Abstract
Electric powertrain faults that could occur during normal driving can affect the dynamic behaviour of the vehicle and might result in significant course deviations. The severity depends both on the characteristics of the fault itself as well as on how sensitive the vehicle reacts to this type of fault. In this work, a sensitivity study is conducted on the effects of vehicle design parameters, such as geometries and tyre characteristics, and fault characteristics. The vehicle specifications are based on three different parameter sets representing a small city car, a medium-sized sedan and a large passenger car. The evaluation criteria cover the main motions of the vehicle, i.e. longitudinal velocity difference, lateral offset and side slip angle on the rear axle as indicator of the directional stability. A design of experiments approach is applied and the influence on the course deviation is analysed for each studied parameter separately and for all first order combinations. Vehicle parameters of high sensitivity have been found for each criterion. The mass factor is highly relevant for all three motions, while the additional factors wheel base, track width, yaw inertia and vehicle velocity are mainly influencing the lateral and the yaw motion. Changes in the tyre parameters are in general less significant than the vehicle parameters. Among the tyre parameters, the stiffness factor of the tyres on the rear axle has the major influence resulting in a reduction of the course deviation for a stiffer tyre. The fault amplitude is an important fault parameter, together with the fault starting gradient and number of wheels with fault. In this study, it was found that a larger vehicle representing a SUV is more sensitive to these types of faults. To conclude, the result of an electric powertrain fault can cause significant course deviations for all three vehicle types studied.
KEYWORDS – Vehicle Dynamics; Vehicle Safety; Fault Tolerance; Electric Powertrain; Sensitivity Study