Electricity: electrical systems and devices – Safety and protection of systems and devices – With specific quantity comparison means
Reexamination Certificate
1999-07-22
2001-03-20
Sherry, Michael J. (Department: 2836)
Electricity: electrical systems and devices
Safety and protection of systems and devices
With specific quantity comparison means
Reexamination Certificate
active
06205009
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to detecting faults in a resolver and in particular to a method and apparatus for detecting faults in a resolver based on the sum of the squared outputs of the resolver. Resolvers are position sensing devices having one excitation winding and two output windings, namely a sine winding and a cosine winding. Due to the physical relationship between the two output windings and the excitation winding, the voltage amplitude of the sine winding is proportional to the sine of the resolver angle and the voltage amplitude of the cosine winding is proportional to the cosine of the resolver angle. Because of the proportionality of the sine and cosine winding voltage amplitudes, the sum of the square of the sine voltage and the square of the cosine voltage should equal a constant.
Existing systems compare the sum of squared cosine and sine voltages to range limits in order to detect sensor faults. The high and low range limits were set wide enough to account for all worst case system variables. As a result, these limits would only detect extreme sensor faults (e.g., electrical opens or shorts). Small signal drifts (e.g., series resistance, resistance to ground, etc.), referred to as soft faults, could produce significant sensed position error but not be detected by the sum of squares range test.
BRIEF SUMMARY OF THE INVENTION
An exemplary embodiment of the invention is directed to a method for detecting fault in a resolver generating a sine voltage and a cosine voltage. The method includes obtaining a sum of a square of the sine voltage and a square of the cosine voltage. The sum is filtered through a first filter having a first time constant to generate a first filter output. The sum is also filtered through a second filter having a second time constant to generate a second filter output. The first filter output and second filter output are compared to detect a fault in the resolver.
REFERENCES:
patent: 3654516 (1972-04-01), Traversi
patent: 5910875 (1999-06-01), Tian et al.
Clark Aidan W.
Cook Kenneth F.
Kamath Deepak M.
Wittenbach Robert D.
Andes William Scott
General Electric Company
Hess Andrew C.
Sherry Michael J.
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