Model-based fault detection and isolation for intermittently active faults with application to motion-based thruster fault detection and isolation for spacecraft
First Claim
1. A method for detecting and isolating intermittently observable fault modes in a system having models describing its behavior and one or more measurements that are sampled regularly, said method comprising:
- (a) said models and computing capacity to calculate past and present measurements that would result from said system with no faults, as well as from said system with one or more potential fault mode candidates;
(b) algorithms to calculate and store deviations between said calculated measurements and either actual measurements or an abstraction of said actual measurements as returned by a filtering function;
(c) detection algorithms using said calculated deviations at times or states comprising present and historical data to declare when one of said fault mode candidates or anomalies in the data un-related to said fault modes becomes possible;
(d) exoneration algorithms using said calculated deviations to remove certain fault mode candidates from consideration as a potential fault mode, thereby making the decision making in the final step simpler and more robust; and
(e) isolation algorithms using said calculated deviations to declare which one of remaining said potential fault mode candidates is the true fault mode.
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Abstract
The present invention is a method for detecting and isolating fault modes in a system having a model describing its behavior and regularly sampled measurements. The models are used to calculate past and present deviations from measurements that would result with no faults present, as well as with one or more potential fault modes present. Algorithms that calculate and store these deviations, along with memory of when said faults, if present, would have an effect on the said actual measurements, are used to detect when a fault is present. Related algorithms are used to exonerate false fault modes and finally to isolate the true fault mode. This invention is presented with application to detection and isolation of thruster faults for a thruster-controlled spacecraft. As a supporting aspect of the invention, a novel, effective, and efficient filtering method for estimating the derivative of a noisy signal is presented.
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Citations
11 Claims
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1. A method for detecting and isolating intermittently observable fault modes in a system having models describing its behavior and one or more measurements that are sampled regularly, said method comprising:
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(a) said models and computing capacity to calculate past and present measurements that would result from said system with no faults, as well as from said system with one or more potential fault mode candidates; (b) algorithms to calculate and store deviations between said calculated measurements and either actual measurements or an abstraction of said actual measurements as returned by a filtering function; (c) detection algorithms using said calculated deviations at times or states comprising present and historical data to declare when one of said fault mode candidates or anomalies in the data un-related to said fault modes becomes possible; (d) exoneration algorithms using said calculated deviations to remove certain fault mode candidates from consideration as a potential fault mode, thereby making the decision making in the final step simpler and more robust; and (e) isolation algorithms using said calculated deviations to declare which one of remaining said potential fault mode candidates is the true fault mode. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
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Specification