Method of wave form segmentation and characterization of the segmented interval thereof

0Associated
Cases 
0Associated
Defendants 
0Accused
Products 
7Forward
Citations 
0
Petitions 
0
Assignments
First Claim
1. A method of partitioning a sampled signal waveform into several sections each of which includes a multiple of samples with a tracing waveform, comprising steps of:
 (a) updating the functional value of said tracing waveform at an (n+1)th sample with the amplitude of said signal waveform at an (n+1)th sample if the functional value of said tracing waveform at an nth sample is smaller than the amplitude of said signal waveform at an (n+1)th sample;
(b) comparing the functional value of said tracing waveform at an nth sample with that at an (n−
1)th sample of said tracing waveform if the functional value of said tracing waveform at an nth sample is greater than or equal to the amplitude of said signal waveform at an (n+1)th sample;
(c) either maintaining the functional value of said tracing waveform at an (n+1)th sample with that at an nth sample of said tracing waveform in case when the functional value of said tracing waveform at consecutively foregoing samples including an nth, an (n−
1)th, an (n−
2)th, . . . , has been kept constant wherein the number of samples is less than a predefined number k, or updating the functional value of said tracing waveform at an (n+1)th sample by subtracting the functional value of said tracing waveform at the nth sample with an average slope between the nth sample and the (n−
k)th sample that is regarded as a slopeinversion point in the case when the number of samples is more than or equal to said predefined number k at the step of (b);
(d) updating the functional value of said tracing waveform at an (n+1)th sample by subtracting a first slope from the functional value of said tracing waveform at an nth sample if the value of said tracing waveform at an nth sample is different from that at an (n−
1)th sample and the number of samples including the nth, (n−
1)th, an (n−
2)th, . . . of which the value has been decreasing with the same slope (said “
first slope”
) is less than a predefined number L, or by subtracting a second slope from the functional value of said tracing waveform at an nth sample if the number of samples decreasing with said first slope is greater than or equal to said predefined number L and the average slope (“
a second slope”
) between the nth sample and the (n−
L)th sample is steeper than said first slope multiplied by a predefined rate (X %), or by subtracting a first slope multiplied by said predefined rate (X %) from the functional value of said tracing waveform at an nth sample if said second slope is less steep than said first slope multiplied by said predefined rate (X %) at step of (b); and
(e) regarding the (n+1)th sample as a slopetransition point and regarding the interval between said slopchanging point and said slopeinversion point as a single section if the functional value of said tracing waveform at an (n+1)th sample is lees than or equal to the value of said signal waveform at an (n+1)th sample and thereby the two waveforms intersect.
0 Assignments
0 Petitions
Accused Products
Abstract
The present invention discloses a method of partitioning a waveform for characterization with a slopeinversion point and a slopetransition point by utilizing a slopetracing waveform, which can be utilized for the application to the physiological signal of a living body.
9 Citations
View as Search Results
THE PRESENT INVENTION IS DIRECTED TO A FEEDING TUBE IN PARTICULAR FOR TOTAL PARENTAL NUTRITION AND/OR MEDICINE DOSING  
Patent #
US 20100087715A1
Filed 11/09/2007

Current Assignee
Koninklijke Philips N.V.

Sponsoring Entity
Koninklijke Philips N.V.

Present invention is directed to a feeding tube in particular for total parental nutrition and/or medicine dosing  
Patent #
US 8,285,399 B2
Filed 11/09/2007

Current Assignee
Koninklijke Philips N.V.

Sponsoring Entity
Koninklijke Philips N.V.

Systems and methods for displaying patient data  
Patent #
US 9,524,569 B2
Filed 04/16/2013

Current Assignee
Airstrip IP Holdings LLC

Sponsoring Entity
Airstrip IP Holdings LLC

Method and apparatus for analyzing waveform signals of a power system  
Patent #
US 10,281,504 B2
Filed 03/25/2009

Current Assignee
ABB Schweiz AG

Sponsoring Entity
ABB Schweiz AG

Systems and methods for and displaying patient data  
Patent #
US 10,402,782 B2
Filed 03/13/2013

Current Assignee
Airstrip IP Holdings LLC

Sponsoring Entity
Airstrip IP Holdings LLC

Systems and methods for and displaying patient data  
Patent #
US 10,460,409 B2
Filed 02/28/2014

Current Assignee
Airstrip IP Holdings LLC

Sponsoring Entity
Airstrip IP Holdings LLC

Feature extraction apparatus and method for biometric information detection, biometric information detection apparatus, and wearable device  
Patent #
US 10,667,757 B2
Filed 01/24/2017

Current Assignee
Samsung Electronics Co. Ltd.

Sponsoring Entity
Samsung Electronics Co. Ltd.

Device and method for reducing number of data sample points sent to a video display system  
Patent #
US 5,365,428 A
Filed 01/21/1992

Current Assignee
Quinton Inc.

Sponsoring Entity
Quinton Instrument Co.

Physiological signals processing system  
Patent #
US 4,633,884 A
Filed 05/23/1984

Current Assignee
KABUSHIKI KAISYA ADVANCE KAIHATSU KENKYUJO

Sponsoring Entity
KABUSHIKI KAISYA ADVANCE KAIHATSU KENKYUJO

13 Claims
 1. A method of partitioning a sampled signal waveform into several sections each of which includes a multiple of samples with a tracing waveform, comprising steps of:
(a) updating the functional value of said tracing waveform at an (n+1)th sample with the amplitude of said signal waveform at an (n+1)th sample if the functional value of said tracing waveform at an nth sample is smaller than the amplitude of said signal waveform at an (n+1)th sample;
(b) comparing the functional value of said tracing waveform at an nth sample with that at an (n−
1)th sample of said tracing waveform if the functional value of said tracing waveform at an nth sample is greater than or equal to the amplitude of said signal waveform at an (n+1)th sample;
(c) either maintaining the functional value of said tracing waveform at an (n+1)th sample with that at an nth sample of said tracing waveform in case when the functional value of said tracing waveform at consecutively foregoing samples including an nth, an (n−
1)th, an (n−
2)th, . . . , has been kept constant wherein the number of samples is less than a predefined number k, or updating the functional value of said tracing waveform at an (n+1)th sample by subtracting the functional value of said tracing waveform at the nth sample with an average slope between the nth sample and the (n−
k)th sample that is regarded as a slopeinversion point in the case when the number of samples is more than or equal to said predefined number k at the step of (b);
(d) updating the functional value of said tracing waveform at an (n+1)th sample by subtracting a first slope from the functional value of said tracing waveform at an nth sample if the value of said tracing waveform at an nth sample is different from that at an (n−
1)th sample and the number of samples including the nth, (n−
1)th, an (n−
2)th, . . . of which the value has been decreasing with the same slope (said “
first slope”
) is less than a predefined number L, or by subtracting a second slope from the functional value of said tracing waveform at an nth sample if the number of samples decreasing with said first slope is greater than or equal to said predefined number L and the average slope (“
a second slope”
) between the nth sample and the (n−
L)th sample is steeper than said first slope multiplied by a predefined rate (X %), or by subtracting a first slope multiplied by said predefined rate (X %) from the functional value of said tracing waveform at an nth sample if said second slope is less steep than said first slope multiplied by said predefined rate (X %) at step of (b); and
(e) regarding the (n+1)th sample as a slopetransition point and regarding the interval between said slopchanging point and said slopeinversion point as a single section if the functional value of said tracing waveform at an (n+1)th sample is lees than or equal to the value of said signal waveform at an (n+1)th sample and thereby the two waveforms intersect.  View Dependent Claims (3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
 2. A method of partitioning a sampled signal waveform into several sections each of which includes a multiple of samples with a tracing waveform, comprising steps of:
(a) updating the functional value at an (n+1)th sample of said tracing waveform with the amplitude of said signal waveform an (n+1)th sample if the functional value of said tracing waveform at an nth sample is larger than the amplitude of said signal waveform at an (n+1)th sample;
(b) comparing the functional value of said tracing waveform at an nth sample with that at an (n−
1)th sample of said tracing waveform if the functional value of said tracing waveform at an nth sample is smaller than or equal to the amplitude of said signal waveform at an (n+1)th sample;
(c) either maintaining the functional value of said tracing waveform at an (n+1)th sample with that at an nth sample in case when the functional value of said tracing waveform at consecutively foregoing samples including an nth, an (n−
1)th, an (n−
2)th, . . . , has been kept constant wherein the number of times is less than a predefined number k, or updating the functional value of said tracing waveform at an (n+1)th sample with an (n+1)th sample by adding the functional value of said tracing waveform at the nth sample with an average slope between the nth sample and the (n−
k)th sample which is regarded as a slopeinversion point in case when the number of samples is more than or equal to said predefined number at the step of (b);
(d) updating the functional value of said tracing waveform at an (n+1)th sample by adding a first slope from the functional value of said tracing waveform at an nth sample if the value of said tracing waveform at an nth sample is different from that at an (n−
1)th sample and the number of samples including the nth, (n−
1)th, an (n−
2)th, of which the value has been increasing with the same slop (said “
first slope”
) is less than a predefined number L, or by adding a second slope from the functional value of said tracing waveform at an nth sample if the number of samples increasing with said first slope is greater than or equal to said predefined number L and the average slope (“
a second slope”
) between the nth sample and the (n−
L)th sample is steeper than said first slope multiplied by a predefined rate (X %), or by adding a first slope multiplied by said predefined rate (X %) from the functional value of said tracing waveform at an nth sample if said second slope is less steep than said first slope multiplied by said predefined rate (X %) at step of (b); and
(e) regarding the (n+1)th sample as a slopetransition point and regarding the interval between said slopchanging point and said slopeinversion point as a single section if the functional value of said tracing waveform at an (n+1)th sample is greater than or equal to the value of said signal waveform at an (n+1)th sample and thereby the two waveforms intersect.
1 Specification
[0001] The present invention relates to a method of partitioning a signal waveform and characterizing the section partitioned thereof, and more particularly, to a method of dividing a signal waveform into several sections, which is appropriate for recognizing the signal recognition through a mathematical integration of the waveform between a slopeinversion point and a slopetransition point.
[0002] The present invention can find its application in the area of the recognition of a wide range of signal waveforms including physiological signal of a living body such as ECG (electrocardiography), EEG (electroencephalography), EMG (electromyography), electrogram, endocardiogram, and pulsation waveform.
[0003] Traditionally, various approaches have been tried to partition a continuous timevarying signal waveform into sections. More often, a section of a signal waveform is defined as an interval between two curvaturetransitioning points where the curvature of the waveform changes its polarity.
[0004] The prior art, however, has a shortcoming in a sense that the density of partitioned sections tends to be excessively high if the signal waveform varies quite rapidly with respect to time.
[0005] Furthermore, the prior art has a limit because a couple of successive waveforms, for instance, in the case of physiological waveforms of a living body, are erroneously interpreted as a single continuous waveform.
[0006] Accordingly, it is an object of the present invention to provide a method of efficiently partitioning a signal waveform into sections and characterizing the sections partitioned thereof.
[0007] It is further an abject of the preset invention to provide a method of partitioning a signal waveform, which is appropriate to be applied for physiological signals of a living body, through utilizing a slopeinversion point and a slopetransition point.
[0008] In order to accomplish the abovementioned objects, the present invention provides a method of partitioning a signal waveform comprising steps of (a) updating the functional value of an (n+1)th sample with an amplitude of an (n+1)th sample if the functional value of an nth sample of a tracing waveform is less than the amplitude of an (n+1)th sample of a signal waveform; (b) comparing the functional value of an nth sample of said tracing waveform with the functional value of an (n1)th sample of said tracing waveform if the functional value of an nth sample of said tracing waveform is either greater than or equal to the amplitude of an (n+1)th sample of said signal waveform; (c) maintaining the functional value of an (n+1)th sample of said tracing waveform with a functional value of an nth sample in case when the functional value of an nth sample of said tracing waveform is the same as the functional values of (n−1)th, (n−2)th, (n−1)th samples wherein 1 is less than k, a predetermined number, and updating an (n+1)th sample of said tracing waveform by subtracting an amount with an average slope between the amplitude of an (nk)th sample and the amplitude of an nth sample in case when the functional value of an nth sample of said tracing waveform is the same as the functional values of (n−1)th, (n−2)th, . . . , (n−1)th samples wherein 1 is equal to k at the step of (b); (d) updating the value of an (n+1)th sample by subtracting an amount with the same slope from (referred as a first slope) the value of an nth sample if the functional value of said nth sample of said tracing waveform is different from those of (n−1)th, (n−2)th, (n−j)th samples wherein j is less than L, a predetermined value), and updating the value of an (n+1)th sample by subtracting an amount with an average slope between an (n−L)th sample of said signal waveform and an nth sample of the signal waveform (referred to as “a second slope”) if said second slope is steeper than said first slope by a predetermined amount rate (X %) and if the functional value of said nth sample of said tracing waveform is different form these of (n−1)th, (n−2)th, . . . , (n−j)th samples wherein j is equal to L), and updating the value of an (n+1)th sample by subtracting an amount with a new slope that is produced by multiplying a predetermined rate (X %) to said first slope if the value said second slope is smaller than that of the multiplication of said first slope by said predetermined rate (X %); and (e) recognizing an (n+1)th sample as a slopetransition point and considering the interval between said slopeinversion point and said slopetransition point as a single interval if the functional value of an (n+1)th sample of said tracing waveform is less than or equal to the amplitude of an (n+1)th sample of said signal waveform, thereby said two waveforms crossing.
[0009] Further feature of the present invention will become apparent from a description of a method of partitioning a signal waveform into sections with a slopeinversion point and a slopetransition point through a tracing waveform taken in conjunction with the accompanying drawings of an embodiment of the invention, which, however, should not be taken to be limitative to the invention, but are for explanation and understanding only.
[0010] In the drawings:
[0011]FIG. 1 is a schematic diagram illustrating a preferred embodiment of a lower slopetracing waveform with a signal waveform for the partition of the waveform into sections in accordance with the present invention.
[0012]FIG. 2 is a schematic diagram illustrating how a lower slopetracing waveform chases a signal waveform during the ascending stage where the amplitude of the signal waveform increases in accordance with the present invention.
[0013]FIG. 3 is a schematic diagram illustrating the behavior of a lower slopetracing waveform during the descending stage posterior to a slopeinversion point in accordance with the present invention.
[0014]FIGS. 4A though 4C are schematic diagrams illustrating the effect when the number of samples is varied for keeping the lower slopetracing waveform constant after a slopeinversion point has been detected, in accordance with the present invention.
[0015]FIG. 5 is a schematic diagram illustrating a preferred embodiment wherein a slopetransition point is determined with a lower slopetracing waveform and thereby the signal waveform in partitioned.
[0016]FIG. 6 is a schematic diagram illustrating an upper slopetracing waveform with a signal waveform for partitioning the signal waveform into sections in accordance with the present invention.
[0017]FIG. 7 is a schematic diagram illustrating the behavior of an upper slopetracing waveform during an ascending stage where a signal waveform increases to a maximum in accordance with the present invention.
[0018]FIG. 8 is a schematic diagram illustrating the behavior of an upper slopetracing waveform at descending stage posterior to a slopinversion point in accordance with the present invention.
[0019]FIGS. 9A through 9C are schematic diagrams illustrating the effect when the number of samples is changed for keeping the upper slopetracing waveform constant after a slopeinversion point is detected, in accordance with the present invention.
[0020]FIG. 10 is a schematic diagram illustrating a preferred embodiment wherein a slopetransition point is determined with an upper slopetracing waveform and thereby the signal waveform is partitioned.
[0021]FIG. 11 is a schematic diagram illustrating a signal waveform with partitioned sections using a lower slopetracing waveform.
[0022]FIG. 12 is a schematic diagram illustrating a waveform with partitioned sections using an upper slopetracing waveform.
[0023] Features of the present invention will be explained in detail with reference the accompanying drawings.
[0024] <Description of Terminology>
[0025] Slopeinversion point: a point of a sampled signal waveform where the waveform switches the polarity of its slope or the differential derivative either from the negative to the positive or from the positive to the negative.
[0026] Slopetransition point: a point where the slope of a signal waveform changes very rapidly. Here, the degree of the rapidness in the change of slope can be understood in a sense that the rate of slopechange at a certain point is larger than a predefined value (X %). As a preferred embodiment, X can be chosen as 50%.
[0027] Slopetracing waveform: a waveform that is chasing a signal waveform and is employed for efficiently determining the slopetransition point and the slopeinversion point. Two types of slopetracing waveform are disclosed as a preferred embodiment: one is a lower slopetracing waveform which traces a signal waveform upward from the beneath, and the other is an upper slopetracing waveform which traces a signal waveform downward from the top.
[0028] Preferably, both the upper and lower slopetracing waveforms can be simultaneously employed for partitioning the signal waveform. Depending upon a situation, either the upper slopetracing waveform or the lower slopetracing waveform can be chosen.
[0029] <Determination of a SlopeInversion Point and a SlopeTransition Point with a Lower SlopeTracing Waveform>
[0030]FIG. 1 is a schematic diagram illustrating a lower slopetracing waveform with a signal waveform for partitioning the signal waveform into sections in accordance with the present invention.
[0031] Referring to FIG. 1, the solid line 100 represents a signal waveform to be partitioned while the dotted line 120 denotes a curve of a lower slopetracing waveform.
[0032] The behavior of the lower slopetracing waveform, as shown in FIG. 1, can be classified as two cases depending upon the relative magnitude of the amplitude between the signal waveform an the slopetracing waveform.
[0033]FIG. 2 illustrates a case when the amplitude of the signal waveform is greater than that of the slopetracing waveform, while FIG. 3 corresponds to a case when the amplitude of the signal waveform is less than that of the sloptracing waveform.
[0034] Additionally, the dots • 13, 15, 17, 19 depicted in FIG. 1 represent the functional values of the samples or the amplitudes of sampling points under consideration.
[0035]FIG. 2 is a schematic diagram illustrating the behavior of a lower slopetracing waveform during the ascending stage where a signal waveform increases in accordance with the present invention.
[0036] Namely, FIG. 2 exhibits a case when the amplitude of a signal waveform is greater than that of a lower slopetracing waveform.
[0037] Referring to FIG. 2, the waveform represented by a solid line 100 is a signal waveform which needs to be partitioned, while the sampled dots • 13, 14, 15, 16 represent the functional values of samples or the amplitude at an instant under consideration prior to the application of the lower slopetracing waveform.
[0038] Moreover, the rectangles □ 1, 3, 5 denote the position of the lower slopetracing after the samples are produced, while the dotted lines 2, 4, 6 denote the height of the lower slopetracing waveform prior to sampling.
[0039] In case when the amplitude of the signal waveform 100 is greater than the height of the lower slopetracing waveform, the lower slopetracing waveform is updated with the signal waveform.
[0040] Let us choose the seventh sample 5 as a sample under consideration for the explanation purposes. In this case it should be noted that the amplitude of the signal waveform at the sample 5 is higher than the height 4 of the lower slopetracing waveform.
[0041] As a consequence, the height of the lower slopetracing waveform is updated with the amplitude 5 of the signal waveform, followed by a step of comparing the height 6 of the lower slopetracing waveform with the amplitude of a next sample 7.
[0042] Moreover, the height 4 of the lower slopetracing waveform prior to the current updating process has been updated with the amplitude 4 of the signal waveform because the amplitude 3 of the signal waveform was higher than the height of the slopetracing waveform. This updating procedure continues until a slopeinversion point 9 is detected as long as the amplitude of the signal waveform at a sample is greater than the height of the lower slopetracing waveform.
[0043]FIG. 3 is a schematic diagram illustrating the behavior of a lower slopetracing waveform during the descending stage posterior to the slopeinversion point in accordance with the present invention.
[0044] Referring to FIG. 3, we can understand how the lower slopetracing waveform behaves during the descending stage after the slopeinversion point 9 is detected.
[0045] When a slopeinversion point 9 is detected, the amplitude of the signal waveform at slopeinversion point 9 is compared with the height 8 of the lower slopetracing waveform. In this case, since the amplitude 9 of the signal waveform at slopeinversion point 9 is greater than the height 8 of the lower slopetracing waveform, the height 10 of the lower slopetracing waveform is updated with the amplitude 9 of the signal waveform.
[0046] Thereafter, since the amplitude of the next succeeding sample 11 is lower than the height 10 of the lower slopetracing waveform, the lower slopetracing waveform maintains its height 10 up to next sample 13.
[0047] The height 14 of the lower slopetracing waveform is maintained with the amplitude 10 of the signal waveform at the slopeinversion point from the inversion point 9 to the third sample 13 if the amplitude of the signal waveform at any of the aforementioned three successive samples exceeds the height of the lower slopetracing waveform, and the previously determined slopeinversion point is disregarded.
[0048] In the meanwhile, if the amplitude of the signal waveform at the third sample 13 as well as the two preceding samples, three of which follow the slopeinversion point 9 in a successive manner, does not go over the height 12, 14 of the lower slopetracing waveform, either the difference in the slope or the amplitude between the slopeinversion point 9 and the third sample 13 is calculated and divided by three in order to get an average slope per sample.
[0049] Now, the height of the lower slopetracing waveform is updated with a new value 16 by subtracting an amount from the old value 14 with the average slope per sample. Preferably, the average slope (or the amplitude) can be regarded as the difference of the height (or the amplitude) between the old lower slopetracing waveform 14 and the updated lower slopetracing waveform 16.
[0050] Now, for the next succeeding sample 15, the amplitude of the sample 15 is compared with the height 16 of the lower slopetracing waveform.
[0051] Since the height 18 of the lower slopetracing waveform exceeds the amplitude 15 of the signal waveform, the lower slopetracing waveform is updated with a new value 18 by subtracting an amount with the average slope per sample.
[0052] Additionally, since the height 18 of the lower slopetracing waveform is still higher than the amplitude 17 of the signal waveform at the next sample, the lower slopetracing waveform is updated again with a new value 20 by subtracting an amount with the average slope per sample.
[0053] In this case, the height of the lower slopetracing waveform updated is compared again with the amplitude 19 at the subsequent sample, and since the amplitude 19 of the signal waveform is still lower than the height of the lower slopetracing waveform, the height of the lower slopetracing waveform is reduced once again by the average slope per sample.
[0054] As a preferred embodiment, the average slope per sample can be updated with new number, which is defined as a difference between the maximum and the minimum, partitioned by three among the four successive samples after the slopeinversion point.
[0055] In other words, the difference between the third sample 13 and the sixth sample 19 is calculated and divided by three for a new average slope per sample. New average slope per sample is then employed for the calculation of the lower slopetracing waveform up to the next three samples 23.
[0056] This procedure continues until the amplitude of the signal waveform happens to exceed the height of the lower slopetracing waveform.
[0057] In the foregoing explanation, the numbers of samples were chosen to be three for the calculation of a new average slope per sample.
[0058] However, it does not have to be three, and the number of grouping samples can be changed in consideration of the computing speed.
[0059] More preferably, if a new average slope per sample, which has been calculated for the most recent three samples, is lower than the previous one by X percent, the average slope per sample can be updated as X percent of the previous average slope. In FIG. 3 is shown the case when X is equal to 50.
[0060] Referring to FIG. 3, the height 26 of the lower slopetracing waveform is calculated by subtracting the average slope, which is the difference between the maximum 19 and the minimum 23 partitioned by three, multiplied by three from the height 24 of the lower slopetracing waveform. In this case, since the average slope per sample was employed for the three successive samples, it should be updated with a new value by finding a difference between finding a difference between a maximum 23 and a minimum 25 and partitioning the difference by three.
[0061] In the meanwhile, the updated average slope per sample is a small value because the difference between a maximum 23 and a minimum 25 is not big.
[0062] Even if the height of the lower slopetracing waveform should be updated with a height 30, which is calculated by subtracting a new average slope, for the comparison with the next sample 27, the calculated average slope is neglected because it is smaller than so percent of the previous average slope. Therefore, the height of the lower slopetracing waveform is now updated with the lower value 28 by using a number of 50 percent of the previous average slope as an updated average slope.
[0063] In this case, if the sample of the signal waveform intersects with the lower slopetracing waveform, it has a special meaning.
[0064] Referring to FIG. 3 again, the sample 27 exhibits the crossover point with the lower slopetracing waveform. Now, the crossover point where the lower slopetracing waveform intersects with the signal waveform is defined as a slopetransition point, which implies a significant change in the average slope. Since the amplitude 27 of the signal waveform is higher than the height 28 of the lower slopetracing waveform after the intersection, the procedure depicted in FIG. 2 is now applied.
[0065] In other words, since the amplitude of the signal waveform at samples thereafter is larger than the height 28 of the lower slopetracing waveform, the lower slopetracing waveform is updated with the amplitude 34 of the signal waveform.
[0066] Referring to FIG. 3, it should be noted that the height 14 of a lower slopetracing waveform is maintained with the amplitude 9 at the slopeinversion point for the next three samples. If the samples of the signal waveform happen to exceed the lower slopetracing waveform while the lower slopetracing waveform is maintained, the procedure explained in FIG. 2 is then applied wherein the slopeinversion point is neglected and the signal waveform is assumed to increase.
[0067] Referring the FIG. 3, the lower slopetracing waveform is maintained for three samples after the detection of a slopeinversion point. However, the number of samples can be arbitrarily chosen with different effects correspondingly.
[0068] In other words, the two neighboring waveforms can be considered as a single waveform or two individual waveforms in accordance with the number of samples, which can result in the effect of a lowpass filter.
[0069]FIGS. 4A through 4C are schematic diagrams illustration the effect when the number of samples is varied wherein the lower slopetracing waveform is maintained posterior to the detection of slopeinversion point in accordance with the present invention
[0070] Referring to FIG. 4A, it should be noted that the amplitude ceases to increase at the slopeinversion point 37 and the slope switches to a positive number at the second slopeinversion point 39.
[0071] Referring to FIG. 4B, the height 42 of the lower slopetracing waveform is maintained for the three samples after the detection of a slopeinversion point 37.
[0072] In this case, the height 42 of the lower slopetracing waveform is maintained up to the third sample 41, and is then updated with a new height 44 by subtracting with an average slope. Since the intersection occurs between the signal waveform and the lower slopetracing waveform, a slopetransition point is determined and the interval between the first slopeinversion point 37 and a slopetransition point 43 is regarded as a single section.
[0073] Referring to FIG. 4C, it is noted the lower slopetracing waveform is maintained for four samples (or even more than four) after the detection of the maximum 37.
[0074] As long as the samples of the signal waveform do not exceed the height 46 of the lower slopetracing waveform after the detection of the first slopeinversion point 37 for four samples prior to the sample 45, samples prior to a sample 45, the procedure depicted in FIG. 2 is applied. In this case, the slopeinversion point 37 is neglected and the signal waveform is considered to increase continuously.
[0075] Through adjusting time (the number of samples) of maintaining the height of the lower slopetracing waveform after the detection of a slopeinversion point, two successive waveforms can be either separated as two or regarded as one.
[0076] The method of partitioning a signal waveform by employing a lower slopetracing waveform in accordance with the present invention performs the procedure disclosed to FIG. 2, FIG. 3, and FIG. 4, and the signal waveform is partitioned is consideration of a slopeinversion point and a slopetransition point.
[0077] The slopetransition point 9 depicted in FIG. 3 is a point where the lower slopetracing waveform intersects the samples of the signal waveform from the negative to the positive and the signal waveform is maintained beneath the level of the lower slopetracing waveform for three or K numbers of sample, and can be employed to determine the maximum of a signal waveform for certain interval.
[0078] The sample 27 of the signal waveform, as shown in FIG. 3, is a point where the signal waveform intersects with the lower slopetracing waveform from the negative to the positive, and can be regarded as a slopetransition point where the signal waveform ceases to decreases for partitioning the signal waveform.
[0079]FIG. 5 is a schematic diagram illustrating a method of determining a slopetransition point by employing a lower slopetracing waveform and preferred embodiments thereof. Referring to FIG. 5, it should be noted that the first bar 49 at the bottom means the slopeinversion point 9 of the signal waveform while the second bar 50 corresponds to the slopechange point. Further, it should be understood that the interval between those two bars should be regarded as a single interval. The amplitudes of those two bars 49, 50 are different form each other, which implies that the larger amplitude of the first bar 49 means a slopeinversion point while the smaller amplitude of the second bar 50 means a slopetransition point.
[0080] <Determination of a SlopeInversion Point and a SlopeChange Point by an Upper SlopeTracing Waveform>
[0081] In the following a detailed description about an upper slopetracing waveform will be given with reference to FIGS. 6 through 10 as another preferred embodiment in accordance with the present invention.
[0082] The behavior of the upper slopetracing waveform is quite similar to that of the aforementioned lower slopetracing waveform, while the difference between the two is that the upper slopetracing waveform approaches the signal waveform downward from the top.
[0083]FIG. 6 is a schematic diagram illustrating a waveformpartitioning method with an upper slopetracing waveform in accordance with the present invention. In FIG. 6 is shown a case when an upper slopetracing waveform 140 is applied to a signal waveform 100. Referring to FIG. 6, a solid line 10 represents a signal waveform that needs to be partitioned, while the dots • 52, 53, 59 represents a sampled value (or amplitude at an instant under consideration) of the signal waveform and a dotted line 140 exhibits the behavior of an upper slopetracing waveform.
[0084] Even if the upper slopetracing waveform 140 depicted by dotted line 140 looks like approaching the signal waveform from the beneath, it is called “upper” slopetracing waveform.
[0085] The behavior of the upper slopetracing waveform, as shown in FIG. 7, can be classified as two cases depending upon the relative magnitude of the amplitude between the signal waveform an the slopetracing waveform.
[0086]FIG. 7 illustrates a case when the amplitude of the signal waveform is greater than that of the upper slopetracing waveform, while FIG. 8 corresponds to a case when the amplitude of the signal waveform is less than that of the upper slopetracing waveform.
[0087]FIG. 7 is a schematic diagram illustrating the behavior of an upper slopetracing waveform during the ascending stage where a signal waveform increases in accordance with the present invention.
[0088] Namely, FIG. 7 exhibits a case when the amplitude of a signal waveform is greater than that of an upper slopetracing waveform.
[0089] Referring to FIG. 7, the waveform represented by a solid line 100 is a signal waveform which needs to be partitioned, while the sampled dots • 52, 53, 59, 16 represent the functional values of samples or the amplitude at an instant under consideration prior to the application of the upper slopetracing waveform.
[0090] Moreover, the rectangles □ 54, 56, 60 denote the position of the upper slopetracing after the samples are produced, while the dotted lines 140 denote the height of the upper slopetracing waveform prior to sampling.
[0091] A detailed description of an upper slopetracing waveform begins with a slopeinversion point 51 where the slope switches from the negative to the positive.
[0092] The upper slopetracing waveform 140, which is updated with the slopeinversion point 51, maintains its height 54 up to the third sample 53.
[0093] If the amplitude of the signal waveform happens to be lower than the height of the upper slopetracing waveform on the way to the third sample 53, the upper slopetracing waveform is updated by a sample whose amplitude is lower than that of the upper slopetracing waveform and the previously defined slopeinversion point is discarded.
[0094] However, if the signal waveform does not cross the upper slopetracing waveform to go down below up until the third sample 53 from the slopeinversion point 51, the slopeinversion point is confirmed.
[0095] Further, the slope difference (or the amplitude difference) between the slopeinversion point 51 and the third sample 53 is calculated and divided by three in order to get an average slope per sample.
[0096] Now, the height of the upper slopetracing waveform is updated with a new value 56 by adding the average slope per sample to the height of the upper slopetracing waveform.
[0097] Now, the process of adding the average slope per sample to the upper slopetracing waveform is kept on for the next samples after the average slope per sample is determined.
[0098] In the meanwhile, the amplitude of the signal waveform does not go below the height of the upper slopetracing waveform for the next three samples, a new average slope per sample is updated and the upper slopetracing waveform is updated by adding the average slopeper sample to the old upper slopetracing waveform, which continues until the amplitude of a signal waveform becomes lower than the height of the upper slopetracing waveform.
[0099] In FIG. 7 is shown a case where the height 54 of the upper slopetracing waveform is maintained from the slopeinversion point 51 to the third sample 53 and the height 60 of the upper slopetracing waveform is updated by adding the average slope per sample to the upper slopetracing waveform.
[0100] In this case, the average slope per sample is updated again and added to the upper slopetracing waveform on the way up to the next three samples 61.
[0101] In the meanwhile, the amplitude 65 of the signal waveform happens to be lower than that 66 of the upper slopetracing waveform, a slopetransition point is determined and the upper slopetracing waveform is updated with the amplitude the transition point.
[0102] As a preferred embodiment in accordance with the present invention, a new average slope per sample, which is calculated for every third sample, can be compared with the 50% value of the previously utilized average slope per sample.
[0103] If a new average slope per sample is lower than the previous one by more than 50%, the average slope per sample should be updated with a new number, which is 50% of the previous average slope per sample.
[0104]FIG. 8 is a schematic diagram illustrating a behavior of the upper slopetracing waveform during the descending stage posterior to the slopeinversion pint in accordance with the present invention.
[0105] Referring to FIG. 8, the second part of the signal waveform demonstrates the behavior of the upper slopetracing waveform when the amplitude of the signal waveform is lower than that of the slopetracing waveform.
[0106] The first part of the waveform shown in FIG. 8 corresponds to the behavior illustrated in FIG. 7 while the second part illustrates the case when the amplitude of the signal waveform becomes lower than that of upper slopetracing waveform.
[0107] Referring to FIG. 8, the solid line 100 denotes the signal waveform to be partitioned whereas the dotted line 140 denotes the upper slopetracing waveform and the dots * 53, 59 imply the sampled value of the signal waveform, the rectangles □ 56, 60 denoting the height of each sample of the upper slopetracing waveform.
[0108] The upper slopetracing waveform is updated either with the previous sample or with the current sample depending upon the comparison in the amplitude.
[0109] Since the slopetransition point 65 lies below the upper slopetracing waveform, the upper slopetracing waveform is updated with a sample 68 and thereafter the height 70 is compared with the amplitude of the next sample 71.
[0110] In this case, since the height 70 of the upper slopetracing waveform is larger than that of a sample 71, the upper slopetracing waveform is updated with a signal sample 71 and maintains the height 72 in order to compared with next sample 73.
[0111] This process continues as long as the amplitude of a signal waveform lines above the upper slopetracing waveform as shown in FIG. 7.
[0112] In the meanwhile, if the height of samples of a signal waveform lies below the upper slopetracing waveform, on the contrary to the case shown in FIG. 7 wherein the height 54 of the upper slopetracing waveform is maintained for the next three samples posterior to the slopeinversion point 51, the slopeinversion point is then discarded and the process illustrated in FIG. 8 is performed.
[0113] However, if the amplitude of a signal waveform happens to be lower than the height of the upper slopetracing waveform during the ascending stage where the upper slopetracing waveform increases with the average slope per sample after the period of maintaining the height for the three samples, the slopeinversion point is confirmed.
[0114] Although the number of samples where the amplitude of the upper slopetracing waveform is maintained is three, one can choose the number as another preferred embodiment with a little bit different effect.
[0115] Depending upon the number of samples for maintaining the height of the slopetracing waveform, two neighboring waveform can be considered either as one or two separate one, and thereby the effect of a lowpass filter can be expected.
[0116]FIGS. 9A through 9C are schematic diagrams illustrating the dependence of the number of samples for maintaining the height of the slopetracing waveform after the detection of the slopeinversion point.
[0117] Referring to FIG. 9A, a signal waveform increases'"'"' from the first slopeinversion point 87 up until the second slopeinversion point 89 after which the waveform decreases.
[0118] Referring to FIG. 9B, the height of the upper slopetracing waveform is maintained with the amplitude 92 of the third sample after the first slopeinversion point 87 is reached. In this case, the height 94 of the upper slopetracing waveform is updated by adding the average slope per sample, which is the average value of the three samples, to the height of the upper slopetracing waveform.
[0119] Now, the next sample 93 is compared with the height 94 of the upper slopetracing waveform. Since the signal waveform crosses down the upper slopetracing waveform and the amplitude 93 lies below the height 94 of the slopetracing waveform, the sample 93 is detected as a slopetransition point and separated from the subsequent waveform.
[0120] Referring to FIG. 9C, the height of the upper slopetracing waveform is maintained up to the fourth sample 95 after the first slopeinversion point. In this case, the slopeinversion point 87 is discarded and the waveform is considered as decreasing because the amplitude 95 of the signal waveform becomes lower than that 96 of the slopetracing waveform while the height of the slopetracing waveform is kept constant.
[0121] Consequently, the up and downs of a signal waveform can be either separated or united depending upon how many samples are chosen form maintaining the height of the upper slopetracing waveform with the amplitude of the slopeinversion point.
[0122] The number N of samples for maintaining the height of the upper slopetracing waveform can be chosen under the consideration of the characteristic and/or the noise performance of the waveform, and further determined automatically.
[0123]FIG. 10 is a schematic diagram illustrating a preferred embodiment for determining a slopetransition point and partitioning the waveform.
[0124] The first bar 99 shown in FIG. 10 implies the first slopeinversion point 51, while the second bar 102 with low height depicts a slopetransition point. The interval between those bars is considered as a single section.
[0125] In addition, the third bar 101 implies the second slopeinversion point of the signal waveform.
[0126] The method of partitioning a signal waveform with an upper slopetracing waveform disclosed in the present invention performs the procedure illustrated in FIGS. 7, 8, and 9, and utilizes the slopeinversion point and the slopetransition point for partitioning the waveform.
[0127] The slopeinversion point 51, as shown in FIG. 7, is a point where the upper slopetracing waveform starts to cross down the signal waveform and the height of the upper slopetracing waveform of the upper slopetracing waveform maintains its height for the next three or K samples, which is used for determining the minimum of a waveform for a particular section.
[0128] The sample 65 of the signal waveform depicted in FIG. 8 is a point where the signal waveform starts to go below the height of the upper slopetracing waveform, which is considered as an ending point of increase and therefore a slopetransition point for the application of partitioning a waveform.
[0129] <SectionPartitioning Method of a Waveform>
[0130] The waveform partitioning method disclosed in the present invention is that a slopeinversion point is determined wherein the slope of a signal waveform changes its value from the positive and the negative and the amplitudes of the next three or N numbers of signal samples are lower than that of a point where the slope changes its value from the negative to the positive, while slopetransition point is determined by finding a point wherein a lower slopetracing waveform keeps decreasing with an average slope per sample and finally becomes smaller than a sample of a signal waveform, and thereby those points are used for partitioning points as a reference.
[0131] The maximum sample 9 shown in FIG. 3 is a sample where a lower slopetracing waveform has been smaller than the amplitude of a signal waveform and now starts to exceed, which determines a slopeinversion point where in the slope of a signal waveform changes from the positive to the negative. The sample 27 depicted in FIG. 3 is a point where the amplitude of a signal waveform has been smaller than the height of a lower slopetracing waveform and then starts to exceed, which determines a slopetransition point by considering it as an ending point of decrease.
[0132]FIG. 5 demonstrates an example for the determination of slopetransition point by employing a lower slopetracing waveform. The first bar 49, shown in FIG. 5, represents a slopeinversion point which is determined under the condition that the lower slopetracing waveform maintains its height with the maximum 9 during three sampling instants, while the second bar 50 represents an instant when the height 28, which has been descending with an average slope per sample, becomes to be lower than a sample 27 and is regarded as a point where the slope changes very abruptly.
[0133] Thereafter, the slopeinversion point 51 of FIG. 7, at which the slope of the upper slopetracing waveform changes from the negative to the positive and of which the slope is lower than those of the next three or N samples with the slopetransition point at which the upper slopetracing waveform increases with an average slope and becomes larger than the amplitude of the signal waveform is a point where the amplitude of the upper slopetracing waveform becomes lower than that of the signal waveform. Since the amplitude of the upper slopetracing waveform is maintained during the next three samples, the slopeinversion point is now fixed. Further, the slopetransition point is fixed because the upper slopetracing waveform increases with an average slope and then the height of the upper slopetracing waveform becomes higher than that of the signal waveform. Thereby, the signal waveform is separated from the next signal interval.
[0134]FIG. 10 is a schematic diagram illustrating an embodiment of determining a slopetransition point by employing an upper slopetracing waveform.
[0135] The first bar 99 of FIG. 10 denotes a slopeinversion point 51, which has been determined according to the condition that the amplitude of the upper slopetracing waveform maintains its amplitude during the next three samples and thereby divides the signal waveform. The second bar 100 implies a slopetransition point where the amplitude 66 of the upper slopetracing waveform becomes lower again than the samples 65, and thereby divides the signal waveform.
[0136]FIGS. 5 and 10 exhibits how to divide the signal waveform by employing the slopeinversion point and the slopetransition point. The bars shown in each figure denotes the partitioned point for the signal waveform.
[0137] The bars 49, 50 pointing to the positive direction denote the partitioned points, which are determined by a lower slopetracing waveform, while the bars 99, 100, 101 pointing to the negative direction denote the partitioned points which are determined by an upper slopetracing waveform.
[0138] The tall bar 49 of FIG. 5 denotes a slopeinversion point where the slope detected by the lower slopetracing waveform changes from the positive to the negative, while the other bar 50 denotes a slopetransition point, which is detected by a lower slopetracing waveform.
[0139] The tall bars 99, 101 denote the slope10 inversion points where the slope, detected by an upper slopetracing waveform, changes from the negative to the positive, while the other bar 100 denotes a slopetransition point detected by an upper slopetracing waveform.
[0140] The waveform partitioning method as set forth in the foregoing upper and lower slopetracing waveforms has been applied in such a way that the time axis of the slopetracing waveform increases.
[0141] This can be utilized either for the realtime recognition of the signal waveform or for the stored waveform.
[0142] In case when the recognition of a certain waveform from the stored signal waveform is needed, the upper and lower slopetracing waveforms can be applied in the reverse time axis. In other words, the stored waveform can be partitioned in accordance with the present invention by applying the slopetracing waveforms from the final toward the initial in the reverse time axis. In order to divide to signal waveform more accurately, the aforementioned slopetracing waveform can be applied both directions of the time axis. In other words, both the upper slopetraction waveform and the lower slopetracing waveform are utilized in a forward time axis and thereafter in a reverse time axis.
[0143] More preferably, the direction in time axis for applying the slopetracing waveform can be alternated, if need. Namely, for instance, one can apply the upper and lower slopetracing waveforms in the positive direction of time axis for certain period of samples. Now, when either a slopeinversion point or a slopetransition point is reached, the direction of time axis for applying the slopetracing waveforms can be switched until either a new slopetransition point or a slopeinversion point is detected. In this case, if the time for applying the slopetracing waveforms in the reverse direction is shorter than the sampling period, it can be applied in real time.
[0144] In the above explanation, the waveform partitioning method by upper and lower slopetracing waveforms defines the spacing between the slopeinversion point and the neighboring slopetransition point as a single interval. More preferably, however, the interval between the left and right slopetransition points with respect to a slopeinversion point as a center can be regarded as a single point. Although this can be applied to the slopeinversion point and the slopetransition point determined either by an upper slopetracing waveform or by a lower slopetracing waveform in a separate manner, in can be also applied to a slopeinversion point and a slopetransition point mixed from the two slopetracing waveforms.
[0145] The interval partitioned by the lower slopetracing waveform and the upper slopetracing waveform, as shown in FIGS. 5 and 10, can be amended as the following, if needed.
[0146]FIG. 11 is a schematic diagram illustrating a partitioned waveform determined by a lower slopetracing waveform. The first bar 171 and the last bar 173 depicted in FIG. 11 correspond to a slopetransition point determined by a lower slopetracing waveform, while the third bar 172 corresponds to a slopeinversion point determined by a lower slopetracing waveform.
[0147] It is noted that there is a significant difference in the amplitude 177, 178 of the signal waveform between at the left slopetransition point 171 and at the right slopetransition point 173 of the slopeinversion point 172 that is determined by the slopetracing waveform.
[0148] In this case, if the difference in the amplitude between at the right slopetransition point 173 and at the left slopetransition point 171 exists by more than Y percent, the slopetransition point 171, 173, which have been detected by a lower slopetracing waveform, are still used.
[0149] In the opposite case, as shown in FIG. 11, the position of the slopetransition point is adjusted and the partitioned interval is modified.
[0150] As a preferred embodiment in accordance with the invention, a slopetransition point 173 whose amplitude 178 is close to that 170 of the signal waveform at the slopeinversion point 172 is selected. Moreover, a slopetransition point 180 for adjusting a sampling instant can be determined by finding a sample 179 whose amplitude is most close to the that 178 of the slopeinversion point 173 in order to amend the interval partitioned by the lower slopetracing waveform.
[0151] Preferably, Y can be chosen in the numbers between 30 and 90 according to the characteristics of the signal waveform. Especially for the physiological signal of a living body, 70% can be chosen for Y.
[0152]FIG. 12 is a schematic diagram illustrating a waveform partitioned with points determined by an upper slopetracing waveform.
[0153] The first bar 181 and the last bar 183 of FIG. 12 represent slopetransition points from the upper slopetracing waveform, while the second bar 182 is a slopeinversion point. There is a significant difference in the amplitude 187, 189 between the left slopetransition point 181 and the right slopetransition point 183 with respect to the slopeinversion point 182 from the upper slopetracing waveform.
[0154] In this case, the difference between the amplitude 180 of the signal waveform at the slopeinversion point 182 and the amplitudes 187, 189 at the slopetransition points is calculated, respectively.
[0155] Furthermore, if the ratio between the larger amplitude and the smaller amplitude is more than Y %, the slopetransition points 181, 183 determined by the upper slopetracing waveform should continue to be utilized.
[0156] However, if the opposite is true, the position of the slopetransition points should be adjusted as shown is FIG. 12 in order to amend the partitioned interval.
[0157] The interval determined from the lower slopetracing waveform can be amended by selecting a slopetransition point 181 having an amplitude 187 that is close to the amplitude 180 of the signal waveform at the slopeinversion point, and defining a sampling instant as a slopetransition point 185 wherein the amplitude 188 of the opposite signal waveform is close to the amplitude 187 of a chosen slopetransition point 181.
[0158] In the meanwhile, any number between 30 and 90 can be chosen for Y. Preferably, 70 can be used as Y for the physiology signal. The amendment explained in the foregoing can be selectively applied, if needed.
[0159] <Characterization of Partitioned Waveform>
[0160] In the followings, a detailed description will be made for characterizing the partitioning points of the signal waveform which has been determined from the slopeinversion point and the slopetransition point with upper and lower slopetracing waveforms.
[0161] As a first embodiment in accordance with the present invention, and interval can be characterized by indication the area at the end of the interval, which is obtained from an integration of the waveform between the partitioning points.
[0162] The area of the signal waveform at each interval is obtained by subtraction the sampled values in the interval from the amplitude of the signal waveform at a slopetransition point, followed by summing the subtracted values.
[0163] In addition, if the interval between the right and the left slopetransition points with a center at the slopeinversion point is defined as a single point, either the sum or the of the pair first part and the second part calculated from the above can be utilized for the characterization of the waveform.
[0164] As a second embodiment in accordance with the invention, the amplitudes in the interval that is partitioned from the partitioning points can be utilized for the characterization. Here, the amplitude is defined as the subtraction of the amplitude at a slopetransition point from the amplitude at a slopeinversion point.
[0165] In addition, in case when the interval of the signal waveform is defined as an interval between the left slopetransition point and the right slopetransition point with a center at a slopeinversion point, the sum of the amplitudes of the first part and the second part can be utilized as well as the pair of the amplitudes.
[0166] As a third preferred embodiment in accordance with the present invention, the time interval partitioned by the slopepartitioning points is calculated and is characterized. The time interval is defined as a time difference between the beginnings to the end of the interval.
[0167] Additionally, when a signal waveform interval is defined as spacing between the left and the right slopetransition point with a center at an slopeinversion point, either the sum or the pair themselves of the first part and the second part can be utilized for the characterization of the interval.
[0168] The abovementioned three embodiments can be applied either separately or simultaneously. In other words, either the area or the amplitude calculated in accordance with the present invention can further reduce the characteristics of the signal waveform by partitioning or multiplying in time interval.
[0169] Although the invention has been illustrated and described with respect to exemplary embodiments thereof, it should be understood by those skilled in the art that various other changes, omissions and additions may be made therein and thereto, without departing from the spirit and scope of the present invention.
[0170] Therefore, the present invention should not be understood as limited to the specific embodiment set forth above but to include all possible embodiments which can be embodies within a scope encompassed and equivalents thereof with respect to the feature set forth in the appended claims.
[0171] As explained in the foregoing, the present invention can be useful for partitioning the signal waveform in such a way that the partitioned waveform is suitable to the recognition of a signal with the upper and lower slopetracing waveform.
[0172] More particularly, the waveform partitioning method in accordance with the present invention can be employed for the physiology signal of the medical instrument.