Speed signal variance detection fault system and method

Details Speed signal variance detection fault system and method Speed signal variance detection fault system and method

2005-04-26

2005-04-26

Zanelli, Michael J. (Department: 3661)

Data processing: vehicles, navigation, and relative location

Vehicle control, guidance, operation, or indication

Vehicle diagnosis or maintenance indication

C701S100000, C702S146000

Reexamination Certificate

active

06885923

ABSTRACT:
A method and a system is provided, useable in electrical control sensors for shaft speed signal frequency change rate tests, detecting intermittent or “in-range”failures. The method estimates a short-term variance of the measured signal or signal rate of change, using the equation: Var[x]=E[x2]−E2[x], where E[x2] is an estimated average of the squared measured signal or rate of change over the short term, and E2[x] is a squared estimated average of the measured signal or rate of change over the short term. The estimated variance is compared with a predefined variance limit for a predefined amount of time, and if the estimated variance exceeds the predefined variance limit for the predefined amount of time, the measured signal is deemed invalid. A latching counter is used for timing, and its time out rate is preferably proportional to the time period the measured input is true. The step for estimating a short-term variance of the measured signal uses several filters performing averaging function.

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