Design of Electric Power Steering Control for Compensating the Torque Steer Effect due to Torque Vectoring Control

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Abstract
The increased popularity of electric vehicles featuring distributed powertrains is enabling an easy and cost-effective implementation of torque vectoring. This is a renowned technique for controlling vehicle lateral dynamics having the objective of improving both vehicle handling and stability. Nevertheless, the application of torque vectoring at the front axle can increase the difficulty of usual driving tasks. This is because differential longitudinal forces at front tires generate a steering wheel torque, which can be badly perceived by the driver, up to the point of jeopardizing the benefits of having a torque vectoring control. The aim of this article is thus to study in detail the steering torque corruption caused by front axle torque vectoring for proposing some electric power steering control strategies compensating for this effect. Indeed, the electric power steering controllers developed in this study are designed based on the analytical derivation of the torque steer theory, which comprehensively highlights the contribution of each tire contact action to the steering torque. This innovative approach allows including the effect of front axle yaw moment in the generation of the steering feedback, which is currently neglected in the literature. Driver-in-the-loop simulations at a dynamic driving simulator are adopted for assessing the suitability of the proposed electric power steering control strategies in restoring proper steering feedback when the vehicle is featuring torque vectoring capabilities at the front axle. Moreover, different knowledge levels about the vehicle states are considered in the proposed electric power steering control strategies, proving that the compensation strategy can be effectively deployed even in production vehicles, which require the estimation of some key parameters for the torque steer theory, such as tire contact forces.

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