چكيده به لاتين
In this thesis, with the focus on carrying out high speeds road test (speeds between 100 to 160 km/h), the energy lost in the vehicle at high speeds, chiefly tire rolling resistance, aerodynamic force and internal-resistance forces in the vehicle’s coast down test, have been investigated. In order to carry out this research, high-speed vehicle tests have been accomplished in a well-known standard test area (Barez Tire Complex test field) using ultra-precision measuring devices. By utilizing the dynamic modeling of vehicle movement along with the rolling resistance model, in fourth terms of speed, the results have been analyzed. Using the filtering of acceleration and velocity signals, the noise data has been eliminated from the raw data recorded by the measuring device. In the high speed coast down test and field rolling resistance testing, the rolling resistance model has been expressed as a function of main variables which are vehicle speed and tire pressure, and the effective vehicle mass and drag coefficient has also been calculated using the gradient descent optimization method. The results of the study have been analyzed with focus on the trend of rolling resistance at high speeds as the view of different tire pressures, as well as comparison with the average speeds. The possible factors for such trends have also been discussed. It has been shown that at speeds above 100 km/h in comparasion with low/mid speeds, the increase in rolling resistance at different pressures has been accelerated with steeper slopes. Other achievements of the study has been the sudden reductions in rolling resistance at high speeds (above 130 km/h, depending on the tire pressure). At vehicle high speeds, the rising trend of rolling resistance is stopped, and rolling resistance force has been declining. Finally, by calculating the power dissipative forces, the contribution of each resource to total power dissipation during the above process have been examined, chiefly at high speeds. Investigations have shown that with increasing tire pressure, although the rolling resistance has been reduced, but the percentage of the loss of this force relative to total power dissipation has increased relatively; on the contrary, the aerodynamic resistance force experienced relative degradation.
