JPH0323835B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control method for a plurality of furnaces, and particularly to a control method for a plurality of furnaces in which controlled variables such as furnace temperature are multivariable.

Conventionally, for example, hot air is supplied from one gas combustion device or electric heating device to multiple furnaces (or one furnace partitioned into multiple zones) to control each furnace (or each zone) to a desired temperature. This is extremely difficult and is rarely practiced. The first example is a common example that has been carried out conventionally.
Shown in Figures a and b. A blower 5 that supplies hot air in the direction of the arrow to a combustion furnace 3 that communicates with a duct 2 via a damper 1, and a plurality of furnaces 4a to 4c (or one furnace 4 partitioned into a plurality of zones 4a' to 4c').
and each furnace 4a to 4c (or each zone 4a' to 4
c') and each damper 6a connected in series.
~6c and each non-interference device 7a~7c consisting of, for example, a three-way valve equipped with a cooling device (not shown).
and thermocouples 8, 9a to 9c that respectively detect the temperature of the duct 2 and the temperature of each furnace 4a to 4c (or each zone 4a' to 4c').

First, the damper 1 is set to a predetermined opening degree, and hot air is passed through the dampers 6a to 6c to each furnace 4 by the blower 5.
a to 4c (or each zone 4a' to 4c'). Then, the temperature T ₂ ~ is determined by thermocouples 9a to 9c.
In order to control the temperature of each furnace (or each zone 4a' to 4c') to a desired value by detecting T ₄ and adjusting the opening degree of the dampers 6a to 6c, each cooling device controls the temperature T ₂ ~Control T ₄ , each damper 6
The non-interference devices 7a to 7c prevent the opening and closing of one of the dampers a to 6c from affecting each furnace temperature (or the temperature of other zones), so that each furnace temperature (or the temperature of each zone) is maintained at the desired set value. so that PID
The temperature was controlled by controlling the temperature.

However, as mentioned above, even if it is possible to manually control the system using a non-interference device equipped with a cooling device, the operation is complicated and it is extremely difficult to operate it efficiently. Moreover, it consumes unnecessary heat, which is contrary to energy conservation, and requires an expensive non-interference device with a cooling device, which is a factor in increasing costs. Further, depending on the opening degree of the damper 1, there have been cases where control cannot be performed even through a non-interference device.

Therefore, it is possible to measure a large number of measured quantities (in this embodiment, including a large number of controlled variables (in the case of this embodiment, temperatures T ₁ to T ₄ by each thermocouple 8, 9a to 9c) without intervening a non-interfering device. In the case, the temperature T ₂ ~ by each thermocouple 9a ~ 9c
In control (multivariable control) where T ₄ ) varies when any one of a large number of manipulated variables (in the case of this example, the opening degrees of dampers 1, 6a to 6c) is manipulated, the measurement In the prior art, it has been impossible to simultaneously and automatically control each manipulated variable so that each controlled variable reaches a desired value by measuring the amount. Furthermore, due to the correlation between the controlled variable and the manipulated variable of multiple variables, a control method that relies on each pair of controlled variable and manipulated variable has the disadvantage that the stability of the controlled variable is poor and the responsiveness is poor. It was hot.

The purpose of the present invention is to perform multivariable control of multiple furnaces without intervening a non-interfering device, so that each controlled variable can be set to a desired value (set target value) using a detection element for measured variables including the controlled variable of furnace temperature. We have developed a control method (system) for multiple furnaces that simultaneously and automatically controls the manipulated variable of the damper opening to achieve thermal efficiency and energy savings, and control means with further improved stability and responsiveness. The purpose is to provide.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment in which the multiple furnace control method according to the present invention is applied to temperature control of multiple furnaces will be described in detail based on the drawings.

First, this embodiment is shown in FIGS. 2a and 2b. One combustion device 12 that communicates with a duct 11 via a damper 10, a blower 14 that supplies hot air in the direction of the arrow to multiple furnaces 13a to 13c (or one furnace 13 partitioned into multiple zones), and each furnace. 13
a to 13c (or each zone 13a' to 13c')
Dampers 15a to 15 that adjust the internal temperature to a desired temperature
c, stepping motors _M1 to _M3 that adjust the opening degrees of these dampers 15a to 15c, and thermocouples arranged in the duct 11 and each furnace 13a to 13c (or each zone 13a' to 13c'). 16,
It consists of 17a to 17c. Each of the stepping motors M ₁ -M ₄ receives an input signal (indicated by a solid line) and generates an output signal (indicated by a dotted line). Further, an output signal is generated from each thermocouple 16, 17a to 17c. These signals are I/O
(A/D) A/D converted by controller 18
CPU19 (manufactured by Heuretsu Patscard Co., Ltd.)
HP1000M series), where it is calculated and
The controlled signal is sent back to D/D by the controller 18.
The signal is converted into A and applied to the stepping motors _M1 to _M4 of each damper 10, 15a to 15c.

Next, such a control system will be explained in detail based on FIG. 3.

In this method, multiple furnaces 20 to be controlled
, a plurality of temperature control variables (points 17a, 17b, 1
temperature at 7c) Y=Y ₁ Y ₂ Y ₃ (points 16, 17a, 17b,
The temperature at 17c Y ₁ Y ₂ Y ₃ Y ₄ is the multiple manipulated variable of the damper opening (damper 1
0, 15a, 15b, 15c) When U=U ₁ U ₂ U ₃ U ₄ changes, the controlled variable is adjusted to its target value YR=YR ₁ YR ₂ YR _3. The aim is to control the amount of operation so that the

The controlled quantities Y ₁ to _{Y 3} are drawn out from the extraction point 21 and connected to the subtraction points 22 of the target values Y _R1 to _{Y R3} , respectively, and the difference between the controlled quantities and the target values Y ₁ − YR ₁ 〓 〓 Y ₃ − We have obtained YR ₃ = ε ₁ 〓 ε ₃ .

These differences ε ₁ ...ε ₃ are applied to the calculation element C. Element C is a matrix written as C ₁₁ ...C ₁₃ 〓 〓 C ₄₁ ...C ₄₃ , where C ₁₁ ...C ₁₃ 〓 〓 C ₄₁ ...C ₄₃ ε ₁ 〓 ε ₃ = U′c ₁ 〓 U′c ₃ The manipulated variables U'c ₁ ... U'c ₃ are given by linear processing. These manipulated variables are each integrator I ₁
~ I ₄ is applied, an integral action is performed and the quantity Uc ₁ ~
It is applied as Uc ₄ to each manipulated variable U ₁ to _{U 4} .

This quantity Uc is expressed as follows as a result of performing an integral function.

Uc (t) = Uc (t-1) + C ₁₁ ...C ₁₃ 〓 〓 C ₄₁ ...C ₄₃ ε ₁ 〓 ε _3This integral operation includes not only the linear integral function by the integrator, but also the integral function. Or it includes operations similar to this.

Further, the integral operation may include dynamic compensation.

In addition, each element of calculation element C, C ₁₁ ...C ₁₃ 〓 〓 〓 C ₄₁ ...C ₄₃ , is calculated based on the optimal control theory using the control object as a model before automatically controlling the multiple furnaces 20 as the control object. and a simulation of the behavior of the manipulated variables U′c ₁ to U′c ₃ , the manipulated variables U ₁ to U ₃ , and the controlled variables Y ₁ to Y ₃ when giving the target values Y _R1 to Y _R3 , and the most It shall be determined appropriately.
（Control System Design for Furnace by
Using) (CAD“by K.Furuta et al at the
IFAC Symposium on the Theory and
Application of Digital Control, Delhi;
See Session 20, 1982).

Further, the extraction point 21 is the feedback element F
It is connected to the subtraction point 23 via. As a result, a feedback operation is performed on the measured quantities Y ₁ -Y ₄ including the controlled quantities Y ₁ -Y ₃ by linear processing, and is subtractively applied to the manipulated quantities U ₁ -U ₄ . This feedback operation may include dynamic compensation. The feedback output _UF is UF=UF ₁ 〓 UF ₄ = F ₁₁ ...F ₁₃ 〓 〓 F ₄₁ ...F ₄₃ Y ₁ 〓 Y ₃ .

It should be noted that each element of F ₁₁ ...F ₁₃ 〓 〓 〓 F ₄₁ ...F ₄₃ is also determined in advance by the aforementioned optimal control theory and simulation.

Furthermore, the extraction point 24 is connected to the summing point 23 via a feed forward element N. As a result, a feedforward operation, that is, a proportional operation is performed on the target values Y _R1 to Y _R3 by linear processing, and is applied additively to the manipulated variables U ₁ to _{U 4} . This feed forward operation may include dynamic compensation. Feedforward output U _N
is UN=UN ₁ 〓 UN ₄ = N ₁₁ …N ₁₃ 〓 〓 N ₄₁ …N ₄₃ YR ₁ 〓 YR ₃ .

In this case, each element of N ₁₁ ...N ₁₃ 〓 〓 N ₄₁ ...N ₄₃ is also determined in advance by the optimal control theory and simulation as described above.

In this way, as a result of three types of operation inputs being supplied to the manipulated variable U, the manipulated variable U finally becomes as follows.

U = Uc - U _F + U _N A limiter L is interposed in each operating line to stop the integral operation when the sum output Uc - U _F + U _N supplied to the manipulated variable exceeds a predetermined range. (Figure 3).

In FIG. 3, the part surrounded by a dotted line represents the CPU, and the input interface for target values Y _R1 to Y _R3 includes an input/output device I/O-1 for A/D conversion,
The output interface for the manipulated variables U ₁ to U ₄ has D/
Input/output device I/O-2 for A conversion, control amount
An input device I/O-3 for A/D conversion is interposed at the input interface to the backward path of the measured quantities Y ₁ to Y ₄ including Y ₁ to _{Y 3} (FIG. 3).

The multivariable automatic control system configured as described above operates as follows.

First, the multiple furnaces 20 are operated to control the control amount Y ₁ to Y ₃
The initial value of the integral operation is set according to the measured quantities Y ₁ to _{Y 4} including (FIG. 4). Next, the CPU is set to the target value
Read data of measured quantities _Y1 to _Y4 including _YR1 to _YR3 and control quantities _Y1 to _Y3 . The calculation element C, the feedback element F, and the feedback element N of the CPU each perform their calculations according to the values expressed by the determinant described above, and U′c=U′c ₁ 〓 U′c ₄ =C ₁₁ …C ₁₃ 〓 〓 C ₄₁ …C ₄₃ ε ₁ 〓 ε ₃ UF＝UF ₁ 〓 UF ₄ ＝F ₁₁ …F ₁₃ 〓 〓 F ₄₁ …F ₄₃ Y ₁ 〓 Y ₃ UN＝UN ₁ 〓 UN ₄ ＝N ₁₁ …N ₁₃ 〓 〓 N ₄₁ …N ₄₃ YR ₁ 〓 Calculate YR ₃ .

This manipulated variable output needs to be controlled and maintained within a predetermined range. Therefore, it is determined whether each manipulated variable output value is within the range, and if it is within the range, an integral operation is performed, and if it exceeds the range, it is output via limiter L. (Figure 4).

In this way, each manipulated variable U′c ₁ ... is operated by an integrator I ₁ ...I ₄ , and the integration operation is performed so that Uc(t)=Uc(t-1)+U′c ₁ 〓 U′ produces an integral output of c ₄ .

If such a function is introduced, even though the damper opening degree as the manipulated variable is 0 to 100% as in this embodiment, if the integral operation is performed from the start of the operation, the manipulated variable will initially be and the target value ε ₁ …ε ₃
Since this is large, it is avoided that the damper opening degree effectively generates an undesirable manipulated variable signal of 200 or 300%.

In this way, the integrator repeats the integration operation until the difference between the target value and the controlled variable ε=YR ₁ 〓 YR ₃ −Y ₁ 〓 Y ₃ becomes zero, and controls the controlled variable so that it approaches the target value as much as possible. It forms a loop.

Thus, the manipulated variable U U = Uc - U _F + _UN is calculated and output to the controlled object 20 .

In this case, the feedback output UF of the feedback element _F has the function of stabilizing the inherent characteristics of the control system.

On the other hand, the output U _F of the feed forward element N is
It accelerates the rise of the controlled variable Y so that it quickly approaches the target value _YR , and has a particularly great effect at the start of furnace operation. This element N further improves the responsiveness of the control system.

In this way, when the manipulated variable U is output to the controlled object 20, it is delayed for a predetermined time until the next sampling,
The following operation is repeated again.

In the above embodiment, there are three controlled variables and target values,
We have explained the case where there are four manipulated variables and four manipulated quantities, and four measured quantities, but in the case where there are l, n, and m pieces, respectively (l, n, and m are positive integers, and n, m≧l). The present invention is equally applicable thereto.

As is clear from the above embodiments, according to the present invention, a measured quantity including a plurality of controlled variables of the temperature of a plurality of furnaces to be controlled can be measured without intervening a non-interference device. When controlling the manipulated variable so that the controlled variable is adjusted to its target value when it fluctuates due to any of multiple manipulated variables, it is necessary to integrate each of the manipulated variables obtained from the difference between the controlled variable and the target value. Since the operation is performed and applied to each manipulated variable, multivariable control is performed such that each manipulated variable performs its function mutually and independently, and the controlled variable approaches the target value. Additionally, by having this control system perform feedback and/or feedback operations, response is improved and stability is increased, and the furnace temperature of each furnace can be set most efficiently and with the least amount of heat. can.

In addition, the above-mentioned multiple furnaces include not only multiple furnaces as shown in FIG. 2a, but also a single furnace shown in FIG. It also includes cases.

[Brief explanation of drawings]

Figures 1a and b are explanatory diagrams showing conventional embodiments of multiple furnaces (or one furnace partitioned into multiple zones), and Figures 2a and b are illustrations of multiple furnaces (or one furnace partitioned into multiple zones) as control targets. one furnace partitioned into
FIG. 3 is a block diagram of an automatic control system in which the present invention is applied to the object to be controlled, and FIG. 4 is an operational flowchart of the system. 20...Multiple furnaces, _Y1 to _Y3 ...Controlled amount, _Y1 to _Y4
...Measurement quantity, U ₁ to _{U 4} ... Manipulated quantity, Y _R1 to _{Y R3} ...
Target value, ε ₁ ~ ε ₃ ...Difference between controlled variable and target value, U′c ₁ ~
U′c ₄ ... manipulated variable.

Claims (1)

[Scope of Claims] 1. A multiple furnace temperature control method in which hot air heated in a heating device is directly supplied to multiple furnaces connected via dampers to adjust the inside of each furnace to a desired temperature, respectively. Multiple control variables for the furnace temperature Y=Y ₁ 〓 Multiple measured variables including Yl Y ₁ 〓 Ym are multiple control variables for the damper opening U=U ₁ 〓 Un (However, l, n, and m are Positive integer greater than or equal to n, m
≧l) When controlling the manipulated variable so that the controlled variable is adjusted to its target value _YR = YR ₁ 〓 YRl, the control variable and the target value are adjusted. The difference YR−Y=YR ₁ −Y ₁ 〓 〓 YRl−Yl=ε ₁ 〓 εl is calculated in advance by a simulation evaluation of the behavior of the manipulated variable and the controlled variable when the target value is given. Element C ₁₁ …C ₁ l 〓 〓 Cn ₁ …Cnl is multiplied to calculate the manipulated variable U′c＝U′c ₁ 〓 Output obtained by performing integral operation on each of U′cn Uc＝Uc ₁ 〓 Ucn is used for each operation outputs UF = UF ₁ 〓 UFn obtained by performing a feedback operation on a plurality of measured quantities Y ₁ 〓 Ym including the controlled variable are applied to each of the manipulated variables, and are supplied to each of the manipulated variables, respectively. When the sum output of the output Uc - the output U _F exceeds a predetermined range,
A temperature control method for multiple furnaces, characterized in that each of the integral operations is stopped.