Data processing: measuring – calibrating – or testing – Calibration or correction system – Position measurement
Reexamination Certificate
2001-10-04
2003-09-02
Barlow, John (Department: 2863)
Data processing: measuring, calibrating, or testing
Calibration or correction system
Position measurement
C702S095000, C702S189000, C341S116000, C701S043000, C180S400000
Reexamination Certificate
active
06615152
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an abnormality detecting method and device for a position detecting device which is applicable for both a rotational position and a linear position such as a rotational position detector, for example a resolver or a synchro for detecting a position, or a linear position detector based on the similar detection principle, and an electric power steering device using such a device, and particularly, relates to judgment at the time of abnormality in the position detection of an electric power steering device for assisting a steering effort of a steering wheel by means for a motor, and a processing at that time.
2. Description of the Prior Art
Conventionally, in this kind of position detecting device, a resolver is used as a position detecting sensor, and two orthogonal winding output signals are inputted into a resolver digital converter (R/D converter), and the rotational position is detected. This position detecting device is utilized in the control of rotation of a motor.
FIG. 5
is a block diagram showing a position detecting device disclosed in, for example, Japanese Patent Laid-Open No. 9-72758.
In this drawing, a reference signal that is sine wave voltage for excitation is inputted into the position sensor
1
using a resolver from an oscillator circuit
22
. From the position sensor
1
, a reference signal is outputted as a signal amplitude-modulated by cos &thgr; and sin &thgr; according to the rotational position &thgr; thereof. Hereafter, an output signal amplitude-modulated by cos &thgr; is a cos signal and an output signal amplitude-modulated by sin &thgr; is a sin signal.
These two output signals are inputted into a position detector circuit
4
using an R/D converter, and from the position detector circuit
4
, the rotational position &thgr; is outputted as a digital signal. This digital signal of the rotational position &thgr; is inputted into a control CPU
5
, and is used for a predetermined control. In the case where a breaking of the wire is caused in the resolver used as the position sensor
1
, it becomes a cause of malfunction in various control mechanisms, and therefore, it is necessary to detect this breaking of the wire of the resolver without delay.
As this kind of conventionally used abnormality detecting method, in the above described Japanese Patent Laid-Open No. 9-72758 or the like, there is disclosed a method in which the amplitude-modulated signals (sin signal, cos signal) of two output parts of the position sensor
1
corresponding to the rotational position that are resolver signals are compared or operated in the control CPU
5
through the A/D converter circuits
23
,
24
apart from the position detector circuit
4
for detecting the position, and abnormality is judged in the case where a predetermined condition is not satisfied.
Furthermore, in Japanese Patent Laid-Open No. 2000-131096 shown in
FIG. 6
, a DC power source
12
is connected to one end of an output winding
3
of the position sensor
1
through a resistance
31
, and the other end of the output winding
3
is connected to the ground through a resistance
32
, and consequently, DC bias current
15
is applied to the cos signal or sin signal that is amplitude-modulated according to the rotational position, from the output winding
3
of the position sensor
1
. Then, signals
6
,
7
from the output winding
3
are inputted in a differential amplifier
10
through buffer circuits
8
,
9
, respectively and are amplified, and abnormality is judged when a signal with a voltage value higher than the maximum voltage value is outputted from the amplified signal.
BRIEF SUMMARY OF THE INVENTION
Object of the Invention
By the way, the conventional abnormality detecting methods disclosed in the above described specification have the following problems.
First, in the above described Japanese Patent Laid-Open No. 9-72758, the structure is made as mentioned above, and therefore, for example, as for the sin signal, it becomes of 0 V when the rotational position is of 0 degree since it is an amplitude-modulated signal, and the judgment cannot be made when the wiring is broken. Furthermore, it is impossible to detect a grounding or air discharge, and it is impossible to judge that it is abnormality.
Furthermore, in the case of the above described Japanese Patent Laid-Open No. 2000-131096, the normal time and abnormal time are judged by detecting the maximum value voltage of the amplified signal from the amplitude-modified signal, and therefore, a circuit for dividing the normal time and the abnormal time by a wind comparator or the like is necessary. Furthermore, it is necessary to input the signal from the output winding
3
of the position sensor
1
to the differential amplifier
10
through the buffer circuits
8
,
9
. Therefore, there is a tendency of enlarging the circuit scale for detecting the breaking of the wire, which is expensive.
Furthermore, noise is easily generated since the passage of the output winding
3
is usually long, and a resistance
33
is usually arranged between the output parts as shown in
FIG. 7
, and it is the ordinary course that the high frequency component noise is eliminated by controlling the impedance. However, in the case of the circuit structure of
FIG. 6
, it is difficult to detect the breaking of the wire because of the bias resistance, that is, the resistances
31
,
32
when the above described resistance
33
is arranged between the output parts, and accordingly, the resistance
33
cannot be arranged, and therefore, it is impossible to eliminate the noise.
This invention is made for solving such problems, and it is an object to provide an abnormality detecting method and a device of a position detecting device in which DC bias is applied to the output winding of the position sensor, and the abnormality such as the breaking of the output winding is surely detected, and in the meantime, the DC bias and the reduction of noise in the position detecting can coexist, and the cost is low and the structure is simple, and an electric power steering device.
SUMMARY OF THE INVENTION
The abnormality detecting method of a position detecting device according to the invention of claim 1 is an abnormality detecting method of a position detecting device which generates an amplitude-modulated or phase-modulated signal from a position sensor according to a rotational position of a rotor when a reference signal having a predetermined periodic waveform is supplied, and the method comprises: a step of applying DC bias current to an output winding of the above described position sensor; a step of detecting a biased DC signal of an amplitude-modulated or phase-modulated signal applied to the above described output winding, apart from signal processing for detecting a rotational position of the above described rotor; and a step of judging abnormality of the above described position detecting device from the above described detected DC signal.
According to this configuration, there is such an effect that abnormality of the position detecting device can surely be detected regardless of the rotational position of a rotor, and furthermore, simplification of the circuit structure and reduction of the cost can be attained.
The abnormality detecting method of a position detecting device according to the invention of claim 2 is a method, in which the above described step of detecting the DC signal includes a step of eliminating an amplitude-modulated component or a phase-modulated component produced by noise and a reference signal.
According to this configuration, there is such an effect that abnormality of the position detecting device can surely be detected without being affected by noise coming from the outside or the like.
The abnormality detecting method of a position detecting device according to the invention of claim 3 is a method further comprising a step of judging abnormality of the above described position detecting device from a DC signal depending on only the above described DC bi
Fujimoto Chiaki
Fukushima Yukio
Barlow John
Mitsubishi Denki & Kabushiki Kaisha
Vo Hien
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