JPS60225022A - Abnormality diagnostic circuit of double sensor system - Google Patents

Abstract

PURPOSE:To discriminate the abnormality of either one of two sensors by detecting abnormality, in a double system sensor comprising two sensors, by taking the sum and difference of the outputs of the two sensors and detecting the polarities of the change amounts of the sum and difference. CONSTITUTION:Two sensors A, B are provided to a plant 1 and biases C, -C are added to the outputs thereof while outputs SA+C, SB-C are inputted to an average processing part 2 and outputted as a sensor signal S=(SA+SB)/2. Further, said outputs are inputted to a difference signal detection part 4 and the difference D=(SA-SB)+2C thereof is calculated. Next, the change amount DELTAD of the difference D is compared with a prescribed value eta to detect abnormality. The change amount DELTAS of output S and the output DELTAD are inputted to an abnormality discrimination part 6 and the abnormality of either one of sensors is detected from the positive and negative combination of the change amounts DELTAS, DELTAD. For example, if both of the change amounts DELTAS, DELTAD are +, it is judged that the output of the sensor A is excessive and, if the change amount DELTAS is + and the change amount DELTAD is -, it is judged that the output of the sensor B is excessive. Because the change amounts of the sum and difference of the sensor outputs are calculated, and abnormal sensor can be detected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an abnormality diagnostic circuit for a dual sensor system that detects an abnormality in the dual sensor system and determines which sensor is abnormal.

[Technical background of the invention and its problems] An example of a conventional abnormality diagnosis circuit for a dual sensor system is shown in FIG.

In FIG. 1, duplex sensor A of plant 1.

Of B, the output S of the sensor person is output as a sensor signal, and the outputs SA and SB of sensor A and sensor B are sent to the comparator circuit 2.
1 and a discrimination circuit 22, and a mismatch is determined based on the difference between them, and an abnormality in the duplex sensor is thereby detected.

However, the circuit shown in FIG. 1 only detects a mismatch between the two sensors, and cannot determine which sensor is abnormal.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a duplex sensor system abnormality diagnostic circuit that can detect an abnormality in a duplex sensor, including determining which sensor is abnormal.

[Summary of the invention]

The present invention provides an abnormality diagnosis circuit 1 for a duplex sensor system that detects an abnormality in a duplex sensor consisting of two sensors.
A comparison calculation unit that stores the sum and difference between the outputs of two sensors for each sampling step and calculates the amount of change for each step, and determines that the sensor is abnormal when the amount of change in the difference is equal to or greater than a predetermined value, and also determines the amount of change in the difference. It is equipped with an abnormality determination section that discriminates the abnormal sensor and its abnormal direction from the polarity of the polarity and the polarity of the amount of change in the sum.This makes it possible to detect sensor abnormalities in the dual sensor system, including which sensor is abnormal. In addition, a sensor switching unit is provided to extract the sensor output from the healthy sensor when an abnormal sensor is discriminated.

[Embodiments of the invention]

An embodiment of the present invention is shown in FIG.

In FIG. 2, duplex sensor A of plant 1.

A bias C is applied to the positive side of the sensor A in B, and the same bias C is applied to the negative side of the sensor B, and the outputs S+C and 5B-C are subjected to averaging processing SA+SB processing section 2. The average value 2 is output as the sensor signal S.

In this case, if both sensors A and B are normal, 5A-81
It is 1.

The above sensor outputs SA+C and 8B-C are input to the difference signal detection section 4, and the difference D= (sA+c) - (SII-C) = (smu-8
B) +20 is calculated.

The difference signal detection unit 4 further samples the above difference, compares the previous D and the current D, and sets the difference △D to a specified value η.
Compared to
η (8A-'I's is a decreasing trend), and depending on each determination result, (→, (-) signal is an abnormal value and the current value is stored in the signal storage unit 5. and is directly input to the abnormality determination unit 6, and the previous value and current value are compared based on the difference ΔS, and when there is an upward trend, that is, ΔS>O (
→, when there is a downward trend, that is, ΔS is 0 (→ is determined).

The abnormality determination unit 6 further determines the abnormal sensor based on the polarity of ΔD and the polarity of ΔS.

In other words, when △S is (g) and △D is (+), sensor A
Excessive output, when ΔS is (→ and ΔD is (→), sensor B
Excessive output, when ΔS is (→ and ΔD is (→), sensor B
If the output is too low, ΔS is ←) and ΔD is (→), sensor A
It determines that the output is too low and outputs an abnormal sensor detection signal.

FIG. 3 shows another embodiment of the present invention, in which a sensor switching section 7 is further provided in the circuit of FIG.
The output of the sensor is used as the sensor signal, and when a sensor abnormality is detected, the sensor is switched to the normal sensor side and the output is used as the sensor signal.

FIG. 4 shows yet another embodiment of the present invention, in which the determination of ΔS in FIG. A timer element is added to provide a time delay for abnormality detection.

Further, FIG. 5 shows a case where the abnormality diagnosis section in the present invention is configured by a microcomputer.

That is, the difference signal detection section 4, signal storage section 5, and abnormality determination section 6 shown in FIG.

FIG. 6 is a flowchart showing the arithmetic processing operation, and the same arithmetic operation as in the case of FIG. 2 is performed.

[Effects of the Invention] As explained above, according to the present invention, it is possible to detect an abnormality in a duplex sensor system by distinguishing which sensor is abnormal, and also to automatically switch the sensor output to the healthy side as necessary. A reasonable abnormality diagnosis circuit for a redundant sensor system that improves plant reliability and operation rate can be obtained.

[Brief explanation of drawings]

Fig. m1 is a system diagram showing an example of an abnormality diagnosis circuit of a conventional dual sensor system, Figs. It is a flowchart showing calculation operation. 1 Plant 2 Average processing unit 3 Abnormality diagnosis unit 4 Difference signal detection unit 5 Signal storage unit 6 Abnormality determination unit 7 Sensor switching unit 9 Memory 10 CPU (8733) Agent Patent attorney Yoshiaki Inomata (1 person) 1st Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

Claims (2)

[Claims] (1) In an abnormality diagnosis circuit of a duplex sensor system that detects a duplex sensor switching section consisting of two sensors, the sum and difference of the outputs of the two sensors are stored for each sampling step, and the sum and difference of the above sum and difference are calculated for each step. A comparison calculation unit that calculates the amount of change, and determines that the sensor is abnormal when the amount of change in the difference is greater than or equal to a predetermined value, and also discriminates the abnormal sensor and the direction of the abnormality based on the polarity of the change in the difference and the polarity of the amount of change in the upper Ki sum. A redundant sensor system abnormality diagnostic circuit characterized by having an abnormality discrimination section that detects the abnormality. (2) An abnormality diagnosis circuit for a dual sensor system according to claim 1, further comprising a sensor switching unit that extracts sensor output from all other sensors when an abnormal sensor is discriminated.