Ballistocardiogram detection device and ballistocardiogram measurement system with noise reduction function

Abstract

To provide a ballistocardiogram detection device having a noise reduction function, and a ballistocardiogram measurement system.SOLUTION: A ballistocardiogram detection device having a noise reduction function includes a pressure reception device, a force sensor, a vibration sensor, and a signal processing module. The pressure reception device is arranged directly or indirectly in a lower part or a back of a body of a subject. The force sensor and the vibration sensor are provided in the pressure reception device. A distance between the vibration sensor and the force sensor is less than 20 cm. The signal processing module electrically connects the force sensor and the vibration sensor and receives a signal output by the force sensor and the vibration sensor.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a ballistocardiogram detection device and a ballistocardiogram measurement system, and more particularly to a ballistocardiogram detection device and a ballistocardiogram measurement system having a noise reduction function. [Background technology]

[0002] A ballistocardiogram (BCG) is a physiological signal generated by the heart. The waveform of a ballistocardiogram shows the regular movement of the body due to the force generated by the cardiac output from the heart hitting the walls of the ascending and descending aorta. A ballistocardiogram can effectively reflect the health status of the human cardiovascular system. Ballistocardiograms can be applied in various fields, such as heart rate monitoring systems for heart rate monitoring, cardiac function (systolic and diastolic) evaluation, and physiological signal analysis (respiratory rate and blood pressure changes). Ballistocardiograms can be combined with wearable devices to remotely monitor the cardiac health of patients with chronic diseases, or to analyze cardiac activity during sleep to help diagnose sleep disorders.

[0003] In current technology, many bed monitoring devices or instruments for measuring ballistocardiograms have been developed and produced. However, ballistocardiogram signals (also known as BCG signals) are minute vibrations of the body caused by the contraction and expansion of the heart (i.e., the BCG signal itself is a minute signal), and are easily affected by interference signals from other body movements or the mattress itself when detected. Therefore, the signal-to-noise ratio (SNR) of BCG signals detected by current devices is poor. Therefore, how to improve them to overcome the above drawbacks is one of the important issues to be solved in this field. Summary of the Invention [Problem to be solved by the invention]

[0004] The problem to be solved by the present invention has been made in consideration of the shortcomings of the prior art, and is to provide a ballistocardiogram detection device and a ballistocardiogram measurement system having a noise reduction function that can accurately measure the BCG signal of a subject and achieve a noise reduction effect. [Means for solving the problem]

[0005] To solve the above problems, the present invention provides a ballistocardiogram detection device with a noise reduction function. The ballistocardiogram detection device with a noise reduction function includes a pressure receiving device, a force sensor, a vibration sensor, and a signal processing module. The pressure receiving device is placed directly or indirectly below or on the back of the subject's body. The force sensor and the vibration sensor are provided on the pressure receiving device. The distance between the vibration sensor and the force sensor is less than 20 cm. The signal processing module electrically connects the force sensor and the vibration sensor and receives signals output by the force sensor and the vibration sensor.

[0006] Another means employed in the present invention to solve the above problems is a ballistocardiogram measurement system. The ballistocardiogram measurement system includes a soft protective pad, multiple measurement devices, and a signal processing module. The multiple measurement devices are respectively arranged in multiple regions of the soft protective pad. Each measurement device includes a force sensor and a vibration sensor, and measures the force and vibration applied to the soft protective pad in the region where the measurement device is located, so that the force sensor outputs a force measurement signal and the vibration sensor outputs a vibration measurement signal. The signal processing module electrically connects the multiple force sensors and multiple vibration sensors in the multiple measurement devices. The signal processing module receives multiple vibration measurement signals from the multiple vibration sensors, generates multiple ballistocardiogram waveforms based on the multiple vibration measurement signals, and further captures multiple peak points from the multiple ballistocardiogram waveforms and obtains multiple heartbeat interval data from the multiple peak points. [Effects of the Invention]

[0007] The present invention has the following advantageous effects: The ballistocardiogram detection device and ballistocardiogram measurement system with noise reduction function provided by the present invention allows the vibration sensor and the force sensor to be positioned close to each other, with a distance of less than 20 cm, so that the force sensor and the vibration sensor can be located in the same measurement area. Thus, the signal processing module receives multiple vibration measurement signals from the multiple vibration sensors, generates multiple ballistocardiogram waveforms based on the multiple vibration measurement signals, and obtains multiple cardiac interval data from the multiple ballistocardiogram waveforms. Furthermore, the signal processing module screens or weights the multiple cardiac interval data based on the force measurement signals, so that the accuracy and signal-to-noise ratio of the obtained cardiac interval data are improved, thereby achieving noise protection and noise reduction effects.

[0008] In order to further understand the features and technical contents of the present invention, please refer to the following detailed description of the present invention and the drawings, but the drawings provided are for reference and explanation only and are not intended to limit the present invention. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic diagram of a ballistocardiogram detection device of the present invention; [Figure 2] FIG. 2 is another schematic diagram of the ballistocardiogram detection device of the present invention. [Figure 3] 1A and 1B are schematic diagrams of a pressure-receiving device, a force sensor, and a vibration sensor according to the present invention. [Figure 4] 1 is a vibration waveform diagram obtained using the ballistocardiogram detection device of the present invention. FIG. [Figure 5] FIG. 10 is another vibration waveform diagram obtained using the ballistocardiogram detection device of the present invention. [Figure 6] FIG. 1 is a diagram of heartbeat interval data captured from an oscillogram. [Figure 7] FIG. 1 is a curve diagram of downward force obtained using the ballistocardiogram detection device of the present invention. [Figure 8] FIG. 10 is a diagram showing a moving average curve obtained without removing noise signals from heartbeat interval data. [Figure 9]FIG. 10 is a diagram showing a moving average curve obtained by removing noise signals from heartbeat interval data. [Figure 10] 1 is a side schematic view of a ballistocardiogram measurement system according to the present invention; [Figure 11] 1 is a schematic top view of a ballistocardiogram measurement system according to the present invention; FIG. [Figure 12] FIG. 2 is a vibration waveform diagram obtained using a plurality of ballistocardiogram detection devices in the ballistocardiogram measurement system of the present invention. [Figure 13] FIG. 10 is a curve diagram of multiple downward forces obtained using multiple ballistocardiogram detection devices in the ballistocardiogram measurement system of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] The following describes the "ballistocardiogram detection device and ballistocardiogram measurement system with noise reduction function" disclosed in the present invention through specific embodiments. Those skilled in the art can understand the advantages and effects of the present invention from the contents disclosed in this specification. The present invention may be implemented or applied using other specific embodiments, and the details herein may be modified and changed in various ways based on different perspectives and applications without departing from the concept of the present invention. It should be noted that the drawings are for simple and schematic illustration only and are not drawn to scale. The following embodiments will further describe the technical details of the present invention, but the disclosed contents do not limit the scope of protection of the present invention. Furthermore, although terms such as "first" and "second" may be used to describe various components in this specification, it should be understood that these components should not be limited by these terms. These terms are primarily used to distinguish one component from another. The term "or" used in this specification may include any one or more combinations of the relevant listed items according to actual circumstances.

[0011] [Example] As shown in FIG. 1, the present invention provides a ballistocardiogram detection device. The ballistocardiogram detection device includes a pressure receiving device 1, a force sensor 2, a vibration sensor 3, and a signal processing module 4. The pressure receiving device 1 is directly or indirectly placed under or on the back of a subject U. For example, the subject U may be a human or other animal, but the present invention does not limit the type of the subject U. In the present invention, the subject U will be described as a human.

[0012] The force sensor 2 and the vibration sensor 3 are provided on the pressure receiving device 1, and the vibration sensor 3 is located near the force sensor 2. Preferably, the distance between the vibration sensor 3 and the force sensor 2 is less than 20 cm, so that the vibration sensor 3 and the force sensor 2 are located within the same measurement range and the phases of the signals output by the vibration sensor 3 and the force sensor 2 correspond to each other (i.e., the signal phases are close or equivalent). The signal processing module 4 electrically connects the force sensor 2 and the vibration sensor 3, and receives the signals output by the force sensor 2 and the vibration sensor 3.

[0013] The subject U (i.e., the human body) can be a force source and a vibration source. For example, when the pressure receiving device 1 is placed directly or indirectly on the back of the subject U's body, the subject U applies a downward force to the pressure receiving device 1, and the force sensor 2 measures the force received by the pressure receiving device 1 and outputs a force measurement signal. The vibration sensor 3 also measures the body vibration of the subject U due to heartbeat and outputs a vibration measurement signal. In another embodiment, as shown in FIG. 2 , when the subject U changes his / her position, the measurement areas of the force sensor 2 and the vibration sensor 3 are separated from the back of the subject U, so that the pressure receiving device 1 receives no force (downward force = 0), and the force sensor 2 does not measure the force received by the pressure receiving device 1. However, because the measurement sensitivity of the vibration sensor 3 is higher than that of the force sensor 2, the vibration sensor 3 may measure other vibration signals from different measurement areas (e.g., the lower limbs of the subject U or other nearby objects).

[0014] As shown in FIG. 3, the present invention further provides a specific embodiment of a ballistocardiogram detection device. For example, the ballistocardiogram detection device may include a pressure receiving device 1, a force sensor 2, and a vibration sensor 3. The pressure receiving device 1 may include a first pressure receiving plate 11 and a second pressure receiving plate 12. The first pressure receiving plate 11 and the second pressure receiving plate 12 have essentially the same shape and size, and the first pressure receiving plate 11 is located above the second pressure receiving plate 12. The force sensor 2 is provided between the first pressure receiving plate 11 and the second pressure receiving plate 12. The vibration sensor 3 is provided on the first pressure receiving plate 11. The vibration sensor 3 is provided on the upper surface of the first pressure receiving plate 11 and is located directly above the first pressure receiving plate 11. The pressure receiving device 1 may also include two limit rivets S movably fixed to both sides of the pressure receiving plates (the first pressure receiving plate 11 and the second pressure receiving plate 12). The limit rivet S limits the deformation of the first pressure plate 11 to within the allowable range of the corresponding limit rivet S, thereby preventing the first pressure plate 11 from being deformed too much.

[0015] Furthermore, the location of the signal processing module 4 is not limited to a specific location, and it may be integrated inside the pressure receiving device 1 or may be provided as a separate component outside the pressure receiving device 1. The signal processing module 4 may include, but is not limited to, a signal amplifier, a filter, and an analog-to-digital signal converter to receive, filter, convert, and perform subsequent analysis processing of the detected signal.

[0016] For example, the force sensor 2 is a load cell including an electric resistance strain gauge. When in use, the electric resistance strain gauge is attached to the object to be measured. The resistance value of the electric resistance strain gauge changes as the object to be measured expands or contracts, and the strain is estimated from the change in resistance value. Therefore, when the first pressure receiving plate 11 is deformed by the application of force, Force Sensor 2 measures the deformation caused when the first pressure-receiving plate 11 receives a force and outputs a force measurement signal.

[0017] For example, the vibration sensor 3 may be a piezoelectric sensor. When a piezoelectric sensor is subjected to mechanical stress, it generates an electric signal due to the piezoelectric effect. In the present invention, the vibration sensor 3 measures the minute vibrations generated when the first pressure-receiving plate 11 receives force, and outputs a vibration measurement signal.

[0018] As shown in Figures 1 and 4, for example, when the vibration sensor 3 measures the body vibration of the subject U due to heartbeat and outputs a vibration measurement signal, the signal processing module 4 receives the vibration measurement signal and generates a vibration waveform, i.e., a ballistocardiogram waveform, as shown in Figure 4. The signal processing module 4 extracts multiple peak points from the ballistocardiogram waveform and can obtain multiple heartbeat interval data P from the multiple peak points. Similarly, as shown in Figures 2 and 5, the vibration sensor 3 also measures a ballistocardiogram waveform caused by a vibration measurement signal from another measurement region (considered to be an interference signal or noise), and the signal processing module 4 extracts multiple peak points from the ballistocardiogram waveform and can obtain multiple heartbeat interval data Q from the multiple peak points.

[0019] In other words, in the detection process of the vibration sensor 3, the detected vibration waveform is a comprehensive waveform that includes the waveform generated by vibrations from its own measurement area (FIG. 4) and the waveform generated by vibrations from other measurement areas (FIG. 5). Therefore, as shown in FIG. 6, the signal processing module 4 simultaneously acquires multiple heartbeat interval data P and Q. Next, the signal processing module 4 performs a moving average calculation on the multiple heartbeat interval data P and Q to obtain the moving average curve diagram shown in FIG. 8. Statistically, a moving average is usually used in conjunction with a time series to eliminate short-term fluctuations and emphasize long-term trends or cycles. Therefore, the ballistocardiogram obtained by the moving average calculation (see FIG. 8) can more accurately reflect the heart rate of the subject U.

[0020] However, as mentioned above, in the detection process of the vibration sensor 3, the detected vibration waveform is a comprehensive waveform, and strictly speaking, Fig. 8 cannot actually reflect the heartbeat of the subject U (because it contains noise caused by the vibration of other objects). Therefore, the signal processing module 4 receives the force measurement signal from the force sensor 2 and, based on the force measurement signal, screens multiple heartbeat interval data, thereby removing the heartbeat interval data Q and leaving the heartbeat interval data P.

[0021] For more details, refer to the force / time curve diagram (FIG. 7) generated when the signal processing module 4 receives the force measurement signal from the force sensor 2, shown in FIGS. 6 and 7. The force sensor 2 and the vibration sensor 3 are located in the same measurement area, and the downward force measured by the force sensor 2 corresponds to the heartbeat interval data. For example, in FIG. 7, the section where the downward force measured by the force sensor 2 is F (F is a preset fixed value) corresponds to the distribution of the heartbeat interval data P in FIG. 6. In FIG. 7, the section where the downward force measured by the force sensor 2 is 0 corresponds to the distribution of the heartbeat interval data Q in FIG. 6. Therefore, the signal processing module 4 can determine that the heartbeat interval data Q is noise and delete it. That is, by arranging the force sensor 2 and the vibration sensor 3 to be located in the same measurement area, the signal processing module 4 can determine whether the vibrations measured by the vibration sensor 3 are from the same measurement area, thereby reducing heart rate calculation errors. Next, the screened heartbeat interval data P is calculated to obtain the moving average value of the heartbeat intervals shown in FIG. 9. FIG. 9 is a ballistocardiogram obtained after noise reduction and moving average calculation, which can actually reflect the heart rate of subject U.

[0022] The present invention also provides a ballistocardiogram measurement system. As shown in Figures 10 and 11, the ballistocardiogram measurement system includes a plurality of measurement devices D and a soft protective pad 5. The plurality of measurement devices D are arranged in a plurality of regions of the soft protective pad 5. The soft protective pad 5 is directly or indirectly arranged below or on the back of the body of a subject U. For example, as shown in Figure 10, the soft protective pad 5 is arranged below a mattress 6, and a user (subject U) lies on the mattress 6.

[0023] Each measuring device D is the ballistocardiogram detection device mentioned above, and includes a force sensor 2 and a vibration sensor 3 (see FIG. 1). Each measuring device D measures the force and vibrations experienced by the soft protective pad 5 in the area where the measuring device D is located, so that the force sensor 2 outputs a force measurement signal and the vibration sensor 3 outputs a vibration measurement signal. The signal processing module 4 electrically connects the multiple force sensors 2 and multiple vibration sensors 3 in the multiple measuring devices D.

[0024] As shown in FIG. 11, three measurement devices in a ballistocardiogram measurement system will be described as an example. These three measurement devices are referred to as measurement devices D1 to D3. In FIG. 11, a user (subject U) is lying on his / her side. From a relative perspective, the force of gravity acting on measurement device D1 is greatest, indicating that the signal measured by measurement device D1 can better reflect the user's heart rate on measurement devices D2 and D3. As shown in FIGS. 1, 11, and 12, signal processing module 4 receives multiple vibration measurement signals from vibration sensors 3 in measurement devices D1 to D3 and generates multiple ballistocardiogram waveforms based on the multiple vibration measurement signals, as shown in FIG. 12. The upper waveform in FIG. 12 is obtained from measurement device D1, the middle waveform is obtained from measurement device D2, and the lower waveform is obtained from measurement device D3.

[0025] The signal processing module 4 further extracts multiple peak points from each ballistocardiogram waveform and obtains multiple heartbeat interval data from the multiple peak points. As shown in FIG. 12, the heartbeat interval data A1, A2,...A nindicates that the heartbeat interval data B1, B2, B n indicates that the heartbeat interval data C1, C2...C are obtained from the ballistocardiogram waveform of the measuring device D2. n represents what can be obtained from the ballistocardiogram waveform of the measuring device D3.

[0026] Next, as shown in Fig. 13, the signal processing module 4 receives a plurality of force measurement signals from the force sensors 2 of the measuring devices D1 to D3, and generates a plurality of force / time curves based on the plurality of force measurement signals. As shown in Fig. 12 and Fig. 13, the downward force F1 in Fig. 13 corresponds to the ballistocardiogram waveform of the measuring device D1 in Fig. 12, the downward force F2 in Fig. 13 corresponds to the ballistocardiogram waveform of the measuring device D2 in Fig. 12, and the downward force F3 in Fig. 13 corresponds to the ballistocardiogram waveform of the measuring device D3 in Fig. 12.

[0027] As can be seen from the relative positional distribution between the measuring devices D1-D3 and the user's body in Figure 11, the closer the measuring device is to the user, the greater the force received by the pressure-receiving device 1, and the vibration waveform obtained by the measuring device can accurately reflect the ballistocardiogram generated by the user's heartbeat. Therefore, the signal processing module 4 receives multiple force measurement signals from multiple force sensors 2 and assigns a corresponding weight to each force measurement signal. The greater the downward force, the greater the weight assigned. As shown in Figure 13, for example, the weight for downward force F1 is set to W1, the weight for downward force F2 is set to W2, and the weight for downward force F3 is set to W3. Next, the signal processing module 4 performs a weighted calculation of the heartbeat interval data based on the obtained weights to obtain a weighted average value of the heartbeat interval data. As shown in Figures 12 and 13, a weighted average calculation is performed on the heartbeat interval data for the same time segment. For example, a first weighted average value obtained by performing a weighted average calculation on the heartbeat interval data A1, B1, and C1 in the first time segment is equal to ((A1×W1)+(B1×W2)+(C1×W3)) / (W1+W2+W3). A second weighted average value obtained by performing a weighted average calculation on the heartbeat interval data A2, B2, and C2 in the second time segment is equal to ((A2×W1)+(B2×W2)+(C2×W3)) / (W1+W2+W3). Heartbeat interval data A in the nth time segment n , B n , C n The nth weighted average value obtained by performing a weighted average calculation is ((A n ×W1)+(B n ×W2)+(C n ×W3)) / (W1+W2+W3), where n is a natural number greater than 3.

[0028] By performing the weighted average calculation, the proportion of the vibration signal from the measuring device D1 closer to the user increases, that is, the proportion of the vibration signal from the measuring device D1 farther from the user decreases (because the farther away from the user, the weaker and noisier the vibration measurement signal measured becomes), thus achieving a noise reduction effect. As a result, the noise is reduced and the ballistocardiogram obtained after the weighted average calculation can actually reflect the heart rate of the user (subject U).

[0029] The contents disclosed above are merely preferred and possible embodiments of the present invention, and do not limit the scope of the claims of the present invention. Therefore, any equivalent technical modifications made using the contents of the specification and drawings of the present invention are included within the scope of the claims of the present invention. [Explanation of symbols]

[0030] D, D1 to D3: Measuring equipment 1: Pressure receiving device 2: Force sensor 3: Vibration sensor 4: Signal processing module 5: Soft protective pad 6: Mattress 11: First pressure plate 12: Second pressure plate U: Subject F, F1~F3: Downward force P, Q, A1, A2, A n , B1, B2, B n , C1, C2, C n : Heart rate data S: Limit rivet

Claims

1. A pressure receiving device that is placed directly or indirectly on the lower or back of the subject's body; a force sensor provided in the pressure receiving device; a vibration sensor provided on the pressure receiving device, the distance between the vibration sensor and the force sensor being less than 20 cm; a signal processing module that electrically connects the force sensor and the vibration sensor and receives signals output by the force sensor and the vibration sensor; The pressure receiving device includes a first pressure receiving plate, a second pressure receiving plate provided below the first pressure receiving plate, and two limit rivets movably fixed to both sides of the first pressure receiving plate and the second pressure receiving plate, the force sensor is provided between the first pressure receiving plate and the second pressure receiving plate, measures deformation of the first pressure receiving plate caused by a force, and outputs a force measurement signal in response thereto; The vibration sensor is provided directly above the first pressure plate, measures minute vibrations caused by the force applied to the first pressure plate, and outputs a vibration measurement signal in response thereto, and the vibration sensor and the force sensor are located within the same measurement range. A ballistocardiogram detection device having a noise reduction function.

2. 2. The ballistocardiogram detection device with noise reduction function as claimed in claim 1, wherein the force sensor is a load cell.

3. 3. The ballistocardiogram detection device with noise reduction function according to claim 2, wherein the vibration sensor is a piezoelectric sensor.

4. 4. The ballistocardiogram detection device with noise reduction function according to claim 3, wherein the signal processing module receives the vibration measurement signal, generates a ballistocardiogram waveform based on the vibration measurement signal, and further extracts a plurality of peak points from the ballistocardiogram waveform and obtains a plurality of cardiac interval data from the plurality of peak points.

5. 5. The ballistocardiogram detection device with noise reduction function according to claim 4, wherein the signal processing module receives the force measurement signal, screens a plurality of the cardiac interval data based on the force measurement signal, and calculates the screened plurality of the cardiac interval data to obtain a moving average value of the cardiac interval data.

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