US3925643A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Drift correcting gyro system using filters
Assignee: RTX Corp
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Filing: 1974-05-13
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Granted: 1975-12-09
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Expires: 1994-05-13
Abstract
Abstract Drift components in the output of a gyro in a strapdown inertial navigation system are measured by modulating the speed of the gyro wheel in a sinusoidal manner. True angular motion components acting on the gyro are modulated in proportion to the modulation of the wheel speed, while drift components which act on the gyro and which are independent of true motion and wheel momentum are not modulated. By the use of a drift calculator or selected bandpass filters responsive to the modulated output from the gyro, the drift component and true angular motion component may be separated, and the navigation system may be compensated for drift. A unique linear-parabolic modulator produces a digital output equivalent to a sinusoid which may be used to modulate the gyro wheel speed in the appropriate manner.
Inventors
- 👤 James P Roantree
- 👤 John Saunders
- 👤 Robert A Baum
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 10:13
CPC Classifications
G; G01; G01C; G01C19/00; G01C19/02; G01C19/04; G01C19/42
Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
235 words
In a control system containing a strapdown gyro which is subject to external angular motion and which produces an output signal containing a component proportional to true angular motion and a component proportional to gyro drift, said gyro having a rotating wheel, the improvement of eliminating the drift component from the gyro output signal comprising means for cyclically modulating the speed of rotation of said gyro wheel to produce a modulation component in said gyro output signal, a band-pass amplifier having an input and an output and tuned to the wheel speed modulation frequency, a band-reject amplifier having an input and an output and tuned to the wheel speed modulation frequency, means for connecting said gyro output signal to the inputs of said band-pass amplifier and said band-reject amplifier, a summing junction connected to the outputs of said band-pass amplifier and said band-reject amplifier, a high pass filter having an input and an output, means connecting said summing junction with the input to said high pass filter, a demodulator having an input and an output and tuned to the wheel speed modulation frequency, means connecting the output from said band-pass amplifier with said demodulator, a low pass filter having an input and an output, means connecting the output of said demodulator with the input of said low pass filter, and means for combining the outputs from said high pass filter and said low pass filter.
Claim 2
Dependent Claim
235 words
In a control system containing a strapdown gyro which is subject to external angular motion and which produces an output signal containing a component proportional to true angular motion and a component proportional to gyro drift, said gyro having a rotating wheel, the improvement of eliminating the drift component from the gyro output signal comprising means for cyclically modulating the speed of rotation of said gyro wheel to produce a modulation component in said gyro output signal, a band-pass amplifier having an input and an output and tuned to the wheel speed modulation frequency, a band-reject amplifier having an input and an output and tuned to the wheel speed modulation frequency, means for connecting said gyro output signal to the inputs of said band-pass amplifier and said band-reject amplifier, a summing junction connected to the outputs of said band-pass amplifier and said band-reject amplifier, a high pass filter having an input and an output, means connecting said summing junction with the input to said high pass filter, a demodulator having an input and an output and tuned to the wheel speed modulation frequency, means connecting the output from said band-pass amplifier with said demodulator, a low pass filter having an input and an output, means connecting the output of said demodulator with the input of said low pass filter, and means for combining the outputs from said high pass filter and said low pass filter.
Claim 3
Dependent Claim
33 words
Apparatus as in claim 1 in which said means for cyclically modulating the speed of rotation of said gyro wheel comprises means for sinusoidally modulating the speed of rotation of said gyro wheel.
Claim 4
Dependent Claim
25 words
Apparatus as in claim 1 and including a torquing coil connected with said gyro, and means for connecting said summing junction with said torquing coil.
Claim 5
Dependent Claim
52 words
Apparatus as in claim 1 and including a pickoff connected with said gyro, a pickoff power supply for exciting said pickoff at a selected frequency, filter means having an input and an output and tuned to said pickoff excitation frequency, and means connecting said pickoff to the input to said filter means.
Claim 6
Dependent Claim
212 words
In a control system containing a strapdown gyro which is subject to external angular motion and which produces an output signal containing a component proportional to true angular motion and a component proportional to gyro drift, said gyro having a rotating wheel, the improvement of eliminating the drift component from the gyro output signal comprising means for cyclically modulating the speed of rotation of said gyro wheel to produce a modulation component in said gyro output signal, first and second filter means tuned to the wheel speed modulation frequency for respectively producing from said gyro output signal a first signal proportional to the true angular motion and drift components and a second signal proportional to the modulation component of the true angular motion, summing means for combining said first and second signals to produce a third signal, a high pass filter connected to said summing means for removing the drift component and modulation component from said third signal, a demodulator tuned to the wheel speed modulation frequency for demOdulating said second signal, a low pass filter connected to said demodulator and passing therethrough only the low frequency portion of said true motion component from said demodulated second signal, and means for combining the outputs from said high pass and low pass filters.
Claim 7
Dependent Claim
212 words
In a control system containing a strapdown gyro which is subject to external angular motion and which produces an output signal containing a component proportional to true angular motion and a component proportional to gyro drift, said gyro having a rotating wheel, the improvement of eliminating the drift component from the gyro output signal comprising means for cyclically modulating the speed of rotation of said gyro wheel to produce a modulation component in said gyro output signal, first and second filter means tuned to the wheel speed modulation frequency for respectively producing from said gyro output signal a first signal proportional to the true angular motion and drift components and a second signal proportional to the modulation component of the true angular motion, summing means for combining said first and second signals to produce a third signal, a high pass filter connected to said summing means for removing the drift component and modulation component from said third signal, a demodulator tuned to the wheel speed modulation frequency for demOdulating said second signal, a low pass filter connected to said demodulator and passing therethrough only the low frequency portion of said true motion component from said demodulated second signal, and means for combining the outputs from said high pass and low pass filters.
Claim 8
Dependent Claim
25 words
Apparatus as in claim 5 and including a torquing coil connected with said gyro, and means for connecting said third signal with said torquing coil.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1978-12-08 | 1979-06-09 | 1979-12-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1982-12-08 | 1983-06-09 | 1983-12-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1986-12-08 | 1987-06-09 | 1987-12-09 | $7700.00 | Window Closed / Lapsed |