JPH09285200A - Current control system for servomotor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease a D-phase current generated by an interference item with D-phase voltage by a Q-phase current, so that high speediness of control can be performed, by providing a means correcting interference with the D-phase voltage by the Q-phase current. SOLUTION: DQ control performed of a current control system of a survomotor by a DC system is performed, further, in an interference correction item 17, a Q-phase current command Iq* is input, a value multiplying it by an angular speed ω and inductance L of one phase component is output as correction voltage. When a change of a Q-phase current, such as reapidly decelerating from a high speed rotational condition, is generated, by adding this correction voltage to a D-phase voltage command interference voltage, generated in a D phase side by the Q-phase current, is corrected by an interference item 15, an increase of a D-phase current, which is a reactive current, is suppressed. In this way, even at high speed rotation time, control preventing a reactive current from flowing can be performed, high speediness of motor control can be performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current control method for an AC servomotor used as a drive source for a mechanical device such as a machine tool or an industrial machine or a robot.

[0002]

2. Description of the Related Art FIG. 11 is a block diagram of a conventional control system for an AC servomotor. The position feedback value detected by the encoder etc. is subtracted from the position command to obtain the position deviation, the position deviation is multiplied by the position gain to perform the position loop control to obtain the speed command, and the speed feedback value is subtracted from the speed command. Obtain the speed deviation, perform speed loop processing such as proportional / integral control, and obtain the current command (torque command). Further, the current feedback value is subtracted from this current command (torque command) to perform current loop processing to obtain a voltage command for each phase and PWM control or the like is performed to control the AC servomotor M.

In such a control system, as a current loop, in the case of a three-phase AC servomotor, an AC current control system is known in which three-phase currents are separately controlled. In such a current control method, the electric current angle (torque command) obtained in the speed loop process is 2π / Electrical angle for the U, V, and W phases from the rotor position θ of the servo motor detected by the encoder or the like. 3 The current command for each phase is obtained by multiplying the shifted sine waves, the actual current Iu, Iv, Iw of each phase detected by each current detector is subtracted from the current command to obtain the current deviation, and the current controller for each phase is obtained. Proportional-integral (PI) control or the like is performed using Iu, Iv, and Iw to output the phase command voltages Eu, Ev, and Ew to the power amplifier. In the power amplifier, PWM control is performed by an inverter or the like, and the currents Iu, Iv, and Iw of each phase are supplied to the servomotor M for driving. As a result, a current loop is formed in the innermost minor loop of the position / speed loop,
The current loop controls the current flowing through each phase of the AC servomotor.

In the case of controlling the three-phase currents separately, the frequency of the current command also increases as the rotation speed of the motor increases, and the current phase gradually delays, increasing the reactive component of the current and increasing the torque. It has the drawback that it cannot be generated efficiently.Because AC is handled as the controlled variable, even in the steady state at constant speed rotation and constant load, there is no delay in phase with respect to the command, attenuation of amplitude, etc. There is a deviation, and it is difficult to achieve torque control equivalent to that of a DC motor. As a method of remedying this drawback, a DQ control method is known in which three-phase currents are DQ-converted into two-phase DC coordinate systems of D-phase and Q-phase, and then each phase is controlled by a DC component.

FIG. 12 is a control block diagram of an AC servomotor according to the DQ control method. In the DQ control method, the current command of the D phase that is the reactive current component is set to “0”, and the current command of the Q phase that is the active current component is set as the current command (torque command) output by the speed loop. And from the three-phase current to 2
In the converter 9 for converting into a phase current, each u,
Using the actual currents of the v and w phases and the rotor phase detected by the rotor position detector, the currents Id and Iq of the D phase and Q phase are obtained, and this current is subtracted from the current command value of each phase to obtain the D phase. , Q
Calculate the phase current deviation. The current controllers 5d and 5q perform proportional / integral control of this current deviation to obtain the D-phase command voltage Vd and the Q-phase command voltage Vq. The means 8 for converting the two-phase voltage into the three-phase voltage is the D-phase command voltages Vd and Q of the two phases.
Three-phase command voltage V of u, v, w phases from the phase command voltage Vq
u, Vv, and Vw are obtained, output to the power amplifier 6, and currents Iu, Iv, and Iw are supplied to each phase of the servomotor by PWM control by an inverter or the like to control the servomotor. Generally, an equivalent circuit when the DQ conversion method is applied can be expressed by the following equation (1),

[0006]

[Equation 1] Further, the conversion formula from the three-phase current to the two-phase current and the conversion formula from the two-phase voltage to the three-phase voltage can be expressed by the following formulas (2) and (3).

[0007]

[Equation 2] FIG. 13 is a block diagram for explaining a conventional AC servomotor according to the DQ control method. In FIG.
The D-phase controller and the Q-phase controller have an integral term 1
1, 12 (K1 is an integral gain) and proportional terms 13, 14 (K
Reference numeral 2 is a control system having a proportional gain, and the motor side has a resistance component R and an inductance component L. Also, each D
The phase and the Q phase have interference terms 15 and 16 from the other phases.

The interference term 15 is an interference term from the Q phase to the D phase, and the value obtained by multiplying the Q phase current by the angular velocity ω and the inductance value for one phase of the motor interferes in the negative direction with respect to the D phase voltage. Further, the interference term 16 is an interference term from the D phase to the Q phase, and the value obtained by multiplying the D phase current by the angular velocity ω and the inductance value for one phase of the motor interferes with the Q phase voltage in the positive direction. .

[0009]

However, in the conventional servo motor current control method, the interference voltage to the D-phase voltage due to the Q-phase current is not corrected, and the D-phase which is a reactive current due to the interference voltage is not corrected. There is a problem that the current becomes large.

As described above, when the servo motor is controlled by the DQ control method, the Q-phase current has an interference term in the D-phase voltage and the D-phase current has an interference term in the Q-phase voltage. This interference term exists steadily, but since it is added to the voltage command of each phase as a voltage disturbance in each phase,
When a time equal to or longer than the time constant of the current loop has passed, the disturbance component due to the interference term is suppressed by the disturbance suppression characteristic provided in the current loop. However, in the transient state, each phase is affected by the interference term.

In current control using DQ conversion,
Since the D-phase current in the same direction as the magnetic flux direction is set to “0” and the Q-phase current Iq orthogonal to the D-phase current Id is controlled so as to follow the torque command, Id = 0, Iq>, and in the positive direction. Since the rotor is rotating and accelerating, the angular velocity ω of the rotor is positive. Therefore, the D-phase voltage and the Q-phase voltage are represented in a vector diagram as shown in FIG. The phase θ is tan θ = Vd /
There is a relationship of Vq. As shown in the equation (1) of the DQ conversion, the value (Iq ×) obtained by multiplying the Q-phase current Iq by the angular velocity ω and the inductance L for one phase due to voltage interference in the motor.
An interference voltage of ωL) is generated on the D phase side and balances with the D phase voltage as shown in FIG. In the current control system based on DQ conversion, the D-phase current command for flowing the reactive current is normally set to 0, and the current control is performed by the Q-phase current command. Therefore, in general D
The phase current is small and the Q-phase current is large. Therefore,
The influence of the D-phase voltage interference term due to the Q-phase current becomes a greater problem than the Q-phase voltage interference term due to the D-phase current. Also,
Since this interference term depends on the angular velocity ω, the influence of the interference term becomes large at high speed. Furthermore, the influence of this interference term becomes a problem transiently in the region as described above.

Therefore, the interference term has a great influence when the Q-phase current changes such that the angular velocity ω is rapidly decelerated from the high-speed rotation state. For example, as shown in FIG. 16A, at high speed rotation, since the angular velocity ω is large, the D-phase voltage that balances the interference voltage generated by this angular velocity ω also becomes large. At this time, if sudden deceleration is performed, FIG.
The interference voltage component (Iq ×
ωL) becomes smaller. At this time, it takes time for the D-phase voltage command to decrease due to the control of the current loop.
A voltage of Vd 'is generated on the D phase side. This D-phase side voltage V
A d-phase current is generated by d '. When a time equal to or longer than the time constant of the current loop has passed, the disturbance component due to the interference term is suppressed by the disturbance suppression characteristic provided in the current loop, and the D-phase current is suppressed as shown in FIG. 16 (c).

In this way, the disturbance voltage is applied to the D-phase voltage during the transition until the influence of the interference voltage is suppressed by the D-phase current loop, so that the D-phase current is controlled to be zero. Nevertheless, the D-phase current, which is a reactive current, will flow. This indicates that in the conventional control method, it is difficult to speed up the transient response at high speed rotation in motor control, and it is difficult to speed up the control. It should be noted that, after a lapse of a predetermined time, the D-phase current decreases due to the disturbance suppression characteristic of the current loop. Therefore, the present invention solves the conventional problems described above, and in the current control of the servo motor by the DQ control, the D-control by the Q-phase current is performed.
The purpose is to reduce the D-phase current generated by the interference term to the phase voltage and speed up the control.

[0014]

According to the present invention, the D-phase current in the magnetic flux direction created by the field and the Q-phase current orthogonal to the D-phase current are obtained by DQ conversion from the drive current of the servo motor and the rotor phase. In the DQ control method in which the phase current is set to zero and the Q-phase current is used as the current command, and the current control system of the servo motor is a direct current method, when the Q-phase current changes such that it rapidly decelerates from the high-speed rotation state, the Q-phase current Is used to correct the interference voltage generated on the D phase side and suppress the increase of the D phase current, which is a reactive current, thereby speeding up the current control, and the Q phase current interferes with the D phase voltage. A means for correcting is provided. The interference correction means has a function of canceling the interference voltage generated on the D phase side by the Q phase current.

According to the current control method of the present invention, a value obtained by multiplying the interference correction means for correcting the interference of the Q-phase current with the D-phase voltage by the Q-phase current command by the angular velocity and the inductance value of one phase of the motor is used. A function to add to the voltage command is provided, the Q-phase current command and the angular velocity of the motor are input, a value is obtained by multiplying the Q-phase current command by the angular velocity and the inductance value for one phase of the motor, and this value is used as the interference voltage. In addition to the D-phase voltage command as the correction voltage to be canceled, the interference voltage is canceled by this. By using the Q-phase current command, interference correction can be performed earlier than the Q-phase current that generates the interference voltage, and a feedforward-like cancellation effect can be obtained.

Further, the interference correction means includes a delay means for delaying the Q-phase current command for a predetermined time, and the Q delayed for a predetermined time.
The phase current command is multiplied by the angular velocity and the inductance value for one phase of the motor, and the obtained value is added as a correction voltage to the D phase voltage command to cancel the interference voltage. By providing this delay means, it is possible to correct a slight advance of the correction timing that occurs when the interference correction voltage is formed using the Q-phase current command that is not delayed. A low-pass filter can be used as the delay unit, and the correction timing can be adjusted by adjusting the time constant of the low-pass filter.

[0017]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram for explaining an embodiment of the present invention, and FIG. 2 is a diagram for explaining voltage states of a D phase and a Q phase according to the embodiment of the present invention. In the block diagram of FIG. 1, the D-phase controller and the Q-phase controller are integrated terms 11, 12
(K1 is an integral gain) and a proportional system 13 and 14 (K2 is a proportional gain), and the motor side is provided with a resistance component R and an inductance component L. Also, each D phase, Q
The phases have interference terms 15, 16 from each other.
This configuration is common to the conventional block diagram shown in FIG.

In the block diagram of FIG. 1, the current control system of the present invention comprises an interference correction term 17 which is a means for correcting the interference of the Q-phase current with the D-phase voltage. Then, the D-phase current in the magnetic flux direction created by the field and the Q-phase current orthogonal to the D-phase current are obtained by DQ conversion from the drive current of the servo motor and the rotor phase by the configuration for performing the normal DQ control. Is set to zero and the Q-phase current is used as a current command to perform DQ control in which the current control system of the servo motor is a direct current system. Further, the interference correction term 17 inputs the Q-phase current command Iq * and inputs the angular velocity to the Q-phase current command Iq *. A value obtained by multiplying ω by the inductance L for one phase is output as a correction voltage. And
By adding this correction voltage to the D-phase voltage command, the interference voltage generated by the Q-phase current on the D-phase side is corrected by the interference term 15 when a change in the Q-phase current that causes rapid deceleration from the high-speed rotation state occurs. However, the increase of the D-phase current, which is a reactive current, is suppressed.

The change state of the D-phase voltage due to the interference correction term 17 will be described with reference to FIG. The interference term 15 has a great influence on the D-phase voltage when there is a Q-phase current change such as a rapid deceleration from a high-speed rotation state where the angular velocity ω is large. As shown in FIG. 2A, the angular velocity ω during high-speed rotation
Is large, the interference voltage (Iq × ωL) generated in the interference term 15 increases due to this angular velocity ω, and the D-phase voltage that balances this interference voltage also increases. When sudden deceleration is performed from such a high speed rotation, the angular velocity ω becomes small, so that FIG.
As shown in (b), the interference term 15 reduces the interference voltage (Iq × ωL) generated on the D phase side by the Q phase current Iq. At this time, since it takes time for the D-phase voltage command to decrease due to the control of the current loop, a large D-phase voltage Vd
Is added, and a voltage of Vd ′ that generates a D-phase current is generated on the D-phase side.

Here, in the control system of the present invention, a value (Iq * × ωL) obtained by multiplying the Q-phase current command Iq * by the angular velocity ω and the inductance L for one phase is used as the D-phase voltage with the opposite sign to the interference correction voltage. Control is performed. As a result, in the voltage on the D phase side, as shown in FIG. 2B, the interference voltage (Iq
(Iq * × ωL) is subtracted from (× ωL), which suppresses the voltage of Vd ′ that generates the D-phase current. In the control method of the present invention, the interference correction voltage for canceling the interference voltage is set to Q instead of the feedback value Iq of the Q-phase current.
It is formed by using the phase current command Iq *, and by this, the correction timing is advanced and feedforward cancellation is performed, whereby the feedback value Iq of the Q phase current is generated.
Compensates for the delay when using. After that, when a time equal to or longer than the time constant of the current loop elapses, the disturbance component due to the interference term is suppressed by the disturbance suppression characteristic provided in the current loop, and the D-phase current is suppressed as shown in FIG. 2C. .

As described above, the disturbance voltage generated in the D-phase voltage is corrected during the transition until the influence of the interference voltage is suppressed by the D-phase current loop, and the D-phase current generated by the disturbance voltage is suppressed. The control is performed so that the D-phase current, which is a reactive current, does not flow. This makes it possible to perform control so that no reactive current flows even during high-speed rotation, and it is possible to speed up motor control.

FIG. 3 is a block diagram of a servo motor control system to which the embodiment of the present invention is applied. Since this configuration is the same as that of a conventional device for performing digital servo control, it is schematically shown. In FIG. 3, 20 is a numerical controller (CNC) with a built-in computer, 21 is a shared RAM, and 2 is a shared RAM.
Reference numeral 2 is a digital servo circuit having a processor (CPU), RON, RAM, etc., 23 is a power amplifier such as a transistor inverter, M is an AC servo motor, 24 is an encoder that generates a pulse as the AC servo motor M rotates, and 25 is a rotor. It is a rotor position detector for detecting a phase.

Next, the current loop control process executed by the processor of the digital servo circuit 22 every predetermined period will be described with reference to the flowchart of FIG. The processor of the digital servo circuit 22 shares the position command (or speed command) commanded by the numerical controller (CNC) RA
Reading position loop processing and speed loop processing are performed via M21.

First, the current command (torque command) Iq * is calculated by speed loop processing (step S1), and the rotor position detector 25 detects the rotor phase θ and the motor speed w.
Is taken in (step S2). Next, the actual currents Iu, Iv of the U and V phases detected by the current detector are fetched as current feedback (step S3), and the fetched U phase,
The V-phase actual currents Iu and Iv and the rotor phase θ are substituted into the equation (2) by DQ conversion to calculate the D-phase and Q-phase currents Id and Iq (step S4).

The control by digital processing for each processing cycle will be described below. Regarding the Q-phase current command obtained in step S4, the Q-phase current command TCMDQ for each processing cycle
(N) is calculated (step S5). On the other hand, the D-phase current command TCMDD (n) for each processing cycle is set to zero (step S6).

Q-phase current command TCMDQ (n) and D-phase current command TCMD determined in steps S5 and S6
For D (n), the D-phase current Id is used as a feedback current, and the D-phase current command TCMDD (n) is set to “0”.
-Proportional integral calculation of the current loop process by the P compensator is performed to obtain the D-phase voltage command UCMDD, and step S5
Q-phase current command TCMDQ (n) obtained in step S
The Q-phase current value Iq calculated in 4 is used as a feedback current to perform a current loop process to obtain a Q-phase voltage command UCMDQ (step S7).

Next, the Q-phase current command TCMDQ (n) obtained in step S5 is multiplied by the angular velocity ω and the inductance L for one phase to obtain an interference correction voltage, and this interference correction voltage is obtained in step S7. D-phase voltage command UCMDD
D-phase voltage command UC with interference correction
MDD (= UCMDD + TCMDQ (n) × ωL) is calculated (step S8).

Q-phase voltage command UCM obtained in step S7
DQ and D-phase voltage command UCM corrected for interference in step S8
DD is substituted for Vq and Vd in the equation (3), DQ conversion is performed, and voltage command values for the U, V, and W phases are obtained (step S
9), the voltage command is output (step S10), and the current loop process of the period is finished.

Next, a second embodiment of the present invention will be described with reference to the block diagram of FIG. The second embodiment shown in FIG. 5 is configured such that, as the interference correction means in the first embodiment described above, a delay means for delaying the Q-phase current command by a predetermined time is provided before the interference correction term 17. By providing this delay means, a slight advance of the correction timing that occurs when the interference correction voltage is formed using the Q-phase current command that is not delayed is corrected. Since the configuration of the second embodiment is the same as the configuration of the first embodiment except for the delay means, only different components will be described, and other common configurations will be described. Is omitted.

In FIG. 5, the delay means for delaying the Q-phase current command by a predetermined time is constituted by the delay term 18, the Q-phase current command is inputted and delayed by a predetermined delay time, and the delayed Q-phase current command is delayed. Output to the interference correction term 17. The delay term 18 can be configured by, for example, a low pass filter having a time constant λ.

When the low-pass filter is digitally processed, the Q-phase current command input every predetermined period is TC.
Set MDQ (n) and filter output as FILTOUT (n)
And the constant determined by the time constant of the filter is λ, the filter output FILTOUT (n) is expressed by the following equation (4).

FILTOUT (n) = λFILTOUT (n−1) + (1−λ) TCMDQ (n) (4) Note that FILTOUT (n−1) is FILTOUT.
It shows the filter output one sample time before (n).

The interference correction term 17 receives the filter output FILTOUT (n) delayed by the low-pass filter, multiplies it by the angular velocity ω and the inductance L for one phase, and outputs (FILTOUT (n) × ωL). Then, this output is added to the D-phase voltage command as an interference correction voltage, and the first
Interference correction is performed in the same manner as in the above embodiment.

Next, the current loop control processing executed by the processor of the digital servo circuit 22 in each predetermined cycle in the second embodiment will be described with reference to the flowchart of FIG. In the flowchart of FIG. 6, steps S11 to S16 are the same as the processing of the first embodiment shown in FIG. 5, and the Q-phase current command TCMDQ (n) is calculated in the steps up to step S16. D
The phase current command TCMDD (n) is set to zero.

Next, the Q-phase current command TC by the delay term 18
MDQ (n) delay processing is performed. This delay processing is performed by the filter processing using the above-mentioned equation (4), and
Q-phase current command TCMDQ obtained in step S15
(N) and filter output FILTOU one sample time before
By substituting T (n-1) with the filter output F
Calculate ILTOUT (n).

Here, for example, the period Ts of the current loop is 2
The cutoff frequency f of the low-pass filter is 183H at 50 μs.
In the case of z, λ, the period Ts of the current loop, and the cutoff frequency f have the relationship of the following equation (5), and therefore λ = exp (−2πfTs) (5) λ is 0.75 ( = Exp (-2π × 183 × 250 × 1
0 ^-6 )). Therefore, the equation (4) at this time is represented by the following equation (6). FILTOUT (n) = 0.75 × FILTOUT (n−1) + 0.25 × TCMDQ (n) (6) By calculating the above formula (6), the cycle Ts of the current loop as the delay term 18 is 250 μs. Q-phase current command FILTOUT for interference correction when using a low-pass filter having a cut-off frequency f of 183 Hz
(N) can be obtained (step S17).

Next, the Q-phase current command FILTOUT (n) for interference correction obtained in step S17 and step S
For the 16 D-phase current command TCMDD (n), the D-phase current Id is used as a feedback current and the D-phase current command TCMDD (n) is set to “0”, as in step S7.
The D-phase voltage command UCMDD is obtained by performing the proportional-plus-integral calculation of the current loop processing by the IP compensator, and step S
The Q-phase current command TCMDQ (n) obtained in step 17 and the Q-phase current value Iq calculated in step S14 are used as feedback currents for current loop processing to perform the Q-phase voltage command UCM.
DQ is calculated (step S18).

Next, the interference correction voltage is obtained by multiplying the Q-phase current command FILTOUT (n) obtained by delaying in step S17 by the angular velocity ω and the inductance L for one phase,
The interference correction voltage is added to the D-phase voltage command UCMDD obtained in step S18 to perform interference correction, and the D-phase voltage command UCMDD (= UCMDD + FILTOU
T (n) × ωL) is calculated (step S19).

Q-phase voltage command UC obtained in step S18
MDQ and D-phase voltage command U that has been subjected to interference correction in step S19
Substituting CMDD and Vq and Vd in the equation (3) for DQ conversion to obtain voltage command values for the U, V, and W phases (step S20), and outputting the voltage command (step S21). The current loop processing of the cycle is ended.

Next, the servo motor current control method of the present invention and the conventional current control method will be compared using the experimental results of FIGS. 7 to 10 show feedback currents of the D phase and the Q phase when the rapid deceleration is performed from 3000 rpm, FIG. 7 is an experimental result when the interference correction of the present invention is not applied, and FIG. FIG. 9 shows an experimental result when the Q-phase current command is subjected to interference correction by applying the first embodiment of the invention, and FIG. 9 shows a result obtained by applying the first embodiment of the present invention.
FIG. 10 shows an experimental result when the Q-phase current command delayed by the 83 Hz ropes filter is subjected to the interference correction, and FIG. 10 is an experimental result when the Q-phase feedback current is used to perform the interference correction. In addition, one scale on the horizontal axis of the drawing indicates 10 ms.

Comparing FIG. 7 and FIG. 8, looking at the D-phase current when the speed is rapidly decelerated from the high-speed rotation, when the Q-phase current command is subjected to interference correction by applying the first embodiment of the present invention. In addition, the generation of the D-phase current is suppressed as compared with the case where the interference correction is not performed (see a in FIG. 7 and b in FIG. 8). Further, by comparing FIG. 8 and FIG. 9 and observing the D-phase current when the speed is rapidly decelerated from the high-speed rotation, interference is caused by using the delayed Q-phase current command by applying the second embodiment of the present invention. In the case of correction, the whiskers are reduced (see c in FIG. 8 and d in FIG. 9) as compared with the case without delay, and the generation of the D-phase current is further suppressed (b in FIG. 8).
And e in FIG. 9).

FIG. 10 shows the case where a Q-phase feedback current is used as the Q-phase current used for forming the interference correction voltage. At this time, the timing of interference correction is the Q-phase current command according to the current control method of the present invention. Since it is later than the case where it is used, suppression of the D-phase current is seen after a while from the rapid deceleration process (see f in FIG. 10). This is because even if the D-phase voltage command is changed after detecting the flow of the Q-phase current, the interference correction timing is delayed and the canceling effect is delayed.

[0043]

As described above, according to the present invention,
In the current control of the servomotor by the DQ control, it is possible to reduce the D-phase current generated by the interference term of the Q-phase current to the D-phase voltage and speed up the control.

[Brief description of drawings]

FIG. 1 is a block diagram for explaining an embodiment of the present invention.

FIG. 2 is a diagram illustrating voltage states of a D phase and a Q phase according to the embodiment of the present invention.

FIG. 3 is a block diagram of a servo motor control system to which an embodiment of the present invention is applied.

FIG. 4 is a flowchart of a current loop control process executed by the processor of the digital servo circuit at every predetermined cycle.

FIG. 5 is a block diagram for explaining a second embodiment of the present invention.

FIG. 6 is a flowchart of a current loop control process executed by the processor of the digital servo circuit in every predetermined cycle in the second embodiment of the invention.

FIG. 7 is an experimental result when the interference correction of the present invention is not applied.

FIG. 8 is an experimental result when the Q-phase current command is subjected to interference correction by applying the first embodiment of the present invention.

FIG. 9 is an experimental result when the interference correction is performed on the delayed Q-phase current command by applying the first embodiment of the present invention.

FIG. 10 is an experimental result when interference correction is performed using a Q-phase feedback current.

FIG. 11 is a block diagram of a control system of an AC servo motor that has been conventionally performed.

FIG. 12 is a control block diagram of an AC servomotor according to a DQ control method.

FIG. 13 is a block diagram for explaining a conventional AC servomotor according to a DQ control method.

FIG. 14 is a vector diagram showing a D-phase voltage and a Q-phase voltage.

FIG. 15 is a diagram showing a D-phase voltage and a Q-phase voltage.

FIG. 16 is a diagram illustrating voltage states of a D phase and a Q phase at the time of sudden deceleration.

[Explanation of symbols]

 1 Position Control Block 2 Speed Control Block 3 Current Control Block 4,24 Servo Motor 5d, 5q Current Controller 6,23 Power Amplifier 7 Rotor Phaser 8 Means for Converting 2-Phase Voltage to 3-Phase Voltage 9 3-Phase Current to 2 Means for converting to phase current 11,12 Integral term 13,14 Proportional term 15,16 Interference term 17 Interference correction term 18 Delay term 20 CNC 21 Shared memory 22 Digital servo circuit 25 Encoder 26 Position detector

Claims (4)

[Claims] 1. A servomotor current control system, comprising:
The D-phase current in the magnetic flux direction created by the field and the Q-phase current orthogonal to the D-phase current are obtained by DQ conversion from the drive current of the servo motor and the rotor phase, and the D-phase current is set to zero and the Q-phase current is used as the current command. A current control method for a servo motor, comprising a means for correcting interference with a D-phase voltage due to a Q-phase current. 2. The interference correction means sets a value obtained by multiplying the Q-phase current command by an angular velocity and an inductance value for one phase of the motor as D.
The current control system for a servomotor according to claim 1, wherein the current control system is added to the phase voltage command. 3. The current control system for a servomotor according to claim 2, wherein the interference correction means includes a delay means for delaying the Q-phase current command for a predetermined time. 4. The current control system for a servo motor according to claim 3, wherein the delay means is a low-pass filter.