Trw Limited

Michelle Renee Schaffran

Frederic Marcel Sejalon

Stephen R Cooper

An ultrasonic sensor system (40) has a transducer (44) that emits an ultrasonic signal (52), in response to an electrical excitation signal (50) from driver/receiver circuitry (46), and outputs an electrical response signal (56), in response to receipt of a reflected ultrasonic signal (54) from an occupant (54). The transducer (44) rings-down upon termination of the excitation signal (50). The transducer (44) has a natural resonant frequency that is subject to change. In an occupant sense mode, a receiver portion (68) of the driver/receiver circuitry (46) and a controller (30) process the response signal (56), resulting from transducer excitation at a predetermined frequency, to determining distance between the transducer (44) and the occupant (14). In an adjust mode, the controller (30) varies the frequency of the excitation signal (50) over a range of frequencies, and monitors the ringdown of the transducer (44) during the variation of the frequency to determine a current natural resonant frequency of the transducer (44). The controller (30) changes the predetermined frequency to the determined natural resonant frequency, so that subsequent operation in the sense mode utilizes the resonant frequency.

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Novi, MI, United States of America

Michelle Renee Schaffran