JPS61101801A - Digital controller - Google Patents

Abstract

PURPOSE:To provide simply a backup function by allowing a diagnostic circuit to hold an output of a register and apply an output from a controller to a controlled system when the diagnostic circuit detects a fault in a digital control operating section comprising a setter, a comparator, the controller and a D/A converter. CONSTITUTION:While the diagnostic circuit 3 normally supervises the digital controller 1, when the circuit 3 detects a fault in the digital control operating section comprising the setter 5, the comparator 7, the controller 8 and the D/A converter 9, the circuit 3 stops immediately the revision of a register 13, which stores a value just before. The converter 9, the comparator 11 and the controller 12, however continue the operation, and a deviation between the value stored in the register 13 and an analog feedback signal is amplified to give an operation signal to the controlled system 4 via a switching contact 3b. Thus, a closed loop control is ensured in a loop of controled system 4 comparator 11 controller 12 changeover contact 36 controlled system 4 even when the controller 1 is failed and the control keeping the present state is attained even with the system 4 of a static type.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a digital control device with a backup function.

[Technical background of the invention and its problems] From the viewpoint of improving the reliability of control systems, multiplexing and redundancy of control devices have been conventionally performed.

In particular, when digitizing a control system, there are two main ways to increase reliability: multiplexing using the same hardware and backing up using analog hardware.

The former multiplexing method can make the system more reliable by increasing the degree of multiplexing, but it generally requires twice or more hardware.
This results in higher costs.

Therefore, in general, the latter "analog backup method" is preferred, and there are many systems that limit the range and function of backup so that operation equivalent to the status quo can be maintained continuously.

The simplest backup method is to maintain the current output of the D/A converter installed at the output section of the digital control device, but this is because the state of the controlled object is determined one-to-one according to the level of the manipulated output. This method is effective only for control objects that have an integral property, and requires some kind of adjustment function on the koto and backup sides for control objects that are non-locating and have integral properties. The conventional example will be explained below with reference to FIG.

As shown in FIG. 2, in the conventional device, a backup device 2 is provided separately from the digital control device 1, and when the diagnostic circuit 3 detects an abnormality in the digital control device 1, the output to the controlled object 4 is digitalized. The control device 1 is switched to the backup device 2.

At this time, the digital control device 1 includes a setting device 5, an A/D converter 6, a comparator 7, a controller 8, and a D/A converter 9, and converts the analog signal fed back from the controlled object 4 into an A/D converter. The D converter 6 converts the signal into a digital signal, the comparator 7 compares it with the setting value from the setting device 5, and the controller 8 calculates the operation signal so that the deviation is 0. converts it into an analog signal and outputs it to the controlled object 4.

On the other hand, the backup device 2 includes a tracking/memory device 10, a comparator 11 . It is equipped with an analog controller 12, and when the digital control device 1 is normal, the analog feedback signal from the controlled object 4 is tracked and stored in the tracking/storage device 10. When an abnormality occurs in the digital control device 1, the tracking operation of the tracking/memory device 10 is stopped based on an instruction from the diagnostic circuit 3. Therefore, from now on, the backup device 2 compares the output of the tracking/memory device 10 and the analog feedback signal from the controlled object 4 using the comparator 11, converts the deviation into an operation signal using the analog controller 12, and converts the deviation into an operation signal to the controlled object 4. Output to.

As a result, after a failure occurs in the digital control device 1, the output of the backup device 2 is used to control the controlled object 4.
The control state of the digital control device 1 can be maintained at the state immediately before it went down.

In this way, a digital control device having a backup function that is effective even for non-local control objects can be obtained, but as can be seen by comparing the digital control device 1 and the backup device 2 in FIG. In this case, the amount of hardware of the backup device 2 is almost the same as that of the digital chill control device 1, and there is a problem that the advantages of the analog backup system, such as simplicity and ease, are lost.

[Object of the Invention] The present invention solves the above-mentioned problems and provides a digital control device that is inexpensive, simple, and equipped with a backup function that is highly reliable and can be applied to non-local control objects. purpose.

[Summary of the Invention] Therefore, the present invention provides an A/D converter that converts an analog signal fed back from a controlled object into a digital signal, a register that stores and holds the digital signal, and a register that converts the digital signal into an analog signal. A comparator that calculates the deviation between the analog signal and the analog feedback signal, and a controller that controls the register so as to eliminate the deviation. The present invention is characterized in that, while the output of the register is adjusted, when the digital control arithmetic unit becomes abnormal, the output of the register is held and the output from the controller is added to the controlled object.

Embodiment of the Invention FIG. 1 shows a configuration diagram of a digital control device according to an embodiment of the invention. In the figure, the same reference numerals as in Fig. 2 indicate the same or corresponding parts, and the difference from Fig. 2 is that the A/D
The converter 6 includes a register 13 that stores and holds a digital signal corresponding to an analog feedback signal from the controlled object 4, a D/A converter 9 that converts the digital signal into an analog signal, and a D/A converter 9 that converts the digital signal into an analog signal. Output and controlled object 4
It consists of a comparator 11 that calculates the deviation from the output of Controller 1 when device 1 fails
2 is outputted to the controlled object 4.

With the above configuration, when the digital control device 1 is normal, the A/D
The converter 6 converts the digital signal of the internal register 13 into D
/A converter 9 converts it into an analog signal.

The comparator 11 compares this with the analog signal fed back from the controlled object 4, and the controller 12 controls the register 13 so that the deviation is O. As a result, the digital signal in the register 13 comes to match the analog feedback signal, and the ^/D conversion is completed. After the digital signal after A/D conversion is compared with the command value from the setting section 5 in the comparator 7, the control section 8 performs control from the D/A converter 9 via the contact 3a in order to eliminate this deviation. Output an operation signal to target 4.

On the other hand, the diagnostic circuit 3 constantly monitors the digital control device 1 and controls the setting device 5, comparator 7, controller 8, and D/A converter 9.
As soon as an abnormality is detected in the digital control calculation unit consisting of the register 13, updating of the register 13 is stopped and the previous value is held. However, the D/A converter 9, comparator 11 . The controller 12 continues to operate, amplifies the deviation between the stored value of the register 3 and the analog feedback signal, and sends an operation signal to the controlled object 4 via the switching contact 3b.

At this time, the switching contact 3a is turned off by a signal from the diagnostic circuit 3.

Therefore, even in the case of an abnormality in the digital control device 1, the control object 4→comparator 11→controller 12→switching contact 3b
→ Closed loop control with the controlled object 4 is ensured, and even if the controlled object 4 is non-locating, control can be maintained while maintaining the current state.

Note that the A/D converter 6 in the above embodiment has a comparator 11.
Even with a follow-up type A/D converter that increases or decreases the value of register 3 by 1 in response to the deviation output of comparator 11, the value of register 3 increases or decreases by 1/2 in response to the deviation output of comparator 11, that is,
Register 3 is a successive approximation type A/A that sequentially converts from the most significant digit to the least significant digit and sets the digital conversion value.
Any D converter may be used.

In addition, after failure detection and switching operation, the current status is maintained.
).

I added an explanation, but for register 3, manual increase/
It is also possible to send a command to decrease and deflect the driving point.

Of course it is possible.

[Effects of the Invention] As explained above, according to the present invention, a high reliability system having an inexpensive and simple backup function that can be applied to an indefinite control target without adding a special external backup device can be achieved. A digital control device is obtained.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a digital control device according to an embodiment of the present invention, and FIG. 2 is a block diagram of a conventional digital control device and its backup device. ■... Digital control device, 2... Backup device, 3... Diagnostic circuit, 4... Controlled object, 5... Setting device, 6... A/D converter, 7, 11...・Comparator,
8...Controller, 9...D/A converter, 10...Tracking/memory device, 12...Controller, 13...Register. Figure 1, 1

Claims (1)

[Claims] An A/D converter that converts an analog feedback signal from a controlled object into a digital signal, and an A/D converter that compares the output of this A/D converter with a set value and converts the operation signal into an analog signal to eliminate the deviation. In a digital control device that includes a digital control calculation unit that outputs to a controlled object, the A/D converter is configured to include a register that stores and holds the digital signal, and a D/A converter that converts the output of the register into an analog signal. a comparator that calculates the deviation between the D/A converter output and the analog feedback signal, and a controller that controls the register so as to eliminate the deviation based on the comparator output. In addition, the output of the register is added to the digital control calculation unit, and the digital control calculation unit adds the output to the controlled object when it is normal, and adds the output of the controller to the controlled object when it is abnormal. A digital control device characterized in that it is configured as follows.