Data processing: measuring – calibrating – or testing – Measurement system – Measured signal processing
Reexamination Certificate
2001-03-02
2004-01-20
Barlow, John (Department: 2863)
Data processing: measuring, calibrating, or testing
Measurement system
Measured signal processing
C702S190000, C702S001000, C702S014000, C702S016000, C702S017000, C702S191000, C702S006000, C702S035000, C702S066000, C702S085000, C600S410000, C600S431000, C600S437000, C600S500000, C600S509000, C382S236000, C382S232000, C382S100000, C382S103000, C382S240000, C382S248000, C367S031000, C367S039000, C367S053000, C367S063000, C367S072000
Reexamination Certificate
active
06681199
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a peak time detecting apparatus and a peak time detecting method and, more particularly, to a peak time detecting apparatus that detects a peak time of time-series signals by using the wavelet transformation and a peak time detecting method that detects a peak time of time-series signals inputted by using the wavelet transformation.
2. Description of the Related Art
Various peak time detecting methods of the aforementioned type have been proposed, including a method in which a differential coefficient is calculated with respect to input time-series signals and, based on fluctuations of the differential coefficient, a peak and a peak time are detected, a method in which a maximum value of input time-series signals is tracked, and the maximum value retained before the signal value decreases below a pre-set threshold is set as a peak value, and the time point of detection of the maximum value is detected as a peak time, etc.
However, in the method of detecting a peak time based on fluctuations of the differential coefficient, false detection by noises is likely to occur, and the reliability is low. In the method in which when an input time-series signal drops below a pre-set threshold, the time of detection of the current maximum value is set as a peak time, detection of a peak time cannot be performed until an input signal is less than the threshold, and therefore detection of a peak time requires an amount of time.
A first peak of signals from a deceleration sensor used to activate an occupant protection apparatus that protects occupants at the time of a crash of the vehicle, such as an airbag apparatus of the like, is normally found when a bumper reinforcement provided forward of side members of a vehicle yields to an impact. Input signals up to the proximity of the first peak are used to determine a form of crash (a frontal collision, a diagonal collision, an offset collision, etc.), or to determine a timing of activating an occupant protection apparatus and a kind of the activation of the occupant protection apparatus, although the situation may vary depending on the configuration of a vehicle. If a peak time is detected with respect to signals from the deceleration sensor used by the occupant protection apparatus, the detection precision and the promptness in detecting a peak time become important factors.
SUMMARY OF THE INVENTION
It is an object of the peak time detecting apparatus and the peak time detecting method of the invention to reduce the false detections cased by noises or the like so as to detect the peak time of signals that are more precisely inputted. It is another object of the peak time detecting apparatus and the peak time detecting method of the invention to promptly detect a peak time. Furthermore, it is an object of the peak time detecting apparatus of the invention to determine the validity of peak time detection.
In order to achieve at least one of the aforementioned objects, the peak time detecting apparatus and the peak time detecting method of the invention adopt the following means.
A peak time detecting apparatus in accordance with a first aspect of the invention is a peak time detecting apparatus peak time detecting apparatus for detecting a peak time of a time-series signal by using a wavelet transformation, including: signal input means for inputting the time-series signal; product-sum operation means for performing a product-sum operation with respect to the time-series signal inputted, by using a predetermined complex function as an integral base; phase calculation means for calculating a phase based on a real number portion and an imaginary number portion of a result of the product-sum operation; and peak time determination means for determining a peak time of the time-series signal based on the phase calculated.
In the peak time detecting apparatus of the first aspect of the invention, the product-sum operation means performs the product-sum operation with respect to the time-series signal inputted by the signal input means, by using a predetermined complex function as a base of integral. The phase calculation means calculates a phase based on the real number portion and the imaginary number portion of a result of the product-sum operation. The peak time determination means determines a peak time of the time-series signal based on the calculated phase. The wavelet transformation is excellent for the analysis of a time-series signal in a time region and a frequency region, in comparison with a short-time Fourier transformation. If a transformation frequency and waveforms of the real number portion and the imaginary number portion are suitably selected, the wavelet transformation allows analysis of a targeted signal. The peak time detecting apparatus of the first aspect detects a peak time of a time-series signal through the use of a signal analysis based on the wavelet transformation.
Since the peak time detecting apparatus of the first aspect performs the product-sum operation with respect to the input time-series signal by using the predetermined complex function, and does not perform a differential operation, the peak time detecting apparatus is able to avoid false detection based on noises. As a result, the detection precision can be improved. Furthermore, since the determination of a peak time is performed based on the phase calculated based on the real number portion and the imaginary number portion of a result of the product-sum operation, the determination can be made immediately after an actual peak. Therefore, the apparatus is able to detect a peak time quickly, in comparison with an apparatus that determines a peak time when the signal becomes lower than a pre-set threshold. Furthermore, the arithmetic operations performed in the apparatus are the product-sum operation with respect to the time-series signal, the phase calculation with respect to a result of the product-sum operation, etc, and can be quickly performed. Therefore, a peak time can be promptly detected.
In the peak time detecting apparatus of the first aspect of the invention, the product-sum operation means may be means that uses a Gabor function as the predetermined complex function. Furthermore, the product-sum operation means may also be means that uses, as the predetermined complex function, a function that includes a real number portion having a localized waveform and an imaginary number portion having a localized waveform that is delayed by &pgr;/2 in phase from the real number portion. In the thus-constructed peak time detecting apparatus of the invention, the peak time determination means may be means for determining, as the peak time, a time point at which the phase calculated by the phase calculation means changes from 2&pgr; to zero. If a function that has a real number portion having a localized waveform and an imaginary number portion having a localized waveform that is delayed by &pgr;/2 in phase from the real number portion, including the Gabor function, is used as a base of integral, the product sum of the real number portion becomes a positive value when the real number portion is superimposed on a peak of the signal. In that case, the imaginary number portion, being delayed by &pgr;/2 in phase, assumes zero, and therefore the product sum of the imaginary number portion is zero. Therefore, by suitably selecting signs of the real number portion and the imaginary number portion, it becomes possible to determine a time point at which the phase calculated based on the real number portion and the imaginary number portion of a result of the product-sum operation changes from 2&pgr; to zero, as a time at which the signal is at a peak.
The peak time detecting apparatus of the first aspect of the invention may further include validity determination means for determining a validity of a result of determination made by the peak time determination means. Therefore, the validity of the detected peak time can be taken into account. In the thus-constructed peak time detecting ap
Imai Katsuji
Iyoda Motomi
Oshima Masuji
Barlow John
Bhat Aditya
Kenyon & Kenyon
Toyota Jidosha & Kabushiki Kaisha
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