Electricity: motive power systems – Positional servo systems – With particular 'error-detecting' means
Reexamination Certificate
1999-08-27
2001-02-20
Ip, Paul (Department: 2837)
Electricity: motive power systems
Positional servo systems
With particular 'error-detecting' means
C318S638000, C318S648000, C318S132000, C324S163000
Reexamination Certificate
active
06191550
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and apparatus for detecting an abnormality (abnormal condition) in a rotation sensor, which detects an abnormal condition of a signal processing circuit related to a resolver. More particularly, the invention relates to a method and apparatus for detecting an abnormality in a rotation sensor, adapted to detect an abnormality in a resolver in a control circuit for driving a motor of an electric vehicle.
2. Description of Related Art
For example, at the occasion of controlling the number of rotations of a motor for driving an electric vehicle, it is necessary to accurately rotate the vector of a current supplied to the driving motor in accordance with the rotations of the driving motor. In an electric vehicle, therefore, it is necessary to accurately detect the rotor position (angle) of the driving motor of the electric vehicle. In fields, including the above kind of field, where the position of a rotor should be accurately detected, a resolver is used as means for detecting the position (angle) of the rotor.
Even if an apparatus using the resolver is employed as an angle detecting apparatus, however, when an abnormality occurs in an output of a signal processing circuit which obtains the angle of the rotor from an output of the resolver, the angle cannot be reliably accurately detected. In an apparatus disclosed in Japanese Patent Application Laid-Open No. 9-72758, an abnormality in the signal processing circuit can be detected. Since an A/D converting process is used for the abnormality detection and the angle is estimated from the result of the A/D conversion, however, the detection accuracy is low. The threshold of the abnormality detection has to be accordingly increased, so that it can be considered that the reliability of the abnormality detection deteriorates. Since the construction including the A/D converting circuit has the large number of components, the failure rate of the abnormality detecting circuit itself may be also increased.
SUMMARY OF THE INVENTION
The invention has been realized to solve the problems and its object is to provide a method and apparatus capable of detecting an abnormality in an output of a signal processing circuit by making a signal processing system redundant, moreover, adapted to a control of a driving motor of an electric vehicle or the like.
In order to achieve the object, according to the invention, in a rotation sensor comprising a resolver attached to a rotor and a signal processing unit for angle detection for supplying a reference signal having a predetermined periodic waveform to the resolver, allowing the resolver to generate a sin signal having a waveform obtained by amplitude-modulating the reference signal by sin &thgr; when an angle of the rotor is &thgr; and a cos signal having a waveform obtained by amplitude-modulating the reference signal by cos&thgr;, and detecting the angle &thgr; on the basis of the sin signal and the cos signal, there are provided a signal processing unit for rotation detection which outputs a rotation pulse signal and a reference position signal on the basis of the angle &thgr;, and a signal process abnormality detecting unit for detecting the presence or absence of an abnormality in the signal processing unit for angle detection on the basis of the angle &thgr; and an angle &thgr;′ calculated from both of the rotation pulse signal and the reference position signal of the signal processing unit for rotation detection.
According to the invention, the angle signal processing unit detects the angle &thgr; on the basis of the sin signal and the cos signal. The rotation signal processing unit outputs the rotation signal pulse and the reference position signal pulse on the basis of the angle &thgr;. When a significant difference occurs between the angle &thgr; detected by the signal processing unit for angle detection and the angle &thgr;′ calculated on the basis of signals from the signal processing unit for rotation detection, the abnormality detecting unit can regard that an abnormality occurs in an output of the signal processing circuit. In the invention, since the difference between detection results of the signal processing units is used, an abnormality in the signal processing unit for angle detection or the signal processing unit for rotation detection can be accurately detected. Since the apparatus can be constructed by a simple digital circuit without using an A/D converting circuit, the number of components is small and the reliability can be enhanced.
According to another feature of the invention, in a rotation sensor abnormality detecting apparatus comprising a resolver for generating a signal in accordance with the angle of a rotor, an R/D converter for outputting a rotation signal and an electrical angle signal &thgr; on the basis of an output signal of the resolver, and a detecting unit for detecting an abnormality in an output of the R/D converter, an output signal of the resolver is connected to first and second R/D converters in parallel, a rotation signal N of the first R/D converter and an electrical angle signal &thgr; of the second R/D converter are connected to the detecting means, and the presence or absence of an abnormality in the resolver is detected from the relation between the rotation signal N of the first R/D converter and the electrical angle signal &thgr; of the second R/D converter.
According to further another feature of the invention, with respect to the two R/D converters, a rotation signal N
1
of the first R/D converter and an electrical angle signal &thgr;2 of the second R/D converter with respect to two R/D converters are used. Even when an R/D converter is failed, the rotation signal N and the angle signal &thgr; are synchronized, and an abnormal signal is generated, an abnormal condition can be therefore detected. Since comparison can be made by using digital data without performing A/D conversion, there are advantages that the decision level can be made low and an abnormal condition can be certainly detected.
REFERENCES:
patent: 4011440 (1977-03-01), Steglich
patent: 4963800 (1990-10-01), Kajiwara et al.
patent: 5075870 (1991-12-01), Kojyo et al.
patent: 5260650 (1993-11-01), Schwesig et al.
patent: 5691611 (1997-11-01), Kojima et al.
patent: 5796357 (1998-08-01), Kushihara
patent: 9-72758 (1997-03-01), None
Evenson, McKeown, Edwards & Lenahan P.L.L.C.
Hitachi , Ltd.
Ip Paul
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