PPG signal quality evaluation method and device, wearable device and storage medium
A technology for signal quality evaluation and wearable devices, applied in diagnostic recording/measurement, medical science, diagnosis, etc., can solve the problems of PPG signal that cannot be evaluated for signal quality, and achieve the effect of improving signal quality that cannot be analyzed
Pending Publication Date: 2021-03-16
QINGDAO GOERTEK INTELLIGENT SENSOR CO LTD
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AI-Extracted Technical Summary
Problems solved by technology
[0004] The main purpose of the present invention is to propose a PPG signal quality evaluation method, device, wearable device a...
Method used
In the present embodiment, by introducing the acceleration signal of described acceleration sensor, the signal characteristic under the frequency domain of PPG signal is compared with the signal characteristic under the acceleration signal frequency domain, and then get rid of the interference of motion artifact under the state of motion , to improve the reliability of signal quality detection and evaluation. Since the signal characteristics in the frequency domain are used for comparison, the obtained signal characteristics can be made more obvious, and then a clearer comparison and analysis can be performed, which helps to improve the efficiency of PPG signal analysis, and obtains the characteristics of PPG signals for clearer analysis. As a result, the feasibility of PPG signal analysis is enhanced.
[0054] In one embodiment, in order to reduce the interference of the inherent noise of the PPG signal, optionally, after the step of obtaining the PPG signal collected by the wearable device and the acceleration signal output by...
Abstract
The invention discloses a PPG signal quality evaluation method and device, a wearable device and a storage medium, and aims at evaluating whether a PPG signal collected by the wearable device can be analyzed or not. The wearable device is provided with an acceleration sensor. The PPG signal quality evaluation method comprises the following steps of: acquiring the PPG signal collected by the wearable device and an acceleration signal output by the acceleration sensor; performing time domain-to-frequency domain conversion on the obtained PPG signal and acceleration signal to obtain a PPG signaland an acceleration signal in a frequency domain; and comparing the amplitude spectrum of the PPG signal and the amplitude spectrum of the acceleration signal in the frequency domain to obtain a quality evaluation result of the PPG signal. According to the invention, the quality of the PPG signal is obtained through the signal characteristics in the frequency domain, so that the problem that the signal quality cannot be analyzed due to the fact that the PPG signal of the existing wearable device is not obvious in a moving state is solved.
Application Domain
CatheterDiagnostic recording/measuring +1
Technology Topic
Signal characteristicEngineering +5
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Examples
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Example Embodiment
[0043] Next, the technical solutions in the embodiments of the present invention will be described in contemplation in the embodiments of the present invention, and clearly, as described herein is merely, not all of the embodiments of the present invention. Based on the embodiments of the present invention, those of ordinary skill in the art will belong to the scope of the present invention without all other embodiments obtained without creative labor.
[0044] The present invention proposes a PPG signal quality assessment method for evaluating whether the PPG signal acquired in the moving state in the motion state can be parsed, and the wearable device has an acceleration sensor, the acceleration sensor for acquiring a wearable device Acceleration signal in motion state. The wearable device detects a blood volume change in a living tissue by a photometric change (PPG), which can characterize parameters such as the heart rate signal. The PPG signal quality corresponds to parsing performance of the PPG signal, and as the PPG signal quality increases, the resolution performance of the PPG signal is better.
[0045] See figure 1 In this embodiment, the PPG signal quality assessment method includes the following steps:
[0046] S100: Get the PPG signal collected by the wearable device and the acceleration signal output from the acceleration sensor.
[0047] The PPG signal and the acceleration signal output from the acceleration sensor are time domain signals. Wherein, the PPG signal and the acceleration signal are the signals acquired in the same period. By synchronizing the acceleration signal, the acceleration feature of the motion state of the wearable device can be convenient to the evaluation of the PPG signal quality.
[0048] S200: The acquired PPG signal and acceleration signal are time domain to frequency domain conversion to obtain PPG signals and acceleration signals under the frequency domain.
[0049]After acquiring the PPG signal and acceleration signal in the same period, the PPG signal and the acceleration in the time domain are faster to obtain the PPG signal and acceleration signal from the frequency domain to facilitate the PPG signal from the frequency domain and Acceleration signal analysis.
[0050] S300: The amplitude spectrum of the PPG signal from the frequency domain and the amplitude spectrum of the acceleration signal obtained by obtaining the quality evaluation result of the PPG signal.
[0051] In one embodiment, it is possible to define the detection time period as the PPG signal and acceleration signal, the PPG signal and acceleration signal, the first to 15th seconds, and the first to 15 seconds of the PPG signal and acceleration of the first to 15 seconds. Signals to perform detection evaluation separately.
[0052] Since the PPG signal quality characterizes parsing performance of the PPG signal, when the PPG signal is parsed, when the PPG signal quality reaches a certain range, it can be parsed. The optimum value of the PPG signal is 100 as an example. When the PPG signal quality reaches or is close to the optimal value 100, the PPG signal is capable of resolving; when the PPG signal quality is higher than the preset signal quality When the value is lower than the best value 100, the PPG signal quality is lower than the optimum value, but the PPG signal is capable of being parsed; when the PPG signal is lower than the preset signal quality value, the The PPG signal quality is low, and the PPG signal cannot meet the resolution requirements, then determine that the PPG signal cannot be parsed. In general, when the PPG signal quality is 100, when the PPG signal quality is higher than 50, the PPG signal can be parsed, and as the PPG signal quality is improved, the parsing performance is also Gradually increase, that is, the PPG signal quality is positively correlated with its parsing performance.
[0053] In the present embodiment, by introducing an acceleration signal of the acceleration sensor, signal characteristics of the frequency domain of the PPG signal are compared to the signal characteristics of the acceleration signal frequency domain, thereby excluding the interference of motion of motion in motion in motion, lifting signal Reliability of quality detection assessment. Due to the comparison of signal characteristics under the frequency domain, it is possible to make the obtained signal characteristics more obvious, and more clear comparison and analysis can be performed, which helps to improve the efficiency of PPG signal analysis, and obtain a clearer analysis of PPG signal characteristics. As a result, the feasibility of lifting PPG signal analysis.
[0054] In one embodiment, in order to reduce the interference of the inherent noise of the PPG signal, optionally, after the step of obtaining the PPG signal acquired by the wearable device and the acceleration signal output, the acquired PPG signal and acceleration are The signal performs the band pass filter denoising, performs low pass filtering on the PPG signal, filter out the processed high frequency noise, then perform high pass filtering, filter out the processed baseline drift and low frequency noise, resulting in the PPG signal and acceleration in the time domain Signal, then the PPG signal and acceleration signal under time domains and the acceleration signal are then converted to avoid the unique noise interference assessment results in the PPG signal.
[0055] In one embodiment, in the step S300, when the amplitude spectrum of the PPG signal under the frequency domain, the anastomosis of the amplitude spectrum of the acceleration signal reaches the preset anastomosis, and the motion fake is more severe to the PPG signal interference. The interference of motion fake cannot be removed from the PPG signal. At this time, it is determined that the Quality evaluation result of the PPG signal is that the PPG signal cannot be parsed.
[0056] The PPG signal quality has an optimum value SQ, the preset anastomosis range approaches the optimal value SQ, for example, within a 10% SQ range, all in the preset anastomosis range. When used in different devices, there is a certain deviation in the preset anastomosis range. In general, the smart watch is an example, preset PPG signal optimum value Sq = 100, the amplitude spectrum of the PPG signal under the frequency domain. When the amplitude spectrum of the acceleration signal is consistent, the spectrum of the PPG signal may be mixed with the motor spectrum, so the PPG signal quality is 10, the signal quality is the worst, and its parsing performance is the worst.
[0057] When it is determined whether the amplitude spectrum of the PPG signal in the frequency domain is inconsistent, or it is basically inconsistent, then the currently obtained PPG signal is smaller, determine the current acquired PPG signal quality. Whether it is at an optimal value to determine if the currently acquired PPG signal is parsed, it is intuitively to obtain the current PPG signal quality.
[0058] See figure 2 In another embodiment, when the currently obtained PPG signal is interfered with motion, the amplitude spectrum of the PPG signal may result in the amplitude spectrum of the PPG signal at the frequency domain, the anastomosis of the amplitude spectrum is not reached a preset anastomosis. The step S300 includes:
[0059] S310: When the amplitude spectrum of the PPG signal in the frequency domain and the anastomosis of the amplitude spectrum of the acceleration signal do not reach the preset anastomosis range, the amplitude spectrum of the PPG signal at the frequency domain is calculated and the amplitude spectrum of the acceleration signal. .
[0060] When the amplitude spectrum of the PPG signal in the frequency domain is inconsistent, the amplitude spectrum of the acceleration signal is inconsistent, and the phase difference ranges exceeds the preset anastomosis range, the currently obtained PPG signal is interference from the motion of motion. Taking the smart watch as an example, the PPG signal quality is optimal value SQ = 100, when the PPG signal quality is SQ <90, the amplitude spectrum of the PPG signal from the contrast frequency domain is calculated from the magnitude of the amplitude spectrum and acceleration signal. The deviation value of the spectrum.
[0061] S311: Contrast the deviation value and the preset maximum deviation value, when the deviation value is less than or equal to the preset maximum deviation value, it is determined that the Quality evaluation result of the PPG signal is that the PPG signal cannot be parsed.
[0062] In motion, the PPG signal quality is interfered with motion of motion, and therefore, when the amplitude spectrum of the PPG signal in the contrast frequency domain and the amplitude spectrum of the acceleration signal, when the deviation value is in a preset Within the maximum deviation value, it is not possible to eliminate motion fake interference in the PPG signal, and the PPG signal cannot be parsed. Among them, there is a difference in the preset maximum deviation value range in different devices, and the PPG signal quality is optimal SQ = 100 as an example, the preset maximum deviation value may be a preset threshold, when the contrast frequency domain The amplitude spectrum of the PPG signal and the amplitude spectrum of the acceleration signal are greater than the preset threshold, and the PPG signal quality can be parsed.
[0063] See image 3 Further, it is further optionally, when the deviation value is greater than the preset maximum deviation value, the currently obtained PPG signal describes the interference of motion of motion, but can be parsed, the step S300 further includes:
[0064] S312: When the deviation value is greater than the preset maximum deviation value, the frequency domain signal of the PPG signal subtracts the frequency domain signal of the acceleration signal to obtain a synthetic frequency domain signal;
[0065] When the deviation value is greater than the preset maximum deviation, the currently obtained PPG signal will be described, although it is disturbed by the motion of the motion, but can be parsed, and the PPG signal quality is further analyzed according to the synthetic frequency domain signal to determine it. No parsed.
[0066] S313: Gets the number of spectrum peaks in the preset spectral range in the preset spectrum range, determines the quality evaluation result of the PPG signal based on the number of peaks.
[0067] In this embodiment, the plot of the peaks, the worse the signal quality, and the number of peaks is negatively correlated with the PPG signal quality. By obtaining the number of spectrum peaks within the preset frequency domain signal in the preset spectral range, the current PPG signal quality is visually understood to facilitate the tester to understand the analysis performance of the current PPG signal.
[0068] In this embodiment, when the number of peaks is less than or equal to the preset minimum spectrum peak, it is determined that the Quality evaluation result of the PPG signal is that the PPG signal can be parsed.
[0069] Since the number of peaks of the synthetic frequency domain signal is negatively correlated with the PPG signal quality, the number of spectrum peaks of the synthetic frequency domain signal can be preset according to the specific device, wherein the synthesis obtained in the preset time period can be preset. The smaller the number of spectrum peaks in the preset spectrum range, the better the PPG signals in this period of time. When the synthetic frequency domain signal obtained in the preset time period is exceeded by the number of peaks in the preset spectrum range, it will illustrate that the PPG signal is very disturbed, and the acquired PPG signal cannot be parsed.
[0070] In this embodiment, when the number of peaks is greater than the number of preset minimum peaks, the current acquired PPG signal is more affected by motion fake, and the number of spectrum is determined. The quality evaluation result of the PPG signal also includes:
[0071] It is determined that the maximum spectral amplitude in the synthetic frequency domain signal is compared to the frequency value corresponding to the maximum spectral amplitude and the preset frequency section, when the frequency value corresponding to the maximum spectral amplitude is in a preset frequency section, it is determined. The quality evaluation result of the PPG signal is that the PPG signal can be parsed. The preset frequency section is not larger than the maximum frequency value of the synthetic frequency domain signal, and is not smaller than the smallest frequency value of the synthetic frequency domain signal.
[0072] When obtaining the maximum spectral amplitude in the synthetic frequency domain signal, the frequency value corresponding to the maximum spectral amplitude is acquired, and the frequency value corresponding to the maximum spectral amplitude in the synthetic frequency domain signal is not greater than the synthetic frequency domain signal. The maximum frequency value is not less than the minimum frequency value of the synthetic frequency domain signal, indicating that the PPG signal can be parsed.
[0073] Alternatively, when the number of spectrum is larger than the number of preset minimum spectrum peaks, the current acquired PPG signal will be largely affected by the motion fake, and the PPG signal is determined based on the number of peaks. The quality assessment results also include:
[0074] It is determined that the second large spectral amplitude in the synthetic frequency domain signal is compared to the frequency value corresponding to the second large spectrum magnitude and the preset frequency section, and the frequency value corresponding to the second large spectrum amplitude is in the preset. When the frequency interval is, it is determined that the Quality evaluation result of the PPG signal is that the PPG signal can be parsed.
[0075] When the second large spectrum amplitude in the synthetic frequency domain signal is obtained, the frequency value corresponding to the second large spectrum magnitude is acquired, and the frequency value corresponding to the second large spectrum amplitude in the synthetic frequency domain signal is not greater than The maximum frequency value of the synthetic frequency domain signal is not less than the minimum frequency value of the synthetic frequency domain signal, indicating that the PPG signal is resolved. At this time, the PPG signal quality under the maximum spectral amplitude corresponding to the frequency value is superior to the PPG signal quality under the second large spectrum amplitude corresponding to the frequency value, the maximum spectral amplitude corresponding to the PPG signal under the frequency value. The parsing performance is superior to the PPG signal under the frequency value corresponding to the second large spectrum amplitude.
[0076] Alternatively, when the number of spectrum is larger than the number of preset minimum spectrum peaks, the current acquired PPG signal will be largely affected by the motion fake, and the PPG signal is determined based on the number of peaks. The quality assessment results also include:
[0077] Determine the third large spectral amplitude in the synthetic frequency domain signal, compared to the frequency value corresponding to the third large spectrum amplitude and the preset frequency section, when the frequency value corresponding to the third large spectrum amplitude is in a preset When the frequency interval is, it is determined that the Quality evaluation result of the PPG signal is that the PPG signal can be parsed.
[0078]When the third large spectral amplitude in the synthetic frequency domain signal is obtained, the frequency value corresponding to the third large spectrum magnitude is acquired, and the frequency value corresponding to the third large spectral amplitude in the synthetic frequency domain signal is not greater than The maximum frequency value of the synthetic frequency domain signal is not less than the minimum frequency value of the synthetic frequency domain signal, indicating that the PPG signal is resolved. At this time, the PPG signal quality under the second large spectral amplitude is superior to the PPG signal quality under the frequency value corresponding to the third large spectrum amplitude, the second large spectrum amplitude corresponding to the frequency value. The parsing performance of the PPG signal is superior to the PPG signal under the frequency value corresponding to the third large spectrum amplitude.
[0079] Contraction below Figure 1 to 3 The principles of the invention are described in detail. The present invention converts the time domain signal of the PPG signal and the acceleration signal into the frequency domain signal by acquiring the PPG signal and the acceleration sensor output, by the PPG signal and the acceleration signal under the frequency domain to determine the quality of the PPG signal. In motion, the PPG signal will be affected by the motion fake, so that the quality of the PPG signal is lowered. When the amplitude spectrum of the PPG signal from the PPG signal under the frequency domain is obtained, if the amplitude spectrum of the PPG signal under the contrast frequency domain under the frequency domain is basically the same, or the amplitude spectrum of the acceleration signal is substantially In the range of the preset anastomosis, the motion fake is more severe to the PPG signal, and cannot remove the interference of the motion of motion from the PPG signal. At this time, the quality evaluation result of the PPG signal is that the PPG signal cannot be parsed.
[0080] When the amplitude spectrum of the PPG signal under the frequency domain, the amplitude spectrum of the acceleration signal is inconsistent, and when the preset anastomosis range is exceeded, since the PPG signal quality is a certain range, the contrast frequency domain under the frequency domain The amplitude spectrum of the lower PPG signal and the amplitude spectrum of the acceleration signal are smaller than the preset maximum deviation value, which means that motion for motion in the PPG signal cannot be removed, and the quality evaluation result of the signal is that the PPG signal cannot be parsed.
[0081] When the amplitude spectrum of the PPG signal under the frequency domain, the amplitude spectrum of the acceleration signal is greater than the preset maximum deviation value, the PPG signal can be used to eliminate the interference of the motion of motion, the PPG signal can be resolved, then calculate the synthesis The frequency domain signal evaluates the PPG signal quality based on the synthetic frequency domain signal. After obtaining the synthetic frequency domain signal, the number of spectrum peaks in the preset frequency domain signal is obtained. The more the number of peaks, the worse the signal quality, and in turn can evaluate the current number of the spectrum. PPG signal quality.
[0082] At the same time, after the synthetic frequency domain signal is obtained, the frequency corresponding to the top three major spectrum amplitude of the synthetic frequency domain signal is obtained, and the maximum frequency and minimum frequency of the synthetic frequency domain signal will be compared to the maximum frequency and minimum frequency of the synthetic frequency domain signal. Any one of the three major spectrum amplitudes in the frequency of the synthetic frequency domain signal is between the maximum frequency and minimum frequencies of the synthetic frequency domain signal, indicating that the currently acquired PPG signal can be parsed.
[0083] The present invention also proposes an embodiment of a PPG signal quality assessment device that performs the method of any of the above embodiments. The apparatus includes: a signal generating unit 1004 for outputting a PPG signal and an acceleration signal; processor 1001; and memory 1002 for storing the PPG signal quality evaluation program that can be run on the processor; When the PPG signal quality evaluation process is executed by the processor, the step of implementing the PPG signal quality assessment method as described above is implemented.
[0084] The signal generating unit 1004 is used to output a PPG signal and an acceleration signal. The processor 1001 can be a CPU, which may include a network interface, a user interface, a communication bus 1003, and the like. The communication bus 1002 is used to implement connection communication between these components. The user interface can include a display, an input unit such as a button, and an optional user interface can also include a standard wired interface, a wireless interface. The network interface can include a standard wired interface, a wireless interface, such as a Wi-Fi interface, a serial port, and the like. Memory 1002 can be a high speed RAM memory 1002 or a stable memory 1002 (Non-Volatile Memory), such as a disk memory 1002. Memory 1002 can also be a storage device independently of the processor 1001. The processor 1001 calls the PPG signal quality evaluation program stored in the memory and the PPG signal and acceleration signal from the signal generating unit, and performs PPG signal quality assessment.
[0085] The present invention also proposes an embodiment of a wearable device. The wearing device stores a device having a method of performing the PPG signal quality assessment method as described in the above embodiment. The wearable device can be a smart watch or the like.
[0086] The present invention also proposes an embodiment of a storage medium. The storage medium stores an evaluation procedure of a PPG signal quality device, the PPG signal quality device, implemented step of implementing the PPG signal quality assessment method as claimed in any of the above embodiments. The readable storage medium can be a readable storage medium of various class storage program code such as a U disk, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a disk, or optical disk.
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