Patent ID: 11971950
Assignee: nan
Field: Measurement (Instruments)
Classification: CPC G | IPC G

Claim 0:
1. A method for onset time detection of a time-domain acoustic emission signal of a concrete beam based on histogram distance, comprising the following steps:
(1) acquiring the time domain acoustic emission signal: breaking a pencil lead on the concrete beam by pressing the pencil lead against a surface of the concrete beam; attaching a piezoelectric acoustic emission sensor to the concrete beam, and collecting energy released by the pencil lead from the piezoelectric acoustic emission sensor as the acoustic emission signal containing n elements, n being an integer greater than 2;
(2) dividing the time-domain acoustic emission signal: dividing the acquired acoustic emission signal that contains n elements into two intervals by a sliding point k at each iteration in a sliding operation, the sliding point k representing the kth element in the n elements; marking the two intervals wherein one is marked as Interval A and the other is marked as Interval B; fitting the Interval A to the interval from the 1st to kth element, and fitting the Interval B to the interval from (k+1)th to nth element;
(3) obtaining a relative frequency histogram of the Interval A and the Interval B, respectively:
(3.1) defining a histogram: let y be a measurement and have one of b bins contained in an ordinal set, Y={y1, . . . , yi, . . . , yb}, wherein i=1, 2, . . . , b, and yi<yi+1;

considering an acoustic emission signal generated from the concrete beam X={x1, x2, . . . , xj, . . . xn} containing n elements, wherein j=1, 2, . . . n, and xj falling within one of the bins of Y; defining the histogram of the signal X by the relationship:

hx=[h1x,h2x, ⋅ ⋅ ⋅ ,hix, ⋅ ⋅ ⋅ ,hbx],i=1,2, ⋅ ⋅ ⋅ ,b, 

wherein defining hx as the histogram of the signal X, b being a total number of bins of the histogram in the signal X, and hix being a value of the ith bin of the histogram of the signal X and defining hix by the relationship:, h
    i
    x
   
   =
   
    
     ∑
     
      j
      =
      1
     
     n
    
    
     c
     ij
    
   
  
  ,
  
   i
   =
   1
  
  ,
  2
  ,
  …
     
  ,
  b
  ,
 

 and j=1, 2, . . . , n, wherein, c
   
    i
    ⁢
    j
   
  
  =
  
   {
   
    
     
      
       
        1
        ,
       
      
      
       
        
         x
         j
        
        ∈
        
         [
         
          
           y
           i
          
          ,
          
           y
           
            i
            +
            1
           
          
         
         ]
        
       
      
     
     
      
       
        0
        ,
       
      
      
       otherwise
      
     
    
    ;
   
  
 

 and
(3.2) calculating the relative frequency histograms of two intervals A and B: defining the relative frequency histograms of said intervals A and B by the relationship,, p
    i
    A
   
   =
   
    
     
      
       h
       i
       A
      
      
       k
       A
      
     
     ⁢
        
     and
     ⁢
     
       
        
     
     ⁢
     
      p
      i
      B
     
    
    =
    
     
      h
      i
      B
     
     
      k
      B
     
    
   
  
  ,
 

 wherein piA and piB being a probability of elements that falling within the ith bin of said histogram in the intervals A and B respectively, hiA being a value of the ith bin of the histogram of the intervals A, hiB being a value of the ith bin of the histogram of the interval B, and kA being a total number of elements of the interval A and kB being a total number of elements of the interval B;

(4) obtaining a histogram distance between the relative frequency histograms of the Interval A and the Interval B:
(4.1) defining the histogram distance by the relationship:, d
     B
    
    (
    
     
      h
      A
     
     ,
     
      h
      B
     
    
    )
   
   =
   
    
     
      1
      -
      
       B
       ⁡
       (
       
        
         h
         A
        
        ,
        
         h
         B
        
       
       )
      
     
    
    =
    
     
      1
      -
      
       
        ∑
        
         i
         =
         1
        
        n
       
       
        
         
          p
          i
          A
         
         ⁢
         
          p
          i
          B
         
        
       
      
     
    
   
  
  ,
 

wherein dB(hA, hB) being the histogram distance between the histograms hA and hB, B(hA, hB) being the Bhattacharyya coefficient between the histograms hA and hB and defining B(hA, hB) by the relationship:, B
    ⁡
    (
    
     
      h
      A
     
     ,
     
      h
      B
     
    
    )
   
   =
   
    
     ∑
     
      i
      =
      1
     
     n
    
    
     
      
       p
       i
       A
      
      ⁢
      
       p
       i
       B
      
     
    
   
  
  ;
 

 and
(4.2) moving the sliding point k: after calculating the histogram distance of the Interval A and the Interval B, moving the sliding point k to the next element to obtain an interval from the 1st to (k+1)th element and the other from (k+2)th to nth element, generating histograms of the interval from the 1st to (k+1)th element and the other from (k+2)th to nth element and calculating the histogram distance between the interval from the 1st to (k+1)th element and the other from (k+2)th to nth element; moving the sliding point k from the first element to the nth element and moving one element; at each iteration in the sliding operation; and

(5) determining the onset time: according to the definition of dB(hA, hB), regarding the sliding point k with a maximum value of the histogram distance as the onset time of an acoustic emission signal.