KR100303065B1 - temperature process control system for heating system - Google Patents

Abstract

The present invention relates to a temperature process control apparatus for heat treatment equipment for controlling the temperature of various furnaces and heat treatment apparatuses used in ceramics, steelmaking, petrochemical, air-conditioning, cold and hot warehouses, farms, etc. It is impossible to solve the problem, and can not be applied to various heat treatment equipment. To this end, a temperature process control apparatus for a heat treatment apparatus according to the present invention includes a temperature sensor for detecting the temperature of the heat treatment apparatus as an electric quantity; A transducer for converting the output signal of the temperature sensor into an electrical signal that can be recognized by a digital circuit; A microcontroller that analyzes the output signal of the transducer and controls the temperature by a PID control method, uses auto-tuning to set the coefficient of the PID controller, and corrects the coefficient by a backward method when the set coefficient is out of an error range; A switching element for switching power input to the heat treatment device according to the control signal of the microcontroller; A computer having the same temperature process control method as the microcontroller, and displaying a temperature change on a screen and programmed to control the temperature by a graphical user interface (GUI) method; The microcontroller and the computer form a network, the remote controller comprising a communication module that enables the temperature control of the heat treatment device through the microcontroller, primarily in the computer Is controlled as I / O to perform temperature process control, and in case of computer failure, the control right has a fail-safe concept of transferring to a microcontroller. The microcontroller and the computer are automatically tuned using a maximum slope (R) of the temperature rise section and a delay time (L) of 1/2 of the time (L1) between overshooting and returning to the set point. It is characterized by setting the coefficient of the PID controller.

The temperature process control device for heat treatment equipment as described above is capable of precise temperature control by applying PID control method, automatic tuning technique, and backward technique, and it can be applied to temperature process control of various heat treatment apparatus by applying automatic tuning technique. have. In addition, the introduction of the GUI method, the operator can easily control the temperature, there is an advantage that the temperature process control at a long distance by using a communication module.

Description

Temperature process control system for heat treatment equipment {temperature process control system for heating system}

The present invention relates to a temperature process control device for controlling the temperature of a heat treatment system having a very high latent heat, such as various furnaces and heat treatment equipments used in ceramics, steelmaking, petrochemical, air-conditioning, cold and hot warehouses, and farms. The present invention relates to a temperature process control device for a heat treatment device capable of precise temperature process control and simple temperature process control by a GUI (Graphical User Interface) method.

Various furnaces and heat treatment apparatuses are used in various fields such as industrial, cooking, ceramics, hobby, etc., so that there is no place which is not used in industrial or real life. In particular, electric furnaces are used for industrial furnaces because temperature process control is simpler than other furnaces and impurities do not enter the material. It is also commonly used in the production of crafts such as drying ceramics on a small scale in a studio or home.

In the temperature process control of the furnace and the heat treatment apparatus, the high value-added heat treatment field and ceramics field require precise temperature process control and various steps of firing process. The temperature process control in this field is very important because the physical properties vary depending on the firing time and at what temperature.

Although precise temperature process control is required in the heat treatment field as described above, the conventional temperature process control apparatus for heat treatment equipment does not satisfy the above requirements. In addition, due to the rapid development of the electronic and information industries, all the control concepts are changing from the manual and sequence control that is conventionally performed to the concept of automatic control management. However, the conventional temperature process control apparatus for heat treatment equipment is a controller having an independent control concept using an 8-bit microprocessor without the concept of multi-control, communication control, screen control, interlock control, and the like. Therefore, since the controller performs only simple control operations and is programmed based on the machine language, it is difficult to apply various algorithms, and thus, there is a problem that precise temperature process control cannot be performed. Also, it does not display processing values in progress. Therefore, there is a problem that it is difficult to determine whether there is a failure and very difficult to find the cause when malfunctioning. In addition, since it is difficult to modify and supplement the program, it is inconvenient to modify the entire program to add a function of the controller. In addition, the coefficient of the controller must be set for each control object by applying an experimental technique or a trial and error method, and there is a problem in that the efficiency of the controller is lowered because only one system can be controlled by one controller.

Accordingly, the present invention has a first object to provide a temperature process control device for heat treatment equipment capable of precise temperature process control in order to solve the above problems.

It is a second object of the present invention to provide a temperature process control device for heat treatment equipment having a general purpose that can automatically set coefficients of a controller so as to be used for temperature process control of various heat treatment equipment.

And a third object of the present invention is to provide a temperature process control device for a heat treatment device capable of temperature process control through a screen at a distance.

1 is a block diagram of a temperature process control apparatus for a heat treatment apparatus according to the present invention.

2 is a system configuration of a temperature process control apparatus for a heat treatment apparatus according to the present invention.

3 is a diagram for explaining an automatic tuning technique.

4 is an overall flowchart of a temperature process control program according to the present invention;

5 is a control screen when the temperature process control program according to the present invention is executed;

<Description of the symbols for the main parts of the drawings>

1: electric furnace 3: temperature sensor

10 Temperature Controller 11 Microcontroller

13: triac 19: main computer

21: RS-232C communication module 23: RS-485 communication module

In order to achieve the above object, a temperature processing control apparatus for a heat treatment apparatus according to the present invention includes a temperature sensor for detecting the temperature of the heat treatment apparatus as an electric quantity; A transducer for converting the output signal of the temperature sensor into an electrical signal that can be recognized by a digital circuit; A microcontroller that analyzes the output signal of the transducer to control the temperature by a PID control method, uses auto-tuning to set the coefficient of the PID controller, and corrects the coefficient by a backward method when the set coefficient is out of an error range; A switching element for switching power input to the heat treatment device according to the control signal of the microcontroller; A computer having the same temperature process control method as the microcontroller, and displaying a temperature change on a screen and programmed to control the temperature by a graphical user interface (GUI) method; The microcontroller and the computer form a network, the remote controller comprising a communication module that enables the temperature control of the heat treatment device through the microcontroller, primarily in the computer Is controlled as I / O to perform temperature process control, and in case of computer failure, the control right has a fail-safe concept of transferring to a microcontroller.

In addition, the microcontroller and the computer automatically set the coefficients of the PID controller by an automatic tuning method, and the maximum slope R and overshooting occur to return to the set point. It is characterized by setting the coefficient of the PID controller automatically by the auto-tuning method by setting 1/2 of the time L1 to the delay time as the delay time L.

In addition, the communication module, characterized in that it comprises a distributed data collection module to control a plurality of heat treatment equipment from the computer.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram showing an embodiment of a temperature process control apparatus for a heat treatment apparatus according to the present invention, in which the control target is an electric furnace.

Referring to FIG. 1, there is an electric furnace 1, a temperature sensor 3 at the next stage of the electric furnace 1, and an amplifier 5 at the next stage of the temperature sensor 3. Next to the amplifier 5 is an A / D converter 7, a first communication module 9, and a microcontroller 11. Again, the microcontroller 11 is connected to the main computer (personal computer) through the second communication module (15). And the LCD 15 and the triac 13 which are controlled by the microcontroller 11.

The temperature sensor 3 is a component for measuring the temperature of the electric furnace by an electric quantity (voltage), and the amplifier 5 is a component for amplifying the voltage output by the temperature sensor 3.

The temperature sensor 3 outputs a voltage proportional to the temperature of the electric furnace. However, the temperature sensor 3 has a very small voltage of several mV. Therefore, in a digital circuit operating at a voltage of about 0 to 5 [V], a voltage of several mV is not suitable for handling. In addition, noise may invade the output voltage of the temperature sensor 3 under the influence of high frequency noise, etc., introduced from the ambient environment for measuring the temperature. It is configured to amplify the output voltage of 3). The voltage of several mV output by the temperature sensor 3 is amplified by the amplifier 5 and becomes several volts.

In addition to the amplifier 5, it is necessary to filter the output signal of the sensor 3 and design it to be resistant to noise. For example, it is preferable to insert a filter at the next stage of the temperature sensor and then amplify the circuit, or to perform electrostatic shielding to prevent noise from entering. In Fig. 1, only the most important amplifier 5 is shown, not a detailed configuration.

Next, the A / D converter 7 next to the amplifier 5 is configured to digitize the voltage output by the temperature sensor 3 so that the digital circuit can recognize it.

Next, the microcontroller 11 is a part in charge of substantial temperature process control. In this embodiment, a PIC microcontroller developed by Microchip was used. PIC microcontroller is a microcontroller that is composed of one chip and contains various peripheral devices such as A / D converter, timer, memory and I / O. In the present embodiment, since the microcontroller 11 does not have an A / D converter, the A / D converter 7 is separately configured outside the microcontroller 11, but the A / D converter 7 is built in. If the microcontroller 11 is used, it is not necessary to configure the A / D converter outside the microcontroller 11 without following the present embodiment. In this case, the construction of the temperature process control device will be much simpler.

The microcontroller 11 executes a temperature process control program to perform temperature process control. Briefly, the temperature process control algorithm used in this embodiment is basically a PID control method, and an automatic tuning method is introduced to automatically set the coefficients of the controller, and the coefficients are back in case the coefficient setting is out of the error range. Correction was made by word technique. Detailed description of the temperature process control program will be described later. The microcontroller 11 displays the temperature process control results or various items through the LCD 15.

Next, the first communication module 9 is configured to connect the A / D converter 7 and the microcontroller 11 by communication. In this embodiment, RS-232C and RS-485, and communication It was constructed using the protocol. The RS-232C is an interface method commonly used for serial communication, and the RS-485 is an interface method commonly used when collecting data in a distributed system. In this embodiment, RS-232C as described above was introduced to control the temperature of the electric furnace at a long distance, and RS-485 was introduced to control a plurality of electric furnaces with one controller. However, when there are one electric furnace or heat treatment equipment to control, it is not necessary to use RS-485. If the temperature process is controlled at a short distance rather than a long distance, RS-232C is not used. You may comprise a temperature process controller.

Next, the triac 13 is configured to switch the power input to the electric furnace 1 in response to the control signal of the microcontroller 11. BACKGROUND With the development of the power electronic field, various power semiconductor devices have been developed. Large-scale power semiconductors have also been developed. The triac is a representative power semiconductor device capable of controlling AC power in both directions. In the present embodiment, the triac 13 is used as a switching element, but in a place where it is difficult to use a semiconductor element as a switching element due to poor surrounding environment, it is also possible to use a relay as a mechanical switching element without following this embodiment. .

Next, the second communication module 17 is configured by using the same RS-232C, RS-485, and communication protocol as the first communication module 9, which is a plurality of temperature process controllers in the main computer 19. It can be configured to collect data from or transmit data to multiple temperature process controllers. In addition, the introduction of the second communication module 17 enables remote control to about 1.2 km.

Next, the main computer 19 is programmed to facilitate the temperature process control, monitoring, management, etc. by the graphic screen processing by the GUI method, and controls the temperature of the electric furnace 1 in conjunction with the microcontroller 11. In order to connect to the second communication module 17.

In the case of large-scale systems such as factories, it is common to control all the systems in the premises using a GUI method from the main computer in the central control room. Therefore, a personal computer (main computer) was introduced so that this temperature process control device can also be controlled by the GUI method, and the temperature process control program was appropriately configured. The temperature process control program was written using Windows as an operating system to operate on the main computer 19, and the object-oriented language 'Visual C' was used as the language. The use of object-oriented language makes the temperature process control program excellent in its upgrade and maintenance functions.

In the present embodiment, the temperature process controller 10 and the main computer 19 centered on the microcontroller 11 are configured to allow the temperature process control to be dual. Since the temperature controller 10 has a microcontroller 11 and an LCD 15, the temperature of the electric furnace 1 can be controlled alone, and the control results can be displayed through the LCD 15. Of course, it is not comparable to the GUI method using the main computer 19, but it is possible to display the control results in a character or simple graphics through the LCD (15). Depending on what is displayed on the LCD 15, the operator resets the temperature or takes the appropriate action.

In this manner, the temperature process controller 10 alone may perform temperature process control, and the temperature process controller 10 and the main computer 19 may be linked to control the temperature of the electric furnace 1. When the main computer 19 and the temperature process controller 10 interlock to control the temperature, the temperature process controller 10 serves as an I / O of the main computer 19. That is, the microcontroller 11 of the temperature process controller 10 transmits the temperature value of the electric furnace 1 measured by the temperature sensor 3 to the main computer 19 through the second communication module 17. The main computer 19 grasps the temperature state of the current electric furnace 1 by the temperature control program, and outputs an appropriate control signal to the microcontroller 11 through the second communication module 17. The microcontroller 11 controls the temperature of the electric furnace 1 by controlling the triac 13 according to data downloaded from the main computer 19, that is, a control signal.

The reason why the microcontroller 11 is capable of controlling the temperature process alone and the temperature process control in conjunction with the main computer 19 is due to the duplication of the temperature process control system. The algorithm was applied. When the main computer 19 stops operating due to an unexpected accident, the control right is transferred to the microcontroller 11 and the temperature process control of the electric furnace 1 is performed by the temperature process controller 10 around the microcontroller 11 alone. It was configured to do.

Next, Fig. 2 (a) is a single system configuration diagram of a temperature process control device for a heat treatment apparatus according to the present embodiment, which is a schematic configuration diagram when remotely controlling the temperature of one electric furnace 1, and Fig. 2 (b) is a multiple system configuration diagram of a temperature process control device.

Referring to FIG. 2A, the temperature process control apparatus 10 according to the present embodiment receives a temperature signal from the electric furnace 1 and outputs an operation signal to the electric furnace 1. And it is connected to the main computer 17 and the RS-232C communication module 21.

Referring to FIG. 2 (b), there are N electric furnaces, and each electric furnace is connected to a temperature process controller configured in the present invention, and N temperature process controllers are connected to the RS-485 communication module 23. The RS-485 communication module 23 is connected to the RS-232C communication module 21, and the RS-232C communication module 21 is connected to the main computer 17.

As described above, the temperature process control apparatus according to the present invention uses RS-485 and RS-232C communication modules 21 and 23, in which case the controllable distance is extended to about 1.2 km.

Next, the temperature process control algorithm applied in the present invention will be described.

The basic control algorithm is a PID control algorithm as shown in the following equation (1).

e (k): Error M ₀ : MV when error is 0 K _p : Proportional band

T _s : Sampling period T _i : Integral time T _d : Differential time

In the present invention, the PID controller is configured to obtain the best control accuracy, and an experimental technique for setting a correction zone, which is a region for determining that the control is in a steady state, is set between a target value of 1% and 0.2% for each temperature step.

In addition, in the present invention, the automatic tuning technique is used to automatically set the coefficient of the PID controller, and in the low temperature region, the coefficient setting by the automatic tuning technique may be out of the error range, so that the coefficient is corrected by the backward technique. Since the backward technique is a known technique, a detailed description thereof will be omitted.

Not all heat treatment equipment have the same temperature characteristics. In other words, because the output of the input power is different for each device, even if the same power is supplied for the same time, the temperature change is different. For this reason, most temperature process controllers developed in the related art can perform temperature process control only for specific heat treatment equipment. That is, it can be used only as a dedicated temperature process controller. Therefore, there is a problem in that the economic burden because it is necessary to purchase a separate temperature process controller according to the control target. In the present invention, in order to solve this problem, that is, to realize a general-purpose temperature process controller that is flexible to the control object, the above-described automatic tuning technique is applied. Figure 3 is an exemplary view for explaining the automatic tuning method applied in the present invention.

In the graph of Fig. 3, the horizontal axis is the time axis and the vertical axis is the temperature axis. That is, the graph of FIG. 3 graphically shows the temperature change of the electric furnace 1 with time.

Auto-tuning technique, first, the database of the characteristics of the electric furnace (1) to be controlled through the experiment. Then, temperature process control is performed according to the created database. Experiments on the control object, once at the microcontroller 11 or the main computer 19, by specifying an arbitrary temperature (set point1), controlling the triac (13) to turn on the electric furnace 1, The temperature change over time is measured by the temperature sensor 3. When the temperature is measured and reaches the specified temperature (set point 1), the triac 13 is turned off to cut off the power flowing into the electric furnace 1. That is, the electric furnace 1 is turned off electrically. Then, the temperature sensor 3 continuously measures the temperature change of the electric furnace 1. Since the temperature is so great inertia, turning off the electric furnace 1 does not stop the rise immediately, but an overshoot occurs as shown in FIG. Controlling an object having inertia, such as temperature process control or motor control, is difficult to precisely control due to such overshoot.

After a certain time after the electric furnace 1 is turned off, the temperature of the electric furnace 1 stops rising and falls. When the temperature decreases and reaches the previously set temperature value (set point1), the time (t1 to t2), that is, L1 until the time after the first overshoot has occurred is measured, and the slope of the temperature rise section (ramp section) (R1) Measure The maximum slope of R1 is determined as R, and 1/2 of L1 is determined as L. When R and L are determined, the parameter values necessary for PID control are obtained by the Gigola-Nichols technique, and temperature process control is performed according to the parameter values. Since the Jigol-Nichols technique is widely used in obtaining coefficients of a PID controller, a detailed description thereof will be omitted.

In order to obtain a more accurate coefficient value, the second temperature set point (set point 2) is reset again, and the temperature is raised to the second set point (set point 2) in a similar manner as before, and the set temperature (set point 2) is reached. The triac 13 is turned off. Second, the slope (R2) is measured in the section of increasing the temperature, and the maximum slope of the slope is determined as R. After the first setting value (set point1) is reached and the second setting value (set point2) is reached, the time (t1 to t3) and L2 are measured, and half of L2 is determined as L. The parameter value required for PID control is obtained by the Gigola-Nichols technique.

Next, with reference to the accompanying flowchart of the program of the temperature process control apparatus for heat treatment equipment according to an embodiment of the present invention.

4 is an overall flowchart of the temperature process control program. Looking at the flowchart, it starts and displays the basic temperature process control screen on the monitor once. (S1) Next, the operator needs to control the temperature at the desired temperature or at a time or step to maintain an arbitrary temperature. Each step is inputted (S2). Next, the control mode is selected. The temperature is controlled by the single-step mode or the multi-step mode. (S3) The single-step mode is selected. If the temperature rises up to the set temperature, the Triac is turned off to suppress the temperature rise and the temperature rises. The graph form to be drawn is displayed on the monitor. (S5) Next, the temperature is kept constant (hold control), It displays the material temperature to a digital value and the graph. (S9)

On the other hand, when the multi-stage mode is selected, the graph form on which the temperature rises is drawn is displayed on the monitor (S6), and then the temperature is increased. (Ramp coontrol, S7) The temperature of the electric furnace is set. When it reaches, from now on, it enters the hold control which keeps the temperature constant (S8) and displays the current temperature as digital value and graph (S9). When it is finished, it is checked whether the temperature rise step is completed (S10). If there is a next step, the above process is repeated again, and if there is no next step, it ends.

FIG. 5 shows a control screen on which a temperature process control program is executed. As shown in FIG. 5, since it is executed in a GUI method on Windows, the operator can control the temperature with a simple operation. Easy temperature process control In the graph shown in Fig. 5, the horizontal axis is the time axis and the vertical axis is the temperature axis. In FIG. 5, the time axis is up to 650 minutes, the temperature axis is up to 1600 °, and the process of increasing the temperature in four steps is shown graphically. The section in which the temperature rises with time changes is a ramp control step, and the section in which the temperature is constant with respect to the time change is a hold control step in which the temperature is kept constant by a backward technique. When the temperature rise and temperature maintenance for the first stage is finished and the temperature is maintained at an arbitrary temperature in the second stage, the lamp control process and the hold control process are repeated again (S3 ~ S10). .

The screen shown in FIG. 5 is by way of example only. The temperature process control program is programmed so that the time axis and the temperature axis are not limited. In other words, when the operator inputs the step temperature and the temperature holding time, the function that draws the graph form accordingly displays the axis by setting the time axis and the temperature axis appropriately. In addition, the ramp time and holding time are programmed to be freely adjusted to the process.

While the temperature process control program is running, the triac 13 is turned on to apply electric power to the electric furnace 1 at the portion where the temperature is to be raised. When power is applied to the electric furnace 1, the applied power is converted into thermal energy and the temperature of the electric furnace 1 rises. The temperature sensor 3 outputs a voltage proportional to the temperature of the electric furnace 1 in real time, and the microcontroller 11 checks the output voltage of the temperature sensor 3 at regular intervals.

When the microcontroller 11 and the main computer 19 are connected to the communication module 17 for temperature process control, the temperature value checked by the microcontroller 11 is transmitted to the main computer 19. And since the checked temperature is displayed on the monitor of the main computer 19, the operator can know the entire process of control in real time through the screen. When the temperature process control is performed in the main computer 19, the microcontroller 11 transmits data corresponding to the output voltage of the temperature sensor 3 through the second communication module 17 of FIG. 1. When performing temperature process control by the controller 10 alone, the microcontroller 11 analyzes the output voltage of the temperature sensor 3 and operates as a controller by comparing with the set temperature value.

As described above, the temperature process control apparatus for a heat treatment apparatus according to the present invention is capable of precise temperature process control by applying a PID control method, an automatic tuning technique, and a backward technique. And it can be applied to temperature process control of various heat treatment equipment by applying automatic tuning technique. In addition, there is an advantage that the operator can easily control the temperature by the introduction of the GUI method, the temperature process control through the screen even at a distance using a communication module. The temperature process control device for heat treatment equipment can be used for temperature process control of various furnaces and heat treatment equipments used in ceramics, steelmaking, petrochemical, air-conditioning, cold storage, and farm.

Claims (3)

A temperature sensor which detects the temperature of the heat treatment apparatus as an electric quantity; A transducer for converting the output signal of the temperature sensor into an electrical signal that can be recognized by a digital circuit; A microcontroller that analyzes the output signal of the transducer and controls the temperature by a PID control method, uses auto-tuning to set the coefficient of the PID controller, and corrects the coefficient by a backward method when the set coefficient is out of an error range; A switching element for switching power input to the heat treatment device according to the control signal of the microcontroller; A computer having the same temperature process control method as the microcontroller, and displaying a temperature change on a screen and programmed to control the temperature by a graphical user interface (GUI) method; The microcontroller and the computer constitute a network, and the computer includes a communication module for allowing the remote computer to control temperature processing of the heat treatment device through the microcontroller. First of all, the computer controls the microcontroller as I / O to perform temperature process control, and in case of computer failure, the process has a fail-safe concept of transferring control right to the microcontroller. Control unit. The method of claim 1, wherein the microcontroller and the computer automatically set the coefficients of the PID controller by an automatic tuning method. PID is automatically tuned using the maximum slope (R) of the temperature rise section and 1/2 of the time (L1) from overshooting to the set point again as the delay time (L). A temperature process control device for a heat treatment machine, characterized in that to automatically set the coefficient of the controller. The apparatus of claim 1, wherein the communication module includes a distributed data collection module to control a plurality of heat treatment devices in the computer.