Patent ID: 6490227
Filing Date: 2002-12-03
Classification: B66F,G01S

Abstract:
A device for detecting the position of a movable body that moves in a predetermined move range, comprising:an ultrasonic sensor, wherein the ultrasonic sensor emits ultrasonic waves toward the movable body and receives ultrasonic waves that are reflected by the movable body; and a controller for controlling the ultrasonic sensor, wherein the controller controls the ultrasonic sensor to consecutively emit a plurality of ultrasonic waves that have different amplitudes at predetermined intervals, thereby measuring the distance between the ultrasonic sensor and the movable body, and wherein the controller computes the distance between the ultrasonic sensor and the movable body based on a period from when the ultrasonic sensor emits one of the ultrasonic waves to when the ultrasonic sensor receives the one ultrasonic wave that is reflected by the movable body, wherein the move range of the movable body is divided into a plurality of measurement sections, wherein each ultrasonic wave is assigned to one of the measurement sections, wherein the controller uses each ultrasonic wave for detection in the corresponding measurement section, and wherein the range of each measurement section is determined such that the maximum detectable distance defined by that measurement section is less than the maximum distance detectable by using the corresponding ultrasonic wave.