JPH08322299A - Vector control system of motor - Google Patents

Abstract

PURPOSE: To provide the vector control system of a motor which facilitates the high precision control with a small memory capacity. CONSTITUTION: A sine waveform table 31 outputs an address DAT corresponding to the upper digits of an electrical angle θwhich is detected by a pole position calculating unit 4 and trigonometric function values SINA and SINB corresponding to addresses adjacent to the address DAT. An interpolation processing unit 32 corrects the trigonometric function values SINA and SINB which are outputted from the sine waveform table 31 by using an interpolation coefficient DLT corresponding to the lower digits of the electrical angle θ which is detected by a pole position calculating unit 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vector control system of a motor for highly accurately controlling a three-phase synchronous motor, a three-phase induction motor and the like used in coordinate measuring machines and machine tools.

[0002]

2. Description of the Related Art In the vector control system of a synchronous servo motor, an electrical angle based on the magnetic pole position of a rotor is detected, and from this electrical angle, two orthogonal axis components of the rotor, that is, d of armature current is detected.
The axis current component and the q-axis current component are calculated, and the error between these current components and the current command value of each axis is detected to control the three-phase voltage command value of the motor. A trigonometric function is used to calculate each axis current component from the electrical angle, but a DSP (Digita) that does not have a trigonometric function calculation command is used.
Since it takes a long time to perform a calculation when a calculation is performed using a signal processor, etc., a trigonometric function value is usually generated by referring to a trigonometric function table or the like.

When highly accurate vector control is required in a coordinate measuring machine or machine tool, it is necessary to increase the detection resolution of the electrical angle of the rotor and generate trigonometric function values at fine intervals. In the former case, for example, the magnetic pole position of the rotor is detected by a magnetic pole sensor at every 60 electrical degrees, and the electrical angle is detected from the relative count value of the incremental encoder from the change point of the signal of the magnetic pole sensor. ing. As a result, the detection resolution of the electrical angle per magnetic pole can be increased to several hundreds of thousands of pulses.

[0004]

However, in the above-described conventional vector control system for a motor, even if the detection resolution of the electrical angle per magnetic pole pair is increased, the trigonometric function is equivalent to the number of pulses for one cycle of the electrical angle. If a table memory is to have a value, as shown in the following table, the memory capacity consumed in the table becomes enormous, and there is a problem that the cost is high.

[0005]

[Table 1]

The present invention has been made in view of the above problems, and an object of the present invention is to provide a vector control system for a motor, which enables a highly accurate control with a small memory capacity.

[0007]

A vector control system for a motor according to the present invention corresponds to an electric angle detecting means for detecting an electric angle of a rotor of the motor and an electric angle detected by the electric angle detecting means. Trigonometric function generating means for outputting a trigonometric function value, current detecting means for detecting a three-phase current value supplied to the motor, three-phase current value detected by the current detecting means and output from the trigonometric function generating means. And a three-phase / two-phase conversion means for calculating a two-phase feedback current corresponding to the two orthogonal axes of the rotor from the trigonometric function value.
Two-phase feedback current calculated by the two-phase conversion means and 2
Two-phase / two-phase voltage command value is calculated from the error detection means for detecting an error from the phase current command value, and the error output from this error detection means and the trigonometric function value output from the trigonometric function generation means. In the vector control method of a three-phase motor, which comprises a three-phase conversion means and supplies a three-phase AC voltage to the motor based on a three-phase voltage command value output from the two-phase / 3-phase conversion means, the trigonometric function The generating means includes a trigonometric function table for outputting a trigonometric function value of an address corresponding to a higher digit of the electrical angle detected by the electrical angle detecting means and an address adjacent to the address, and the electrical angle detected by the electrical angle detecting means. Interpolation processing means for correcting the trigonometric function value read out from the trigonometric function table by using the value corresponding to the lower digit of the interpolation coefficient as an interpolation coefficient.

[0008]

According to the present invention, the trigonometric function table is read by referring to the address corresponding to the upper digit of the electrical angle of the rotor detected by the electrical angle detecting means and the address adjacent thereto, and reading the trigonometric function value. It is corrected by interpolating the trigonometric function value by the interpolation processing means. Therefore, even if the trigonometric function value stored in the trigonometric function table is small, a fine trigonometric function value can be obtained by the interpolation processing. Since the two-phase feedback signal and the three-phase voltage command value are obtained using the obtained trigonometric function value, highly accurate vector control can be realized with a small memory capacity.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a third embodiment according to the present invention.
It is a block diagram showing composition of a vector control device of a phase synchronous motor.

A magnetic pole sensor 2 and an incremental encoder 3 are connected to a three-phase synchronous motor 1 to be controlled via its rotor shaft. The magnetic pole sensor 2 detects the magnetic pole position of the motor 1 at a constant angle, and for example, a three-phase pulse signal φ that is turned on / off every 60 ° electrical angle.
u, φv, and φw are supplied to the magnetic pole position calculation unit 4. Also,
The incremental encoder 3 has a phase difference of 90 ° at a finer pitch than the pulse signal of the magnetic pole sensor 2.
The phase pulse signals PA and PB are supplied to the magnetic pole position calculation unit 4.

The magnetic pole position calculator 4 calculates the current magnetic pole position (electrical angle θ) from the electrical angle calculated from the output change point of the magnetic pole sensor 2 and the count value of the output pulse of the incremental encoder 3. The trigonometric function generation unit 5 obtains a value corresponding to sin θ from the electrical angle θ calculated by the magnetic pole position calculation unit 4 by table reference and interpolation processing.

A current command value Id * of a d-axis current component (exciting current component) along the magnetic pole axis of the armature current and a current command value Iq of a q-axis current component (torque current component) orthogonal to the magnetic pole axis.
* Is input to one input terminal of each of the subtracters 6a and 6b. At the other input terminals of the subtracters 6a and 6b,
Feedback current values Id and I corresponding to the above-mentioned two-axis components
q is input respectively. The error between each current command value output from the subtracters 6a and 6b and the feedback current is input to the three-phase / two-phase conversion unit 8 via the buffers 7a and 7b, respectively. The 3-phase / 2-phase converter 8 is d
Based on the axis and q-axis current command values Id *, Iq *, the feedback currents Id, Iq, and the triangular angle value sin θ output from the trigonometric function generator 5, the three-phase voltage command value Vu
Calculate c, Vvc, Vwc. PMW inverter 9
Turns on / off an internal switching element (not shown) based on the three-phase voltage commands Vuc, Vvc, Vwc to convert the DC power into AC power, and obtains the obtained three-phase AC voltages Vu, Vv, Vw is supplied to the motor 1.

Of the three-phase current supplied to the motor 1, U
The current values Iu and Iv of the phase and V phase are detected by
detected by b, supplied to the AD converter 11, AD-converted into digital values DIu and DIv, and three-phase / two-phase converter 12
Is supplied to. The 3-phase / 2-phase conversion unit 12 uses the current value DI
Feedback currents Id and Iq are calculated from u and DIv and the trigonometric function value sin θ supplied from the trigonometric function generator 5, and are supplied to the subtractors 6a and 6b.

Next, the operation of the vector control device for the motor thus constructed will be described. Assuming that the electric angle of the rotor of the motor 1 is θ, the d-axis component Id and the q-axis component Iq of the armature current can be calculated by the following mathematical formula 1.

[0015]

Id = √2 [DIv · sin θ−DIu · sin (θ + 4π / 3)] Iq = √2 [DIu · sin (θ + 11π / 6) −DIv · sin (θ + π / 2)]

On the other hand, the d and q axis components Id and I of the armature current
q and d, q-axis voltage command values Vd *, Vq * corresponding to the difference between q-axis current command values Id *, Iq * (buffer 7
The voltage command values Vuc, Vvc, Vwc can be obtained from the following Equation 2 from the outputs a, 7b) and the electrical angle θ of the rotor of the motor 1.

[0017]

[Formula 2] Vuc = √2 [Vq * · sin θ + Vd * · sin (θ + π / 2)] Vvc = √2 [Vq * · sin (θ + 4π / 3) + Vd * · sin (θ + 11π / 6)] Vwc = −Vuc -Vvc

Therefore, the control performance of the motor 1 largely depends on the resolution of the electrical angle θ of the rotor and the accuracy of the trigonometric function value sin θ corresponding to this electrical angle θ.

Now, for convenience of explanation, the number of magnetic pole pairs p of the rotor is p.
2 is set to 1 as shown in FIG.
Three-phase pulse signals φu, φv, and φw as shown in FIG. 3 are output to detect the magnetic pole position at every 0 °. By detecting the rising or falling edge of the output pulse of the magnetic pole sensor 2, the electrical angle θ is 60 °, 120 °
The time points of °, 180 °, 240 ° and 300 ° can be detected. The output pulse signals PA and PB of the incremental encoder 3 are used to detect the fine electrical angle Δθ between them. When the number of magnetic pole pairs p of the rotor is 2 or more, the magnetic pole sensor 2 detects the magnetic pole position every 60 ° / p.

FIG. 4 shows the current electrical angle θ and its electrical angle θ.
FIG. 5 is a flowchart showing the procedure for calculating the trigonometric function value sin θ corresponding to the above, and FIG. 5 is a diagram expressing this processing as functional blocks of the magnetic pole position calculation unit 4 and the trigonometric function generation unit 5. The current electrical angle θ is calculated as follows.

That is, the counter 20 of the magnetic pole position calculator 4 counts the pulse signals PA and PB from the incremental encoder 3. When the rising or falling of the pulse signals φu, φv, φw output from the magnetic pole sensor 2 is detected, the value EPC calculated by the pulse signal is stored in the register 21 as the electrical angle θ. E
PC indicates the absolute value of the electrical angle θ from the reference angle according to the resolution of the encoder 3. At the same time, the count value of the counter 20 at that time is preset in the register 22. At this time, the counter 20 and the register 22 have the same value, so the EPC held in the register 21 is directly output as the electrical angle θ. At each subsequent sampling time point, the content Pn held in the counter 20 and the content Pn-1 held in the register 22
And the value corresponding to the amount of movement of the magnetic pole from the previous sampling to the current sampling is added by the adder 23.
The value added to PC is output as the current electrical angle θ (S1). This value is set in the register 21 as the next EPC value (S2). In addition, at the time of start-up when the edge of the output pulse of the magnetic pole sensor 2 is not detected, half of the reading value of the magnetic pole sensor 2 every 60 ° (30 °, 90 °, 150 °, 210 °, 270 °).
The motor 1 may be controlled so that the current EPC value is the current EPC value, and moved to the change point of the sensor output.

Next, the electrical angle θ calculated in this way
Then, the trigonometric function value sin θ is obtained by the following procedure. As shown in FIG. 6, the EPC corresponding to the electrical angle θ is
Since the resolution is determined by the resolution of the incremental encoder 3, the incremental encoder 3 is set to 1 in Table 1 described above.
With the th resolution (one electrical angle cycle = 25000)
In the case of a pulse), in order to obtain a trigonometric function value with a resolution equivalent to this, it is necessary to hold 25000 words of data in the sine waveform table. In this device, in order to improve this, the sine waveform table 3 holds only the trigonometric function values of 504 words, and during that period, the interpolation processing unit 32 executes interpolation processing to obtain the values. .

Therefore, first, since the sine waveform table 31 is referred to from the EPC value, the EPC value is normalized by the normalization coefficient NR held in the normalization table 33 (S
3). The normalization coefficient NR is

[0024]

NR = number of data in sine waveform table / maximum value of EPC = 504/25000

Is given by The normalization coefficient NR is the top 16
When divided into bits and lower 16 bits and expressed by NRH and NRL,

[0026]

(4) DAT, DLT = NRH, NRL × EPC

Upper data DAT (integer part) obtained by
Is the address of the sine waveform table 31, lower data DLT
(Decimal part) is given as interpolation data in the interpolation processing unit 32.

When the address DAT is given to the sine waveform table 31, the sine waveform table 31 shows that the address DAT and the address D adjacent thereto are provided as shown in FIG.
The sine wave values SINA and SINB corresponding to AT + 1 are read and given to the interpolation processing unit 32. Interpolation processing unit 3
In 2,

[0029]

## EQU00005 ## SIN = SINA + (SINB-SINA) .times.DLT

The trigonometric function value SIN (= si
nθ) is calculated (S4). As a result, the obtained trigonometric function value becomes a value obtained by linearly interpolating between SINA and SINB, as shown in FIG. 6, and thus a value that substantially corresponds to the actual electrical angle θ.

In the above embodiment, the case where the present invention is applied to the synchronous motor has been described, but it goes without saying that the present invention can also be applied to an induction motor of a similar vector control system.

[0032]

As described above, according to the present invention,
The trigonometric function value is read by referring to the trigonometric function table with the address corresponding to the upper digit of the electrical angle of the rotor detected by the electrical angle detection unit and the address adjacent thereto, and the trigonometric function value is interpolated by the interpolation processing unit. Correct by doing. Therefore, even if the trigonometric function value stored in the trigonometric function table is small, a fine trigonometric function value can be obtained by the interpolation processing. Since the two-phase feedback signal and the three-phase voltage command value are obtained using the obtained trigonometric function value, highly accurate vector control can be realized with a small memory capacity.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of a vector control device for a motor according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of an electrical angle detected by a magnetic pole sensor in the control device.

FIG. 3 is a diagram for explaining magnetic pole position detection in the present embodiment.

FIG. 4 is a flowchart showing a procedure for calculating a trigonometric function value sin θ in the example.

FIG. 5 is a diagram showing the same procedure as functional blocks of a magnetic pole position calculation unit and a trigonometric function generation unit.

FIG. 6 is a diagram showing an output of a trigonometric function value sin θ in the example.

[Explanation of symbols]

1 ... Motor, 2 ... Magnetic sensor, 3 ... Incremental encoder, 4 ... Magnetic position calculation unit, 5 ... Trigonometric function generation unit,
6a, 6b ... Subtractor, 7a, 7b ... Buffer, 8 ... 2-phase / 3-phase converter, 9 ... PWM inverter, 10a, 10b
... galvanometer, 11 ... AD converter, 12 ... 3 phase / 2 phase converter, 20 ... Counter, 21, 22 ... Register, 23 ... Adder, 31 ... Sine waveform table, 32 ... Interpolation processing section, 3
3 ... Normalization table.

Claims (1)

[Claims] 1. An electric angle detecting means for detecting an electric angle of a rotor of a motor, a trigonometric function generating means for outputting a corresponding trigonometric function value from the electric angle detected by the electric angle detecting means, and the motor. The current detecting means for detecting the supplied three-phase current value, and the three-phase current value detected by the current detecting means and the trigonometric function value output from the trigonometric function generating means are used for the two orthogonal axes of the rotor. 3-phase / 2-phase conversion means for calculating the corresponding 2-phase feedback current, and error detection means for detecting an error between the 2-phase feedback current calculated by the 3-phase / 2-phase conversion means and the 2-phase current command value. A two-phase / three-phase conversion means for calculating a three-phase voltage command value from the error output from the error detection means and the trigonometric function value output from the trigonometric function generation means, Output from conversion means In a vector control method of a three-phase motor that supplies a three-phase AC voltage to the motor based on a three-phase voltage command value, the trigonometric function generating means corresponds to a higher digit of an electrical angle detected by the electrical angle detecting means. The trigonometric function table that outputs the trigonometric function value of the address and the address adjacent thereto, and the value corresponding to the lower digit of the electrical angle detected by the electrical angle detection unit are read from the trigonometric function table as the interpolation coefficient. A vector control system for a motor, comprising: interpolation processing means for correcting a trigonometric function value by interpolation processing.