Resolver abnormality detection apparatus

This application claims priority to Japanese Patent Application No. 2015-32673 filed on Feb. 23, 2015, the entire contents of which are hereby incorporated by reference.

1. Field of the Invention

The present invention relates to a resolver abnormality detection apparatus for detecting an abnormality such as a wire breakage or a sky fault (a short circuit to power supply) in a resolver.

2. Description of Related Art

Japanese Patent Application Laid-open No. 2000-166205 describes an interphase short-circuit detection apparatus for a resolver, the apparatus including a DC power supply connected to the cosine phase of the secondary winding of the resolver, a comparator for comparing a DC voltage relative to ground of the sine phase of the secondary winding of the resolver with a threshold value, and a comparator for comparing a DC voltage relative to ground of the cosine phase of the secondary winding of the resolver with a threshold value. This interphase short-circuit detection apparatus can detect an interphase short circuit in the secondary winding, and a short circuit between the primary winding and the secondary winding based on the outputs of the two comparators.

This interphase short-circuit detection apparatus can detect also a sky fault and a ground fault (a short circuit to ground) in the secondary winding. However, in this interphase short-circuit detection apparatus, there is a limit to the rotational angle θ of the rotor of a resolver in detecting a wire breakage in the secondary winding. For example, in a case where a wire breakage is determined to be present in the resolver when the equation of sin (θ)^2+cos (θ)^2=1 does not hold, if there occurs a wire breakage in the sine phase when the rotational angle θ of the rotor is 0 degrees, it cannot be detected, because this equation still holds. Accordingly, this interphase short-circuit detection apparatus has a problem in that when a wire breakage occurs while the rotor is stationary at a specific angle position, the wire breakage may not be detected.

An exemplary embodiment provides a resolver abnormality detection apparatus for a resolver having a first secondary winding and a second secondary winding which constitute different phases, resolver abnormality detection apparatus including:

a first resistor section including a first pull-up resistor for pulling up the first secondary winding, a first pull-down resistor for pulling down the first secondary winding and a first DC power supply connected to the first pull-up resistor;

a second resistor section including a second pull-up resistor for pulling up the second secondary winding, a second pull-down resistor for pulling down the second secondary winding and a second DC power supply connected to the second pull-up resistor;

a first differential input section connected across the first secondary winding; and

a second differential input section connected across the second secondary winding;

the resolver abnormality detection apparatus detecting presence of an abnormality in each of the first and second secondary windings based on outputs of the first and second differential input sections, a first voltage as a DC voltage between the first resistor section and the first differential input section and a second voltage as a DC voltage between the second resistor section and the second differential input section.

According to the exemplary embodiment, there is provided a resolver abnormality detection apparatus capable of detecting a wire breakage, a sky-fault and a ground-fault without limitation of the angular position of the resolver.

Other advantages and features of the invention will become apparent from the following description including the drawings and claims.

In the accompanying drawings:

FIG. 1 is a diagram showing the structure of a resolver abnormality detection apparatus according to an embodiment of the invention.

A resolver abnormality detection apparatus for a resolver according to an embodiment of the invention is described with reference to FIG. 1 .

In this embodiment, the resolver includes a primary winding 10 , a secondary winding 20 A (a first secondary winding) and a secondary winding 20 B (a second secondary winding). The primary winding 10 , the secondary winding 20 A and the secondary winding 20 B are insulated from one another. The primary winding 10 is connected with an excitation circuit (not shown) for supplying an excitation signal to the primary winding 10 . The secondary winding 20 A constitutes a cosine phase. The secondary winding 20 B constitutes a sine phase.

The primary winding 10 is mechanically coupled to the rotor of a motor. Each of the mutual inductance between the secondary winding 20 A and the primary winding 10 and the mutual inductance between the secondary winding 20 B and the primary winding changes depending on the rotational angle θ of the rotor of the motor. Accordingly, the output voltage of the secondary winding 20 A becomes a modulated wave signal equivalent to the excitation signal modulated with a modulating wave signal cos θ, and the output voltage of the secondary winding 20 B becomes a modulated wave signal equivalent to the excitation signal modulated with a modulating wave signal sin θ.

Next, the structure of the cosine phase of the resolver abnormality detection apparatus is explained. A Y-capacitor for removing common mode noise is connected across the secondary winding 20 A. The Y-capacitor is constituted of capacitors C 1 A and C 2 A. The capacitor CIA is connected to a signal line 81 of the secondary winding 20 A. The capacitor 2 A is connected to a signal line S 3 of the secondary winding 20 A.

Further, a resistor section 30 A (a first resistor section) is connected to the secondary winding 20 A on the more output side than the capacitors C 1 A and C 2 A. The resistor section 30 A includes a pull-up resistor R 1 A (a first pull-up resistor), a pull-down resistor R 2 A (a first pull down resistor), and a pull-up power supply E 1 A (a first DC power supply). The pull-up power supply E 1 A, which is a DC power supply of a voltage VPA, is connected to a first end of the pull-up resistor R 1 A. A second end of the pull-up resistor R 1 A is connected to the signal line S 1 of the secondary winding 20 A. The pull-up resistor R 1 A is for pulling up the signal line S 1 of the secondary winding 20 A to the voltage of the pull-up power supply E 1 A. A first end of the pull down resistor R 2 A is grounded. A second end of the pull-down resistor R 2 A is connected to the signal line S 3 of the secondary winding 20 A. The pull-down resistor R 2 A is for pulling down the signal line S 3 of the secondary winding 20 A to a ground voltage.

The resistance of the pull-up resistor R 1 A is set to the same value as the pull-down resistor R 2 A. The resistance of the pull-up resistor R 1 A and the pull-down resistor R 2 A is sufficiently larger than the DC resistance of the secondary winding 20 A. Accordingly, since the DC component of the voltage between the signal lines S 1 and 53 can be regarded to be zero, the DC voltage at a connection node P 1 A between the signal line S 1 and the pull-up resistor R 1 A is VPA/2. That is, the signal line S 1 and the signal line S 3 are equal to each other in DC voltage.

The second end of the pull-up resistor R 1 A is connected with a first end of a resistor R 3 A for gain adjustment. The second end of the pull-up resistor R 2 A is connected with a first end of a resistor R 4 A for gain adjustment. Between second ends of the resistor R 3 A and R 4 A, a capacitor C 3 A for removing normal mode noise is connected. The resistances of the resistance R 3 A and the resistance R 4 A are set equal to each other.

The capacitor 3 A is connected to a differential input section 40 A (a first differential input section) at is both ends. The differential input section 40 A includes resistors R 5 A to R 8 A, a DC power supply E 2 A of a voltage of Vc and a differential amplifier OPA. The resistors R 5 A and R 7 A are series-connected to the terminal on the side of the signal line S 1 of the capacitor C 3 A. The resistors R 6 A and R 8 A are series-connected to the terminal on the side of the signal line S 3 of the capacitor C 3 A. The connection node between the resistor R 5 A and the resistor R 7 A is connected to the inverting input of the differential amplifier OPA. The connection node between the resistor R 6 A and the resistor R 8 A is connected to the non-inverting input of the differential amplifier OPA. The resistor R 7 A is connected to the output terminal of the differential amplifier OPA. The resistor R 8 A is connected to the DC power supply E 2 A. The resistance of the resistor R 5 A is set equal to that of the resistor R 6 A. The resistance of the resistor R 7 A is set equal to that of the resistor R 8 A.

Here, it is assumed that the voltage at the connection node between resistor R 5 A and capacitor C 3 A, that is, the input voltage of differential input section 40 A on the side of the signal line S 1 is Vi 1 , and the voltage at the connection node between the resistor R 6 A and the capacitor C 3 A, that is, the input voltage of differential input section 40 A on the side of the signal line S 3 is Vi 3 . In this assumption, the output voltage VOA of the differential amplifier OPA is equal to Vc+R 7 A/R 5 A(Vi 3 −Vi 1 ).

Between the resistor R 3 A and the capacitor C 3 A, a filter 50 A is connected. The filter 50 A, which is a low-pass filter for removing AC components, is constituted of a resistor R 9 A and a capacitor C 4 A.

Next, the structure of the sine phase of the resolver abnormality detection apparatus is explained. The structure of the sine phase is similar to that of the cosine phase described above. Signal lines S 2 and S 4 of the secondary winding 20 B correspond to the signal lines S 1 and S 3 , respectively. Capacitors C 1 B and C 2 B correspond to the capacitors C 1 A and C 2 A, respectively. A resistor section 30 B (a second resistor section) including a pull-up resistor R 1 B (a second pull-up resistor), a pull-down resistor R 2 B (a second pull-down resistor) and a pull-up power supply E 1 B (a second DC power supply) corresponds to the resistor section 30 A. A difference input section 40 B (a second difference input section) corresponds to the difference input section 40 A. A filter 50 B corresponds to the filter 50 A. A resistor R 3 B, a resistor R 4 B and a capacitor C 3 B correspond to the resistor R 3 A, the resistor R 4 A and the capacitor C 3 A, respectively.

The respective components and power supplies of the sine phase are the same in value as those of the cosine phase except for the voltage of the pull-up power supply E 1 B. The voltage of the pull-up power supply E 1 B is a DC voltage of VPB which is different from the voltage of VPA. Accordingly, the DC voltage of VPB/2 at the connection node P 1 B between the signal line S 2 and the pull-up resistor R 1 B differs from the DC voltage VPA/2 at the connection node P 1 A. Accordingly, when the resolver is normal, the DC voltage at the connection node P 2 A between the resistor R 3 A and the filter 50 A is different in value from the DC voltage at the connection node P 2 B between the resistor R 3 B and the filter 50 B. That is, the DC voltage outputted from the filter 50 A is different in value from the DC voltage outputted from the filter 50 B. Here, the resolver is assumed to be normal if there is no abnormality such as a wire breakage, a short circuit, a sky fault (that is, a short circuit to the battery positive terminal), a ground fault or an interphase short-circuit in the primary winding 10 or secondary windings 20 A and 20 B.

The output voltage VMA (a first voltage) of the filter 50 A of the cosine phase and the output voltage VMB (a second voltage) of the filter 50 B of the sine phase are inputted to the microcomputer 60 . The output voltage of the differential input section 40 A of the cosine phase and the output voltage of the differential input section 40 B of the sine phase are also inputted to a microcomputer 60 .

An A/D converter included in the microcomputer 60 converts the voltages VMA and VWB outputted from the filters 50 A and 50 B, and the voltages VOA and VOB outputted from the differential input sections 40 A and 40 B into digital values. The microcomputer 60 detects an abnormality in the secondary windings 20 A and 20 B based on the voltages VMA and VWB and the voltages VOA and VOB having been converted into the digital values. Specifically, the microcomputer 60 detects a wire breakage, a short circuit, a sky fault, a ground fault or an interphase short-circuit in the secondary windings 20 A and 20 B. The output terminal of the filter 50 A is connected with a diode DA and a power supply E 3 A. The output terminal of the filter 50 B is connected with a diode DB and a power supply E 3 B. The diodes DA and DB and the power supplies E 3 A and E 3 B are for reducing each of the input voltages of the microcomputer 60 below a predetermined value when a sky fault occurs in the secondary winding 20 A or 20 B to protect the microcomputer 60 .

The resolver abnormality detection apparatus of this embodiment is constituted of the resistors 30 A and 30 B, the differential input sections 40 A and 40 B, the filters 50 A and 50 B, and the microcomputer 60 . Next, the operation of the resolver abnormality detection apparatus is explained.

For a case where a wire breakage occurs in the signal line S 1 or S 3 :

If there is no wire breakage, since the signal line S 1 and the signal line 83 are at the same DC voltage, the DC component of the output voltage VOA of the differential input section 40 A is equal to Vc. That is, the output voltage VOA the differential input section 40 A is at the voltage Vc superimposed with an AC component. The AC component is equivalent to the change with time of the envelope of the modulated wave signal of the cosine phase.

When there is a wire breakage in the signal line S 1 or S 3 , specifically, when the secondary winding 20 A is broken on the more input side than the resistor section 30 A is, the DC component of the voltage inputted to the differential input section 40 A becomes equal to the voltage VPA of the pull-up power supply E 1 A on the side of the signal line S 1 , and becomes equal to the ground voltage on the side of the signal line S 3 . Accordingly, the DC component of the output voltage VOA offsets to the ground side compared to when there is no wire breakage.

Accordingly, the microcomputer 60 detects a presence of a wire breakage in the signal line S 1 or S 3 when the DC component of the output voltage VOA has decreased below a threshold value. When a wire breakage occurs in the signal line S 1 or S 3 , since the DC component of the output voltage VOA always becomes lower than the threshold value regardless of the rotational angle of the rotor, the wire breakage can be detected reliably without limitation of the rotational angle of the rotor. The microcomputer 60 can detect a wire breakage also in the signal line S 2 or S 4 in a similar way to the above.

For a case where a short circuit occurs between the signal line S 1 and the signal line S 3 :

In this case, both the DC component and the AC component of the voltage between the signal lines S 1 and S 3 become zero. Accordingly, the output voltage VOA becomes equal to the voltage Vc of the DC power supply E 2 A. The microcomputer 60 detects a presence of an interphase short-circuit between the signal lines S 1 and S 3 by comparing the output voltage VOA with an upper threshold value and a lower threshold value. The upper threshold value is larger than the voltage Vc, and the lower threshold value is smaller than the voltage Vc. The upper and lower threshold values are set such that one of the output voltage VOA of the differential input section 40 A and the output voltage VOB of the differential input section 40 B is always larger than the upper threshold value, or always smaller than the lower threshold value as long as both the cosine phase and the sine phase are normal.

Accordingly, if a short circuit occurs between the signal lines S 1 and S 3 the microcomputer 60 detects a presence of the short circuit when the output voltage VOB of the cosine phase is detected to be between the upper threshold value and the lower threshold value. The microcomputer 60 can detect a short circuit also between the signal lines S 2 and S 4 in the similar way to the above.

For a case where a sky fault occurs in the signal line S 1 or S 3 :

If a short circuit occurs between the positive terminal of a DC power supply such as a battery and the signal line S 1 or S 3 , that is, if a sky fault occurs in the signal line S 1 or S 3 , the DC voltage of the DC power supply is applied to the signal lines S 1 and S 3 . Accordingly, the DC voltage at the connection node P 2 A, that is, the output voltage VMA of the filter 50 A when both the signal lines S 1 and S 3 are normal is set lower than the DC voltage assumed to be applied to the signal lines S 1 and S 3 when a sky fault has occurred. In this setting, when a sky fault occurs in the signal line S 1 or S 3 , the DC voltage at the connection node P 2 A and the output voltage VMA of the filter 50 A increase from their normal values, respectively. Accordingly, the microcomputer 60 detects a presence of the sky fault in the signal line S 1 or S 3 when the output voltage of the filter 50 A exceeds a sky-fault threshold. The sky-fault threshold value is larger than the normal value of the output voltage VMA. The microcomputer 60 can detect a presence of a sky fault also in the signal line S 2 or 54 in the similar way to the above.

For a case where a ground fault occurs in the signal line S 1 or S 3 :

When the signal line S 1 or S 3 is short-circuited to the ground, that is, when a sky fault has occurred in the signal line S 1 or S 3 , the ground voltage is applied to the signal lines S 1 and S 3 . Accordingly, the DC voltage at the connection node P 2 A, that is, the output voltage VMA of the filter 50 A when both the signal lines S 1 and S 3 are normal is set larger than the ground voltage. In this setting, when a sky fault has occurred in the signal line S 1 or S 3 , the DC voltage at the connection node P 2 A and the output voltage VMA of the filter 50 A decrease from their normal values, respectively. Accordingly, the microcomputer 60 detects the presence of the ground fault in the signal line S 1 or S 3 when the output voltage VMA of the filter 50 A decreases below a ground-fault threshold value. The ground-fault threshold value is set smaller than the normal value of the output voltage VMA. The microcomputer 60 can detect a presence of a ground fault also in the signal line S 2 or S 4 in the similar way to the above.

For a case where an interphase short-circuit occurs:

In this embodiment, the voltage VPA of the pull-up power supply E 1 A, and voltage VPB of the pull-up power supply E 1 B are set different from each other, so that the DC voltage at the connection node P 2 A is different from the voltage at the connection node P 2 B when both secondary windings 20 A and 20 B are normal. Accordingly, if the signal line S 3 of the cosine phase and the signal line 92 of the sine phase are short-circuited to each other, causing an interphase short-circuit between the cosine phase and the sine phase, the output voltage VMB of the filter 50 B changes. For example, when the DC voltage at the connection node P 2 A is larger than the DC voltage at the connection node P 2 B, the output voltage VMB increases from its normal value when an interphase short-circuit has occurred. However, since the DC voltage at the connection node P 2 A is smaller than the voltage applied to the sine phase when a sky fault has occurred, the output voltage VBM does not increase so much when an interphase short-circuit has occurred compared to when a sky fault has occurred. On the other hand, when the DC voltage at the connection node P 2 A is smaller than the DC voltage at the connection node P 2 B, the output voltage VMB decreases from its normal value when an interphase short-circuit has occurred. However, the output voltage VBM does not decrease so much compared to when a ground fault has occurred.

Accordingly, the microcomputer 60 detects a presence of the interphase short-circuit when the output voltage VBM exceeds an interphase short-circuit threshold value if the DC voltage at the connection node P 2 A is larger than the DC voltage at the connection node P 2 B. The interphase short-circuit threshold value is set larger than the normal value of the output voltage VBM and smaller than the sky fault threshold value. Further, the microcomputer 60 detects a presence of the interphase short-circuit when the output voltage VBM falls below an interphase short-circuit threshold value if the DC voltage at the connection node P 2 A is smaller than the DC voltage at the connection node P 2 B. The interphase short-circuit threshold value is set smaller than the normal value of the output voltage VBM, and larger than the ground-fault threshold value.

The resolver abnormality detection apparatus according to the embodiment described above provides the following advantages.

It is possible to detect a wire breakage, a sky fault or a ground fault in the secondary winding 20 A or 20 B without limitation of the rotational angle of the rotor by monitoring the output voltages VOA and VOB of the differential input sections 40 A and 40 B, and the output voltage VMA and VMB of the filters 50 A and 50 B.

Since the voltage VPA of the pull-up power supply E 1 A and the voltage VPB of the pull-up power supply E 1 B are set to different values from each other, the DC voltage at the connection node P 2 A and the DC voltage at the connection node P 2 B when both the secondary windings 20 A and 20 B are normal can be made different from each other. Accordingly, it is possible to detect an interphase short-circuit between the secondary windings 20 A and 20 B based on the output voltage VMB of the filter 50 B.

Since the normal values of the output voltages VMA and VMB are set between the DC voltage applied to the secondary winding 20 A when a sky failure has occurred and the ground voltage and between the DC voltage applied to the secondary winding 20 B when a sky failure has occurred and the ground voltage, respectively, it is possible to detect a sky fault and a ground fault in each of the secondary windings 20 A and 20 B based on the output voltages VMA and VMB.

Since the filter 50 A is connected between the resistor section 30 A and the differential input section 40 A, and the filter 50 B is connected between the resistor section 30 B and the differential input section 40 B, it is possible to extract the output voltages VMA and VMB as DC components to be supplied to the microcomputer 60 .

Other Embodiments

It is possible that the voltage VPA of the pull-up power supply E 1 A and voltage VPB of the pull-up power supply E 1 B are set equal to each other, and the resistances of the pull-up resistor and the pull-down resistor are set different from each other at least at one of the cosine phase and the sine phase. Also in this setting, the output voltage VMA of the filter 50 A and the output voltage VMB of filter 50 B can be made different from each other when both the secondary windings 20 A and 20 B are normal.

For example, if the resistance of the pull-down resistor R 2 A is set to twice that of the pull-up resistor R 1 A, the DC voltage at the connection node P 1 A becomes VPA×2/3. On the other hand, if the resistance of the pull-down resistor R 2 B and the resistance of the pull-up resistor R 1 B are set equal to each other, the DC voltage at the connection node P 1 B becomes VPB/2. Accordingly, the output voltage VMA of the filter 50 A and output voltage VMB of the filter 50 B can be made different from each other although the voltage VPA and the voltage VPB are equal to each other.

Further, the resistance of the pull-up resistor R 1 B and the resistance of the pull-down resistor R 2 B may be set different from each other. For example, if the resistance of the pull-up resistor R 1 B is set to twice that of the pull-down resistor R 2 B, the DC voltage at the connection node P 1 B becomes VPB×1/3. Accordingly, the output voltage VMA of the filter 50 A and output voltage VMB of the filter 50 B can be made different from each other although the voltage VPA and the voltage VPB are equal to each other.

Further, it is possible that the voltage VPA of the pull-up power supply E 1 A and the voltage VPB of the pull-up power supply E 1 B are set equal to each other, and the resistance of the pull-up resistor and the resistance of the pull-down resistor are set different from each other. In this case, the voltages VPA and VPB of the pull-up power supplies E 1 A and E 1 B, and the resistances of the pull-up resistors R 1 A and R 1 B and the pull-down resistors R 2 A and R 2 B are set such that the output voltage VMA of the filter 50 A and output voltage VMB of the filter 50 B are different from each other when both the secondary windings 20 A and 20 B are normal.

A comparator may be used instead of the microcomputer 60 . In this case, the comparator compares the output voltages VOA and VOB of the differential input sections 40 A and 40 B with their thresholds, and compares the output voltages VMA and VMB of the filters 50 A and 50 B with their thresholds to detect an abnormality in the secondary winding 20 A or 20 B.

In a case where it is not necessary to detect any interphase short-circuit between the secondary winding 20 A and the secondary winding 20 B, the output voltage VMA of the filter 50 A and the output voltage VMB of the filter 50 B may be set to the same value. That is, in this case, it is possible that the voltages VPA and VPB of the pull-up power supplies E 1 A and E 1 B are set to the same value, the resistances of the pull-up resistor R 1 A and the pull-down resistor R 2 A are set to the same value, and the resistances of the pull-up resistor R 1 B and the pull-down resistor R 2 B are set to the same value.

The filter 50 A may be connected between the resistor R 4 A and the capacitor C 3 A instead of between the resistor R 3 A and the capacitor C 3 A. The filter 50 B may be connected between the resistor R 4 B and the capacitor C 3 B instead of between the resistor R 3 B and the capacitor C 3 B.

The resistor R 3 A and the resistor R 4 A may be connected between the capacitor C 3 A and the differential input section 40 A. In this case, the filter 50 A is connected between the pull-up resistor R 1 A and the capacitor C 3 A or between the pull-down resistor R 2 A and the capacitor C 3 A. The resistor R 3 B and the resistor R 4 B may be connected between the capacitor C 3 B and the differential input section 40 B. In this case, the filter 50 B is connected between the pull-up resistor R 1 B and the capacitor C 3 B or between the pull-down resistor R 2 B and the capacitor C 3 B.

The above explained preferred embodiments are exemplary of the invention of the present application which is described solely by the claims appended below. It should be understood that modifications of the preferred embodiments may be made as would occur to one of skill in the art.