the Daily action values of exposure set by the Rulebook, for both types of vibrations. Such results obtained from measured level of noise and vibrations imply that the operators using self-propelled machinery Hidromatiks S-PT, are not in risk of damaging their health, which damages can be caused by noise and vibrations.