Intermittent failure diagnostic system and electric power steering apparatus provided with the same
First Claim
1. An intermittent failure diagnostic detection system for detecting failures in at least one electrical apparatus, said intermittent failure diagnosis detection system comprising a fail-counter to detect a first failure for an ordinary diagnosis by calculating a normal distribution based on a mean value and a standard deviation of measured values of an output normal state voltage of said at least one electrical apparatus, by setting at least one output voltage failure threshold as a diagnostic threshold of measured output voltage values of said at least one electrical apparatus, and by measuring a number or a time of said measured output voltage values of said at least one electrical apparatus exceeding said output voltage failure threshold:
- wherein said intermittent failure diagnostic detection system sets an intermittent output voltage failure diagnostic threshold for an intermittent failure diagnosis between said mean value of an output normal state voltage and said output voltage failure threshold, and said fail-counter measures a number or a time that measured output voltage values of said at least one electrical apparatus exceed said intermittent output voltage failure diagnostic threshold;
wherein said intermittent failure diagnostic system sets a counting value or a time to detect a second failure for an intermittent failure diagnosis, that satisfies the relationship
N=(n*log PF)/(log PT)where a counting value of said fail-counter to detect said first failure for said ordinary diagnosis is n, a counting value of said fail-counter to detect said second failure for said intermittent failure diagnosis is N, a permissible value on a false-failure probability of said ordinary diagnosis is PFn and a permissible value on a false-failure probability of said intermittent failure diagnosis is PTN, so as to coincide said permissible value on said false-failure probability of said ordinary diagnosis with said permissible value on said false-failure probability of said intermittent failure diagnosis;
wherein said intermittent failure diagnostic system detects an occurrence of an intermittent failure when said counting value of said fail-counter to detect said second failure for said intermittent failure diagnosis is said counting;
wherein the electrical apparatus comprises an electric power steering apparatus; and
wherein the detection of said first failure for an ordinary diagnosis and said detection of said second failure for an intermittent diagnosis are outputted to a display.
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Accused Products
Abstract
An intermittent failure diagnostic system that, in addition to a failure detection of a conventional failure threshold, appropriately sets an intermittent diagnostic threshold at which a probability of false-positive detection of the intermittent failure is equal to a probability of false-positive detection of the conventional failure, more accurately detects the intermittent failure, suppresses an unprepared system down and improves the reliability, may be used with an electric power steering apparatus.
14 Citations
8 Claims
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1. An intermittent failure diagnostic detection system for detecting failures in at least one electrical apparatus, said intermittent failure diagnosis detection system comprising a fail-counter to detect a first failure for an ordinary diagnosis by calculating a normal distribution based on a mean value and a standard deviation of measured values of an output normal state voltage of said at least one electrical apparatus, by setting at least one output voltage failure threshold as a diagnostic threshold of measured output voltage values of said at least one electrical apparatus, and by measuring a number or a time of said measured output voltage values of said at least one electrical apparatus exceeding said output voltage failure threshold:
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wherein said intermittent failure diagnostic detection system sets an intermittent output voltage failure diagnostic threshold for an intermittent failure diagnosis between said mean value of an output normal state voltage and said output voltage failure threshold, and said fail-counter measures a number or a time that measured output voltage values of said at least one electrical apparatus exceed said intermittent output voltage failure diagnostic threshold; wherein said intermittent failure diagnostic system sets a counting value or a time to detect a second failure for an intermittent failure diagnosis, that satisfies the relationship
N=(n*log PF)/(log PT)where a counting value of said fail-counter to detect said first failure for said ordinary diagnosis is n, a counting value of said fail-counter to detect said second failure for said intermittent failure diagnosis is N, a permissible value on a false-failure probability of said ordinary diagnosis is PFn and a permissible value on a false-failure probability of said intermittent failure diagnosis is PTN, so as to coincide said permissible value on said false-failure probability of said ordinary diagnosis with said permissible value on said false-failure probability of said intermittent failure diagnosis; wherein said intermittent failure diagnostic system detects an occurrence of an intermittent failure when said counting value of said fail-counter to detect said second failure for said intermittent failure diagnosis is said counting; wherein the electrical apparatus comprises an electric power steering apparatus; and wherein the detection of said first failure for an ordinary diagnosis and said detection of said second failure for an intermittent diagnosis are outputted to a display. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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Specification