# Analysis of the Impact of Vibrations on the Driver of a Motor Vehicle
## 3 Results  
The test run included driving on a motorway, high speed roads, and local roads. During the measurements, phases of vibrations clearly perceptible on the steering wheel were identified with a time stamp. More than 30 such phases were recorded during the test run (Figure 3). The calculated total daily exposure value (Figure 4) of 0.1 m/s\({}^{2}\) is five times lower than the value of 0.5 m/s\({}^{2}\) set as the limit in the applicable standard, which makes it evident that the level of general vibrations affecting the vehicle driver does not exceed the standard threshold. Furthermore, the conclusion derived from the total RMS value of vibration accelerations of 0.27 m/s\({}^{2}\) is that the level of vibrations falls within the range of comfort (limit of 0.36 m/s\({}^{2}\)). The vibration dose value (VDV) (Figure 4) of 3.8 is also three times lower than the permissible limit of 9.1. As reported in several papers, the highest values of the vibration parameters affecting the driver were registered along the vertical \(Z\) axis (RMS values being two to three times higher than those obtained for the X and Y axes). Figure 3: Behavior of the vibrations in time with marked non-standard phases of vibrations clearly perceptible on the steering wheel. Another part of the studies was an FFT frequency analysis and determination of frequency spectra based on the overall behavior of the vibrations recorded in time (Figure 5). The spectral analysis has revealed that the vertical (Z axis) vibrations associated with the setup of the vehicle's sprung and unsprung masses fall within the low frequency range, i.e., that of a few Hz. As for the vibrations recorded in directions X and Y, on the other hand, dominant values were found for the frequency of 28 Hz, which translates into a rotational speed of 1700 rpm, tantamount to the engine's rotational speed at which considerable and perceptible vibrations were also recorded at the steering wheel. With regard to local vibrations, namely the effect exerted by the steering wheel on the driver's hands (Figure 6), the calculated total daily exposure values of 0.35 m/s\({}^{2}\) and 0.39 m/s\({}^{2}\) are also five times lower compared to the standard value of 2.5 m/s\({}^{2}\), which makes it evident that the level of local vibrations affecting the vehicle driver does not exceed the standard threshold. The total RMS value of vibration acceleration is approx. 1 m/s\({}^{2}\), while the RMS values obtained for individual directions also come to approx. 1 m/s\({}^{2}\). The maximum (PEAK) values recorded at the steering wheel are lower than 20 m/s\({}^{2}\), and hence a peak factor value nearing 30 (Figure 7). The forementioned implies the significant dynamic and the considerable contribution of forcing of an impulse response nature. Another part of the studies comprised an FFT frequency analysis and determination of a frequency spectrum based on the overall behavior of the vibrations recorded in time. The spectral analysis revealed that, for the vibrations recorded in directions X, Y, and Z (Figures 8-10), dominant values were found for the frequencies of 13, 36, and 72 Hz, which translates into rotational speeds of 780, 2160, and 4320 rpm. Figure 4: Summary of the global vibration parameter values (driver seat), (*-multiplication). Figure 5: Averaged frequency spectrum of the global vibration (driver seat). Figure 6: Summary of the local vibration parameter values (steering wheel), (*-multiplication). Figure 7: Averaged frequency spectrum of local vibration (steering wheel). (**A**) Background FFT-velocity v = 0, engine working, and (**B**) average FFT-velocity v > 0, engine working. Figure 8: Detailed frequency analysis for the steering wheel vibrations in the direction X.  
Figure 9: Detailed frequency analysis for the steering wheel vibrations the direction Y.  
Frequencies in the range of 8-15 Hz are characteristic for vibrations of unsprung mass elements (wheel with part of the suspension).