JP2006042590A - Apparatus and method of correcting detected current value of three-phase motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an apparatus and a method of correcting the detected current value of a three-phase motor, without using special devices by performing a correction for enhancing the relative accuracy of the current detector. <P>SOLUTION: The apparatus of correcting the detected current value of the three-phase motor includes a current detector for detecting the currents of the respective phases of three phases, and a detected current value correcting means for relatively correcting, based on the correlation of the detected value of the current detector, provided to the other two phases at the zero-crossing time of the current of one phase of the three phase at the three-phase motor operating time. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a detection current value correction device and a correction method of a current detector for smoothly rotating a three-phase motor.

  In conventional three-phase motor control devices, there are variations in the resistance, amplifier, etc. of each phase of the current detector, so the output of the current detector includes an offset error and a gain error, respectively. For this reason, the current setting value and the current value actually supplied to the three-phase motor do not match, causing an unbalance in the three-phase current and causing torque ripple. In order to solve such a problem, a method of correcting the current detection value as follows is disclosed as one method (Patent Document 1).

  First, one of the phases (U, V, W) of the three-phase motor is set as a reference phase (U), and the current of each phase is detected in a state where no current flows in any phase of the three-phase motor at the time of correction. The offset error (Δu, Δv, Δw) of each device is obtained. Next, a predetermined current flows only in the reference phase (U) and the other one phase (V), and the other phase (V) is output from the outputs of the current detectors of the U phase and the V phase at this time. ) Current detector gain error (ΔGv). Further, a predetermined current flows only in the reference phase (U) and another one phase (W), and the other one phase (from the outputs of the U-phase and W-phase current detectors at this time) W) The gain error (ΔGw) of the current detector is obtained. During the operation of the three-phase motor, the detected values (Iu) of the current detectors for each phase are obtained using the offset errors (Δu, Δv, Δw) and gain errors (ΔGv, ΔGw) of the obtained current detectors for each phase. , Iv, Iw) are respectively corrected, and currents corresponding to the corrected detection values (Icu, Icv, Icw) of the current detector are supplied to the three-phase motor.

  FIG. 1 is a schematic diagram of a circuit for explaining the conventional correction method. Transistors Tru1, Tru2, Trv1, Trv2, Trw1, and Trw2 are provided in each phase of U, V, and W to form an inverter circuit, and output of variable voltage and variable duty obtained by switching the output of DC power supply V + To drive the three-phase motor M. Ru, Rv, and Rw are resistors constituting the current detector of each phase. FIG. 1 shows that a predetermined current i flows only in the reference phase (U) and the other one phase (V). The case where the output of the current detector of U phase and V phase is calculated | required is shown.

FIG. 2 is a diagram showing another configuration for obtaining the current detection value of each phase in order to correct the current detection value of the current detector, and shows a case of obtaining the current detection value of the U phase among the three phases. . Transistor T _RU1, T _ru2 is a transistor provided in the U-phase of the inverter circuit, a constant current source flowing a predetermined current, detects this by the resistance R _u constituting the current detector is amplified by an amplifier Amp Output to the microcomputer, A / D conversion is performed here, and correction is performed based on the converted detected current value.
That is, in these conventional techniques, correction is performed by generating a unique state such as flowing a predetermined current only in a certain arbitrary phase when correcting the current detection value.

Japanese Patent Laid-Open No. 5-91780

The current detector is composed of a resistor, an amplifier, and the like. However, since each element varies, the current value detected by the detector may be different even if the current value is the same.
In order to improve the control accuracy of the three-phase motor, offset errors etc. included in the output of the current detector of each phase are detected and corrected, but for that purpose it is necessary to detect the current value accurately, A device for this is required.

On the other hand, in order to smoothly rotate the three-phase motor, when the same value of current flows in a plurality of phases of the motor at a certain time, the detected current value may be set to the same value. What is necessary is just to raise the relative accuracy instead of the absolute accuracy of the current of each phase (U, V, W).
Accordingly, an object of the present invention is to provide a method for correcting the current detection value of a three-phase motor without using a special device by performing correction to increase the relative accuracy of the current detector. .

  According to the detected current value correction device for a three-phase motor according to the present invention, the current detector for detecting the current of each of the three-phase motors has a current detector, and when the three-phase motor is operating, the current of one phase of the three phases Detection current value correction means for performing relative correction based on the correlation of detection values of current detectors provided in the other two phases at the time of zero crossing.

  The detected current value correcting means is based on a correlation between detection values of the current detectors provided in the other two phases at the time of zero crossing when the current of one phase rises and at the time of zero crossing when falling. And make relative corrections.

  In addition, the detected current correction means, the detection value of the current detector provided in the other two phases at the time of zero crossing of the one-phase current, the current of the three-phase motor is relatively large, medium, Detect when it is small.

  In addition, when the current of the three-phase motor is 0 [A], it further includes storage means for storing the detection value of the current detector for each of the three-phase phases. The determination at the time of zero crossing of the current is performed when the detection value of the current detector provided in one phase of the three phases coincides with the detection value of the one phase stored in the storage means.

According to the detected current value correction method of the three-phase motor according to the present invention, the current detector detects the current of each of the three phases, and when the three-phase motor is operated, a certain one of the three phases Relative correction is performed based on the correlation of the detection values of the current detectors provided in the other two phases at the time of zero crossing of the current.
In addition, when the three-phase motor is operating, one phase of the three phases is used as a reference phase, and the current value of the other one phase is detected at the time of zero crossing of the current value of one of the other two phases. The one-phase current detection value is corrected to be equal to the reference phase current detection value.

  According to the present invention, by correcting the detected current value of the three-phase motor relatively, it is possible to correct the detected current value due to variations in the current detector without using a special device, so that correction can be easily performed. it can.

  Further, there is no need to generate a specific state for correcting the current detection value, such as flowing a predetermined current only in a certain arbitrary phase. Therefore, for example, even after shipment of a product having a three-phase electric motor such as an electric power steering, it is possible to correct the current detection value at any time if the product is in use. Can be eliminated.

  In addition, even if there is further variation in the resistance of each phase current detector, amplifier, etc. due to deterioration caused by the usage status and environment of the product, it is possible to correct the current detection value at any time if the product is in use. Therefore, it is possible to correct the current detection value appropriately according to the variation even after the product is shipped.

  In addition, during use of a product having a three-phase motor, since various current patterns exist, the correction accuracy can be improved.

FIG. 3 is a diagram showing an outline of the configuration of a control circuit for a three-phase motor to which the correction method according to the present invention is applied. Transistors T _ru1 , T _ru2 , T _rv1 , T _rv2 , T _rw1 , T _rw2 are provided in each phase of U, V, W to constitute an inverter circuit, and are obtained by switching the output of the DC power supply V +. The three-phase motor M is driven by voltage and variable duty output. These drive controls are performed by the inverter drive unit 3 controlled by the microcomputer 1. R _u , R _v , and R _w are resistors constituting current detectors for each phase, and the currents flowing through the respective phases are detected by these resistors and amplified by the amplifiers A _u , A _v , A _w for each phase. The detected current value output to the microcomputer 1 is A / D converted and stored in the storage device 2. FIG. 3 shows an example applied to an electric power steering device that assists the steering operation of the vehicle with a three-phase motor. Therefore, a steering torque signal from the torque sensor 4 and a vehicle speed signal from the vehicle speed sensor 5 are input to the microcomputer 1. Yes. FIG. 4 shows an example of the configuration of the rotor, and the position of the rotor 6 detected by the rotor position detection sensor 7 is sent to the microcomputer 1.

FIG. 5 is a three-phase alternating current waveform diagram for explaining the first correction method according to the present invention. FIG. 5 shows a waveform when the level of the current value of the electric motor is relatively small. As can be seen from the figure, in the three-phase AC waveform, when the current value of one phase is 0, the absolute values of the other two-phase currents are the same. For example, the absolute value of the U-phase current when the W-phase current value is 0 | i _us (t1) |, the absolute value of the V-phase current | i _vs (t1) |, and the absolute value of the U-phase current | I _us (t2) | is equal to the absolute value of the V-phase current | i _vs (t2) |.
| I _us (t1) | = | i _vs (t1) |
| I _us (t2) | = | i _vs (t2) |
I _us (t1) and i _vs (t1) are the current values at zero crossing when the W-phase current rises, and i _us (t2) and i _vs (t2) are the W-phase current. It is the current value at zero crossing when it falls. When the U-phase and V-phase current values are each 0, the absolute values of the other two-phase currents are similarly equal.
In addition, when the current value (DI _w ) detected and stored in the W phase when the current of a three-phase motor, which will be described later, is 0 [A], and the detected current value in the W phase match, the zero crossing in the W phase occurs. It's time. In the case of the U phase and the V phase, the U phase and the V phase are zero-crossed when the detected current values of the U phase and the V phase coincide with the stored values DI _u and DI _v .

FIG. 6 shows a waveform when the level of the current value of the electric motor is relatively medium. As in the case of FIG. 5, in the three-phase AC waveform, when the current value of one phase is 0, the absolute values of the other two-phase currents are the same. Absolute value | i _um (t1) | of U phase current when current value of W phase is 0, absolute value of current V phase | i _vm (t1) |, and absolute value of current of U phase | i _um (t2) | is equal to the absolute value of the V-phase current | i _vm (t2) |.
| I _um (t1) | = | i _vm (t1) |
| I _um (t2) | = | i _vm (t2) |
Note that i _um (t1) and i _vm (t1) are current values at zero crossing when the W-phase current rises, and i _um (t2) and i _vm (t2) are the W-phase current rises. It is the current value at zero crossing when it falls.
In addition, when the current value of the current value detected and stored in the W phase (DI _w ) matches the detected current value in the W phase when the current of a three-phase motor described later is 0 [A], the zero crossing in the W phase occurs. It's time. In the case of the U phase and the V phase, the U phase and the V phase are zero-crossed when the detected current values of the U phase and the V phase coincide with the stored values DI _u and DI _v .

FIG. 7 shows a waveform when the level of the current value of the electric motor is relatively large. As in the case of FIG. 5, in the three-phase AC waveform, when the current value of one phase is 0, the absolute values of the other two-phase currents are the same. Absolute value of U phase current | i _ub (t1) |, absolute value of V phase current | i _vb (t1) |, and absolute value of U phase current | i when W phase current value is 0 _ub (t2) | is equal to the absolute value of the V-phase current | i _vb (t2) |.
| I _ub (t1) | = | i _vb (t1) |
| I _ub (t2) | = | i _vb (t2) |
I _ub (t1) and i _vb (t1) are current values at zero crossing when the W-phase current rises, and i _ub (t2) and i _vb (t2) are the W-phase current. It is the current value at zero crossing when it falls.
In addition, when the current value of the current value detected and stored in the W phase (DI _w ) matches the detected current value in the W phase when the current of a three-phase motor described later is 0 [A], the zero crossing in the W phase occurs. It's time. In the case of the U phase and the V phase, the U phase and the V phase are zero-crossed when the detected current values of the U phase and the V phase coincide with the stored values DI _u and DI _v .

[Example 1]
FIG. 8 is a flowchart for explaining the first correction method of the present invention. The control performed in this flowchart is performed by the microcomputer 1 in FIG. The flowchart will be described below with reference to FIG.
[Detected current value of each phase current detector when the motor current is 0 [A]]
(1) First, when the motor current is 0 [A], that is, when the motor is not energized, the output of each phase current detector is obtained as an offset error. The current value at this time is detected through resistors R _u , R _v , R _w constituting the current detector, and the detected current value I amplified by the amplifiers (Amp) A _u , A _v , A _w of each phase. _u , I _v , and I _w are output to the microcomputer 1. Detected current value I _u microcomputer 1, I _v, and I _w converted A / D, the digital signal DI _u indicating the offset error of each phase of the current detector, DI _v, to obtain the DI _w. Then, the acquired digital signals DI _u , DI _v , DI _w are stored in the storage device 2 (S1). The storage device is composed of, for example, an EE-PROM.

[Detection current value of U-phase and V-phase current detectors when W-phase current is zero crossing]
(2) Next, when the electric motor is driven and the current value level is relatively small as shown in FIG. 5, the detected current value I _us of the U-phase current detector when the W-phase current is zero- _crossed. (t1), I _us (t2), and detection current values I _vs (t1) and I _vs (t2) of the V-phase current detector are output to the microcomputer 1. The detected current values I _us (t1), I _us (t2), I _vs (t1), and I _vs (t2) are A / D converted by the microcomputer 1 and the digital signal values DI _us (t1) and DI _us (t2) , DI _vs (t1), DI _vs (t2) are acquired and stored in the storage device.

Similarly, as shown in FIG. 6, digital signal values DI _um (t1), DI _um (t2), DI _vm (t1), and DI _vm (t2) when the current level is relatively medium are obtained. Save it in the storage device.
Further, as shown in FIG. 7, the digital signal values DI _ub (t1), DI _ub (t2), DI _vb (t1), and DI _vb (t2) when the level of the current value is relatively large are obtained, Save in the storage device (S2).
(3) Next, a correlation between the acquired detected current values is obtained. Specifically, as shown in FIG. 9, the detected current value is A / D converted into coordinates where the horizontal axis is the actual current value of the motor and the vertical axis is the current value detected by the detector. Plot the absolute value of the measured digital signal value.

  As shown in FIG. 9, the absolute values of the digital signal values of the U-phase and V-phase detected currents when the actual current value level of the motor is 0 [A] and the small, medium, and large values acquired in advance are respectively shown. Plot. Note that the actual current value of the motor on the horizontal axis may be selected as a relatively large, medium, or small value for the motor, and it is not necessary to select a specific exact value.

Next, a straight line (DI _u = A _u · i + B _u ) along the distribution is obtained from the distribution of the absolute values of the detected currents of the U phase (B _u is the detection when the U phase is 0 [A]. Value), and similarly, a straight line (DI _v = A _v · i + B _v ) along the distribution is obtained from the distribution of the absolute values of the detected currents of the V phase (B _v is 0 [A] for the V phase) Detection value at the time).

By deleting “i” from the above two formulas, the following formula is derived.
_{DI u = (A u / A} v) DI v + B u - (A u / A v) B V or _{DI v = (A v / A} u) DI u + B v - (A v / A u) B u
The above expression represents the correlation between the U-phase detection current and the V-phase detection current (S3).

  In addition, when the distribution of the plotted detection current values is not a straight line, for example, a quadratic curve, a quadratic curve related to the U-phase detection current and a quadratic curve related to the V-phase detection current Find the correlation. The same applies when the U-phase and V-phase currents described below are at zero crossing.

[Detection current value of V-phase and W-phase current detectors when U-phase current is zero-crossing]
(4) Similarly, when the motor is driven and the current value level is relatively small as shown in FIG. 5, the detected current value I _vs of the V-phase current detector when the U-phase current is zero- _crossed (t1), I _vs (t2) and detection current values I _ws (t1), I _ws (t2)) of the W-phase current detector are output to the microcomputer 1. The microcomputer 1 _performs A / D conversion on the detected current values I _vs (t1), I _vs (t2), I _ws (t1), and I _ws (t2) to _obtain digital signal values DI _vs (t1), DI _vs (t2) , DI _ws (t1), DI _ws (t2) are acquired and stored in the storage device.

Similarly, as shown in FIG. 6, the digital signal values DI _vm (t1), DI _vm (t2), DI _wm (t1), and DI _wm (t2) when the current level is relatively medium are obtained. Save it in the storage device.
Further, as shown in FIG. 7, the digital signal values DI _vb (t1), DI _vb (t2), DI _wb (t1), and DI _wb (t2) when the level of the current value is relatively large are obtained. Save in the storage device (S4).

(5) Next, the correlation between the acquired detected current values is obtained. Specifically, as shown in FIG. 10, the detected current value is A / D converted into coordinates where the horizontal axis is the actual current value of the motor and the vertical axis is the current value detected by the detector. Plot the absolute value of the measured digital signal value.

  As shown in FIG. 10, the absolute values of the digital signal values of the V-phase and W-phase detected currents when the actual current value level of the motor is 0 [A] and the small, medium, and large levels acquired in advance are respectively shown. Plot. Note that the actual current value of the motor on the horizontal axis may be selected as a relatively large, medium, or small value for the motor, and it is not necessary to select a specific exact value.

Next, a straight line (DI _v = A _v · i + B _v ) along the distribution is obtained from the distribution of the absolute values of the detected current of the V phase (B _v is the detection when the V phase is 0 [A]. Value), similarly, a straight line (DI _w = A _w · i + B _w ) along the distribution is determined from the distribution of the absolute values of the detected current of the W phase (B _w is 0 [A] for the W phase). Detection value at the time).

By deleting “i” from the above two formulas, the following formula is derived.
DI _v = (A _v / A _w ) DI _w + B _v − (A _v / A _w ) B _w or DI _w = (A _w / A _v ) DI _v + B _w − (A _w / A _v ) B _v
The above expression represents the correlation between the V-phase detection current and the W-phase detection current (S5).

[Detected current value of W-phase and U-phase current detectors when V-phase current is zero crossing]
(6) Similarly, when the motor is driven and the current value level is relatively small as shown in FIG. 5, the detected current value I _ws of the W-phase current detector when the V-phase current is zero- _crossed. (t1), I _ws (t2) and detection current values I _us (t1), I _us (t2)) of the U-phase current detector are output to the microcomputer 1. The microcomputer 1 _performs A / D conversion on the detected current values I _ws (t1), I _ws (t2), I _us (t1), and I _us (t2) to _obtain digital signal values DI _ws (t1), DI _ws (t2 ), DI _us (t1), DI _us (t2) are acquired and stored in the storage device.

Similarly, as shown in FIG. 6, digital signal values DI _wm (t1), DI _wm (t2), DI _um (t1), and DI _um (t2) when the current level is relatively medium are obtained. Save it in the storage device.
Further, as shown in FIG. 7, the digital signal values DI _wb (t1), DI _wb (t2), DI _ub (t1), and DI _ub (t2) when the level of the current value is relatively large are obtained. Save in the storage device (S6).

(7) Next, the relationship between the acquired detected current values is obtained. Specifically, as shown in FIG. 11, the detected current value is A / D converted into coordinates where the horizontal axis is the actual current value of the motor and the vertical axis is the current value detected by the detector. Plot the absolute value of the measured digital signal value.
As shown in FIG. 11, the absolute values of the digital signal values of the W-phase and U-phase detected currents when the actual current value level of the motor is 0 [A] and the small, medium, and large levels acquired in advance are respectively shown. Plot. Note that the actual current value of the motor on the horizontal axis may be selected as a relatively large, medium, or small value for the motor, and it is not necessary to select a specific exact value.

Then, from the distribution of the absolute value of the detected current of the plotted W-phase, linearly along converting said fabric _{(DI w = A w · i} + B w) asking (B _w is detected when the W phase is 0 [A] Value), similarly, a straight line (DI _u = A _u · i + B _u ) along the distribution is obtained from the distribution of the absolute values of the detected currents of the W phase (B _u is 0 [A] for the U phase) Detection value at the time).

By deleting “i” from the above two formulas, the following formula is derived.
_{DI w = (A w / A} u) DI u + B w - (A w / A u) B u or _{DI u = (A u / A} w) DI w + B u - (A u / A w) B w
The above expression represents the correlation between the W-phase detection current and the U-phase detection current (S7).

[Correction based on correlation between phases]
(8) Using the correlation formula obtained in the above (S3), (S5), and (S7), conversion can be performed as follows.
(1) When converting the V phase and the W phase into U phase values, the following equations can be used.
DI _{v (u)} = (A _u / A _v ) DI _v + B _u − (A _u / A _v ) B _{v
DI w (u) = (A} u / A w) DI w + B u - (A u / A w) B w
(2) When converting the U phase and the W phase into values of the V phase, the following equation can be used.
DI _{u (v)} = (A _v / A _u ) DI _u + B _v − (A _v / A _u ) B _u
DI _{w (v)} = (A _v / A _w ) DI _w + B _v − (A _v / A _w ) B _w
(3) When converting the U phase and the V phase into W phase values, the following equations can be used.
_{DI u (w) = (A} w / A u) DI u + B w - (A w / A u) B u
DI _{v (w)} = (A _w / A _v ) DI _v + B _w − (A _w / A _v ) B _v

[Example 2]
In the second correction method of the present invention, one phase of the three phases is set as a reference phase, and the detected value of the current of the other phase is set as a reference at the time of zero crossing of the current value of one phase among the other two phases. The correction is made to be equal to the detected value of the phase current. Furthermore, the current detection value of one phase is corrected to be equal to the current detection value of the reference phase at the time of zero crossing of the current value of another one phase among the other two phases. Thereby, it can correct | amend so that the electric current detection value of two phases may become equal to the electric current detection value of a reference | standard phase, and can eliminate an offset error.
In the present embodiment, an example based on the U phase is shown, but the same detection current value can be corrected even if the other phase is used as the reference phase.

FIG. 12 is a flowchart for explaining the second correction method of the present invention. The control in this flowchart is performed by the microcomputer 1 in FIG. The flowchart will be described below with reference to FIG.
First, the detection current value of each phase current detector when the motor current is 0 [A] is acquired (S11).
When the motor current is 0 [A], that is, when the motor is not energized, the output of each phase current detector is obtained as an offset error. The current value at this time is detected through resistors R _u , R _v , R _w constituting the current detector, and the detected current value I amplified by the amplifiers (Amp) A _u , A _v , A _w of each phase. _u , I _v , and I _w are output to the microcomputer 1. Detection current value I _u microcomputer 1, I _v, and I _w converts A / D, the digital signal DI _u, DI _v, to obtain the DI _w. The acquired digital signals DI _u , DI _v , DI _w are stored in the storage device 2 as B _u , B _v , B _w indicating the offset error of the current detector of each phase. The storage device is composed of, for example, an EE-PROM.

Next, the detection current values of the U-phase and V-phase current detectors when the W-phase current is zero crossing are acquired (S12).
When the motor is driven and the current value level is relatively small as shown in FIG. 5, the detected current values I _us (t1) and I _us of the U-phase current detector when the W-phase current is zero- _crossed (t2) and the detected current values I _vs (t1) and I _vs (t2) of the V-phase current detector are output to the microcomputer 1. The detected current values I _us (t1), I _us (t2), I _vs (t1), and I _vs (t2) are A / D converted by the microcomputer 1 and the digital signal values DI _us (t1) and DI _us (t2) , DI _vs (t1), DI _vs (t2) are acquired and stored in the storage device.
Similarly, as shown in FIG. 6, digital signal values DI _um (t1), DI _um (t2), DI _vm (t1), and DI _vm (t2) when the current level is relatively medium are obtained. Save it in the storage device.
Further, as shown in FIG. 7, the digital signal values DI _ub (t1), DI _ub (t2), DI _vb (t1), DI _vb (t2) when the current value is relatively large are obtained, Save to storage.

  And the correlation of the acquired said detected electric current value is calculated | required (S13). Specifically, as shown in FIG. 9, the detected current value is A / D converted into coordinates where the horizontal axis is the actual current value of the motor and the vertical axis is the current value detected by the detector. Plot the absolute value of the measured digital signal value.

  As shown in FIG. 9, the absolute values of the digital signal values of the U-phase and V-phase detected currents when the actual current value level of the motor is 0 [A] and the small, medium, and large values acquired in advance are respectively shown. Plot. Note that the actual current value of the motor on the horizontal axis may be selected as a relatively large, medium, or small value for the motor, and it is not necessary to select a specific exact value.

Next, from the distribution of the absolute values of the U-phase detected currents plotted, a straight line along the distribution DI _u = A _u · i + B _u ... ... (1)
Ask for. Here, B _u is a detected value of the U phase when the U phase is 0 [A], and is a value corresponding to an offset error. Similarly, from the distribution of the absolute values of the V-phase detected currents plotted, a straight line DI _v = A _v · i + B _v along the distribution… ... (2)
Ask for. Here, B _v is a detected value of the V phase when the V phase is 0 [A], and is a value corresponding to an offset error.

From the above formulas (1) and (2), when “i” is deleted from the U-phase formula (1),
DI _u = (A _u / A _v ) DI _v + B _u − (A _u / A _v ) B _v (3)
Is expressed as an equation of a V-phase current corrected with reference to the value of the U-phase,
_{DI v (u) = (A} u / A v) DI v + B u - (A u / A v) B v ······· (4)
It becomes.
By substituting the current value of the V phase detected by the current detector into DI _v in the equation (4), the detected value of the V phase can be corrected to the same value as the detected current value of the U phase of the reference phase.
Thereby, in the U phase and the V phase, the distance between the straight lines of both phases, that is, the offset error is eliminated.

Next, the detection current values of the U-phase and W-phase current detectors when the V-phase current is zero crossing are acquired (S14).
When the motor is driven and the current value level is relatively small as shown in FIG. 5, the detected current values I _us (t1) and I _us of the U-phase current detector when the V-phase current is zero crossing (t2) and detection current values I _ws (t1) and I _ws (t2) of the W-phase current detector are output to the microcomputer 1. The detected current values I _us (t1), I _us (t2), I _ws (t1), and I _ws (t2) are A / D converted by the microcomputer 1 and the digital signal values DI _us (t1), DI _us (t2) , DI _ws (t1), DI _ws (t2) are acquired and stored in the storage device.
Similarly, as shown in FIG. 6, digital signal values DI _um (t1), DI _um (t2), DI _wm (t1), and DI _wm (t2) when the current value level is relatively medium are obtained. Save it in the storage device.
Further, as shown in FIG. 7, the digital signal values DI _ub (t1), DI _ub (t2), DI _wb (t1), and DI _wb (t2) when the level of the current value is relatively large are obtained. Save to storage.

  And the correlation of the acquired said detected electric current value is calculated | required (S15). Specifically, as shown in FIG. 11, the detected current value is A / D converted into coordinates where the horizontal axis is the actual current value of the motor and the vertical axis is the current value detected by the detector. Plot the absolute value of the measured digital signal value.

  As shown in FIG. 11, the absolute values of the digital signal values of the U-phase and W-phase detected currents when the actual current value level of the motor is 0 [A] and small, medium, and large obtained in advance are respectively shown. Plot. Note that the actual current value of the motor on the horizontal axis may be selected as a relatively large, medium, or small value for the motor, and it is not necessary to select a specific exact value.

Next, from the distribution of the absolute values of the U-phase detected currents plotted, a straight line along the distribution DI _u = A _u · i + B _u ... ... (1)
Similarly, from the plotted distribution of the absolute values of the detected current of the W phase, a straight line DI _w = A _w · i + B _w ... (5)
Ask for. Here, B _w is a detected value of the W phase when the W phase is 0 [A], and is a value corresponding to an offset error.

From the above equations (1) and (5), when “i” is deleted from the U-phase (1) equation,
DI _u = (A _u / A _w ) DI _w + B _u − (A _u / A _w ) B _w (6)
Is expressed as an equation of the W-phase current corrected with reference to the value of the U-phase,
_{DI w (u) = (A} u / A w) DI w + B u - (A u / A w) B w ······· (7)
It becomes.
By substituting the current value of the W phase detected by the current detector into DI _w in the equation (7), the detected value of the W phase can be corrected to the same value as the detected current value of the U phase of the reference phase.
As a result, in the U phase and the W phase, the distance between the straight lines of the two phases, that is, the offset error is eliminated.

  And electric motor control is performed using the detected electric current value acquired by the said Formula (1), (4) Formula, (7) Formula (S16).

Actual current has value value of the motor, for example, if a current value of a value a small level (i _s), the current of one phase of the three phases is detected in the other two phases during zero-crossing The absolute values of the currents must be equal. However, due to variations in detectors, they may not necessarily be equal as shown in FIGS.
In the present invention, the relative accuracy of the detected current value can be improved by correcting the detected current value based on the above equation and controlling the corrected two-phase current values to be equal. .

  The present invention is applicable to any device having a three-phase motor. Preferably, by applying the present invention to an electric power steering device that assists the steering operation of the vehicle with a three-phase motor, a smooth steering operation without torque ripple can be provided to the user.

The schematic of the circuit for demonstrating the conventional correction method. The schematic of the circuit for demonstrating the conventional correction method. The figure which showed the outline | summary of the structure of the control circuit for three-phase motors to which the correction method by this invention is applied. The figure which shows an example of a structure of a rotor. FIG. 3 is a waveform diagram of a three-phase AC for explaining the correction method according to the present invention (when the level of the current value is relatively small). FIG. 6 is a three-phase AC waveform diagram for explaining the correction method according to the present invention (when the current value level is relatively medium); FIG. 3 is a waveform diagram of a three-phase AC for explaining the correction method according to the present invention (when the level of the current value is relatively large). The flowchart for demonstrating the 1st correction method of this invention. On the coordinates, the absolute value of the digital signal value of the U-phase and V-phase detected currents when the actual current value level of the motor is small, medium, and large and the W-phase current value is 0 [A]. Each plot. On the coordinates, the absolute value of the digital signal value of the V-phase and W-phase detected currents when the actual current value level of the motor is small, medium and large and the U-phase current value is 0 [A]. Each plot. On the coordinates, the absolute value of the digital signal value of the detected current of the W phase and U phase when the actual current value level of the motor is small, medium and large and the current value of the V phase is 0 [A]. Each plot. The flowchart for demonstrating the 2nd correction method of this invention.

Explanation of symbols

_{DESCRIPTION OF SYMBOLS} 1 Microcomputer 2 Memory _| storage device 3 Inverter drive part 4 Torque sensor 5 _Vehicle speed sensor 6 Rotor 7 Rotor position detection sensor M Electric motor _Tru1 , _Tru2 , _Trv1 , _Trv2 , _Trw1 , _Trw2 Transistor which comprises inverter circuit R _u , R _v , R _w Current detection resistor Amp amplifier

Claims (8)

A detection current value correction device for a three-phase motor having a current detector for detecting a current of each phase of the three phases,
Detection in which the relative correction is performed based on the correlation of the detection values of the current detectors provided in the other two phases at the time of zero crossing of the current of one phase of the three phases during the operation of the three-phase motor. A detected current value correcting apparatus comprising a current value correcting means.   The detected current value correcting means is based on a correlation between detection values of the current detectors provided in the other two phases at the time of zero crossing when the current of one phase rises and / or at the time of zero crossing when falling. 2. The detected current value correcting apparatus according to claim 1, wherein relative correction is performed.   The detected current correction means is configured to detect a detected value of the current detector provided in the other two phases at the time of zero crossing of the one-phase current when the current of the three-phase motor is relatively large, medium, and small. 2. The detected current value correcting apparatus according to claim 1, wherein the detected current value correcting apparatus detects at a certain time. When the current of the three-phase motor is 0 [A], further comprising storage means for storing the detected value of the current detector for each of the three-phase phases,
The determination at the time of zero crossing of the current of one phase of the three phases is performed by determining the detected value of the current detector provided in one phase of the three phases and the one phase stored in the storage means. The detection current value correction device according to claim 1, wherein the detection current value correction device is performed when the detection value matches. A detection current value correction method for a three-phase motor having a current detector for detecting a current of each phase of the three phases,
Relative correction is performed based on the correlation between the detection values of the current detectors provided in the other two phases at the time of zero crossing of the current of one phase of the three phases during operation of the three-phase motor. A method for correcting a detected current value. An electric power steering control device for correcting a current value of a three-phase motor having a current detector for detecting a current of each phase of three phases,
During the operation of the three-phase motor, based on the correlation of the detected values of the current detectors provided in the other two phases at the time of zero crossing of the current of one phase of the three phases, the other two phases An electric power steering control device comprising: current value correcting means for performing relative correction of the current value of the current. A control device for a three-phase motor having a current detector for detecting a current of each phase of the three phases, and when the three-phase motor operates, one phase of the three phases is set as a reference phase,
Current value detection means for detecting the current value of the other one phase at the time of zero crossing of the current value of one phase among the other two phases,
Detection current value correcting means for correcting the detected value of the other one-phase current to be equal to the detected value of the current of the reference phase;
A control device for a three-phase motor, comprising: A detection current value correction method for a three-phase motor having a current detector for detecting a current of each phase of the three phases,
During operation of the three-phase motor, one phase of the three phases is a reference phase,
At the time of zero crossing of the current value of one of the other two phases, the current value of the other one phase is detected,
Correcting the detected value of the other one-phase current to be equal to the detected value of the current of the reference phase,
Detection current value correction method.

Images