JPH0823828B2 - Signal selector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial field of application> The present invention selects one of the four input signals that simultaneously measure the same physical state as the signal with the highest reliability.
The present invention relates to an improvement in a signal selector for selecting individual pieces.

<Prior Art> In instrumentation of an atomic couplant, it is common to take a redundancy method in order to improve the system reliability and meet the standard (for example, IEEE-279-1971). In addition, when checking one of the redundant signal systems online, it is necessary to ensure sufficient reliability among the remaining signal systems. In general, the most reliable signal is always selected and used.

FIG. 6 shows a prior art example of a signal selector used for such a purpose.

A, B, C and D are four input signals, the first high selector 1 inputs the signals A and B, the second high selector 2 inputs the signals B and C, and the third high selector 3 Input signals C and D.

The fourth high selector 4 inputs the outputs of the first and second high selectors. The fifth high selector 5 inputs the outputs of the second and third high selectors. As a result, the first and second high level signals of the input signals A to D are selected as the outputs of the fourth and fifth high selectors.

Reference numeral 6 is a low selector for inputting the outputs of the fourth and fifth high selectors, and the selection output thereof is the second high level signal X.

<Problems to be Solved by the Invention> As described above, the signal selector that always selects the second high-order signal among the four input signals is configured by the five high selectors and the one low selector. , There are the following problems.

In FIG. 7, assuming that the input signals A, B and C are normal and the signal D is abnormal at time t ₀ , the selection signal is A. Time t ₁
In, the signal C is selected to the test mode and gradually increased for the test, the signal C is selected at the time t ₂ and the signal D is selected at the time t ₃ .

A first object of the present invention is to provide a signal selector which can solve the problem that a signal which can be clearly judged to be abnormal is erroneously selected.

The second object of the present invention is to introduce the idea of a criminal record index for judging the past behavior of each input signal to enable selection in the case where four input signals are separated into two groups by two. In the provision of a signal selector.

<Means for Solving the Problems> The structural feature of the present invention is that a signal selector that selects one of four input signals performs mutual subtraction of each of the four input signals. 6 subtractors, 6 comparators that compare the absolute value of the operation result of these subtractors with a preset constant value, and any other input signal based on the outputs of these comparators. Exclude signal selection circuit that excludes the input to the signal selection circuit by selecting an input signal that is more than the set value from the value, and for the deviation between the selected output of the signal selection circuit and each of the input signals Normalization processing and digital filter processing are executed to calculate a criminal record index indicating an abnormality degree for each input signal, and a criminal record index calculation circuit that holds the criminal record index, and two input signals each having two or more constant values are provided in two groups. If you split into , A channel switching judgment circuit for selecting one from a group having a lower criminal record index is provided.

<Operation> Mutual subtraction is performed by the six subtractors on the four input signals, and the absolute value of the operation result of the subtractor is set to a predetermined constant value by the six comparators. Compared,
An exclusion signal selection circuit that inputs a comparison output determines an input signal that is apart from any other input signal value by a certain value or more, and excludes it from the input to the signal selector.

Further, the antecedent index calculation circuit performs a normalization process and a digital filter process on the deviation between the selected output of the signal selection circuit and each of the input signals, and the antecedent index for each input signal is calculated and held, and the input signal is 2 When the individual is divided into 2 groups above a certain value, this criminal record index is referred to,
One is selected by the channel switching judgment circuit from the group having a lower criminal record index.

<Example> An example of the present invention will be described with reference to FIG. 7 is the 6th
The signal selection circuit has the same configuration as the signal selection circuit described in the figure, and inputs the outputs A ′ to D ′ of the signal exclusion circuit that inputs four input signals A to D and outputs the second high signal x ′. To do.

The signal exclusion circuit 8 outputs the output signals A ′ to D ′ in which the level of the input signal determined to be abnormal is forcibly clamped to zero potential.

A configuration example of the signal exclusion circuit 8 will be described with reference to FIG. The input signals A, B, C, D are transmitted through the changeover switches 802, 803, 804, 805 which are selectively driven by the output M of the exclusion signal selection circuit 801, respectively.
It is output as ´, B´, C´, D´.

In each of the changeover switches, the changeover piece is clamped to the output side, one terminal is clamped to the input signal side, and the other terminal is clamped to zero potential, and when the output M of the exclusion signal selection circuit excludes the input signal, 0% when the switching piece is connected to the terminal side
Is selected.

Reference numerals 806 to 811 are six subtractors, and 806 is an AB
07 subtracts BC, 808 subtracts CD, 809 subtracts DA, 810 subtracts AC, and 811 subtracts BD.

812 to 817 are six comparators, and six subtractors 806 to 8
The output of 11 is input and its absolute value is compared with a preset constant value ε. If it is less than ε, a normal value 0 is output, and if ε is abnormal, an abnormal value 1 is output.

The outputs of these comparators are input to the exclusion signal selection circuit 801, and an abnormal signal is determined.

The abnormal signal referred to here is a signal that is separated from all the signals other than itself by a constant value ε or more, for example, the third signal.
The determination is made by the algorithm shown in the flow chart of the figure.

Data buffers NA, NB, NC, ND corresponding to the signals A, B, C, D are prepared and cleared to zero before the start of judgment.

When the outputs of the comparators 812 to 817 are 1, 1 is added to the value of the data buffer of the signal corresponding to the input of the subtractor connected to each comparator.

After the output judgment of all the comparators is completed, the values of the data buffers NA to ND are checked, and signals having a value of 3 or more are excluded. In this case, an algorithm that excludes the maximum value may be used.

After the exclusion signal determination work is completed, the changeover switches 802 to 805 are switched according to the result to set the abnormal input signal output to 0%.

To restore the exclusion signal (switch switch to state),
It is performed when the difference from the currently selected signal is within ε.

Although such an algorithm can exclude an abnormal signal in a pattern that can usually occur, there are cases in which it cannot be excluded in a special case. That is, for example, as in the case of the input signals A and B in the normal proximity state,
This is a case where the C and D groups are abnormally distant from each other, and in this case, as shown in the intercomparison matrix file 818, the value of each data buffer NA, NB, NC, ND is 2, 2, 2, 2. It becomes a state and abnormal and normal cannot be differentiated.

Incidentally, the signal Q is an external transmission signal of the contents of the comparison matrix file 818, and the signal P is a signal for transmitting excluded input signal information to the outside.

The present invention uses a criminal record index as a means for dealing with the above-described case where the differentiation cannot be made. This is an index indicating a signal abnormal state in the near past. Hereinafter, a method of normalizing an input signal and obtaining the previous index will be described.

Returning to FIG. 1, an embodiment of the antecedent index calculating circuit 10 shown by a chain line block will be described.

101 to 104 is a subtractor, and the output signal X of the signal selection circuit 7
'And the deviation e between the outputs A'to D'of the signal exclusion circuit 8 are calculated and input to the determination circuits 105 to 108 for the normalization processing.

FIG. 4 is a characteristic diagram of this determination circuit. When the absolute value of the deviation e is ε ₁ or less, it is 0, and when it is ε ₂ or more, it is 1 and ε _{2.
When 1 to} ε ₂ , it is converted into a normalized signal f (x) that takes a number between 0 and ₁ in proportion. This normalized signal is a parameter indicating the current degree of abnormality of each input signal with reference to the output X ′ of the signal selection circuit 7.

Reference numerals 109 to 112 denote digital filter circuits for performing digital filter processing on the normalized signals of the determination circuits 105 to 108.

FIG. 5 is a diagram for explaining the operation of the digital filter,
If the filter output of the previous control cycle t _n-1 is in Z _n-1, there is an input of f (x) with respect to this, the output Z _n of the current control cycle t _n is, Z _n = {f (X) -Zn _-1 } r + Zn _-1 = (1-r) Zn _-1 + r.f (x) is output. Here, r is a gain.

The output Z _n of this digital filter is a parameter indicating the degree of abnormality of each input signal from the past to the present, and this is named a criminal record index.

Reference numerals 113 to 116 _denote clamp circuits driven by the excluded input signal information P transmitted from the signal excluding circuit 8 and setting circuit 11 for the antecedent index output Z _n for the excluded input signal.
It is forcibly regulated to "1" by the output of 7.

Reference numerals 118 to 121 denote antecedent index holding circuits corresponding to the respective input signals, and hold antecedent index outputs from the digital filters 109 to 112 via the clamp circuits 113 to 116. H _A , H
_B , H _C , and H _D are continuous outputs of these hold circuits.

In FIG. 1, 9 is a channel switching determination circuit,
If the output X'of the signal selection circuit, the output Q of the comparison matrix contents from the signal exclusion circuit, and the hold outputs H _{A to} H _D of the antecedent index are input, and the total of the data buffers is other than 2,2,2,2 X ′ is output as it is as X ₀ , and when the total of the data buffer becomes 2,2,2,2, it is output as X ₀ by switching to the second high signal of the group with the lower criminal record index. .

<Effects of the Invention> As described above, according to the present invention, referring to FIG. 7, since the signal D is excluded from the beginning, the signal C is not selected at the time t ₂ , and even if the time t _{Even if} the deviation between C and D is within ε in ₃ , the deviation from the selected signal A is ε.
Since it is not within the time, D cannot return and the time is the same as before.
There is no danger that D will be selected at t ₃ .

Even in the special case where the signal D is at a level that is not excluded from the beginning and is separated into A and B groups and C and D groups by ε or more as at time t ₃ , it is safe from past behavior by referring to the previous criminal index. It is possible to select one from the group with the highest frequency.

[Brief description of drawings]

1 is a configuration diagram showing an embodiment of the present invention, FIG. 2 is a configuration diagram showing an embodiment of a signal exclusion circuit, FIG. 3 is a flow chart diagram showing an example of a determination algorithm of an exclusion signal selection circuit,
FIG. 4 is an operation explanatory diagram of a normalization processing judgment circuit, FIG. 5 is an operation explanatory diagram of a digital filter, FIG. 6 is a configuration diagram showing an example of a conventional technique, and FIG. 7 is an operation explanatory diagram thereof. . 1-5 ... 1st-5th high selector, 6 ... low selector, 7 ... signal selection circuit, 8 ... signal exclusion circuit, 9 ...
Channel switching judgment circuit, 10 ... former index calculation circuit

Claims (1)

[Claims] 1. A signal selector for selecting one of four input signals, six subtracters for performing mutual subtraction of each of the four input signals, and these subtracters. 6 comparators that compare the absolute value of the calculation result of 1 with a preset constant value, and an input signal that is more than the above set value from any other input signal value based on the output of these comparators. An exclusion signal selection circuit for selecting and excluding the input to the signal selection circuit, and a normalization process and a digital filter process for the deviation between the selection output of the signal selection circuit and each input signal for each input A criminal record index computing circuit that calculates a criminal record index indicating the degree of abnormality for each signal and holds the criminal record index, and refers to the above criminal record index when two of the input signals are divided into two groups each having a predetermined value or more. Is it a group with a low criminal record? Signal selector that and a channel switching judgment circuit for selecting one of the.