JPS6319841Y2 - - Google Patents

Description

[Detailed description of the invention] This invention is based on an automatic adjustment/manual adjustment switching circuit (hereinafter referred to as an automatic/manual switching circuit) for electronic controllers mainly used to control continuous processes, especially analog controllers that perform PID calculations using analog calculations. ).

Generally, this type of electronic controller uses a soft manual circuit consisting of a capacitor, a resistor, and an operational amplifier as an output device during manual operation, but this soft manual circuit alone is not sufficient. If the manual operation continues for a long time, the charge in the capacitor will gradually discharge and the manual operation output will decrease. . (In general, a manual operation method that uses only the soft manual circuit is called soft manual.) Therefore, when using manual operation and leaving it unused for a long time, manually switch the terminal voltage of the capacitor to a constant voltage power source such as a battery, and then A method is used to make the output equal to the output from a constant voltage power supply.
(Generally, this manual operation method that uses a constant voltage is called hard manual).

However, when using the hard manual method,
When switching from automatic to manual, if you do not balance the previous automatic output and the previous hard manual residual voltage in advance, a bump will occur during the switching, which will cause unnecessary disturbance to the process. It will give a cause. Furthermore, depending on the length of manual driving time, manually switching between the soft manual and hard manual at the driver's discretion places an excessive burden on the driver, and the automatic
This becomes an obstacle to smooth manual switching.

As a means to eliminate this obstacle to automatic-manual switching, a servo mechanism may be provided so that the manual output always follows the automatic output, or a counter and D/A converter may be combined as a static tracking circuit. Various methods have been proposed, such as providing a tracking type switching circuit, but although these circuits are extremely effective for performing automatic-manual switching without bumps, they require complicated mechanisms or circuits. Moreover, it is inevitable that reliability will deteriorate.

Particularly recently, as this type of automatic control equipment is used for long-term non-stop operation of plants with small time constants, the automatic-manual switching required for maintenance inspection and troubleshooting of the automatic control equipment is becoming increasingly difficult. It is desired that the plant not be affected by bumps, etc. In this case, the soft manual system is ideal to prevent bumps from occurring, but if the period of manual operation becomes long, the soft manual circuit The influence of the time constant can no longer be ignored. (If the manual operation period is long, the hard manual method is advantageous).

In consideration of the above, this invention is based on the soft manual method, in which the counter starts counting only after a preset period of time has elapsed, and according to the output,
The output of the D/A converter is changed, and when the value reaches the manual output of the software method, the manual output of the hard memory is output. This allows the manual period to be shortened. Our aim is to provide a controller that is simple in structure and convenient to handle, which takes advantage of the advantages of the soft manual system and automatically switches to the hard manual system after a certain period of time has elapsed from the manual period. .

That is, the present invention provides a timer circuit in addition to a soft manual type manual circuit without using a complicated and expensive circuit such as a tracking circuit, and when the period after manual switching exceeds the fixed time limit of the timer,
The counter automatically starts counting pulses, and the output of the D/A converter is changed according to the output. In this way, the output of the D/A converter gradually increases from zero until it reaches the same value as the manual output of the soft manual.
When the A converter output and the soft manual manual output are balanced, the hard memory corresponding to the D/A converter output is output. This hard memory is INC (increase) or DFC (decrease) when switching from manual to automatic or while in manual mode.
When the switch is operated, it is released, so there is no problem with these three types of driving operations.

Next, an embodiment of the present invention will be described. FIG. 1 is a circuit diagram showing the configuration of an embodiment of the present invention;
The figure is a circuit diagram showing the configuration of an analog controller of the present invention equipped with an automatic-manual switching circuit. In Figure 1, 1 is automatic-manual (automatic)
The first contact of the (A/M) changeover switch (hereinafter referred to as A/M changeover switch), 2 is the capacitor for the soft manual, 3 is the second contact of the A/M changeover switch, and 3' is the A/M changeover switch. 3rd contact, 4 is DC constant voltage power supply for hard manual (terminal voltage
E ₂ ), 4' is the reference DC constant voltage power supply (terminal voltage E ₁ ) for 4, 5 is the resistor (resistance value R), 6 is the capacitor (capacitance C ₂ ) (terminal voltage E ₃ ), 7 is the gate ,
8 is a binary counter, 9 is a reset input for 8,
10 is a D/A converter (digital-to-analog converter), 11 is an output voltage ed of the D/A converter 10, 12 is a manual output voltage eo, 13 is a comparator between voltage ed and voltage eo, and 14 is an electromagnetic relay ( 15 is the 1st a contact of the relay, 16 is the 2nd a contact and b contact of the relay (solid line: automatic operation, dotted line: manual operation) 17 is a push button switch for manual output increase (INC) 1st a contact, 18 is pushbutton switch b contact for manual output INC, 19 is pushbutton switch 2nd a contact for manual output INC, 20 is manual output decrease (DEC)
21 is the pushbutton switch B contact for manual output DEC,
22 is the 2nd a contact of a pushbutton switch for manual output DEC, 23 is a pulse input to the binary counter 8, 24 is a hard memory, 25 is a resistor that determines the time constant of the soft manual voltage eo,
26 is the automatic output of the automatic control device, 27 is the output when the automatic control device is switched manually (26, 2 when automatic)
7 matches). In FIG. 2, 28 is a process signal, 29 is a differentiation circuit, 30 is a gain and integration circuit, 31 is a soft manual circuit, and 32 is a hard manual circuit.

The analog calculation by the differentiator circuit 29 and the gain and integration circuit 30 is called PID calculation.

Next, the operation of the present invention will be explained with respect to the circuits shown in FIGS. 1 and 2. Regarding the switch states in FIG. 1, the solid line indicates automatic operation, and the dotted line indicates manual operation. From the solid line state, turn A/M selector switch 1,
3 and 3' to the manual position shown by the dotted line, the first contact 1 of the A/M changeover switch outputs the automatic output 26 of the automatic control device shown in Fig. 2 (which becomes the input to the manual circuit shown in Fig. 1). is cut out, but capacitor 2 has
The automatic output signal value 26 before switching is maintained as it is. At the same time, the third contact 3' of the A/M changeover switch becomes open, and the terminal voltage _E2 of the hard manual power supply 4 is charged to the capacitor 6 via the resistor. In this case, for example, if the time constant of the capacitor 6 and the resistor R is set to one hour, the terminal voltage E ₃ of the capacitor 6 will be about 63.2% of the terminal voltage E ₂ of the power supply 4. When this E ₃ becomes greater than the terminal voltage E ₁ of the comparison power source 4', the gate 7 opens and the pulse input 23 is applied to the UP side of the binary counter 8. Since this counter output is reset to zero by the reset input 9 in the automatic state, the binary counter 8 is reset to zero by the reset input 9.
When opened, integration is performed gradually from zero, and its binary output is converted by the D/A converter 10 into an analog voltage 11 (its value is ed). When this ed is larger than the soft manual voltage 12 (its value is eo), the output of the comparator 13 (A4) of ed and eo becomes positive, the relay coil 14 is energized, and the 1A contact 15 of the relay is closed. , the second a contact 16 is also switched to the hard memory (H side) shown by the dotted line. That is, at this point, manual output 27 is held at a value equal to the output of converter 10. In the hard memory state, gate 7 is closed and binary counter 8
The value of does not change.

Next, when either the INC or DEC pushbutton switch is pressed, either contact 18 or 21 opens, releasing the hold 15 of the relay, and relay contact 1
6 returns to position A. Also, the capacitor 6 is short-circuited by the contact 19 or 22 of the pushbutton switch, and its charge is discharged, so that the terminal voltage of the capacitor 6 gradually increases from zero again.
As mentioned above, when E ₃ >E ₁ , the hard memory 24 is switched again. Also hard memory 24
A/M selector switch 1, 3, 3' during manual operation.
When set to the automatic A side, the hold of the relay is released by the switch 3, the relay contact 16 is switched to the automatic A side, and the same automatic output as in the case of the hard memory 24 is output. In this case, the binary counter 8 is reset to zero and the capacitor 6 (C ₂ ) is shorted, so
In this case, the hard manual output voltage 12 (its value
eo) becomes larger than the output voltage 11 of the D/A converter (its value ed), the comparator 13 does not operate,
The relay is not energized.

As described above, when automatic operation is switched to manual operation, the timer circuit consisting of constant voltage power supplies 4, 4', capacitor 6, resistor 5, operational amplifier A5, etc. starts operating, and when the time limit determined by capacitor 6 and resistor 5 elapses, Since the pulse gate 7 is opened and the pulse counter 8, which has been reset to zero in advance, starts counting, the output of the D/A converter 10 also gradually increases from zero until it reaches the soft manual voltage 12.
(eo). At that time, the comparator 13 operates and the relay coil 14 is energized, so the changeover switch 16 is operated and the output is switched to hard manual output. That is, until this switching, it is a soft manual, and after the switching, it becomes a hard manual. Moreover, the switching is completely automatic.

In the above embodiment, the A/M changeover switch 1,
3, 3' DEC push button switch 17, 18, 1
9, Push button switch for INC 20, 21, 21,
Although we have shown an example in which electromagnetic relays 14, 15, and 16 are all in contact, it is also possible to form these switches and relays into logic circuits using static circuits, and as a result, it is possible to A gate circuit that resets the timer circuit during DEC operation or automatic switching, and interrupts input to the counter in hard memory;
If it is equipped with a circuit that holds this, a circuit that releases this hold when switched to INC, DEC, and automatic, a circuit that automatically resets the counter, and a circuit that combines a counter D/A converter, All of them can produce similar effects.

As detailed above, the present invention takes advantage of the advantages of the soft manual, and the human operation is
By simply switching between automatic and manual positions, it is possible to prevent a decrease in output due to soft manual leaks, and it is now possible to perform completely balance-less automatic/manual switching. In the conventional system using a hard manual, the output signal was generated by a potentiometer, but this system basically consists of a D/A converter, counter, comparator, timer, etc., so reliability is low. It also improves.

It also requires fewer components and is less expensive than a circuit that constantly tracks.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing the structure of an embodiment of the present invention, and FIG. 2 is a circuit diagram showing the structure of a process controller equipped with an automatic-manual switching circuit. Explanation of symbols: 4: DC voltage power supply, 4': Reference DC voltage power supply, 5: Resistor, 6: Capacitor, 7: Gate circuit, 8: Binary counter, 9: Reset input, 10: D/A converter, 13 : Voltage comparator,
14: Relay coil, 26: Automatic output of automatic control device, 27: Manual output during manual switching, 28: Process signal, 31: Soft manual circuit, 32: Hard manual circuit.

Claims (1)

[Scope of utility model registration request] In an analog controller that has an automatic-manual changeover switch and performs PID calculations using analog calculations, there is a soft manual circuit that operates in response to the switch to manual mode, and a soft manual circuit that operates upon switching to manual mode and the end of the soft manual circuit's output increase/decrease operation. A timer circuit that operates and resets by switching to automatic and increasing/decreasing the output of the soft manual circuit, a hard manual circuit, a switch from soft manual to hard manual, and an output of the hard manual circuit and an output of the soft manual circuit. The hard manual circuit includes a comparator for comparison, and the hard manual circuit includes a counter that starts counting after a certain period of time set by the timer circuit, and a D/A converter that converts the output of the counter into an analog value. An analog controller characterized in that when the output of the hard manual circuit exceeds the output of the soft manual circuit, the switching switch is actuated by the output of the comparator to switch from the soft manual to the hard manual.