A detection method and system using PPG signal sampling in motion state

Abstract

The application provides a detection method and system using PPG signal sampling in a motion state, the method comprising: collecting and converting PPG signals, linear acceleration signals, rotary acceleration signals and electrical activity signals on the surface of human skin respectively, performing Fourier transform on the converted digital signals to form PPG spectrum sets, linear acceleration spectrum sets, rotary acceleration spectrum sets and EDA spectrum sets; performing difference set calculation on the PPG spectrum sets and the union spectrum sets to obtain a calculation spectrum set related to heart rate and respiratory frequency; in a frequency band where the heart rate is located, the frequency with the maximum energy amplitude in the calculation spectrum set is taken as heart rate data; in a frequency band where the respiratory frequency is located, the frequency with the maximum energy amplitude in the calculation spectrum set is taken as respiratory frequency data, and the reliability of the heart rate (or respiratory frequency) detection data is improved.

Description

Technical Field

[0001] This invention relates to the field of vital sign parameter detection, and in particular to a detection method and system that utilizes PPG signal sampling during motion. Background Technology

[0002] Currently, there are two commonly used methods for detecting heart rate: ECG (electrocardiogram) and PPG (photoplethysmography). ECG detects heart rate by capturing the bioelectrical signals generated during a heartbeat. Electrodes need to be attached to the body; during movement, vibrations between the electrodes and the body can interfere with the ECG signal, affecting the accuracy of heart rate data. PPG uses light and simultaneously receives reflected light from capillaries, calculating changes in blood flow within the capillaries. This requires placing LEDs and photodiodes close to the skin surface. During movement, vibrations between the detection device and the skin surface also interfere with PPG signal detection, ultimately affecting the accuracy of heart rate data. Because the human body surface is flexible, it is impossible to guarantee a completely stable and vibration-free detection device. Therefore, interference from movement is unavoidable; the only options are to minimize or filter it out.

[0003] In related technologies, heart rate data (or respiratory rate data) is generally obtained by detecting a single type of PPG signal. However, this method of obtaining heart rate data (or respiratory rate data) by detecting a single type of PPG signal is difficult to filter out the interference of exercise on the collected PPG signal, thus making the reliability of heart rate (or respiratory rate) detection data low.

[0004] To address this problem, the present invention provides a detection method and system that utilizes PPG signal sampling during motion, thereby solving the aforementioned issues. Summary of the Invention

[0005] In order to solve the problems existing in the prior art, this invention innovatively proposes a detection method and system for sampling PPG signals under exercise conditions, which effectively solves the problem of low reliability of heart rate (or respiratory rate) detection data caused by the prior art, and effectively improves the reliability of heart rate (or respiratory rate) detection data.

[0006] The first aspect of this invention provides a detection method using PPG signal sampling in motion, comprising: The PPG signal was collected as the intensity of reflected light from blood in capillaries changed during motion, and the collected PPG signal was converted into a digital PPG signal. The linear acceleration and rotational acceleration signals of human motion are collected, and the collected linear acceleration and rotational acceleration signals of human motion are converted into linear acceleration digital signals and rotational acceleration digital signals. The electrical activity signals on the surface of human skin are collected to detect the relative motion between the sensor and the human body surface; Fourier transforms were performed on PPG digital signals, linear acceleration digital signals, rotational acceleration digital signals, and electrical activity signals on the surface of human skin, and the spectrum with the largest energy proportion was selected to form PPG spectrum set, linear acceleration spectrum set, rotational acceleration spectrum set, and EDA spectrum set respectively. The difference between the PPG spectrum set and the union spectrum set is calculated to obtain the calculated spectrum set related to heart rate and respiratory rate. The union spectrum set is the union of the linear acceleration spectrum set, the rotational acceleration spectrum set, and the EDA spectrum set. In the frequency band where the heart rate is located, the frequency with the largest energy amplitude in the calculated spectrum set is used as the heart rate data. In the frequency band where the respiratory rate is located, the frequency with the largest energy amplitude in the calculated spectrum set is used as the respiratory rate data.

[0007] Optionally, if the amplitude of the linear acceleration digital signal change is less than a first preset amplitude threshold, the linear acceleration spectrum set in the difference set is empty; if the amplitude of the rotational acceleration digital signal change is less than a second preset amplitude threshold, the rotational acceleration spectrum set in the difference set is empty; if the amplitude of the electrical activity signal on the surface of human skin change is less than a third preset amplitude threshold, the EDA spectrum set in the difference set is empty.

[0008] Optionally, after converting the acquired PPG signal into a PPG digital signal, the method further includes preprocessing the PPG digital signal; the preprocessing includes: Acquire the initial sampled value of the PPG digital signal and the corresponding control parameters for sampling; the control parameters include the operating current I of the light source module. led The input bias current I of the amplifier in the analog front-end control chip offset Gain factor K gain The light source module is used to irradiate the blood in the capillaries, and the analog front-end control chip is used to adjust the brightness of the light source module. Based on the corresponding sampling control parameters, the initial sampled value V of the PPG digital signal is... s The PPG digital signal is then standardized to obtain the sampled value V. unify ; Based on the changes in control parameters during the sampling process of the PPG digital signal, the compensation amount V is set. diff ; The sampled value V of the unified PPG digital signal unify With compensation amount V diff Perform interpolation to obtain the preprocessed PPG digital signal sample value V. ppg .

[0009] Furthermore, based on the corresponding sampling control parameters, the initial sampled value V of the PPG digital signal is... s The PPG digital signal is then standardized to obtain the sampled value V. unify Specifically: V unify = (V s / K gain I offset ) / I led ; Among them, V unify V represents the initial sampled value of the PPG digital signal and the sampled value of the PPG digital signal after the current control parameters have been standardized. s K represents the initial sample value of the PPG digital signal in this sampling. gain I represents the gain factor of the amplifier in the current analog front-end control chip. led I represents the operating current of the current wavelength generation module. offset This is the input bias current of the amplifier in the current analog front-end control chip; The sampled value V of the unified PPG digital signal unify With compensation amount V diff Perform interpolation to obtain the preprocessed PPG digital signal sample value V. ppg Specifically: V ppg = V unify - V diff ; Among them, V ppg V represents the sampled value of the preprocessed PPG digital signal. diff This is the compensation amount after this sampling.

[0010] Optionally, after converting the acquired PPG signal into a PPG digital signal, the method further includes: based on the initial sample value V of the PPG digital signal. s The amplitude of the change in sampled values ​​within the acquisition period, V a The control parameters are dynamically adjusted during the PPG signal acquisition process; the initial sample value V of the PPG digital signal is used as the basis for this adjustment. s The amplitude of the change in sampled values ​​within the acquisition period, V a Dynamic adjustment of control parameters during PPG signal acquisition includes: Obtain the initial sample value V of the PPG digital signal s ; Find the maximum value V of the sampled values ​​within the acquisition period. smax and minimum value V smin ; The maximum value V of the sampled value smaxand minimum value V smin Perform interpolation and calculate the amplitude V of the sampled value change within the acquisition period. a ; If the amplitude of the change in the sampled value during the acquisition period is V a Not within the preset first valid range, or the initial sample value V s If the signal is not within the preset second effective range, the control parameters during PPG signal acquisition will be adjusted to adjust the amplitude V of the sampled value change within the acquisition period. a and initial sample value V s The preset adjustment requirements are met, wherein the preset adjustment requirements are related to the amplitude V of the change in the sampled values ​​within the acquisition period. a The preset maximum amplitude V amax and preset minimum amplitude V amin The geometric mean, and the initial sample value V s Within the preset second effective range.

[0011] Furthermore, adjusting the control parameters during PPG signal acquisition specifically includes: Based on the preset maximum amplitude V within the acquisition period amax and preset minimum amplitude V amin Calculate the magnitude of the target change; If the current change magnitude V a (n) is greater than the preset maximum amplitude V amax At this time, reduce the gain factor K of the amplifier in the analog front-end control chip. gain Alternatively, simultaneously reduce the operating current I of the light source module. led If the current change amplitude V a (n) is less than the preset minimum amplitude value V amin At this time, increase the gain factor K of the amplifier in the analog front-end control chip. gain Alternatively, simultaneously increase the operating current I of the light source block. led ; According to the adjusted gain factor K of the amplifier in the analog front-end control chip gain (n+1) and the operating current I of the light source module led (n+1), calculate the adjusted input bias current I of the amplifier in the analog front-end control chip. offset (n+1); Adjust the gain factor K of the amplifier in the analog front-end control chip. gain (n+1) Input bias current I offset (n+1) Operating current I of the light source module led (n+1) By setting the registers inside the analog front-end control chip, the adjusted control parameters take effect.

[0012] Furthermore, when only the gain factor K of the amplifier in the analog front-end control chip is adjusted... gain When the preset adjustment requirements are met, only the gain factor K of the amplifier in the analog front-end control chip is adjusted. gain The operating current I of the light source module led The following remains unchanged: K gain (n+1)=( ) / V a (n) K gain (n); I led (n+1)=I led (n); Among them, K gain (n+1) represents the gain factor of the amplifier in the analog front-end control chip after adjusting the control parameters, V a (n) represents the magnitude of the change in the current sampled value within the acquisition period, V amax V is the preset maximum amplitude. amin K is the preset minimum amplitude value. gain (n) represents the gain factor of the amplifier in the analog front-end control chip before adjusting the control parameters, I led (n+1) represents the operating current of the light source module after adjusting the control parameters, I led (n) represents the operating current of the light source module before adjusting the control parameters; When only the gain factor K of the amplifier in the analog front-end control chip is adjusted gain If the preset adjustment requirements cannot be met, then adjust the gain factor K of the amplifier in the analog front-end control chip. gain At the same time, adjust the operating current I of the light source module. led Specifically: If the current change magnitude V a (n) is less than the preset minimum amplitude value V amin Time: K gain (n+1)=K gainmax Or, if the current change magnitude V a (n) is greater than the preset maximum amplitude V amax Time: K gain (n+1)=K gainmin Among them, K gainmax To simulate the maximum gain of the amplifier in the front-end control chip, K gainmin To simulate the minimum gain of the amplifier in the front-end control chip; Adjusted operating current I of the light source module led (n+1) specifically refers to: I led (n+1)=( ) / V a (n) K gain (n) / K gain (n+1)) I led (n).

[0013] Optionally, based on the gain factor K of the amplifier in the adjusted analog front-end control chip. gain (n+1) and the operating current I of the light source module led (n+1), calculate the adjusted input bias current I of the amplifier in the analog front-end control chip. offset (n+1) specifically refers to: I offset (n+1) = (V s (n) / K gain (n+1)) (V stand I led (n+1)); Among them, I offset (n+1) represents the adjusted input bias current of the amplifier in the analog front-end control chip, V s (n) represents the initial sample value V of the PPG digital signal before adjustment. s K gain (n+1) represents the adjusted gain of the amplifier in the analog front-end control chip, V stand As a preset sampling standard value, I led (n+1) represents the adjusted operating current of the light source module.

[0014] Optionally, after determining the adjusted control parameters, the method further includes: After the next sampling, based on the sampled value V after the next unification process. unify (n+1) Set the compensation amount V for the next sampling. diff (n+1), specifically: V diff (n+1) = V unify (n+1) V stand ; Among them, V diff (n+1) represents the compensation amount after the next sampling, V unify (n+1) represents the initial sample value of the first PPG digital signal after control parameter adjustment and the sample value after the adjusted control parameters have been standardized, V stand This is the preset sampling standard value.

[0015] A second aspect of the present invention provides a detection system for sampling PPG signals during motion, comprising: a light source module, a light sensing module, an analog front-end control chip, an inertial sensor, an EDA sensor, and a microcontroller. The light source module is used to output light of a preset wavelength for irradiating capillaries; the light sensing module is used to receive light reflected from blood within capillaries and collect PPG signals that change with the intensity of reflected light during motion; the analog front-end control chip is used to adjust the output current to control the brightness of the light source module and to receive and convert the collected PPG signals into PPG digital signals; the inertial sensor is used to collect and convert linear acceleration and rotational acceleration signals of human motion into linear acceleration digital signals and rotational acceleration digital signals; the EDA sensor is used to collect electrical activity signals on the surface of human skin to detect the relative motion between the sensor and the human surface; and the microcontroller is used to execute the detection method for sampling PPG signals during motion as described in the first aspect of the present invention.

[0016] The technical solution adopted in this invention has the following technical effects: 1. In this invention, PPG signals, linear acceleration signals, rotational acceleration signals, and electrical activity signals are collected and converted respectively. Fourier transforms are performed on the PPG digital signals, linear acceleration digital signals, rotational acceleration digital signals, and electrical activity signals from the human skin surface, respectively, to form PPG spectrum sets, linear acceleration spectrum sets, rotational acceleration spectrum sets, and EDA spectrum sets. The difference between the PPG spectrum sets and the union spectrum sets is calculated to obtain a set of calculated spectrums related to heart rate and respiratory rate. In the frequency band of heart rate, the frequency with the largest energy amplitude in the calculated spectrum set is used as heart rate data; in the frequency band of respiratory rate, the frequency with the largest energy amplitude in the calculated spectrum set is used as respiratory rate data. This effectively solves the problem of low reliability of heart rate (or respiratory rate) detection data caused by existing technologies and effectively improves the reliability of heart rate (or respiratory rate) detection data.

[0017] 2. The technical solution of this invention integrates the PPG spectrum set, linear acceleration spectrum set, rotational acceleration spectrum set, and EDA spectrum set to determine the heart rate (or respiratory rate) detection data. It can filter out the signal of changes in blood flow in capillaries caused by exercise, as well as the influence of the relative motion between the measuring device and the human body surface on the acquisition of PPG signals. Thus, it calculates the signal of changes in blood flow in capillaries caused by heartbeat and respiratory activity, thereby achieving the function of measuring heart rate and respiratory rate data even in the exercise state.

[0018] 3. In the technical solution of this invention, if the amplitude of the frequency in the linear acceleration spectrum set is less than the first preset amplitude threshold, the linear acceleration spectrum set in the difference set is empty; if the amplitude of the frequency in the rotational acceleration spectrum set is less than the second preset amplitude threshold, the rotational acceleration spectrum set in the difference set is empty; if the amplitude of the frequency in the EDA spectrum set is less than the third preset amplitude threshold, the EDA spectrum set in the difference set is empty. Only when the amplitude of the corresponding influencing signal is greater than the corresponding threshold will the influencing signal be considered for the change signal of blood flow in capillaries, thereby improving the adaptability of heart rate (or respiratory rate) detection data.

[0019] 4. The technical solution of this invention can also preprocess the PPG digital signal; based on the control parameters corresponding to the sampling, the initial sample value V of the PPG digital signal is... s The PPG digital signal is then standardized to obtain the sampled value V. unify Based on the changes in control parameters during the sampling process of the PPG digital signal, set the compensation amount V. diff The sampled value V of the unified PPG digital signal. unify With compensation amount V diff Perform interpolation to obtain the preprocessed PPG digital signal sample value V. ppg This further improves the reliability of heart rate (or respiratory rate) detection data.

[0020] 5. The technical solution of this invention can also dynamically adjust the control parameters during the PPG signal acquisition process; and obtain the initial sample value V of the PPG digital signal. s Find the maximum value V of the sampled values ​​within the acquisition period. smax and minimum value V smin ; the maximum value V of the sampled value smax and minimum value V smin Perform interpolation and calculate the amplitude V of the sampled value change within the acquisition period. a If the amplitude V of the sampled value changes within the acquisition period a Not within the preset first valid range, or the initial sample value V s If the signal is not within the preset second effective range, the control parameters during PPG signal acquisition are dynamically adjusted to adjust the amplitude V of the sampled value change within the acquisition period. a It meets the preset requirements and further improves the reliability of heart rate (or respiratory rate) detection data.

[0021] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit the invention. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a flowchart illustrating the method of Embodiment 1 in the present invention; Figure 2 This is a schematic diagram of a detection system that uses PPG signal sampling under motion conditions, based on the method of Embodiment 1 of the present invention. Figure 3 This is a flowchart illustrating the process of determining heart rate and respiratory rate data in the method of Embodiment 1 of the present invention; Figure 4 This is a schematic diagram of the process for preprocessing PPG digital signals in the method of Embodiment 1 of the present invention; Figure 5 This is a flowchart illustrating the dynamic adjustment of control parameters during PPG signal acquisition in Embodiment 1 of the present invention. Detailed Implementation

[0024] To clearly illustrate the technical features of this solution, the invention will be described in detail below through specific embodiments and in conjunction with the accompanying drawings. The following disclosure provides many different embodiments or examples for implementing different structures of the invention. To simplify the disclosure of the invention, components and arrangements of specific examples are described below. Furthermore, reference numerals and / or letters may be repeated in different examples. This repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. It should be noted that the components illustrated in the drawings are not necessarily drawn to scale. Descriptions of well-known components, processing techniques, and processes are omitted in this invention to avoid unnecessarily limiting the invention.

[0025] Example 1 like Figure 1 As shown, the present invention provides a detection method using PPG signal sampling in motion, comprising: S1, collect PPG signals as the intensity of reflected light from blood in capillaries changes during motion, and convert the collected PPG signals into PPG digital signals; S3 collects linear acceleration and rotational acceleration signals of human motion, and converts the collected linear acceleration and rotational acceleration signals of human motion into linear acceleration digital signals and rotational acceleration digital signals; S5 collects electrical activity signals from the surface of human skin to detect the relative motion between the sensor and the human body surface; S7 performs Fourier transforms on the PPG digital signal, linear acceleration digital signal, rotational acceleration digital signal, and electrical activity signal on the human skin surface, respectively, and selects the spectrum with the largest energy proportion to form the PPG spectrum set, linear acceleration spectrum set, rotational acceleration spectrum set, and EDA spectrum set. S9. Perform difference calculation on the PPG spectrum set and the union spectrum set to obtain the calculated spectrum set related to heart rate and respiratory rate. The union spectrum set is the union of the linear acceleration spectrum set, the rotational acceleration spectrum set, and the EDA spectrum set. In the frequency band where the heart rate is located, the frequency with the largest energy amplitude in the calculated spectrum set is used as the heart rate data. In the frequency band where the respiratory rate is located, the frequency with the largest energy amplitude in the calculated spectrum set is used as the respiratory rate data.

[0026] It should be noted that the detection method using PPG signal sampling in motion state in this embodiment of the invention is based on, for example, Figure 2 This is based on a detection system that utilizes PPG signal sampling during motion. Specifically, a detection system that utilizes PPG signal sampling during motion may include a light source module, a light sensing module, an analog front-end control chip (AFE), an inertial sensor (GSensor), an EDA sensor, and a microcontroller (MCU). The light source module outputs light of a preset wavelength to irradiate capillaries; the light sensing module receives light reflected from blood within capillaries and collects PPG signals that change with the intensity of reflected light during motion; the analog front-end control chip adjusts the output current to control the brightness of the light source module; and receives and converts the collected PPG signals into PPG digital signals; the inertial sensor collects and converts the linear acceleration and rotational acceleration signals of human motion into linear acceleration digital signals and rotational acceleration digital signals; the EDA sensor collects the EDA signals caused by the relative motion between the sensor and the human body surface; and the microcontroller acquires... Fourier transforms were performed on PPG digital signals, linear acceleration digital signals, rotational acceleration digital signals, and electrical activity signals from the human skin surface, respectively. The spectrum with the highest energy proportion was selected to form PPG spectrum sets, linear acceleration spectrum sets, rotational acceleration spectrum sets, and EDA spectrum sets. The difference between the PPG spectrum sets and their union sets was calculated to obtain the calculated spectrum sets related to heart rate and respiratory rate. The union set of these spectrum sets is the union of the linear acceleration spectrum sets, rotational acceleration spectrum sets, and EDA spectrum sets. Within the frequency band of heart rate, the frequency with the highest energy amplitude in the calculated spectrum sets was used as heart rate data; similarly, within the frequency band of respiratory rate, the frequency with the highest energy amplitude in the calculated spectrum sets was used as respiratory rate data.

[0027] Specifically, in steps S1-S5, the light source module includes a light-emitting diode LED1 for emitting light of a preset first wavelength and a light-emitting diode LED2 for emitting light of a preset second wavelength; the light-sensing module includes a photodiode PD1 and a photodiode PD2, wherein photodiode PD1 is used to receive the preset first wavelength light reflected by blood in capillaries and to acquire a first PPG signal adjusted by the intensity of the reflected preset first wavelength light during motion; photodiode PD2 is used to receive the preset second wavelength light reflected by blood in capillaries and to acquire a second PPG signal adjusted by the intensity of the reflected preset second wavelength light during motion; the inertial sensor includes an accelerometer. (3-axis accelerometer) and gyroscope sensor (3-axis gyroscope sensor). The accelerometer is used to collect and convert the linear acceleration signal of human motion into a linear acceleration digital signal, and the gyroscope sensor is used to collect and convert the rotational acceleration signal of human motion into a rotational acceleration digital signal. The EDA sensor includes EDA electrode 1 and EDA electrode 2 set on the skin surface. The voltage signal output by the constant voltage signal source is applied to the user's skin surface through EDA electrode 1 and EDA electrode 2. The skin impedance between EDA electrode 1 and EDA electrode 2 and the sampling resistor form a voltage divider circuit, which is used to collect the EDA signal caused by the relative motion between the sensor and the human body surface.

[0028] Specifically, the PPG sensor (photosensitive module) collects PPG (photoplethysmography) signals of the human body in motion. However, the PPG signals actually collected not only include the changes in blood flow in capillaries caused by heartbeat and breathing activities, but also the changes in blood flow in capillaries caused by human movement. In addition, it also includes the influence of the relative motion between the measuring device and the human body surface caused by movement on the PPG signal collection. Inertial sensors collect linear acceleration and rotational acceleration signals of human motion during motion. An EDA (electrodermal activity) sensor has two electrodes that are attached to the skin surface. A small voltage signal is applied between the two electrodes, and the current passing between the electrodes is detected to calculate the contact resistance. The change in this resistance is used to acquire the change signal of the relative motion between the measuring device and the human body surface.

[0029] like Figure 2As shown, the system includes LED1 and LED2, which emit red and green light of specific wavelengths to illuminate capillaries; photodiodes PD1 and PD2, which receive light reflected from blood within capillaries and output different currents depending on the intensity of the reflected light, used to acquire PPG signals; an analog front-end control chip (AFE), with a built-in LED driver circuit connected to LED1 and LED2, which can adjust the output current to control the brightness of the LEDs; the AFE also has a built-in input amplifier, whose input is connected to photodiodes PD1 and PD2 to receive PPG signals; the input amplifier can adjust the bias current of the input signal and the amplifier gain; and finally, the signal is converted into a digital signal by an ADC; and an inertial sensor (GSensor) with a built-in 3-axis accelerometer and 3-axis gyroscope, used to acquire the linear acceleration and rotation of human motion. The system includes an acceleration signal generator with a built-in ADC that converts the acquired analog signal into a digital signal. EDA electrodes 1 and 2 are two metal electrodes that are attached to the user's skin during use. A constant voltage signal source outputs a fixed voltage signal, which is applied to the user's skin through EDA electrodes 1 and 2. The skin impedance between EDA electrodes 1 and 2, along with a standard sampling resistor, forms a voltage divider circuit. A microcontroller (MCU) connects to an analog front-end control chip (AFE) and reads the acquired PPG digital signal through an interface circuit. The MCU also connects to an inertial sensor (GSensor) and reads the acquired linear and rotational acceleration digital signals through an interface circuit. Finally, the MCU connects to EDA electrodes 1 and 2, acquires the level signals from these electrodes, and converts them into digital signals using its internal ADC.

[0030] In this embodiment, the calculation of heart rate and respiratory rate data under exercise is mainly based on the collected PPG signal under exercise. The distribution of its energy spectrum is analyzed. At the same time, the motion signal of the human body and the signal of relative motion between the measuring device and the human body surface are collected and analyzed. The energy spectrum distribution of these spectra is analyzed by algorithms to filter out the signal of changes in capillary blood flow caused by exercise, as well as the influence of the relative motion between the measuring device (EDA sensor) and the human body surface on the PPG signal acquisition. Thus, the signal of changes in capillary blood flow caused by heartbeat and respiratory activity is calculated. Finally, according to the different frequency bands in which the heart rate and respiratory rate are located, the heart rate and respiratory rate data are calculated.

[0031] This embodiment can filter out the signal of changes in blood flow in capillaries caused by exercise, as well as the influence of the relative motion between the measuring device and the human body surface on the PPG acquisition signal, so that heart rate data can be measured even during exercise.

[0032] Specifically, such as Figure 3 As shown, step S7 includes: S71 acquires PPG signal data in real time, with the sampling rate selected based on the requirements of calculation accuracy and hardware processing capabilities; S72. Since the sampled data may be collected under different control parameter conditions, data unification processing is required to remove the influence of control parameter factors. In addition, the data collected at the point of control parameter change will have a step jump, so data splicing processing is also required to make the collected waveform continuous and stable, so as to facilitate subsequent data calculation. S73, considering the wide dynamic range of PPG data signals, requires dynamic adjustment of the sampling circuit's control parameters to ensure the sampling circuit also has a sufficiently wide dynamic range, guaranteeing that the acquired signal remains within the normal range. The sampling circuit's control parameters include the LED's operating current I. led The gain factor K of the amplifier in the analog front-end control chip gain The input bias current I of the amplifier in the analog front-end control chip offset ; S74 acquires linear acceleration and rotational acceleration data from inertial sensors in real time, with the sampling rate selected based on the requirements of computational accuracy and hardware processing capabilities. S75 acquires DEA (electrodermal activity) signal data in real time, with the sampling rate selected based on the requirements of calculation accuracy and hardware processing capabilities; it saves the acquired data within 40 seconds. S76, Perform FFT (Fast Fourier Transform) on the PPG sampled data, find the top 20 spectral values ​​fppg1...fppg20 with the largest energy proportion, save the frequency, amplitude and phase of these 20 spectra, and form the PPG spectrum set Fppg = {fppg1... fppg20}; S77. Perform FFT (Fast Fourier Transform) on the linear acceleration sampling data, find the top 3 spectral values ​​with the largest energy proportion facce1...facce3, save the frequency, amplitude and phase values ​​of these 3 spectra, and form the linear acceleration spectrum set Facce = {facce1 ... facce3}. S78. Perform FFT (Fast Fourier Transform) on the rotational acceleration sampling data, find the top 3 spectral values ​​fgyro1...fgyro3 with the largest energy proportion, and save the frequency, amplitude and phase values ​​of these 3 spectra to form the rotational acceleration spectrum set Fgyro = {fgyro1 ... fgyro3}. S79, perform FFT (Fast Fourier Transform) on the EDA signal sampled data (EDA digital signal, microcontroller built-in ADC, convert EDA signal to EDA digital signal), find the top 3 spectrum values ​​with the largest energy proportions, feda1...feda3, save the frequency, amplitude and phase values ​​of these 3 spectra, and form the EDA signal spectrum set Feda = {feda1 ... feda3}; Specifically, in step S9, the difference between the PPG spectrum set and the union spectrum set is calculated to obtain the calculated spectrum set related to heart rate and respiratory rate. The union spectrum set is the union of the linear acceleration spectrum set, the rotational acceleration spectrum set, and the EDA spectrum set. Specifically, the spectrum generated by body movement is analyzed; the spectrum generated by body movement exists within the linear acceleration spectrum set Facce and the rotational acceleration spectrum Fgyro, i.e. The set of motion spectra is Fmotion = Facce ∪ Fgyro; The spectrum of the relative motion between the analysis and detection device and the skin surface exists in the EDA spectrum set Feda; the calculated spectrum set Fhr related to heart rate and respiratory rate is: The set Fhr = Fppg \ (Fmotion ∪ Feda) = Fppg \ (Facce ∪ Fgyro ∪ Feda) is the set of calculated spectra related to heart rate and respiratory rate. That is, the set of spectra related to heart rate and respiratory rate is the difference between the PPG spectrum set Fppg and the union spectrum set. The difference set is the union of the linear acceleration spectrum set Facce, the rotational acceleration spectrum set Fgyro, and the EDA spectrum set Feda.

[0033] Within the frequency band of heart rate, the frequency with the largest energy amplitude in the calculated spectrum set is used as the heart rate data; within the frequency band of respiratory rate, the frequency with the largest energy amplitude in the calculated spectrum set is used as the respiratory rate data.

[0034] Specifically, the frequency with the largest energy amplitude within the range of 0.5Hz to 4Hz (the frequency band where the heart rate is located) is the heart rate frequency fhr; the frequency with the largest energy amplitude within the range of 0.05Hz to 1Hz (the frequency band where the respiratory rate is located) is the respiratory rate fresp. Finally, convert the heart rate frequency to the corresponding unit, that is: Heart rate = 60 fhr (times per minute); Convert the breathing frequency into the corresponding units, that is: Breathing count = 60 fresp (times per minute); A 2-second delay is applied to overwrite the earliest sampled data while retaining the latest collected data, continuously calculating heart rate and respiratory rate data.

[0035] Preferably, if the amplitude of the linear acceleration digital signal change is less than a first preset amplitude threshold (the amplitude of the frequency change in the linear acceleration spectrum set is less than the first preset amplitude threshold), then the linear acceleration spectrum set in the difference set is empty; if the amplitude of the rotational acceleration digital signal change is less than a second preset amplitude threshold (the amplitude of the frequency change in the rotational acceleration spectrum set is less than the second preset amplitude threshold), then the rotational acceleration spectrum set in the difference set is empty; if the amplitude of the electrical activity signal on the surface of human skin change is less than a third preset amplitude threshold (the amplitude of the frequency change in the EDA spectrum set is less than the third preset amplitude threshold), then the EDA spectrum set in the difference set is empty.

[0036] Specifically, the amplitude of the linear acceleration data is compared. If the amplitude of the change is lower than the corresponding lower threshold (first lower threshold), the influence of linear motion is considered to be very small and its influence is not considered. That is, the linear acceleration spectrum set is an empty set (the first 3 spectrum values ​​of the current acquisition period are removed), Facce = {}; Compare the change amplitude of the rotational acceleration data. If the change amplitude is lower than the corresponding lower threshold (second lower threshold), the influence of rotational motion is considered to be very small and its influence is not considered. That is, the rotational acceleration spectrum set is an empty set (removing the first 3 spectrum values ​​of the current acquisition period), Fgyro = {}; Compare the amplitude of changes in the EDA signal (electrical activity signal on the surface of human skin). If the amplitude of changes is lower than the lower threshold (third lower threshold), it is considered that the relative motion between the detection device and the skin surface has little effect and its effect is not considered. That is, the EDA spectrum set is an empty set (the first 3 spectrum values ​​of the current acquisition period are removed), Feda = {}.

[0037] Preferably, after converting the acquired PPG signal into a PPG digital signal in step S1, the method further includes step S21, which preprocesses the PPG digital signal, specifically, as follows: Figure 4 As shown, step S21 includes: S211, acquire the initial sampled value of the PPG digital signal and the corresponding control parameters for sampling; the control parameters include the operating current I of the light source module. led The input bias current I of the amplifier in the analog front-end control chip offset Gain factor K gain The light source module is used to irradiate the blood in the capillaries, and the analog front-end control chip is used to adjust the brightness of the light source module. S212, based on the corresponding sampling control parameters, the initial sampled value Vs of the PPG digital signal is normalized to obtain the normalized sampled value V of the PPG digital signal. unify ; Specifically, the PPG sampling data is processed by removing control parameter factors and then undergoing data standardization. The standardization process is as follows: V unify = (V s / K gain I offset ) / I led ; Among them, V unify V represents the initial sampled value of the PPG digital signal and the sampled value of the PPG digital signal after the current control parameters have been standardized. s K represents the initial sample value of the PPG digital signal in this sampling. gain I represents the gain factor of the amplifier in the current analog front-end control chip. led I represents the operating current of the current wavelength generation module. offset This is the input bias current of the amplifier in the current analog front-end control chip.

[0038] S213, Based on the changes in control parameters during the sampling process of the PPG digital signal, set the compensation amount V. diff ; Specifically, if the control parameters remain unchanged, the acquired data is continuous. However, when dynamically adjusting the control parameters, due to hardware performance parameter deviations, using different control parameters to acquire the same signal results in step jumps in the acquired data, requiring data splicing. The splicing scheme involves setting a compensation amount V. diff Each collected value is standardized before the compensation amount V is subtracted. diff Compensation is performed when the control parameters remain unchanged; this compensation amount V diff The value remains unchanged if the control parameters are not changed; when the control parameters change, this compensation value V is updated. diff The value of the compensation amount V. diff The update process involves, after changing the control parameters, obtaining the control parameters for adjusting the sampling circuit, so that the sampled value V at this time can be used... s (n) V after unification unify1 (n+1) equals a preset sampling standard value V stand If the circuit has no hardware performance parameter deviations, then the sampled value after changing the control parameters and undergoing standardization should be equal to V. stand However, due to deviations in the hardware performance parameters of the circuit, V at this time... unify(n+1) is not equal to V stand The difference between them is the compensation amount V. diff ,Right now, V diff (n+1)= V unify (n+1) V stand ; Among them, V unify (n+1) is the initial sample value V of the first PPG digital signal after the control parameters are adjusted. s The sampled values ​​of V after the adjusted control parameters have been standardized. stand The initial sampled value of the PPG digital signal before control parameter adjustment and the sampled value after the control parameters have been standardized. That is: V unify = (V s / K gain I offset ) / I led ; V unify (n+1)= (V s / K gain I offset ) / I led ; V stand =V unify1 (n)= (V s / K gain I offset ) / I led .

[0039] S214, the sampled values ​​V of the unified PPG digital signal unify With compensation amount V diff Perform interpolation to obtain the preprocessed PPG digital signal sample value V. ppg .

[0040] Data concatenation (difference processing) is the process of combining the current unified numerical value V with the original value. unify Compensation is performed using a compensation amount to ensure that there are no abrupt changes before and after altering the control parameters of the sampling circuit. The spliced ​​data is then used as the final calculation data and saved. The calculation formula is as follows: Vppg = V unify - V diff ; Among them, V ppg V represents the preprocessed PPG digital signal sample value. unify V represents the initial sampled value of the PPG digital signal and the sampled value of the PPG digital signal after the current control parameters have been standardized. diff This is the compensation amount after this sampling.

[0041] Preferably, after converting the acquired PPG signal into a PPG digital signal in step S1, the method further includes step S22, which involves converting the PPG digital signal into a digital signal based on its initial sample value V. s The amplitude of the change in sampled values ​​within the acquisition period, V a Dynamically adjust control parameters during PPG signal acquisition; such as Figure 5 As shown, based on the initial sample value V of the PPG digital signal... s The amplitude of the change in sampled values ​​within the acquisition period, V a Dynamic adjustment of control parameters during PPG signal acquisition includes: S221, Obtain the initial sample value V of the PPG digital signal. s ; S222, save the PPG sampling data within the most recent 0.5s; S223, find the maximum value V of the sampled value within the acquisition period (e.g., 0.5s). smax (Same as Vsmax) and minimum value V smin (Same as Vsmin); S224, the maximum value V of the sampled value smax and minimum value V smin Perform interpolation and calculate the amplitude V of the sampled value change within the acquisition period. a (Same as Va); That is, V a = V smax V smin .

[0042] S225, Compare the change amplitude V a Is it within the preset first effective range (maximum amplitude V)? amax Amplitude lower limit V amin ), or the initial sample value V s Is it within the preset second effective range (amplitude upper limit V)? smax Amplitude lower limit V smin If the amplitude V of the sampled value changes within the acquisition period a Not within the preset first valid range, or the initial sample value V sIf the value is not within the preset second valid range, proceed to step S226; otherwise, save the current sampled value and the corresponding control parameters, and perform the next sampling. Step S226: Dynamically adjust the control parameters during PPG signal acquisition to ensure that the amplitude V of the sampled value changes within the acquisition period. a and initial sample value V s The preset adjustment requirements are met, wherein the preset adjustment requirements are related to the amplitude V of the change in the sampled values ​​within the acquisition period. a The preset maximum amplitude V amax (Same as Vamax) and preset minimum amplitude V amin (Same as Vamin) geometric mean, and the initial sample value V s Within a preset second effective range. Preferably, after adjusting the control parameters, V... stand =(V s / K gain I offset ) / I led Among them, V stand The initial sampled value of the PPG digital signal before control parameter adjustment and the sampled value after the control parameters have been standardized, i.e., the goal of parameter adjustment is to utilize the sampled value V before parameter adjustment at this point. s (n) and the adjusted control parameter K gain (n+1), I offset (n+1), I led (n+1), the sampled value after standardization is equal to the preset sampling standard value V. stand .

[0043] Specifically, dynamically adjusting the control parameters during PPG signal acquisition includes: S2261, based on the preset maximum amplitude V within the acquisition period amax and preset minimum amplitude V amin Calculate the magnitude of the target change; Specifically, V a (n+1) = sqrt(V amax V amin ); where V a (n+1) represents the target change magnitude, V amax V is the preset maximum amplitude value within the acquisition period. amin The preset minimum amplitude value within the acquisition period.

[0044] S2262, if the current change amplitude V a (n) is greater than the preset maximum amplitude Vamax At this time, reduce the gain factor K of the amplifier in the analog front-end control chip. gain Alternatively, simultaneously reduce the operating current I of the light source module. led If the current change amplitude V a (n) is less than the preset minimum amplitude value V amin At this time, increase the gain factor K of the amplifier in the analog front-end control chip. gain Alternatively, simultaneously increase the operating current I of the light source block. led ; Specifically, calculate the magnification K that needs to be adjusted. adj ; Specifically, K adj = V a (n+1) / V a (n) = sqrt(V amax V amin ) / V a (n); Among them, V a (n) represents the amplitude of the current acquisition cycle change.

[0045] Specifically, on the one hand, if the current change amplitude V a (n) is greater than the preset maximum amplitude V amax At this time, reduce the gain factor K of the amplifier in the analog front-end control chip. gain Alternatively, simultaneously reduce the operating current I of the light source module. led ; Specifically, if the preset adjustment requirements can be achieved simply by adjusting the amplifier gain, then only the amplifier gain should be adjusted: That is, if K adj K gain (n)>K gainmin K gainmin This is the minimum gain value of the amplifier; Then K gain (n+1) = K adj K gain (n); that is, K gain (n+1)=( ) / V a (n) K gain (n); I led (n+1) = I led (n); Among them, K gain(n+1) represents the gain factor of the amplifier in the analog front-end control chip after adjusting the control parameters, V a (n) represents the magnitude of the change in the current sampled value within the acquisition period, V amax V is the preset maximum amplitude. amin K is the preset minimum amplitude value. gain (n) represents the gain factor of the amplifier in the analog front-end control chip before adjusting the control parameters, I led (n+1) represents the operating current of the light source module after adjusting the control parameters, I led (n) represents the operating current of the light source module before adjusting the control parameters; If adjusting the amplifier gain alone cannot achieve the target, in addition to adjusting the gain factor K of the amplifier in the analog front-end control chip... gain In addition, the operating current I of the LED light-emitting diode (light source module) also needs to be adjusted. led : That is, if K adj K gain (n) <K gainmin K gainmin This is the minimum gain value of the amplifier; Then K gain (n+1) = K gainmin ; I led (n+1) = K adj K gain (n) / K gainmin I led (n); i.e. I led (n+1)=( ) / V a (n) K gain (n) / K gain (n+1)) I led (n).

[0046] On the other hand, if the current change magnitude V a (n) is less than the preset minimum amplitude value V amin At this time, increase the gain factor K of the amplifier in the analog front-end control chip. gain Alternatively, simultaneously increase the operating current I of the light source module. led ; Specifically, if the current change magnitude V a (n) <V a When the current is min, it is necessary to increase the amplifier gain or increase the LED operating current I. led; Specifically, if the goal can be achieved simply by adjusting the amplifier's gain, then only the amplifier's gain should be adjusted: That is, if K adj K gain (n) <K gainmax K gainmax This is the amplifier's maximum gain value; Then K gain (n+1) = K adj K gain (n); I led (n+1) = I led (n); If adjusting the amplifier gain alone cannot achieve the target amplitude change, in addition to adjusting the amplifier gain, the operating current I of the LED must also be adjusted. led : That is, if K adj K gain (n)>K gainmax K gainmax This is the amplifier's maximum gain value; Then K gain (n+1) = K gainmax ; I led (n+1) = K adj K gain (n) / K gainmax I led (n), i.e. I led (n+1)=( ) / V a (n) K gain (n) / K gain (n+1)) I led (n); Among them, K gain (n+1) represents the gain factor of the amplifier in the analog front-end control chip after adjusting the control parameters, V a (n) represents the magnitude of the change in the current sampled value within the acquisition period, V amax V is the preset maximum amplitude. amin K is the preset minimum amplitude value. gain (n) represents the gain factor of the amplifier in the analog front-end control chip before adjusting the control parameters, I led(n+1) represents the operating current of the light source module after adjusting the control parameters, I led (n) represents the operating current of the light source module before adjusting the control parameters.

[0047] S2263, based on the adjusted gain factor K of the amplifier in the analog front-end control chip. gain (n+1) and the operating current I of the light source module led (n+1), calculate the adjusted input bias current I of the amplifier in the analog front-end control chip. offset (n+1); Specifically, if the amplitude parameter has already been adjusted, there is no need to adjust the offset parameter again. If the amplitude of the sampled data within 0.5 seconds does not exceed the limit, then compare whether the sampled values ​​within 0.5 seconds exceed the range in amplitude. That is, if the maximum sampled value V... smax (Same as Vsmax) is greater than the upper limit of the sampled value V max (Same as Vmax), or, minimum sample value V smin (Same as Vsmin) less than the lower limit of the sampling value V min (Same as Vmin) Then it is necessary to adjust the input bias current I of the amplifier in the analog front-end control chip. offset ; The goal of adjusting the offset parameter is to utilize the current sampled value V s (n) and the adjusted control parameter K gain (n+1), I offset (n+1), I led (n+1), after standardization, the sampled value is equal to the standard value V. stand ,Right now: (V s (n) / K gain (n+1) - I offset (n+1)) / I led (n+1) = V stand ; Since the amplitude of the sampled value meets the requirements, the amplifier gain and the operating current of the LED remain unchanged, that is: K gain (n+1) = K gain (n); I led (n+1) = I led (n); Calculate and adjust the input bias current I of the amplifier in the analog front-end control chip. offset (n+1): I offset (n+1) = (V s (n) / K gain(n+1)) (V stand I led (n+1)); Among them, I offset (n+1) represents the adjusted input bias current of the amplifier in the analog front-end control chip, V s (n) represents the initial sample value V of the PPG digital signal before adjustment. s K gain (n+1) represents the adjusted gain of the amplifier in the analog front-end control chip, V stand As a preset sampling standard value, I led (n+1) represents the adjusted operating current of the light source module.

[0048] S2264 will adjust the gain factor K of the amplifier in the analog front-end control chip. gain (n+1) Input bias current I offset (n+1) Operating current I of the light source module led (n+1) By setting the registers inside the analog front-end control chip, the adjusted control parameters take effect.

[0049] Determine whether the control parameters of the sampling circuit have changed during this processing. If they have changed, save the changed control parameters and set the registers inside the AFE (Analog Front End) control chip via the bus to make the changed control parameters take effect; then continue to wait for the next sampling operation.

[0050] Preferably, after determining the adjusted control parameters, the method further includes: S2265, after the next sampling, based on the sampled value V after the next unification process. unify (n+1) Set the compensation amount V for the next sampling. diff (n+1), specifically: V diff (n+1) = V unify (n+1) V stand ; Among them, V diff (n+1) represents the compensation amount after the next sampling, V unify (n+1) represents the initial sample value of the first PPG digital signal after control parameter adjustment and the sample value after the adjusted control parameters have been standardized, V stand The preset sampling standard value, i.e., V stand = (V s / K gain I offset ) / I led .

[0051] This embodiment simultaneously acquires PPG (photoplethysmography) signals, linear acceleration signals, rotational acceleration signals, and EDA (electrodermal activity) signals. This allows for the filtering of changes in capillary blood flow caused by movement, as well as the impact of relative motion between the measuring device and the human body surface on PPG signal acquisition. This enables the calculation of changes in capillary blood flow caused by heartbeat and respiratory activity, thus achieving the function of measuring heart rate and respiratory rate data even during exercise. Furthermore, considering the wide dynamic range of PPG signals, an algorithm is provided to comprehensively control LED luminous intensity, input bias current, and amplifier gain to adapt to signal changes. This ensures that the signal never exceeds the circuit's measurement range during detection, avoiding signal distortion. When control parameters change and cause a step jump, a data stitching algorithm is also provided, making the data more coherent and improving the accuracy and precision of data calculation.

[0052] This embodiment can be used to detect a user's heart rate and respiratory rate data during fitness or sports training, providing support for the user's fitness or training activities.

[0053] In this invention, PPG signals, linear acceleration signals, rotational acceleration signals, and electrical activity signals from the human skin surface are collected and converted. Fourier transforms are performed on the PPG digital signals, linear acceleration digital signals, rotational acceleration digital signals, and electrical activity signals from the human skin surface, respectively, to form PPG spectrum sets, linear acceleration spectrum sets, rotational acceleration spectrum sets, and EDA spectrum sets. The difference between the PPG spectrum sets and the union spectrum sets is calculated to obtain a set of calculated spectrum related to heart rate and respiratory rate. Within the frequency band of heart rate, the frequency with the largest energy amplitude in the calculated spectrum set is used as heart rate data; similarly, within the frequency band of respiratory rate, the frequency with the largest energy amplitude in the calculated spectrum set is used as respiratory rate data. This effectively solves the problem of low reliability of heart rate (or respiratory rate) detection data caused by existing technologies, and effectively improves the reliability of heart rate (or respiratory rate) detection data.

[0054] The technical solution of this invention integrates PPG spectrum set, linear acceleration spectrum set, rotational acceleration spectrum set, and EDA spectrum set to determine heart rate (or respiratory rate) detection data. It can filter out the signal of changes in capillary blood flow caused by exercise, as well as the influence of the relative motion between the measuring device and the human body surface on PPG signal acquisition. Thus, it calculates the signal of changes in capillary blood flow caused by heartbeat and respiratory activity, thereby achieving the function of measuring heart rate and respiratory rate data even in the exercise state.

[0055] In the technical solution of this invention, if the amplitude of the frequency in the linear acceleration spectrum set is less than the first preset amplitude threshold, the linear acceleration spectrum set in the difference set is empty; if the amplitude of the frequency in the rotational acceleration spectrum set is less than the second preset amplitude threshold, the rotational acceleration spectrum set in the difference set is empty; if the amplitude of the frequency in the EDA spectrum set is less than the third preset amplitude threshold, the EDA spectrum set in the difference set is empty. Only when the amplitude of the corresponding influencing signal is greater than the corresponding threshold will the influencing signal be considered for the change signal of blood flow in capillaries, thereby improving the adaptability of heart rate (or respiratory rate) detection data.

[0056] The technical solution of this invention can also preprocess the PPG digital signal; based on the control parameters corresponding to the sampling, the initial sample value V of the PPG digital signal is... s The PPG digital signal is then standardized to obtain the sampled value V. unify Based on the changes in control parameters during the sampling process of the PPG digital signal, set the compensation amount V. diff The sampled value V of the unified PPG digital signal. unify With compensation amount V diff Perform interpolation to obtain the preprocessed PPG digital signal sample value V. ppg This further improves the reliability of heart rate (or respiratory rate) detection data.

[0057] The technical solution of this invention can also dynamically adjust the control parameters during the PPG signal acquisition process; and obtain the initial sample value V of the PPG digital signal. s Find the maximum value V of the sampled values ​​within the acquisition period. smax and minimum value V smin ; the maximum value V of the sampled value smax and minimum value V smin Perform interpolation and calculate the amplitude V of the sampled value change within the acquisition period. a If the amplitude V of the sampled value changes within the acquisition period a Not within the preset first valid range, or the initial sample value V s If the signal is not within the preset second effective range, the control parameters during PPG signal acquisition are dynamically adjusted to adjust the amplitude V of the sampled value change within the acquisition period. a It meets the preset requirements and further improves the reliability of heart rate (or respiratory rate) detection data.

[0058] Example 2 like Figure 2As shown, the present invention also provides a detection system for sampling PPG signals during motion, comprising: a light source module, a light sensing module, an analog front-end control chip (AFE), an inertial sensor (GSensor), an EDA sensor, and a microcontroller (MCU). The light source module is used to output light of a preset wavelength for irradiating capillaries; the light sensing module is used to receive light reflected from blood in capillaries and collect PPG signals that change with the intensity of reflected light during motion; the analog front-end control chip is used to adjust the output current to control the brightness of the light source module; and to receive and convert the collected PPG signals into PPG digital signals; the inertial sensor is used to collect and convert linear acceleration and rotational acceleration signals of human motion into linear acceleration digital signals and rotational acceleration digital signals; the EDA sensor is used to collect EDA signals caused by the relative motion between the sensor and the human body surface; and the microcontroller is used to acquire PPG digital signals, linear acceleration digital signals, rotational acceleration digital signals, and electrical activity signals on the human skin surface, respectively, and to determine heart rate and respiratory rate data based on the spectral data of PPG digital signals, linear acceleration digital signals, rotational acceleration digital signals, and EDA signals.

[0059] Specifically, the light source module includes a light-emitting diode (LED1) for emitting light of a preset first wavelength and a light-emitting diode (LED2) for emitting light of a preset second wavelength; the light sensing module includes a photodiode (PD1) and a photodiode (PD2), wherein photodiode (PD1) receives the preset first wavelength light reflected from blood in capillaries and acquires a first PPG signal adjusted by the intensity of the reflected preset first wavelength light during motion; photodiode (PD2) receives the preset second wavelength light reflected from blood in capillaries and acquires a second PPG signal adjusted by the intensity of the reflected preset second wavelength light during motion; the inertial sensor includes an accelerometer (3-axis accelerometer). The system includes an accelerometer (3-axis gyroscope sensor) and a gyroscope sensor (3-axis gyroscope sensor). The accelerometer is used to collect and convert the linear acceleration signal of human motion into a linear acceleration digital signal, and the gyroscope sensor is used to collect and convert the rotational acceleration signal of human motion into a rotational acceleration digital signal. The EDA sensor includes EDA electrode 1 and EDA electrode 2, which are placed on the skin surface. The voltage signal output by the constant voltage signal source is applied to the user's skin surface through EDA electrode 1 and EDA electrode 2. The skin impedance between EDA electrode 1 and EDA electrode 2 and the sampling resistor form a voltage divider circuit, which is used to collect the EDA signal caused by the relative motion between the sensor and the human body surface.

[0060] Specifically, the PPG sensor (photosensitive module) collects PPG (photoplethysmography) signals of the human body in motion. However, the PPG signals actually collected not only include the changes in blood flow in capillaries caused by heartbeat and breathing activities, but also the changes in blood flow in capillaries caused by human movement. In addition, it also includes the influence of the relative motion between the measuring device and the human body surface caused by movement on the PPG signal collection. Inertial sensors collect linear acceleration and rotational acceleration signals of human motion during motion. An EDA (electrodermal activity) sensor has two electrodes that are attached to the skin surface. A small voltage signal is applied between the two electrodes, and the current passing between the electrodes is detected to calculate the contact resistance. The change in this resistance is used to acquire the change signal of the relative motion between the measuring device and the human body surface.

[0061] like Figure 2 As shown, the light source module includes LEDs 1 and 2, which emit red and green light of specific wavelengths to illuminate capillaries; photodiodes PD1 and PD2, which receive light reflected from blood within capillaries and output different currents depending on the intensity of the reflected light, used to acquire PPG signals; an analog front-end control chip (AFE), with a built-in LED driver circuit connected to LEDs 1 and 2, can adjust the output current to control the brightness of the LEDs. The AFE also has a built-in input amplifier, with its input connected to photodiodes PD1 and PD2 to receive PPG signals. The input amplifier can adjust the bias current of the input signal and the amplifier gain, and finally converts the signal into a digital signal via an ADC; the inertial sensor (GSensor) incorporates a 3-axis accelerometer and a 3-axis gyroscope to acquire the linear acceleration and deceleration of human motion. The rotational acceleration signal, with its built-in ADC, converts the acquired analog signal into a digital signal; EDA electrode 1 and EDA electrode 2 are two metal electrodes that are attached to the user's skin during use; a constant voltage signal source outputs a fixed voltage signal, which is applied to the user's skin through EDA electrode 1 and EDA electrode 2. The skin impedance between EDA electrode 1 and EDA electrode 2 and the standard sampling resistor form a voltage divider circuit; the microcontroller (MCU) is connected to the analog front-end control chip (AFE) and reads the acquired PPG digital signal through the interface circuit; the microcontroller (MCU) is connected to the inertial sensor (GSensor) and reads the acquired linear acceleration and rotational acceleration digital signals through the interface circuit; the microcontroller (MCU) is connected to EDA electrode 1 and EDA electrode 2, acquires the level signals of these two electrodes, and converts them into digital signals through the internal ADC.

[0062] In this invention, PPG signals, linear acceleration signals, rotational acceleration signals, and electrical activity signals from the human skin surface are collected and converted. Fourier transforms are performed on the PPG digital signals, linear acceleration digital signals, rotational acceleration digital signals, and electrical activity signals from the human skin surface, respectively, to form PPG spectrum sets, linear acceleration spectrum sets, rotational acceleration spectrum sets, and EDA spectrum sets. The difference between the PPG spectrum sets and the union spectrum sets is calculated to obtain a set of calculated spectrum related to heart rate and respiratory rate. Within the frequency band of heart rate, the frequency with the largest energy amplitude in the calculated spectrum set is used as heart rate data; similarly, within the frequency band of respiratory rate, the frequency with the largest energy amplitude in the calculated spectrum set is used as respiratory rate data. This effectively solves the problem of low reliability of heart rate (or respiratory rate) detection data caused by existing technologies, and effectively improves the reliability of heart rate (or respiratory rate) detection data.

[0063] The technical solution of this invention integrates PPG spectrum set, linear acceleration spectrum set, rotational acceleration spectrum set, and EDA spectrum set to determine heart rate (or respiratory rate) detection data. It can filter out the signal of changes in capillary blood flow caused by exercise, as well as the influence of the relative motion between the measuring device and the human body surface on PPG signal acquisition. Thus, it calculates the signal of changes in capillary blood flow caused by heartbeat and respiratory activity, thereby achieving the function of measuring heart rate and respiratory rate data even in the exercise state.

[0064] In the technical solution of this invention, if the amplitude of the frequency in the linear acceleration spectrum set is less than the first preset amplitude threshold, the linear acceleration spectrum set in the difference set is empty; if the amplitude of the frequency in the rotational acceleration spectrum set is less than the second preset amplitude threshold, the rotational acceleration spectrum set in the difference set is empty; if the amplitude of the frequency in the EDA spectrum set is less than the third preset amplitude threshold, the EDA spectrum set in the difference set is empty. Only when the amplitude of the corresponding influencing signal is greater than the corresponding threshold will the influencing signal be considered for the change signal of blood flow in capillaries, thereby improving the adaptability of heart rate (or respiratory rate) detection data.

[0065] The technical solution of this invention can also preprocess the PPG digital signal; based on the control parameters corresponding to the sampling, the initial sample value V of the PPG digital signal is... s The PPG digital signal is then standardized to obtain the sampled value V. unify Based on the changes in control parameters during the sampling process of the PPG digital signal, set the compensation amount V. diff The sampled value V of the unified PPG digital signal. unify With compensation amount V diffPerform interpolation to obtain the preprocessed PPG digital signal sample value V. ppg This further improves the reliability of heart rate (or respiratory rate) detection data.

[0066] The technical solution of this invention can also dynamically adjust the control parameters during the PPG signal acquisition process; and obtain the initial sample value V of the PPG digital signal. s Find the maximum value V of the sampled values ​​within the acquisition period. smax and minimum value V smin ; the maximum value V of the sampled value smax and minimum value V smin Perform interpolation and calculate the amplitude V of the sampled value change within the acquisition period. a If the amplitude V of the sampled value changes within the acquisition period a Not within the preset first valid range, or the initial sample value V s If the signal is not within the preset second effective range, the control parameters during PPG signal acquisition are dynamically adjusted to adjust the amplitude V of the sampled value change within the acquisition period. a It meets the preset requirements and further improves the reliability of heart rate (or respiratory rate) detection data.

[0067] While the specific embodiments of the present invention have been described above in conjunction with the accompanying drawings, this is not intended to limit the scope of protection of the present invention. Those skilled in the art should understand that various modifications or variations that can be made by those skilled in the art without creative effort based on the technical solutions of the present invention are still within the scope of protection of the present invention.

Claims

1. A detection method using PPG signal sampling in motion, characterized in that, include: The PPG signal, which reflects the change in light intensity of blood within capillaries during motion, is acquired and converted into a digital PPG signal. The digital PPG signal is then preprocessed. The preprocessing includes: Acquire the initial sampled value of the PPG digital signal and the corresponding control parameters for sampling; the control parameters include the operating current I of the light source module. led The input bias current I of the amplifier in the analog front-end control chip offset Gain factor K gain The light source module is used to irradiate the blood in the capillaries, and the analog front-end control chip is used to adjust the brightness of the light source module. Based on the corresponding sampling control parameters, the initial sampled value V of the PPG digital signal is... s The PPG digital signal is then standardized to obtain the sampled value V. unify ; Based on the changes in control parameters during the sampling process of the PPG digital signal, the compensation amount V is set. diff ; The sampled value V of the unified PPG digital signal unify With compensation amount V diff Perform interpolation to obtain the preprocessed PPG digital signal sample value V. ppg ; The linear acceleration and rotational acceleration signals of human motion are collected, and the collected linear acceleration and rotational acceleration signals of human motion are converted into linear acceleration digital signals and rotational acceleration digital signals. The electrical activity signals on the surface of human skin are collected to detect the relative motion between the sensor and the human body surface; Fourier transforms were performed on the PPG digital signal, linear acceleration digital signal, rotational acceleration digital signal, and electrical activity signal from the human skin surface, respectively. The spectrum with the highest energy proportion was selected from each, forming the corresponding PPG spectrum set, linear acceleration spectrum set, rotational acceleration spectrum set, and EDA spectrum set; specifically including: Perform a Fourier transform on the PPG digital signal to find the first number of spectral values ​​with the highest energy amplitude. Save the frequency, amplitude, and phase of the first number of spectra to form a PPG spectrum set. Perform a Fourier transform on the linear acceleration digital signal, find the second-to-last number of spectral values ​​with the highest energy amplitude, and save the frequency, amplitude, and phase values ​​of these second-to-last number of spectra to form a linear acceleration spectrum set. Perform a Fourier transform on the rotational acceleration digital signal and identify the signals with the highest energy amplitudes. The first second number of spectral values ​​are stored, along with their frequencies, amplitudes, and phases, forming a rotational acceleration spectrum set. Perform a Fourier transform on the digital signal of electrical activity on the surface of human skin, find the second-to-last number of spectral values ​​with the highest energy amplitude, and save the frequency, amplitude and phase values ​​of these second-to-last number of spectra to form an EDA signal spectrum set. The difference between the PPG spectrum set and the union spectrum set is calculated to obtain the calculated spectrum set related to heart rate and respiratory rate. The union spectrum set is the union of the linear acceleration spectrum set, the rotational acceleration spectrum set, and the EDA spectrum set. In the frequency band where the heart rate is located, the frequency with the largest energy amplitude in the calculated spectrum set is used as the heart rate data. In the frequency band where the respiratory rate is located, the frequency with the largest energy amplitude in the calculated spectrum set is used as the respiratory rate data.

2. The detection method using PPG signal sampling in motion state according to claim 1, characterized in that, If the amplitude of the linear acceleration digital signal change is less than the first preset amplitude threshold, the linear acceleration spectrum set in the difference set is empty; if the amplitude of the rotational acceleration digital signal change is less than the second preset amplitude threshold, the rotational acceleration spectrum set in the difference set is empty. If the amplitude of the change in electrical activity signal on the surface of human skin is less than the third preset amplitude threshold, then the EDA spectrum set in the difference set is empty.

3. The detection method using PPG signal sampling under motion conditions according to claim 1, characterized in that, Based on the corresponding sampling control parameters, the initial sampled value Vs of the PPG digital signal is normalized to obtain the normalized sampled value V of the PPG digital signal. unify Specifically: V unify = (V s / K gain I offset ) / I led ; Among them, V unify V represents the initial sampled value of the PPG digital signal and the sampled value of the PPG digital signal after the current control parameters have been standardized. s K represents the initial sample value of the PPG digital signal in this sampling. gain I represents the gain factor of the amplifier in the current analog front-end control chip. led I represents the operating current of the current wavelength generation module. offset This is the input bias current of the amplifier in the current analog front-end control chip; The sampled value V of the unified PPG digital signal unify With compensation amount V diff Perform interpolation to obtain the preprocessed PPG digital signal sample value V. ppg Specifically: V ppg = V unify - V diff ; Among them, V ppg V represents the sampled value of the preprocessed PPG digital signal. diff This is the compensation amount after this sampling.

4. The detection method using PPG signal sampling under motion conditions according to claim 1, characterized in that, After converting the acquired PPG signal into a PPG digital signal, the process also includes: based on the initial sample value V of the PPG digital signal. s The amplitude of the change in sampled values ​​within the acquisition period, V a The control parameters are dynamically adjusted during the PPG signal acquisition process; the initial sample value V of the PPG digital signal is used as the basis for this adjustment. s The amplitude of the change in sampled values ​​within the acquisition period, V a Dynamic adjustment of control parameters during PPG signal acquisition includes: Obtain the initial sample value V of the PPG digital signal s ; Find the maximum value V of the sampled values ​​within the acquisition period. smax and minimum value V smin ; The maximum value V of the sampled value smax and minimum value V smin Perform interpolation and calculate the amplitude V of the sampled value change within the acquisition period. a ; If the amplitude of the change in the sampled value during the acquisition period is V a Not within the preset first valid range, or the initial sample value V s If the signal is not within the preset second effective range, the control parameters during PPG signal acquisition will be adjusted to adjust the amplitude V of the sampled value change within the acquisition period. a and initial sample value V s The preset adjustment requirements are met, wherein the preset adjustment requirements are related to the amplitude V of the change in the sampled values ​​within the acquisition period. a The preset maximum amplitude V amax and preset minimum amplitude V amin The geometric mean, and the initial sample value V s Within the preset second effective range.

5. The detection method using PPG signal sampling in motion state according to claim 4, characterized in that, Adjusting control parameters during PPG signal acquisition specifically includes: Based on the preset maximum amplitude V within the acquisition period amax and preset minimum amplitude V amin Calculate the magnitude of the target change; If the current change magnitude V a (n) is greater than the preset maximum amplitude V amax At this time, reduce the gain factor K of the amplifier in the analog front-end control chip. gain Alternatively, simultaneously reduce the operating current I of the light source module. led If the current change amplitude V a (n) is less than the preset minimum amplitude value V amin At this time, increase the gain factor K of the amplifier in the analog front-end control chip. gain Alternatively, simultaneously increase the operating current I of the light source block. led ; According to the adjusted gain factor K of the amplifier in the analog front-end control chip gain (n+1) and the operating current I of the light source module led (n+1), calculate the adjusted input bias current I of the amplifier in the analog front-end control chip. offset (n+1); Adjust the gain factor K of the amplifier in the analog front-end control chip. gain (n+1) Input bias current I offset (n+1) Operating current I of the wavelength generation module led (n+1) By setting the registers inside the analog front-end control chip, the adjusted control parameters take effect.

6. The detection method using PPG signal sampling in motion state according to claim 5, characterized in that, When only the gain factor K of the amplifier in the analog front-end control chip is adjusted gain When the preset adjustment requirements are met, only the gain factor K of the amplifier in the analog front-end control chip is adjusted. gain The operating current I of the light source module led The following remains unchanged: K gain (n+1)=( ) / V a (n) K gain (n); I led (n+1)=I led (n); Among them, K gain (n+1) represents the gain factor of the amplifier in the analog front-end control chip after adjusting the control parameters, V a (n) represents the magnitude of the change in the current sampled value within the acquisition period, V amax V is the preset maximum amplitude. amin K is the preset minimum amplitude value. gain (n) represents the gain factor of the amplifier in the analog front-end control chip before adjusting the control parameters, I led (n+1) represents the operating current of the light source module after adjusting the control parameters, I led (n) represents the operating current of the light source module before adjusting the control parameters; When only the gain factor K of the amplifier in the analog front-end control chip is adjusted gain If the preset adjustment requirements cannot be met, then adjust the gain factor K of the amplifier in the analog front-end control chip. gain At the same time, adjust the operating current I of the light source module. led Specifically: If the current change magnitude V a (n) is less than the preset minimum amplitude value V amin Time: K gain (n+1)=K gainmax Or, if the current change magnitude V a (n) is greater than the preset maximum amplitude V amax Time: K gain (n+1)=K gainmin Among them, K gainmax To simulate the maximum gain of the amplifier in the front-end control chip, K gainmin To simulate the minimum gain of the amplifier in the front-end control chip; Adjusted operating current I of the light source module led (n+1) specifically refers to: I led (n+1)=( ) / V a (n) K gain (n) / K gain (n+1)) I led (n)。 7. The detection method using PPG signal sampling in motion state according to claim 5, characterized in that, According to the adjusted gain factor K of the amplifier in the analog front-end control chip gain (n+1) and the operating current I of the light source module led (n+1), calculate the adjusted input bias current I of the amplifier in the analog front-end control chip. offset (n+1) specifically refers to: I offset (n+1) =(V s (n) / K gain (n+1)) (V stand I led (n+1)); Among them, I offset (n+1) represents the adjusted input bias current of the amplifier in the analog front-end control chip, V s (n) represents the initial sample value V of the PPG digital signal before adjustment. s K gain (n+1) represents the adjusted gain of the amplifier in the analog front-end control chip, V stand As a preset sampling standard value, I led (n+1) represents the operating current of the adjusted wavelength generation module.

8. The detection method using PPG signal sampling in motion state according to claim 5, characterized in that, After determining the adjusted control parameters, the following steps are also included: After the next sampling, based on the sampled value V after the next unification process. unify (n+1) Set the compensation amount V for the next sampling. diff (n+1), specifically: V diff (n+1) = V unify (n+1) V stand ; Among them, V diff (n+1) represents the compensation amount after the next sampling, V unify (n+1) represents the initial sample value of the first PPG digital signal after control parameter adjustment and the sample value after the adjusted control parameters have been standardized, V stand This is the preset sampling standard value.

9. A detection system that utilizes PPG signal sampling during motion, characterized in that, include: The system comprises a light source module, a light sensing module, an analog front-end control chip, an inertial sensor, an EDA sensor, and a microcontroller. The light source module outputs light of a preset wavelength for irradiating capillaries. The light sensing module receives light reflected from blood within capillaries and collects PPG signals that change with the intensity of reflected light during motion. The analog front-end control chip adjusts the output current to control the brightness of the light source module and receives and converts the collected PPG signals into digital PPG signals. The inertial sensor collects and converts linear and rotational acceleration signals of human motion into digital linear and rotational acceleration signals. The EDA sensor collects electrical activity signals from the surface of human skin to detect the relative motion between the sensor and the human surface. The microcontroller executes a detection method using PPG signal sampling during motion, as described in any one of claims 1-8.

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