Data processing: measuring – calibrating – or testing – Measurement system in a specific environment – Mechanical measurement system
Reexamination Certificate
2001-09-26
2003-06-10
Barlow, John (Department: 2863)
Data processing: measuring, calibrating, or testing
Measurement system in a specific environment
Mechanical measurement system
C702S072000, C702S189000, C701S041000, C701S043000, C318S661000, C318S254100
Reexamination Certificate
active
06577957
ABSTRACT:
This application is based on Application No. 2001-115250, filed in Japan on Apr. 13, 2001, the contents of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an abnormality detecting apparatus and method for detecting abnormality in a position detection device, which is applicable for both rotational position detection and linear position detection, including a rotational position detector such as a position detecting resolver, a position detecting synchronizer, etc., and a linear position detector utilizing position detection principles similar to those for rotational position detection. More specifically, it relates to abnormality determination and processing in such a position detection device in an electrically operated or motorized power steering system for assisting an operator's steering effort exerted on a steering wheel by means of an electric motor.
2. Description of the Related Art
In the past, a resolver, a typical one of such kinds of position detectors, has been employed for rotational position detection in which output signals from two orthogonally arranged winding members are input to a resolver digital converter (hereinafter simply referred to as R/D converter). By the use of this position detection device, a motor for a motorized power steering system is controlled to rotate.
An example of such a resolver is illustrated in FIG.
11
. In
FIG. 11
, the resolver
10
has a single primary winding member to which an excitation signal (sin &ohgr;t)
14
, which is a sine wave voltage for excitation of the resolver, is input from an oscillation circuit
12
. The resolver
10
also has two secondary winding members arranged in a mutually orthogonal relation with respect to each other to output induction signals
16
,
18
, which are generated, for example, by amplitude modulating the excitation signal
14
with cos &thgr; and sin &thgr;, respectively, in accordance with the rotational position &thgr; of the motor of the motorized power steering system. Hereinafter, the output signal of the secondary winding members generated through amplitude modulation with cos &thgr; is referred to as a cos signal
16
, and the output signal of the secondary windings generated by amplitude modulation with sin &thgr; is referred to as a sin signal
18
. These two output signals
16
and
18
are input to the R/D converter
20
which then generates a digital signal representative of the detected rotational position &thgr;. The digital signal of this rotational position &thgr; is input to a control section
22
for use in the prescribed control.
When there takes place a break in the resolver, there might be caused malfunctions of various control mechanisms, and hence such a break has to be detected promptly. To detect abnormality in the resolver, there has conventionally been implemented a method of individually detecting the excitation signal
14
, the cos signal
16
and the sin signal
18
, respectively. In addition, another method of simultaneously detecting breaks in signal lines for these three signals has also been proposed. This method is advantageous in that simultaneous detection of breaks in the three lines serves to reduce the number of component elements and provide inexpensive broken-line detection as compared with the aforementioned individual broken-line detection method. An exemplary method of simultaneously detecting breaks in three lines is disclosed, for instance, in Japanese Patent Application Laid-Open No. 3-78668.
FIG. 12
illustrates the construction of a conventional position detecting apparatus for simultaneous detection of breaks in three lines. In
FIG. 12
, two excitation signals supplied to a resolver
102
from an oscillation circuit
100
are gain adjusted into signals Vsin &ohgr; by means of an amplifier
104
, which are then input to a full-wave rectifier circuit
106
wherein they are full-wave rectified into a DC voltage. The output signal of the full-wave rectifier circuit
106
is input to a comparator or comparison circuit
108
. Also, a sin signal
18
output from the resolver
102
is gain adjusted into a signal Vsin &thgr; sin &ohgr;t by means of an amplifier
110
, which is then input to a phase shift circuit
112
where the signal Vsin &thgr; sin &ohgr;t is phase-shifted, by phase-shifting sin &ohgr;t, into a signal Vsin &thgr; cos &ohgr;t which is in turn output therefrom to an addition circuit
114
.
On the other hand, a cos signal
16
output from the resolver
102
is gain adjusted into a signal Vcos &thgr; sin &ohgr;t by means of an amplifier
116
, which is then input to the addition circuit
114
. In the addition circuit
114
, the signals Vsin &thgr; cos &ohgr;t and Vcos &thgr; sin &ohgr;t are summed to provide a combined signal Vsin(&ohgr;t+&thgr;) as its output. Since this signal Vsin(&ohgr;t+&thgr;) shifts by a phase &thgr; from the excitation signal Vsin &ohgr;t, when full-wave rectified into a DC voltage by means of a full-wave rectifier
118
, it provides the same DC signal as the output of the full-wave rectifier circuit
106
. Then, the output of the full-wave rectifier
118
is also input to the comparison circuit
108
, where the output voltage of the full-wave rectifier circuit
106
and the output voltage of the full-wave rectifier circuit
118
are compared with each other for determination of a break in the resolver
102
. When a break is generated in the resolver
102
, the output DC voltages from the two full-wave rectifier circuits
106
,
118
become unequal whereby the break of the resolver
102
can be detected.
In the conventional abnormality detection apparatus for the position detection device as constructed above, the full-wave rectifier circuits each of a complicated construction are needed, thereby increasing the number of component elements and hence the cost of manufacture as well. Moreover, for example, in the event that the resolver is rotating with the signal line for the sin signal being broken, it is determined that the resolver is normal at a rotational position or angle of 0 or 180 degrees, and abnormal at all the other rotational positions or angles. Therefore, determinations of normality and abnormality are repeated, thus making it impossible to definitely determine the abnormality of the resolver.
SUMMARY OF THE INVENTION
The present invention is intended to obviate the above-mentioned problems, and has for its object to provide an abnormality detecting apparatus and method for a position detection device which is capable of performing abnormality detection with improved accuracy at low costs by detecting abnormality based on a peak value of a phase-modulated signal obtained corresponding to the rotational position of a rotating element such as a motor, the rotational position of which is to be detected.
Bearing the above object in mind, according to one aspect of the present invention, the invention resides in an abnormality detection apparatus for a position detection device in which at least one excitation signal having a predetermined periodic waveform is supplied to primary winding of a position detection sensor to thereby generate at least one output signal in the form of a phase modulated signal corresponding to a rotational position of a rotating member from secondary winding of the position detection sensor directly or after having been subjected to phase shifting and arithmetic operations, said apparatus comprising an abnormality detection section for determining an abnormality of said position detection device when said phase modulated signal has a peak value which is outside a predetermined range.
In a preferred form of the present invention, the abnormality detection section comprises: a peak hold circuit for detecting a peak value of said phase modulated signal and holding it for a predetermined period of time; and an abnormality detection determination processing section for determining abnormality when the peak hold value of said peak hold circuit is outside a predetermined range.
In a
Fujimoto Chiaki
Fukushima Yukio
Barlow John
Mitsubishi Denki & Kabushiki Kaisha
Vo Hien
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