A simple ultrasonic ranging system

Abstract

There are many instances in robot design where an inexpensive compact ranging system can be of great benefit. The system developed by a well-known camera company to automatically focus cameras is ideally suited to such applications. This system is composed of an electrostatic transducer and a single electronic module containing the drive, receiving, and processing circuitry. It can be used effectively to measure distance or detect the presence of objects within a range of 0.9–35 ft, operating at four discrete frequencies between 50 and 60 kHz. The system exhibits an acceptance angle of approximately 20°. To determine the distance to an object, the time interval between the transmit signal and the received echo must be externally determined. With an appropriate clock, a resolution of 0.25 in. can be obtained. Correction for changes in air temperature must be made to attain good resolution and accuracy throughout a wide temperature range. The system can therefore be used to map a robot's environment, or simply provide an effective means of collision avoidance.