Influence of damping characteristics changes on vehicles vibration research

The vehicle vibration causes many difficulties as: increases fuel consumption, damages to the elements of vehicles and causes vibration to roadside buildings. For driving safety and comfort it is very important what kind and values of vibration transfers from road to car body. A vehicle's vibration should be taken into consideration more often during environmental impact analysis of transport. The article provides a discussion on the studies comprising active experiments conducted on vehicles as the complex oscillatory system, the purpose of which was to analyze the influence of damping characteristics changes on the form of vibration. Damping characteristics of shock absorbers determined values of vibration transfer to car body and pressured forces of wheels and coefficient traction of tires. At the beginning of the investigation the shock absorbers with programmed damping characteristics were prepared. The next step of investigation was encased shock absorbers with programmed damping characteristics in the vehicle and conduct vibration test. The car was set in motion and tested with harmonic forced vibration methods. Consequently the vehicle tested on a vibration exciter can be regarded as a vibrating, non-linear and non-stationary mechanical system. To research a system of this type, the methods of non-stationary randomized signal analysis can be useful. In analysis of non-stationary signals random processes have fundamental meaning, in which interesting random effects can be functions of frequency and time domain. As the analytical experiment, different signal processing methods were used. The presented algorithm was based on application of a time and frequency transformation which enables obtaining the information of the signals carry in two domains simultaneously, namely those of time and frequency. The results provided and discussed evidence the applicability of the methods described in the analysis of the impact on vehicles vibration research of damping characteristics changes.