Use of Fuzzy Logic in Wheel Slip Assignment - Part I: Yaw Rate Control

This paper describes the use of logic-based control for the purpose of determining and assigning desired wheel slips for each corner of a vehicle. The control objective is to track overall desired vehicle dynamics, such as tracking a desired vehicle yaw rate, Ω_d, by assigning an appropriate wheel slip, λ, to each corner of the vehicle. Each of these wheel slips is used as reference input wheel slip, λ_r, for a wheel dynamics control system. This setup can be thought of behaving like a hierarchical control system (higher-level control system interacting with a lower level control system). This paper focuses on developing the higher-level logic based controller. The logic controller uses fuzzy logic control techniques. In conventional fuzzy logic control, a two-dimensional rule table is created based on the error between the desired and actual signals, and on the change in the error. The fuzzy logic controller presented in this paper is based on the work performed by Choi, et.al. [5]. This method combines the two controller inputs into a single input. The rule table elements are filled in, and adjusted based on the expertise of the designer. A rule table is created for each wheel based on how a wheel is classified in relationship to the turn of the vehicle (i.e. inside front, outside rear). These classifiers are then assigned to the appropriate wheel online. An emergency lane change simulation is performed to show the effectiveness of the control.