Tracking filter apparatus for wheel monitoring systems
First Claim
1. A wheel monitoring system, comprising:
- a wheel monitoring device that is mountable on a wheel and configured to generate a first signal that is indicative of a characteristic of said wheel, said first signal having a main frequency that varies corresponding to a variation of a rotational speed of said wheel; and
a tracking filter apparatus, comprising;
an input configured to receive said first signal from said wheel monitoring device;
an adjustable filter having an adjustable cut off frequency and configured to filter said first signal to produce a filtered first signal; and
a filter controller being co-operable with said adjustable filter and being configured to;
measure a characteristic of said filtered first signal; and
compare said characteristic of said filtered first signal against a reference value;
adjust said adjustable cut off frequency corresponding to a variation of said main frequency when said characteristic of said filtered first signal differs from said reference value by an amount that exceeds a threshold value,wherein said filtered first signal has a main signal component at said main frequency, said main signal component having an amplitude,wherein said characteristic of said filtered first signal comprises a peak said amplitude of said main signal component,wherein said filter controller comprises a peak detector configured to;
detect the peak amplitude of said filtered first signal, andgenerate a direct current signal comprising an amplitude that is indicative of said detected amplitude of said filtered first signal.
2 Assignments
0 Petitions
Accused Products
Abstract
A wheel monitoring system that includes a tracking filter apparatus for tracking a signal that has a varying main frequency. The tracking filter apparatus has an adjustable filter and a filter controller arranged to measure the amplitude of the filtered signal and to compare amplitude against a reference value. The filter controller adjusts the cut off frequency of the filter if the measured amplitude differs from the reference value by an amount that exceeds a threshold value. The filter controller adjusts the cut off frequency such that the main frequency lies within the roll off region of the filter'"'"'s frequency response. The system may be used to track signals that are produced by shock sensors in a wheel mounted monitoring device.
7 Citations
21 Claims
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1. A wheel monitoring system, comprising:
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a wheel monitoring device that is mountable on a wheel and configured to generate a first signal that is indicative of a characteristic of said wheel, said first signal having a main frequency that varies corresponding to a variation of a rotational speed of said wheel; and a tracking filter apparatus, comprising; an input configured to receive said first signal from said wheel monitoring device; an adjustable filter having an adjustable cut off frequency and configured to filter said first signal to produce a filtered first signal; and a filter controller being co-operable with said adjustable filter and being configured to; measure a characteristic of said filtered first signal; and compare said characteristic of said filtered first signal against a reference value; adjust said adjustable cut off frequency corresponding to a variation of said main frequency when said characteristic of said filtered first signal differs from said reference value by an amount that exceeds a threshold value, wherein said filtered first signal has a main signal component at said main frequency, said main signal component having an amplitude, wherein said characteristic of said filtered first signal comprises a peak said amplitude of said main signal component, wherein said filter controller comprises a peak detector configured to; detect the peak amplitude of said filtered first signal, and generate a direct current signal comprising an amplitude that is indicative of said detected amplitude of said filtered first signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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18. A wheel monitoring system, comprising:
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a wheel monitoring device that is mountable on a wheel and configured to generate a first signal that is indicative of a characteristic of said wheel, said first signal having a first main frequency that varies corresponding to a variation of a rotational speed of said wheel; and a first tracking filter apparatus, comprising; a first input configured to receive said first signal from said wheel monitoring device; a first adjustable filter having a first adjustable cut off frequency and configured to filter said first signal to produce a filtered first signal; a filter controller being co-operable with said first adjustable filter and being configured to; measure a characteristic of said filtered first signal; compare said characteristic of said filtered first signal against a reference value; and adjust said first adjustable cut off frequency when said characteristic of said filtered first signal differs from said reference value by an amount that exceeds a threshold value; wherein said wheel monitoring device comprises a first motion sensor, said first signal being generated by said first motion sensor; a second motion sensor, generating a second signal that is indicative of said characteristic of said wheel, said second signal having a second main frequency that is corresponding to said rotational speed of said wheel, said wheel monitoring system further comprising; a second tracking filter apparatus, comprising; an second input configured to receive said second signal; and an second adjustable filter having an second adjustable cut off frequency and configured to filter said second signal to produce a filtered second signal, and wherein said second filter controller being co-operable with said adjustable filter and being configured to; measure a characteristic of said filtered second signal; and compare said characteristic of said filtered second signal against said reference value; adjust said second adjustable cut off frequency when said characteristic said filtered second signal differs from said reference value by an amount that exceeds a threshold value, and said wheel monitoring system further comprising; a phase detector, each of said first and second filtered signals being provided to the phase detector, said phase detector being configured to determine a phase relationship between said first and second filtered signals. - View Dependent Claims (19)
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20. A wheel monitoring system, comprising:
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a wheel monitoring device that is mountable on a wheel and configured to generate a first signal that is indicative of a characteristic of said wheel, said first signal having a main frequency that varies corresponding to a variation of a rotational speed of said wheel; and a tracking filter apparatus, comprising; an input configured to receive said first signal from said wheel monitoring device; an adjustable filter having an adjustable cut off frequency and configured to filter said first signal to produce a filtered first signal; and a filter controller being co-operable with said adjustable filter and being configured to; measure a characteristic of said filtered first signal; and compare said characteristic of said filtered first signal against a reference value; adjust said adjustable cut off frequency corresponding to a variation of said main frequency when said characteristic of said filtered first signal differs from said reference value by an amount that exceeds a threshold value; an adjustable impedance module connected between said input and said adjustable filter, said adjustable impedance module being controllable by said filter controller to adjust impedance of said adjustable impedance module when said characteristic of said filtered first signal differs from said reference value by an amount that exceeds a threshold value, wherein said adjustable impedance module comprises a network of transistors, wherein said filter controller is configured to provide a pulse width modulated clock signal to a bias control input of said network to control a bias current of said transistors.
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21. A method of tracking a main frequency component of a first signal in a wheel monitoring system, said main frequency varying corresponding to a variation of a rotational speed of a wheel, wherein said wheel monitoring system comprises:
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an adjustable filter having an adjustable cut off frequency and a control input configured to receive a clock signal, wherein the clock signal controls said adjustable cut off frequency of said adjustable filter, and a filter controller co-operable with said adjustable filter, the method comprising; filtering said first signal, by said wheel monitoring system, to produce a filtered first signal; measuring, by said wheel monitoring system, at least one characteristic of said filtered first signal; comparing, by said wheel monitoring system, said characteristic of said filtered first signal against a reference value; and adjusting, by said wheel monitoring system, said adjustable cut off frequency when said characteristic of said filtered first signal differs from said reference value by an amount that exceeds a threshold value, deriving, by said wheel monitoring system, from said clock signal a measure of said rotational speed of said wheel; comparing, by said wheel monitoring system, said measure of said wheel speed against an alternative measure of said wheel speed; and determining, by said wheel monitoring system, that said adjustable filter is operating correctly if said measure and said alternative measure of said wheel speed substantially match.
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Specification