Friction detection from stationary steering manoeuvres

The friction coefficient between the tyres of a vehicle and the roadway is one of the most critical parameters governing a vehicle's motion. However, most techniques for identifying road friction from vehicle motion require the operation of the vehicle in highly dynamic manoeuvres that utilise a significant portion of the tyre grip capacity. Thus, the excitation of dynamics sufficient to provide a reasonable estimate of the friction coefficient could also destabilise the vehicle. This paper presents an alternative approach to friction estimation wherein stationary steering manoeuvres, such as those performed in moments while a vehicle is not moving within a parking lot or at an intersection, may be used to identify the tyre-road friction characteristics prior to higher speed operation. The paper describes a model and results from using a stationary steering process to identify friction. The approach is validated with experimental data from a steer-by-wire test vehicle to illustrate the efficacy of the technique.