SU1721772A1 - Dc electric drive - Google Patents

Abstract

The invention relates to electrical engineering, in particular, to precision electric drives with an in-phase rotation of an electric motor, and can be applied in systems of automatic control by VCR drives. The aim of the invention is to improve the accuracy of rotational speed control by eliminating systematic errors. The electric drive contains an electric motor 8 with a pulse frequency sensor 1, connected to a power amplifier 7. a generator of 2 clock pulses, two pulse counters 3 and 5, a comparison unit 4, a decoder 6, a geometric error correction block 10, a speed correction block 11, and corresponding connections between them. In this device, the output of block 10 allocates a frequency that does not depend on the frequency deviation caused by the eccentricity of sensor 1. This allows the frequency of rotation of the electric motor to be adjusted with greater accuracy. 3 il. fe 41 43 h VI s Figure 1

Description

The invention relates to electrical engineering and can be used in digital high-frequency drives of video recorders.

A digital DC electric drive is known, which includes a pulse sensor, a frequency meter, a digital frequency controller, a pulse-width modulator, a converter and a low-order accumulator.

The device allows you to adjust (vary) the rotational speed of the motor, however, it has a sufficiently large ripple of rotational speed in the steady state.

The purpose of the invention is to improve the accuracy of speed control by eliminating systematic errors.

Figure 1 shows the structural electrical circuit of a direct current drive; 2 is a functional electrical circuit of a geometric error correction unit; FIG. 3 is a functional electrical circuit of a speed correction unit.

The DC motor (Fig. 1) contains a rotational frequency pulse sensor 1, a generator of 2 clock pulses connected in series, a first counter of 3 pulses, a comparison unit 4, a second counter of 5 pulses, a decoder 6, a power amplifier 7 and an electric motor 8. In addition, The electric drive contains a D-flip-flop 9, the synchronization input of which is connected to the second input of the geometric error correction unit 10, the output of which is connected to the first input of the speed correction unit 11, the output of which is connected to the second input of the comparison unit 4. The output of the clock pulse generator 2 is connected to the second input of the speed correction unit 11 and to the first input of the geometric error correction unit 10, the second input of which is connected to the first output of the rotational frequency pulse sensor 1, the second output of which is connected to the third input of the geometric error correction block 10 and with the information input of the D-trigger 9, the output of which is connected to the input of the installation of the second counter 5 pulses.

Pulse sensor 1 speed (Fig, 1) contains a modulation-raster disk 12 and the generators 13 and 14 counting pulses. The modulation raster disk 12 has one information track and is rigidly connected to the shaft of the electric motor 8, which is a non-contact DC torque motor.

Block 10 correction of the geometric error (figure 2) contains the imaging unit 15

pulses, the first, second and third triggers 16 - 18, the elements AND-NOT 19 and 20. the outputs of which are connected to the inputs of the element OR-NOT 21, the output of which is connected to

the synchronization input of the counter 22 pulses, the output of which is connected to the synchronization input of the trigger 18, the first and second outputs of which are connected respectively to the installation input of the counter 22

0 pulses and with the output of block 10 geometric error correction, the first input of which is connected to the synchronization input of the trigger 16 and the first input of the element AND-NOT 19, the second input of which is connected to

5 the first output of the trigger 17, the second output of which is connected to the first input of the element AND-NOT 20, the second input of which is connected to the output of the trigger 16. The second input of the geometric correction unit 10

0 error is connected to the input of the pulse driver 15, the output of which is connected to the installation input of the trigger 18 and to the installation input of the trigger 17, the synchronization input of which is the third input of the unit 10

5 geometric error correction.

The speed correction unit 11 (FIG. 3) contains a pulse distributor 23 connected in series, the first pulse counter 24, the second pulse counter 25

0 and an IS-HE element 26, the second input of which is connected to the output of the third pulse counter 27, the input of which is the second input of the speed correction unit 11 and connected to the synchronization input of the counter 24

5 pulses and with the synchronization input of the pulse distributor 23, the second output of which is connected to the control input of the second pulse counter 25, the synchronization input of which is connected to the output

0 of the NAND element 26. The installation of the distributor 23 of pulses is the first input of the speed correction unit 11, the outputs of which are a group of outputs of the counter of 25 pulses.

5 The drive operates as follows.

The modulation-raster disk 12 named after the pulser of the rotational speed sensor 1 is rigidly connected to the shaft of the electric motor 8.

0 Generators 13 and 14 of counting pulses are designed to convert the angular displacement of the modulation-raster disk 12 into a proportional number of pulses. Optocouplers of generators 13 and 14 counters

The 5 pulses are located around the circumference of the modular-raster disk 12 by 180 ° one relative to the other and are shifted by a quarter of the raster step, and the raster path of the modulation-raster disk 12 has (Z-1) circumferential marks.

The start of the electric motor 8 and its acceleration to the nominal speed is carried out with the help of a generator of 2 clock pulses and a block 4 of comparison. Upon reaching the nominal speed, the electric motor 8 begins to operate in a self-switching mode, provided by a counter of 5 pulses and a decoder b, which form the switching pulses of the windings of the contactless electric motor 8, shifted 120 ° apart from each other (for a three-phase motor), i.e. It is an electronic sensor for the position of the rotor of the electric motor 8.

- To synchronize the switching pulses of the electric motor 8 relative to the position of the modulation-raster disk 12, the D-trigger 9 generates a reference pulse (HO), which appears once per turn of the disk 12, since its raster track has a missing mark , and the outputs of the generators 13 and 14 of the counting pulses are connected respectively to the D- and C-inputs of the D-flip-flop 9. If there is no pulse at the D-input (label missing), the output of D-flip-flop 9 appears the duration of the period of the pulse generator 14 account impulses. The synchronization is carried out by applying signals from the output of the trigger 16 at a frequency of ft / 2.

After arrival at the third input of block 10 of the geometric error correction of the leading edge of the 1m2 frequency pulse, the trigger 17 will be set to the opposite state. At the same time, 22 pulses go to the synchronization input of the pulse counter (via the N-NE element 19 and the OR-NE21 element) from the first input of the geometric error correction block frequency fT. Pulse counter 22 counts the pulses arriving at its synchronization input before overflow. The pulse of the overflow pulse 22 translates the trigger 18 into the opposite state. The position of the back edge of the pulse from the inverse output of the trigger 18 does not depend on eccentricity, since with the aid of the pulse counter 22 it is determined that the center of the relative fronts of the frequency fMi and fM2 and its relative time shift is made by a constant value:

N K-TT,

where K fT / 2-fM is the counter conversion factor of 22 pulses;

T 1 / fT is the period of the clock frequency.

Thus, the geometric error correction unit 10 produces a computation fM;

the half sum of the frequencies fMt and fM2 and gives the frequency f, which does not depend on the change in the mutual arrangement of the leading edges of the pulses of the frequency fMi and fM2, i.e. devoid of deviation due to eccentricity of the disc.

However, eliminating the influence of the eccentricity of the modulation-raster disk 12 does not exclude fluctuations in the rotational speed of the electric motor 8 in the stabilization mode due to, for example, external disturbances, which leads to a decrease in the accuracy of controlling the rotational speed of the electric motor 8. To eliminate this, the device operates as follows.

Comparison unit 4 separates the phase mismatch between the frequency f0n from the output of the 3-pulse counter and the frequency foe from the output of the speed-correction block 1. The speed correction is performed by the speed correction block 11, which measures the increment of the subsequent period of the frequency fM over its previous period and extends the value of this increment by K times.

Frequency 1m is formed by the geometric error correction unit 10 and is equal to wz.

I

where (o is the speed of rotation of the electric motor 8;

Z is the number of marks on the modulation raster disk 12.

Speed corrections are made in the linear zone, i.e. in the steady state of stabilization of the speed (frequency) of rotation of the electric motor 8.

Upon arrival at the first input of the speed correction unit 11 (FIG. 3) of the falling edge of the frequency pulse fM from the output of the geometric error correction unit 10, the first clock pulse frequency fT records information from the counter 24 pulses into the counter 25 pulses. The clock frequency is selected three orders of magnitude higher than the frequency fM. The second pulse clock frequency fT is preset counter 24 pulses. If the frequency period fM does not change, i.e. There are no disturbing influences on the motor 8, the period Tm 1 / tm, and the frequency pulses fM are shifted by the speed correction unit 11 by a constant time interval r0, forming a new sequence of pulses with frequency f0c.

In this case, t0 K ,, -,

where Kp is the counter division ratio of 27 pulses;

To-tt-n;

TT-Pt, N - the maximum volume of the counter 24 pulses.

With this (1-1) -th frequency pulse fM in the counter 24 pulses, the number n - N / 2 (preset) is recorded.

For the arrival of the 1st pulse frequency fM, the counter 24 pulses can overflow a certain number of times, due to the difference in frequencies fr and TM and the volume of the counter itself. If the 1st pulse frequency fM comes through a time interval Tm -M -To p -Tt, M - the number of counter overflows 24 pulses per period Tm; The correction is not made, and the 1st pulse of the frequency fM is shifted by the time interval m. A pulse counter 25 operates in a pulse subtraction mode, fV / Kp, generated by a pulse counter 27. The counter is blocked by the counter 25 pulses of the TT / KP frequency by the signal of its overflow, which arrives at the first input of the AND-NE element 26.

Suppose that the period Tm of the frequency fM has decreased. Then (t + tyft impulse passes through the interval

 - M-To + W-TT,

it is obvious that u N / 2. The number of W is recorded in the pulse counter 25, and the number of pulses N / 2 is recorded in the pulse counter 24.

Shift (1 + 1 j-ro pulse when this occurs by

L Cr -t-TT

; Now let the period Tm of the frequency fM increase. Then (+2} th pulse will come through the interval

Tm +2 M -To + p2; TT,

moreover, P2 N / 2. The shift (1 + 2) pulse occurs in this case by

Г2 Кр Ti2 Тт.

Thus, with a change in the period Tm by the value of u Tt, the period of the new pulse sequence foe changes by Kp times, and decreases, if u u N / 2 and increases if u u

 N / 2. The duration of the phase mismatch varies by the same amount.

The speed correction is performed under the assumption: the period That must be less than the period of the reference frequency foe. The maximum value of T0 is selected from the condition of maximum overshoot. The speed correction unit 11 thus performs frequency conversion fM

and produces a new sequence of frequency pulses foe- The pulses from the output of the comparator unit 4 are counted by a pulse counter 5, which together with the decoder 6 generates pulses

switching windings of a contactless electric motor 8.

The use of the proposed electric drive allows high accuracy of rotational speed control.

motor, as well as to increase this accuracy by eliminating systematic errors in the regulation.

Claims (1)

Invention Formula A DC motor containing a motor with a pulse frequency sensor connected to a power amplifier connected in series with a clock generator pulses, a first pulse counter and a comparison unit, as well as a second pulse counter, characterized in that, in order to improve the accuracy of rotational speed control, a decoder, a D-flip-flop and a series-connected geometric error correction block and a velocity correction block are inputted into it connected to the second input of the comparator unit, the output of which is connected to the synchronization input of the second pulse counter, the outputs of which are connected to the inputs of the decoder, the outputs of which are connected to the inputs of the power amplifier, The output of the clock pulse is connected to the second input of the speed correction unit and to the first input of the geometric error correction unit, the second input of which is connected to the D-trigger synchronization input and to the first output of the rotational frequency impulse sensor, the second output of which is connected to the third input of the geometric error correction unit and with the information input of the D-flip-flop, the output of which is connected to the input of the installation of the second pulse counter. .J FIG. 2