EP0511730A2
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EP
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Fault-tolerant inertial navigation system
Assignee: Northrop Grumman Guidance and Electronics Co Inc
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Filing: 1992-02-12
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Granted: —
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Expires: 2012-02-12
Abstract
Abstract Disclosed herein is a Fault-Tolerant Inertial Navigation System (70) comprising, in a preferred embodiment, a Redundant Set of at least two Inertial Navigation Systems (101, 102) from which one may identify and isolate at least one instrument within an Inertial Navigation Unit which shows substantial performance degradation. The two inertial navigation units are fully capable of performing navigational functions. Each of these inertial navigation units has a plurality of navigational instruments, including at least three linear sensors (such as accelerometers) (38) and three angular change sensors (such as gyroscopes or ring laser gyroscopes) (32, 34, 36). No two linear sensors nor any two angular change sensors of either unit are aligned collinearly. Each of the inertial navigation units produces a set of independent navigational solutions (X₁, X₂) at each of their respective outputs. The independent navigational solutions of each of the navigation units are compared and any significantly degraded performance of any one linear sensor or any one angular change sensors is detected.
Inventors
- 👤 James R. Huddle
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-06 18:14
CPC Classifications
G; G01; G01C; G01C21/00; G01C21/10; G01C21/12; G01C21/16; G01C21/183; G01C21/188; G01C25/00; G01C25/005
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
158 words
A fault-tolerant inertial navigation system (70), comprising a plurality of independent inertial navigation units, each of said inertial navigation units (101, 102) being fully capable of performing navigational functions, and each of said inertial navigation units comprising a plurality of navigational instruments including at least three linear force sensors (38) and three angular change sensors (32, 34, 36), characterised in that there are two said navigational units with no two linear sensors nor two angular change sensors of either unit being co-linear or co-planar, each of said inertial navigation units being operable to produce a set of independent navigational solutions (X₁, X₂) at each of their respective outputs, there being means (100) for comparing said independent navigational solutions of each of said navigation units and for detecting any significantly degraded performance of any one linear sensor or any one angular change sensor whereby, one of such sensors indicating such degraded performance is isolated and identified as being faulty.
Claim 2
Dependent Claim
153 words
The fault-tolerant inertial navigation system of claim 1, wherein said means for comparing (100) said independent navigational solutions of each of said navigation units and for detecting any significantly degraded sensor performance is capable of detecting significantly degraded performance of any one sensor of a first type of instrument and significantly degraded performance of any one sensor of a second type of instrument, there being means for identifying the type of a first of such sensors exhibiting such significantly degraded performance and, said identifying means capable of further identifying the type of a second of such sensors exhibiting such significantly degraded performance, provided such second sensor is a different type than said first sensor; whereby, a first of such sensors indicating such degraded performance is isolated and identified as to being faulty, and a second of such sensors, of a different type than the first of such sensors so identified, is also identified.
Claim 3
Dependent Claim
79 words
The fault-tolerant inertial navigation system (70) according to claim 1 or 2 wherein said means (100) for comparing said independent navigational solutions includes an optimal estimation Kalman filter (78, 80) operating according to a Kalman algorithm which processes differences in the compared computed navigational solutions, and said algorithm includes in its error states the errors in computed navigation variables, such as position, velocity, and orientation, and said Kalman algorithm further includes appropriate error states for the inertial instrument errors.
Claim 4
Dependent Claim
64 words
The fault-tolerant inertial navigation system of claim 3, wherein said Kalman filter algorithm of said comparing means (100) includes performance factors such as individual angular change sensors and linear force sensor biases, scale factor errors, mounting misalignments of said angular change and linear force sensors within each of said navigation units, with respect to one other, and mechanical misalignments between the two navigation units.
Claim 5
Dependent Claim
69 words
The fault-tolerant inertial navigation system according to claim 1 or 2 wherein said means (100) for comparing said independent navigational solutions includes a least squares estimation algorithm which processes differences in these compared computed navigational solutions, and said algorithm includes in its error states the errors in computed navigation variables, such as position, velocity, and orientation and said algorithm further includes appropriate error states for the inertial instrument errors.
Claim 6
Dependent Claim
177 words
The fault-tolerant inertial navigation system according to any one of the preceding claims, wherein said means (100) for comparing said independent navigational solutions includes: means (126, 128) for computing a set of error state estimate values, said error state estimate values being computed for navigation variables, such as position, velocity and orientation, said error state estimate values forming sub-vectors ê s1 and ê s2 of the error estimate vectors ê₁ and ê₂; means (111, 113, 123, 125) for combining said set of said independent navigational solutions, which solutions are provided at each of the respective outputs of said inertial navigation units (101, 102), with said computed error state estimate values; means for determining corrections in said error state estimate values as a function of the error in the estimated values of the independent navigational solutions from both of said inertial navigation units; and means for updating said error state estimate values with said corrections whereby estimated navigational solutions approach the true navigational solutions for each navigational unit so that fault detection of navigational instruments may be achieved.
Claim 7
Dependent Claim
130 words
The fault-tolerant inertial navigation system according to any one of claims 1 to 5, wherein said means for comparing said independent navigational solutions includes: means (126, 128) for computing two sets of error state estimate values, respective sets comprising estimates associated with error state variables such as errors in position, velocity and orientation, for each of said navigational units; means for determining corrections in said error state estimate values, wherein a function of the error state vector estimates for each of said inertial navigation units is obtained without having an effect on the other separately; and means for updating said error state estimate values with said corrections whereby estimated navigational solutions approach the true navigational solutions for each navigational unit so that fault detection of navigational instruments may be achieved.
References Cited (Backward Citations)
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