Fault-tolerant system, apparatus and method
First Claim
1. A method of integrity maintenance in an estimating processor including at least one system state having an estimable value, at least one dynamic system model responsive to changes in the at least one system state and receptive to one or more external inputs, a measurement model comprising at least one measurement having information pertaining to the at least one system state, and at least one hypothesized fault model, wherein the at least one hypothesized fault model describes a direction in which a fault may act on any of the at least one system state, the method comprising the steps of:
- (a) determining a residual by differencing the at least one system state and the at least one measurement;
(b) projecting at least one hypothesized fault model;
(c) determining a fault-free residual by applying the at least one projected hypothesized fault to the determined residual;
(d) determining a probabilistic estimate of fault occurrence using the at least one projected hypothesized fault model and the at least one measurement based on results of or one or more residual testing wherein the one or more residual tests are selected from the group consisting of;
Multiple Hypothesis Wald Sequential Probability Ratio residual testing, Multiple Hypothesis Shiryayev Sequential Probability Ratio residual testing and Chi-Square Test residual testing;
(e) updating a filter gain;
(f) updating the at least one system state with a product of the updated filter gain and the determined residual of step (a);
(g) determining fault occurrence based on the determined probabilistic estimate; and
(h) predicting a next at least one system state using the updated at least one system state and the at least one dynamic system model and (i) updating and predicting the at least one fault direction using the at least one dynamic system model.
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Abstract
A method, apparatus and system are described having a minimum variance estimator of state estimates typically in navigation embodiments where a sensor and/or effecter fault detecting module is adapted to execute residual testing steps using the Multiple Hypothesis Wald Sequential Probability Ratio test, the Multiple Hypothesis Shiryayev Sequential Probability Ratio test, the Chi-Square test and combinations thereof to determine the likelihood of sensor and/or actuator fault occurrences and thereafter isolate the effects of the one or more identified fault from the state estimates.
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Citations
24 Claims
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1. A method of integrity maintenance in an estimating processor including at least one system state having an estimable value, at least one dynamic system model responsive to changes in the at least one system state and receptive to one or more external inputs, a measurement model comprising at least one measurement having information pertaining to the at least one system state, and at least one hypothesized fault model, wherein the at least one hypothesized fault model describes a direction in which a fault may act on any of the at least one system state, the method comprising the steps of:
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(a) determining a residual by differencing the at least one system state and the at least one measurement;
(b) projecting at least one hypothesized fault model;
(c) determining a fault-free residual by applying the at least one projected hypothesized fault to the determined residual;
(d) determining a probabilistic estimate of fault occurrence using the at least one projected hypothesized fault model and the at least one measurement based on results of or one or more residual testing wherein the one or more residual tests are selected from the group consisting of;
Multiple Hypothesis Wald Sequential Probability Ratio residual testing, Multiple Hypothesis Shiryayev Sequential Probability Ratio residual testing and Chi-Square Test residual testing;
(e) updating a filter gain;
(f) updating the at least one system state with a product of the updated filter gain and the determined residual of step (a);
(g) determining fault occurrence based on the determined probabilistic estimate; and
(h) predicting a next at least one system state using the updated at least one system state and the at least one dynamic system model and (i) updating and predicting the at least one fault direction using the at least one dynamic system model. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A system for performing fault tolerant navigation comprising:
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a global positioning satellite receiving device providing at least three position outputs, or pseudorange measurements, and an associated time output;
a processor for providing a plurality of state estimates by taking in the pseudorange measurements and associated time output wherein the processor comprises;
a minimum variance estimator of state estimates;
a sensor fault detecting module adapted to execute residual testing steps based on one or more testing steps selected from the group consisting of;
Multiple Hypothesis Wald Sequential Probability Ratio residual testing, Multiple Hypothesis Shiryayev Sequential Probability Ratio residual testing and the Chi-Square Test residual testing; and
a sensor fault annihilator module adapted to estimate a fault time history and remove the estimated fault time history from the state estimates. - View Dependent Claims (10, 11, 12)
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13. A system for autonomous relative navigation comprising:
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(a) a target element, comprising;
(i) at least one target element global positioning system antenna;
(ii) at least one target element global positioning system receiver operably coupled to the at least one target element global positioning system antenna;
(iii) a target element processor for deriving a position, velocity, attitude solution for the target element; and
(iv) a transmitter for transmitting the derived target position, velocity, attitude solution as well as global positioning system measurements from any of the at least one global positioning system receivers; and
(b) a seeker element comprising;
(i) at least one seeker element global positioning system antenna;
(ii) at least one seeker element global positioning system receiver operably coupled to the at least one seeker global positioning system antenna; and
(iii) a receiver for receiving the transmitted derived target position, velocity, attitude solution and global positioning system measurements; and
(iv) a seeker element processor for deriving a seeker-relative position, velocity, attitude solution for the target element;
wherein the target element processor and seeker element processor each comprise;
a minimum variance estimator of state estimates;
a sensor fault detecting module adapted to execute residual testing steps based on one or more testing steps selected from the group consisting of;
Multiple Hypothesis Wald Sequential Probability Ratio residual testing, Multiple Hypothesis Shiryayev Sequential Probability Ratio residual testing and the Chi-Square Test residual testing; and
a sensor fault annihilator module adapted to estimate a fault time history and remove the estimated fault time history from the state estimates. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20, 21, 22, 23)
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24. An apparatus for maintaining state estimation integrity, the apparatus including at least one system state having an estimable value, at least one dynamic system model responsive to changes in the at least one system state and receptive to one or more external inputs;
- a measurement model comprising at least one measurement having information pertaining to the at least one system state, and at least one hypothesized fault model, wherein the at least one hypothesized fault model describes a direction in which a fault may act on any of the at least one system state, the apparatus further comprising;
means for determining a residual by differencing the at least one system state and the at least one measurement;
means for projecting at least one hypothesized fault model;
means for updating a filter gain;
means for updating the at least one system state with a product of the updated filter gain and the determined residual;
means for determining the residual by differencing the at least one updated system state and the at least one measurement;
means for determining a fault-free residual by applying the at least one projected hypothesized fault to update the determined residual;
means for determining a probabilistic estimate of fault occurrence using the projected at least one hypothesized fault model and the at least one measurement;
means for determining fault occurrence based on the determined probabilistic estimate;
means for predicting a next at least one system state using the updated at least one system state and the at least one dynamic system model; and
means for updating and predicting the at least one fault direction using the at least one dynamic system model.
- a measurement model comprising at least one measurement having information pertaining to the at least one system state, and at least one hypothesized fault model, wherein the at least one hypothesized fault model describes a direction in which a fault may act on any of the at least one system state, the apparatus further comprising;
Specification