Wheel slip angle detecting system for vehicle

Abstract

A travel state of a vehicle is detected by a travel-state detecting device. A lateral slip angle of a vehicle body is calculated as a first lateral slip angle in a first lateral slip angle calculating device by integrating a differentiated value of lateral slip angle determined based on a non-linear four-wheel vehicle's motion model. A lateral slip angle of the vehicle body is calculated as a second lateral slip angle in a second lateral slip angle calculating device by a calculation in a linear two-wheel vehicle's motion model. One of the first and second lateral slip angles is selected alternatively in a selecting device in accordance with the travel state detected by the travel-state detecting device such that the second lateral slip angle is selected when the travel-state detecting device detects a state in which the vehicle is traveling straightforwardly at a low speed. A slip angle of each of wheels is calculated by a slip angle calculating device based on the lateral slip angle selected in the selecting device. Thus, the lateral slip angle of the vehicle body can be calculated with good accuracy using an appropriate calculating equation depending on the travel state of the vehicle, and the wheel slip angle can be determined with good accuracy using the lateral slip angle of high accuracy.