Within this work, differences and new boundary conditions for electric vehicles have been outpointed. Utilizing the degrees of freedom electro mobility offers to car manufacturers leads to the chosen scenario of a powertrain architecture with single wheel drives at the vehicles' rear axis and a heavy rear axle load. For conventional cars without countermeasures this could mean an unstable driving behavior. Using the possibility a single wheel drive offers to freely distribute wheel torques, so-called torque vectoring, it can be utilized to stabilize the vehicle and improve the response qualities at the same time. Four different feed forward approaches for torque distribution were presented. The results are summarized in a table. Distributing wheel torques according to the wheel loads (FF V1) optimizes the wheel force distribution on wheel level instead of vehicle level, which does not always result in improvements with respect to the desired driving behavior. The effort which has to be made for implementation and especially application are less than for the other controls. While the results for braking while cornering are good, dynamic responsiveness for dynamic driving maneuvers such as step-steer showed no improvements. For steady-state cornering unstable driving behavior with skidding spin-out was examined. The second approach was the use of the transfer function for yaw movement for two different single track models during steady state cornering and solving it for an additional yaw torque (FF V2). The implementation requires little effort and also the application values are feasible. The results show stable vehicle behavior, but the responsiveness and agility (step-steer) was not improved. In order to improve handling characteristics, the transfer function method was extended by the vehicles dynamic behavior (FF V3). As the transient vehicle behavior has to be taken into account, implementation and application needs more attempt. The resulting vehicle response was stable driving behavior with improvement on ride agility. For steady-state cornering, a trade-off between oversteer prevention and loss of maximum achievable lateral dynamics has to be achieved adjusting the underlying linear single track models. Best results were found by the use of the static feed forward structure (FF V2) in combination with two single track models whose yawing movements were compared to compute the needed additional yaw moment for dynamic maneuvers, leading to FF V4. But also, the effort for this approach is most. Via adaption of the underlying single track models the steady-state vehicle behavior can be influenced in any direction. As the step steer maneuver shows, agility and stability can be improved for dynamic driving maneuvers. For braking while cornering, stability can be ensured even when driving close to vehicle dynamics limits. Both yaw rate and side slip angle showed a very smooth course.
Potential of vehicle dynamics via single wheel drive for installation space optimized electric vehicles
2012
24 Seiten, 13 Bilder, 1 Tabelle, 24 Quellen
Aufsatz (Konferenz)
Englisch
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