Heart rate signal motion artifact elimination method for thermal endurance monitoring

Abstract

The invention relates to the technical field of electronic digital data processing, in particular to a heart rate signal motion artifact elimination method for thermal endurance monitoring, which comprises the following steps of: acquiring temperature data and acceleration data of a monitored object and a PPG heart rate signal of a blood vessel in a thermal endurance monitoring process, and determining different types of actions according to the acceleration data; the method comprises the following steps: acquiring PPG heart rate signals corresponding to different types of actions, decomposing segments of the PPG heart rate signals corresponding to the different types of actions, determining each IMF component corresponding to each action, determining the influence condition of each IMF component corresponding to each action on motion artifacts according to each IMF component corresponding to each action and temperature data, and determining the motion artifact of the motion artifacts according to the influence condition of each IMF component corresponding to each action. According to the method, signal reconstruction is carried out according to the influence condition of each IMF component corresponding to each action on the motion artifact, the target PPG heart rate signal without the motion artifact is obtained, the condition that the heart rate signal is distorted due to the motion artifact is avoided, and the accuracy of heart rate measurement is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of electronic digital data processing, and particularly relates to a method for eliminating motion artifacts in heart rate signals for heat endurance monitoring. Background Art

[0002] When performing non-contact heart rate signal monitoring, PPG (Photo Plethysmo Graphy) measures heart rate by detecting blood flow changes. As a non-invasive optical technology, PPG emits light of a specific wavelength (such as red, green, or infrared) onto the skin. When the light irradiates blood vessels, part of the light energy is absorbed by the blood and part is reflected back to the sensor. The DC component of the PPG signal reflects the average blood volume of the blood and tissues, while the AC component reflects the periodic blood volume changes (heart rate) of the heart.

[0003] Usually, during the process of heat endurance monitoring, since the monitored object is in a moving state, it will cause changes in the skin contact pressure between the monitoring device and the monitored object. At the same time, movement will also cause rapid changes in blood flow velocity, resulting in obvious motion artifacts in the acquired signal data, thus causing distortion of the measured PPG heart rate signal and affecting the measurement accuracy. Summary of the Invention

[0004] In order to solve the above technical problems, the purpose of the present invention is to provide a method for eliminating motion artifacts in heart rate signals for heat endurance monitoring, and the specific technical solutions adopted are as follows: In the first aspect, an embodiment of the present application provides a method for eliminating motion artifacts in heart rate signals for heat endurance monitoring, including: During the heat endurance monitoring process, obtaining the temperature data, acceleration data of the monitored object, and the PPG heart rate signal of the blood vessels; Determining each action of different types according to the acceleration data, and decomposing the segments of the PPG heart rate signal corresponding to each action of different types to determine each IMF component corresponding to each action; Determining the influence of each IMF component corresponding to each action on motion artifacts according to each IMF component corresponding to each action and the temperature data; Performing signal reconstruction according to the influence of each IMF component corresponding to each action on motion artifacts to obtain the target PPG heart rate signal with motion artifacts eliminated.

[0005] In an implementation manner, the determining each action of different types according to the acceleration data includes: Perform motion decomposition on the acceleration data to obtain motion segments of several actions, and perform normalization processing on each of the motion segments respectively; Determine the DTW distances between each of the motion segments after normalization processing, and cluster each of the motion segments according to the DTW distances to determine each action of different types.

[0006] In one implementation manner, determining the influence of each IMF component corresponding to each action on motion artifacts according to each IMF component corresponding to each action and the temperature data includes: Match each IMF component corresponding to each action through DTW, and respectively determine several IMF component matching pairs between actions of the same type; Determine the action difference situation between actions of the same type according to several of the IMF component matching pairs and the acceleration data; Determine the change deviation situation of each IMF component of each action according to the temperature data and the action difference situation, and determine the influence of each IMF component corresponding to each action on motion artifacts according to the change deviation situation of each IMF component of each action.

[0007] In one implementation manner, determining the action difference situation between actions of the same type according to several of the IMF component matching pairs and the acceleration data includes: According to several of the IMF component matching pairs, determine the first difference situation between the actions of each IMF component matching pair under each IMF component; Determine the acceleration segment corresponding to each action from the acceleration data, match the acceleration segments corresponding to each action through DTW, respectively determine several acceleration matching pairs between actions of the same type, and determine the second difference situation of the acceleration between the actions of each acceleration matching pair according to several acceleration matching pairs between actions of the same type; Wherein, the action difference situation between actions of the same type includes the first difference situation and the second difference situation.

[0008] In one implementation manner, determining the first difference situation between the actions of each IMF component matching pair under each IMF component according to several of the IMF component matching pairs includes: Respectively determine a first action and a second action from each type of action, and determine several candidate IMF component matching pairs corresponding to the first action and the second action according to several of the IMF component matching pairs; Determine a first absolute value of the difference in slopes between the IMF components in each of the candidate IMF component matching pairs; Respectively determine, in each of the candidate IMF component matching pairs, a first amplitude of the IMF component matching the IMF component corresponding to the first action and a second amplitude of the IMF component matching the IMF component corresponding to the second action, and respectively determine a second absolute value of the difference between the first amplitude and the corresponding second amplitude; Based on the first absolute value, the second absolute value, and the number of candidate IMF component matching pairs, determine, for each IMF component in each type of action, a first difference situation between the first action and the second action, and return to the step of respectively determining the first action and the second action from each type of action until the first difference situation between the actions of each IMF component matching pair is determined for each IMF component.

[0009] In one implementation manner, the determining, according to a plurality of acceleration matching pairs between actions of the same type, a second difference situation of accelerations between the actions of each of the acceleration matching pairs includes: Respectively determine a first action and a second action from each type of action, and determine a plurality of candidate acceleration matching pairs corresponding to the first action and the second action according to the plurality of acceleration matching pairs between actions of the same type; Determine a third absolute value of the difference in slopes between acceleration segments in each of the candidate acceleration matching pairs; Respectively determine, in each of the candidate acceleration matching pairs, a third amplitude of the acceleration segment matching the acceleration segment corresponding to the first action and a fourth amplitude of the acceleration segment matching the acceleration segment corresponding to the second action, and respectively determine a fourth absolute value of the difference between the third amplitude and the corresponding fourth amplitude; Based on the third absolute value, the fourth absolute value, and the number of candidate acceleration matching pairs, determine, for each type of action, a second difference situation between the first action and the second action, and return to the step of respectively determining the first action and the second action from each type of action until the second difference situation of accelerations between the actions of each acceleration matching pair is determined.

[0010] In one implementation manner, the determining, according to the temperature data and the action difference situation, a change deviation situation of each IMF component of each action, and determining, according to the change deviation situation of each IMF component of each action, an influence situation of each IMF component corresponding to each action on motion artifacts includes: Based on the temperature data, determine the temperature DTW matching distance between actions of the same type, and respectively determine the temperature difference situation between actions of the same type according to the natural exponential function and the temperature DTW matching distance; Respectively determine the ratio of the first difference situation to the second difference situation, and determine the corresponding variance according to each of the ratios; Perform a summation process according to the ratio, the temperature difference situation, and the number of actions in each type of action to obtain a summation result, and obtain the change deviation situation of each IMF component of each action according to the product of the reciprocal of the variance and the summation result; According to the change deviation situation of each IMF component of each action, calculate the difference in the change deviation situation between two adjacent actions, and determine the influence situation of each IMF component corresponding to each action on motion artifacts.

[0011] In one implementation, the signal reconstruction based on the influence situation of each IMF component corresponding to each action to obtain the target PPG heart rate signal for eliminating motion artifacts includes: Determine the component weight corresponding to each IMF component according to the influence situation of each IMF component corresponding to each action on motion artifacts; Respectively determine the amplitude gap between the corresponding IMF components of two adjacent actions, and respectively determine the reconstruction weight of each IMF component of each action according to the amplitude gap and the component weight corresponding to each IMF component; Perform signal reconstruction according to the reconstruction weight of each IMF component of each action to obtain the target PPG heart rate signal for eliminating motion artifacts.

[0012] In one implementation, the determining the reconstruction weight of each IMF component of each action according to the amplitude gap and the component weight corresponding to each IMF component respectively includes: Respectively determine the fluctuation weight of each IMF component according to the natural exponential function and the opposite number of the amplitude gap; Respectively determine the reconstruction weight of each IMF component of each action according to the product of the fluctuation weight of each IMF component and the component weight.

[0013] In one implementation, the performing signal reconstruction according to the reconstruction weight of each IMF component of each action to obtain the target PPG heart rate signal for eliminating motion artifacts includes: Perform a weighted summation of the corresponding IMF components of each action according to the reconstruction weight of each IMF component of each action to obtain the target PPG heart rate signal for eliminating motion artifacts.

[0014] The present invention has the following beneficial effects: During the thermal endurance monitoring process, temperature data, acceleration data, and the PPG heart rate signal of blood vessels of the monitored object are acquired. Different types of actions are determined based on the acceleration data, and segments of the PPG heart rate signal corresponding to different types of actions are decomposed to determine each IMF component corresponding to each action. Based on each IMF component corresponding to each action and the temperature data, the influence of each IMF component corresponding to each action on motion artifacts is determined. Signal reconstruction is performed according to the influence of each IMF component corresponding to each action on motion artifacts to obtain the target PPG heart rate signal with motion artifacts eliminated, avoiding the situation where the heart rate signal is distorted due to motion artifacts, which is beneficial to improving the accuracy of heart rate measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions and advantages in the embodiments of the present invention or the prior art, the drawings required for use in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0016] Figure 1 It is a schematic flowchart of the steps of a method for eliminating motion artifacts of a heart rate signal for thermal endurance monitoring provided by an embodiment of the present invention; Figure 2 It is a schematic diagram of acceleration data provided by an embodiment of the present invention; Figure 3 It is a schematic diagram of the PPG heart rate signal provided by an embodiment of the present invention; Figure 4 It is a schematic diagram of temperature data provided by an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0017] In order to further elaborate on the technical means and effects adopted by the present invention to achieve the predetermined invention purpose, the following combines the drawings and preferred embodiments to describe in detail a method for eliminating motion artifacts of a heart rate signal for thermal endurance monitoring proposed according to the present invention, its specific implementation manner, structure, characteristics, and effects. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. In addition, the specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs.

[0019] It should be noted that the "exemplary" in the embodiments of the present application refers to examples listed for convenience of description, and in other embodiments, it is not limited to the listed examples.

[0020] The following specifically describes the specific solution of a method for eliminating motion artifacts of a PPG heart rate signal for thermal endurance monitoring provided by the present invention with reference to the accompanying drawings.

[0021] Please refer to Figure 1 , which shows a flowchart of a method for eliminating motion artifacts of a PPG heart rate signal for thermal endurance monitoring provided by an embodiment of the present invention. The method for eliminating motion artifacts of a PPG heart rate signal for thermal endurance monitoring may at least include steps S100 - S400: S100. During the thermal endurance monitoring process, obtain the temperature data, acceleration data, and PPG heart rate signal of blood vessels of the monitored object.

[0022] S200. Determine each action of different types according to the acceleration data, decompose the segments of the PPG heart rate signal corresponding to each action of different types, and determine each IMF component corresponding to each action.

[0023] S300. Determine the influence of each IMF component corresponding to each action on motion artifacts according to each IMF component corresponding to each action and the temperature data.

[0024] S400. Perform signal reconstruction according to the influence of each IMF component corresponding to each action on motion artifacts to obtain the target PPG heart rate signal with motion artifacts eliminated.

[0025] The technical solution of the embodiments of the present application, by obtaining the temperature data, acceleration data, and PPG heart rate signal of blood vessels of the monitored object during the thermal endurance monitoring process, determining each action of different types according to the acceleration data, decomposing the segments of the PPG heart rate signal corresponding to each action of different types, determining each IMF component corresponding to each action, determining the influence of each IMF component corresponding to each action on motion artifacts according to each IMF component corresponding to each action and the temperature data, and performing signal reconstruction according to the influence of each IMF component corresponding to each action on motion artifacts to obtain the target PPG heart rate signal with motion artifacts eliminated, avoids the situation that the heart rate signal is distorted due to motion artifacts, and is beneficial to improving the accuracy of heart rate measurement.

[0026] Such as Figure 2 , Figure 3 and Figure 4As shown, in one embodiment, during the thermal endurance monitoring, relevant data of the monitored object can be obtained by using a monitoring device. For example, by placing a portable ear-hanging device around the ear of the monitored object, the PPG heart rate signal and temperature data of the blood vessels of the monitored object can be collected, as Figure 3 shown. Figure 3 As shown in the schematic diagram of the PPG heart rate signal, after amplifying a section of the PPG heart rate signal 31, one cardiac cycle 32 can be seen (the ordinate of the PPG heart rate signal is dimensionless and is a relative value), reflecting the ratio of the light intensity change received by the photoelectric sensor), as Figure 4 shown. Figure 4 As shown in the schematic diagram of the temperature data, it can be seen from the temperature data that the temperature (body temperature) changes corresponding to different times, and the change of the set point can be seen, as well as which time period corresponds to information such as shivering, vasoconstriction, sweating, vasodilation, etc.; at the same time, as Figure 2 shown. Figure 2 As shown in the schematic diagram of the acceleration data, a motion module with an acceleration sensor and a gyroscope can be used to obtain the acceleration data of the monitored object. Different monitored objects may have different acceleration data, that is, the respective accelerations corresponding to different times. It should be noted that the monitoring time length is adjusted based on the actual situation, and the monitoring device can use existing devices and modules, which will not be described in detail.

[0027] It should be noted that during the thermal endurance monitoring, when obtaining the PPG heart rate signal of the blood vessels for heart rate signal monitoring, due to the movement of the monitored object, the movement will cause certain motion artifacts in the obtained PPG heart rate signal. When removing the artifacts, in fact, the actions of the monitored object can be decomposed, and the PPG heart rate signals corresponding to the same actions can be analyzed. Although the motion artifacts of the PPG heart rate signals corresponding to the same actions may be affected by temperature and the frequency of heart rate beats during acquisition, the PPG heart rate signals corresponding to the same actions have certain rules. Therefore, in this application, the EMD decomposition method is used for analysis to determine the influence of different actions on motion artifacts.

[0028] In the embodiment of this application, based on the principle that different actions will cause different interferences of motion artifacts, quantitative analysis is performed, and action classification is performed based on the acceleration data.

[0029] In one embodiment, in step S200: First, the acceleration data can be decomposed into motion segments of several actions by using existing methods. Each motion segment has a certain number of accelerations (values), and then each motion segment is normalized respectively to avoid the interference caused by the motion intensity.

[0030] Secondly, determine the DTW distance between each motion segment after normalization processing. DTW (Dynamic Time Warping) is an algorithm used to measure the similarity between two time series. Then, use the DTW distance as the distance during clustering, and cluster each motion segment according to the DTW distance to determine different types and each action within different types.

[0031] Then, through the EMD (Empirical Mode Decomposition) decomposition method, decompose the segments of the PPG heart rate signals corresponding to each action of different types, and determine each IMF (Intrinsic Mode Function) component corresponding to each action. Each IMF component is equivalent to a part of the signal of the decomposed PPG heart rate signal.

[0032] In the embodiments of the present application, the obtained PPG heart rate signal itself is composed of motion artifacts, noise, and the heart rate part, and it is not easy to distinguish them because they are superimposed on each other. Therefore, the components are operated by means of EMD decomposition. At the same time, by analyzing the different IMF components after decomposition, the influence of temperature can be reduced to a certain extent (the temperature affects the trend of the IMF components). Among them, when analyzing the IMF components subsequently, the IMF components in the high-frequency region can be removed because the heart rate is generally distributed in the middle-frequency region, and the low-frequency region is generally caused by the changes in the respiration and body temperature of the monitored object (changes in the trend). Therefore, when analyzing the IMF components subsequently, it refers to analyzing the middle-frequency region and the part of the low-frequency region of the IMF components.

[0033] It should be noted that the above division of the same action type is related to the situation of motion artifact generation and the motion action. There is a certain connection between the obtained acceleration data and the PPG heart rate signal under the same action, and the stability and noise influence of the PPG heart rate signal under the same acceleration can be analyzed; in addition, since the influence of motion artifacts is also related to the temperature of the monitored object, and the intensity of motion artifacts will increase after the temperature rises, the influence of different temperatures under the same action needs to be considered when performing subsequent quantitative analysis.

[0034] In one implementation, step S300 includes steps S301 - S303: S301. Match each IMF component corresponding to each action through DTW, and respectively determine several IMF component matching pairs between actions of the same type.

[0035] Optionally, each IMF component corresponding to each action is matched through DTW, and several IMF component matching pairs between actions of the same type are respectively determined; among them, each IMF component matching pair includes two IMF components. If there is a one-to-many matching situation in DTW, the IMF component with the closest DTW distance is used as the finally matched IMF component, so as to achieve one-to-one matching and determine several IMF component matching pairs.

[0036] S302. Determine the action difference situation between actions of the same type according to several IMF component matching pairs and acceleration data.

[0037] Optionally, the action difference situation between actions of the same type includes a first difference situation and a second difference situation. S302 includes Step 1 and Step 2: Step 1. According to several IMF component matching pairs, determine the first difference situation between the actions of each IMF component matching pair under each IMF component.

[0038] First, determine a first action (such as the th action) and a second action (such as the th action) respectively from each type of action. That is, the first action and the second action belong to the same type of action. For each type of action, the first action and the second action are extracted, and according to several IMF component matching pairs, determine several candidate IMF component matching pairs corresponding to the first action and the second action, that is, all the IMF component matching pairs in which the IMF component of the th action is matched with the IMF component of the th action.

[0039] Secondly, determine the first absolute value of the difference in slope between the IMF components in each candidate IMF component matching pair (that is, for the two IMF components in the th pair of candidate IMF component matching pairs, since the IMF component is a part of the PPG heart rate signal, it can also be called the absolute value of the difference in slope between the signals of the two IMF components in the th pair of candidate IMF component matching pairs).

[0040] Then, respectively determine the first amplitude of the IMF component matched with the IMF component corresponding to the first action in each candidate IMF component matching pair (that is, in the th candidate IMF component matching pair, the amplitude of the IMF component (the signal of the IMF component) matched with the th IMF component corresponding to the th action), and the second amplitude of the IMF component matched with the IMF component corresponding to the second action (that is, in the Among the candidate IMF component matching pairs, for the action corresponding to the amplitude of the IMF component (the signal of the IMF component) matched by the th IMF component, and respectively determine the second absolute value of the difference between the first amplitude and the corresponding second amplitude

[0041] Finally, according to the first absolute value , the second absolute value and the number of candidate IMF component matching pairs , determine the first difference situation between the first action and the second action under each IMF component in various actions : Among them, is the first difference situation between the th action and the th action under the th IMF component. Therefore, return the steps of respectively determining the first action and the second action from various actions until the first difference situation between the actions of each IMF component matching pair is determined under each IMF component , that is , , When taking different values respectively, represents the first difference situation between the actions of each IMF component matching pair.

[0042] Step 2: Determine the acceleration segment corresponding to each action from the acceleration data, match the acceleration segments corresponding to each action through DTW, respectively determine several acceleration matching pairs between actions of the same type, and determine the second difference situation of the acceleration between the actions of each acceleration matching pair according to several acceleration matching pairs between actions of the same type.

[0043] First, the acceleration data includes acceleration segments corresponding to several actions respectively. Match the acceleration segments corresponding to each action through DTW, and respectively determine several acceleration matching pairs between actions of the same type. The principle of DTW matching is similar to that of IMF component matching and will not be elaborated here. Through matching, several acceleration matching pairs between actions of the same type can be respectively determined. Then, respectively determine the first action (for example, the th action) and the second action (for example, the th action) from various actions, and according to several acceleration matching pairs between actions of the same type, determine several candidate acceleration matching pairs corresponding to the first action and the second action, that is, the acceleration of the th action and the All acceleration matching pairs that match the acceleration of a single action.

[0044] Secondly, determine the third absolute value of the difference in slopes between acceleration segments in each candidate acceleration matching pair (i.e., the absolute value of the difference in slopes between acceleration segments in the th candidate acceleration matching pair).

[0045] Then, respectively determine the third amplitude of the acceleration segment that matches the acceleration segment corresponding to the first action in each candidate acceleration matching pair (i.e., in the th candidate acceleration matching pair, the amplitude of the acceleration segment that matches the acceleration segment corresponding to the th action), the fourth amplitude of the acceleration segment that matches the acceleration segment corresponding to the second action (i.e., in the th candidate acceleration matching pair, the amplitude of the acceleration segment that matches the acceleration segment corresponding to the th action), and respectively determine the fourth absolute value of the difference between the third amplitude and the corresponding fourth amplitude .

[0046] Finally, based on the third absolute value , the fourth absolute value and the number of candidate acceleration matching pairs , determine the second difference situation between the first action and the second action in each type of action: Among them, is the second difference situation between the th action and the th action. Therefore, return the steps to determine the first action and the second action respectively from each type of action until the second difference situation of the acceleration between the actions of each acceleration matching pair is determined , that is , when taking different values, represents the second difference situation of the acceleration between the actions of each acceleration matching pair.

[0047] S303. According to the temperature data and the action difference situation, determine the change deviation of each IMF component of each action, and based on the change deviation of each IMF component of each action, determine the influence situation of each IMF component corresponding to each action on the motion artifact.

[0048] First, according to the temperature data, determine the temperature DTW matching distance between actions of the same type (i.e., the temperature DTW matching distance between the th action and the th action in the same category), and respectively determine the temperature difference situation between actions of the same category according to the natural exponential function and the temperature DTW matching distance: Among them, is the temperature difference situation between the th action and the th action in the same category.

[0049] Secondly, respectively determine the ratio of the first difference situation to the second difference situation, and determine the corresponding variance according to each ratio.

[0050] Then, perform a summation process according to the ratio , the temperature difference situation and the number of actions in each type of action to obtain a summation result , and obtain the change deviation situation of each IMF component of each action according to the product of the reciprocal of the variance and the summation result: Among them, is the change deviation situation of the th IMF component of the th action, represents the change stability situation of the acceleration data of the current category. The larger its value, the more chaotic the relationship between the acceleration data and the heart rate change is after the th action. For the current chaotic situation, each action may correspond to a different heart rate situation.

[0051] Finally, according to the change deviation situation of each IMF component of each action, calculate the difference in the change deviation situation between two adjacent actions, and determine the influence situation of each IMF component corresponding to each action on the motion artifact : = Among them, represents the difference in the change deviation situation between the th action and the adjacent th action, denoted as the th action corresponding to the The influence of each IMF component on motion artifacts. In the embodiments of the present application, considering that the monitored object undergoes a continuous and ongoing change during motion, and the corresponding heart rate change is similar, when analyzing and reconstructing the weights subsequently, it is necessary to consider the offset of its components caused by the continuous motion changes. Therefore, in the embodiments of the present application, the influence of each IMF component corresponding to each action on motion artifacts is calculated. .

[0052] It should be noted that in actual situations, there may be some IMF components that contain motion artifacts in the heart rate information. Therefore, it is necessary to analyze the fluctuations in each obtained IMF component. For the IMF components with relatively large fluctuations affected currently, their weights can be reduced during reconstruction.

[0053] In one implementation manner, step S400 includes steps S401 - S403: S401. Determine the component weight corresponding to each IMF component according to the influence of each IMF component corresponding to each action on motion artifacts.

[0054] Specifically, according to the influence of each IMF component corresponding to each action on motion artifacts , determine the component weight corresponding to each IMF component , representing the overall weight corresponding to the th IMF component.

[0055] S402. Respectively determine the amplitude differences between the corresponding IMF components of adjacent pairs of actions, and respectively determine the reconstruction weights of the IMF components of each action according to the amplitude differences and the component weight corresponding to each IMF component.

[0056] Optionally, first, respectively determine the amplitude differences between the corresponding IMF components of adjacent pairs of actions , is the amplitude corresponding to the th action's th IMF component (or the signal of the IMF component), is the amplitude corresponding to the th IMF component (or the signal of the IMF component) of the a - 1th action.

[0057] Secondly, respectively determine the fluctuation weight of each IMF component according to the natural exponential function and the opposite of the amplitude difference. .

[0058] Then, based on the fluctuation weights of each IMF component and the product of the component weights respectively, determine the reconstruction weights of each IMF component for each action: Wherein, is the reconstruction weight of the th IMF component of the th action, is a hyperparameter to prevent the denominator from being zero.

[0059] S403. Perform signal reconstruction according to the reconstruction weights of each IMF component for each action to obtain the target PPG heart rate signal with motion artifacts removed.

[0060] Specifically, according to the reconstruction weights of each IMF component for each action, perform weighted summation on each IMF component corresponding to each action to obtain the target PPG heart rate signal with motion artifacts removed. It can be understood that after each real-time acquisition of the PPG heart rate signal, based on the above process, the target PPG heart rate signal with motion artifacts removed can be finally obtained, avoiding the distortion of the heart rate signal caused by motion artifacts and being beneficial to improving the accuracy of heart rate measurement.

[0061] In one implementation, according to the above operations, the target PPG heart rate signal with motion artifacts removed can be obtained, that is, the target PPG heart rate signal with at least part or completely removed motion artifacts. At this time, the peak region in the target PPG heart rate signal can be extracted, and then the time interval between two peaks in the peak region can be calculated. Dividing 60 by this time interval can obtain the heart rate. Among them, when displaying the heart rate, the continuous five heart rates can be averaged, and the average heart rate after averaging is the heart rate value at the current moment.

[0062] The method of the embodiment of the present application decomposes and classifies the actions of the monitored object, analyzes the PPG heart rate signals corresponding to the same type of actions, uses the influence of the IMF components corresponding to different classified actions obtained by EMD decomposition on motion artifacts as the degree of artifact interference in the current PPG heart rate signal, and then determines the reconstruction weights of the decomposed IMF components for signal reconstruction to obtain the target PPG heart rate signal with motion artifacts removed, reducing the influence of motion artifacts on the heart rate signal and having an obvious artifact removal effect when the temperature changes.

[0063] It should be noted that the above sequence of the embodiments of the present invention is only for description and does not represent the superiority or inferiority of the embodiments. The processes depicted in the drawings do not necessarily require the specific order or continuous order shown to achieve the desired results. In some implementations, multitasking and parallel processing are also possible or may be beneficial.

[0064] Each embodiment in this specification is described in a progressive manner. For the same or similar parts among the embodiments, reference can be made to each other, and the differences between each embodiment and other embodiments are emphasized respectively.

Claims

1. A method for eliminating motion artifacts of heart rate signals for thermal endurance monitoring, characterized in that: The method comprises: During the thermal endurance monitoring process, the temperature data, acceleration data and PPG heart rate signal of the monitored object are obtained; Determine different types of actions according to the acceleration data, and decompose the segments of the PPG heart rate signal corresponding to the different types of actions to determine the IMF components corresponding to each of the actions; Determine, according to each IMF component corresponding to each of the actions and the temperature data, the influence of each IMF component corresponding to each of the actions on the motion artifact; According to the influence of each IMF component corresponding to each of the actions on the motion artifacts, signal reconstruction is performed to obtain a target PPG heart rate signal with motion artifacts eliminated.

2. The method for eliminating motion artifacts of heart rate signals for thermal endurance monitoring according to claim 1, characterized in that: Determining different types of actions according to the acceleration data includes: Performing motion decomposition on the acceleration data to obtain motion segments of a plurality of actions, and performing normalization processing on each of the motion segments respectively; The DTW distance between each of the normalized motion segments is determined, and each of the motion segments is clustered according to the DTW distance to determine different types of actions.

3. The method for eliminating motion artifacts of heart rate signals for thermal endurance monitoring according to claim 1, characterized in that: Determining, according to the IMF components corresponding to each of the actions and the temperature data, the influence of the IMF components corresponding to each of the actions on the motion artifacts comprises: Matching the IMF components corresponding to each of the actions through DTW, and determining a number of IMF component matching pairs between actions of the same type; Determining action differences between actions of the same type according to a plurality of the IMF component matching pairs and the acceleration data; According to the temperature data and the action differences, the change deviation of each IMF component of each action is determined, and according to the change deviation of each IMF component of each action, the influence of each IMF component corresponding to each action on the motion artifact is determined.

4. The method for eliminating motion artifacts of heart rate signals for thermal endurance monitoring according to claim 3, characterized in that: Determining the action differences between actions of the same type according to the plurality of IMF component matching pairs and the acceleration data includes: According to the plurality of IMF component matching pairs, determining a first difference between actions of the respective IMF component matching pairs under each IMF component; Determine an acceleration segment corresponding to each of the actions from the acceleration data, match the acceleration segments corresponding to each of the actions through DTW, respectively determine a plurality of acceleration matching pairs between actions of the same type, and determine a second difference in acceleration between the actions of each of the acceleration matching pairs based on the plurality of acceleration matching pairs between the actions of the same type; The action difference situations between the actions of the same type include a first difference situation and a second difference situation.

5. The method for eliminating motion artifacts of heart rate signals for thermal endurance monitoring according to claim 4, characterized in that: The determining, according to the plurality of IMF component matching pairs, of a first difference between actions of each of the IMF component matching pairs under each of the IMF components comprises: Determine a first action and a second action from each type of action respectively, and determine a plurality of candidate IMF component matching pairs corresponding to the first action and the second action according to the plurality of IMF component matching pairs; Determine a first absolute value of a difference in slopes between IMF components in each of the candidate IMF component matching pairs; Respectively determining, in each of the candidate IMF component matching pairs, a first amplitude of an IMF component matched by the IMF component corresponding to the first action and a second amplitude of an IMF component matched by the IMF component corresponding to the second action, and respectively determining a second absolute value of a difference between the first amplitude and the corresponding second amplitude; According to the first absolute value, the second absolute value, and the number of the candidate IMF component matching pairs, determine the first difference between the first action and the second action under each IMF component in each type of action, and return to the step of determining the first action and the second action from each type of action respectively until the first difference between the actions of each IMF component matching pair under each IMF component is determined.

6. The method for eliminating motion artifacts of heart rate signals for thermal endurance monitoring according to claim 4, characterized in that: The determining, based on a plurality of acceleration matching pairs between actions of the same type, a second difference in acceleration between actions of each of the acceleration matching pairs comprises: Determine a first action and a second action from each type of action respectively, and determine a plurality of candidate acceleration matching pairs corresponding to the first action and the second action based on a plurality of acceleration matching pairs between actions of the same type; determining a third absolute value of a difference in slope between acceleration segments in each of the candidate acceleration matching pairs; respectively determining, in each of the candidate acceleration matching pairs, a third amplitude of the acceleration segment that matches the acceleration segment corresponding to the first action and a fourth amplitude of the acceleration segment that matches the acceleration segment corresponding to the second action, and respectively determining a fourth absolute value of a difference between the third amplitude and the corresponding fourth amplitude; Determine the second difference between the first action and the second action in each type of action according to the third absolute value, the fourth absolute value and the number of the candidate acceleration matching pairs, and return to the step of determining the first action and the second action from each type of action respectively until the second difference in acceleration between the actions of each acceleration matching pair is determined.

7. The method for eliminating motion artifacts of heart rate signals for thermal endurance monitoring according to claim 4, characterized in that: Determining the change deviation of each IMF component of each action according to the temperature data and the action difference, and determining the influence of each IMF component corresponding to each action on the motion artifact according to the change deviation of each IMF component of each action includes: Determine the temperature DTW matching distance between actions of the same type according to the temperature data, and determine the temperature difference between actions of the same type according to the natural exponential function and the temperature DTW matching distance respectively; respectively determining a ratio of the first difference situation to the second difference situation, and determining a corresponding variance according to each of the ratios; Performing a summation process according to the ratio, the temperature difference and the number of actions in each type of action to obtain a summation result, and obtaining a change deviation of each IMF component of each action according to the inverse of the variance and the product of the summation result; According to the variation deviation of each IMF component of each action, the difference of variation deviation between two adjacent actions is calculated to determine the influence of each IMF component corresponding to each action on the motion artifact.

8. The method for eliminating motion artifacts of heart rate signals for thermal endurance monitoring according to claim 7, characterized in that: The signal reconstruction is performed according to the influence of each IMF component corresponding to each of the actions on the motion artifacts to obtain the target PPG heart rate signal with the motion artifacts eliminated, comprising: Determine a component weight corresponding to each IMF component according to the influence of each IMF component corresponding to each of the actions on the motion artifact; Determine the amplitude differences corresponding to the IMF components of the adjacent two actions respectively, and determine the reconstruction weights of the IMF components of each action according to the amplitude differences and the component weights corresponding to each IMF component; Signal reconstruction is performed according to the reconstruction weights of each IMF component of each action to obtain a target PPG heart rate signal with motion artifacts eliminated.

9. The method for eliminating motion artifacts of heart rate signals for thermal endurance monitoring according to claim 8, characterized in that: Determining the reconstruction weight of each IMF component of each action according to the amplitude difference and the component weight corresponding to each IMF component includes: Determining the volatility weight of each IMF component according to the natural exponential function and the inverse of the amplitude difference, respectively; The reconstruction weights of the respective IMF components of each action are determined according to the fluctuation weight of each IMF component and the product of the component weights.

10. The method for eliminating motion artifacts of heart rate signals for thermal endurance monitoring according to claim 8, characterized in that: The signal reconstruction is performed according to the reconstruction weights of each IMF component of each action to obtain a target PPG heart rate signal with motion artifacts eliminated, comprising: According to the reconstruction weights of the IMF components of each action, the IMF components corresponding to each action are weighted and summed to obtain a target PPG heart rate signal with motion artifacts eliminated.

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