JPS62224801A - Device for obtaining highly reliable one numerical value signal from three numerical value signals - Google Patents

Abstract

PURPOSE:To obtain a selecting system having good characteristic in a tripled controlling device etc. by executing examination according to a probability curve of predetermined deviation between signals and adopting a weighted average weighted according to the probability curve. CONSTITUTION:Three inputs 2, 3, 4 from the same detection point select and output 5 a value considered to be the surest through numerical value calculation by an arithmetic unit 1. That is, in the case where >=two out of three input signals are at upper, lower limit value (detector is defective), or the sum of values of the probability curve determined from signal deviation between each two is smaller than a constant K (>0), an alarm is given and this system of calculation is not adopted. When more than two are not at upper or lower limit values, and the sum of probability curves is equal to or larger than K, a weighted average in which the weight is determined by the probability curve is taken and the most probable value is made output. Thereby, when the relative relation of signal values is changed gently, the output signal changes gently and continuously.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a control system for a thermal power plant and a nuclear power plant, and particularly to a triplex system where high reliability is required.

[Conventional technology]

A method in which the highest and lowest values of three detection signals for the same measurement point are discarded, and the one in between is considered correct. If a problem occurs in one of the three signals, its influence can be excluded.

(Adopted by Toshiba for control equipment for nuclear couplants) [Problem that the invention seeks to solve] The above conventional technology has the following problems.

1) Since the intermediate value is simply assumed to be positive, the intermediate value is selected even if the three signals are different. In this case, the accuracy of the intermediate value is questionable.

2) If - signals fail, the one closer to the failure signal value of the two remaining healthy signals is selected.

(If there are two healthy signals, the average of them is desirable.) An object of the present invention is to provide a selection method that solves the above problems and has good characteristics.

[Means for solving problems]

The above objective is achieved by carrying out the test using a predetermined probability curve of signal amount deviation and by employing a weighted average weighted according to this probability curve.

[Effect]

The present invention is applied to a digital control device, and since the most probable value is selected through numerical calculation, there is no malfunction, and even if one signal fails, the output signal changes continuously.

〔Example〕

FIG. 1 is a block diagram showing the concept of the present invention, in which 1 is an arithmetic unit, 2, 3, and 4 are three inputs from the same detection point, and 5 is an output. Figure 2 shows the probability curve of the variation among the three input signals used when implementing this method, with the horizontal axis representing the deviation between two unique signals among the three signals, and the vertical axis representing the deviation This is the curve that takes the realization probability and is the maximum when the deviation is O (
For convenience, this value is assumed to be t-1,0), and as the deviation increases to the + side or the - side, it approaches O. Although this curve is theoretically given as a normal distribution curve (curve 1), it may be given as an approximate trapezoidal curve (curve 2).

The shape of this curve can be determined by the previously measured error curve of each detector (for example, the square root of the sum of the squares of each human error).

Figure 3 shows the calculation method according to the present invention, in which two or more of the three input signals are at the upper or lower limit of the signal (defective detector), or it is determined from the signal deviation between each two of them. If the sum of the values of the probability curves is smaller than the constant K (>O) (
In other words, if the signal amount deviation is extremely inconsistent), a warning will be issued and this calculation method will not be used at all. If the upper and lower limits are not met, and the sum of the probability curves is greater than or equal to K (i.e., two signals close to each other exist), calculate the most probable value by taking a weighted average of their weights determined by the probability curves, In other words, it is the output of this device.

In this figure, 1 is the starting point of calculation, 2 is a test block to check whether each input signal is close to each other, 3 is a warning to the operator, and 4Fi is an output signal using inputs that are close to each other (considered normal). A calculation block 5 indicates the end point of the calculation.

〔Effect of the invention〕

According to the method according to the present invention, the output signal is: (1) If the three signals are separated by more than the limit expected from the error of each detector (that is, if they are scattered and a reliable one cannot be identified), an alarm is issued. is issued to notify the operator and stop the calculation.

(2) If the two signals almost match and are separated by -
Take the average value of the two matched signals.

(8) If the three signals almost match, take a weighted average of the three signals weighted in consideration of the degree of mismatch.

(4) When the relative relationship between each signal value changes gradually, the output signal also changes slowly and continuously (does not change stepwise).

It has excellent characteristics as a highly reliable control system.

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram of an embodiment of the present invention, FIG. 2 is a basic signal deviation probability curve diagram, and FIG. 3 is a block diagram of an output signal calculation method using this curve. 1...High reliability signal calculation block.

Claims (1)

[Claims] 1. When handling three numerical signals of the same type in a triplex control system, etc., in order to eliminate as much as possible the influence of erroneous signals due to failures in the equipment that generates the signals, such as detectors and controllers, A permissible variation range is defined, and only when 2 or 3 signals exist within the range of variation, those signals are set as normal, and if the variation increases or decreases over time, the output of this device is set within the permissible range of variation. A device for obtaining one highly reliable numerical signal from three numerical signals, characterized in that the unified signal does not change suddenly.