Ultrasound transducer temperature compensation methods, apparatus and programs

Abstract

Method, apparatus and computer programs are described for compensating for the effect of temperature on the sensitivity of electrostatic ultrasound (US) transducers, particularly as used in an automotive occupancy sensing (AOS) systems for sensing the nature or type of occupant and the location of the occupant with respect to the vehicle interior. The invention permits the AOS to classify the occupancy state of the vehicle from a US echo signal substantially free of the effects of temperature on signal amplitude. A capacitive divider or voltage monitor is employed to measure the capacitance of the transducer. The voltage monitor output is used by the scaling algorithm of a compensator to determine the scaling factor to be applied to the US transducer signal to compensate for the effect of temperature on the transducer sensitivity. Calibration procedures and software are disclosed for determining the coefficients of the scaling algorithm to compensate for temperature effects and also to compensate for installation factors, transducer manufacturing variations, and circuit board effects. The system disclosed is useful for other types of signal processing in addition to temperature compensation of AOS ultrasonic signals, and may be used in other ranging devices such as cameras, golf or binocular range finders, and measuring devices and instruments.

Description

[0001] The invention relates to ultrasound (US) transducer temperature compensation methods, apparatus and programs, and more particularly to US transducers used in automotive occupancy sensing (AOS) systems for sensing the nature or type of occupant and the location of the occupant with respect to the vehicle interior. The system disclosed is useful for other types of signal processing in addition to temperature compensation of AOS ultrasound signals, and may be used in other ranging devices such as cameras, golf or binocular range finders, and measuring devices and instruments.[0002] Studies have revealed that there is a class of automotive accidents causing injuries associated with airbag deployment and with the nature and position of the vehicle occupant, particularly with respect to airbags deployed adjacent to seats occupied by children or infants in car seats. Automotive occupancy sensor (AOS) systems used in conjunction with airbag deployment systems (ADS) have been develope...

AI Technical Summary

Benefits of technology

[0013] The magnitude of the voltage monitor output signal permits the AOS microprocessor and software to utilize real-time transducer sensitivity data to normalize the received signal and optimize the occupancy classification algorithm performance.

Problems solved by technology

Studies have revealed that there is a class of automotive accidents causing injuries associated with airbag deployment and with the nature and position of the vehicle occupant, particularly with respect to airbags deployed adjacent to seats occupied by children or infants in car seats.

The electrostatic transducer response is highly temperature sensitive, and vehicle interiors have a large potential temperature range during operation, particularly when driving has just started after some period of non-use in hot or cold weather, and environmental controls such as heaters or air conditioners have not yet moderated extremes of heat or cold of the vehicle interior.

This approach has been tried with limited success, because in an ultrasound signal for occupant classification, a large amount of the distinguishing information is amplitude related, i.e., a lot of information needed for occupancy classification is present in the amplitude of the ultrasonic echo.

Amplitude changes due to temperature rather than due to changes in the state of the occupants or objects being imaged could result in false classifications.

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