JP3217145B2 - Automatic offset adjustment device for current detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for automatically adjusting the offset of a current detector in a digital control device of a servomotor used for a high-precision NC device or a robot.

[0002]

2. Description of the Related Art Conventionally, in a digital controller for a servomotor used in a high-precision NC device or a robot, when a current detector composed of an analog circuit is used as a current detecting means, the output of the current detector is controlled. The offset is corrected. That is, when the motor is stopped after the power is turned on, the detected output voltage of the current detector is used as an offset correction value, and the offset correction value set at the time of turning on the power is not updated during the operation of the motor.

[0003]

However, in the above-described conventional configuration, the actual offset value and the offset correction set at power-on due to a change in the ambient temperature during a 24-hour operation, a rise in the temperature of the elements in the current detector, and the like. If there is an error between the value and the value, there is a problem that a pulsation of the same cycle as the electrical angle occurs in the torque generated by the servomotor.

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problem, in which the occurrence of a correction error of an offset correction value due to a rise in temperature of a current detector is determined from the pulsation of a torque command value.
It is an object of the present invention to provide an automatic offset adjustment device for a current detector that can automatically execute correction of an offset correction value even during operation of a motor and can prevent pulsation of torque generated by a servomotor.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, an automatic offset adjusting device for a current detector according to the present invention comprises a current detector having a current detector having an offset value. An automatic offset adjusting device, which receives a torque command value of the servomotor and an electrical angle signal, and detects that the rotation is in one direction and the rotation speed is equal to or less than a first set value for one electrical angle cycle. Detecting means, an electrical angle detecting means for detecting a first electrical angle at which a torque command value during one cycle of the electrical angle becomes maximum and a second electrical angle at which the torque command value becomes minimum during the rotation angle detecting means, Determining means for determining whether a difference between the first electrical angle and the second electrical angle detected by the electrical angle detecting means is within a range of a second set value; and determining the first electrical angle by the determining means. Of the angle and the second electrical angle There When it is determined to be within the scope of the second set value, in which a correction means for correcting the offset correction value of the current detector in response to the first electrical angle.

In the automatic offset adjusting device of the present invention, the correction means for correcting the offset correction value of the current detector divides the electrical angle of 360 degrees into eight ranges, and the first electrical angle is in any range. Electric angle existence range determining means for judging whether or not the offset correction value is set in accordance with the eight ranges, and the offset correction value of the divided range in which the first electric angle exists in the offset correction value And an offset correction value output means for adding and updating the adjustment amount and outputting the updated offset correction value.

Further, in the automatic offset adjusting apparatus of the present invention, the correcting means for correcting the offset correction value of the current detector divides the electrical angle of 360 degrees into four ranges,
An electrical angle existence range determining means for determining in which range the electrical angle is located; and an offset correction value adjustment amount set in accordance with the four ranges.
Offset correction value output means for adding and updating the offset correction value adjustment amount in the divided range where the electric angle exists, and outputting the updated offset correction value.

[0008]

With the above configuration, even when a correction error occurs in the offset correction value due to a temperature change or the like during operation, the occurrence of the correction error of the offset correction value due to a rise in the temperature of the current detector can be considered as a pulsation of the torque command value. The offset correction value of the current detector is corrected according to the electrical angle at which the torque command value during one cycle of the electrical angle of the servo motor drive current is maximized. Since the correction of the correction value is performed, pulsation of the motor-generated torque is prevented, and deterioration in control performance such as an increase in speed ripple is suppressed.

[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 digital control device for a servomotor having an automatic offset adjusting device for a current detector according to a first embodiment of the present invention. In FIG. 1, an adder 1 to which a speed command value a is input is a speed controller 2
Is connected to the sine-wave table 3 and the automatic offset correction value adjusting device 4 via the input terminal, and inputs the torque command value b from the speed controller 2 to the sine-wave table 3 and the automatic offset correction value adjusting device 4. The output terminal of the automatic offset correction value adjustment device 4 and the output terminal of 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 automatic offset correction value adjustment device 4, The U-phase detection current value d1 having an offset value from the current detector 5 is input to the adder 6. The adder 6 and the TU 3a of the sine wave table 3 are connected to the adder 7, and the TU 3
The U-phase current command value e1 from a and the output from the adder 6 are input to the adder 7. This adder 7 is a proportional element 8
Further, it is connected to a servo motor 10 via a servo amplifier 9. These servo amplifier 9 and servo motor 10
A U-phase current detector 5 is provided therebetween. The output terminals of the automatic offset correction value adjustment device 4 and the V-phase current detector 11 having an offset value are connected to an adder 12, and the V-phase offset correction value c2 from the automatic offset correction value adjustment device 4 is output. , The V-phase detection current value d2 having an offset value from the current detector 11 is input to the adder 12. The adder 12 and the TV 3b of the sine wave table 3
Is connected to the adder 13, and the V-phase current command value e2 from the TV 3b and the output from the adder 12 are
Is input to 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. Further, the adders 7 and 13 are connected to a servo motor 10 via an adder 15, a proportional element 16, and a servo amplifier 9.

The servo motor 10 is provided with an encoder 17.
And the encoder 17 further includes a position counter 18
The electric angle signal f of the servo motor 10 from the position counter 18 is input to the automatic offset correction value adjusting device 4 and the sine wave table 3 via the. Also, encoder 1
Reference numeral 7 is connected to the adder 1 via a speed detection circuit 19, and inputs the speed feedback value g from the speed detection circuit 19 to the adder 1.

FIG. 2 is a block diagram showing the configuration of the automatic offset correction value adjusting device 4 shown in FIG. In FIG. 2, a speed control processing cycle setting means 21 receives a torque command value b and an electric angle signal f of the servomotor 10, inputs the torque command value b and the electric angle signal f, and sets a speed control processing return flag. Is set so as to proceed to the next speed control cycle. Rotation detecting means 22 for the velocity control period setting unit 21 is connected as input the torque command value b and the electrical angle signal f, the rotating direction of the rotational speed identical to the rotational direction of the velocity control period of the previous It is detected that the value is equal to or less than the first set value. This means that the direction of rotation is reversed or
When exiting the normal operating state where the speed enters the resonance range
Causes unexpected acceleration / deceleration torque,
In the present invention, the state of maximum and minimum movement is used for correction control.
This is because preconditions are broken. The electric angle detecting means 26 to which the rotation detecting means 22 is connected receives the torque command value b and the electric angle signal f, and detects the electric angle when the torque command value becomes maximum when the rotation detecting means 22 detects the electric angle. A maximum value detecting means 23 for storing as the first electrical angle f1, and a minimum value detecting means 2 for storing the electrical angle when the torque command value becomes minimum when the rotation detecting means 22 detects the torque as the second electrical angle f2.
4 and an electrical angle counter 25 that counts the electrical angle signal and outputs a speed control processing return flag to the speed control processing cycle setting means 21 if one electrical angle cycle has not been detected. The judging means 27 to which the electric angle detecting means 26 is connected judges whether or not the difference between the electric angles f1 and f2 detected by the electric angle detecting means 26 is within the range of the second set value. The electric angle existence range judging means 28 to which the judging means 27 is connected, when the judging means 27 judges that the difference between the electric angle f1 and the electric angle f2 is within the range of the second set value, the electric angle 360 It is determined in which range the degree is divided into eight and in which range the electrical angle f1 exists. Offset correction value output means 2 to which the electrical angle existence range determination means 28 is connected
Numeral 9 has an offset correction value adjustment amount set in accordance with the eight division ranges, updates the offset correction value adjustment amount of the division range in which the electrical angle f1 exists by adding it to the offset correction value, and updates this. The offset correction values are output as offset correction values c1 and c2. A correction unit 30 is configured by the electrical angle existence range determination unit 28 and the offset correction value output unit 29, and corrects 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 27
The initialization means 31 connected to the offset correction value output means 29 and the rotation detection means 22, the determination means 27, the maximum value of the torque command value by the initialization flag output from any of the offset correction value output means 29, The minimum value, the electrical angle f1, and the electrical angle f2 are initialized, and thereafter, a speed control process return flag is output to the speed control process cycle setting means 21. At the time of the initial setting, the initial value of the offset correction value is also set by the initializing means 31.

In the automatic offset correction value adjusting device 4 configured as described above, when an error occurs in the offset correction value of the current detector, a pulsation having the same cycle as the electrical angle occurs in the torque generated by the servo motor 10. , There is a first electrical angle f1 at which the torque command value b is maximum and a second electrical angle f2 at which the torque command value b is minimum. In this embodiment, the automatic adjustment of the offset correction value is performed by detecting the electrical angle f1.

FIG. 3 is a flow chart showing a calculation process in the automatic offset correction value adjusting device 4 shown in FIG. 2. In this calculation process, processes S0 to S1 show a process at the time of initial setting, and a speed control process SV. And processes S2 to S8 indicate processes performed during normal operation. As shown in FIG.
At 0, an offset correction value determined when the power is turned on is set as an initial value, and at step S1, the maximum value and the minimum value of the torque command value, and the values of the electrical angles f1 and f2 are initialized.

Next, after the normal operation is started and the speed control process SV is executed, in the process S2, the current rotation direction of the motor shaft is detected by the rotation detecting means 22.
This rotation direction is compared with the rotation direction at the time of the previous speed control processing. If the rotation direction has changed, the process proceeds to step S8, and the initialization means 31 sets the maximum and minimum values of the torque command value, the electrical angle f1, and the electrical angle f1. Initialize the value of the angle f2 and proceed to the next speed control processing cycle. If this rotation direction is the same as the previous speed control processing cycle, the process proceeds to step S3. In the process S3, the current rotation speed is detected by the rotation detecting means 22. If the rotation speed is equal to or higher than the upper limit speed set value which is the first set value set in advance, the process S8 is performed similarly to the process S2.
To the maximum value of the torque command value by the initialization means 31,
Initialize the minimum value and the values of the electrical angles f1 and f2,
The process proceeds to the next speed control processing cycle. If the rotation speed is equal to or lower than the upper limit speed set value, the process proceeds to step S4. In the process S4, the torque command value b and the electrical angle f are input to the electrical angle detecting means 26 once every speed control processing cycle until the electrical angle counter 25 detects the elapse of one electrical angle cycle. Until one cycle elapses, the electrical angle when the torque command value b measured by the maximum value detecting means 23 obtains the maximum value is stored as the first electrical angle f1, and the minimum value detecting means 24 Is stored as the second electrical angle f2 when the minimum value of the torque command value measured in is obtained. The process proceeds to the next speed control processing period while the elapse of one electrical angle cycle is not detected, and proceeds to process S5 if the elapse of one electrical angle cycle is detected. In the process S5, if the absolute value of the angle difference between the electric angle f1 and the electric angle f2 is within the range of the second set value, it is judged by the judging means 27 that the torque pulsation caused by the offset correction error has occurred. Then, the process proceeds to step S6. If the absolute value of the angle difference between the electrical angle f1 and the electrical angle f2 is out of the range of the second set value, it is determined that the torque pulsation is caused by factors other than the offset correction error, and the maximum value of the torque command value and the torque command After the minimum value, the electrical angle f1 and the electrical angle f2 are initialized by the initialization means 31 in step S8, the process proceeds to the next speed control processing cycle. Here, the second set value is that the torque pulsation caused by the correction error of the offset correction value has the same cycle as the electrical angle, and the phase difference between the maximum value and the minimum value of the pulsation is 1
It is determined from being 80 degrees. Α1 and α2 in the process S5 in FIG. 3 of the present embodiment are set as follows: α1 = 180 ° −β (1) α2 = 180 ° + β (2) Here, β is a constant representing an allowable range of an error at the time of measurement.

In step S6, the electrical angle existence range determining means 2
In step S8, the offset correction value output unit 29 determines whether the electrical angle f1 is present in a range obtained by dividing an electrical angle of 360 ° into eight parts. Set the offset correction value adjustment amount to U
The offset correction value of the V-phase is updated by adding it to the offset correction value of the U-phase, and is output as the offset correction value c1 of the U-phase. An offset correction value c2 is output. After outputting the offset correction values c1 and c2, in processing S8, the initialization means 31 sets the maximum value of the torque command value,
Initialize the minimum value and the values of the electrical angles f1 and f2,
The process proceeds to the next speed control processing cycle.

Further, in the speed control process SV, all processes except the process in the automatic offset correction value adjusting device 4 in FIG. 1 are performed, and the U-phase offset correction output from the offset correction value output means 29 is performed. By subtracting the value c1 from the U-phase detection current value d1 including the offset value from the current detector 5, the detection current value d1 having the U-phase offset value is corrected. Similarly, the V-phase offset correction value c2 output from the offset correction value output means 29 is subtracted from the V-phase detection current value d2 including the offset value from the current detector 11 to obtain the V-phase offset value. The correction of the detected current value d2 is performed.

Further, the adjustment amount of the offset correction value is determined as follows. First, dI offset correction error of the U-phase _U, the offset correction error of the V-phase as dI _V, defined by the following equation.

DI _U = (U-phase offset correction value c1) − (actual U-phase offset value) (3) dI _V = (V-phase offset correction value c2) − (actual V-phase offset value) (4) The magnitude relationship between the positive and negative signs and the absolute values of the offset correction errors dI _U and dI _V is determined according to where the electrical angle f1 exists within 360 degrees of one electrical angle cycle. Therefore, the electrical angle f
FIG. 4A shows the magnitude relationship between the positive and negative signs of the offset correction errors dI _U and dI _{V and} the absolute values of the offset correction errors dI _U and dI _V for each range where 1 exists. Electric angle f1 from FIG. 4A
Offset correction error according to each range where
The relationship between dI _U and dI _{V is} as follows: When the electrical angle f1 is equal to or greater than 0 degree and less than 60 degrees (range of FIG. 4A), dI _U <0 dI _V > 0 | dI _U | <| dI _V | When f1 is an electrical angle of 60 degrees or more and less than 120 degrees (the range of FIG. 4A), dI _U <0 dI _V > 0 | dI _U |> | dI _V |, and an electrical angle f1 of 120 degrees or more and less than 150 degrees ( FIG. 4A
DI _U <0 dI _V <0 | dI _U |> | dI _V |, and the electrical angle f1 is equal to or greater than 150 degrees and less than 180 degrees (FIG. 4A).
DI _U <0 dI _V <0 | dI _U | <| dI _V |, and the electrical angle f1 is equal to or greater than 180 degrees and less than 240 degrees (FIG. 4A).
DI _U > 0 dI _V <0 | dI _U | <| dI _V |, and the electrical angle f1 is equal to or greater than 240 degrees and less than 300 degrees (FIG. 4A).
DI _U > 0 dI _V <0 | dI _U |> | dI _V |, and the electrical angle f1 is equal to or greater than 300 degrees and less than 330 degrees (FIG. 4A).
DI _U > 0 dI _V > 0 | dI _U |> | dI _V |, and the electrical angle f1 is equal to or greater than 330 degrees and less than 360 degrees (FIG. 4A).
DI _U > 0 dI _V > 0 | dI _U | <| dI _V |.

The adjustment amount of the offset correction value is determined from the above relationship. As an example, when the electrical angle f1 is in the range of FIG. 4A, the U-phase offset correction error dI _U becomes a negative value, and from equation (3), it is determined that the offset correction value is smaller than the actual offset value. The offset correction value c1 for the U phase is corrected by increasing the current value by a predetermined amount from the current value.
Also, V phase offset correction errors dI _V has a positive value expression
(4) indicates that the offset correction value is larger than the actual offset value, and the offset correction value is adjusted by reducing the V-phase offset correction value c2 from the current value. The correction of these offset correction values is performed by increasing or decreasing the digital values of the outputs of the current detectors 5 and 11 by 1n level (1n bits) and 2n levels (2n bits). (N represents an integer 1, 2, 3,...) Further, the weight when increasing or decreasing the offset correction value is determined from the magnitude relation of the absolute values of the correction errors. If |
Since dI _U | <| dI _V |, the V-phase offset correction value is reduced by the digital value 2n level (2n bits) of the output of the current detector 11, and the U-phase offset correction value is
The digital value of the output is increased by 1n level (1n bits). FIG. 4B shows the amount of adjustment obtained when n = 1 for each range in FIG. 4A.

(Embodiment 2) The configuration of the second embodiment is the same as that of the first embodiment, except that the range in which the electrical angle f1 determined in step S6 in FIG. 3 of the first embodiment exists. It is classified into four. That is, FIG. 5A divides the electrical angle of 360 degrees into four ranges, and the U and V phase offset correction errors dI _U and dI _{V for} each range where the electrical angle f1 exists.
Represents the magnitude relationship between the positive and negative signs and the absolute value. The offset correction error dI _U according to the range in which the electrical angle f1 exists,
relation dI _V is the electrical angle f1 is less than an electrical angle of 330 degrees or more 360 degrees, if less than 0 degrees 60 degrees or more (the range in FIG. _{5A), | dI U | <} | dI V | dI V> 0, the electrical angle When f1 is an electrical angle of 60 degrees or more and less than 150 degrees (range of FIG. 5A), | dI _U |> | dI _V | dI _U <0, and an electrical angle f1 of 150 degrees or more and less than 240 degrees (FIG. 5A)
| DI _U | <| dI _V | dI _V <0, and the electrical angle f1 is equal to or greater than 240 degrees and less than 330 degrees (FIG. 5A).
| DI _U |> | dI _V | dI _U > 0.

The adjustment amount of the offset correction value is determined based on the relationship described above. As an example, the electric angle f1 is shown in FIG.
5A, | dI _U | <| dI _V |, and the V-phase offset correction error dI is considered from FIG. 5A.
_{Since V} is a positive value, the V-phase offset correction value c2 is reduced from the current value. The offset correction value is corrected by increasing or decreasing the digital value of the output of the current detector 11 for each 1n level (1n bits) (n represents an integer). FIG. 5A
FIG. 5B shows the respective offset correction value adjustment amounts when n = 1 for each of the ranges of.

Therefore, according to the above embodiments, when an error occurs in the offset correction value due to a temperature change or the like during operation, the electrical angle detecting means 26 detects the pulsation of the motor generated torque from the torque command value b. Then, an electrical angle f1 when the torque command value is maximum and an electrical angle f2 when the torque command value is minimum are detected by the pulsation component from the electrical angle signal f,
Further, the judging means 27 judges whether or not an offset correction error has occurred based on the angle difference between the electrical angle f1 and the electrical angle f2. Is added, and the offset correction value is updated. As a result, a correction error occurs in the offset correction value due to a rise in the temperature of the elements in the current detectors 5 and 11 due to long-time operation in the servo motor digital controller, and the torque generated by the servo motor 10 becomes equal to the electrical angle. Even when a pulsation occurs in the cycle, the occurrence of an offset correction error can be detected from the pulsation of the torque command value, and the offset correction value can be automatically corrected.

Although the most preferred embodiment of the present invention has been described in some detail, the description of the preferred embodiment is based on the modification of the detailed configuration and the description of the present invention described in the claims. Obviously, various modifications or a combination thereof can be made without departing from the spirit of the invention.

[0025]

As described above, according to the present invention, even if a correction error occurs in the offset correction value due to a temperature rise or the like,
Automatic adjustment of the offset correction value can be performed during operation of the servomotor, torque pulsation generated by the servomotor can be reduced, and deterioration of control performance such as increase in speed ripple can be suppressed.

[Brief description of the drawings]

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

FIG. 2 is a block diagram showing a configuration of an automatic offset correction value adjusting device 4 of FIG. 1;

FIG. 3 is a flowchart showing an arithmetic processing operation in the automatic offset correction value adjusting device 4 of FIG. 2;

FIG. 4A is an electric angle f according to the first embodiment of the present invention.
Value of 1 and offset correction error dI _U, DI_VPositive and negative
FIG. 6B is a diagram showing the magnitude relationship of FIG.
The offset correction value c1 for the U phase and the offset
Showing the adjustment amount of the cut correction value c2

FIG. 5A is an electric angle f in the second embodiment of the present invention.
Value of 1 and offset correction error dI _U, DI_VPositive and negative
FIG. 6B is a diagram showing the magnitude relation of
The offset correction value c1 for the U phase and the offset
Showing the adjustment amount of the cut correction value c2

[Explanation of symbols]

 4 Automatic Offset Correction Value Adjustment Device 5 U-Phase Current Detector with Offset Value 10 Servo Motor 11 V-Phase Current Detector with Offset Value 22 Rotation Detection Means 23 Maximum Value Detection Means 24 Minimum Value Detection Means 25 Electric Angle Counter 26 Electricity Angle detection means 27 Judgment means 28 Electric angle existence range judgment means 29 Offset correction value output means 30 Correction means 31 Initialization means b Torque command value c1 U-phase offset correction value c2 V-phase offset correction value f Electric angle

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yoshihiro Ino 1006 Kadoma Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (58) Field surveyed (Int. Cl. ⁷ , DB name) H02P 5/00 G01R 19/00 H02P 7/36 302

Claims (3)

(57) [Claims] An automatic offset adjusting device for a current detector in a digital control device for a servo motor using a current detector having an offset value, wherein a torque command value and an electrical angle signal of the servo motor are input to an electronic control unit. Rotation detection means for detecting that the rotation is in one direction and the rotation speed is equal to or less than a first set value during one cycle of the air angle; and a torque command value for one cycle of the electrical angle when the rotation detection means detects the rotation. An electrical angle detecting means for detecting a maximum first electrical angle and a minimum second electrical angle; and determining a difference between the first electrical angle and the second electrical angle detected by the electrical angle detecting means. Determining means for determining whether the difference is within the range of the second set value, and determining that the difference between the first electrical angle and the second electrical angle is within the range of the second set value. The current detection according to the first electrical angle. Automatic offset adjustment device of the current detector with a correcting means for correcting the offset correction value. 2. A correction means for correcting an offset correction value of a current detector divides an electrical angle of 360 degrees into eight ranges, and determines an electrical angle existence range determination for determining a range of the first electrical angle. Means, having an offset correction value adjustment amount set in accordance with the eight ranges, updating the offset correction value by adding the offset correction value adjustment amount of the divided range where the first electrical angle exists, 2. The automatic offset adjusting device for a current detector according to claim 1, further comprising: an offset correction value output unit that outputs the updated offset correction value. 3. A correction means for correcting an offset correction value of a current detector divides an electrical angle of 360 degrees into four ranges, and determines an electrical angle existence range determination for determining a range of the first electrical angle. Means, having an offset correction value adjustment amount set in accordance with the four ranges, updating the offset correction value by adding the offset correction value adjustment amount of a divided range where the first electrical angle exists, 2. The automatic offset adjusting device for a current detector according to claim 1, further comprising: an offset correction value output unit that outputs the updated offset correction value.