Determination of tire dynamic properties: Application to an agricultural vehicle

This paper describes the methods for estimating a vehicle's dynamic parameters using a Global Positioning System implementing a Real Time Kinematic scheme (RTK-GPS) and an Inertial Measurement Unit (IMU). An RTK-GPS system and an IMU are used to estimate the vehicle's body sideslip angle and then obtain the relation between the tire's lateral forces and slip angles, and also the tire's cornering stiffness. In order to compare the experimental results two vehicle models are described; the bicycle geometric model and the bicycle dynamic model. The method of least squares was applied to the experimental data in order to obtain mathematical expressions that account for the nonlinearities of the system. It is shown that the measurements performed can be used to estimate the tire sideslip and the tire cornering stiffness. The experimental results are consistent to the predictions made by the models, which verifies the potential of this method to determine a nonlinear mathematical model.