JPS596401B2 - program control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a program control device in a process control system, and particularly to a device that controls the progress speed of a program according to the state of a controlled object.

For example, when controlling the temperature of a heating furnace, conventionally the temperature was raised or lowered by focusing only on the temperature at one representative point in the furnace. A temperature difference occurs, and when this temperature difference becomes significant, there is a drawback that it adversely affects the quality of the object to be processed.

The present invention manages differences in physical quantities at different measurement points within a controlled object, such as temperature differences between points in a furnace, so that they do not exceed allowable values without making any changes to the original programming device. The purpose is to provide a control device.

Next, an embodiment of the present invention will be described regarding temperature control of a heating furnace.

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

The furnace 1 is equipped with a heating burner 2, a main thermometer 3, and a sub-thermometer 4 for measuring the temperature inside the furnace.The measured value of the main thermometer is θ1, and the measured value of the sub-thermometer is θ2. shall be. Programs to be controlled are set in advance in the program device PRO. This program output E. is set as a reference value, and the measured value θ1 by the main thermometer 3 is set as a feedback value, and the fuel control valve 6 is controlled according to the deviation. A feature of the present invention is that a program progress speed reduction function, which will be described below, is added to the above-mentioned control system. That is, the difference between the absolute value of the difference between the measured values at two points, △θ■1θ1-θ21, obtained by the subtractor T, and the tolerance value △θ0 of the temperature difference △θ is obtained by the subtractor 8, and △θ<△θ0 In this case, the program proceeds at a predetermined standard temperature increase (or temperature decrease) rate, and when △θ>△θo, the program speed regulator R
By the function of C, the program progress speed is appropriately reduced according to the magnitude of the difference value (△θ−△θo), and therefore, △
It is controlled to maintain θ=Δθo. Fig. 2 shows a schematic characteristic diagram of the temperature rise in the furnace during the temperature rise process. In the figure, characteristic (B) indicates the temperature at point A where the time constant is small, and characteristic (B) indicates the temperature at point B where the time constant is large. There is a delay of time Ti from when point A reaches a certain temperature until point B reaches that temperature, and the temperature difference between the two points at a certain time is Δθ1. When slowing down the heating rate without changing the measurement points of the furnace structure, as shown in Figure 3, the delay time T2 from when point A reaches a certain temperature until point B reaches that temperature is determined by a time constant. Since it depends on the structure of the furnace, it is equal to the delay time T1 in FIG.
T1=T2 holds true, and therefore, the temperature difference Δθ2 between the two points becomes smaller than Δθ1 by the amount that the temperature increase rate is reduced.
The technical idea of the present invention can be implemented in various ways depending on the process control device, and some specific examples will be described next. FIG. 4 shows an embodiment using analog calculation.

In the figure, 9 is a multiplier, 10 is a Miller integrator,
The multiplicand Es of the multiplier 9 is a signal related to the standard rate of change set in the program, the multiplier ER of the multiplier 9 is an output signal of the program speed regulator RC, and △θ〈△θo
When EB=1 and △θ>△θo, as △θ increases, E? {It is determined that it will gradually decrease.
The input of Miller integrator 10, EI=ES-E blue, and the output of Miller integrator 10, E. is EO=-f'EIdt (where ττ is the time constant of the integrator). Therefore, when Δθ exceeds Δθo, ER<1, so the output EI of the multiplier 9 gradually decreases, and the signal E is introduced to the temperature controller TC.

The rate of change of τ decreases in proportion to 1·E1.

FIG. 5 shows a digital embodiment.

The first pulse generator PG-1 has a constant pulse rate corresponding to the tolerance value △θo゛, and the second pulse generator PG-2 has a pulse rate that changes corresponding to the temperature difference 1θ1-θ21, The larger the difference Δθ, the larger the pulse rate. The pulse motor PM rotates in the positive direction following the number of input pulses at the terminal U, rotates in the negative direction following the number of input pulses at the terminal D, and so on. When there is input to both terminals U and D, the motor rotates in the positive or negative direction according to the difference in the number of pulses. Contacts U and D are program setter P
Opening/closing is controlled by RO, and contact U is closed when a temperature increase instruction is issued, and contact D is closed when a temperature decrease instruction is issued. Both contacts A and A2 are connected to the output of the subtracter 8 (△θ−△θo
) is a positive contact, which is set in accordance with a memory element, such as a control relay, and is an a contact that operates in accordance with a control relay; contact A2 is closed when the temperature is instructed to rise, and contact a1 is closed when the temperature is instructed to be lowered.
The variable resistor RV has a voltage division ratio that changes according to the rotation angle of the pulse motor PM, and has a constant voltage E as an input and an output E. is introduced into the reference side input of the temperature controller TC. Now, in the temperature increase program, when △θ and △θo, only contact U is in contact, and pulse motor PM rotates in the forward direction at a predetermined speed to output E. is increased at the standard temperature increase rate, but when △θ>△θo, in addition to the above, contact A2 becomes a contact and the output pulse of the second pulse generator PG-2 is also introduced to terminal D, so the pulse motor PM The rotational speed of is reduced. In the temperature reduction program, Δθ△θ
o, only the contact D is in contact and the pulse motor PM rotates in the negative direction at a predetermined speed, but when △θ〉△θ0, the output pulse of the second pulse generator PG-2 is simultaneously transmitted through the contact a1. Pulse motor P is introduced into terminal U.
The negative direction rotational speed of M is reduced. The present invention is not limited to the above-mentioned heating furnace, but can be widely applied to devices in which the time delay phenomenon is noticeable6, such as devices related to heat, devices involving chemical changes, devices related to the growth of microorganisms, etc. .

The present invention is easy to implement because it can be implemented simply by controlling the rate of change of the set value without changing the original program.For example, in a ceramic firing furnace, temperature differences have a large effect on the quality of the product. Not only that, but also because it is difficult to provide a stirrer due to the high temperature, the effect of introducing the apparatus of the present invention is particularly remarkable.

[Brief explanation of the drawing]

FIG. 1 is a control system diagram of an embodiment of the present invention. FIGS. 2 and 3 are characteristic diagrams illustrating the operation of the above embodiment. FIGS. 4 and 5 are circuit diagrams showing specific embodiments of the features of the present invention. 1...Furnace, 2...
... Bar 9 3, 4 ... Thermometer, 6 ...
・Fuel control valve, RC...Program speed regulator, PRO...Program setting device, TC...
··Temperature Controller.

Claims (1)

[Claims] 1. A device for controlling a controlled object in accordance with a predetermined program, comprising means for detecting that a difference between measured values at at least two points regarding the controlled object exceeds a predetermined value, and a program progress speed reduction means, A program control device configured to equalize the state inside the controlled object by slowing down the progress of the program when the difference in measured values increases beyond a predetermined value.