JPH01268478A - Vector control arithmetic unit for induction motor - Google Patents

Abstract

PURPOSE:To improve cutting accuracy suppressing position error dispersion to a small value, when a C-shaft cutting is performed, by switching a secondary magnetic flux from a weaker variable magnetic flux to a stronger fixed magnetic flux when a main spindle mode is switched to a C-shaft mode. CONSTITUTION:In the time of a main spindle mode, a switch 23 and a switch 25 are set to a position A, and feeding weakening variable magnetic flux, fed from a weakening variable magnetic flux generating circuit 16, to an excitation divider current arithmetic circuit 19, an excitation divider current i'ds is calculated. In the time of a C-shaft mode controlling a position, the switch 23 and the switch 25 are set to a position B, and selecting a position loop while setting secondary magnetic flux phi2 of an electric motor 5 to the fixed magnetic flux fed from a strengthening fixed magnetic flux generating circuit 24, the excitation divider current i'ds is calculated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] This invention relates to a vector control calculation device for an induction motor, and in particular to improving the accuracy of C-cutting for position control.

[Prior Art] Fig. 4 is a block diagram showing an inverter drive device for an induction motor having a vector control calculation device. In the figure, (1) is a three-phase AC power supply, and (2) is a three-phase AC type i1K
1) a converter using a diode or the like to rectify the alternating current sent from the converter (3), a smoothing capacitor to smooth the voltage rectified by the converter (2), and (4)
) is an inverter consisting of transistors, etc. that converts the DC voltage smoothed by a smoothing capacitor (3) into three-phase AC voltage, and (5) is an induction motor (hereinafter referred to as "induction motor") driven by the three-phase AC voltage output by the inverter (4). , an electric motor), and the electric motor (5) is connected to the main shaft of the machine tool.

(6) is a speed detector that is attached to the electric motor (5) and outputs a signal commensurate with its rotational speed, and (7) is a speed detector that is attached to the electric motor (5).
) is a high-resolution position detector that outputs a signal commensurate with its position.

(8) is a numerical control device that outputs the speed command ω" or position command θ" of the electric motor (5), (9) is a speed command creation circuit, and the speed command creation circuit (9) is a numerical control device during speed loop operation. The speed command sent from the device (8) is output as is, and during position loop operation, the speed is calculated by comparing the position command θ8 sent from the numerical control device (8) and the position detection signal θ of the position detector (7). Outputs the command ωゝ. (lO) is the speed "Amplitude 111 of the primary current given to the motor (5) by performing vector control calculation from the speed command ω9 sent from the command generation circuit (9) and the speed detection signal ω of the speed detector (6)
．． A vector control calculation path that outputs angular velocity ω 2 phase angle Δθ, (11) is the amplitude 1 of the primary current sent from the vector control calculation circuit (10). Angular velocity ω 1 phase angle Δ
The -order current reference generation circuit generates the U-phase primary current command l and the ■phase primary current command i s from θ, and (12) is the primary current command sent from the -order current reference generation circuit (11). ! , Ge us
This is a current control circuit that determines whether the transistor of the inverter (4) is turned on or off based on the feedback signal of the primary current flowing through the motor (5).

FIG. 5 shows an internal block diagram of the speed command generation circuit (9) and vector control calculation circuit (step 0) shown in FIG. In the figure (13) is the position command signal θ1 and the position detection signal θ
The difference between the position loop gain and the position loop gain is 1. A position loop gain circuit that multiplies `` to obtain a speed command ω'', (2
3) is a switch for setting during speed loop operation and position loop operation; (14) is a PI control circuit that compares the difference between the speed command ω rate and the speed detection signal ω and calculates 1 and integral control; (15) (16) is a limiter circuit that limits the output of the PI control circuit (14) to a constant saturation value 111aX and uses the torque component current command S; worth it

qs A weakening variable magnetic flux generation circuit that generates secondary magnetic flux φ2, (17) is a first-order lag element that outputs secondary magnetic flux φ1 from secondary magnetic flux φ2, and (1g) is a mutual reactance that generates motor mutual reactance M from φ; (19) is a phase angle calculation circuit that calculates the phase angle Δθ of the primary current S from 19 and 118, (22) is a bow; This is a slip angular frequency calculation circuit that calculates φ2 and slip angular frequency ω8.

Next, the operation will be explained. According to well-known vector control logic, the required torque generated by the motor is TM, and the number of pole pairs is P.
, the actance following the secondary resistance to R is L 1 , the torque component current is 1 , the excitation component current is 2
If the QSids' differential operator is S, the following relational expression holds true.

In vector control, the error between the speed command signal ω* and the speed detection signal ω is amplified by the PI control circuit (14), and the limiter circuit (15) applies a certain limit to the torque current command signal. In addition, the excitation current S calculation circuit (19) uses the speed detection signal ω and the torque current command 19 to calculate the secondary magnetic flux φ obtained at the weakening variable magnetic flux generation port S path (16) from the equation (2). L2/R2
A linear advance calculation is performed with the constant as a constant, and the excitation component current command 'ds is obtained by multiplying by the mutual reactance M obtained from the mutual reactance pattern generation circuit (18). In addition, the slip angular frequency ω can be calculated from equation (3) by dividing the torque component current command 1 by the secondary magnetic flux command φ′ using the angular frequency calculation circuit (22) to obtain the coefficient (R/L2)・M. Obtained by multiplying.

- Amplitude of next current command II 1. Angular frequency ω. .

The phase angle Δθ is determined by the following formula.

II*I (i”)”+(i”)” −(4)l
qs ds ω0-ω, +ω8...(5)-
1,*.

Δθ-tan <198/tds>
-(a) Therefore, in the amplitude calculation circuit (20), equation (4)
The phase angle calculation circuit (21) calculates equation (6).

In the vector control calculation device configured as described above, in the normal spindle operation mode, a speed loop is configured to control the speed of the electric motor (5), and the switch 23 is set to the A side in FIG. Further, in the C-axis mode, a position loop is configured to control the position of the electric motor (5), and the switch 23 is set to the B side.

The responsiveness in this C-axis mode is determined by the position loop gain KPP set in the position loop gain circuit (13) of the speed command generation circuit (9) and the speed set in the PI control circuit (14) of the vector control calculation circuit (10). Loop proportional gain K: Depends on the integral gain. Normally, the value of the position loop P■' loop gain K is set to a value of about 30 sec"-', and the speed P loop proportional gain K and the integral gain are set to 1■ and the speed V is set to a value as large as possible within the range that does not make the control system unstable. This is set to improve responsiveness.

[Problems to be Solved by the Invention] In the conventional vector control calculation device configured as described above, the secondary magnetic flux φ2 of the electric motor (5) is changed from the rated magnetic flux φ2 of about 172 when no load increases as the rated magnetic flux load increases. gradually 100
This is because the excitation current is obtained by determining the weakening variable magnetic flux that increases up to the rated magnetic flux. The speed response of the vector control calculation circuit (10) in the main axis mode and in the C-time mode was the same.

However, when a machine tool is used for C-cutting, the electric motor (
5) Join. For this reason, if the speed response of the electric motor (5) is not excellent, speed fluctuations will occur due to inconsistent external force, and large error variations will occur between the desired commanded position and the actual position, reducing the accuracy of C-axis cutting. There was a problem.

Furthermore, if the depth of cut of the cutting tool into the workpiece is reduced in order to reduce the variation in positional errors, there is also the problem that the cutting limit capability is reduced.

This invention was made to solve the problem of peeling, and improves cutting accuracy during C-axis cutting, which constitutes a position loop that controls the position of the electric motor, and prevents the cutting tool from digging into the workpiece. The object of the present invention is to obtain a vector control calculation device for an induction motor that can improve the cutting limit capacity by the following methods.

[Means for Solving the Problems] A vector control calculation device for an induction motor according to the present invention includes:
The present invention is characterized in that when changing from the main shaft mode to the C-axis mode, the secondary magnetic flux of the induction motor for calculating the excitation current is switched from a weak variable magnetic flux to a strong fixed magnetic flux.

[Function] In this invention, when switching from the main shaft mode to the C-axis mode, the secondary magnetic flux of the induction motor is switched from the weakening variable magnetic flux in the main shaft mode to the stronger fixed magnetic flux, thereby increasing the CIT.
o Increase cutting degree response during cutting.

[Example] FIG. 1 is a block diagram showing one embodiment of the present invention.

The overall configuration of this embodiment is exactly the same as the block diagram shown in FIG. 4. In Figure 1, (9),
(10), (13) to (23) are exactly the same as the conventional example shown in FIG. (24) is an electric motor (5)
(25) is a weak variable magnetic flux generation circuit (16) that makes the secondary magnetic flux φ2 into a strong fixed magnetic flux of 100% of the rated magnetic flux.
) and the stronger fixed magnetic flux generation circuit (24).

The operation of the vector control calculation device configured as described above will be explained with reference to the flowchart shown in FIG.

First, it is necessary to judge whether the f and IJ control of the electric motor (5) is in the spindle mode in which the speed is controlled @IJ or in the C-axis mode in which the position is controlled (step s1). When in the spindle mode, the switch (23) and the switch ( 25) to the A side, select the speed loop with the switch (23), and weaken the secondary magnetic flux φ2 of the motor (5) to weaken the variable magnetic flux sent from the variable magnetic flux generation circuit (1B), i.e. When there is no load, the magnetic flux is approximately 50% of the rated magnetic flux, and as the load increases, the magnetic flux gradually increases to 100% of the rated magnetic flux (Step S3). The excitation component current i♂8 is calculated.

When the control of the electric motor (5) is in the C-axis mode that controls the position, set the switch (23) and the switch (25) to the B side (step s4), select the position loop, and control the electric motor (5). Step S5: Strengthen the secondary magnetic flux φ2 to a stronger fixed magnetic flux sent from the fixed magnetic flux generation circuit (24).
), calculate the excitation component current 'ds.

Here, in the normal spindle mode, the electric motor (5)
In order to reduce the excitation noise of the motor (5), the secondary magnetic flux Φ2 of the electric motor (5) is weakened and made into a variable magnetic flux. The secondary magnetic flux Φ2 of 5) is strengthened and fixed as a fixed magnetic flux to increase the speed response of the vector control calculation circuit (■0).

Figure 3(b) shows the load fluctuations and the torque component current that changes due to the load fluctuations when performing C-axis cutting with the secondary magnetic flux φ2 of the electric motor (5) as 100% rated magnetic flux φ in this embodiment. Command! Figure 3(b) shows the variation in the positional error s and the variation in the positional error s.
5) is a waveform chart showing for comparison the position error when C-axis cutting is performed with the secondary magnetic flux φ2 changing from 50% rating to 100% rating and weakening variable magnetic flux φ. As shown in the figure, according to this embodiment, the positional error and its variation can be made much smaller than in the conventional example.

[Effects of the Invention] As explained above, in this invention, when switching the secondary magnetic flux that determines the magnetic flux of the induction motor from the weak variable magnetic flux to the strong fixed magnetic flux when switching from the main axis mode to the C-axis mode, the C Variations in positional errors during axial cutting can be suppressed to a small level, and cutting accuracy in C-axis cutting can be improved.

Furthermore, since the cutting accuracy is improved, the cutting limit capacity can also be improved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a flowchart showing the operation of the above embodiment, and FIG. 3(a)
, (b) is a waveform comparison diagram of the position error between the conventional example and the above embodiment, FIG. 4 is a block diagram showing an inverter drive device for an induction motor having a vector control calculation device, and FIG. 5 is a block diagram of the conventional example. be. (9)... Speed command generation circuit, (lO)... Vector control calculation circuit, (16)... Variable weakening magnetic flux generation circuit, (19)... Excitation component current calculation circuit, (23),
(25)...Switch, (24)...Strengthening fixed magnetic flux generation circuit. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] In a vector control calculation device that separates and controls a primary current given to an induction motor into a torque component current and an excitation component current, the secondary magnetic flux of the induction motor is controlled in a C-axis mode for position control. A vector control calculation device for an induction motor, characterized in that an excitation component current is obtained as a strong fixed magnetic flux.