Intermittent failure diagnostic system and electric power steering apparatus provided with the same

Patent metadata

Field	Value
Publication number	US-2016264173-A1
Application number	US-201415036492-A
Country	US
Kind code	A1
Filing date	Nov 13, 2014
Priority date	Nov 22, 2013
Publication date	Sep 15, 2016
Grant date	—

Abstract

An intermittent failure diagnostic system that, in addition to a failure detection of a conventional failure threshold, sets an intermittent diagnostic threshold inside of the failure threshold or sets the intermittent diagnostic threshold in an arbitrary scope with a detection resolving-power unit, securely detects the intermittent failure in a wide region by using a statistics way, suppresses an unprepared system down and improves the reliability and to an electric power steering apparatus provided with the same.

First claim

1 - 9 . (canceled)

10 . An intermittent failure diagnostic system comprising a fail-counter to failure-settle 1 on an ordinary diagnosis by calculating a normal distribution based on a mean value and a standard deviation of measured values at a normal state of an electrical apparatus, by setting at least one failure threshold as a diagnostic threshold of said measured values, and by measuring a number or a time of said measured values exceeding said failure threshold:
wherein said intermittent failure diagnostic system sets an intermittent failure diagnostic threshold for an intermittent failure diagnosis between said mean value and said failure threshold, and said fail-counter measures a number or a time that said measured values exceed said intermittent failure diagnostic threshold; and wherein said intermittent failure diagnostic system sets a counting value or a time to failure-settle 2 on said fail-counter so as to coincide a permissible value on a false-failure probability of said ordinary diagnosis with a permissible value on a false-failure probability of said intermittent failure diagnosis, wherein assuming that a counting value of said fail-counter to failure-settle 1 on said ordinary diagnosis is n, a counting value of said fail-counter to failure-settle 2 is N, a permissible value on a false-failure probability of said ordinary diagnosis is P F n and a permissible value on a false-failure probability of said intermittent failure diagnosis is P T N , a relation
N =( n *log P F )/(log P T )

is established.

11 . The intermittent failure diagnostic system according to claim 10 , wherein said failure threshold is set based on a physical requirement 1.

12 . The intermittent failure diagnostic system according to claim 11 , wherein said physical requirement 1 is a hard ware characteristic or a system usage condition.

13 . The intermittent failure diagnostic system according to claim 10 , wherein said counting value or said time to failure-settle 2 is set based on a physical requirement 2.

14 . The intermittent failure diagnostic system according to claim 13 , wherein said physical requirement 2 is at least one of a hard ware characteristic, a system usage condition, a supposing impulse-noise width and a continuous permissible time on a functional safety.

15 . The intermittent failure diagnostic system according to claim 10 , wherein said failure thresholds are set at an upper-limit side and a lower-limit side, and at least one of said intermittent failure diagnostic threshold is set between said failure thresholds and said mean-value.

16 . The intermittent failure diagnostic system according to claim 10 , wherein said failure counting is continuously or discontinuously performed.

17 . The intermittent failure diagnostic system according to claim 10 , wherein said intermittent failure diagnostic threshold is shifted to a whole region of diagnostic values by a detection resolving-power unit and is set.

18 . An electric power steering apparatus is provided with the intermittent failure diagnostic system claimed in claim 10 .

Assignees

• Nsk Ltd

Inventors

• Goto Hiroki

Classifications

• G05B23/0235

  based on a comparison with predetermined threshold or range, e.g. "classical methods", carried out during normal operation; threshold adaptation or choice; when or how to compare with the threshold · CPC title

• G05B23/0275

  Fault isolation and identification, e.g. classify fault; estimate cause or root of failure · CPC title

• B62D5/0481 Primary

  monitoring the steering system, e.g. failures · CPC title