An ultrasonic sensor for distance measurement in automotive applications

TLDR

The paper presents an ultrasonic sensor for measuring ground distance at selected vehicle points. The sensor uses time‑of‑flight of a 40 kHz ultrasonic pulse reflected by the ground, with a constrained‑optimization technique that accounts for transducer frequency response to enable sub‑wavelength detection via a threshold comparator. Experimental tests show a 1 mm standard uncertainty at rest or low speeds, acceptable performance up to 30 m/s, and the low‑cost sensor self‑adapts to conditions, making it suitable for first‑car equipment.

Abstract

This paper describes an ultrasonic sensor that is able to measure the distance from the ground of 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. A constrained optimization technique is employed to obtain reflected pulses that are easily detectable by means of a threshold comparator. Such a technique, which takes the frequency response of the ultrasonic transducers into account, allows a sub-wavelength detection to be obtained. Experimental tests, performed with a 40 kHz piezoelectric-transducer based sensor, showed a standard uncertainty of 1 mm at rest or at low speeds; the sensor still works at speeds of up to 30 m/s, although at higher uncertainty. The sensor is composed of only low cost components, thus being apt for first car equipment in many cases, and is able to self-adapt to different conditions in order to give the best results.