Estimation of Tire-Road Friction by Tire Rotational Vibration Model

Tire-road friction is the most important piece of information used by active safety systems. However, most conventional friction estimation/ detection methods are accurate only within the non-linear region. In addition, such methods require numerous sensors, such as yaw rate sensors, acceleration sensors, and steering angle sensors. In this paper, a friction estimation method using a tire vibration model is proposed. The method is based on the frequency characteristics of wheel speed vibration, which are related to tire-road friction. The recursive least squares and instrumental variable methods are applied for on-line estimation. The experimental results show that, when applied to a free-rolling tire, the proposed method detects friction change from dry asphalt to iced road while the vehicle travels at constant speed without braking, accelerating, or cornering.