Method for suppressing deployment of an inflatable restraint based on sensed occupant capacitance
First Claim
1. A method of determining whether to allow or suppress deployment of a vehicular inflatable restraint for a vehicle occupant based at least in part on an output signal of a sensor responsive to occupant capacitance relative to a vehicle seat, the method comprising the steps of:
- comparing a filtered version of said output signal to a threshold having a default value corresponding to a predetermined occupant capacitance under a given set of conditions;
determining a value of a parameter that affects a magnitude of said output signal;
adjusting said threshold above or below said default value when the determined parameter value is outside a predetermined range of values; and
allowing deployment of said restraint when the filtered version of said output signal is above said threshold, and suppressing deployment of said restraint when the filtered version of said output signal is below said threshold.
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Accused Products
Abstract
An improved method of selectively suppressing deployment of a vehicular inflatable restraint utilizes both static and dynamic variation in the measured capacitance of a vehicle occupant in a complementary manner that reduces overall system variability. The decision to allow or suppress deployment of the restraint is determined based on a comparison of the static capacitance reading with at least one threshold, and the dynamic variation of the measured capacitance and other parameters such as seat belt tension, seat humidity and seat temperature are used to adjust the threshold in a direction to minimize the overall variability of the system. In a preferred embodiment, the variation of the measured capacitance with respect to the variation in vertical acceleration of the vehicle is used to estimate the free capacitance of the occupant, and such free capacitance is used to adjust the threshold.
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Citations
9 Claims
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1. A method of determining whether to allow or suppress deployment of a vehicular inflatable restraint for a vehicle occupant based at least in part on an output signal of a sensor responsive to occupant capacitance relative to a vehicle seat, the method comprising the steps of:
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comparing a filtered version of said output signal to a threshold having a default value corresponding to a predetermined occupant capacitance under a given set of conditions;
determining a value of a parameter that affects a magnitude of said output signal;
adjusting said threshold above or below said default value when the determined parameter value is outside a predetermined range of values; and
allowing deployment of said restraint when the filtered version of said output signal is above said threshold, and suppressing deployment of said restraint when the filtered version of said output signal is below said threshold. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
measuring a vertical acceleration of the vehicle;
determining a value of said free capacitance based on a variation of said output signal with respect to a variation of the measured vertical acceleration;
adjusting said threshold below said default value when the determined value of said free capacitance is above a predetermined range of free capacitance values corresponding to an average capacitance occupant; and
adjusting said threshold above said default value when the determined value of said free capacitance is below the predetermined range of free capacitance values.
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3. The method of claim 2, wherein the step of determining a value of said free capacitance includes the steps of:
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sampling output signal values and computing an average of the sampled values;
identifying sampled output signal values that are within a specified percentage of said average;
computing a first variance of the identified output signal values;
computing a second variance of the measured vertical acceleration; and
determining the value of free capacitance according to a ratio of the first variance and the second variance.
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4. The method of claim 2, including the steps of:
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measuring a vehicle run time; and
delaying the step of determining the value of said free capacitance until the measured run time reaches a predetermined threshold.
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5. The method of claim 1, wherein said vehicle seat is equipped with a seat belt for restraining said occupant, and said parameter is a tension of said, seat belt, the method including the steps of:
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measuring the tension of said seat belt; and
adjusting said threshold above said default value when the measured tension is above a predetermined normal range.
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6. The method of claim 1, wherein said parameter is a temperature of said vehicle seat, the method including the steps of:
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measuring said temperature; and
adjusting said threshold below said default value when the measured temperature is below a predetermined normal range.
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7. The method of claim 1, wherein said parameter is a relative humidity of said vehicle seat, the method including the steps of:
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measuring said relative humidity; and
adjusting said threshold above said default value when the measured relative humidity is above a predetermined normal range.
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8. The method of claim 1, wherein said parameter is a variance of said output signal, the method including the steps of:
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adjusting said threshold below said default value when the variance of said output signal is above a predetermined range corresponding to an expected variance for an average weight occupant; and
adjusting said threshold above said default value when the variance of said output signal is below the predetermined range.
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9. The method of claim 8, including the steps of:
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sampling output signal values and computing an average of the sampled values;
identifying sampled output signal values that are within a specified percentage of said average;
computing the variance of the output signal based on the identified output signal values.
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Specification