Device and method for detecting position of movable body by using ultrasonic waves

摘要

An ultrasonic sensor is located in the bottom of a lift cylinder of a forklift and emits ultrasonic waves toward a piston in the cylinder. A controller controls the ultrasonic sensor to consecutively emit ultrasonic waves that have different amplitudes at predetermined intervals. The ultrasonic waves are emitted in order of smallness of amplitude. The controller computes the distance between the ultrasonic sensor and the piston based on a period from when the ultrasonic sensor emits one of the ultrasonic waves to when the ultrasonic sensor receives the ultrasonic wave that is reflected by the piston. As a result, the range of the detectable distances is extended.