JPS6331493A - Controller for synchronous motor - Google Patents

Abstract

PURPOSE:To reduce torque ripples in an extremely low speed range, by generating the correction value of the torque ripple according to the rotational position of magnetic flux. CONSTITUTION:The torque ripple of a synchronous motor is previously metered, and correction current Ic for cancelling the torque ripple is found, and a value corresponding to the found correction current is stored in a memory element 22. On driving the motor, according to the change of position data thetar, a correction current value ic is called by the memory element 22. The called correction current ic is converted to an analog quantity by a D/A converter 23, and is added to the torque current Ia of output generated from a speed controller 20 by an adder 24.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a control device for a synchronous motor, and more specifically, a control device for a synchronous motor that greatly improves the smoothness of rotation when the motor rotates at low speed. Regarding equipment.

[Conventional technology]

Conventionally, synchronous motors (hereinafter referred to as SM) have been widely used as constant speed motors powered by a constant frequency power source, taking advantage of their robustness and low performance characteristics. In addition, with recent improvements in electronic device, microcomputer, and software technology, it has become possible to obtain a power source with a wide range of variable frequencies (hereinafter referred to as a driver) as a power source for driving the SM, and advances in magnets. With the emergence of brushless powerful SM, the above SM
is changing from brushed constant speed motors to brushless servo motors. Such a driver operates by vector control as shown in, for example, documents (1) and (2) in the "Reference List" shown at the end of the book.

The equation for the torque of the SM used in the above vector control is shown by the following equation (2). (For example, formula 6.3 of P2S5 in document (1)).

T=Ka・Ia・・・・・・・・・・・・■2Here,
Ka is a constant determined from the magnetic flux interlinking with each armature winding, the number of pole pairs, etc., and Ia is a torque current supplied to the primary winding.

As is clear from the above equation 0, the torque T is the torque current 1a
This shows that the torque T can be freely controlled by controlling this torque current Ta. Therefore, the above SM is suitable for use with servo motors that require high-speed response. It is suitable as

However, P 184 of document (2). As explained in FIG. 17 and related matters, the current distortion that occurs six times in one period of electrical angle causes torque ripple with a frequency six times the rotational frequency of the SM.

This current distortion is caused by the torque current 1a in the control system that controls the SM.
Even if the signal is an ideal signal, distortion occurs in the current that actually flows through the SM during the process from the signal to the power converter to 3MJ, and this is the biggest cause of this phenomenon. This is due to operational constraints (prevention of crossfire) of the power converter, as will be described later.

In addition, the torque ripple as described above impairs the "smoothness of rotation", which is another important performance of servo motors, so it is important for high-precision SM applications, such as finishing in the table drive of machine tools. Improvements in cutting, etc. are required as much as possible.

Here, as an example of a conventional vector control device for SM, FIG. 6-17 shown in P2O3 of document (1) will be described with reference to FIG. 6 of this specification.

As shown in FIG. 6, the power converter 8 is on the primary side of the SMI.
Three-phase currents iu, iv, and iw are supplied from. These three phase currents iu, i, v, iw are detected by current detectors 5, 6 .
7, and the results are sent to error amplifiers 14,
15.16 is fed back to each second input.

As described above, the three-phase currents iu, iv, iw are SMI
, the rotor of this SMI rotates with that frequency (-next layer wave number). The magnetic flux position of the rotor during this rotation is fed back by the magnetic flux position detector 2 to the u, v, and w phase current command calculators 17, 18, and 19.

Further, the speed ωr of the rotor is detected by a speed detector 3, the rotational position θr of the rotor is detected by a position detector 4, and a speed controller 20 and a position controller 2, respectively.
1 feedback will be given.

Furthermore, according to the configuration of a known servo device, the position command θr
When is given, in the position controller 21, a value proportional to the error (θr-θr) becomes the speed command ωr.

When this speed command ωr is given to the speed controller 20 as a speed command, the speed command ωr is added and ωr is subtracted, and a value proportional to the error (ωr−ωr) becomes the command acceleration. This commanded acceleration is proportional to the torque, and the torque is proportional to the torque current (2) a due to (2) above. Therefore, the error (ωr
-ωr) becomes the command current Ia.

For this command current Ia, current command calculators 17°*, iv, iw for each phase are created, and error amplifiers 14, 1515.
In 16, command currents iu, iv, and iw have errors (iu-iu) and (iv-iv) due to iw.

*(iw-iw) is generated and applied to comparators 10, 11, and 12. In these comparators 10 to 12, the signal is compared with a triangular wave which is a carrier wave from a known triangular wave generator 13, and a known sine wave pulse width modulation is performed. The sinusoidal pulse width modulated outputs from these comparators 10 to 12 are sent to the power transistors 8z of the power converter 8.
.

[Problem to be solved]

However, in the conventional vector control device for SM shown in FIG. 6, the currents iu, iv,
Even if iw has a distortion-free waveform, as shown in FIG. 17 on page 184 of document (2) and its related explanation, the operation of the base signal amplifier 9 and the power converter 8 causes the barwa transistor 8. Due to the on-delay clock time provided to prevent the crossfire of ~86, dead zones occur at all zero-crossing points of the currents of each phase.

This dead zone occurs twice per electrical angle period, and 3
In phase coalescence, it occurs six times per electrical angle-period. This dead zone causes a current ripple with a frequency six times the rotational frequency, and therefore a torque ripple based on the above-mentioned item (2).

This torque ripple causes a rift in the rotor speed, which is shown in FIG. 18 of document (2) with a distorted waveform of the current.

An object of the present invention is to achieve a significant reduction in the torque spectrum corresponding to harmonics of the -th layer wave number f by means of a device on the control device side.

[Means for solving problems]

In order to solve the above-mentioned problems, the present invention applies a multiphase primary current to the primary winding of the stator of a synchronous motor, generates a rotating magnetic flux within the stator, and generates a rotating magnetic flux in the stator. In a control device for a synchronous motor that generates torque in the rotor through electromagnetic interaction between the magnetic flux of the rotating rotor and the magnetic flux, a measured value of torque ripple that occurs periodically in response to the rotational position of the magnetic flux. A correction value corresponding to the above is stored, and a correction current is generated according to this correction value read out according to the rotational position of the magnetic flux, and the correction current corrects the above primary current to reduce the above torque ripple. It was designed so that

In a further improved form, a correction current is generated for each of the multiphase currents that constitute the primary current, and one of the multiphase currents is positioned at a rotational position where one phase generates current distortion based on the dead zone of the power converter. In this case, a correction current is applied to another phase which has the same rotational position but does not have the dead zone and therefore does not generate current distortion.

Further, the period of the correction current with respect to the rotational position of the magnetic flux is 60 degrees in electrical angle, an integral multiple of 60 degrees in electrical angle, or an integral fraction of 60 degrees in electrical angle, and the rotational position to which the correction current is applied is This is the position where current distortion occurs.

Furthermore, the storage means for the measured value of the torque ripple uses the rotational position of the magnetic flux as an address input, and outputs a correction value corresponding to the measured value.

Furthermore, advance compensation is applied to the correction current to reduce the influence of a delay in the electrical time constant of the synchronous motor.

[Effect]

When the difference between and the detected values iu, iv, iw is small (actually configured in this way), the torque T faithfully follows the torque current Ia according to the above equation 0, so this torque current ■
This is intended to improve the ripple of torque T by correcting a.

In particular, when the dead zone near the zero-crossing point of the current of each phase is avoided, the detected value iu with respect to the command value iu,
Since the detected value iv for the command value iv- and the detected value iw for the command value *iw are very faithful, iu
As shown in FIG. 3, the correction values for the two phases are such that the command values of adjacent phases are corrected while mutually avoiding the dead zone.

Further, correction values for iv and iw are also performed in the same manner as above.

[Embodiments] Hereinafter, a synchronous motor control device of the present invention will be described based on illustrated embodiments.

FIG. 1 is a block diagram of a synchronous motor control device showing a first embodiment of the present invention. Incidentally, the members that have already been explained in FIG. 6 will be given the same reference numerals to avoid redundant explanation.

In this first embodiment, the torque current of the synchronous motor is 1
This is a case where a is comprehensively corrected.

As shown in the figure, the output end of the position detector 4 is connected to the input end of the position controller 21 and also to the input end of the memory element 22. The output end of this memory element 22 is a digital/analog converter (hereinafter referred to as a D/A converter).
23, and this D/A converter 23
The output terminal of is connected to the first input terminal of the adder 24.

The output end of the speed controller 20 is connected to the second input end of the adder 24, and the output end of this adder 24 is connected to u, v.
, and the respective input terminals of the w-phase current command calculators 17, 18, and 19.

As mentioned above, the torque ripple of SM is 1/6 of the electrical angle.
It also occurs at an angle of 60°. This torque ripple is measured in advance every 3M, a correction current Ic that cancels out this torque ripple is determined, and a value corresponding to the determined correction current is stored in the memory element 22 using the position data θr as an address.

In such a configuration, when the SM is rotated, the conventional SM
Similarly, the detection data from the magnetic flux position detector 2 and the speed detector 3 are sent to the u, v, and w phase current command calculators 17, 18, respectively.
19 and speed controller 20, respectively. Furthermore, detection data from the position detector 4 is sent to the position controller 21 and is also input to the memory element 22 as position data θr.

Then, according to the change in the position data θr, the memory element 2
2, the position data θr is input as an address. Then, when the rotor comes to the position where the torque current 1a is to be corrected, that is, when any of the three phase currents is near the zero cross point, the correction current value ic is called from the memory element 22, and this called correction current The value ic is converted into an analog quantity by the D/A converter 23, and added to the torque current 1a output from the speed controller 20 in the adder 24.

At this time, the torque T is expressed by the following equation (2).

T±Ka-Ia 10 Ka·Ic...■ Here, Ka is the same as in the case of No. 2 above.

In this way, a current of magnitude (I a + I c) is applied to the u, v, wN current command converters 17, 18, and 19.

LJ (Thus, the torque ripple generated by Ka-1a is significantly improved by Ka.Ic.

Next, a second embodiment of the present invention will be described based on FIG.

This second embodiment is an example of a case where correction is made to avoid unfavorable zones in each phase.

As shown in FIG. 2, the output end of the position detector 4 is connected to the position controller 21, and is also connected to each input end of each memory element 22A, 22B, 22C constituting the memory element 22. Each of these memory elements 22A, 22B,
The output terminal of 22C is connected to each D/A that constitutes the D/A converter 23.
connected to the input ends of the converters 23A, 23B, 23C,
Furthermore, each adder 24A, 24B that constitutes the adder 24,
24C.

A first output terminal of the speed controller 20 is connected to a second input terminal of the adder 24A, and a second output terminal is connected to the second input terminal of the adder 24A.
The third output terminal is connected to the second input terminal of the adder 24C. The output end of the adder WS24A is connected to the input end of the U-phase current command calculator 17, the output end of the adder 24B is connected to the input end of the V-phase current command calculator 18, and the output end of the adder 24C is connected to the input end of the adder WS24A. is connected to the input terminal of the W-phase current command calculator 19.

The memory elements 22A, 22B, and 22C are memory elements similar to the memory element 22 shown in the first embodiment, and the current value ivc to be corrected according to the torque ripple measured in advance for each 3M. .

iuc and iwc are stored respectively.

For example, as shown in Figure 3, iu (
(see Fig. 3(a)) for a correction current of 1 uc (see Fig. 3(a))
When the command value iv (see FIG. 3(c)) is applied to the command value iv (see FIG. 3(c)), a waveform as shown in FIG. 3(d) is obtained.

Therefore, the correction current iuc is added to the command value iv, and the corrected current value iv is applied to the SM as shown in FIG. 3(e).

By the way, a certain amount of time delay occurs after the primary current of the SM is input until the secondary magnetic flux becomes electrically malicious. This time delay is called the "electrical time constant."

If a step-like signal indicated by the symbol P as shown in Fig. 4 is given as the primary current, there will actually be a "delay" as indicated by the symbol Q due to the above-mentioned electrical time constant, and this signal will be delayed. will stand up. In such a case, the above-mentioned "delay" can be canceled by adding a signal as shown by the symbol R. This above code R
Compensation for the electrical time constant as shown in is called "advanced compensation."

For the correction current supplied from the correction current generation section (for example, the part consisting of the memory element 22 and the D/A converter 23) shown in FIGS. 1 and 2 above, the correction current shown in FIG. By adding a "lead compensation circuit" consisting of well-known resistors R1, R3, R4 and an operational amplifier A as shown, "
If "lead compensation" is applied, it becomes possible to reduce the "delay" of the electrical time constant in the SM.

〔effect〕

According to the present invention, it is possible to reduce torque ripple in an extremely low speed range, so it is possible to maintain smooth rotation of the synchronous motor even in a low speed range.

[Brief explanation of the drawing]

Figure 1 shows the control of the synchronous motor of the present invention. II! FIG. 2 is an electric circuit diagram showing a second embodiment of the synchronous motor control device of the present invention, and FIGS. 3(a) to (e) are the same as those described above. Fig. 2 is a diagram showing correction of the phase current of the control device, Fig. 4 is a diagram showing correction of the electrical time constant, Fig. 5 is an electric circuit diagram showing a lead correction circuit, and Fig. 6 is a diagram showing a conventional synchronizer. Electrical circuit diagram of vector control device for eggplant motor, Figure 7 (a), (b), (C
) is a characteristic diagram of torque rise pull in a synchronous motor. ■・・・・・・・・・Synchronous motor, 2・・・・
...Magnetic flux position detector, 3... Speed detector, 4... Position detector, 8... Power conversion Part, 20...speed controller, 21...position controller, 22, 22A, 22B, 22C...
Memory element, 23.23A, 23B, 23C...D/A converter, 24.24A, 24B, 24C...Adder.

Claims (1)

[Claims] 1.) A multiphase primary current is applied to the primary winding of the stator of a synchronous motor to generate rotating magnetic flux within the stator, and a rotor that rotates concentrically with this magnetic flux. In a control device for a synchronous motor that generates torque in the rotor through the electromagnetic action of the magnetic flux and the magnetic flux, the control device corresponds to the measured value of torque ripple that occurs periodically in response to the rotational position of the magnetic flux. A correction value is stored in memory, and a correction current is generated according to the correction value read out according to the rotational position of the magnetic flux, and the correction current corrects the primary current to reduce the torque ripple. A synchronous motor control device characterized by: 2.) A correction current is generated for each of the multiphase currents that make up the above primary current, and at rotational positions where one of the multiphase currents generates current distortion based on the dead zone of the power converter, the rotational position is the same. 2. A control device for a synchronous motor according to claim 1, wherein a correction current is applied to the other phase which does not have the dead zone and therefore does not generate current distortion. 3.) The period of the correction current with respect to the rotational position of the magnetic flux is 60 degrees in electrical angle, an integral multiple of 60 degrees in electrical angle, or an integer fraction of 60 degrees in electrical angle, and the period at which the correction current is applied is 3. The synchronous motor control device according to claim 1, wherein is a position where current distortion occurs. 4.) The storage means for the measured value of the torque ripple is a storage means that uses the rotational position of the magnetic flux as an address input and outputs a correction value corresponding to the measured value. A control device for a synchronous motor according to scopes 1, 2, and 3. 5.) A control device for a synchronous motor according to claim 1, wherein lead compensation is applied to the correction current to reduce the influence of a delay in the electrical time constant of the synchronous motor. .