SU1566320A2 - Apparatus for program control of temperature - Google Patents

Abstract

This invention relates to process automation. The purpose of the invention is to increase the reliability of the device working out the heating program and stabilize the temperature of the electric furnace by restoring the task when the electrical power is turned off and then on. The buffer register, the second adder and the key block are entered into the device according to A.N. N1372278. Using the setting knob 11 of the heating rate, the required heating rate is set. In each control cycle, the current temperature is compared with the desired one and the electric furnace is turned on for a time proportional to the magnitude of the error. When the heating rate is turned off from the setpoint, the proportionality coefficient automatically increases. When the preset level of temperature stabilization is reached, the proportionality coefficient does not change. When the device is initially turned on or the power is turned off and then turned on during program heating, the counter 8 is reset, and the digital code corresponding to the current temperature of the electric furnace is fixed in the buffer register 4. The contents of the buffer register enter the adder 7, where the temperature setpoint is generated. Thus, the current temperature value is automatically set as the setpoint, and further the setpoint is incremented at a predetermined speed by adding the value corresponding to the contents of the counter. The setpoint code through the key block 12 enters the comparison block 6. When the temperature of the object reaches the set stabilization level or when the electric power is switched off and then switched on during the temperature stabilization, the key block is switched by a signal from the trigger 15, and in the comparison block 6, the set temperature setpoint from the setpoint 13 of the limit parameter is supplied as a setpoint.

Description

one

(61) 1372273

(21) 4348688 / 24-24

(22) 11/03/87

(46) 05.23.90. Bul No. 19

(71) State All-Union Central Scientific Research Institute of Complex Automation

(72) M. B. Shmuelzon, P. Yu. Gusev and A. V. Chervkov

(53) 621.503.55 (088.8)

(56) USSR Copyright Certificate f 1372278, cl. G, 05 V 19/18, 1988.

(54) DEVICE FOR PROGRAM TEMPERATURE REGULATION

(57) The invention relates to the automation of technological processes. The purpose of the invention is to increase the reliability of the device working out the heating program and stabilize the temperature of the electric furnace by

restoring the task when the power is turned off and then turned on. In the device on and.with. n 1372278 entered buffer register, the second adder and key block. Using the setting knob 11 of the heating rate, the required heating rate is set. In each control cycle, the current temperature is compared with the set temperature and the electric furnace is turned on for a time proportional to the magnitude of the error. When the heating rate is turned off from the set one, the proportionality coefficient automatically increases. When the preset level of temperature stabilization is reached, the proportionality coefficient does not change. When the device is initially turned on or disconnected and then switched on during the program

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ate

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the heating occurs, the counter 8 is terminated; a digital code is recorded in the buffer register 4 corresponding to the current temperature of the electric furnace. The contents of the buffer register enter the adder 7, where the temperature setpoint is generated. Thus, the current temperature value is automatically set as the setpoint, and further the setpoint is incremented at a predetermined speed by adding a value corresponding to the invention. The invention relates to the automation of technological processes and can be used, for example, to programmatically control the temperature of electrical resistance furnaces, when organ, a relay element is used, and is an improvement of the invention according to the author. St. No. 1372278.

The aim of the invention is to improve the reliability of the device by restoring the task during a power outage and subsequent power up.

The drawing shows a block diagram of the proposed device.

The device for software temperature control contains temperature sensor 1, object 2 is controlled (electric furnace), analog-digital converter 3, buffer register 4, clock generator 5, comparison unit 6, second adder 7, counter 8 second element 9, generator 10 pulses, heat rate setting unit 11, key block 12, limit parameter set 13, first digital comparator 14, trigger 15, comparison element 16, actuator 17, multiplication unit 18, timer 19, subtract 20 block, element 21 delays, second digital comparato 22, the first AND gate 23, the block 24 increments specifying the proportionality coefficient, the first adder 25, the dial 26 the proportionality coefficient.

The device works as follows.

press the counter. The setpoint code through the key block 12 enters the comparison block 6. When the temperature of the object reaches a given level of stabilization or shutdown and subsequent switching on of electric energy during temperature stabilization, the key block is switched

the signal from the trigger 15, and in block 6 of the comparison, the setpoint code of the stabilization temperature from the setpoint 13 of the limiting parameter is supplied as a setpoint. 1 il.

,

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The signal from sensor 1, the characteristic temperature of the control object 2 (electric furnace), is converted using an analog-digital converter 3 to a digital code. When the device is turned on, the digital code from the output of the analog-to-digital converter 3 according to the Start signal is rewritten into the buffer register 4 and is used to generate a predetermined temperature value. With a given discreteness by the signal from the clock generator 5, in block 6 of comparison, the deviation of the current temperature value Tj from the specified value T &

Ј. T - T ;.

The code value T is generated in two ways depending on the mode of operation of the device.

In the first method (during heating of the electric furnace), the digital code corresponding to Tj. Is formed by the second adder 7 by adding the contents of the buffer register 4 and the counter 6. The counting input of the counter 8 passes the second element 9 of the counting pulses from the generator 10 pulses. The pulse frequency, which characterizes the rate of change, T ,, is set with the aid of the setting device 11 of the heating rate. The connection of the second adder 7, which forms the digital code T, to the comparison unit 6 is realized by the block 12 keys. According to the second method (at temperature stabilization), the digital code corresponding to T takes the value of the stabilization temperature Tc, set by the setpoint 13 of the limiting parameter.

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The connection of the setting device 13 to the comparison unit 6 is carried out through the block 12 of the keys. In the event of a power outage and subsequent power up in the heating mode of the electric furnace, the counter 8 is reset, and in the buffer register 4 Fixes a digital code corresponding to the current temperature of the electric furnace, which, when added to the contents of the counter 8, forms the code value at the output of the second adder 7 T. Thus, immediately after switching on the device T, it takes on the value of the current temperature of the heater T (. and the heating process starts from the value T T (and not from zero. the counter 8 continues until the current temperature of the heater reaches the stabilization level.The rate of change of the contents of counter 8 and, consequently, of the second accumulator 7. forming a digital code of a given temperature, is determined by the pulse frequency of the generator 10. The contents of the buffer register 4 remain no change and equal to the value of the current temperature of the electric furnace at the time of power-up. The contents of the buffer register 4 change every time after turning off and then the device is turned on and remains unchanged with its uninterrupted operation. Ti is increased until the furnace temperature reaches the level of temperature stabilization Tc. The task Tc is set using the setting unit 13 of the limiting parameter.

The first digital comparator 14 compares the digital codes from the analog-digital converter 3 and the setting device 13. If the temperature of the control object is less than TC, then there is no signal at the output of the first digital comparator 14. The absence of this signal causes the presence of a signal at the output of the trigger 15. The trigger 15 is reset to its initial state when the device is turned on via bus Setting 0. The signal at the trigger 15 output opens the second element 9 for transmitting generator 10 pulses through it

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the input of the counter 8. The content of the second adder 7 through the block 12 enters the block 6 of the comparison. Thus, in block 6, a digital code is supplied that corresponds to a given temperature and is formed by the second adder 7 by adding the contents of buffer register 4 and counter 8. Counter 8 is reset to the initial state via bus Setting 0 when the device is turned on. When the object reaches a predetermined level of stabilization, a signal appears at the output of the first digital comparator 14. Trigger 15 reverses the state. Output change

20 of the trigger 15 causes the second element 9 to close to pass the counting pulses through it and switch the block 12. At the same time, the digital code arrives at the comparison block 6

25 of a predetermined temperature, corresponding to the limit value of the stabilization temperature Tc set by the setting unit 13. In the event of a shutdown and subsequent

JQ in the stabilization mode, the counter 8 is reset, the trigger 15 is set to the initial state and overwritten into the buffer register 4 the code value of the current heating temperature of 35 l.

If after turning on the power supply it turns out that the current temperature of the electric furnace T is higher or equal to 40

45

at a given stabilization temperature, the same actions will be repeated as when the specified stabilization level is reached, and the value of the desired stabilization temperature will be formed as a task. If a

after turning on the power T | Ј Tc, the steady-state signal at the output of the trigger 15 will open the second element AND 9 DPP passes to the counter 8

5Q counting pulses of the generator 10 and connect to the comparison unit 6 through the key block 12 the output of the second adder 7. Consequently, the block 6 receives a digital code corresponding to a given temperature and generated by the second adder 7 by adding the contents of the buffer register 4 and the counter 8. The rate of change the contents of the counter, and ultimately, and the second adder 7, which forms the digital code of a given temperature, is determined by the pulse frequency of the 1P generator. Thus, the device from the temperature stabilization mode enters the heating mode at a given speed, which continues from T ,, T, until the heater temperature reaches the specified stabilization level.

If it were not for the possibility of forming T, according to the measured (current) temperature of the heater, then with each disconnection and subsequent switching on of the power supply, the device would begin to work out the program of heating and stabilizing the temperature with zero (anew). In the comparison element 16, the condition under which the activation signal is issued through the actuator 17 of the electric furnace 2 is checked.

In multiplication unit 18, the control action time t is calculated in accordance with the expression

with "KP-Ј, where K p - is the coefficient proportional to

nosti.

The calculated time t .. is

AND

setting timer 19. Timer 19, after a predetermined time has expired, switches off electric furnace 2 through actuator 17. Thus, if in this control step the current temperature is less than the temperature set at that moment, then the electric furnace is turned on for a time proportional to the deviation value. If these temperatures are equal or if the current temperature is higher than the set temperature, the electric furnace is not turned on.

In order to increase the accuracy of temperature control in accordance with a given program (heating rate), the device will automatically change the proportionality coefficient Kp. For this, in subtraction unit 20, the actual heating rate V of the electric furnace is determined in accordance with the formula

VP T., -tm,

where t j. - temperature value

electric furnace of the previous with respect to the current control cycle.

The value of the code corresponding to

T; enters subtraction unit 20 from analog-digital converter 3, and the code value corresponding to

T,

is formed in element 21 pu1-1 by the arrival delay code from

analog-to-digital converter 3 to block 20 for one control cycle. The coding code corresponding to Vp is fed to the second digital compartor 22, where a comparison is made between the given heating rate U., the code of which comes from preset 11, and the actual speed Vp. When the condition Vj, Vp is fulfilled, a signal is output from the second digital comparator 22 to the first element 23.

At the output of the first element And 23, a signal is generated in the presence of a signal from the second digital comparator 22 and the trigger 15, i.e. if V, Vp and T with t. The unit 24 for specifying the increment of the coefficient of proportionality selects one of two values of the increment of the coefficient of proportionality of the EC:

Жп, at receipt of a signal from the first element I 23;

Oh, in the absence of a signal V from the first element And 23.

DKP

Q

with

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In the first adder 25, the digital code Kp is summed up, the initial value of which is set using the proportional coefficient setpoint 26 when tuning the device, with one of

two values: n or 3 of the first adder 25, the result of the sum enters multiplication unit 18, where the time of the control action is calculated. The change in K n during the program heating of an electric furnace can be described by the following expression

to".

Kni

TO,

, with Vp, Chu or T-Tc; + DCT

with Vp VjH

where k

PI

 ni-i

P 1-1

T, TC

- proportionality factor, according to which tw is calculated in the current control cycle; coefficient of proportionality of the previous to the current control cycle.

Thus, as the electric furnace warms up, K automatically increases, and its increment occurs during control cycles in which the heating rate is less than the specified one. When the stabilization level Kp is reached, it becomes such that its value is sufficient to maintain this temperature, the trigger 15 is activated, the signal does not arrive at the proportionality coefficient incrementing unit 24 and subsequently the Kp remains unchanged.

The initial value KB, as well as the value / 1КП, specified in block 24, are selected when setting up the device and depend on the dynamic characteristics of the furnace.

Claims (1)

The invention The device for software temperature control on the author, St. Q five 0 No. 1372278, characterized in that, in order to increase the reliability of the device, it contains a buffer register, a second adder and a key block, the information input of the buffer register connected to the output of the analog-digital converter, the output of the buffer register connected to the first input of the second adder, the second input which is connected to the output of the counter, and the output - to the first information input of the key block, the second information input of which is connected to the output of the limit parameter setting unit, and the control input is connected to the output of the trig EPA, outputs a key block connected to the second input of the comparing unit, the buffer register write input connected to the input device Start.