US4016565A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Aircraft ground closure rate filtering method and means
Assignee: Boeing North American Inc
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Filing: 1975-09-15
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Granted: 1977-04-05
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Expires: 1995-09-15
Abstract
Abstract Ground closure rate between an aircraft and underlying terrain is obtained by differentially combining a radio altimeter derived rate signal and a barometric altitude rate signal to obtain a rate of change of ground profile signal. The ground profile rate is filtered on an autocorrelation basis to obtain a profile rate signal devoid of amplitude pulses introduced by sharp or discontinuous terrain features and recombined with barometric rate to obtain ground closure rate. The filtering technique imposes no rate limitation on the radio rate signal.
Inventors
- 👤 Ferman L. Walker
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 03:47
CPC Classifications
G; G01; G01C; G01C5/00; G01C5/005; G01S; G01S13/00; G01S13/88; G01S13/93; G01S13/933; G01S13/935
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
191 words
Signal development means for deriving an output signal definitive of the elevation rate of change between an aircraft and underlying ground terrain comprising: first means for developing a first signal definitive of the absolute closure rate between aircraft and underlying ground terrain, second means for developing a second signal definitive of barometrically determined aircraft rate of change of altitude, means for subtractively combining said first and second signals to develop a third signal definitive of the rate of change of terrain profile, filtering means; said filtering means comprising a signal integrating means, signal correlation responsive means comprising a further signal combining means receiving said third signal and the output of said signal integrating means as respective inputs thereto and responsive to an exponential correlation therebetween to provide a correlation defined output signal, said correlation defined output signal being applied as input to said signal integrating means; the output of said signal integrating means comprising the output of said filtering means; still further signal combining means additively combining said second signal and said output of said filtering means; and the output of said still further signal combining means comprising said output signal.
Claim 2
Dependent Claim
191 words
Signal development means for deriving an output signal definitive of the elevation rate of change between an aircraft and underlying ground terrain comprising: first means for developing a first signal definitive of the absolute closure rate between aircraft and underlying ground terrain, second means for developing a second signal definitive of barometrically determined aircraft rate of change of altitude, means for subtractively combining said first and second signals to develop a third signal definitive of the rate of change of terrain profile, filtering means; said filtering means comprising a signal integrating means, signal correlation responsive means comprising a further signal combining means receiving said third signal and the output of said signal integrating means as respective inputs thereto and responsive to an exponential correlation therebetween to provide a correlation defined output signal, said correlation defined output signal being applied as input to said signal integrating means; the output of said signal integrating means comprising the output of said filtering means; still further signal combining means additively combining said second signal and said output of said filtering means; and the output of said still further signal combining means comprising said output signal.
Claim 3
Dependent Claim
46 words
Signal development means as defined in claim 1, wherein said first signal is definitive of the time derivative of the altitude proportional output from a radio altimeter, and said second signal is definitive of the time derivative of the altitude proportional output from a barometric altimeter.
Claim 4
Dependent Claim
99 words
Signal development means as defined in claim 1 wherein said signal correlation responsive means comprises a signal translating means having a transfer function substantially defined by e - K |X|, where e is the natural logarithm base, K is a constant and X comprises the output from said further signal combining means as applied to said signal translating means, signal multiplying means receiving the output of said further signal combining means and the output of said signal translating means as respective inputs thereto, with the output of said signal multiplying means comprising the input to said signal integrating means.
Claim 5
Dependent Claim
38 words
Signal development means as defined in claim 3, wherein the transfer function of said signal integrating means is approximated as (1T 2 S), where T 2 is a predetermined time constant and S is the La Placian operator.
Claim 6
Dependent Claim
73 words
Signal development means as defined in claim 3, wherein said signal translating means and said multiplying means, the collective transfer function of which is defined as Xe≠ K |X|, are collectively implemented by a nonlinear element having a transfer function defined by contiguous linear transfer characteristic segments which collectively approximate the transfer function of Xe - K |X|, with the output of said nonlinear element comprising the input to said signal integrating means.
Claim 7
Dependent Claim
145 words
Signal development means as defined in claim 5 wherein said nonlinear element comprises first saturable operational amplifier means providing a linear output at predetermined gain to said signal integrator; means combining said first and second signals and the output of said integrator, as applied to the input of said first operational amplifier means, whereby the output from said first operational amplifier means comprises said signal X; the output of said first operational amplifier means being applied as input to each of second and third operational amplifiers having gains in excess of the gain of said first operational amplifier and respectively biased to produce linear outputs when the input thereto exceeds respective opposite polarity signal magnitudes; means for combining the outputs of each of said first, second and third operational amplifiers; and means applying said last defined signal combination as input to said signal integrating means.
Claim 8
Dependent Claim
56 words
Signal development means as defined in claim 6 wherein said first operational amplifier provides a saturated output at a level in excess of the signal level at which said second and third operational amplifiers are rendered conductive and exceeding that of the outputs of said second and third operational amplifiers in response to that signal level.
Claim 9
Dependent Claim
44 words
Signal development means as defined in claim 7 comprising signal gain changing means receiving the summation of the outputs from said first, second and third operational amplifiers, with the output of said gain changing means being applied as input to said signal integrating means.
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) | 1980-04-04 | 1980-10-04 | 1981-04-05 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-04-04 | 1984-10-04 | 1985-04-05 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-04-04 | 1988-10-04 | 1989-04-05 | $7700.00 | Window Closed / Lapsed |