Ultrasonic transducers for robotic applications

Abstract

A new family of ultrasonic transducers will be described that are especially useful as position sensing probes in many robotic applications. Low-frequency (20–40 kHz) transducers using small exponential horns achieve efficiencies in the order of 50%, and are used for long-range (50-ft) distance measuring. High-frequency (200- to 500-kHz) transducers utilizing planar mode vibrating ceramic discs in combination with quarter-wavelength acoustic waveguides eliminate secondary lobes and are particularly useful for making shorter range measurements and for achieving very high resolution (± 0.001 in.) at close ranges. The new transducers provide a wide variety of beam angles from virtually omnidirectional to 5° conical. The transducer designs to be described operate on either the fundamental or on a controlled overtone mode of the vibratile element, depending on the frequency region of operation required. Special sensing modules will be shown which include the interface circuitry permitting simple control of the ultrasonic sensing probe by logic signal commands produced by the robot's computer.