SU1427349A1 - Temperature regulator - Google Patents

Abstract

This invention relates to automatic control systems. The purpose of the invention is to increase the accuracy of the controller. The goal is achieved by the fact that, in the temperature controller, a pulse width modulation forming unit (PIM) is performed on an operational amplifier (OU) 5 with a positive positive feedback (POS) 8, a, negative feedback circuit (axis) contains a cut-off diode 9, a controlled voltage divider formed by the field-effect transistor 18, a controlled release signal from the output of the scaling amplifier 4, and a potentiometer 17, a low-frequency tunable RC filter 11 and an integrating tunable RC circuit 16. 2 silt but (

Description

ABOUT)

sg

The invention relates to automatic control systems and is intended to maintain temperatures within specified limits by heating the control object.

The purpose of the invention is to increase the controller's TB.

Figure 1 shows the scheme of the proposed temperature controller; FIG. 2 shows time diagrams of the controller; a - in transient control modes, b - at the output of a tunable low-frequency RC filter, and in - at the output of an operational amplifier of a pulse width modulation shaping unit.

The temperature controller contains a sensor 1, a temperature setpoint 2, a comparison unit 3, a scaling amplifier 4, a pulse width modulation shaping unit performed on the operational amplifier 5, an operating element 6 acting on the control object 7, and the operational amplifier contains resistive positive feedback 8, in the negative feedback of which is switched on through diode 9, a controlled voltage divider 10 and a low-frequency tunable RC filter 11, and between the inputs of the operational amplifier 5 Two counter parallel-connected razvyaz

Diodes 12, 13, non-inverting input of op-amp amplifier 5 is connected with scaling amplifier 4 by a second resistor 1A, inverting n with a common bus regulator through the first resistor 15 and with an integrating RC-circuit 16 connected to the output of a low-frequency RC filter; 11, a potentiometer 17 of the controlled voltage divider 10 connected to the medium output, the first arm of which is formed by the potentiometer 17 and the other by the field-effect transistor 18 with the pn-junction and the p-type channel, the gate of which is connected with the output of the scaling amplifier A.

The device works as follows.

The error signal between the sensor 1 and the setting device 2 from the output of the comparison unit is amplified by the amplifier 4 and is fed to the non-inverting input of the amplifier 5. The output signal from

ten

15

20

output of the amplifier 5 is fed to the input of the executive body 6 and acts on the object to be regulated 7. The pulse width modulation shaping unit is built on the principle of a generating zero-body on the operational amplifier 5 covered by resistive positive feedback 8 and an integrating RC circuit 16. Suppose that the potential at the output of the low-frequency tunable RC filter 11 is zero, then the pulses at the output of the null organ will exist as long as the input voltage is within the limits of the linear portion of the amplitude x Characteristics of the operational amplifier 5. Otherwise, the output of the operational amplifier 5 establishes a voltage corresponding to a positive or negative level of limitation .. The dependence of the duty ratio of the generated pulses and the applied

25 input voltage limits

The linear portion of the amplitude response of the op amp 5, which is the proportional band of the DF controller, has a pulse width modulation pattern. The pulse period at the output of the pulse-width modulation shaping unit is determined by the recharge time of the capacitance of the integrating tunable RC circuit 16. Recharging the capacitance of the integrating tunable RC circuit 16 occurs due to the flow of current through the circuits: resistor 8, decoupling diode 12 or 13, integrating tunable RC circuit 16, common control bus. To the output of the pulse-width modulation shaping unit, through a cut-off diode 9, a control is connected to a 1.1V voltage divider 10, consisting of a potentiometer 17 and a field-effect transistor 18 with a pn-junction and a p-type channel. Provided that when the control object is heated, the voltage at the output of amplifier 4 is in the limit of the positive limitation level of the operational amplifier 5 of the pulse-width modulation forming unit, the source-drain resistance of the field-effect transistor 18 is large and the potential of the positive polarity from the output of the amplifier 5 through the cut-off diode 9 and the potentiometer 17 of the first arm of the controlled voltage divider 10 will accumulate in

35

40

45

50

55

the low-frequency tunable RC-capacitor capacitor 11. Assuming that the time constant of the low-frequency RC filter 11 is longer than the constant integrating RC circuit 16, the linear portion of the amplitude xfipaK-characteristic of the amplifier 3 changes and automatically shifts in the transition mode of the system in the right direction and to the required value, depending on the value of the constant time of the control object and the value of the external disturbance. The magnitude of the displacement is greater, the greater the constant of the time of the object of regulation and the greater the influence of disturbances that caused the transitional regime of the system.

This is illustrated by the time diagrams of Fig. 2a, where the external perturbation is considered as a step change in the setting of the control parameter A in the form of its specified values A1, A2, A3. When the setting changes from A1 to A2, the value of P1; the proportionality of the regulator

R

yH (, happens to meet the change

control parameter A (fig. 2a, period). At the same time, the potential of a positive polarity at the output of the low-frequency tunable RC filter 11 increases (Fig. 26, period ti-tj), and amplifier 5 is in the positive limit level (Fig. 2c, period t, -t). When the error signal is sufficient to switch the amplifier 5 to the linear control mode, in a block, the PWM generation starts generating negative polarity signals (Fig. 2c, periods tj-t ,,, tfe-t). At the same time, the potential of the positive field of the phasedness at the output of the tunable low-frequency RC-filter 11 decreases (Fig. 26, periods t, -C, ...) due to the discharge current of its capacitor through circuits connected to it (Fig. 2b, periods tg-t,

)

, and due to the vmenenie current for

a series of weakened controllable voltage telemetry 10, in which the resistance of the p-channel of the field-effect transistor 18 with the pn-junction decreases in proportion to the decrease in the positive level of the error at the output of the amplifier 4 (Fig. 26, periods t, -t ,, tj-tg).

The proportional band of the regulator jhr is shifted towards the specified

Jq. 20 25

27349 4

the value and with a zero level of mismatch tends to its minimum value (fig. 2a, periods

thirty

 , 35

40

50

55

C-tio

  AT 9

Thus, the duty cycle of the generated pulses is automatically changed and, as a result, the regulator structure automatically changes in a transient mode, i.e., a proactive seizure of the process occurs and the process is brought to a new specified value.

With a mismatch signal corresponding to a negative level of restriction (Fig. 2a, A3), the structure of the controller is unchanged and the capture and bringing the process to a new value occurs in the proportional band of & XP controller (Fig. 2a, tQ-C, / .

Thus, the 5th excludes self-oscillations of the control system when the object is heated in transient conditions by changing the dynamic response of the temperature controller in order to maintain the control parameter optimally and accurately.

Claims (1)

Invention Formula A temperature regulator containing a comparison unit, the inputs of which are connected to the sensor and temperature setting device, and the output to the input of the scaling amplifier, the output of which is connected to the input of the pulse-width modulation forming unit performed on the operational amplifier with feedback, and the output a pulse-modulation modulation unit is connected with the input of the executive body, characterized in that, in order to increase the accuracy of the controller, it contains a controlled voltage divider, made in the form of a sequence a coupled potentiometer and a field-effect transistor with a pn junction and a p-channel, the positive feedback circuit of the operational amplifier is formed by a resistor, and the negative feedback circuit is formed by a cut-off diode connected by the anode to the output of the operational amplifier, low-frequency tunable RC filter whose input is connected to the cathode of the cutting diode through a potentiometer controlled voltage divider, and an integrating tunable RC circuit connected by an input to the filter output, and an output to the inverting input of an operational amplifier, through the first resistor connected to the common bus of the regulator and through counter-on time  . " Ag jxp / X Diodes with a non-inverting input of an operational amplifier, which is connected via a second resistor to the output of a scaling amplifier connected via a third resistor to the gate of the field-effect transistor, the source of which is connected to the common bus of the regulator. i Figg