The GPS and Vehicle Dynamics Lab at Auburn University is expanding the boundaries of parameter estimation for lateral vehicle dynamics. A critical part of the lateral vehicle model is the tire/road interaction. To characterize this interaction, sideslip (difference in heading and direction of travel) must be estimated; one method is to combine the Global Positioning System (GPS) with an Internal Measurement Unit (IMU). Figure 1 shows the Infinity G35 the lab uses to perform the experiments. The car is instrumented with multiple GPS receivers, IMUs, and numerous additional sensors.

Although many researchers have estimated tire parameters online using linear tire models (i.e. cornering stiffness), to predict the tire behavior outside the linear region, a more complicated model must be used. This model must capture the linear nature of the tire at small slip angles, but also the saturation behavior at large slip angles (i.e. when the car slides). Being able to estimate this peak force on-line is critical for stability control systems; if it is known when the car will slide, it is possible to remain below that threshold. This estimation could also be useful in autonomous or tele-operated ground vehicles. Knowing the peak lateral force, the steering controller could not allow behavior outside the inherent capability of the UGV.

## Figure 1:Fully Instrumented Infinity G35 | ## Figure 2:On-line Tire Curve Estimation |