JPS59123486A - Digital controller for dc motor - Google Patents

Abstract

PURPOSE:To stabilize a DC motor at current intermittently interrupting time by correcting the gain of a current control system with the counterelectromotive voltage value of the motor and a firing angle command value at the current intermittently interrupting time. CONSTITUTION:A speed controller 21 outputs as a current reference signal IOD the function value of a proportional integration to the deviation input of a speed reference signal N0 and a speed feedback signal ND. A current controller 22 outputs as a firing angle command Valpha the function value of a proportional integration to the deviation between a current reference signal IOD and a current feedback signal ID. A gain correcting unit 23 inputs the output Valpha of the controller 22, a current feedback signal ID, and the output voltage detection signal V of a voltage detector 3, and outputs a correction value signal ValphaG. A converter 26 supplies as a firing angle command signal the output Valpha of the controller 22 at the current continuing time and the signal ValphaG at the current intermittently interrupting time to a gate pulse generator 27.

Description

[Detailed description of the invention] The present invention relates to a digital control device for a DC motor.

FIG. 1 shows a conventional example of this type of analog control device. In the figure, 1 is an AC power supply, 2 is a DC motor, 3 is a thyristor forward converter, 4 is a gate pulse generator, and are speed controllers, into which a deviation signal between speed command signal No. and speed feedback signal N is input. and outputs a proportional integral function signal for the deviation input. Speed feedback signal N
is the voltage output of the speed generator 6 connected to the DC motor 2.

Reference numeral I denotes a current controller, which receives a current reference signal Io output from the speed controller 5 and a deviation signal of a current feedback signal, and outputs a proportional integral function signal in response to the deviation input. The current feedback signal I' is a detection signal of a current detector 8 inserted into the AC input side of the forward converter 3. 9
is a voltage controller, and the voltage reference signal V is the output of the current controller 7.

and the voltage feedback signal (2), and outputs a first-order delayed signal with respect to the deviation input. Voltage feedback signal V is the output of voltage detector 10 that detects the DC motor 20 input voltage. The output of this voltage controller 9 is supplied to the gate pulse generator 4 as a firing angle command signal.

In this control device, one output of the Cyrisk power converter 3'
i8. When the current is continuous, a linear relationship is maintained between the firing angle command value given by the firing angle command signal output by the voltage controller 9 and the DC output voltage of the Cyrisk power converter 3, but when the output current is intermittent, When this happens, the DC output voltage will be affected by the back electromotive force of the DC motor 2, and will be lower than the expected voltage value for the firing angle command value, if the DC motor 2 is rotating in the forward direction. becomes higher, and lower when rotating in the opposite direction＼
As a result, the linearity between the firing angle command value and the DC output voltage is lost, and the gain of the voltage control system (minor roof) decreases in accordance with the degree of discontinuity of the output current.

By setting the cut-off frequency of this voltage control system to a value sufficiently higher than the cant-off frequency of the speed control system (main loop) and current control system (minor loop), the influence of the above-mentioned current intermittent on the control system can be alleviated to some extent. However, since there is an upper limit to this, there is a problem in that if the current intermittent is significant, responsiveness must be sacrificed for the sake of stability of the control system.

The above is a case of analog control, but even if you try to perform the control with digital control using a microprocessor, etc., the calculation time is finite, so if a high frequency response is required, a high-speed loop is required. There was a problem that this could not be expressed centrally because the calculation took time.

This invention was made in view of the above-mentioned conventional problems, and when the current is interrupted, the gain of the current control system is
By correcting using the motor's back electromotive force value and firing angle command value, and giving the corrected firing angle command value as a signal to the gate pulse generator, the entire system becomes sufficiently stable during current interruptions. The object of the present invention is to provide a digital control device for a DC motor that provides high control accuracy.

An embodiment of the present invention will be explained below with reference to the drawings.

In Fig. 2, B is a digital control device using a microprocessor, and its control system includes a speed control system (main loop) and a current control system (minor loop) that perform time-division calculation processing. It is a bank control system. 21 is a speed control section, 22 is a current control section, and 23 is a gain correction section.

The speed control unit 21 outputs a proportional integral function value as a current reference signal IOD with respect to a deviation input between the speed reference signal No. and the speed feedback signal N. The speed feedback signal ND is provided by a pulse encoder 24 connected to the DC motor 2.
This is the output of The current control section 22 receives the current reference signal IOC and the current feedback signal in, and outputs a proportional integral function value for the deviation between the two as the firing angle command signal ■α. The current feedback signal io is a signal obtained by digitally converting the detection signal of the current detector 8 by the 0 converter 25. The gain correction section 23 receives the output ■ of the current control section 22, the current feedback signal a, and the output voltage detection signal V of the voltage detector 3, and outputs a correction value signal ■αG. Current controller 2
The output ■α of 2 and the correction value signal VαG are supplied to the gate pulse generator 527 as a firing angle command signal via the switching section 26.

Next, the operation of this device will be explained.

The output average voltage Ed when the output current of the forward converter 3 is a continuous current is the maximum voltage value of the AC input of the forward converter 3, E
When m is the firing angle and α is the firing angle, it is expressed by the following equation.

Ed := −Em Co3α−−−=song=−−−=
(1)π When the output current of the forward converter 3 starts to be intermittent, this average voltage Ed changes as shown in the following equation due to the back electromotive force EC of the DC motor 2.

θ1=flow angle ・----1)
) The minute change in equation (1) above is: ΔEd= −−Emainα・Δα・・min・・・・・・
(3) Also, the minute change in the above equation (2) is as follows. However, K is a constant determined by the load characteristics, 1≦≦
2, 1 for resistive load, 2 for inductive load
becomes.

The gain of the control system when the current is intermittent is reduced by a value G expressed by the following formula compared to when the current is continuous.

sin α Here, the firing angle α is obtained from the firing angle command value ■α, and the back electromotive force Ec is the zero current J when the current is interrupted.

The output voltage detection value V at zero can also be determined. Further, the flow angle θ1 is determined as follows.

That is, FIG. 3 shows the output voltage waveform 32 when the forward converter 3 is controlled at the firing angle α during current intermittent, and α1 in this figure
Since the instantaneous value of the output voltage during one continuous current is expressed by the following formula, Ed=Emsin (α+-)・・・・・・・・・・・・
...(6) It is obtained by replacing Ed in the formula with the back electromotive force Ec. Approximate the flow angle θ, using the monthly salary of this town, as follows.

θ,=K(α−α1)・・・・・・−・・−・・・・・・
...(7) Firing angle α and back electromotive force E obtained in this way
By calculating the reciprocal of the above formula 5 using the reverse flow angle θ1, the gain correction value at the time of intermittent current can be obtained. Gain correction section 2
3 outputs the firing angle command value ■α when the current is continuous with gain correction, and the output VαG is supplied to the gate pulse generator 2T as the firing angle command value when the current is interrupted.

Since the above equation (5) is a simple arithmetic expression consisting of only a sine function, the functions can be easily tabulated and can be calculated in a short time by a microcomputer.

As described above, according to the present invention, the instability of the system when current #71 continues can be compensated for by a simple calculation using the firing angle and the value of the back electromotive force of the motor (I. As a result, it is possible to use a device with high stability and control accuracy.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a conventional analog control device for a DC motor, Fig. 2 is a block diagram of an embodiment of a digital control device for a 1m DC motor according to the present invention, and Fig. 3 is a block diagram of an embodiment of a digital control device for a thyristor power converter. Output when current is intermittent? jr, pressure waveform pressure waveform stone. In the figure, 2... DC motor, 3... Thyristor power converter, 21... Speed control section, 22... Current control section, 2
3... Gain correction section, 24... Encoder, 25...
...A/D converter, 26...switcher, 27...
Gate pulse generator. In addition, in the figures, the same reference numerals indicate the same or equivalent parts O. Agent: Nobu Kuzuno - Procedural amendment ￥ (voluntary) Commissioner of the Japan Patent Office 1, Indication of the case, Patent Application No. 57-229761 2
・Name of the invention Naofu'Ij7. Doimatsu's digital 1li1. l Tsukuda [Device F! 3 Relationship with the case of the person making the amendment Patent applicant address 2-chome LJ Marunouchi, Chiyoda-ku, Tokyo
Total: 3 G-Name (601) Mitsubishi Electric Corporation Representative Hitoshi Katayama 4, Agent Address 2-3 Marunouchi 2-1, Chiyoguchi, Tokyo
No. 5, Column 6, Detailed Description of the Invention of the Specification Subject to Amendment, Contents of the Amendment (1) "Proportional Integral Function Signal" in Page 2, Lines 10 to 11 of the Description is changed to "Proportional Integral Function Signal""Signal" is corrected. (2) Change “output of voltage detector 3” on page 5, line 14 to “
The output of the voltage detector 10 is corrected. (3) "Zero current IpJ is 'current Il)" on page 7, line 5.
I am corrected.

Claims (1)

[Claims] In a control device for a DC motor that is fed through a thyristor power converter and subjected to feedback control, ignition occurs when the output of the power converter is interrupted in response to a current feedback signal, an output voltage detection signal of the thyristor power converter, and an output of a current control section. A gain correction section is provided that performs a correction calculation of the current control system gain based on the angle command value and the DC motor back electromotive voltage value, and the output of the current control section is adjusted when the output of the power converter is continuous, and when the output is intermittent, A digital control device for a DC motor, characterized in that the output of the gain correction section is supplied to a gate pulse generator of the power converter as a firing angle command signal.