A non-scanning ultrasonic sensor for driver assistant systems

Describes an improvement of ultrasonic environment-sensors for driver assistant systems. Ultrasonic sensors are effective under bad weather conditions where the optical sensors are ineffective. However, they have a fatal weak point that their longitudinal detectable range is very short. Moreover, because the propagation velocity of sound waves is slow, we cannot use a scanning method. Therefore, the authors extended the longitudinal detectable range by increasing the power of emitted sound wave and shortening the sensing time by using multi-receiver method. In order to detect the relative velocity between vehicle and objects, Doppler shift was measured by using FM (frequency modulation) method. Because, this FM method requires complex electric circuits, a DSP was used for simplifying the circuits. Sometimes, walls located at both side of the ultrasonic sensor cause a mis-detection of objects. Thus, a method to avoid this miss-detection is proposed in the paper. Experiments were carried out and useful results were obtained.