JPS6275705A - Digital controller - Google Patents

Abstract

PURPOSE:To cause each sequence to make independent operation confirming tests, by artificially making the output signals of optional one sequence of logical operation circuits to be tested to the output signal of a 2/3 logic circuit. CONSTITUTION:If all signals 51a-51c are 'OFF', values of the output signals 41a-41c of a selected logic circuit 4 respectively coincide with values of signals 11a-11c. Moreover, when the signal 51a is 'ON' and the other signals 51b and 51c are 'OFF', the value of the signal 41a is equal to the value of the signal 11a and the value of the signal 41b becomes 'ON' regardless of the value of the signal 11b, and then, the value of the signal 41c becomes 'OFF' regardless of the value of the signal 11c, when the test of a logical operation circuit 1a is executed. Therefore, the output signal of a 2/3-logic circuit 2 becomes equal to the output signal 41a, namely, the value of the output signal 11a of the logical operation circuit 1a. The very same phenomena are obtained when logical operation circuits 1b and 1c are tested. Therefore, the operation confirmation of an optional one sequence can easily be tested without receiving any influences from the output signals of the other two sequences, since the sequence to be tested is independently connected with a mimic device for testing.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an improved technique for a multiplexed digital control device having three series of the same logic operation circuit.

[Technical background of the invention and its problems]

Multiplexed control devices are often used in large-scale systems that require high reliability, such as power plants. In particular, in digital control equipment that handles binary signals such as on and off, logic operation circuits are tripled, and % of the output signal of each series is
It is often configured to take logic and output signals to the controlled object.

In such devices, it is necessary to carefully check the operation of the logical operation circuits before combining them with actual equipment. To do this, a simulation device that resembles the characteristics of the actual system is prepared and used. There is a way to check the operation in advance. In particular, the larger the scale of the process and the more complex the logical operations performed by the control device, the greater the need for such simulation tests.

FIG. 3 shows an example of a general configuration for a stain resistance test in such a multiplexed digital control device. In FIG. 3, logic operation circuits 1a and lb.

1c each performs exactly the same logical operation and is triplexed. Output signal 11 of each logic operation circuit
a, llb, llc are input to the 2/3 logic circuit 2, and as a result, the output signal 2 is determined by majority decision of the three input signals.
Get 1. The final output signal 21 of the control device is inputted to the simulator 3 to indicate the operation of the actual process to be controlled, and the output of the process simulator is determined accordingly. .

The feedback signal 31 to 1c constitutes a closed loop system as a whole.

By the way, when carrying out such a test to check the operation of a logic operation circuit, since all three series of logic operation circuits perform exactly the same logic operation, it is necessary to check the operation of any one of them.
It is sufficient to confirm the operation of the series. However, in the configuration shown in Figure 3, the output signals of each series are connected to the process simulator via the 2/3 logic circuit 2, so the final output signal is automatically determined by the % logic, and the output signal of each series is automatically determined by the % logic. However, it is not possible to directly input one series of output signals to the process simulator. Therefore, while testing any one series, if it is possible to make the output signal of the seventh series the output signal of the 2/3 logic circuit, the output signal of the other two series will not be interfered with. Since it is possible to check the function of each series alone, it becomes easy to test three series at the same time.

For example, if a logic operation circuit is implemented using computer software, there will be a time lag in the output signals of each series unless synchronization is achieved with the execution synchronization of each computer. This makes testing of three trains at the same time even more difficult. Normally, the multiplexed streams are not synchronized as described above in order to maintain their mutual independence.

In addition, if you turn off the power supplies of the logic operation circuits of the other two series in order to make use of only the l series, the logic outputs of those two series will both be turned off or on, so the output of the 2/3 logic circuit will always be off. Otherwise, the specified purpose cannot be achieved.

Also, if you think about it simply, if you can test the logic operation circuit alone in combination with a plant simulation device, there will be no problem like the above, but if you test it after the logic operation circuit and the 2/3 logic circuit are assembled and completed as a product, you will not be able to test it. Often included in the process. In such a case, in order to test the logical operation circuit alone, it is necessary to remove the wiring that has been done once and then rewire it. Furthermore, the output signal of the logic operation circuit is used as an internal signal of the control device when it cannot directly interface with the outside.

[Purpose of the invention]

The present invention is a digital control device consisting of a triple logic operation circuit and a 2/3 logic circuit, and when checking its operation, the output signal of any one series of logic operation circuits to be tested is artificially changed. It is an object of the present invention to provide a digital control device that uses the output signal of a 2/3 logic circuit and enables an operation confirmation test of each series independently.

[Summary of the invention]

In the present invention, when inputting the output signal of the three-series ruru logic operation circuit to the 2/3 logic circuit, it is inputted as is in normal times, that is, when no test is performed, and when any one series of tests is performed, the output signal is inputted as is. The output of one of the remaining two series is turned on and the output of the other series is inputted as off, and the output signal of the circuit under test is selected by the 2/3 logic circuit to achieve the specified purpose. It is something to do.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIG.

The difference between FIG. 1 and FIG. 3 is that a test signal generation circuit 5 and a selection logic circuit 4 are provided. The test signal generating circuit 5 selects any one of the three series of logical operation circuits to be tested, and the selection is made manually. The output signals 51a, 51b, and 51c of the test signal generation circuit 5 are turned on when the logic operation circuits 11a, llb, and llc are the test targets, respectively.

Normally, for example, when used in combination with an actual process, the signals 51a, 51b, and 51c are off.

The selection logic circuit is each output signal 11a of the logic operation circuit.

11b and llc according to their values and transmits them to the 2/3 logic circuit 2.

If all the b signals 51a, 51b and 51c are turned off, the values of the output signals 41a, 41b and 41C of the selection logic circuit correspond to the values of the signals 11a, llb and 1lcO, respectively. Further, for example, if the signal 51r is turned on and the signals 51b and 51c are turned off, that is, when the logic operation circuit 1a is being tested, the value of the signal 41a will be the same as that of the signal 11a.
pl, and the value of signal 41b is on regardless of the value of signal 11b, and the value of signal 41c is equal to signal 1.
It turns off regardless of the value of 1C. Therefore 2/3
Logic circuit output signal 41a1, that is, logic operation circuit 1a
is equal to the value of the output signal 11a. Logical operation circuit 11
The same applies when testing B.ILC.

As mentioned above, under normal conditions, the percentage of the output of each triplexed series is
Logic outputs are obtained, and when the function of any one series is to be verified, the logic outputs of that series are given as the final outputs of the respective control devices. As a result, when checking the operation of any one system, that system alone is connected to the test simulation device, making it easy to test without being disturbed by the output signals of the other two systems. becomes. When used in combination with an actual process, the selection logic circuit has no effect on the output signals of each series, and the components of the selection logic circuit are also extremely simple compared to logic operation circuits, so triplexing is possible. Highly reliable operating conditions can be maintained.

Even if the selection logic circuit 4 shown in FIG. 1 is configured as shown in FIG. 2 by changing the order of the OR logic and the AND logic, exactly the same function can be obtained. By the way, the selection logic circuit according to the present invention is provided for the purpose of facilitating testing of multiplexed logic operation circuits, but even when used in combination with an actual process, two series may fail simultaneously and continue operation. It can be used even if you are unable to do so. That is, by specifying the remaining normal series in the test signal generation circuit 5, a temporary operation can be performed using only that series, and during this time it is possible to wait for recovery from the failure.

〔Effect of the invention〕

As described above, according to the present invention, since it is possible to artificially utilize only one arbitrary series in a triplex digital control device, it is highly effective in saving labor in simulation tests of circuits that perform complex logical operations. In addition, the configuration of the selection logic circuit that realizes this is simple, impairing the high reliability achieved by triplexing. Figure 1 is a block configuration diagram showing an embodiment of the digital control device according to the present invention, and Figure 2 is a selection logic circuit. FIG. 3 is a block configuration diagram showing another example of a logic circuit. FIG. 3 is a simulation test configuration diagram of a general triplex digital control device.

la, lb, lc...logic operation circuit, 2...2/3
Logic circuit, 3... Process simulation device, 4... Selection logic circuit, 5... Test signal generation circuit, lla, 11b,
11c...Logic operation circuit output signal, 51a, 51b,
51c... Test signal of logic operation circuit, 21...% logic output signal, 41a, 41b, 41c... Output signal of selection logic circuit.

Agent: Patent Attorney Noriyuki Chika Same as Hirofumi Mitsumata 2nd ffl

Claims (1)

[Claims] Three series of logic operation circuits that have the same operation function and operate in response to the same input signal, and a 2/3 logic circuit that receives three logic signals and determines the output signal based on majority logic. In a digital control device, normally the output of each series of logical operation circuits is transmitted as is to the 2/3 logic circuits, and when any one of the three series of logic operation circuits is designated, the specified The output signal of the selected series remains unchanged, the output signal of one of the remaining two series is forcibly turned on, and the output signal of the other series is forcibly turned off and transmitted to the 2/3 logic circuit. 1. A digital control device comprising a logic circuit and configured such that a specified series of logic output signals becomes an output signal of a 2/3 logic circuit.