Proposal of road friction coefficient estimator focused tire characteristic

In the preventive safety field, AEBS (Advanced Emergency Braking System) has been widely spread to the market. AEBS is composed of alert-braking and full-braking, and when AEBS works, ABS (Antilock Brake System) is often used simultaneously. In order to use braking force to the maximum, it is desirable for ABS to take into account a road friction coefficient because the tire slip ratio where the maximum force is generated is varied in accordance with the road friction coefficient. Furthermore, road friction coefficient estimator is difficult to be realized. As the control of ABS depends on only tire slip ratio, it cannot generate tire braking force sufficiently on the various road surface condition. In this paper, we propose a technique to estimate road friction coefficient during alert-braking period. In addition, we changed the target tire slip ratio required by ABS based on road friction coefficient. It was found that by using the method mentioned above, it was possible to reduce the collision speed compared with the conventional system.