JPS62157903A - Cooling method of pid control - Google Patents

Abstract

PURPOSE:To vary a duty ratio according to, for example, a polygonal curve for adapting an output rate to the cooling characteristic of a controlled system by obtaining a curve which is adapted to the cooling characteristic of the controlled system as a controlled variable characteristic for cooling among control variables corresponding to the output rate. CONSTITUTION:The deviation (e)(=TM-Tj) between a desired value TM of temperature and the measured value Tj of temperature of the controlled system 1 is calculated and a temperature control part 2 perform PID arithmetic operation to calculate the output rate (m). A microcomputer outputs two kinds of control signals S1 and S2 and a relay ON time pulse value P is found from a constant control period thetac (equivalent to a task period for PID arithmetic) and a relay output period thetaR which is the minimum width of the relay ON time according to the output rate (m) which is calculated from a PID arithmetic expression by the temperature control part 2. The P value (PH) of a heating side is determined according to a linear line when the output rate calculated by the microcomputer is between 0 and 100% and the P value (PC) of a cooling side, on the other hand, is determined according to a curve corresponding to the cooling characteristic of the controlled system 1 when the output rate is between -100 and 0%.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is a method for controlling PI of a controlled object having different heating characteristics and cooling characteristics.
This relates to a cooling method in D control.

(Prior Art) Conventionally, various methods have been proposed for performing good PID control with a small number of control parameters. In addition, temperature control using PID control is provided with not only a heating function but also a cooling function, and it is desirable to obtain good control characteristics with a small number of parameters even in this type of temperature control. It is rare.

(Problems to be Solved by the Invention) However, the time constants during heating and cooling generally differ depending on the heat retention state of the controlled object and the characteristics of the cooling refrigerant. In conventional PID control, for example, the operating time of the heating device and the cooling device (
(relay ON time) is controlled by duty. In other words, the duty is 1 when the output rate is 100%,
When the output rate is 0%, the duty is 0, and during that time, the duty ratio is determined by a linear relationship between both the cooling and heating characteristics, so in the system with the different cooling and heating characteristics described above, a good Plr) could not be controlled.

(Means for solving the problem) The present invention calculates an output rate according to a proportional term, an integral term, and a differential term regarding the deviation between a set target value and a measured value, and uses the output rate to determine the heating characteristics and cooling of a controlled object. , a method for controlling objects having different characteristics, in which the characteristics of the controlled amount for cooling among the controlled amounts corresponding to the output rate are made into a curve that matches the cooling characteristics of the controlled object.

(Function) The duty ratio of the control amount for controlling the heating device is changed in a linear relationship with the output rate obtained by PTI') calculation. On the other hand, in the output rate determined by PID calculation for the cooling device, the duty ratio is changed according to, for example, a polygonal curve that matches the cooling characteristics of the controlled object.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing a control system for PIF') control according to the present invention.

The target temperature value is TH1 The actual measured temperature value of controlled object 1 is T4
, the deviation e (=TH
TJ) is calculated, PTr) is calculated by the temperature controller 2, the output rate (m) is calculated according to the formula (A) below, and the controlled object 1 is automatically controlled according to the calculation result to maintain a constant target value T.
, and is maintained in the same way. The controlled object 1 has both a heating device and a cooling device.

However, kP: proportionality coefficient T,: integral time TD: differential time FIG. 2 shows an example of the control object 1, and shows a schematic diagram when the temperature of the plastic fluid 4 flowing inside the pipe body 3 is controlled. .

Heaters 5a are provided on the surface of the tube body 3 at appropriate intervals.

5b... are provided, and these heaters 5a, 5b... are connected to a heating relay 6 and an electric current tJ7, and this heating relay 6 is set to 0N10FF by a heating control signal S output from a microcomputer. Duty controlled. On the other hand, a cooling pipe 9 for passing a cooling medium 8 is attached to the pipe body 3 in a meandering coil shape, and the flow rate of this cooling pipe 9 is controlled by a cooling relay 1o made of electromagnetic pulp or the like. There is. This cooling relay 1
o is 0N10FF duty-controlled by a cooling control signal S2 output by the microcomputer. The temperature measurement of the tube body 3 is detected by, for example, a thermocouple 11 and inputted to the microcomputer.

FIG. 4 shows the hardware configuration of the microcomputer.

In the figure, various basic boards and a CPT 15 for screen display are connected around a CPU board 14. Each basic board has a keyboard 1 that provides operation commands, etc.
3 and the deviation (e), a memory board that stores the calculation results, and a digital input/output board 17 and an analog input/output board 18 that form an input/output interface. In this example, Since this is an example of temperature control, the temperature value measured by the thermocouple 11 is input to this analog input/output board 18, and the above-mentioned heating and cooling control signals St, Sz is output.

The two types of control signals S+ and St output from the microcomputer have a constant output rate according to the output rate calculated based on the PID calculation formula [formula (A) above] calculated by the temperature adjustment section 2. Control period θ.

(corresponds to the task cycle for PTD calculation) and relay O
From the relay output period θ8 which is the minimum width of N time, the following formula (
Calculate the relay ON time pulse value P using B), subtract (-1) from this P value every time the relay output period θ elapses, and keep the relay in the ON state until it reaches 0. Turn off the relay at this point.

UR100 When the output rate calculated by the microcomputer is between 0% and 100%, the P value (pH) on the heating side is a linear straight line α
(see Figure 3), while the output rate is 11
The P value (Pc) on the cooling side between 00% and 0% is determined according to a curve according to the cooling characteristics of the controlled object 1. For example, in FIG. 3, the cooling characteristics are exemplified by five types of curves, including a straight line β. indicates the conventionally used straight line, and the curve β
.

is particularly applied to those with a small cooling time constant, and the curve β2 is applied to those with a large cooling time constant. These curves β1
．． In addition to β2, for example, curve β3 shown in the drawing shows that the heating device is
If you want to control the cooling device to turn on at the same time when it is in the N state,
Curve β4 is a case in which the cooling device is desired to be turned off until a certain output rate is reached, and the number of bending points of these curves also indicates the need for rapid cooling in response to the cooling characteristics of the controlled object or in the event that an abnormality occurs in the plastic fluid 4. Changes may be made as appropriate depending on certain circumstances. Further, the curve is not limited to a polygonal line, but may be a quadratic curve such as a hyperbola. And these curves are′
They are stored in advance in the memory board 16 and can be selected as appropriate by operating the keyboard 13.

In addition, although the method of 0N10FF duty ratio control was illustrated in the above-mentioned embodiment, the method is not limited to this, and for example, the voltage value of the power supply 7 on the heating side may be controlled, or the flow rate of the cooling medium 8 may be directly controlled.

(Effects of the Invention) As described above, according to the present invention, good control characteristics can be obtained with a small number of control parameters in PID control when a heating function and a cooling function are provided. As a result, hunting and the like caused by differences in heating and cooling characteristics can be effectively prevented.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the control system of PIT) control according to the present invention, Fig. 2 is a schematic diagram showing the configuration of the heating system and cooling system, and Fig. 3 is a characteristic diagram showing the relationship between output rate and P value. , FIG. 4 is a block diagram showing the hardware configuration of the microcomputer. ■...Controlled object 2...Temperature control section 5a, 5b.
... Heater 6 ... Heating relay 10 ... Cooling relay Patent applicant Sekisui Chemical Co., Ltd. Representative Hiroshi 1) Kaoru Figure 1 Figure 2

Claims (1)

[Claims] 1) An output rate is calculated according to a proportional term, an integral term, and a differential term regarding the deviation between a set target value and a measured value, and the heating characteristics and cooling characteristics of the controlled object are controlled depending on the output rate. A cooling method in PID control, characterized in that among the controlled variables corresponding to the output rate, the characteristic of the controlled variable for cooling is made into a curve that matches the cooling characteristic of the controlled object. 2) A cooling method in PID control according to claim 1, wherein the controlled amount for cooling is regulated by a duty ratio in a control cycle at constant intervals. 3) The cooling method in PID control according to claim 1, wherein the curve is a polygonal line.