JP2713836B2 - Digital controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital controller for performing process control.

[0002]

2. Description of the Related Art FIG. 5 is a diagram showing the configuration of a conventional digital controller. In the figure, reference numeral 1 denotes an input unit, 2 denotes a control unit, 3 denotes an output unit, 4 denotes a display unit, 5 denotes a clock, 1
Reference numerals 1 and 12 denote a sensor failure detection function and an input switching function inside the input unit 1, respectively, and 41 and 42 denote a failure output display and a process value display displayed on the display unit 4, respectively. The details of the above components will be described in the following operation description.

Next, the operation will be described. This conventional digital control device includes an input unit 1 for taking in a measured value from an external sensor 10 for detecting information related to control of an object to be controlled, a control unit 2 operating to bring the measured value closer to a set value SV, and an external unit. An output unit 3 for outputting a control output amount from the control unit 2 to a control target, a display unit 4 indicating a control state to an operator, and an operation of the input unit 1, the control unit 2, the output unit 3, and the display unit 4 It consists of a clock 5 for performing synchronization. The basic function of a digital control device is to perform control in accordance with a measured value and output a control output. However, in a digital control device used in a system in which the process changes slowly, a sensor failure of the input unit 1 may occur. detection function 11, when the measured value by detecting the sudden change in the measured value is out of the predetermined range, and outputs a sensor malfunction signal, thereby previous instead of values input switching function 12 has input this time The value immediately before the occurrence of the failure sampled by the clock 5 is output, and an operation may be performed to avoid a sudden change in the control output. FIG. 6 is a flowchart of the above operation. As shown in FIG. 6, if there is no failure in the sensor 10 (step 61), the current measured value is used as an input (step 62). If there is a failure in the sensor 10 (step 61), the input of the sensor 10 The value immediately before the occurrence of the failure is used (step 63). The above sensor failure signal;
The signal switched by the input switching function 12 is displayed on the display unit 4 as a failure output display 41 and a process value display 42.

[0004]

In the conventional digital control device, even when the failure output display 41 is displayed, the sensor 10 has really failed because the process value display 42 appears to be a normal value. Noka sensor failure detection function 1
There was a problem that it could not be distinguished whether the failure was 1 itself. In addition, the behavior at the time of sensor failure detection is the same for any process (the input value is kept at the value immediately before the failure occurred), so the usage range is limited such that it cannot be applied to systems where the process changes rapidly. There was a disadvantage that it was done.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and has as its object to provide a digital control device which can distinguish between sensor failures and can be used in any process. And

[0006]

A digital control device according to the first aspect of the present invention has a function of holding a measured value input from the sensor 10 at a value immediately before the sensor failure occurs and a function of not retaining the input measured value when the sensor 10 fails. Function selector 6 for selecting
a.

In the digital control device according to the second aspect of the present invention, when the sensor 10 has a failure, a function selection function of selecting a function of holding the control output amount from the control unit 2 at a value immediately before the occurrence of the sensor failure and a function of not storing the control output amount. It has a portion 6a.

In the digital control device according to the third aspect of the present invention, the function selecting section 6a or 6b has an internal setting means or an external setting means for selecting a function.

A digital control device according to a fourth aspect of the present invention selects a function of holding the control output amount from the control unit 2 at a specific output holding value set from the outside when a failure occurs in the sensor 10, and a function of not holding the control output amount. It is provided with a function selecting section 6c to perform.

[0010]

According to the first aspect of the present invention, the function selecting section 6a selects a function of retaining a measured value input from the sensor 10 at a value immediately before the occurrence of a sensor failure and a function of not retaining the value when the sensor 10 fails.

According to the second aspect of the present invention, the function selecting section 6
“a” selects a function of holding a control output amount from the control unit 2 at a value immediately before the occurrence of a sensor failure and a function of not retaining the control output amount from the control unit 2 when a failure of the sensor 10 occurs.

According to the third aspect of the present invention, the function selecting section 6
In a, the function is selected by an internal setting unit, and the function selection unit 6b selects the function by an external setting unit.

According to the fourth aspect of the present invention, the function selecting section 6
“c” selects a function of holding a control output amount from the control unit 2 at a specific output holding value set from the outside when a failure occurs in the sensor 10 and a function of not holding the control output amount.

[0014]

[Embodiment 1] FIG. 1 is a configuration diagram of a digital control device according to a first embodiment of the present invention. In FIG. 1, reference numeral 1 denotes an input unit for inputting a measurement value from a sensor 10 for detecting information related to control of a control target, and 2 compares a measurement value input by the input unit 1 with a predetermined set value SV. a control unit for controlling so as to approach the measured value to the set value SV, 3 is an output unit for outputting to provide a control output amount from the control unit 2 to the control object, 4
Is a display unit for displaying a control state, 5 is a clock, 6a is an input measurement value from the sensor 10 when a failure occurs in the sensor 10 .
And a function selection unit for selecting a function of holding a control output amount from the control unit 2 at a value immediately before the occurrence of a sensor failure and a function of not holding the control output amount . The input unit 1 includes a sensor failure detection function 11 and an input switching function 12. Input switching function 12
Has switches 12a and 12b. The output unit 3 includes an output switching function 31 having switches 31a and 31b. The display unit 4 displays a failure output display 41, a process value display 42, and a control output amount display 43. The function selecting unit 6a includes a switch 71 interlocked with the switch 12a in the input switching function 12 of the input unit 1, and a switch 72 interlocked with the switch 31a in the output switching function 31 of the output unit 3.
And

Next, the operation will be described. Example 1
In the example, the function selecting section 6a has switches 71 and 72, and the operation is determined by the ON / OFF state of the switches 71 and 72. That is, the switch 71 is linked to the switch 12a of the input switching function 12, and the switch 72 is
1 is linked to the switch 31a, and the sensor failure detection function 1
1 determines the operation of the input switching function 12 and the output switching function 31 when a sudden change in the input signal is detected and the sensor failure signal is output. For example, when the switch 71 is ON , the switch 12a is ON , and the input measurement value at the time of the sensor failure is taken as the input measurement value immediately before the occurrence of the failure. Switch 71 is off
In this case, the switch 12a is turned off , and normal processing is performed even when the sensor fails. When the switch 72 is ON , the switch 31a is turned ON , and the output value (control output amount) at the time of the sensor failure is set as the output value immediately before the occurrence of the failure. Switch 7
When the switch 2 is OFF , the switch 31a is turned OFF , and normal processing is performed even when the sensor fails.

By the way, in order to shift the process to the safe side when an abnormality is detected in the furnace temperature control or the like in the plant to be controlled, the control is continued in accordance with the actual sensor abnormality state in the process where the output reduction is prioritized. In order to keep only the output value in a process where the change of the process is fast but the output does not suddenly change, such as the control of the injection of the raw material in the chemical reactor, the switch 71 is turned off. , Switch 72 to O
N, and when the process changes slowly, the switch 71 is turned on and the switch 72 is turned off.
Flexible to any process.

The input operation and the output operation in the first embodiment will be described with reference to the flowchart of FIG. If there is no sensor failure, the current measurement value is used as an input (test steps 21 and 22), and the output of the control unit 2 is used as an output (steps 23 and 24). If there is a sensor failure (step 21) and if there is an input holding function (step 25), the value immediately before the occurrence of the sensor failure is used as an input (step 26). If there is a sensor failure (step 23) and there is an output holding function (step 27), the value immediately before the occurrence of the sensor failure is used as the output (step 28).

The above-mentioned sensor failure signal and input switching function 1
2 and the signal after the switching of the output switching function 31
Are displayed as a failure output display 41, a process value display 42, and a control output amount display 43. If the switch 71 is not turned on, no inconvenience occurs on the display.

Embodiment 2 FIG. (Corresponding to claim 3) In the first embodiment, the function selecting section 6 is described as an example using a switch (setting means) built in the present apparatus. In this case, as shown in FIG. 3, if a set value is given to each control loop from a function selecting unit 6b provided outside the apparatus such as a CRT, the same control apparatus is used. More detailed control of each control loop can be performed.

Embodiment 3 FIG. (Corresponding to claim 4) In the first and second embodiments, when a sensor failure occurs, only the function of holding the control output value at the value immediately before the sensor failure occurs and the function of not holding the control output amount are selected. If setting is possible, as shown in FIG. 4, in response to an emergency shutdown or the like, a specific output holding value can be directly set from the function selection unit 6c when a failure occurs, and operation can be performed. The function selection unit 6c is provided for the control unit 2 when the sensor 10 fails.
And a function not to hold the control output amount from the controller at a specific output holding value set from the outside.

[0021]

As described above, according to the first aspect of the present invention,
When a sensor failure occurs, a function selection unit is provided to select the function that holds the input measurement value from the sensor at the value immediately before the sensor failure occurs and the function that does not hold it, so that the behavior of the input value at the time of the sensor failure becomes variable, The function can be selected depending on the target process, whereby it is possible to distinguish whether the sensor is faulty, and it is possible to flexibly cope with a system in which the process changes rapidly or any other process.

According to the second aspect of the present invention, the function selecting unit is provided for selecting the function of holding the control output amount from the control unit at the value immediately before the occurrence of the sensor failure and the function of not retaining the control output amount when the sensor fails. The behavior of the output value in the event of a sensor failure is variable, and the function can be selected depending on the target process, so that it is possible to distinguish whether the sensor has failed or not, and it is flexible for systems with fast process changes and any other processes. Is obtained.

According to the third aspect of the present invention, the function selecting section has an internal setting means or an external setting means for selecting a function, so that the function can be set according to the internal setting or the external setting. In particular, if a set value is given to the control loop from the outside, it is possible to obtain an effect that finer control can be performed.

According to the fourth aspect of the present invention, there is provided a function selecting section for selecting a function of holding a control output amount from the control section at a specific output holding value set from the outside when a sensor failure occurs and a function of not holding the control output amount. With this arrangement, a specific output holding value can be directly set from the outside when a failure occurs in response to an emergency shutoff or the like, and the effect of expanding the use range can be obtained.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a digital control device according to a first embodiment of the present invention.

FIG. 2 is a flowchart showing the operation of the first embodiment.

FIG. 3 is a configuration diagram of a digital control device according to a second embodiment of the present invention.

FIG. 4 is a configuration diagram of a digital control device according to a third embodiment of the present invention.

FIG. 5 is a configuration diagram of a conventional digital control device.

FIG. 6 is a flowchart showing the operation of the conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Input part 2 Control part 3 Output part 4 Display part 6a, 6b, 6c Function selection part 10 Sensor

Claims (4)

(57) [Claims] An input unit for inputting a measurement value from a sensor for detecting information relating to control of a control object, and a measurement value set by comparing the measurement value input by the input unit with a predetermined setting value A control unit that controls the sensor so as to approach the value, an output unit that outputs a control output amount from the control unit to the control object, and a display unit that displays a control state. A digital control device provided with a function selection unit for selecting a function of holding a measured value input from a sensor at a value immediately before the occurrence of a sensor failure and a function of not retaining the input measurement value when a failure occurs. 2. An input unit for inputting a measured value from a sensor for detecting information related to control of a control object, and a measured value set by comparing the measured value input by the input unit with a predetermined set value. A control unit that controls the sensor so as to approach the value, an output unit that outputs a control output amount from the control unit to the control object, and a display unit that displays a control state. A digital control device comprising a function selection unit for selecting a function of holding a control output amount from the control unit at a value immediately before the occurrence of a sensor failure and a function of not holding the control output amount when a failure occurs. 3. The digital control device according to claim 1, wherein the function selecting section has an internal setting means for selecting a function or an external setting means. . 4. An input section for inputting a measurement value from a sensor for detecting information relating to control of a control object, and setting the measurement value by comparing the measurement value input at the input section with a predetermined set value. In a digital control device including a control unit that controls the control value to approach the value, an output unit that outputs a control output amount from the control unit to the control target, and a display unit that displays a control state, a sensor failure A digital control device, comprising: a function selecting unit for selecting a function of holding a control output amount from the control unit at a specific output holding value set from the outside when the occurrence occurs, and a function of not holding the function.