JPH0455740B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention generally relates to a temperature control device for a constant temperature device in physical and chemical equipment. (b) Prior Art A conventional method for controlling the temperature of this type of constant temperature device is disclosed in, for example, Japanese Patent Application Laid-open No. 35856/1983. This type of constant temperature device is required to precisely control the temperature inside the refrigerator to a target value of, for example, 15℃ to 30℃, which requires a heater to heat the inside of the constant temperature device and a compressor to cool it. It is equipped with a cooling device with a machine. Because this compressor cannot be stopped frequently due to its mechanism, for this kind of precise control it is common to control the heater output while the compressor is running, but the target value is If it is higher than , cooling will be required even though it is not necessary.
The output of the heater increases accordingly, requiring a large amount of power consumption. It is also possible to change the cooling capacity of the cooling system in stages by changing the resistance value of the pressure reducer in the refrigerant circuit of the cooling system, changing the number of poles of the compressor, or changing the frequency using an inverter. In any case, the current situation is that when the target value is high, the user has to manually stop the compressor or reduce the cooling capacity.

In order to save this time and effort, the above-mentioned publication uses proportional control of the heater, so that when the output of the heater, that is, the amount of operation in the proportional control calculation decreases, the compressor is driven, and when it increases, it is stopped, thereby automatically stopping the operation of the compressor. A method of controlling is adopted.

(C) Problems to be Solved by the Invention In the above-mentioned publication, the heater was proportionally controlled, but PI or PID control may be considered for more precise control. Here, PI control is proportional-integral control, and PID control further includes differential control. The general formula for PID control is shown below.

y=Kpe+Kp/Ti∫edt+KpTdde/dt...(i) Here, (y) is the manipulated variable that is the output of the heater, Kp is the proportional sensitivity, Ti is the integral time, Td is the differential time, and e is the target temperature (SV) and the temperature (PV) in the thermostat. In equation (i), Kpe is the specific manipulated variable, Kp/Ti∫edt is the integral manipulated variable, and KpTdde/dt is the differential manipulated variable. The proportional manipulated variable is proportional to the increase in the deviation e and acts to reduce it, the integral manipulated variable integrates the deviation and acts to eliminate steady deviations, and the differential manipulated variable acts to eliminate sudden temperature fluctuations. It acts in the direction of slowing down.

Figure 6 shows that as in the above publication, the manipulated variable (y), which is the output of the heater, decreases to, for example, 20% (y _L ) and drives the compressor, and from that state until it reaches 80% (y _H ). Temperature (PV) when the ambient temperature has increased from a stable state when the target temperature (SV) was higher than the ambient temperature.
shows the time course of As the ambient temperature rises, the manipulated variable (y), which is the heater output, gradually decreases.
When the manipulated variable (y) reaches (y _L ) at point f in the figure, the compressor starts. The manipulated variable (y) is very small, so the output of the heater is also small, and on the other hand, the temperature (PV) starts to drop rapidly when the compressor is started, so the manipulated variable (y) correspondingly decreases as well. In an attempt to return the temperature (PV) to the target temperature (SV), the temperature rises rapidly, causing
At the point, it reaches (y _H ). In other words, the compressor ends up being stopped even though the ambient temperature is high and cooling is necessary. Then, even though the compressor has stopped, the heater output is still above (y _H ), so overheating occurs and the temperature (PV) rises rapidly, causing h
After this point, the target temperature (SV) will be greatly overshot. Then, the manipulated variable (y) decreases rapidly again, and this cycle repeats, causing the temperature (PV) overshoot and undershoot to become large, resulting in a very unstable problem. It was hot.

The present invention aims to solve these problems.

(d) Means for Solving the Problems The present invention maintains the inside of the constant temperature device at a target temperature by respectively driving a heating means for heating the inside of the constant temperature device and a cooling means for cooling the inside of the constant temperature device in a temperature control device for a constant temperature device. It has a calculation unit that executes PI or PID calculation based on the temperature in the constant temperature device and the target temperature, and drives the heating means with the manipulated variable obtained thereby, and also operates as necessary. A control means for raising or lowering the cooling capacity of the cooling means is provided, and the control means is provided with means for setting a predetermined integral initial value in the calculation section when raising or lowering the cooling capacity of the cooling means.

(e) Effects According to the present invention, the cooling capacity of the cooling means is increased or decreased as necessary, so power consumption can be reduced. Further, by setting an appropriate initial integral value when the cooling capacity of the cooling means fluctuates, it is possible to prevent the temperature from becoming unstable.

(F) Embodiments Next, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a functional block diagram of a temperature control device 1 of the present invention. Reference numeral 2 designates a well-known microcomputer as a control means, and the microcomputer 2 has as its functions a PID calculation section 3, an integral operation amount storage section 4, integral initial value setting sections 5, 6, a comparison section 7, and a switch 8. . Reference numeral 9 denotes a temperature setting unit for setting a target temperature (SV) inside a constant temperature device (not shown), such as an incubator.
Output to PID calculation section 3. Reference numeral 10 denotes a temperature detection unit that outputs the internal temperature (PV) of the incubator to the PID calculation unit 3 via the A/D converter 11. 1
A heater 3 serves as a heating means for heating the inside of the refrigerator, and is connected to a heater drive circuit 14. or,
Reference numeral 15 denotes a compressor constituting a refrigerant circuit of a cooling device for cooling the inside of the refrigerator (not shown). The compressor 15 is connected to an AC power source 17 via a switch 16, and the heater drive circuit 14 is directly connected to an AC power source 17.

PID calculation unit 3 calculates temperature (PV) and target temperature (SV)
PID calculation is performed based on the above formula (i), and in particular, the integral operation amount (hereinafter referred to as ()).
is read into the storage unit 4 each time the calculation is completed, and a new integral manipulated variable ( ) is stored again. The manipulated variable (y) is calculated by adding the integral manipulated variable ( ) stored in the storage unit 4 to the other manipulated variables (proportional and differential), and outputs it to the heater drive circuit 14 . The heater drive circuit 14 controls the amount of heat generated by the heater 13 by adjusting the duty ratio of the energization time based on the operation amount (y).

The integral initial value setting units 5 and 6 each have predetermined integral initial values (I _OH ) (for example, +25%) and (I _OL ) (for example, −25%) stored in advance, and output these values. Each output is connected to the a contact and the b contact of the switch 8, and the common terminal of the switch 8 is connected to the storage section 4.

Based on the integral operation amount () stored in the storage section 4, the comparison section 7 switches switch 1 when the operation amount () decreases to a predetermined value (I _L ) (for example, -45%) or less.
6 to start the compressor 15, while switch 8
Operate to close contact a momentarily and set the initial integral value (I _OH )
is input into the storage unit 4, its contents are erased (I _OH )
Replace with Also, when the manipulated variable (I) increases to a predetermined value (I _H ) (for example, +45%) or more, switch 16 is opened to stop the compressor 15, while switch 8 is momentarily closed to contact b to restart the next operation. inputs the initial integral value (I _OL ) into the storage unit 4, erases its contents, and replaces it with (I _OL ). It is assumed that the switch 8 is not always closed at any of its contacts.

Next, FIG. 2 is a flowchart showing the software of the microcomputer 2. The process starts at the same time as the power is turned on, and in step 20 the target temperature (SV) and internal temperature (PV) are read from the temperature setting section 9 and temperature detection section 10, and in step 21 it is determined whether (PV) is higher than (SV). If the value is higher, the process proceeds to step 28, and if it is less than the value, the process proceeds to step 22. In step 22, the comparator 7 keeps the switch 16 open and the compressor 15 stopped, reads the temperature (PV) in step 23, and executes PID calculation in the PID calculation unit 3 in step 24. . Then, in step 25, the result (y) is output and the heater drive circuit 14 causes the heater 13 to generate heat. Next, in step 26, it is determined whether the integral operation amount (I) in the storage section 4 is less than or equal to (I _L ), and if not, the process returns to step 23, and if it is less than or equal to
Proceeding to step 7, the comparison section 7 closes the switch 8 to the a contact and writes the initial integral value (I _OH ) into the storage section 4. Next, in step 28, the switch 16 is closed and the compressor 1 is
5, read the temperature (PV) in step 29, execute PID calculation again in step 30, and use the operation amount (y) as the result to control the heater drive circuit 3.
1 controls the output of the heater 13. Next, in step 32, it is determined whether the integral operation amount (I) in the storage section 4 is greater than or equal to (I _H ), and if not, the process proceeds to step 2.
If the value is above, the process proceeds to step 33, closes the switch 8 to the b contact, writes the initial integral value (I _OL ) in the storage section 4, and returns to step 22.

Next, the operation of the temperature control device 1 of the present invention will be explained with reference to FIGS. 3 to 5, which show the time course of temperature (PV) in an actual control state. In Fig. 3, the target temperature (SV) is set to, for example, +30°C, and the proportional bands in the PID calculation unit 3 are set to the ranges of +31°C (PH) and +29°C (PL), respectively.
This shows the change in temperature (PV) over time when the power is turned on and control is started from an ambient temperature of +20°C. At this point, the temperature (PV) is lower than (SV), so the process proceeds from step 21 to step 22, and the compressor 15 is not started.
Also, since the temperature (PV) is below the proportional band, the output of the heater 13 at step 25 is
At 100%, the integral operation amount (I) is not calculated, and steps 23 to 26 are repeated to adjust the heater 13.
generates heat and rapidly increases the temperature (PV).
Eventually, it enters the proportional band at point j in Figure 3, and formula (i)
Calculation based on is started in step 24, and the integral manipulated variable (I) also increases. On the other hand, at point j, the temperature (PV) is rapidly rising, so the proportional and differential manipulated variables in equation (i) are increasing in the direction of decreasing the manipulated variable (y), and as a result, the output of the heater 13 is rapidly increasing. (because it is faster than the rate at which the integral manipulated variable (I) increases), and at point k in Figure 3, the manipulated variable (y) is lower than, for example, 20% (y _L ). ((y _H ) is 80%), but since the temperature (PV) is still lower than the target temperature (SV), the integral manipulated variable (I) is gradually increasing, so it will not become below (I _L ), Therefore, the compressor 15 is not driven in steps 26 to 27 and 28. After reaching the target temperature (SV) at point l in the figure, the integral manipulated variable (I) begins to decrease due to some overshoot, but the proportional and differential manipulated variables increase again, and eventually the temperature (PV) is stable as it matches (SV), and the manipulated variable
(y) and the integral manipulated variable (I) also converge to appropriate values. On the other hand, if the compressor 15 is driven when the manipulated variable (y) reaches (y _L ), the compressor 15 will start at point k in Fig. 3, and cooling is not necessary. Despite this, the control state becomes unstable due to cooling, but no unexpected problems occur in the temperature control circuit 1. This is because the integral manipulated variable (I) is determined by the integral value of the deviation, and therefore outputs the most stable value against temporary temperature (PV) changes. In other words, the integral manipulated variable (I) changes with changes in the ambient temperature and internal load conditions, and is output to eliminate steady-state deviations. The true need for cooling can be determined.

Next, in Figure 4, the temperature (PV) is the target temperature (SV).
This shows the control state when the ambient temperature rises from a stable state. At this time, the manipulated variable (y), which is the output of the heater 13, gradually decreases in an attempt to match the temperature (PV) with the target temperature (SV), and the integral manipulated variable (I) also decreases in order to eliminate the steady-state deviation. and go,
Eventually, the reduction in the output of the heater 13 is no longer sufficient, and when the integral operation amount (I) reaches (I _L ) at point _m in FIG. The amount (y) is forcibly raised and the compressor 15 is started in step 28. When the compressor 15 starts at point m and cooling starts, the temperature (PV) tries to drop rapidly, but the heater 13
Since the output of is increased by setting the initial integral value (I _OH ), a sudden drop in temperature (PV) can be suppressed. Thereafter, the output and integral operation amount (I) of the heater 13 rise slightly due to the temporary drop in temperature (PV), but eventually shift to a new stable state due to heating by the heater 13 and cooling of the compressor 15.

If the initial integral value (I _OH ) is not set here, the output of the heater 13 will have also decreased by the time the compressor 15 is started, so the temperature (PV) will drop rapidly, and the manipulated variable (y) (I ) increases and the compressor 15 is stopped even though cooling is required, making the control unstable, but the present invention does not have this problem.

Next, FIG. 5 shows a control state when the ambient temperature drops from a state where the compressor 15 is being driven and the temperature (PV) is stable at the target temperature (SV). At this time, the manipulated variable (y) and the integral manipulated variable (I) rise in the opposite way to the above, and eventually, when cooling is no longer necessary, the integral manipulated variable (I) reaches (I _H ) at point n in the figure. , proceed from steps 32 to 33 and set the initial integral value _IOL .
In step 22, the compressor 15 is stopped. When the compressor 15 stops at point n, the temperature (PV) tries to rise rapidly, but the output of the heater 13 is forced to decrease because the integral operation amount (I) has been lowered to (I _OL ). Because of this, a sudden rise in temperature (PV) is suppressed, and after that, PID of only heater 13
It moves to a stable state under control.

If the initial integral value (I _OL ) is not set here, the output of the heater 13 will have also increased when the compressor 15 stops, and the temperature (PV) will rise rapidly, so the manipulated variable (y) ( I) decreases and the compressor 15 is started even though cooling is not required, making the control unstable, but the present invention solves this problem.

It is assumed that the initial integral value (I _OH ) and the absolute value of I are smaller than the absolute values of (I _H ) and (I _L ), respectively.
In addition, in the embodiment, the compressor 15 was controlled by starting and stopping, but in addition, the cooling capacity of the cooling means may be increased in stages by, for example, changing the resistance value of the pressure reducer in the refrigerant circuit in stages. The present application is valid even if it is lowered or lowered.

(G) Effects of the Invention According to the present invention, power consumption can be reduced by increasing the cooling capacity only when cooling by the cooling means is necessary and stably controlling the temperature by PI or PID control of the heating means. In particular, since the integral operation amount of PI or PID calculation is set to a predetermined initial value as the cooling capacity increases or decreases, undershoot and overshoot due to excessive cooling and heating can be reduced, and a stable constant temperature device can be maintained. This allows temperature control.

[Brief explanation of the drawing]

1 to 5 show embodiments of the present invention, in which FIG. 1 is a functional block diagram of the temperature control device, FIG. 2 is a flowchart showing the software of the microcomputer, and FIGS. Figure 6 and Figure 5 are diagrams showing the time course of the temperature inside the thermostat;
This figure is a diagram showing the time course of temperature by a conventional control device corresponding to FIGS. 4 and 5. 1...Temperature control device, 2...Microcomputer, 3...PID calculation unit, 4...Storage unit, 5, 6
...Integral initial value setting section, 7...Comparison section, 13...
Heater, 15... Compressor.

Claims (1)

[Claims] 1 The inside of the constant temperature device is maintained at a target temperature by respectively driving heating means for heating the inside of the constant temperature device and cooling means for cooling the inside of the constant temperature device, and the PI is controlled based on the temperature inside the constant temperature device and the target temperature.
Alternatively, it has a calculation unit that executes a PID calculation, and a control unit that drives the heating means with the manipulated variable obtained thereby and increases or decreases the cooling capacity of the cooling means as necessary, and A temperature control device for a constant temperature device, characterized in that the control means includes means for setting predetermined integral initial values in the calculation section when increasing and decreasing the cooling capacity of the cooling means.