JPS592562Y2 - Redundant input signal source switching device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a switching device for redundant input signal sources.

In order to improve the reliability of boiler automatic control devices and the like, important input signal sources such as a main steam flow rate transmitter and a main steam pressure transmitter are duplicated.

Conventionally, when one of the duplicated input signal sources fails, switching is performed manually by an operator based on an alarm.

In this case, the alarm is generated by a mismatch in the signals of the duplicate signal sources, so when the operator encounters the alarm, he must first determine which signal source has failed before switching.

During this time, the control device is operated in manual mode.
Since it takes a certain amount of time to confirm the faulty side, manual operation must be continued for that long, which is not desirable in terms of maintaining control quality.

To automatically identify a faulty signal source, each signal system should be equipped with a means to monitor abnormal changes in the signal based on the differential value of the signal, and if the differential value becomes larger than the specified value, It is conceivable to determine that this is a failure and switch to the normal one.

However, when a failure is detected by this means, the abnormally suddenly changed signal has already been transmitted to the next stage, so the equipment at the next stage is seriously affected by the abnormal signal.

SUMMARY OF THE INVENTION An object of the present invention is to provide a device that can switch redundant input signal sources without passing abnormal sudden changes in the signal.

The present invention limits the rate of change of the input signal source on the active side and the input signal source on the standby side, which generate signals related to a common controlled quantity, to a constant value when the rate of change of each signal exceeds a predetermined limit. first and second speed-of-change limiters that each transmit to the next stage; first and second deviation monitors that detect the difference between the input and output signals of the first and second speed-of-change limiters, respectively; a changeover switch to which an output signal of the second speed-of-change limiter is applied and normally selects an input/output signal of the first speed-of-change limiter; The above object has been achieved by a redundant input signal source switching device comprising a switching controller for controlling switching of a switching switch.

The present invention will be explained below with reference to the drawings.

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

In FIG. 1, TA and TB are redundant input signal sources, where TA is on the active side and TB is on the standby side.

These generate signals relating to a common controlled variable.

RA and RB are change speed limiters, MA and MB are deviation monitors, TS is a changeover switch, C is a controller, and L is a changeover controller.

The rate-of-change limiters RA and RB are constituted by a circuit as shown in FIG. 3, for example.

In other words, comparator U and integrator ■ are complementary.
connected through a parallel circuit of transistors Ql and Q2,
The output signal Eo of the integrator (2) is negatively fed back to the comparator (U).

In this circuit, comparator U connects input signal Ei and integrator I
The transistor Q1 or Q2 is turned on depending on the magnitude relationship between the output signal Eo of
is input to integrator I.

The time constant of the integrator I is selected to a value that can follow the rate of change of the input signal Ei during normal operation.

In this circuit, while the input signal Ei is changing normally, the output signal Eo of the integrator (2) correctly follows the change in the input signal, so that an output signal Eo matching the input signal Ei can be obtained.

However, if the input signal Ei changes abnormally suddenly due to a failure of the signal source, the output signal Eo of the integrator (2) will no longer be able to follow it, and will change at a constant rate of change determined by its time constant.

Deviation monitors MA and MB are constituted by a circuit as shown in FIG. 4, for example.

The fourth circuit is a differential amplifier A that receives two input signals El and E.
2, and convert the difference signal into positive and negative reference voltages +Es,
- two comparators Ul, each given Es;
The signal is input to U2, and the output signals of the two comparators Ul and U2 are output as a command signal.

This circuit generates an off-level output signal while the difference between the two input signals El and E2 is within the range of positive and negative reference voltages Es and -Es, but when it exceeds that range, In response to this, comparator U1 or U2 generates an output signal of the on level.

The signal transmitted from the input signal source TA is passed through the rate of change limiter R.
A is applied to the A contact of the changeover switch TS through A.

The signal transmitted from the input signal source TB is passed through the rate of change limiter R.
B to the B contact of the changeover switch TS.

The changeover switch TS is normally turned on to the A side and supplies the signal from the input signal source TA to the controller C.

Deviation monitors MA and MB are change rate limiters RA, respectively.
The difference between the input and output signals of RB is monitored and a signal representing the result is provided to the switching controller.

The switching controller provides control signals corresponding to these signals to the switching switch TS and the controller C.

The set values of the rate of change limiters RA and RB are determined by the input signal source TA.
, is set slightly larger than the expected maximum rate of change of TB under normal conditions.

Such a value can be easily determined from the response characteristics of the process.

While the input signal sources TA and TB are operating normally, the rate of change of the signal transmitted from them is limited by the rate of change limiter RA.
, does not depend on the set value of RB, so the change rate limiter RA
, RB pass the respective applied signals as they are.

Therefore, the deviation monitors MA and MB, which respectively monitor the input and output signals of the change rate limiters RA and RB, do not detect deviations.

On the other hand, if the human input signal sources TA and TB fail, the signal transmitted from them suddenly changes to O or 100%, so this is applied to the set value of the change rate limiters RA and RB, and the change rate limiters RA and RB outputs the signal by limiting the rate of change to the set value.

Therefore, abnormal sudden changes in the input signal are not transmitted to the next stage.

Also, at this time, a difference occurs between the input signal and the output signal of the change rate limiters RA and RB, which causes the deviation monitors MA and M
Detected at B.

The switching controller switches the changeover switch TS and controls the controller C in accordance with the output signals of the deviation monitors MA and MB.

The detailed configuration of the switching controller is shown in FIG.

In Figure 2, the output of deviation monitor MA and the output of deviation monitor M
The negative value of the output of B is logically multiplied in an AND circuit 1, and the result is set in a latch relay 2 and given to the changeover switch TS as a switch changeover signal.

The output signal of the AND circuit 1 is given to the AND circuit 3 through a direct path and a delay/not path, and the output signal of the AND circuit 3 is given to the controller C as a hold command.

The output signals of the deviation monitors MA and MB are logically multiplied by an AND circuit 4, and are given to required parts of the control system as a manual control command.

The output signals of the deviation monitors MA and MB are also logically summed by the OR circuit 5 and outputted as an alarm signal.

Since the switching controller is as described above, the following operations are performed depending on the combination of failures of the input signal sources TA and TB.

(TA: Malfunction, TB: Normal) At this time, the output of deviation monitor MA is on, and the output of deviation monitor M is on.
Since the output of B is turned off, both of the two input signals of the AND circuit 1 are turned on, its output signal is turned on, the latch relay 2 is set, and a switch changeover signal is given to the changeover switch TS.

Therefore, the changeover switch TS is switched to the B contact side, and the normal input signal is selected and applied to the controller C.

When the output signal of the AND circuit 1 is turned on, the output signal of the AND circuit 3 is also turned on for a period corresponding to the delay time of the delay/negation path, and a hold command is given to the controller C.

As a result, the controller C temporarily enters the hold mode during the input signal switching, thereby preventing disturbance of the regulated output signal due to the input switching.

By turning on the output signal of deviation monitor MA,
An alarm signal is issued through the OR circuit 5.

Since both the output signals of the deviation monitors MA and MB are not on, the output signal of the AND circuit 4 is off.

[TA: Normal, TB: Failure] At this time, the output signal of deviation monitor MA is turned off and the output signal of deviation monitor MB is turned on, so the two input signals of AND circuit 1 are turned off, and its output signal is turned off. be.

Therefore, the changeover switch TS is not changed.

However, since the output signal of the deviation monitor MB is turned on, an alarm signal is generated through the OR circuit 5.

The output signal of the AND circuit 4 is off.

(TA: failure, TB: failure) At this time, the output signals of deviation monitors MA and MB are both turned on.

Since the output signal of the deviation monitor MB is given to the AND circuit 1 as a negative value, the output signal of the AND circuit 1 is off.

Therefore, the changeover switch TS is not changed.

However, since the output signals of both deviation monitors MA and MB are turned on, the output signal of the AND circuit 4 is turned on.
A manual control command is issued and an alarm signal is also output through the OR circuit.

In this way, the present invention provides a change rate limiter for each of the redundant signal sources, so it is possible to detect whether there is an abnormality in each signal based on the difference in the input and output of the change rate limiters. Even if the signal on the working side changes abnormally suddenly, the change is softened to a non-problematic level and transmitted to the next stage.

Therefore, the next-stage signal utilization device is less likely to be affected by the abnormal signal.

[Brief explanation of drawings]

FIG. 1 is a conceptual block diagram of an embodiment of the present invention, and FIGS. 2, 3, and 4 are detailed diagrams of a part thereof. TA, TB...Input signal source, RA, RB・
...Change speed limiter, MA, MB...
Deviation monitor, TS...changeover switch, C...
...Controller, L...Switching controller.

Claims (1)

[Scope of utility model registration request] When the speed of change of each signal exceeds a predetermined limit for the human input signal source on the active side and the input signal source on the standby side that generate signals related to a common controlled variable, the speed of change is limited to a constant value and the signal is sent to the next stage. first and second change speed limiters that transmit the change, first and second deviation monitors that detect the difference between input and output signals of the first and second change speed limiters, respectively; and said first and second change rate limiters. a changeover switch to which an output signal of the speed limiter is applied and normally selects a first variable speed limiter output signal; and a changeover switch of the changeover switch based on the output signals of the first and second deviation monitors. A switching device for a redundant input signal source, comprising a switching controller for controlling a redundant input signal source.