Pneumatic monitor for a vehicle based on the disturbance observer

In this paper, a new method for detecting underinflated tires of a vehicle and a pneumatic monitor based on this method are proposed. Most of the monitors available are of the air pressure switch type and of the loaded radius type. However, the former is higher in manufacturing cost, and the latter has difficulty in detecting natural leaks causing all tires to be underinflated. In the new method, the variation of the tire stiffness which depends on the pressure is estimated by using a disturbance observer. This method is realized in lower cost because it needs only wheel speed sensors already provided for anti-lock brake system (ABS), and also can detect underinflated tires in every situation such as a puncture and natural leaks. The monitor is installed on a vehicle and its performance is confirmed by experiments.