New torque vectoring functions for modular electrical propulsion

Abstract

With the increasing electrification of passenger cars, more and more vehicles will be equipped with multiple E-motors. Having 2 motors on one axle offers the opportunity to implement functionality without additional hardware. By applying different torques on the left and right wheel, the vehicle driving direction can be influenced by the resulting yaw moment. The function is known as torque vectoring. Torque vectoring is not new and is also implemented in mechanical systems. The main objective of such systems is to achieve better traction during cornering and to increase the steering response of the vehicle. FEV has investigated additional possibilities for torque vectoring systems based on dual E-motors. These functions focus more on the daily use for typical customers. A simulation model has been built to develop and investigate the new functions. As next step a development platform was used to demonstrate the results on an actual vehicle. In this paper the focus is on the development of the function ``perturbing force compensation''. This function has the aim to support the driver in circumstances where there is a side force on the vehicle that would require the driver to use the steering wheel to keep driving straight ahead. Examples of forces are: side wind and road banking, both situations where the correction is needed for longer periods >1s. The function can also serve as a compensation for E motor tolerances that would give an off-set to the steering wheel effort and angle. The base of the function is an observer that compares the steering wheel angle and torque to the driving direction in relation to vehicle speed. Simulation results show the effectiveness of the function. Finally, the potential risks of torque vectoring have been analysed to secure a functional safety compliant development.