On the estimation of tyre self-aligning moment through a physical model and the trick tool

The understanding of tyre-road interactions plays a fundamental role in the design of advanced vehicle controllers for enhancing performance and safety. Although there are interesting contributions in the literature that look at estimating tyre-road forces, little has been done on estimating the self-aligning moment. This paper proposes a new method to estimate the self-aligning moment, based on a brush model and a tyre force estimator tool. The idea is that: i) the parameters of a physical model (the brush model) can be optimised to match the lateral forces obtained through a reliable tyre force estimator tool; ii) the optimised model can then be used to compute the self-aligning moment, due to a key feature of the brush model, i.e. that it is a physical model. Hence, unlike other contributions, this method does not require experimental measurements of the self-aligning moment, nor the steering torque. A fitting function is also proposed for the length and width of the contact patch of a tyre as a function of the vertical load. Results show the satisfactory estimation of the lateral force and the consequent self-aligning moment trends, based on experimental manoeuvres carried out on a handling track with a performance-oriented vehicle.