Design of a NonLinear Observer for a Laboratory Antilock Braking System

Abstract

In this paper a nonlinear observer is presented in order to estimate the angular velocity of both upper and lower wheels of the PC controlled ABS Laboratory setup, from INTECO Ltd. The system simulates the dynamics of a quarter car model. In order to accomplis this, it includes two attached wheels, the angular velocity of the upper wheel simulates the road surface, its movement allows to estimate the vehicle's longitudinal velocity. In the observer design, it is assumed that the angular velocity of the vehicle's wheel is known, since a sensor is installed on the system, as it is in a real vehicle, so the longitudinal velocity can be estimated with this information. The proposed nonlinear observer takes the Pacejka's Magic Formula to calculate the contact force. The magic formular allows the obseerver to estimate the states in both; the linear and nonlinar regions. The stability is proved and validated with simulations, and experimentally, with the Antilock Braking System Laboratory setup.