JPH06121573A - Automatic offset regulator for current detector - Google Patents

Abstract

PURPOSE:To prevent pulsation of torque generated from a servo motor by performing automatic correction of offset correcting value even during operation of servo motor. CONSTITUTION:Upon occurrence of an error in offset correction due to temperature variation or the like during operation, an electrical angle detecting means 27 detects pulsation of torque generated from a servo motor based on a quadrature axis current value and first and second electrical angles, for which the quadrature axis current is maximized and minimized respectively by the pulsating components, based on an electrical angle signal of motor. Furthermore, a decision means 28 makes a decision whether an error has occurred in offset correction based on the difference between first and second electrical angles. If a decision is made that an error has occurred, a correcting means 31 adds a regulation value corresponding to the first electrical angle to offset correcting values c1, c2 thus updating them.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic offset adjusting device for a current detector in a digital control device for a servo motor used in a highly accurate NC device or robot.

[0002]

2. Description of the Related Art Conventionally, in a digital controller for a servomotor used in a highly accurate NC device or robot, when a current detector composed of an analog circuit is used as a current detecting means, the output of the current detector is Offset correction is performed. That is, when the motor is stopped after the power is turned on, the detected output voltage of the current detector is used as the offset correction value, and the offset correction value set when the power is turned on is not updated during the operation of the motor. .

[0003]

However, in the above-mentioned conventional configuration, the actual offset value and the offset correction set at the time of turning on the power supply due to the change of the ambient temperature during the long-time operation and the temperature rise of the elements in the current detector. When an error occurs between the value and the value, there is a problem that the torque generated by the servo motor has a pulsation with the same cycle as the electrical angle.

The present invention solves the above-mentioned conventional problems. When the correction error of the offset correction value caused by the temperature rise of the current detector is generated, the three-phase AC feedback current value from the servomotor is changed to three-phase / Current detection that can be determined from the pulsation of the horizontal axis current value obtained by 2-phase conversion and that the offset correction value is automatically corrected even during motor operation to prevent torque pulsation generated in the servo motor. It is an object of the present invention to provide an automatic offset adjusting device for a container.

[0005]

In order to achieve the above object, an automatic offset adjusting device for a current detector according to the present invention is provided for a current controller in a digital controller for a servomotor using a current detector having an offset value. An automatic offset adjustment device, wherein a three-phase AC feedback current value of the servomotor and an electrical angle signal are input, rotation is in one direction for one cycle of the electrical angle, and the rotation speed is less than or equal to a predetermined upper limit set value. The rotation detecting means for detecting and the first electric angle at which the horizontal axis current obtained from the three-phase AC feedback current value of the motor becomes maximum and the second electric angle at which the horizontal electric current becomes minimum during one cycle of the electric angle are detected. Electrical angle detection means, determination means for determining whether the difference between the first electrical angle and the second electrical angle detected by the electrical angle detection means is 180 degrees, and the determination means The difference between the first electrical angle and a second electrical angle 1
When it is determined that the angle is 80 degrees, a correction unit that corrects the offset correction value of the current detector according to the first electrical angle is provided.

Further, in the correction means for correcting the offset correction value of the current detector in the automatic offset adjusting apparatus of the present invention, the first electric angle is in any of the divided ranges obtained by dividing the electric angle of 360 degrees into eight ranges. An electrical angle existing range determining means for determining whether or not there is an offset correction value adjustment amount set according to the eight divided ranges, and the offset correction of the divided range in which the first electrical angle exists in the offset correction value. An offset correction value output means for adding and updating the value adjustment amount and outputting the added value adjustment amount.

Further, in the correction means for correcting the offset correction value of the current detector in the automatic offset adjusting apparatus of the present invention, the first electrical angle is divided into four ranges by dividing the electrical angle of 360 degrees into four ranges. An electrical angle existing range determination means for determining whether or not there is an offset correction value adjustment amount set according to the four divided ranges, and the offset correction of the divided range in which the first electrical angle exists in the offset correction value. An offset correction value output means for adding and updating the value adjustment amount and outputting the added value adjustment amount.

[0008]

According to the above construction, even if a correction error occurs in the offset correction value due to a temperature change during operation,
The occurrence of a correction error in the offset correction value due to the temperature rise of the current detector is judged from the pulsation of the horizontal axis current value obtained from the feedback current value of the servo motor, and the horizontal axis current is maximum during one electrical angle cycle. Since the offset value of the current detector is corrected according to the electrical angle, the offset correction value is automatically corrected even while the servo motor is operating, preventing pulsation of the motor-generated torque and increasing the speed ripple. It is possible to suppress the deterioration of the control performance.

[0009]

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment 1) FIG. 1 is a block diagram of a servo motor digital controller having an automatic offset adjusting device for a current detector according to a first embodiment of the present invention.
In FIG. 1, the adder 1 to which the speed command value a is input is connected to the sine wave table 3 via the speed control unit 2, and the torque command value b from the speed control unit 2 is input to the sine wave table 3. The output ends of the offset correction value automatic adjustment device 4 and the U-phase current detector 5 having an offset value are connected to the adder 6, and the U-phase offset correction value c1 from the offset correction value automatic adjustment device 4 and the current The U-phase detected current value d1 having the offset value from the detector 5 is input to the adder 6. The adder 6 is connected to the offset correction value automatic adjustment device 4 and the adder 7, and the U-phase feedback current value g1 is input to the offset correction value automatic adjustment device 4 and the adder 7. The sine wave table 3 is connected to the adder 7,
The U-phase current command value e1 from the sine wave table 3 and the U-phase feedback current value g1 from the adder 6 are input to the adder 7. The adder 7 is connected to a servomotor 10 via a proportional element 8 and a servo amplifier 9. The U-phase current detector 5 is provided between the servo amplifier 9 and the servo motor 10. The output ends of the offset correction value automatic adjustment device 4 and the V-phase current detector 11 having an offset value are connected to the adder 12, and the V-phase offset correction value c2 from the offset correction value automatic adjustment device 4 is connected.
Then, the V-phase detected current value d2 having the offset value from the current detector 11 is input to the adder 12. The adder 12 is connected to the offset correction value automatic adjustment device 4 and the adder 13, and the V-phase feedback current value g2 is input to the offset correction value automatic adjustment device 4 and the adder 13. The sine wave table 3 is connected to the adder 13, and the V phase current command value e2 from the sine wave table 3 and the V phase feedback current value g2 from the adder 12 are added to the adder 13.
Entered in. The adder 13 is connected to the servo motor 10 via the proportional element 14 and the servo amplifier 9. A V-phase current detector 11 is provided between the servo amplifier 9 and the servo motor 10. Furthermore, the adder 6 and the adder 12 are connected to the offset correction value automatic adjustment device 4 via the adder 20, and in the adder 20, W
The phase current feedback value g3 is calculated and input to the offset correction value automatic adjustment device 4, and the adder 7 and the adder 13 add the adder 15, the proportional element 16, and the servo amplifier 9.
Is connected to the servomotor 10 via.

Further, the servo motor 10 has an encoder 17
And the encoder 17 is connected to the position counter 18
The electric angle signal f of the servomotor 10 from the position counter 18 is connected to the offset correction value automatic adjustment device 4 and the sine wave table 3 via the. Also, encoder 1
7 is connected to the adder 1 via the speed detection circuit 19, and inputs the speed feedback value h from the speed detection circuit 19 to the adder 1.

FIG. 2 is a block diagram showing the internal configuration of the offset correction value automatic adjustment apparatus 4 of FIG. In FIG. 2, the speed control processing cycle setting means 21 is the servo motor 1
The three-phase AC feedback current values g1, g2, g3 of 0 and the electrical angle signal f are input, and the three-phase AC feedback current values g1, g2, g3 and the electrical angle signal f are passed, and the speed control process return flag is set. Set to proceed to the next speed control cycle. The rotation detection means 22 to which the speed control processing cycle setting means 21 is connected receives the electrical angle signal f, the rotation direction is the same as the rotation direction of the previous speed control processing cycle, and the rotation speed is generated by the servo motor 10. It is detected that the phase difference between the torque and the horizontal axis current value is less than or equal to a predetermined upper limit set value so as not to cause a problem. The electrical angle detecting means 27 to which the rotation detecting means 22 is connected includes a horizontal axis current detecting means 23 and a maximum value detecting means 24.
And a minimum value detecting means 25 and an electrical angle counter 26. The horizontal axis current detection means 23 is the servo motor 1
The three-phase AC feedback current values g1, g2, g3 of 0 and the electrical angle signal f are input, and the three-phase feedback current of the servo motor 10 is converted into a three-phase / two-phase signal to obtain the same phase as the torque generated by the servo motor 10. The related horizontal axis current value is detected. The horizontal axis current detecting means 23 is connected to the maximum value detecting means 24 and the minimum value detecting means 25. The maximum value detecting means 24 receives the horizontal axis current value and the electrical angle signal f as input, stores the electrical angle when the horizontal axis current value becomes maximum as the first electrical angle f1, and the minimum value detecting means 25. Stores the electrical angle when the horizontal axis current value becomes the minimum as the second electrical angle f2. The electrical angle counter 26, to which the maximum value detecting means 24 and the minimum value detecting means 25 are connected, counts the electrical angle signal and, if one electrical angle cycle is not detected, sets the speed control processing return flag to the speed control processing cycle setting means. 21 is output. Judgment means 28 to which the electrical angle detection means 27 is connected
Determines whether the difference between the electrical angle f1 and the electrical angle f2 detected by the electrical angle detection means 27 is 180 degrees. Electrical angle existence range determination means 29 to which the determination means 28 is connected
Indicates that the difference between the electrical angle f1 and the electrical angle f2 is 18 by the determination means 28.
When it is determined that the electrical angle f0 is 0 degree, the range in which the electrical angle 360 degrees is divided into eight is determined. The offset correction value output means 30 to which the electric angle existence range determination means 29 is connected has an offset correction value adjustment amount set according to the eight division ranges, and offset correction of the division range in which the electric angle f1 exists. The value adjustment amount is added to the offset correction value to be updated, and is output as the offset correction values c1 and c2. These electrical angle existence range determination means 29 and offset correction value output means 30
The correction unit 31 is configured by the above, and is configured to correct the offset values of the current detectors 5 and 11 according to the first electrical angle.

Further, the rotation detecting means 22 and the judging means 28
The initialization means 32 to which the offset correction value output means 30 is connected with the maximum value of the horizontal axis current value according to the initialization flag output from any one of the rotation detection means 22, the determination means 28, and the offset correction value output means 30. , Minimum value and electrical angle f
1. Initialize the electrical angle f2, and then output the speed control processing return flag to the speed control processing cycle setting means 21.
At the time of initial setting, the initial value of the offset correction value is also set in the initializing means 32.

In the offset correction value automatic adjusting device 4 configured as described above, when an error occurs in the offset correction value of the current detector, the torque generated by the servomotor 10 has a pulsation with the same cycle as the electrical angle. , Servo motor 10
The first electrical angle f1 at which the horizontal axis current value has the same phase relationship as the torque generated at the maximum and the minimum second electrical angle f
There are two. In this embodiment, the offset correction value is automatically adjusted by detecting the electrical angle f1.

FIG. 3 is a flow chart showing a calculation process in the offset correction value automatic adjustment apparatus 4 of FIG. 2. Among these calculation processes, processes S0 to S1 indicate processes at the time of initial setting, and a speed control process SV. The processes S2 to S8 indicate processes performed during normal operation. As shown in FIG. 3, first, the processing S0
In step S1, the offset correction value determined at power-on according to the conventional technique is set as an initial value, and the process S1
In, the maximum value and the minimum value of the horizontal axis current value, and the values of the electrical angle f1 and the electrical angle f2 are initialized.

Normal operation is started, and the speed control process SV
Is executed, the rotation detection means 2 is processed in step S2.
2 detects the current rotation direction of the motor shaft, compares this rotation direction with the rotation direction at the previous speed control process,
If the rotation direction has changed, the process proceeds to step S8, and the initialization unit 32 initializes the maximum and minimum values of the horizontal axis current value and the values of the electrical angle f1 and the electrical angle f2, and proceeds to the next speed control processing cycle. . If the rotation direction is the same as the previous speed control processing cycle, the process proceeds to step S3. In the process S3, the rotation detecting means 22 detects the current rotation speed, and if the rotation speed is equal to or higher than the preset upper limit set value, the process S3 is performed.
Similar to step 2, the process proceeds to step S8, and the initialization unit 32 causes the maximum and minimum values of the horizontal axis current value and the electrical angle f1 and the electrical angle f2.
The value of is initialized and the process proceeds to the next speed control processing cycle. If the rotation speed is less than or equal to the upper limit set value, the process proceeds to step S4. In process S4, the horizontal axis current value and the electrical angle signal f detected by the horizontal axis current detecting means 23 are once in the speed control processing cycle until the electrical angle counter 26 detects the passage of one electrical angle cycle.
Is inputted to the maximum value detecting means 24 and the minimum value detecting means 25, and in the maximum value detecting means 24, the electrical angle when the horizontal axis current value measured until one cycle of the electrical angle has reached the maximum value The value of the signal is stored as the first electrical angle f1, and the minimum value detecting means 25 obtains the minimum value of the horizontal axis current values measured until one electrical angle cycle elapses. The value is stored as the second electrical angle f2. While the elapse of one electrical angle cycle is not detected, the process proceeds to the next speed control processing cycle, and when the elapse of one electrical angle cycle is detected, the process proceeds to step S5. In step S5, the torque pulsation caused by the correction error of the offset correction value has the same cycle as the electrical angle. Therefore, if the absolute value of the angular difference between the electrical angle f1 and the electrical angle f2 is not 180 degrees by the determining means 28, It is determined that torque pulsation due to factors other than the offset correction error has occurred, and the maximum and minimum values of the horizontal axis current value and the electrical angle f1 and electrical angle f2 are initialized by the initialization means 32 in step S8. After that, the process proceeds to the next speed control processing cycle. If the absolute value of the angle difference between the electrical angle f1 and the electrical angle f2 is 180 degrees, it is determined that torque pulsation due to the offset correction error has occurred, and the process proceeds to step S6. Here, it is assumed that the angle difference of 180 degrees allows an error of α degrees during measurement.

In step S6, the electrical angle existence range determining means 2 is used.
9, it is determined in which range the electrical angle f1 exists in a range obtained by dividing an electrical angle of 360 degrees, which will be described later, into eight parts. From the result of the determination, in step S7, the offset correction value output means 30 detects the U phase The offset correction value adjustment amount is added to the U-phase offset correction value to update and output the offset correction value c1, and the V-phase offset correction value adjustment amount is added to the V-phase offset correction value to obtain the offset correction value. c2 is updated and is output. After outputting the offset correction values c1 and c2, the maximum value and the minimum value of the horizontal axis current value and the values of the electrical angle f1 and the electrical angle f2 are initialized by the initialization means 32 in the process S8, and the next speed control process is performed. Go to cycle.

In the speed control process SV, all the processes except the process in the automatic offset correction value adjusting device 4 in FIG. 1 are performed, and the U-phase detection current d1 including the offset value from the current detector 5 is detected. By subtracting the U-phase offset correction value c1 output from the offset correction value output means 30, the corrected U-phase feedback current g1 is obtained. Similarly, the V-phase feedback current corrected by subtracting the V-phase offset correction value c2 output from the offset correction value output means 30 from the V-phase detection current d2 including the offset value from the current detector 11. g2 is obtained.

The adjustment amount of the offset correction value is determined as follows. First, the U-phase offset correction error is dI _u , and the V-phase offset correction error is dI _v . DI _u is defined by equation (1) and dI _v is defined by equation (2).

DI _u = (U-phase offset correction value c1)-(actual U-phase offset value) (1) dI _v = (V-phase offset correction value c2)-(actual V-phase offset value) (2 ) The magnitude relationship between the positive and negative signs of dI _u and dI _v and the absolute value thereof is found depending on where the electrical angle f1 exists within one cycle of the electrical angle of 360 degrees. Here, FIG. 4A shows the magnitude relationship between the positive and negative signs of dI _u and dI _{v and} the absolute values of dI _u and dI _v for each range in which the electrical angle f1 exists. Electrical angle f1 shown in FIG.
Of each division range and offset correction error dI
The relationship between _u and dI _v is such that when the electrical angle f1 is 0 degree or more and less than 60 degrees (R1 in FIG. 4A), dI _u ≦ 0, dI _v > 0, | dI _u | <| dI _v | The electrical angle f1 is 60 degrees or more and less than 120 degrees (see FIG. 4).
In the case of R2) in (a), dI _u <0, dI _v > 0, | dI _u | ≧ | dI _v | The electrical angle f1 is 120 degrees or more and less than 150 degrees (see FIG. 4).
In the case of R3) in (a), dI _u <0, dI _v ≦ 0, | dI _u |> | dI _v | The electrical angle f1 is 150 degrees or more and less than 180 degrees (see FIG. 4).
In the case of R4) of (a), dI _u <0, dI _v <0, | dI _u | ≦ | dI _v | The electrical angle f1 is 180 degrees or more and less than 240 degrees (see FIG. 4).
In the case of R5) in (a), dI _u ≧ 0, dI _v <0, | dI _u | <| dI _v | The electrical angle f1 is 240 degrees or more and less than 300 degrees (see FIG. 4).
In the case of R6) in (a), dI _u > 0, dI _v <0, | dI _u | ≧ | dI _v | The electrical angle f1 is 300 degrees or more and less than 330 degrees (see FIG. 4).
In the case of R7) in (a), dI _u > 0, dI _v ≧ 0, | dI _u |> | dI _v | The electrical angle f1 is 330 degrees or more and less than 360 degrees (see FIG. 4).
In the case of R8) in (a), dI _u > 0, dI _v > 0, and | dI _u | ≦ | dI _v |.

The adjustment amount of the offset correction value is determined according to the above relationship. As an example, the electrical angle f1 is shown in FIG.
When it exists in the range R1 of (a), the offset correction error dI _u of the U phase becomes a negative value, and it is shown from Equation (1) that the offset correction value is smaller than the actual offset value. The U-phase offset correction value c1 is obtained by increasing the current value by a predetermined amount. Again d
I _v is a positive value, which means that the offset correction value is larger than the actual offset value from the equation (2).
The V-phase offset correction value c2 is obtained by reducing the current value from the current value. These offset correction values are increased / decreased by increasing / decreasing the digital values of the outputs of the current detectors 5 and 11 for each 1n level (1n bit) or 2n level (2n bit) (n is a positive integer 1, 2, 3, ... Represents).

The weight for increasing or decreasing the offset correction value is determined by the magnitude relationship of the absolute values of the correction error. In the case of R1, since | dI _u | <| dI _v |, the offset correction value of the V phase is reduced by the digital value 2n level (2n bits) of the output of the current detector 11, and the offset correction value of the U phase is The digital value of the output of the detector 5 is increased by 1n level (1n bit). FIG. 4 shows the adjustment amount obtained when n = 1 for each range in FIG.
It shows in (b).

(Second Embodiment) Next, a second embodiment of the present invention will be described.

The range in which the electrical angle f1 is determined in step S6 of FIG. 3 of the first embodiment is divided into four. That is, in FIG. 5A, the electrical angle of 360 degrees is divided into four ranges, and the positive and negative signs of the U and V phase offset correction errors dI _u and dI _v and the magnitude of the absolute value are divided for each range in which the electrical angle f1 exists. It represents a relationship. The relationship between the offset correction errors dI _u and dI _v according to the range in which the electrical angle f1 exists is that the electrical angle f1 is less than 360 degrees when the electrical angle is 330 degrees or more and 60 degrees when the electrical angle f1 is 0 degrees or more.
If less than 60 degrees (R1 in FIG. 5 (a)): | dI _u | ≦ | dI _v |, dI _v > 0 The electrical angle f1 is 60 degrees or more and less than 150 degrees (FIG. 5).
In the case of R2) in (a), | dI _u | ≧ | dI _v |, dI _u <0 where electrical angle 1 is 150 degrees or more and less than 240 degrees (FIG. 5).
In the case of R3) of (a), | dI _u | ≦ | dI _v |, dI _v <0 The electrical angle 1 is 240 degrees or more and less than 330 degrees (see FIG. 5).
In the case of R4) in (a), | dI _u | ≧ | dI _v |, dI _u > 0.

The adjustment amount of the offset correction value is determined based on the above relationship. As an example, the electrical angle f1 is shown in FIG.
Considering the case of existing in the range R1 in (a), from FIG. 5 (a), | dI _u | ≦ | dI _v |, and the V-phase offset correction error dI _v is a positive value. The offset correction value c2 of is decreased from the current value. The offset correction value is increased / decreased for each digital value 1n level (1n bit) of the output of the current detector 11 (n represents a positive integer). FIG. 5B shows the calculated offset correction value adjustment amounts when n = 1 for each range of R1 to R4 in FIG. 5A.

Therefore, according to each of the above embodiments, when an error occurs in the offset correction value due to a temperature change or the like during the operation, the electrical angle detecting means 27 sets the feedback current value of the three-phase AC of the servo motor to three. The pulsation of the motor-generated torque is detected from the horizontal axis current value obtained by the phase / two-phase conversion, and the electrical angle f1 when the horizontal axis current value becomes maximum and the minimum when the horizontal axis current value becomes minimum due to the ripple component from the electrical angle signal f. The electrical angle f2 is detected, and the determination means 28 further determines the electrical angle f1.
And the electrical angle f2, it is determined whether an offset correction error has occurred. If it is determined that the offset correction error has occurred, the correction means 31 uses the electrical angle f1.
The offset correction value adjustment amount corresponding to the value of is added, and the offset correction value is updated. As a result, a correction error occurs in the offset correction value due to the temperature rise of the element in the current detector due to long-time operation in the servo motor digital controller, and the torque generated by the servo motor has a pulsation of the same cycle as the electrical angle. Even if it occurs, it is possible to detect the occurrence of the offset correction error from the pulsation of the horizontal axis current value and automatically correct the offset correction value.

Although the most preferred embodiment of the present invention has been described in detail with respect to the present invention, the description of the preferred embodiment includes modifications of detailed portions of the configuration and the idea of the present invention described in the claims. It is obvious that various modifications can be made without departing from the above, or a combination thereof can be changed.

[0028]

As described above, according to the present invention, even when a correction error occurs in the offset correction value due to a temperature rise or the like,
The offset correction value can be automatically adjusted during the operation of the servo motor, the torque pulsation generated in the servo motor can be reduced, the deterioration of the control performance such as the increase of speed ripple can be suppressed, and the servo motor can be operated for a long time. Therefore, stable and precise control can be achieved.

[Brief description of drawings]

FIG. 1 is a block diagram of a digital control device for a servomotor having an automatic offset adjustment device for a current detector according to an embodiment of the present invention.

FIG. 2 is a block diagram showing an internal configuration of the offset correction value automatic adjustment apparatus shown in FIG.

FIG. 3 is a flowchart showing an arithmetic processing operation in the offset correction value automatic adjustment apparatus.

FIG. 4A is a relational diagram showing the positive / negative of the value of the electrical angle f1 and the offset correction errors dI _u and dI _v and their magnitude relationship in the first embodiment of the present invention, and FIG. 4B is the first embodiment of the present invention. FIG. 4 is a relationship diagram showing the adjustment amounts of the U-phase offset correction value c1 and the V-phase offset correction value c2 in the embodiment of FIG.

FIG. 5A is a relational diagram showing the positive / negative relationship between the value of the electrical angle f1 and the offset correction errors dI _u and dI _v and their magnitude in the second embodiment of the present invention, and FIG. FIG. 4 is a relationship diagram showing the adjustment amounts of the U-phase offset correction value c1 and the V-phase offset correction value c2 in the embodiment of

[Explanation of symbols]

5 U-phase current detector (current detector) 10 Servo motor 11 V-phase current detector (current detector) 22 Rotation detecting means 27 Electrical angle detecting means 28 Judging means 31 Correction means c1 U-phase offset correction value (offset correction) Value) c2 V phase offset correction value (offset correction value) f Electrical angle signal g1 U phase feedback current value (three-phase AC feedback current value) g2 V phase feedback current value (three-phase AC feedback current value) g3 W-phase feedback Current value (3-phase AC feedback current value)

 ─────────────────────────────────────────────────── ─── Continued front page (72) Inventor Yoshihiro Ino 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (3)

[Claims] 1. An automatic offset adjusting device for a current detector in a digital controller for a servo motor using a current detector having an offset value, wherein a three-phase AC feedback current value and an electrical angle signal of the servo motor are input. The rotation detecting means for detecting that the rotation is in one direction for one electrical angle cycle and the rotation speed is equal to or lower than a predetermined upper limit set value, and the horizontal axis current obtained from the three-phase AC feedback current value of the servo motor are An electrical angle detecting means for detecting a maximum first electrical angle and a minimum second electrical angle during one cycle of the electrical angle, and a first electrical angle detected by the electrical angle detecting means The judgment means for judging whether the difference between the two electric angles is 180 degrees, and the judgment means judges that the difference between the first electric angle and the second electric angle is 180 degrees. First electric A current detector offset automatic adjustment apparatus comprising: a correction unit that corrects an offset correction value of the current detector according to an air angle. 2. The correction means for correcting the offset correction value of the current detector divides the electrical angle of 360 degrees into eight ranges,
An electrical angle existence range determination means for determining which division range the first electrical angle is in, and an offset correction value adjustment amount set according to the eight division ranges, and the first electrical angle is set as the offset correction value. The offset automatic adjustment device for a current detector according to claim 1, further comprising: offset correction value output means for adding and updating the offset correction value adjustment amount in a divided range in which a corner exists. 3. The correction means for correcting the offset correction value of the current detector divides the electrical angle of 360 degrees into four ranges,
An electrical angle existing range determination means for determining which division range the first electrical angle is in, and an offset correction value adjustment amount set according to the four division ranges, and the first electrical angle is set as the offset correction value. The offset automatic adjustment device for a current detector according to claim 1, further comprising: offset correction value output means for adding and updating the offset correction value adjustment amount in a divided range in which a corner exists.