A low-cost contactless distance meter for automotive applications

This paper describes an ultrasonic sensor that is able to measure the distance from the ground from selected points of a motor vehicle. The sensor is based on the measurement of the time of flight of an ultrasonic pulse, which is reflected by the ground. An uncertainty of 1 mm (1 σ) is obtained at rest or at low speeds; the sensor still works at speeds of up to 30 m/s although at reduced accuracy. Such a performance is obtained by employing a series of optimisation that allow the sensor to self-adapt to the different conditions to give the bests results. The sensor is composed of only low cost components, thus being apt for first car equipment in many cases.