Abstract
For the vehicle safety system, the informatin regarding a tire is becoming more necessary since it is an important interface between road and vehicle. Intelligent tire concept which utilizes a tire as a sensor or as a part of sensor system is one of the choices for monitoring the information. Compared to the other methods using the existing sensors in vehicle, intelligent tire is considered to be more direct sensing method close to the contacting surface. In this paper, two types of developed sensing algorithm based on the sensor signal around the contact patch are presented. They are named Contact Area Information Sensing (CAIS) technology. To sense the information at contact area, the sensors of these intelligent tires are located at inner liner of tread portion.
CAIS Type I has two strain sensors in the middle area of the tread portion. Using the time information of sensor signals, dynamic tire/road interaction is estimated. It utilizes the basic correlation between contact patch shape and tire forces. However, there are many factors needed to be considered under the actual situation. By understanding the tire deformation, the robust algorithm including the compensation for the effects of those factors, which are camber angle and so on, has been developed. The estimation outputs are lateral force, vertical load, camber angle, and slip angle. The real-time signal processing program was verified well through the field tests.
The target of CAIS Type II is the estimation of road condition related with the potential friction coefficient , especially while driving in a steady state which is before the action to avoid the danger. Type II has a one-axis accelerometer at the center of the tread portion to detect the small change of tire behavior according to the road condition. Based on the observation of detail tire behavior on different surfaces, and also on the various driving conditions, the robust algorithm to classify the road sufaces has been developed. Through the field tests, very high percentages of correct road classification were obtained.
Keywords:Intelligent tire, sensor, algorithm, friction, contact area