Method for monitoring at least two redundant sensors

Abstract

The invention relates to a method for monitoring at least two redundant sensors, which are in particular arranged in a chemical plant or an aircraft, comprising providing a first sensor signal of a first sensor, the first sensor signal comprising at least one measured value, providing at least one further sensor signal from a further sensor, the further sensor signal comprising at least one further measured value, generating a first analysis signal from the first sensor signal, generating at least one further analysis signal from the further sensor signal, determining at least one relationship between the first sensor signal and the further sensor signal at least in dependence on the first analysis signal and the further analysis signal over a time horizon, comparing the relationship with at least one admissible range, and, depending on the result of the comparison, determining whether at least one sensor of the two redundant sensors is faulty.

1 . A computer-implemented method for monitoring at least two redundant sensors arranged in a chemical plant or an aircraft, comprising:
 a) providing at least two redundant sensors,   b) providing a first sensor signal of a first sensor of the at least two redundant sensors, the first sensor signal comprising at least one measured value,   c) providing at least one further sensor signal from a further sensor of the at least two redundant sensors, the further sensor signal comprising at least one further measured value,   d) generating at least one first analysis signal from the first sensor signal,   e) generating at least one further analysis signal from the further sensor signal,   f) selecting a time horizon for the sensor signals from b), c) by comparison of the analysis signals from d) and e) with predefined limits for the variance, stationarity and/or dynamics of the sensor signal,   g) determining at least one correlation between the first analysis signal of the first sensor and the analysis signal of the further sensor,   h) comparing the correlation with at least one admissible correlation range or the difference with an admissible difference range, and   i) depending on the result of the comparison according to h), determining whether at least one sensor of the two redundant sensors is faulty,   j) issuing the determination according to i);   
       wherein
 in d), a standard deviation of the first sensor signal is generated, and 
 in e), a standard deviation of the further sensor signal is generated, and 
 in f), the horizon is a moving horizon, wherein the standard deviation of the first sensor signal and the standard deviation of the further sensor signal respectively do not exceed a specified stationarity limit for the same period of time or for the same points in time, in g), the average deviation between the at least one measured value of the first sensor signal and the at least one measured value of the further sensor signal is determined, and, in h), the average deviation is compared with an admissible average deviation. 
 
     
     
         2 . The method according to  claim 1 , wherein
 a spatial distance between the first sensor and the further sensor is determined, and   depending on a volumetric flow measurement and on the spatial distance between the sensors, at least one of the sensor signals provided is processed on a time basis.   
     
     
         3 . The method according to  claim 2 , wherein
 depending on the spatial distance between the first sensor and the further sensor, one of the sensor signals provided is processed on a time basis by a delay element of at least the first order, and/or   depending on the volumetric flow measurement and on the spatial distance between the sensor and the further sensor, one of the sensor signals provided is processed on a time basis by a dead time element.   
     
     
         4 . Method according to  claim 1 , wherein, before determination of the first analysis signal and/or of the further analysis signal, at least one of the recorded sensor signals is filtered in a filtering step in such a way that at least measuring noise is filtered out from the sensor signal. 
     
     
         5 . A computer-implemented method for monitoring at least two redundant sensors arranged in a chemical plant, comprising:
 a) providing at least two redundant sensors,   b) providing a first sensor signal of a first sensor of the at least two redundant sensors, the first sensor signal comprising at least one measured value,   c) providing at least one further sensor signal from a further sensor of the at least two redundant sensors, the further sensor signal comprising at least one further measured value,   d) generating at least one first analysis signal from the first sensor signal,   e) generating at least one further analysis signal from the further sensor signal,   f) selecting a time horizon for the sensor signals from b), c) by comparison of the analysis signals from d) and e) with predefined limits for the variance, stationarity and/or dynamics of the sensor signal,   g) determining at least one correlation between the first analysis signal of the first sensor and the analysis signal of the further sensor,   h) comparing the correlation with at least one admissible correlation range or the difference with an admissible difference range, and   i) depending on the result of the comparison according to h), determining whether at least one sensor of the two redundant sensors is faulty,   j) issuing the determination according to i);   
       wherein
 in d), a second derivative of the first sensor signal is generated, and 
 in e), a second derivative of the further sensor signal is generated, and 
 in f), a horizon in which there are a minimum number of datapoints is ascertained, comprising a second time derivative, the absolute value of which lies above a specified dynamics limit value of the second derivative, and 
 
       wherein
 in d), a standard deviation of the first sensor signal is generated as a further analysis signal of the first sensor signal, and 
 in e), a standard deviation of the further sensor signal is generated as a further analysis signal of the further sensor signal, and 
 in g), the determination of a correlation comprises maximizing the cross-correlation between the standard deviation of the first sensor signal and the standard deviation of the further sensor signal. 
 
     
     
         6 . The method according to  claim 5 , wherein the cross-correlation is maximized by maximizing the covariance between the standard deviation of the first sensor signal and the standard deviation of the further sensor signal by way of different time displacements (ΔT). 
     
     
         7 . The method according to  claim 6 , wherein
 a fouling time is determined as the correlation from the time displacement performed,   the fouling time is compared with an admissible fouling time range, and   depending on the result of the comparison, it is determined whether there is a faulty sensor.   
     
     
         8 . The method according to  claim 1 , wherein
 a spatial distance between the first sensor and the further sensor is determined, and   depending on a volumetric flow measurement and on the spatial distance between the sensors, at least one of the sensor signals provided is processed on a time basis.   
     
     
         9 . The method according to  claim 8 , wherein
 depending on the spatial distance between the first sensor and the further sensor, one of the sensor signals provided is processed on a time basis by a delay element of at least the first order, and/or   depending on the volumetric flow measurement and on the spatial distance between the sensor and the further sensor, one of the sensor signals provided is processed on a time basis by a dead time element.   
     
     
         10 . The method according to  claim 1 , wherein, before determination of the first analysis signal and/or of the further analysis signal, at least one of the recorded sensor signals is filtered in a filtering step in such a way that at least measuring noise is filtered out from the sensor signal. 
     
     
         11 . A monitoring device for performing the method of monitoring at least two redundant sensors arranged in a chemical plant or an aircraft according to  claim 1 , comprising:
 at least one receiving device designed for receiving a first sensor signal of a first sensor of the two redundant sensors and for receiving at least one further sensor signal from a further sensor of the two redundant sensors,   the first sensor signal comprising at least one measured value and the further sensor signal comprising at least one measured value,   at least one processing device designed for generating a first analysis signal from the first sensor signal and for generating at least one further analysis signal from the further sensor signal,   the processing device being designed for determining at least one correlation condition between the first sensor signal and the further sensor signal at least in dependence on the first analysis signal and the further analysis signal, wherein the at least one correlation condition comprises selecting a time horizon for the sensor signals by comparison of the analysis signals with predefined limits for the variance, stationarity, and/or dynamics of the sensor signal, and determining at least one correlation between the first analysis signal of the first sensor and the analysis signal of the further sensor,   at least one comparing device designed for comparing the correlation condition with at least one admissible correlation range, and   at least one evaluation device designed for determining whether, depending on the result of the comparison, at least one sensor is faulty.   
     
     
         12 . Chemical plant, comprising:
 at least one monitoring device according to  claim 11 .   
     
     
         13 . Aircraft, comprising:
 at least one monitoring device according to  claim 11 .