A small expendable wideband low-frequency sound source that will be deployed on the seafloor is being developed to be used for geoacoustic inversion surveys in conjunction with a terrain-hugging AUV. This low-cost deployable source contains a transducer that produces a relatively flat transmit response over the broad frequency band of 100 to 4000 Hz. In operation, a seafloor interface wave will be excited and exploited for geoacoustic inversion by the deployed sound source and a receiving array on the bottom-hugging AUV. A feasibility study is also being performed that includes physics-based sonar simulations to infer the performance of geoacoustic inversion in a number of AUV scenarios and environmental conditions. Based on this study, design trade-offs will be determined to finalize key factors of the transducer, such as its physical size, weight, and production cost. Battery technology is also being developed to optimize the source level, the duty cycle, and the operating life of the signals that will be transmitted during data collection. This effort is being supported by ONR.

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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.

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