Assessment of the effect of passenger car wheel unbalance on driving comfort

Abstract

This paper presents the results of experimental investigations of the effects of car wheel unbalance on driving safety and comfort. Basic information about types of wheel unbalance, their causes, and effects are included. The test subject was a BMW 3 Series car with rear-wheel drive. A specific unbalance was introduced on the front steered wheels. The vehicle was driven in a straight line on an asphalt road in good condition at speeds between 70 km/h and 140 km/h. During the test runs, acceleration waveforms were recorded from sensors placed on the lower control arm, driver's seat, and steering wheel. The vibration level of the unbalanced wheel increases with the driving speed and with the increase in unbalance. The highest increase in vibration amplitude occurred on the steering wheel at speeds between 100 km/h and 120 km/h. These vibrations have a direct effect on the driver. This is evidenced by negative driver perceptions such as fatigue and driving discomfort. This was also confirmed by the calculated vibration exposure levels. Driving with unbalanced wheels accelerates wear on the tyres, steering, drive, and suspension components of the vehicle.

Hydraulic Vehicle Damper Controlled by Piezoelectric Valve

“…The analysis of the results shown indicates that the delay in the change of the damping force in the PZD-FT damper resulted from overdriving the valve by a control signal value of 100% (change of the PZ valve supply voltage 0–150 V and 150–0 V) at an average speed of 50 mm/s is about 8–10 ms. Thanks to the use of charge recovery capabilities, the delay time of the control signal value in relation to the value of the piezo-actuator supply voltage, is less than 1 ms. For comparison, similar studies conducted for another type of damper indicated, at a similar speed of piston rod movement, delays of up to 50–67 ms [ 27 ]. The longer delay times were mainly due to the different control principles of magnetorheological damper and the delay times of the action of the winding responsible for generating the magnetic field.…”

“…Driving comfort is defined as a reduction in the intensity of changes in vertical acceleration of a selected point of the vehicle body (e.g., driver or passenger seat points), which is defined in ISO 2631 [ 21 , 22 , 23 , 24 ]. On the other hand, increased driving safety is influenced not only by the reduction in horizontal and lateral accelerations [ 24 ], but also by the change in the value of the forces exerted by the wheels on the road (so-called dynamic wheel load changes) as well as the condition of the tires [ 25 , 26 , 27 , 28 ]. When discussing control algorithms, it should be noted that many dampers using non-Newtonian fluid have inherently nonlinear characteristics; therefore, the selection of an effective control strategy remains a difficult problem to solve and apply [ 29 ].…”