SU1614032A1 - Device for stabilizing revolutions of driving shaft of tape recorder tape transport mechanism - Google Patents

Abstract

The invention relates to instrumentation, in particular to the technique of magnetic recording. The purpose of the invention is to improve the accuracy of stabilizing the rotational speed of the drive shaft by increasing the transmission coefficient of the open-loop device while maintaining the stability margin. The device contains serially connected frequency discriminator, amplifier-converter, power amplifier and electric motor, the rotor of which is kinematically connected to the drive shaft and the rotational speed meter, while the amplifier-limiter, two nonlinear elements, the first and second attenuators and the comparator provide an increase in transmission coefficient maintaining sustainability. 3 il.

Description

The invention relates to instrumentation, in particular to magnetic recording, and can be used in systems for automatically controlling the rotation frequency of the drive shaft, and hence the speed of movement of the recording medium in tape recorders ..,

The purpose of the invention is to improve the accuracy of controlling the frequency of rotation of the shaft of the tape recorder mechanism.

FIG. 1 shows a functional diagram of the proposed device: in FIG. 2 - time diagrams of voltages, referring to the principle of operation of the device: in FIG. 3 - algorithmic (structural) scheme of the device, where Wi (P) Ki / (Tip + 1): W2 (P) K2 / T2p + 1):

W3 (P) K3 / (T3p + 1) x (T4p + 1)

W4 (P) K4 / (T3p + 1):

W5 (P) K5 - transfer functions, respectively, of frequency discriminator, amplifier-converter and power amplifier, electric motor for control and disturbing influences, meter of rotational speed:

К :, К2, Кз, К4 and КБ - transfer coefficients:

TI, T2. Tz and T4 are the time constants fo (P). f3 (p). wed) w (p). M (p) and V (p) —the images in the Laplace set the action, feedback signal, error, controlled variable, disturbance effects on the load moment and supply voltage, respectively.

The device consists of a power supply 1, a frequency discriminator 2. an amplifier converter 3. an amplifier 4 of power, an electric motor 5, the rotor of which is kinematically connected with a driving shaft 6 and a meter 7 of frequency of rotation, an amplifier limiting 8, a differentiating circuit 9. the first 10 and second 11 nonlinear elements, the first 12 and second 13 attenuators and the comparator 14.

The device can be implemented in hardware, for example, as follows: a DC power supply 1 (auto

E o

with

fO

k

Yomny or mains), frequency discriminator-Nator 2, amplifier-converter 3, amplifier-limiting device 8 and comparator 14 (mainly for operational amplifiers with differential inputs), power amplifier 4 (at transistors), 5 direct current motor with excitation magnets, meter 7 rotational speed (inductive or photoelectric type), Differentiating circuit 9 (resistive-capacitive), the first 10 and second 11 nonlinear topics (on diodes), the first 2 and second 13 | attenuators (on resistors). : The device works as follows.

In the steady state, the rotor of the electric motor 5 rotates at the nominal (required) frequency, since the nominal control voltage is applied to the input of the electric motor 5 from the output of the power amplifier 4. Kinematically: the drive shaft b associated with the rotor of the electric motor 5 and the rotational speed meter 7 are also rotated at nominal frequencies.

: When the load moment changes on a-; the shaft 6 and the voltage of the source 1: the power is changed from their nominal values, respectively, and the rotation frequency I of the drive shaft 6 and the speed meter 7, and hence the frequency w ith on his way out. The frequency discriminator 2 generates an error signal I, the value of which is proportional to the deviation of the rotation frequency of the drive shaft 6 from the nominal value. The generated error signal is corrected and amplified by the voltage of the amplifier-converter 3. And by power, by a power amplifier 4, it is applied to the input of the electric motor 5 in such a way as to compensate for the effect of disturbing influences with an accuracy of the established error.

In accordance with the algorithmic scheme (Fig. 3) of the Laplace image, the error 0 (p) of the regulation is:

/ uh W4 (p) Afe (p).

p) -t + Sh)

M (p)

GoodTr + SchrG

V (p)

where W (prWi (p); W2 (p); W3 (p): W5 (p) is the transfer function of the open-loop device stat5 or chzim.

With constant deviations of the moment M of the load and the voltage U of the power supply from formula (1), we obtain the expression

for the forced (steady-state) component of the regulation error:

/ 3

K / iKsM КзКб-У 1 + Кр 1 + Кр

(2)

where Kp Ki. К2, Кз, Кз- coefficient of transmission of an open device.

For the device for controlling the frequency of rotation of the drive shaft of the tape recorder mechanism (LPM), the inequality

Tz Ti T2 T4,

(3)

where is ti. T2, Tz, and T4 are the time constants of the frequency discriminator, the amplifier converter with the power amplifier, and the electric motor, respectively.

(electromechanical and electromagnetic).

As follows from the expression (2), the value

the established error is less than

more Cr. Exodus from the condition of sustainability

devices taking into account inequality (3), the limiting value of Kp cannot be accepted greater than l / Ti. The value of the time constant Ti is chosen based on considerations of permissible ripple of the error signal, taken from the output of the frequency discriminator 2.

Therefore, the higher the frequency of the output voltage of the rotational frequency meter 7, the shorter the time constant Ti and, as a result, the greater the Kp. The frequency of the output voltage (Hz) of the meter 7 of the induction or photoelectric type is determined by the relation

f e wZ,

where fu and Z are the rotation frequency (s) and the number of teeth (holes) of the rotor of the meter 7, respectively.

Increased accuracy is achieved by increasing the transmission coefficient.

open-loop device without decreasing the stability and absolute stability margins, since the output of the comparator 14 increases the pulse frequency at their constant duration and amplitude,

as a result, the time constant Ti can be reduced by 2 times and, therefore, the transfer coefficient Kp of an open-loop device can be increased by 2 times. A signal from the output of the rotational speed meter 7 is applied to the input of the amplifier-limiter 8 (Fig. 2a). This signal is amplified and limited in amplitude by the amplifier-limiter 8 (Fig. 26), differentiated by time in differentiating circuit 9

(Fig. 2c) and is fed to the inputs of the first 10 and second 11 non-linear elements.

Nonlinear elements 10 and 11 select differently differentiated differentiated pulses and serve, for example, positive pulses. non-inverting input of comparator 14, and negative pulses - to inverting its input (Fig. 2g and Fig. 2d |. The same inputs of the comparator 14 from the outputs of the first 12 and second 13 attenuators are supplied with bias voltage Uoi and Uo2, the value of which satisfies condition (Uoi-Uci2) 1. which eliminates the false triggering of the comparator 14 from interference at its inputs and sets the required polarity and duration of the pulses at its output (Fig. 2.e).

Thus, at the output of the comparator 14, a sequence of rectangular pulses of a given polarity and a constant duration and amplitude is formed over the entire range of input frequencies.

From the output of the comparator 14, a sequence of rectangular pulses of constant duration and amplitude is fed to the input of frequency discriminator 2, ensuring the operation of the device for stabilizing the frequency of rotation of the drive shaft of the tape drive mechanism in both steady state and transient operating modes.

Claims (1)

Invention Formula A device for stabilizing the rotational speed of the drive shaft of the tape recorder mechanism, comprising a power source and a frequency discriminator connected in series, an amplifier / converter, a power amplifier and an electric motor, the rotor of which is kinematically connected to the drive shaft and a rotation frequency meter, characterized in that increase the accuracy of stabilization of the rotation frequency of the drive shaft, an amplifier-limiter and a differentiating circuit, connected in series, the first and second nonlinear elements, the first and second attenuators, as well as the comparator, the first input of which is connected to the outputs of the first attenuator and the first nonlinear element, the second input to the outputs of the second attenuator and the second nonlinear element, and the inputs of the first and second attenuators are connected to the source output power, the inputs of the first and second nonlinear elements to the output of the differentiating circuit, the output of the comparator is connected to the input of the frequency discriminator, and the input of the amplifier-limiter is connected to the output of the rotational speed meter . 1 Figg mm v {p IP Blp). “.  } - MgChM  Il..J L, y; / s;