JPH08178551A - Temperature control method in combustion control system - Google Patents

Abstract

PURPOSE: To enable an accommodation of a baked material under a control of temperature to be attained for a non-specified element while being separated from a control of a heater by a method wherein a target temperature is corrected by a first feedback loop in response to the non-specified element of baked material and an output of the heater is followed to the corrected target temperature in a second feedback loop. CONSTITUTION: A target temperature M(k) in a baking chamber indicating in response to an aging pattern stored in a memory 20 is corrected by a first calculating means 13 forming a first feedback loop with an output Δ(k) of an adjusting means 19 with an output Ti(t) of a baking chamber temperature sensor 10 for use in detecting a temperature of the baking chamber being applied as an input to get a corrected target temperature M'(k). A difference ε(k) between the corrected target temperature M'(k) and a flame temperature T1(k) of the heater 16 acting as a baking burner forming the second feedback loop is calculated and outputted to a PID controller 15. The PID controller 15 may output a control input (u) to the heater 16 in such a manner that an absolute value of the difference ε(k) may be reduced and then the heater 16 may apply heat to the combustion chamber in response to the output.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a combustion control system for a furnace for firing a fired product such as ceramics, and more particularly to a control method for controlling the temperature inside the furnace by combustion control.

[0002]

2. Description of the Related Art As shown in FIG. 3, the temperature pattern of a firing chamber when firing a ceramic is as follows: after raising the temperature of the firing chamber to a set firing temperature at a predetermined rate of rise, The time-dependent pattern is generally maintained for the required time and then lowered at an appropriate descent rate. When the temperature is lowered, if the cooling is too rapid, the fired product may be cracked. On the contrary, if the temperature is too slow, the color may become black or the gloss may deteriorate.

Regarding the combustion control and temperature control of a furnace for firing ceramics, there is an example disclosed in JP-A-5-172470. In the technique disclosed in this publication, the temperature inside the firing chamber is detected, and based on the detected temperature, the fuel control valve that supplies fuel to the firing burner for controlling the temperature inside the firing chamber of the furnace is controlled. And the flow of control is
It is as shown in FIG. In the loop from the temperature setting to the firing chamber in this control flow, as shown in FIG. 9, the deviation ε (t) between the set target temperature M (t) and the measured temperature T2 (t) of the firing chamber is Input to the controller, the controller outputs a signal u (t) for controlling the heater in the direction in which ε (t) decreases. The heater receives u (t) as an input and the heat represented by the heater flame temperature T1 (t). Is output and the temperature of the firing chamber formed by the input of heat represented by the heater flame temperature T1 (t) is detected, and the measured temperature T
2 (t) is used to calculate the deviation ε (t).

[0004]

By the way, the temperature change in the firing chamber is influenced by many uncertain factors.
For example, the shape, quantity, storage location, and physical properties of the fired product affect the temperature distribution in the firing chamber, and the limited number of temperature detectors cannot accurately detect the temperature distribution in the firing chamber. In consideration of these uncertain factors, the temperature control loop configuration of FIG. 9 cannot easily realize a hybrid configuration including a nonlinear element of the controller design and the heater itself. Furthermore, it is difficult to adjust the delay (DELAY), which is a characteristic of the combustion system, in consideration of the sampling in order to consider the delay (DELAY) under the same control loop for controlling the heater and controlling the uncertainties.

That is, the above publication does not disclose details of practical temperature control for realizing a predetermined temperature (temporal pattern).

An object of the present invention is to realize temperature control in the temperature control of the firing chamber, taking into consideration the influence of uncertain factors that affect the temperature distribution in the firing chamber, such as the shape and quantity of the fired product, the storage location and the physical properties. It is in.

[0007]

In order to achieve the above object, the present invention provides a shelf arranged in a firing chamber on which a fired product is placed, a heater for supplying heat to the firing chamber, and a heater for the heater. A fuel control valve for controlling the amount of fluid fuel supplied, temperature detection means for detecting the temperature in the firing chamber, and a deviation between the output of the temperature detection means and a target temperature indicated by a preset aging pattern as inputs. In a temperature control method of a combustion control system in a firing furnace, which comprises a controller for controlling the fuel control valve, a control loop for temperature control, a target temperature indicated by the temporal pattern, and an output of the temperature detection means. And a first feedback loop for correcting with a correction value calculated based on the target temperature indicated by the aging pattern, and a temperature near the heater is detected, and a deviation between this temperature and the corrected target temperature is detected. Calculated, and a second feedback loop that the calculated deviation as an input to the controller, in which characterized in that it is configured.

The correction value can be calculated by using fuzzy inference.

[0009]

The control for correcting the target temperature corresponding to the uncertain factor of the fired product is first performed in the first feedback loop, and the control for making the output of the heater follow the corrected target temperature is performed in the second feedback loop. Done. The output of the heater is controlled by feeding back the output of a temperature detector that measures the temperature in the vicinity of the heater, and the temperature of the firing chamber is irrelevant. Since the control including the response to the influence of the uncertainties of the fired product, that is, the control of bringing the temperature of the firing chamber close to the target temperature of the set aging pattern is performed in a control loop different from the control of the heater itself, It can be realized regardless of the response delay of the heater and the operating characteristics.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a schematic view of the configuration of a firing furnace for pottery, and a firing chamber 1 is provided in the firing furnace, and a secondary combustion chamber 2 is formed so as to be connected to the upper portion of the firing chamber 1 and a secondary combustion chamber is formed. The chamber 2 is connected to the exhaust stack 3 via the catalyst layer 12. Two
The secondary combustion chamber 2 is provided for reburning carbon monoxide and carbon in the exhaust gas generated when operating in a reducing atmosphere. A firing burner 4 is installed below the firing chamber 1, and a secondary burner 5 is provided in the secondary combustion chamber 2.
Fuel is supplied to the firing burner 4 through a fuel control valve 6-1 and air is supplied through an air control valve 7-1.

Similarly, fuel is supplied to the secondary burner 5 via the fuel control valve 6-2, and air is supplied via the air control valve 7-2. When operating in a reducing atmosphere, the temperature may be high, and due to the action of the catalyst, there is a case where the secondary burner 5 is burned again by simply feeding air without supplying fuel. Further, in the firing chamber 1, an oxygen detector 8 for detecting the oxygen concentration, a carbon monoxide detector 9 for detecting the carbon monoxide concentration, a firing chamber temperature detector 10 for detecting the temperature, and a flame. Temperature detector 1
0-1 are arranged, and the shelf boards 11 for arranging the pottery works for firing are arranged vertically in two stages. A plurality of temperature detectors 10 are arranged to detect temperatures at a plurality of places in the firing chamber, and a flame temperature detector 10-1 is arranged to detect temperatures in the vicinity of the combustion flame of the firing burner 4 which constitutes the heater 16. Has been done. The detection output of the flame temperature detector 10-1 is the output T1 of the firing burner 4 which constitutes a heater.
(T). The heater 16 mentioned here is configured to include the firing burner 4, the fuel control valve 6-1 and the air control valve 7-1.

The control flow basically follows that shown in FIG. 10, but the control loop from temperature setting to temperature formation in the firing chamber is as shown in FIG. 1 at each sampling point of the temporal pattern. The target temperature M (k) is corrected with the adjustment value Δ (k) of the temporal pattern, and the target value M ′ of the heater output is corrected.
The first calculation means 13 for outputting as (k) and the second calculation means 14 for calculating and outputting the deviation ε (k) between the heater output target value M ′ (k) and the heater output measurement value T1 (t). And P that outputs a control signal u (k) for controlling the heater 16 in a direction to reduce the deviation ε (k) by inputting the deviation ε (k).
The ID controller 15, the heater 16 that operates by receiving the control signal u (k) to generate heat, the heat output from the heater 16 is detected, and the second calculation means 14 is used as a measured value T1 (k) of the heater output. To output flame temperature detector 10-
1, a firing chamber temperature detector 10 that detects the temperature of the firing chamber formed by the heat output from the heater at a plurality of locations and outputs the temperature as the firing chamber temperature T2 (t), and the firing chamber temperature T2 (t).
Is input to calculate the adjustment value Δ (k) of the temporal pattern and outputs the adjustment value Δ (k) to the first calculating means 13.

The adjusting means 19 is a baking chamber temperature detector 10.
It handles (a plurality of) outputs, flexibly judges the temperature change pattern in the firing chamber in consideration of the uncertainties of the fired product, and outputs the adjustment value Δ (t) of the temporal pattern accordingly. It is configured by applying neural network technology, fuzzy technology, and technology that fuses both. In this embodiment, the adjusting means 19 to which the fuzzy technique is applied is used.

As shown in FIG. 4, the adjusting means 19 uses the data T2 (t) (here, ti (t) from the temperature detectors 10 for a plurality of firing chambers, where i = 1 to N are a plurality of firing chambers. (Indicating the respective numbers of the temperature detectors 10) is input and the temperature error e
A data conversion unit 19A for calculating, storing and outputting r (k) and a temperature error change amount ec (k), and a temperature error er (k) and a temperature change change amount ec connected to the data conversion unit 19A.
It is configured to include a fuzzy rule unit 19B that receives (k) as an input and calculates and outputs an adjustment value Δ (k). In the control flow shown in FIG. 10, the memory 20 is set with time →
It is in charge of the temperature setting part, stores the temporal pattern of the firing chamber temperature, and outputs the target temperatures M (k) and M (k-1) that change with the passage of time. In the above description, the variable t is represented by t = kTo, To is the sampling period of the temperature detector, k is the number indicating the sampling number, and k = 0, 1, 2, ...... is.

The operation of the adjusting means 19 having the above construction will be described below. First, the data conversion unit 19A calculates the average temperature T ₂ (k) of the input ti (t) (i = 1 to n) by the following equation.

[0016]

[Equation 1]

The data conversion unit 19A uses the temperature M (k-1) of the temporal pattern input from the memory 20 and the calculated T ₂ (k) to calculate the temperature error er ( k) is calculated. Further, using T ₂ (k−1) stored at the previous sampling, T ₂ (k) calculated this time, and temperatures M (k−1) and M (k) of the temporal pattern input from the memory 20, The temperature error change amount ec (k) is calculated by the equation (2-2). Er (k) expressed by the following equation,
ec (k) is the temperature error and the temperature error change amount in the k-th sampling, respectively. er (k), ec
When the calculation of (k) is completed, the T ₂ (k) calculated this time becomes
It is stored and stored as T ₂ (k−1).

[0018]

[Equation 2]

M is a positive number smaller than the minimum value of the temperature change at one sampling interval in the aging pattern of the firing chamber target temperature, and 0 <m <┃M (k) -M (k-1) ┃ (aging It is a coefficient represented by (applicable to k of all areas of the pattern).

The calculated er (k) and ec (k) are sent to the fuzzy rule section 19B. Fuzzy rule section 19B
Evaluates the input er (k) and ec (k), and calculates the correction amount Δ (k) by the following equation. F represents a fuzzy inference relationship.

Δ (k) = F (er (k), ec (k)), k = 0, 1, ... (3) That is, the temperature change characteristic of the previous sampling is used as the antecedent part, and the next aging pattern Fuzzy inference is performed using the correction amount for the value as the consequent part. 5, 6 and 7 show examples of membership functions for evaluating the temperature error and the temperature error change amount and outputting the correction amount.

First, the calculated er (k) is applied to the horizontal axis of FIG. 5, and the illustrated NL, NS, ZO, PS, PL are shown.
Read the value of each graph. Horizontal axis in Figure 5 emin ~ emax
Is the width of the temperature error that you actually want to evaluate.
The minimum possible er (k) (maximum on the negative side) is assumed to be e
The maximum er (k) (maximum on the positive side) that is assumed for max is
Each is set. Further, en is placed between emin and the origin (error 0) for a negative temperature error, which is ideal (ZO) and when the negative error is very large (NL).
Shows the value of the temperature error that becomes the boundary point that divides, and ep is
The temperature error that is the boundary point between the ideal case (ZO) and the case where the positive error is very large (PL) placed between emax and the origin (error 0) for the positive temperature error Indicates a value. The value of is selected and set in advance as a control constant. For example, a temperature error er of −100 ° C. to 100 ° C.
When trying to evaluate (k), it is determined by equally dividing as follows: emin = -100 ° C, en = -50 ° C, 0 = 0 ° C ep = 50 ° C, emax = 100 ° C.

Next, ec (k) (temperature error change amount) is applied to the horizontal axis of the membership function of FIG.
The values of the K and FA graphs are read.

The fuzzy inference rules applying the read values of each graph are given in Table 1.

[0025]

[Table 1]

The values read in FIGS. 5 and 6 are applied to the fuzzy inference rules given in Table 1 of the graph of FIG. 7 to obtain the correction amount indicated by the values on the horizontal axis. Δ6 and Δ3 on the horizontal axis of FIG. 7 indicate the maximum value on the decreasing side and the maximum value on the increasing side of the temporal pattern correction amount, respectively. For example,
When the maximum value on the decreasing side is -30 ° C and the maximum value on the increasing side is 30 ° C, 0, Δ1, Δ2, Δ4, and Δ5 are simply divided into equal parts. 0 = 0 ° C Δ1 = 10 ° C Δ2 = 20 ° C Δ3 = 30 ° C Δ4 = -10 ° C Δ5 = -20 ° C Δ6 = -30 ° C.

The adjusting means 19 performs the correction amount Δ by the above-mentioned procedure.
(K) is calculated, and the calculated Δ (k) is calculated by the first calculation means 1
Output to 3. FIG. 8 shows an operation procedure of the adjusting means 19. The illustrated procedure is repeated every sampling period.

M (k) is inputted from the memory 20 to the first calculating means 13, and Δ (k) inputted from the adjusting means 19 is added to the target value M '(k of the heater output. )
Is output to the second calculation means 14. The second calculation means 14 has a deviation ε (k) between M ′ (k) input from the calculation means 13 and the heater output T1 (k) which is the measured temperature near the flame input from the flame temperature detector 10-1. ) Is calculated,
Output to the PID controller 15. The PID controller 15 outputs a control signal u (k) for controlling the heater 16 in a direction in which the absolute value of the input deviation ε (k) decreases, and outputs the output of the heater 16, that is, the combustion amount of the firing burner 4. Control. The output of the heater 16 is represented by the temperature near the combustion flame of the burning burner 4, and is fed back to the second computing means 14 as the output T1 (k) of the flame temperature detector 10-1. That is, the second calculation means 14, P
ID controller 15, heater 16 (actually fuel control valve 6-1, air control valve 7-1) and flame temperature detector 10-
Second feedback loop composed of 1 (combustion control loop)
Can be controlled so that the heater output T1 (k) matches the target value M ′ (k) regardless of the temperature of the firing chamber, and the control is simplified.

On the other hand, the temperature of the firing chamber is detected by the plurality of firing chamber temperature detectors 10, converted into the correction amount Δ (k) by the adjusting means 19 and output to the first computing means 13 as described above. It That is, the temperature of the firing chamber is determined by the first calculation means 13,
It is controlled by the first feedback loop (temperature control loop) composed of the firing chamber temperature detector 10 and the adjusting means 19. This temperature control loop does not directly relate to the combustion control of the firing burner 4, but directs the heater output based on the firing chamber temperature. Then, the combustion control loop controls the heater so that the heater output becomes the instructed heater output. Therefore, if the firing chamber temperature does not reach the temperature M (k) indicated by the target aging pattern of the firing chamber temperature even if the heater output reaches the instructed heater output, the adjusting means sets the positive correction amount Δ (k ) Is output to increase the heater output target value M ′ (k).

According to this embodiment, it is possible to separate the control of the indeterminate element of the burned material from the control of the heater, facilitate the response of the indeterminate element of the fired object, and deal with various adjusting means. It is possible to automatically correct the aging pattern. Furthermore, the delay of firing temperature (DELAY), the rise time of the control loop of the heater, the selection of the sampling cycle of the combustion control system, etc. can be adjusted with a clear relationship. By doing so, fine temperature control can be realized.

[0031]

According to the present invention, it is possible to deal with the uncertain factor of the burned material in the temperature control separately from the control of the heater, and it is easy to deal with the uncertain factor of the burned material.

[Brief description of drawings]

FIG. 1 is a control block diagram showing an embodiment of the present invention.

FIG. 2 is a sectional view showing an example of a firing furnace to which the present invention is applied.

FIG. 3 is a conceptual diagram showing an example of a temporal pattern of the temperature of a firing furnace.

FIG. 4 is a control block diagram showing details of a part of the embodiment shown in FIG.

FIG. 5 is a diagram showing an example of a membership function applied to the present invention.

FIG. 6 is a diagram showing an example of a membership function applied to the present invention.

FIG. 7 is a diagram showing an example of a membership function applied to the present invention.

FIG. 8 is a procedure diagram showing an operation procedure of the adjusting means shown in FIG.

FIG. 9 is a control block diagram showing an example of a conventional technique.

FIG. 10 is a control loop diagram showing an example of a conventional technique.

[Explanation of symbols]

1 Firing Chamber 2 Secondary Combustion Chamber 3 Exhaust Cylinder 4 Firing Burner (Heater) 5 Secondary Burner 6-1 Combustion Control Valve 7-1 Air Control Valve 8 Oxygen Detector 9 Carbon Monoxide Detector 10 Firing Chamber Temperature Detector 10 -1 Flame Temperature Detector 11 Shelf Board 12 Catalyst Layer 13 First Computing Means 14 Second Computing Means 15 PID Controller 16 Heater 18 Firing Kiln 19 Adjusting Means

Claims (2)

[Claims] 1. A shelf in which a fired product is placed in a firing chamber, a heater for supplying heat to the firing chamber, a fuel control valve for controlling the amount of fluid fuel supplied to the heater, and a heater in the firing chamber. A firing furnace comprising: a temperature detecting means for detecting a temperature; and a controller for controlling the fuel control valve with an input of a deviation between an output of the temperature detecting means and a target temperature indicated by a preset aging pattern. In a temperature control method of a combustion control system, a first temperature indicated by the aging pattern is corrected by a correction value calculated based on an output of the temperature detecting means and a target temperature indicated by the aging pattern. A feedback loop; a second feedback loop that detects the temperature in the vicinity of the heater, calculates a deviation between this temperature and the corrected target temperature, and uses the calculated deviation as an input to the controller;
A temperature control method for a combustion control system, wherein: 2. The temperature control method for a combustion control system according to claim 1, wherein the correction value is calculated by fuzzy inference.