JP4729008B2 - Temperature control device - Google Patents

Description

  The present invention relates to a temperature control device for controlling a heating temperature in a heating furnace by a heater when the temperature in the heating furnace is changed by the heater.

  In the field of temperature control, two-degree-of-freedom PID control is widely used. Here, in the normal PID control (one-degree-of-freedom PID control), as described in Non-Patent Document 1, both the target value response and the disturbance response are controlled by the same adjustment unit. If the target value response is emphasized, the disturbance response is delayed, and if the disturbance response is emphasized, the target value response becomes oscillating (overshoot occurs). On the other hand, in the two-degree-of-freedom PID control, as described in Non-Patent Document 1, a disturbance response is handled by the PID unit, and a target value response is processed by the PID unit and feedforward. Thus, the disturbance response and the target value response can be handled independently.

  More specifically, in the two-degree-of-freedom PID control described in Non-Patent Document 1, the parameters of the PID part are adjusted for disturbance response, and the output from the PID part is suppressed by the output from the feedforward part. This prevents overshoot. Thereby, the target value response can be freely set without affecting the disturbance response by adjusting the parameter of the feedforward unit.

  Further, FIG. 9 of Non-Patent Document 1 describes the relationship between the parameters α and β of the feedforward unit and the overshoot temperature. From this relationship, α is about 0.65 and β is about 1.0. It can be seen that the overshoot temperature can be minimized.

OMRON TECHNICS Vol. No. 28 4 1988 p. 285-291 “Temperature control by 2-degree-of-freedom PID control system”

  Here, the output from the feedforward unit of Non-Patent Document 1 is obtained by applying a proportional action and a differential action to the target value. The output from the feedforward unit has a larger influence of the proportional action as the value of α is larger and the value of β is relatively smaller. As the value of α is smaller and the value of β is relatively larger, the differential action is increased. The impact will be significant.

  In addition, as temperature control by two-degree-of-freedom PID control, for example, in a glass substrate firing furnace (heating furnace) for a liquid crystal panel, by controlling the heating temperature of the firing furnace with a heater, the temperature of the firing furnace is kept constant. Control (ramp control) is generally performed in which the temperature is raised to a predetermined final target temperature at a predetermined final target time and held at the final target temperature. In such ramp control, in order to make the rate of temperature change constant, each of the target temperatures (hereinafter referred to as target temperature on the way) is determined for a plurality of times from the start of control until the target time elapses. And the heating temperature by the heater is controlled so that the temperature of the heating furnace becomes a corresponding intermediate target temperature at each time.

  Therefore, when the lamp control as described above is performed by the two-degree-of-freedom PID control, the target temperature is frequently changed as time passes, so that the value of α is large (for example, 0.65) and the value of β Is relatively small, the output from the feedforward unit has a small effect on the temporal change in the target temperature during the course (differentiation of the target temperature in the middle), that is, the followability to the change in the target temperature is low. Become. As a result, the temperature in the heating furnace reaches the corresponding intermediate target temperature with a delay from each time.

  On the contrary, if the value of α is small (for example, 0.1) and the value of β is relatively large, the output from the feedforward unit has a large influence on the time change of the target temperature on the way. Followability to the target temperature is improved. However, in this case, as can be seen from the description of FIG.

  The object of the present invention is to control the temperature of the heating furnace using the two-degree-of-freedom PID control, and the lamp control has high followability with respect to the target temperature on the way at each time and is over after reaching the final target temperature. It is to provide a temperature control device that does not cause a chute.

The temperature control apparatus of the present invention increases the temperature in the heating furnace to a predetermined final target temperature in a predetermined final target time by heating the inside of the heating furnace with a heater, and maintains the final target temperature. The change in temperature in the heating furnace until reaching the final target temperature is constant for a plurality of times from when control is started until the final target time elapses. A target temperature including a feed forward operation using a PID operation and a proportional element and a differential element is used to control the heating temperature by a heater so that a target temperature is set on the way and the heating furnace becomes the corresponding intermediate target temperature at each time. This is a temperature control device that performs value feed forward two-degree-of-freedom PID control. Then, from the final target temperature and the final target time, overshoot suppression temperature calculation means for calculating an overshoot suppression temperature that is proportional to the final target temperature and inversely proportional to the final target time, and the temperature of the heating furnace Temperature detecting means for detecting, determining means for determining the value of the coefficient α of the proportional element, and heating temperature control means for controlling the heating temperature by the heater by the target value feedforward two-degree-of-freedom PID control. ing. The determining means sets the value of α to a predetermined first value when the temperature in the heating furnace detected by the temperature detecting means is equal to or lower than a switching temperature lower than the final target temperature by the overshoot suppression temperature. When the temperature in the heating furnace detected by the temperature detection means is higher than the switching temperature, the value of α is determined to be a second value larger than the first value ( Claim 1).

  According to this, when the temperature of the heating furnace is equal to or lower than the final target temperature by an overshoot suppression temperature, the value of α is set to a predetermined first value, whereby the followability to the intermediate target temperature of the heating furnace is improved. Can be improved. Furthermore, when the temperature of the heating furnace becomes higher than the temperature lower than the final target temperature by the overshoot suppression temperature, the value of α is set to a second value that is larger than the first value. When the final target temperature is reached, overshoot is less likely to occur.

  In the temperature control device of the present invention, the overshoot suppression temperature calculation means calculates the overshoot suppression temperature so that the overshoot suppression temperature is a value proportional to the final target temperature and inversely proportional to the final target time. (Claim 2). According to this, by determining the overshoot suppression temperature in this way, the followability to the target temperature during the heating furnace is reliably increased, and overshoot is not easily generated after reaching the final target temperature. .

  Hereinafter, preferred embodiments of the present invention will be described.

FIG. 1 is a schematic configuration diagram of a temperature control system according to the present embodiment. As shown in FIG. 1, the temperature control system 1 includes a heating furnace 2 and a control device 3. In the temperature control system 1, it is input by the user, which is the final target temperature of the heating furnace 2 final target temperature n _x, and the last from the start of the control until it reaches the final target temperature n _x based on the target time t, the temperature is raised in the heating furnace 2 at a constant rate, and the final target time heating furnace 2 at t perform control such that the final target temperature n _x (ramp control).

More specifically, for each of a plurality of times t _{1 to} t ₄ (see FIG. 4) from the start of control until the final target time elapses so that the rate of temperature rise is constant. The intermediate target temperatures n _{1 to} n ₄ (see FIG. 4) are set, and the heating temperature is controlled by the heater 12 to be described later so as to become the corresponding intermediate target temperatures n _{1 to} n ₄ at the respective times t _{1 to} t ₄ . ing.

  The heating furnace 2 includes a heating chamber 11, a heater 12, a temperature sensor (temperature detection means) 13, a blower 14, a cooling fan 15, an exhaust valve 16, a shelf 17, and a partition wall 18. The heating chamber 11 is a space surrounded by an outer wall 19 made of a heat insulating material. The heater 12 heats the inside of the heating chamber 11. The temperature sensor 13 detects the temperature in the heating chamber 11 (in the heating furnace 2). The blower 14 circulates the air in the heating chamber 11 to make the temperature of the air in the heating chamber 11 uniform.

  The cooling fan 15 is provided in an air inlet 19 a formed in the vicinity of the lower right end portion of the outer wall 19 in FIG. 1, and air is introduced into the heating chamber 11 from the outside by operating the cooling fan 15. The exhaust valve 16 is provided in an exhaust port 19b formed in the vicinity of the lower left end portion in FIG. 1 of the outer wall 19, and rotates around a support portion 16a at the upper end. When the cooling fan 15 is not operating, the exhaust valve 16 closes the exhaust port 19b as shown by the solid line in FIG. When the cooling fan 15 is operated, the exhaust port 19b is opened by rotating the exhaust valve 16 about the support portion 16a as shown by a one-dot chain line in FIG. Thereby, outside air is introduced into the heating chamber 11 from the intake port 19a, and air in the heating chamber 11 is discharged to the outside, and the inside of the heating chamber 11 is cooled.

  The shelves 17 are arranged in the vertical direction in the drawing, and a sample P such as a glass substrate for a liquid crystal panel is disposed on each shelf 17. The partition wall 18 is disposed between the heater 12 and the shelf 17, and prevents the heat of the heater 12 from directly propagating to the sample P disposed on the shelf 17 to prevent the temperature of the sample P from rapidly rising. Yes.

  FIG. 2 is a block diagram of the control device 3 of FIG. As shown in FIG. 2, the control device 3 includes an overshoot suppression temperature calculation unit 21, an α determination unit 22, a heating temperature control unit 23, a cooling fan control unit 24, and a blower control unit 25.

Overshoot suppression temperature calculation unit 21 is inversely proportional to the final target time t as well as proportional to the final target temperature n _x entered by the user, calculating a predetermined overshoot suppression temperature n. Specifically, the overshoot suppression temperature n is calculated by calculating n = (n _x / t) · A. Here, A is a constant of about 1 <A <2.

The α determining unit 22 uses the overshoot suppression temperature n calculated by the overshoot suppression temperature calculation unit 21 and the temperature of the heating chamber 11 detected by the temperature sensor 13, so that the heating temperature control unit 23 has a two-degree-of-freedom PID described later. The value of α which is a parameter in the control is determined. More specifically, when the temperature in the heating chamber 11 is less than the final target temperature n lower by overshoot suppressing temperature n than _x switching temperature n _x -n is the minimum value in the range capable of setting a value of alpha (e.g., 0, determines a first value), determines the value of α when higher than the temperature n _x -n switching temperature of the heating chamber 11 to 0.65 (large second value than the first value) To do.

The heating temperature controller 23, based on the final target temperature n _x entered by the _user, the final target time t and the temperature in the heating chamber 11 detected in the temperature sensor 13, as described later, the heating chamber by the heater 12 11 heating temperature is controlled. Moreover, the cooling fan control part 24 controls operation | movement of the cooling fan 15 at the time of cooling the inside of the heating chamber 11, after heat processing is complete | finished. The blower control unit 25 controls the operation of the blower 14.

  FIG. 3 is a block diagram showing control by the heating temperature control unit 23 of FIG. As shown in FIG. 3, the heating temperature control unit 23, when represented by a block diagram, includes a PID unit 31, a feedforward unit 32, a subtractor 33, a proportional gain unit 34, an adder 35, a control target 36, and a subtractor. 37.

PID unit 31 includes a subtractor 37 is input from the difference between the value of the temperature in the heating chamber 11 detected by the final target temperature n _x value and the current temperature sensor 13, "1+ _[1 / T 1 s)] + T ₀ s ”is output. Here, T ₀ and T ₁ are parameters in the 2-degree-of-freedom PID control, and are set in advance. Further, s is a complex variable in Laplace transform.

The feedforward unit 32 outputs a value obtained by multiplying the value of the target temperature (intermediate target temperature n _{1 to} n ₄ , final target temperature n _x ) input by the user by “α + βT ₀ s”. That is, the output obtained by applying the proportional operation and the differential operation to the target temperature is output. Here, α and β are parameters in the two-degree-of-freedom PID control, and the value of α is determined by the α determination unit 22 according to the temperature in the heating chamber 11 detected by the temperature sensor 13 as described later. , Β are preset.

The subtractor 33 outputs the difference between the value output from the PID unit 31 and the value output from the feedforward unit 32 to the proportional gain unit 34. Proportional gain unit 34 outputs a value obtained by multiplying the K _p to the input value. Here, K _p is a parameter in the two-degree-of-freedom PID control, is set in advance.

  The adder 35 outputs the sum of the output value from the proportional gain unit 34 and the disturbance value σ to the control target. Note that the output from the adder 35 indicates the operation amount of the heating temperature by the heater 12.

  The control object 36 corresponds to the heater 12 and the temperature sensor 13 in FIG. 1 and is detected by the temperature sensor 13 when the heating temperature of the heater 12 is changed according to the value input from the adder 35. Output temperature. The temperature in the heating chamber 11 output from the control object 36 is output (feedback) to the subtractor 37.

Next, a method for controlling the temperature in the heating chamber 11 in the present embodiment will be described. FIG. 4 is a diagram showing a change in the midway target temperature in the temperature control system 1 shown in FIG. In the temperature control system 1, the temperature of the heating chamber 11, in order to change to the final target temperature n _x at a constant rate during the final target time t, as shown in FIG. 4, from the start of the control Intermediate target temperatures n _{1 to} n ₄ are set for a plurality of times t _{1 to} t ₄ until the final target time t elapses, and the target temperatures in FIG. 3 are changed as time passes. Specifically, as the target temperature of the FIG. 3, the time _{t 1} temperature _{n 1} until time _t 1 ~t between ₂ temperature _{n 2,} the time _t 2 during ~t ₃ temperature _{n 3,} time _{t 3} between ~t ₄ temperature _n 4, _{t 4} later inputs a temperature _{n x,} respectively. Thus, at each time _t 1 ~t _4, the temperature in the heating chamber 11, so that each the corresponding middle target temperature _n 1 ~n _4, the heating temperature by the heater 12 is controlled. In FIG. 4, the case where there are four intermediate target temperatures has been described as an example, but the number of intermediate target temperatures is not limited thereto.

FIG. 5 is a diagram showing a change over time of the temperature in the heating furnace 2 when the temperature in the heating furnace 2 is controlled in the temperature control system 1 shown in FIG. When fixed to 65, (b) indicates the case where the value of α is fixed to the minimum value (for example, 0.1), and (c) indicates the case of the present embodiment. In the following, as an example, the constant A is 1.37, 80 minutes the temperature in the heating chamber 11 by the lamp control (final target time t), where increased to 400 ° C. (final target temperature n _x) An example will be described. In this case, the overshoot suppression temperature n is
n = (400/80) · 1.37 = 6.85 (° C.)
Is calculated.

As described above, when the temperature in the heating chamber 11 is controlled by the two-degree-of-freedom PID control, if the value of α in the feedforward unit 32 is constant, the value of α is large (for example, about 0.65). When the value is relatively small, the output from the feedforward unit 32 is less influenced by the differentiation of the target temperature (time change of the target temperature), that is, the followability to the change of the target temperature is low. It becomes. As a result, as shown in FIG. 4, it may change frequently middle target temperature with the lapse of time, as shown in FIG. 5 (a), after the temperature in the heating chamber 11 has reached the final target temperature n _x In addition, overshooting in which the temperature further rises is unlikely to occur, but the followability to the intermediate target temperature at each time until the final target temperature _nx is reached (corresponding with a delay from each time t _{1 to} t _4). it reaches halfway to the target temperature _n 1 ~n ₄ to).

Conversely, when the value of α is small and the value of β is relatively large, the output from the feedforward unit 32 has a large influence on the time change of the target temperature. High trackability. As a result, as shown in FIG. 5 (b), trackability way at each time until it reaches the final target temperature n _x with respect to the target temperature n ₁ ~n ₄ is increased, and reached the final target temperature n _x Later, an overshoot in which the temperature rises further occurs.

In contrast, in the present embodiment, as shown in FIG. 5 (c), in the overshoot suppressing temperature n by low switching temperature n _x -n (above example than the temperature in the heating chamber 11 is the final target temperature 393.15 ° C.) or less, the value of α is set to a minimum value (for example, 0.1) within a settable range. Thereby, the followability with respect to the intermediate target temperatures n _{1 to} n ₄ at each time until the temperature in the heating chamber 11 reaches the switching temperature n _x -n (393.15 ° C. in the above example) increases. At this time, the temperature in the heating chamber 11 so does not reach the final target temperature n _x, it does not occur further overshoot temperature increases than the final target temperature n _x.

On the other hand, when the temperature in the heating chamber 11 becomes higher than the switching temperature n _x -n (393.15 ° C. in the above example), the value of α is switched to 0.65. Thus, after this, following capability is reduced relative to the final target temperature n _x of the temperature of the heating chamber 11, the temperature in the heating chamber 11 is further overshoot temperature rises when reaching the final target temperature n _x Hard to happen.

The temperature in the heating chamber 11, when a switching temperature n _x -n close to the final target temperature n _x than the temperature prior to heating by the heater 12, so that increasing the value of alpha, the After that, even if the followability of the temperature in the heating chamber 11 with respect to the intermediate target temperature at each time is low, the temperature in the heating chamber 11 greatly deviates from the intermediate target temperature until the final target temperature _nx is reached. There is no end to it.

According to the embodiment described above, the temperature of the heating chamber 11, when: only low switching temperature n _x -n overshoot suppressing temperature n than the final target temperature n _x, which can set the value of α range with minimum value in, the temperature of the heating chamber 11, with follow-up performance is lowered with respect to a change in the way the target temperature, when it becomes higher than the temperature n _x -n switching temperature of the heating chamber 11 is α by increasing the value, for follow-up property is low relative to the final target temperature n _x of the temperature of the heating chamber 11, after the heating chamber 11 has reached the final target temperature n _x, further overshoot temperature increases It becomes difficult to occur. Therefore, the temperature in the heating chamber 11 can be accurately controlled with respect to the final target temperature and intermediate target temperature of the lamp control.

Further, the overshoot suppressing temperature calculation section 21, as well as proportional to the final target temperature n _x, to a value that is inversely proportional to the final target time t, by calculating the overshoot suppression temperature n, of the heating chamber 11 The followability to the final target temperature and the intermediate target temperature in the ramp control of temperature can be reliably increased.

  Next, a modified example in which this embodiment is modified will be described.

In this embodiment, the overshoot suppressing temperature n, proportional to the final target temperature n _x, although the final target time was determined as a value that is inversely proportional to t, the method for determining the overshoot suppression temperature n in this Is not limited, and may be determined by another method according to the final target temperature _nx and the final target time t.

Further, in the present embodiment, when the temperature in the heating chamber 11 is equal to or lower than the switching temperature n _x −n, the value of α is set to the minimum value within a settable range, and the temperature in the heating chamber 11 is changed to the switching temperature n _x −. was determined to 0.65 the value of α when becomes higher than n, the value of α when higher than the temperature n _x -n switching temperature of the heating chamber 11 (second value) is heated greater than the temperature n _x -n following values of α when switching temperature in the furnace 2 (the first value), it may be the value of α to another value.

It is a schematic block diagram of the temperature control system which concerns on embodiment in this invention. It is a block diagram of the control apparatus of FIG. It is a block diagram which shows the control in the temperature control system of FIG. It is a figure which shows the change of the midway target temperature in the temperature control system of FIG. It is a figure which shows the result of having performed the temperature control of the heating chamber by the temperature control system of FIG. 1, When (a) fixes the value of (alpha) to 0.65, (b) made the value of (alpha) the minimum value. In the case, (c) shows the case of the present embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Temperature control system 2 Heating furnace 3 Control apparatus 11 Heating chamber 12 Heater 13 Temperature sensor 21 Overshoot suppression temperature calculation part 22 alpha determination part 23 Heating temperature control part

Claims (1)

By heating the inside of the heating furnace with a heater, the temperature in the heating furnace is increased to a predetermined final target temperature in a predetermined final target time, and when the temperature is held at the final target temperature, the control is started and the For each of a plurality of times until the final target time elapses, the target temperature is set halfway so that the change in temperature in the heating furnace until reaching the final target temperature is constant, Control of the heating temperature by the heater so that the heating furnace reaches the corresponding target temperature at the time, the target value feedforward type two-degree-of-freedom PID including the PID operation and the feedforward operation using the proportional element and the differential element A temperature control device controlled by control,
From the final target temperature and the final target time, an overshoot suppression temperature calculation means that calculates an overshoot suppression temperature that is proportional to the final target temperature and inversely proportional to the final target time ;
Temperature detecting means for detecting the temperature of the heating furnace;
Determining means for determining a value of the coefficient α of the proportional element ;
A heating temperature control means for controlling the heating temperature by the heater by the target value feedforward type two-degree-of-freedom PID control ,
The determining means includes
When the temperature in the heating furnace detected by the temperature detection means is equal to or lower than the switching temperature lower than the final target temperature by the overshoot suppression temperature, the value of α is determined to be a predetermined first value,
When the temperature in the heating furnace detected by the temperature detection means is higher than the switching temperature, the value of α is determined to be a second value larger than the first value. Control device.

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