Backrest type millimeter wave radar heart rate monitoring system and method

Abstract

The invention discloses a backrest type millimeter wave radar heart rate monitoring system and method, relates to the technical field of heart rate monitoring, and solves the problems that most of the existing heart monitoring technologies are contact type measurement, and the methods are poor in measurement accuracy due to insufficient comfort, sensitivity to the use environment and the like. And long-term continuous heart activity monitoring of the driver during driving is difficult to realize. The method comprises the following steps: acquiring an echo signal formed by reflecting a frequency-modulated continuous wave signal through a target position; analyzing the echo signal to obtain a displacement curve; performing separation processing on the displacement curve to obtain respiratory frequency and heartbeat frequency; whether early warning is carried out or not is judged based on the breathing frequency and the heartbeat frequency, and the technical problem is solved.

Description

Technical Field

[0001] The present invention belongs to the field of heart rate monitoring, and specifically relates to a backrest type millimeter wave radar heart rate monitoring system and method. Background Art

[0002] When a driver is working, a great deal of energy is consumed, and the brain is in a state of long-term overload operation. Generally, the physiological, psychological, and fatigue-related disease states of a driver do not show obvious pathological manifestations. In particular, drivers suffering from cardiovascular diseases are not easily detected under normal conditions. Early-onset cardiovascular diseases can be effectively prevented through timely diagnosis and treatment. Therefore, long-term continuous monitoring of cardiac activity is crucial for the early detection of diseases.

[0003] With the continuous development of vehicle intelligence, it has become possible to provide all-round vital sign monitoring for drivers. During driving, the driver's attention is highly concentrated, and the best detection method is non-contact measurement without the driver's intervention. Most existing cardiac monitoring technologies are contact measurements. Due to reasons such as insufficient comfort and sensitivity to the use environment, it is difficult to achieve long-term continuous monitoring of cardiac activity when the driver is driving.

[0004] Therefore, the present invention proposes a backrest type millimeter wave radar heart rate monitoring system and method to solve the above problems. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems existing in the prior art; for this purpose, the present invention proposes a backrest type millimeter wave radar heart rate monitoring system and method, which are used to solve the technical problem that most existing cardiac monitoring technologies are contact measurements, and it is difficult to achieve long-term continuous monitoring of cardiac activity when the driver is driving due to reasons such as insufficient comfort and sensitivity to the use environment.

[0006] To achieve the above object, the first aspect of the present invention provides a backrest type millimeter wave radar heart rate monitoring system, including: a data acquisition module, a data analysis module, and a monitoring and warning module;

[0007] The data acquisition module: acquires the echo signal formed by the reflection of the frequency modulated continuous wave signal through the target position;

[0008] The data analysis module: obtains a displacement curve by analyzing the echo signal; obtains the respiration frequency and the heart rate by separating the displacement curve;

[0009] The monitoring and warning module: determines whether to give a warning based on the respiration frequency and the heart rate.

[0010] Preferably, the acquisition of the echo signal formed by the reflection of the frequency modulated continuous wave signal through the target position includes:

[0011] A frequency modulated continuous wave signal is transmitted by a millimeter radar installed on the back of the driver's seat;

[0012] The receiver collects in real time the echo signal formed by the reflection of the frequency modulated continuous wave signal when passing through the target, and sends the collected echo signal to the data analysis module; wherein, the target refers to the chest or heart of the driver.

[0013] Preferably, the method for obtaining the displacement curve by analyzing the echo signal includes:

[0014] A1: Determine the frame period of collecting the echo signal;

[0015] A2: Obtain the target distance within each frame period, and extract the phase corresponding to the target distance; wherein, the target distance refers to the distance from the target to the radar;

[0016] A3: Generate a phase sequence that changes with time based on the phase corresponding to the target distance within each frame period;

[0017] A4: Obtain the phase change amount between each frame by performing a difference operation on adjacent phases in the phase sequence;

[0018] A5: Based on the relationship between the phase change amount and displacement: Convert the phase change amount into the displacement of the target to generate a displacement curve; wherein, ΔR is the displacement of the target, is the phase change amount, and λ is the operating wavelength of the radar.

[0019] It should be noted that the frame period refers to the time between the start of collecting one frame of data and the start of collecting the next frame of data. For example, the frame period is 50 ms, that is, the phase corresponding to the target distance is extracted every 50 ms;

[0020] The displacement curve is a curve of displacement changing with time; the conversion of the phase change amount into the displacement of the target, and the displacement of the target refers to the change amount of the distance of the target relative to the radar;

[0021] Due to the small movement of the target, the phase of the echo signal will change accordingly, and the phase difference reflects the relative displacement of the target along the radar line of sight;

[0022] Accumulate the phase differences of all frames to form a displacement curve that changes with time, and this curve contains information of all frequency components, including breathing and heartbeat.

[0023] Preferably, the method for obtaining the target distance within each frame period includes:

[0024] Mix the transmitted frequency modulated continuous wave signal and the received echo signal to generate an intermediate frequency signal;

[0025] The expression of the frequency-modulated continuous-wave signal is as follows:

[0026]

[0027] where f c is the carrier frequency of the signal, B is the signal bandwidth, T is the signal frequency-sweeping time, j is the imaginary unit, and t is the time variable;

[0028] The expression of the echo signal is as follows:

[0029]

[0030] where t d is the delay time of the echo signal, t d = 2R / c, R is the distance from the target to the radar, i.e., the target distance, and c is the speed of light;

[0031] The expression of the intermediate-frequency signal is as follows:

[0032]

[0033] where f b is the frequency of the intermediate-frequency signal, is the initial phase of the intermediate-frequency signal, and λ is the radar wavelength;

[0034] By performing analog-to-digital conversion on the intermediate-frequency signal, the digital signal corresponding to the intermediate-frequency signal is obtained;

[0035] By performing fast Fourier transform on the digital signal corresponding to the intermediate-frequency signal, the spectrogram in the range dimension is obtained; where the horizontal axis of the spectrogram represents the distance, and the vertical axis represents the signal amplitude;

[0036] The target distance is obtained based on the spectrogram in the range dimension.

[0037] Preferably, obtaining the target distance based on the spectrogram in the range dimension includes:

[0038] Searching on the spectrogram in the range dimension based on a preset target distance range, and selecting the maximum peak of the signal amplitude;

[0039] Extracting the frequency corresponding to the maximum peak and marking it as the target frequency;

[0040] Let f b be the target frequency, and the target distance is calculated through the formula It should be noted that the preset target distance range is set by experts in this field according to experience;

[0041]

[0042] ​After the intermediate-frequency signal is converted by analog-to-digital conversion (ADC), the time-domain signal is converted to the frequency domain through fast Fourier transform (FFT) to generate a range-dimensional spectrogram; the horizontal axis of the spectrogram corresponds to the range, and the vertical axis is the signal amplitude; since the reflected signals of targets at different ranges are manifested as different frequency components in the frequency domain, by searching for the amplitude peaks within a preset range (such as 0.5 - 1.2 meters), the position of the driver's chest can be locked; let f b be the frequency corresponding to the maximum peak, and substituting it into the formula the target range can be calculated.

[0043] Preferably, the separation processing of the displacement curve includes:

[0044] B1: Determine the target frequency range; wherein, the target frequency range includes: the respiration frequency range and the heartbeat frequency range;

[0045] B2: Based on the target frequency range, filter the displacement curve through a band-pass filter to obtain the target frequency signal; wherein, the target frequency sequence includes: the respiration frequency signal and the heartbeat frequency signal;

[0046] B3: Perform fast Fourier transform on the target frequency signal to obtain a spectrogram; wherein, the spectrogram includes: the respiration spectrogram and the heartbeat spectrogram;

[0047] B4: Obtain the target frequency based on the spectrogram; wherein, the target frequency includes: the respiration frequency and the heartbeat frequency.

[0048] It should be noted that since the frequency ranges of respiration and heartbeat are different (the respiration frequency is usually between 0.1 and 0.5 Hz, and the heartbeat frequency is between 0.8 and 2.5 Hz), by designing two different band-pass filters, the signals within these two frequency ranges can be extracted respectively.

[0049] Preferably, the obtaining of the target frequency based on the target spectrogram includes:

[0050] Perform frequency division processing on the spectrogram to obtain the target spectrogram; wherein, the target spectrogram includes: the target respiration spectrogram and the target heartbeat spectrogram;

[0051] Extract the frequency corresponding to the peak with the largest amplitude in the target respiration spectrogram as the respiration frequency; extract the frequency corresponding to the peak with the largest amplitude in the target heartbeat spectrogram as the heartbeat frequency.

[0052] Preferably, the method for performing frequency division processing on the spectrogram to obtain the target spectrogram includes:

[0053] Divide the spectrogram at a preset frequency interval to form several sub-bands;

[0054] Integrate the spectral values within the sub - frequency band to obtain the total energy of the current sub - frequency band;

[0055] Determine whether the total energy of the current sub - frequency band is greater than a preset threshold; if yes, it is determined as a valid frequency band; if no, it is determined as an invalid frequency band and the current frequency band is removed;

[0056] Retain the valid frequency bands in several sub - frequency bands of the spectrogram and remove the invalid frequency bands to obtain the target spectrogram.

[0057] It should be noted that the preset threshold is the energy level used to distinguish valid signals from noise or irrelevant signals, and is set by experts in the field according to the background noise level;

[0058] In spectral analysis, the magnitude of signal energy or amplitude is an important basis for distinguishing valid signals from background noise or interference. Valid signals usually have higher energy or amplitude, while the energy of noise and interference signals is relatively low; the setting of the threshold is to distinguish signals from noise. If the signal energy or amplitude within a certain frequency band exceeds the threshold, it indicates that the signal strength within this frequency band is sufficient to be considered a valid signal rather than background noise or interference.

[0059] Preferably, the determination of whether to give an early warning based on the breathing rate and heart rate includes:

[0060] C1: Determine whether the breathing rate is less than the lowest breathing threshold; if yes, generate a warning message; if no, go to step C2;

[0061] Determine whether the heart rate is less than the lowest heart rate threshold; if yes, generate a warning message; if no, go to step C3;

[0062] C2: Determine whether the breathing rate is greater than the highest breathing threshold; if yes, generate a warning message; if no, continue monitoring and judging;

[0063] C3: Determine whether the heart rate is greater than the highest heart rate threshold; if yes, generate a warning message; if no, continue monitoring and judging.

[0064] It should be noted that the lowest breathing threshold represents the critical point of too low breathing rate. Usually, the normal breathing rate range of adults is about 12 to 20 times per minute. If the detected breathing rate is lower than this lowest threshold (for example, less than 12 BPM), it may indicate respiratory depression or other respiratory problems;

[0065] The highest breathing threshold represents the critical point of too high breathing rate. If the detected breathing rate is higher than this highest threshold (for example, greater than 20 BPM), it may mean tachypnea or other respiratory abnormalities;

[0066] The minimum heart rate threshold represents the critical point at which the heart rate is too low. For adults, the normal heart rate range is approximately 60 to 100 beats per minute. If the detected heart rate is lower than this minimum threshold (e.g., less than 60 BPM), it may indicate bradycardia;

[0067] The maximum heart rate threshold represents the critical point at which the heart rate is too high. If the detected heart rate is higher than this maximum threshold (e.g., greater than 100 BPM), it may indicate tachycardia.

[0068] The second aspect of the present invention provides a backrest type millimeter wave radar heart rate monitoring method, including:

[0069] Step 1: Obtain the echo signal formed by the reflection of the frequency modulated continuous wave signal through the target position;

[0070] Step 2: Analyze the echo signal to obtain the displacement curve;

[0071] Step 3: Separate the displacement curve to obtain the breathing rate and heart rate;

[0072] Step 4: Judge whether to give an early warning based on the breathing rate and heart rate.

[0073] Compared with the prior art, the beneficial effects of the present invention are:

[0074] 1. Most of the existing cardiac monitoring technologies are contact measurements. Due to reasons such as insufficient comfort and sensitivity to the use environment, it is difficult to achieve the technical problem of long-term continuous cardiac activity monitoring for drivers while driving; the present invention transmits a frequency modulated continuous wave signal through a millimeter wave radar installed on the back of the driver's seat and receives the reflected echo signal in real time, realizing non-contact data acquisition, greatly improving the comfort and convenience of users; by processing the echo signal, generating a displacement curve, and using a band-pass filter and fast Fourier transform (FFT) to separate the breathing rate and heart rate, ensuring the accuracy and reliability of the signal; based on the preset target distance range, the system searches for the maximum peak in the distance dimension spectrogram and locks the target position, further improving the measurement accuracy; judging whether the breathing rate and heart rate are abnormal according to the set minimum and maximum thresholds, and generating early warning information when necessary to ensure timely discovery of potential health problems. The present invention not only realizes long-term continuous monitoring of the driver's heart rate and breathing rate, but also significantly improves the comfort and environmental adaptability during the monitoring process, providing a strong guarantee for driving safety.

[0075] 2. The present invention realizes continuous monitoring of the driver's heart rate and respiratory rate in a non-contact manner, without the user wearing any additional devices, greatly improving the convenience and comfort of use; by analyzing the frequency-modulated continuous wave signal and its reflected signal, the present invention can accurately capture minute chest movements, thereby accurately calculating the respiratory and heart rates, and maintaining high accuracy even in complex or dynamic environments; through advanced signal processing techniques such as band-pass filters and fast Fourier transforms, the signals within the target frequency range are effectively separated, ensuring the reliability of physiological parameter measurement; based on preset minimum and maximum thresholds, the system can real-time determine whether the heart rate and respiratory rate are abnormal, and generate warning information when necessary, providing strong support for timely detection of health problems. BRIEF DESCRIPTION OF THE DRAWINGS

[0076] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following-described drawings are only some embodiments of the present invention, and those of ordinary skill in the art can obtain other drawings based on these drawings without creative efforts.

[0077] Figure 1 It is a schematic diagram of the system module of the embodiment of the present invention;

[0078] Figure 2 It is a schematic diagram of the millimeter-wave radar installation of the embodiment of the present invention;

[0079] Figure 3 It is a schematic diagram of the method steps of the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0080] The following will clearly and completely describe the technical solutions of the present invention in combination with the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts belong to the scope of protection of the present invention.

[0081] Please refer to Figure 1 , the first aspect embodiment of the present invention provides a backrest type millimeter-wave radar heart rate monitoring system, including: a data acquisition module, a data analysis module, and a monitoring and warning module;

[0082] The data acquisition module; obtains the echo signal formed by the reflection of the frequency-modulated continuous wave signal through the target position;

[0083] The data analysis module: analyzes the echo signal to obtain a displacement curve; separates and processes the displacement curve to obtain the respiratory rate and heart rate;

[0084] Monitoring and warning module: Determine whether to give a warning based on the breathing rate and heart rate.

[0085] Obtain the echo signal formed by the reflection of the frequency-modulated continuous wave signal through the target position, including:

[0086] Transmit a frequency-modulated continuous wave signal through a millimeter-wave radar installed on the back of the driver's seat;

[0087] Collect in real time through a receiver the echo signal formed by the reflection of the frequency-modulated continuous wave signal when passing through the target, and send the collected echo signal to the data analysis module; where the target refers to the chest or heart of the driver.

[0088] Refer to Figure 2 , the millimeter-wave radar is installed in a sealed housing 1, and the housing is embedded and installed in the car seat backrest. The system power supply is converted from the vehicle power supply through an internal DCDC converter into the working power supply of the system to provide the working power supply for the detection module;

[0089] Under the seat, a gravity switch 2 is installed. When the driver sits on the seat, through the action of his own gravity, the seat switch 2 is turned on, giving the system a trigger signal, and the system starts to work; when the driver leaves the seat, the switch is turned off, and the module enters the sleep state, automatically cutting off the system working power supply.

[0090] Method for displacement curve, including:

[0091] A1: Determine the frame period for collecting the echo signal;

[0092] A2: Obtain the target distance within each frame period and extract the phase corresponding to the target distance; where the target distance refers to the distance from the target to the radar;

[0093] A3: Generate a phase sequence that changes with time based on the phase corresponding to the target distance within each frame period;

[0094] A4: Obtain the phase change amount between each frame by performing a difference operation on adjacent phases in the phase sequence;

[0095] A5: Based on the relationship between the phase change amount and displacement: Convert the phase change amount into the displacement of the target to generate a displacement curve; where ΔR is the displacement of the target, is the phase change amount, and λ is the working wavelength of the radar.

[0096] Method for target distance, including:

[0097] Mix the transmitted frequency-modulated continuous wave signal and the received echo signal to generate an intermediate frequency signal;

[0098] The expression of the frequency-modulated continuous-wave signal is as follows:

[0099]

[0100] where f c is the carrier frequency of the signal, B is the signal bandwidth, T is the signal frequency-sweeping time, j is the imaginary unit, and t is the time variable;

[0101] The expression of the echo signal is as follows:

[0102]

[0103] where t d is the delay time of the echo signal, t d = 2R / c, R is the distance from the target to the radar, i.e., the target distance, and c is the speed of light;

[0104] The expression of the intermediate-frequency signal is as follows:

[0105]

[0106] where f b is the frequency of the intermediate-frequency signal, is the initial phase of the intermediate-frequency signal, and λ is the radar wavelength;

[0107] By performing analog-to-digital conversion on the intermediate-frequency signal, the digital signal corresponding to the intermediate-frequency signal is obtained;

[0108] By performing a fast Fourier transform on the digital signal corresponding to the intermediate-frequency signal, a spectrogram in the range dimension is obtained; where the horizontal axis of the spectrogram represents the distance and the vertical axis represents the signal amplitude;

[0109] The target distance is obtained based on the spectrogram in the range dimension.

[0110] Obtaining the target distance based on the spectrogram in the range dimension includes:

[0111] Searching on the spectrogram in the range dimension based on a preset target distance range, and selecting the maximum peak of the signal amplitude;

[0112] Extracting the frequency corresponding to the maximum peak and marking it as the target frequency;

[0113] Let f b be the target frequency, and the target distance is calculated through the formula

[0114] For example: The parameters of the millimeter-wave radar are as follows:

[0115] The carrier frequency fc = 77 GHz, the bandwidth B = 4 GHz, and the frequency-sweeping time T = 1 ms. ​

[0116] The radar is installed on the back of the driver's seat and faces the driver's chest (the target distance is within a preset range of (0.3 - 1.2 m).

[0117] Transmitted signal:

[0118]

[0119] Received echo signal:

[0120]

[0121] Generate a displacement curve;

[0122] 1. Mixing to generate an intermediate frequency signal:

[0123]

[0124] Among them,

[0125] 2. Analog-to-digital conversion (ADC) and Fast Fourier Transform (FFT):

[0126] After the intermediate frequency signal is sampled by ADC, a range dimension spectrogram (the horizontal axis is the distance and the vertical axis is the amplitude) is generated through FFT.

[0127] Target distance calculation:

[0128] Search for the maximum amplitude peak within the preset distance range, corresponding to the frequency f b , assuming the searched f b = 100 kHz, substitute into the formula: R = 0.375 m;

[0129] 3. Phase difference and displacement conversion:

[0130] Extract the phase sequence for each frame (the frame period is 50 ms), and calculate the phase change amount by difference

[0131] Through the relationship between the phase change amount and the displacement Convert the phase change into displacement and generate a displacement curve.

[0132] By separating and processing the displacement curve, including:

[0133] B1: Determine the target frequency range; among them, the target frequency range includes: the breathing frequency range and the heartbeat frequency range;

[0134] B2: Filter the displacement curve through a band-pass filter based on the target frequency range to obtain the target frequency signal; among them, the target frequency sequence includes: the breathing frequency signal and the heartbeat frequency signal;

[0135] B3: Obtain a spectrogram by performing a fast Fourier transform on the target frequency signal; wherein, the spectrogram includes: a respiration spectrogram and a heartbeat spectrogram;

[0136] B4: Obtain the target frequency based on the spectrogram; wherein, the target frequency includes: the respiration frequency and the heartbeat frequency.

[0137] Obtaining the target frequency based on the target spectrogram includes:

[0138] Perform frequency division processing on the spectrogram to obtain the target spectrogram; wherein, the target spectrogram includes: the target respiration spectrogram and the target heartbeat spectrogram;

[0139] Extract the frequency corresponding to the peak with the largest amplitude in the target respiration spectrogram as the respiration frequency; extract the frequency corresponding to the peak with the largest amplitude in the target heartbeat spectrogram as the heartbeat frequency.

[0140] The method for the target spectrogram includes:

[0141] Divide the spectrogram at a preset frequency interval to form a number of sub-bands;

[0142] Integrate the spectral values within the sub-band to obtain the total energy of the current sub-band;

[0143] Determine whether the total energy of the current sub-band is greater than a preset threshold; if yes, it is determined as a valid band; if no, it is determined as an invalid band and the current band is removed;

[0144] Retain the valid bands in the number of sub-bands of the spectrogram and remove the invalid bands to obtain the target spectrogram.

[0145] Judging whether to give an alarm based on the respiration frequency and the heartbeat frequency includes:

[0146] C1: Judge whether the respiration frequency is less than the lowest respiration threshold; if yes, generate an alarm message; if no, go to step C2;

[0147] Judge whether the heartbeat frequency is less than the lowest heartbeat threshold; if yes, generate an alarm message; if no, go to step C3;

[0148] C2: Judge whether the respiration frequency is greater than the highest respiration threshold; if yes, generate an alarm message; if no, continue monitoring and judging;

[0149] C3: Judge whether the heartbeat frequency is greater than the highest heartbeat threshold; if yes, generate an alarm message; if no, continue monitoring and judging.

[0150] For example: During long-distance driving, a certain driver's respiration frequency drops to an abnormal value (8 times per minute) due to fatigue, and at the same time, the heartbeat frequency rises to 120 times per minute due to nervousness. Detection and triggering of an alarm are carried out through the following steps:

[0151] Step 1: Displacement curve separation processing;

[0152] 1. Determine the target frequency range:

[0153] Respiratory frequency range: 0.1–0.5 Hz (corresponding to 6–30 breaths per minute).

[0154] Heartbeat frequency range: 0.8–2.5 Hz (corresponding to 48–150 beats per minute).

[0155] 2. Band-pass filter design;

[0156] Respiratory signal filter: Butterworth band-pass filter, cut-off frequency 0.1–0.5 Hz, suppressing noise with an amplitude less than 1 mm.

[0157] Heartbeat signal filter: Chebyshev band-pass filter, cut-off frequency 0.8–2.5 Hz, ripple coefficient 0.1 dB, suppressing noise with an amplitude less than 0.1 mm.

[0158] 3. FFT spectrum analysis;

[0159] Respiratory spectrogram: The main peak is located at 0.13 Hz (corresponding to 8 breaths per minute).

[0160] Heartbeat spectrogram: The main peak is located at 2.0 Hz (corresponding to 120 beats per minute).

[0161] 4. Frequency division processing and target spectrogram;

[0162] Sub-band segmentation: Segment the spectrogram at intervals of 0.05 Hz (e.g., respiratory band: 0.1–0.15 Hz, 0.15–0.2 Hz, etc.).

[0163] Energy integration and threshold judgment:

[0164] For example, for the respiratory band: 0.1–0.15 Hz, the total energy is 500, and the preset threshold is 300, which is determined to be valid.

[0165] Interference band: 0.45–0.5 Hz, the total energy is 250 (less than 300), which is determined to be invalid and removed.

[0166] Output of the target spectrogram: Only the valid bands are retained.

[0167] Step 2: Respiratory and heartbeat frequency extraction;

[0168] 1. Extract the frequency peak;

[0169] Respiratory frequency: 0.13 Hz (corresponding to 8 breaths per minute), taken from the maximum peak (amplitude 8 mm) of the respiratory spectrogram.

[0170] Heartbeat frequency: 2.0 Hz (corresponding to 120 beats per minute), taken from the maximum peak (amplitude 0.3 mm) of the heartbeat spectrogram.

[0171] Step 3: Early warning judgment logic;

[0172] Preset threshold:

[0173] Respiratory rate: minimum threshold 12 breaths per minute, maximum threshold 20 breaths per minute.

[0174] Heartbeat frequency: minimum threshold 60 beats per minute, maximum threshold 100 beats per minute.

[0175] Judgment process:

[0176] 1. Respiratory rate detection: 8 breaths per minute is less than 12 breaths per minute, triggering an early warning.

[0177] 2. Heartbeat frequency detection: 120 beats per minute is greater than 100 beats per minute, triggering an early warning.

[0178] When an early warning is triggered:

[0179] Audible and visual alarm: A beeping sound is emitted inside the vehicle, and "Abnormal respiration" and "Tachycardia" are displayed on the dashboard.

[0180] Data upload: Abnormal data (respiration 8 breaths per minute, heartbeat 120 beats per minute) is synchronized to the cloud monitoring platform.

[0181] Through this example, the system successfully detected the driver's respiratory depression and tachycardia, verifying its ability to accurately separate physiological signals and give real-time early warnings in a high-noise environment.

[0182] Refer to Figure 3 , the second aspect of the present invention provides a backrest type millimeter wave radar heart rate monitoring method, including:

[0183] Step 1: Obtain the echo signal formed by the reflection of the frequency-modulated continuous wave signal through the target position;

[0184] Step 2: Analyze the echo signal to obtain the displacement curve;

[0185] Step 3: Separate the displacement curve to obtain the respiratory rate and heartbeat frequency;

[0186] Step 4: Judge whether to give an early warning based on the respiratory rate and heartbeat frequency.

[0187] Some of the data in the above formula are calculated by removing the dimension and taking their numerical values. The formula is obtained by software simulation of a large amount of collected data to get a formula that is closest to the actual situation. The preset parameters and preset thresholds in the formula are set by those skilled in the art according to the actual situation or obtained through simulation of a large amount of data.

[0188] The above embodiments are only used to illustrate the technical method of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical method of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical method of the present invention.

Claims

1. A backrest type millimeter wave radar heart rate monitoring system, characterized in that: include: Data collection module, data analysis module and monitoring and early warning module; Data acquisition module; Acquire an echo signal formed by the frequency modulated continuous wave signal reflected from the target position; Data analysis module: by analyzing the echo signal, the displacement curve is obtained; by separating the displacement curve, the respiratory rate and heart rate are obtained; Monitoring and early warning module: determines whether to issue an early warning based on breathing rate and heart rate.

2. The backrest type millimeter wave radar heart rate monitoring system according to claim 1, characterized in that: The step of obtaining an echo signal formed by the frequency modulated continuous wave signal being reflected from the target position includes: The frequency modulated continuous wave signal is transmitted through the millimeter radar installed on the back of the driver's seat; The receiver collects in real time the echo signal formed by the reflection of the frequency modulated continuous wave signal when it passes through the target, and sends the collected echo signal to the data analysis module; wherein the target refers to the driver's chest or heart.

3. The backrest type millimeter wave radar heart rate monitoring system according to claim 1, characterized in that: The method for obtaining the displacement curve by analyzing the echo signal includes: A1: Determine the frame period for collecting echo signals; A2: Obtain the target distance in each frame period and extract the phase corresponding to the target distance; where the target distance refers to the distance from the target to the radar; A3: Generate a time-varying phase sequence based on the phase corresponding to the target distance in each frame period; A4: By performing differential operation on adjacent phases in the phase sequence, the phase change between each frame is obtained; A5: Based on the relationship between phase change and displacement: The phase change is converted into the displacement of the target to generate a displacement curve; where ΔR is the displacement of the target, is the phase change, and λ is the operating wavelength of the radar.

4. The backrest type millimeter wave radar heart rate monitoring system according to claim 3, characterized in that: The method for obtaining the target distance in each frame period includes: Mixing the transmitted frequency modulated continuous wave signal and the received echo signal to generate an intermediate frequency signal; The expression of the frequency modulated continuous wave signal is: Among them, f c is the carrier frequency of the signal, B is the signal bandwidth, T is the signal sweep time, j is the imaginary unit, and t is the time variable; The expression of the echo signal is: Among them, t d is the delay time of the echo signal, t d =2R / c, R is the distance from the target to the radar, that is, the target distance, and c is the speed of light; The expression of the intermediate frequency signal is: in, f b is the frequency of the IF signal, is the initial phase of the intermediate frequency signal, λ is the radar wavelength; By performing analog-to-digital conversion on the intermediate frequency signal, a digital signal corresponding to the intermediate frequency signal is obtained; By performing fast Fourier transform on the digital signal corresponding to the intermediate frequency signal, a spectrum of the distance dimension is obtained; wherein the horizontal axis of the spectrum represents the distance, and the vertical axis represents the signal amplitude; Obtain target distance based on the spectrum of distance dimension.

5. The backrest type millimeter wave radar heart rate monitoring system according to claim 4, characterized in that: The method of obtaining the target distance based on the spectrum of the distance dimension includes: Search on the spectrum of the distance dimension based on the preset target distance range and select the maximum peak of the signal amplitude; Extract the frequency corresponding to the maximum peak and mark it as the target frequency; Let f b is the target frequency, through the formula Calculate the target distance.

6. The backrest type millimeter wave radar heart rate monitoring system according to claim 1, characterized in that: The separation process of the displacement curve includes: B1: Determine the target frequency range; wherein the target frequency range includes: breathing frequency range and heart rate frequency range; B2: filtering the displacement curve through a bandpass filter based on the target frequency range to obtain a target frequency signal; wherein the target frequency sequence includes: a respiratory frequency signal and a heart rate frequency signal; B3: Obtain a spectrum diagram by performing fast Fourier transform on the target frequency signal; wherein the spectrum diagram includes: a breathing spectrum diagram and a heartbeat spectrum diagram; B4: Obtaining a target frequency based on the spectrum diagram; wherein the target frequency includes: breathing frequency and heart rate frequency.

7. The backrest type millimeter wave radar heart rate monitoring system according to claim 6, characterized in that: The step of acquiring the target frequency based on the target spectrum diagram includes: Perform frequency division processing on the spectrum graph to obtain a target spectrum graph; wherein the target spectrum graph includes: a target breathing spectrum graph and a target heartbeat spectrum graph; The frequency corresponding to the peak with the largest amplitude in the target breathing spectrum is extracted as the breathing frequency; the frequency corresponding to the peak with the largest amplitude in the target heartbeat spectrum is extracted as the heartbeat frequency.

8. The backrest type millimeter wave radar heart rate monitoring system according to claim 7, characterized in that: The method of performing frequency division processing on the spectrum graph to obtain the target spectrum graph includes: The spectrum graph is divided into several sub-bands according to preset frequency intervals; Integrate the spectrum values ​​within the sub-band to obtain the total energy of the current sub-band; Determine whether the total energy of the current sub-frequency band is greater than a preset threshold; if yes, it is determined to be a valid frequency band; if no, it is determined to be an invalid frequency band and the current frequency band is removed; The effective frequency bands in several sub-frequency bands of the spectrum graph are retained, and the invalid frequency bands are removed to obtain the target spectrum graph.

9. The backrest type millimeter wave radar heart rate monitoring system according to claim 1, characterized in that: The determining whether to issue an early warning based on the respiratory rate and the heart rate includes: C1: Determine whether the respiratory rate is less than the minimum respiratory threshold; if yes, generate a warning message; if no, go to step C2; Determine whether the heart rate is less than the minimum heart rate threshold; if yes, generate a warning message; if no, go to step C3; C2: Determine whether the respiratory rate is greater than the maximum respiratory threshold; if yes, generate a warning message; if no, continue monitoring and judgment; C3: Determine whether the heart rate is greater than the maximum heart rate threshold; if yes, generate a warning message; if not, continue monitoring and judging.

10. A backrest type millimeter wave radar heart rate monitoring method, applied to a backrest type millimeter wave radar heart rate monitoring system according to any one of claims 1 to 9, characterized in that: include: Step 1: Acquire an echo signal formed by the frequency modulated continuous wave signal reflected at the target position; Step 2: Analyze the echo signal to obtain the displacement curve; Step 3: Get the respiratory rate and heart rate by separating the displacement curve; Step 4: Determine whether to issue an early warning based on the breathing rate and heart rate.

Images