Parameter estimation of one wheel vehicle using nonlinear observer

The effective radius of the tire as well as the rolling resistance of a vehicle are two important variables that affect its dynamics, performance and comfort. Because of their dependence on tire pressure, the assessment of these variables can be used to monitor tire pressures using an indirect approach. By considering the vertical, longitudinal and rotational dynamics and using the wheels´ angular velocities and the actuator torque measurements a nonlinear observer is developed from the variable´s estimation. The proposed approach is based on nonlinear observer and does not require additional sensors. This observer is based on a sliding mode approach of high order, characterized by its robustness and convergence in finite time. The peculiarity of the developed approach is the joint estimation of two parameters, which are the effective radius and the rolling resistance. In fact, the observer provides a first solution for the rolling resistance dynamic estimation, in standard driving situations. The obtained Simulation results allow the analysis of the effect of tire pressure on the estimated variables and demonstrate the applicability of the proposed approach.