Noise canceling apparatus for weight measurement, and noise canceling method for weight measurement
First Claim
1. A noise canceling apparatus for weight measurement for eliminating a fixed-period vibration noise contained in a quantitative signal, said quantitative signal being a result of digitization of a signal obtained by detecting a weight of an object to be measured, said apparatus comprising:
- a band pass filter for filtering a frequency component of said quantitative signal at a plurality of notches, said filtering using variable filter coefficients; and
a coefficient control section for calculating a series of said filter coefficients, and supplying said series to said band pass filter, wherein said band pass filter has a frequency characteristic including said plurality of notches, and a transfer function of said band pass filter includes a product of a plurality of factors each having a root corresponding to each one of said plurality of notches, said coefficient control section comprising;
a frequency changing element for changing a frequency component of a root as a part of a factor, said root corresponding to a notch selected from said plurality of notches;
an expansion element for expanding a product of a plurality of factors in a polynomial, said product constituting said transfer function of said band pas filter; and
a coefficient calculating element for calculating a series of said filter coefficients on the basis of said polynomial.
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Accused Products
Abstract
A noise canceling apparatus (1) comprises an amplifier (10) for amplifying a measured signal (ms) outputted from a measuring device (3), an analog filter (11), an ADC (12), a digital filter (14), a coefficient control section (13), and a data input section (15). The digital filter (14) is a notch filter for attenuating a frequency component of a quantitative signal D(n) outputted from the ADC (12) at a plurality of notches (stop bands). A transfer function of the digital filter (14) is expressed by the product of a plurality of factors each having a root that corresponds to each one of the plurality of notches. The coefficient control section (13) changes a frequency component of a root corresponding to a notch selected from the plurality of notches, and thereafter, expands in a polynomial the transfer function of the reconstructed digital filter (14). On the basis of the polynomial thereby obtained, a new series of filter coefficients is calculated. A filter characteristic is controlled in such a manner that it conforms to a frequency variation of a fixed-period vibration noise, whereby the fixed-period vibration noise that varies in frequency is attenuated with a high degree of precision.
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Citations
16 Claims
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1. A noise canceling apparatus for weight measurement for eliminating a fixed-period vibration noise contained in a quantitative signal, said quantitative signal being a result of digitization of a signal obtained by detecting a weight of an object to be measured, said apparatus comprising:
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a band pass filter for filtering a frequency component of said quantitative signal at a plurality of notches, said filtering using variable filter coefficients; and
a coefficient control section for calculating a series of said filter coefficients, and supplying said series to said band pass filter, wherein said band pass filter has a frequency characteristic including said plurality of notches, and a transfer function of said band pass filter includes a product of a plurality of factors each having a root corresponding to each one of said plurality of notches, said coefficient control section comprising;
a frequency changing element for changing a frequency component of a root as a part of a factor, said root corresponding to a notch selected from said plurality of notches;
an expansion element for expanding a product of a plurality of factors in a polynomial, said product constituting said transfer function of said band pas filter; and
a coefficient calculating element for calculating a series of said filter coefficients on the basis of said polynomial. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A noise canceling method for weight measurement for eliminating a fixed-period vibration noise contained in a quantitative signal, said quantitative signal being a result of digitization of a signal obtained by detecting a weight of an object to be measured, said method comprising the steps of:
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(a) calculating a series of filter coefficients for a band pass filter; and
(b) causing a band pass filter to filter a frequency component of said quantitative signal at a plurality of notches, said band pass filter having a series of said filter coefficients, wherein said band pass filter has a frequency characteristic including said plurality of notches, and a transfer function of said band pass filter includes a product of a plurality of factors each having a root corresponding to each one of said plurality of notches, said step (a) comprising the steps of;
(a-1) changing a frequency component of a root as a part of a factor, said root corresponding to a notch selected from said plurality of notches;
(a-2) expanding a product of a plurality of factors in a polynomial, said product constituting said transfer function of said band pass filter; and
(a-3) calculating a series of said filter coefficients on the basis of said polynomial. - View Dependent Claims (10, 11, 12, 13, 14, 15, 16)
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Specification