Patent ID: 6279396
Filing Date: 2001-08-28
Classification: G01S

Abstract:
An ultrasonic-wave distance measurement method of a separate transmission and reception type reflection system which receives an ultrasonic wave emitted from an ultrasonic-wave transmission sensor and reflected at a distance measured object by an ultrasonic-wave reception sensor, measures a time from the transmission of the ultrasonic wave to the reception of the same, and performs sensitivity correction in accordance with a type of the distance measured when measuring the distance between the ultrasonic-wave transmission sensor or the ultrasonic-wave reception sensor and the distance measured object from the obtained time,said method including the following steps of:measuring a time from the transmission of an ultrasonic wave emitted from the ultrasonic-wave transmission sensor to the distance measured object to the reception of the same, calculating a provisional distance from the measured time, measuring attenuation characteristics of the reflected ultrasonic-wave by comparing an amplitude with a reference reflection ultrasonic-wave, and preparing ultrasonic-wave sensor sensitivity correction data from the attenuation characteristics with respect to every type of distance measured object and various distances between the distance measured object and the ultrasonic-wave transmission sensor or the ultrasonic-wave reception sensor;setting a type of the distance measured object prior to an actual distance measured;starting counting simultaneously with the emission of an ultrasonic-wave signal to the distance measured object by driving the ultrasonic-wave reception sensor,stopping the counting simultaneous with the reception of the reflected wave by the ultrasonic-wave reception sensor, measuring an elapsed time from the driving of the ultrasonic-wave transmission sensor to the reception of the reflected wave by the ultrasonic-wave reception sensor, calculating a provisional distance between the ultrasonic-wave transmission sensor or the ultrasonic-wave reception sensor and the distance measured object based on the elapsed time, generating ultrasonic-wave sensor sensitivity correction data for reception corresponding to the calculated provisional distance and the set type of the distance measured object, and enabling sensitivity correction related to the sensor sensitivity correction data in an ultrasonic-wave signal sensitivity correction portion for reception;starting counting a time simultaneously with the emission of the ultrasonic-wave signal to the distance measured object by driving the ultrasonic-wave transmission sensor again; andstopping the counting simultaneously with the reception of a reflected wave larger than a predetermined level by the ultrasonic-wave reception sensor again, measuring a time from the driving of the reflected wave by the ultrasonic-wave transmission sensor to the reception of the reflected wave by the ultrasonic-wave reception sensor, and calculating the actual distance between the ultrasonic-wave transmission sensor or the ultrasonic-wave reception sensor and the distance measured object based on the measured time.