Diagnostic systems and methods for predictive condition monitoring

Abstract

A system for empirically diagnosing a condition of a monitored system. Estimates of monitored parameters from a model of the system provide residual values that can be analyzed for failure mode signature recognition. Residual values can also be tested for alert (non-zero) conditions, and patterns of alerts thus generated are analyzed for failure mode signature patterns. The system employs a similarity operator for signature recognition and also for parameter estimation. Failure modes are empirically determined, and precursor data is automatically analyzed to determine differentiable signatures for failure modes.

What is claimed is:  
     
         1 . A monitoring apparatus for diagnosing faults in a system, comprising: 
 a reference data store containing failure mode identification data and associated parameter data indicative of behavior of said system in the failure mode; and    a similarity engine responsive to monitored parameter data indicative of monitored behavior of said system, for generating at least one similarity value for a comparison of the monitored parameter data to said failure mode associated parameter data, as a diagnostic indication of said failure mode.    
     
     
         2 . An apparatus according to  claim 1 , wherein said parameter data is residual data.  
     
     
         3 . An apparatus according to  claim 2 , further comprising: 
 a model for generating estimates of operational data in response to receiving operational data from said system; and    means for differencing the estimates and the received operational data to generate the residual data.    
     
     
         4 . An apparatus according to  claim 1 , further comprising failure identification means responsive to similarity values from the similarity engine for determining an indicated failure mode.  
     
     
         5 . An apparatus according to  claim 4 , wherein said failure mode identification means compares similarity values for a plurality of failure modes in said data store, and identifies at least the failure mode with the highest similarity as an indicated failure mode of said system.  
     
     
         6 . An apparatus according to  claim 4 , wherein said failure mode identification means compares similarity values for a plurality of failure modes in said data store, and identifies at least the failure mode with the highest average similarity as an indicated failure mode of said system.  
     
     
         7 . An apparatus according to  claim 4 , wherein said failure mode identification means compares similarity values for a plurality of failure modes in said data store, and identifies as an indicated failure mode of said system at least the failure mode with at least a selected number of highest similarities over a window of successive comparisons.  
     
     
         8 . An apparatus according to  claim 4 , wherein said failure mode identification means compares similarity values for a plurality of failure modes in said data store, and identifies as an indicated failure mode of said system at least the failure mode with at least a selected number of highest average similarities over a window of successive comparisons.  
     
     
         9 . A method for diagnosing faults in a monitored system, comprising the steps of: 
 acquiring monitored parameter data indicative of monitored behavior of said system; and    comparing for similarity the monitored parameter data to reference parameter data associated with a failure mode to generate a similarity value as a diagnostic indication of said failure mode.    
     
     
         10 . A method according to  claim 9 , wherein said parameter data is residual data.  
     
     
         11 . A method according to  claim 10 , further comprising the steps of: 
 generating estimates of operational data in response to acquiring operational data from said system; and    differencing the estimates and the received operational data to generate the residual data.    
     
     
         12 . A method according to  claim 9 , further comprising the step of determining an indicated failure mode based on similarity values resulting from the similarity comparisons.  
     
     
         13 . A method according to  claim 12 , wherein said determining step comprises comparing the similarity values for a plurality of failure modes, and identifying at least the failure mode with the highest similarity as an indicated failure mode of said system.  
     
     
         14 . A method according to  claim 12 , wherein said determining step comprises comparing the similarity values for a plurality of failure modes, and identifying at least the failure mode with the highest average similarity as an indicated failure mode of said system.  
     
     
         15 . A method according to  claim 12 , wherein said determining step comprises comparing the similarity values for a plurality of failure modes, and identifying as an indicated failure mode of said system at least the failure mode with at least a selected number of highest similarities over a window of successive comparisons.  
     
     
         16 . A method according to  claim 12 , wherein said determining step comprises comparing the similarity values for a plurality of failure modes, and identifying as an indicated failure mode of said system at least the failure mode with at least a selected number of highest average similarities over a window of successive comparisons.  
     
     
         17 . A monitoring apparatus for diagnosing faults in a system, comprising: 
 a similarity engine responsive to monitored parameter data from said system for generating estimates of the monitored parameter data;    an alert module disposed to produce parameter alerts in response to a comparison of said estimates to said monitored data; and    means for identifying an impending failure mode in said system by matching said parameter alerts with at least one reference alert pattern associated with said failure mode.    
     
     
         18 . An apparatus according to  claim 17 , wherein said alert module performs a sequential probability ratio test on at least one parameter.  
     
     
         19 . An apparatus according to  claim 17 , wherein said alert module produces an alert when the difference of an estimate and corresponding monitored data exceeds a selected threshold.  
     
     
         20 . A method for diagnosing faults in a monitored system, comprising the steps of: 
 comparing for similarity monitored parameter data from said system to reference parameter data characteristic of known behavior of said system;    generating estimates of the monitored parameter data based on the similarity comparison;    generating alerts in response to a comparison of said estimates to said monitored data; and    identifying an impending failure mode in said system by matching said parameter alerts with at least one reference alert pattern associated with said failure mode.    
     
     
         21 . A method according to  claim 20 , wherein said alert generating step comprises performing a sequential probability ratio test on at least one parameter.  
     
     
         22 . A method according to  claim 20 , wherein said alert generating step comprises producing an alert when the difference of an estimate and corresponding monitored data exceeds a selected threshold.  
     
     
         23 . A monitoring apparatus for diagnosing faults in a system, comprising: 
 a similarity engine responsive to monitored parameter data from said system for generating estimates of the monitored parameter data;    means for differencing the estimates and the monitored data to generate residual data; and    means for recognizing an impending failure mode by comparing for similarity said residual data to reference residual data associated with the failure mode.    
     
     
         24 . An apparatus according to  claim 23 , further comprising means for communicating remedial control commands to a control program for said system.  
     
     
         25 . An apparatus according to  claim 23 , further comprising a control module for operating said system, responsive to recognition of an impending failure of said system from said recognizing means for remedially controlling said system.  
     
     
         26 . An apparatus according to  claim 23 , further comprising a profile data store for storing and providing reference parameter data characteristic of known behavior of said system, to said similarity engine for generation of the estimates.  
     
     
         27 . An apparatus according to  claim 23 , further comprising a failure mode data store for storing said reference residual data and associated failure mode identification data.  
     
     
         28 . An apparatus according to  claim 27  wherein said failure mode data store also stores information about remedial steps specific to a failure mode.  
     
     
         29 . A method for diagnosing faults in a monitored system, comprising the steps of: 
 comparing for similarity monitored parameter data from said system to reference parameter data characteristic of known behavior of said system;    generating estimates of the monitored parameter data based on the similarity comparison;    differencing the estimates and the monitored data to generate residual data; and    comparing for similarity the residual data to reference residual data associated with a failure mode, as a diagnostic indication of said failure mode.    
     
     
         30 . A method according to  claim 29 , further comprising the step of communicating a remedial control command to a control program for said system.  
     
     
         31 . A method according to  claim 29 , further comprising the steps of: 
 recognizing an impending failure mode based on the residual similarity comparison step; and    controlling remedially said system responsive to recognition of an impending failure of said system.    
     
     
         32 . A computer program product for diagnosing faults in a monitored system, comprising: 
 a residual testing program module for generating alerts in response to residual signals characterizing behavior of said system; and    a fault pattern detection program module disposed to receive said alerts and indicate a fault in said system upon matching the alerts to a reference pattern associated with said fault.    
     
     
         33 . A program product according to  claim 32 , wherein the residual testing program module performs a sequential probability ratio test on said residuals.  
     
     
         34 . A program product according to  claim 32 , wherein the residual testing program module compares a residual to a threshold to generate an alert when the residual exceeds the threshold.  
     
     
         35 . A program product according to  claim 32 , further comprising an empirical model program module disposed to generate estimates of parameter signals from said system, and difference the parameter signals and the estimates to generate the residual signals.  
     
     
         36 . A program product according to  claim 35 , wherein said empirical model program module employs a similarity operator to generate said estimates.  
     
     
         37 . A method for forming a diagnostic monitoring system for a machine, comprising the steps of: 
 instrumenting a plurality of like machines with sensors;    operating said plurality of machines and collecting operational sensor data characterizing operation;    autopsying each of said plurality of machines upon failure to determine a failure mode, and storing the failure modes for use in the diagnostic monitoring system;    selecting a failure precursor portion of said operational sensor data collected for a selected interval prior to failure of each machine; and    distilling each said failure precursor data portion into at least one failure signature data set and associating each set with a corresponding failure mode.    
     
     
         38 . A method according to  claim 37  wherein said distilling step comprises selecting time-correlated snapshots of operational sensor data.  
     
     
         39 . A method according to  claim 37  wherein said distilling step comprises generating time-correlated snapshots of estimated sensor data corresponding to at least a selected failure precursor data portion, differencing the estimates with the selected failure precursor data to form residual snapshots, and selecting at least one residual snapshot to be associated with the failure mode.  
     
     
         40 . A method according to  claim 39  wherein the estimated sensor data is generated by an empirical model based on the collected operational sensor data.  
     
     
         41 . A diagnostic monitoring apparatus for a sensor-instrumented system selected from a process and a machine, comprising: 
 an operational model module for modeling said system and generating estimates for said sensors in response to receiving actual values of said sensors;    a differencing module for generating residual signals from said estimates and said actual values;    a reference library for storing failure modes and associated residual data values; and    a failure mode recognition engine disposed to compare generated residual signals with said residual data values to select and output a recognized failure mode for said system.    
     
     
         42 . A diagnostic monitoring apparatus according to  claim 41 , wherein said failure mode recognition engine comprises a similarity operation module for generating a similarity score for a comparison of said generated residual signals with said residual data values in said reference library.  
     
     
         43 . A diagnostic monitoring apparatus according to  claim 42 , wherein said failure mode recognition engine further comprises a failure mode decision module responsive to the similarity scores generated by the similarity operation module to select at least one failure mode to output.  
     
     
         44 . A diagnostic monitoring apparatus for a sensor-instrumented system selected from a process and a machine, comprising: 
 an operational model module for modeling said system and generating estimates for said sensors in response to receiving actual values of said sensors;    a differencing module for generating residual signals from said estimates and said actual values;    a testing module disposed to receive said residual signals and generate alerts in response thereto;    a reference library for storing failure modes and associated alert signatures; and    a failure mode recognition engine disposed to compare generated alerts with said alert signatures to select and output a recognized failure mode for said system.    
     
     
         45 . A diagnostic monitoring apparatus for a sensor-instrumented system selected from a process and a machine, comprising: 
 sensor input means for receiving current sensor data from said system in operation;    a reference library for storing failure modes and associated snapshots of sensor data from said system;    a failure mode recognition engine disposed to compare current sensor data with said snapshots to select and output a recognized failure mode for said system.    
     
     
         46 . A diagnostic monitoring apparatus according to  claim 45 , wherein said failure mode recognition engine comprises a similarity operation module for generating a similarity score for a comparison of said current sensor data with a snapshot of sensor data stored in said reference library.  
     
     
         47 . A diagnostic monitoring apparatus according to  claim 46 , wherein said failure mode recognition engine further comprises a failure mode decision module responsive to the similarity scores generated by the similarity operation module to select at least one failure mode to output.  
     
     
         48 . A diagnostic monitoring apparatus according to  claim 47 , wherein said failure decision module selects the at least one failure mode based on a highest similarity score for any one snapshot in said reference library.  
     
     
         49 . A diagnostic monitoring apparatus according to  claim 47 , wherein said failure decision module selects the at least one failure mode based on a highest average similarity score across sets of snapshots associated with each failure mode in said reference library.