In-ear multichannel ear electroencephalogram signal acquisition equipment

Abstract

The invention discloses in-ear multi-channel ear electroencephalogram signal acquisition equipment which comprises a front-end acquisition device, a rear-end acquisition device and a signal processing device, the front-end acquisition device is provided with an in-ear electrode, an earphone shell for installing the in-ear electrode, and a front-end amplification circuit for amplifying the ear electroencephalogram signal; the control mainboard is at least provided with an analog front end for converting the ear electroencephalogram signals into digital signals, a main control chip for receiving the digital signals, and a power supply module for supplying power to the analog front end and the main control chip; and the connecting assembly is used for connecting and fixing the front-end acquisition device and the control mainboard. Compared with the prior art, the in-ear electrode has more signal channels, more comprehensive physiological data can be provided, wider application scenarios are facilitated, in addition, the memory sponge earplug and the elastic supporting structure are adopted, and the adaptability of the electrode and the ear canal is improved.

Description

Technical Field

[0001] The invention relates to the medical field, and in particular to an in-ear multi-channel electroencephalogram signal acquisition device. Background Art

[0002] Electroencephalography (EEG) is a method of measuring and recording neurophysiological activity in a non-invasive manner. It is widely used in medical clinics, scientific research and other fields. As shown in Figure 1, traditional EEG uses electrodes covering the entire brain to obtain EEG signals with high quality and spatial resolution. Wet electrodes such as gel electrodes and saline electrodes are usually used. This acquisition method is complex to operate and has limited usage scenarios. In order to overcome the limitations of traditional acquisition, wearable EEG devices have designed many new acquisition solutions to balance signal quality and portability according to usage scenarios.

[0003] Ear EEG is a method of collecting EEG by placing electrodes in the ears. Its principle is the same as that of standard EEG collected by the scalp, and EEG signals are collected through the brain volume conduction effect. The electrodes are placed in the ears, so they are more sensitive to signals from the temporal lobe, and have more advantages than EEG caps in some special scenarios. The appearance of ear EEG collection equipment is similar to hearing aids, headphones and other devices, and it has good wearability.

[0004] Generally, ear EEG acquisition devices are divided into two categories: (1) Intra-ear EEG acquisition devices: electrodes are placed in the external auditory canal, cavum concha and cymba concha. (2) Periauricular EEG acquisition devices: electrodes are placed in the periauricular area, which is usually not covered by hair.

[0005] The appearance of in-ear EEG devices is similar to in-ear headphones. The main difference lies in the electrode design and can be divided into the following options.

[0006] (1) The electrodes were originally personalized electrodes made based on ear molds. This design requires the ear canal to be re-molded first, and then reconstructed using 3D printing or re-molding. Since the structure of each person's ear canal is different, this personalized electrode can only be used by one person alone and has poor versatility. Although this electrode is specially made according to the shape of the ear canal, since the electrode material has a certain hardness and rigidity, the movement of the ear canal often causes a gap between the electrode contact and the skin, which is prone to motion artifacts. [Publication No.: CN114711777A] Based on the idea of ​​personalized electrodes, the electrode structure is improved to optimize the design.

[0007] (2) Conductive rubber earplug electrodes. The material of this type of electrode usually uses polydimethylsiloxane (PDMS) as the substrate. This material has excellent ductility and low dielectric constant. It needs to be doped or combined with other conductive materials to prepare electrodes. [Publication number: CN218651833U] PDMS doped carbon nanotubes are used to make binaural electrodes, which improves conductivity while taking into account comfort. [Publication number: CN210871574U] Elastic support materials and titanium alloys are used to make electrodes, dual-channel signal acquisition, and data is transmitted via Bluetooth.

[0008] (3) Elastic earplug-type electrode. This solution is closest to the present invention. The elastic earplug-type electrode is made of viscoelastic insulating material and flexible conductive material. The viscoelastic insulating material is used as the base, and memory foam is tried; the flexible conductive material is used as the electrode contact, and various conductive fabrics are often used. Since memory foam has good elasticity, this type of electrode has a high degree of adaptability to the ear canal and can reduce the adverse effects of motion artifacts. [DOI: 10.1109 / JSEN.2015.2471183] uses memory foam earplugs and silver-plated nylon cloth.

[0009] Based on the above settings, there are problems in the prior art: Personalized electrodes have poor versatility and high production costs; gaps are easily generated between the electrode contacts and the skin, and the signal quality is easily affected by motion artifacts; some electrodes also require the use of conductive gel to achieve good contact between the electrode and the skin.

[0010] (2) The conductive rubber earplug electrode does not fit the shape of the ear canal well enough, and the insertion depth and stability are limited; the contact impedance with the skin is high; due to the limitations of the manufacturing process, single-channel acquisition is mostly performed in a single ear canal, using the ipsilateral concha or the contralateral ear canal as a reference, which limits the spatial resolution of the signal.

[0011] (3) The surface pressure of the elastic earplug electrode is evenly distributed, but it blocks sound propagation to a certain extent, which has an impact on some usage scenarios.

[0012] Therefore, how to design an in-ear multi-channel ear EEG signal acquisition device to solve the problems existing in the prior art is a technical problem that needs to be solved urgently in the industry. Summary of the invention

[0013] In view of the problem of poor versatility of personalized electrodes in the prior art, the present invention proposes an in-ear multi-channel ear electroencephalogram signal acquisition device.

[0014] The technical solution of the present invention is to propose an in-ear multi-channel electroencephalogram signal acquisition device, comprising: A front-end acquisition device, which is used to be worn on the ear of the user to collect ear electroencephalogram signals, and the front-end acquisition device has an in-ear electrode, an earphone shell for installing the in-ear electrode, and a front-end amplification circuit for amplifying the ear electroencephalogram signals, and the in-ear electrode has a plurality of signal acquisition channels for collecting the ear electroencephalogram signals; A control mainboard, which at least has an analog front end for converting the ear and brain electroencephalogram signals into digital signals, a main control chip for receiving the digital signals, and a power supply module for supplying power to the analog front end and the main control chip; A connecting component is used to connect and fix the front-end acquisition device and the control mainboard.

[0015] Further, the in-ear electrode comprises: a silicone earpiece tube, a memory foam earplug, and a plurality of metal conductive fabrics; The silicone earpiece tube is configured as a double-layer structure, and a copper wire is disposed between the two layers of the silicone earpiece tube. The memory foam earplug is coated on the outside of the silicone earpiece tube. The metal conductive fabric is used as the signal acquisition channel and is assembled inside the memory foam earplug, and is connected to the copper wire inside the memory foam earplug.

[0016] Furthermore, the in-ear electrode includes a reference electrode and a bias electrode, and both the reference electrode and the bias electrode are disposed in the earphone housing; The shape of the earphone shell matches the shape of the user's concha, so that the reference electrode is installed at the concha cavity and the bias electrode is installed at the cymba concha.

[0017] Furthermore, the front-end amplifier circuit includes: resistor R4, resistor R5, resistor R6, capacitor C8, capacitor C9, capacitor C10, capacitor C16, amplifier U3, amplifier U17; The third end of the amplifier U3 is connected in series with the resistor R6 and then connected to the ear and brain electroencephalogram signal, the fourth end of the amplifier U3 is connected in series with the resistor R4 and then grounded, the first end of the amplifier U3 is connected to the third end of the amplifier U17, the fifth end of the amplifier U3 is connected to the positive electrode of the 2.5V power supply, and the second end of the amplifier U3 is connected to the negative electrode of the 2.5V power supply; The first end of the amplifier U17 is used to output the ear and brain electroencephalogram signal after primary amplification, the fourth end of the amplifier U17 is connected to the first end of the amplifier U17, the fifth end of the amplifier U17 is connected to the positive pole of the 2.5V power supply, and the second end of the amplifier U17 is connected to the negative pole of the 2.5V power supply; One end of the resistor R5 is connected between the resistor R4 and the fourth end of the amplifier U3, and the other end of the resistor R5 is connected between the first end of the amplifier U3 and the third end of the amplifier U17; One end of the capacitor C10 is connected between the fifth end of the amplifier U3 and the positive electrode of the 2.5V power supply, the other end of the capacitor C10 is grounded, and the capacitor C8 is connected in parallel to both ends of the capacitor C10; One end of the capacitor C9 is connected between the second end of the amplifier U3 and the negative electrode of the 2.5V power supply, the other end of the capacitor C9 is grounded, and the capacitor C16 is connected in parallel across the capacitor C9.

[0018] Further, the power module includes a charging circuit, and the charging circuit includes: a resistor R29, a resistor R30, a thermistor R31, a resistor R34, a capacitor C84, a capacitor C85, a light-emitting diode LED1, a light-emitting diode LED2, a fuse F2, an inductor L8, a bidirectional voltage regulator U12, and a charging management chip U11; One end of the fuse F2 is connected to the charging interface, the other end of the fuse F2 is connected to one end of the inductor L8, the other end of the inductor L8 is respectively connected to the CE pin of the charging management chip U11, the positive electrode of the light-emitting diode LED1, and the positive electrode of the light-emitting diode LED2, the negative electrode of the light-emitting diode LED1 is connected in series with the resistor R29 and then connected to the CHRG pin of the charging management chip U11, and the negative electrode of the light-emitting diode LED2 is connected in series with the resistor R30 and then connected to the STDBY pin of the charging management chip U11; The BAT pin of the charging management chip U11 outputs the charging voltage as the output end of the charging circuit, the TEMP pin and the GND pin of the charging management chip U11 are grounded, the PROG pin of the charging management chip U11 is connected in series with the resistor R34 and then grounded, and the VCC pin of the charging management chip U11 is connected between the inductor L8 and the CE pin of the charging management chip U11; One end of the thermistor R31 is connected between the charging port and the fuse F2, and the other end of the thermistor R31 is grounded; One end of the bidirectional voltage regulator U12 is connected between the fuse F2 and the inductor L8, and the other end of the bidirectional voltage regulator U12 is grounded; One end of the capacitor C84 is connected between the inductor L8 and the CE pin of the charging management chip U11, and the other end of the capacitor C84 is grounded.

[0019] Furthermore, the power module includes: a lithium battery power supply circuit and a power detection circuit; The lithium battery power supply circuit includes: resistor R7, resistor R8, resistor R9, resistor R10, resistor R11, capacitor C56, capacitor C57, capacitor C58, fuse F1, inductor L6, voltage regulator U9, switch TA-3525, connector U6, and voltage regulator U7; The first end of the switching switch TA-3525 is connected to the second end of the connector U6, the second end of the switching switch TA-3525 is connected in series with the fuse F1 and the resistor R7 and then connected to the EN pin of the voltage regulator U7, and the third end of the switching switch TA-3525 is grounded; One end of the resistor R10 is connected between the fuse F1 and the resistor R7, and the other end of the resistor R10 is connected in series with the resistor R11 and then grounded; one end of the capacitor C57 is connected between the fuse F1 and the resistor R7, and the other end of the capacitor C57 is grounded; one end of the capacitor C58 is connected between the fuse F1 and the resistor R7, and the other end of the capacitor C58 is grounded; The NC pin of the voltage regulator U7 is vacant, the IN pin of the voltage regulator U7 is connected between the fuse F1 and the resistor R7, the GND pin of the voltage regulator U7 is grounded, the FB pin of the voltage regulator U7 is connected in series with the resistor R9 and then connected to the positive electrode of the 5V power supply, one end of the resistor R8 is connected between the GND pin of the voltage regulator U7 and the ground, and the other end of the resistor R8 is connected between the FB pin of the voltage regulator U7 and the resistor R9, one end of the capacitor C56 is connected between the GND pin of the voltage regulator U7 and the ground, and the other end of the capacitor C56 is connected between the positive electrode of the 5V power supply and the resistor R9; One end of the inductor L6 is connected to the IN pin of the voltage regulator U7, the other end of the inductor L6 is connected to the positive electrode of the voltage regulator U9, the negative electrode of the voltage regulator U9 is connected between the positive electrode of the 5V power supply and the resistor R9, and the SW pin of the voltage regulator U7 is connected between the inductor L6 and the voltage regulator U9.

[0020] Further, the power detection circuit includes: a resistor R35, a resistor R36, a capacitor C86, and an amplifier U14; The third end of the amplifier U14 is connected in series with the resistor R35 to receive the power supply voltage of the lithium battery, the first end of the amplifier U14 is connected in series with the resistor R36 to the ADC pin of the microcontroller to detect the power, the second end of the amplifier U14 is connected between the first end of the amplifier U14 and the resistor R36, one end of the capacitor C86 is connected between the resistor R36 and the ADC pin of the microcontroller, and the other end of the capacitor C86 is grounded.

[0021] Further, the power supply module includes: an analog power supply circuit; The analog power supply circuit includes a digital power supply, and the digital power supply includes: capacitor C67, capacitor C68, capacitor C71, capacitor C72, inductor L7, and linear regulator U10; The Vin pin of the linear regulator U10 is connected to a 5V power supply, the Vout pin of the linear regulator U10 is connected in series with the inductor L7 to output a 3.3V voltage, and the GND pin of the linear regulator U10 is grounded; One end of the capacitor C71 is connected between the Vin pin of the linear regulator U10 and the 5V power supply, the other end of the capacitor C71 is grounded, and the capacitor C72 is connected in parallel across the capacitor C71; One end of the capacitor C67 is connected between the Vout pin of the linear regulator U10 and the inductor L7 , the other end of the capacitor C67 is grounded, and the capacitor C68 is connected in parallel across the capacitor C67 .

[0022] Further, the analog power supply circuit includes a first analog power supply for providing a -5V voltage, a second analog power supply for providing a +2.5V voltage, and a third analog power supply for providing a -2.5V voltage; The first analog power supply includes: a linear regulator U2, an inductor L1, an inductor L2, a capacitor C2, a capacitor C3, a capacitor C4, a capacitor C6, a capacitor C7, a capacitor C78, ​​and a capacitor C79; One end of the capacitor C6 is connected to a +5V voltage, and the other end of the capacitor C6 is grounded; The IN pin of the linear regulator U2 is connected in series with the inductor L1 and then connected to the capacitor C6, the OUT pin of the linear regulator U2 is connected in series with the inductor L2 and then outputs a -5V voltage, the CFLY+ pin of the linear regulator U2 is connected in series with the capacitor C79 and then connected to the CFLY- pin of the linear regulator U2, and the GND pin of the linear regulator U2 is grounded; One end of the capacitor C7 is connected between the inductor L1 and the IN pin of the linear regulator U2, the other end of the capacitor C7 is grounded, and the capacitor C78 is connected in parallel across the capacitor C7; One end of the capacitor C2 is connected between the inductor L2 and the OUT pin of the linear regulator U2, the other end of the capacitor C2 is grounded, and the capacitor C3 is connected in parallel to both ends of the capacitor C2; One end of the capacitor C4 is connected to the other end of the inductor L2 , and the other end of the capacitor C4 is grounded.

[0023] Furthermore, the analog front end adopts an integrated chip ADS1299, and each input pin of the integrated chip ADS1299 is connected in series with a protection resistor and a filter capacitor.

[0024] Furthermore, the main control chip adopts the chip STM32f411RCT6 with M4 core.

[0025] Furthermore, the control mainboard also includes a motion sensor and a Bluetooth module, and the motion sensor uses a chip LSM6DSL.

[0026] Furthermore, the connection component includes: An ear-hanging structure, which is connected to the front-end acquisition device, and the outer contour of the ear-hanging structure matches the auricle of the user, and is used to hook the auricle to support the front-end acquisition device; A rear ear support structure, which is arranged at the rear end of the ear hanging structure and has a support portion pressed against the connection between the ear root and the mastoid of the user; An elastic adjustment structure is connected between the behind-the-ear support structure and the control mainboard and is wavy in shape. Openings are provided at the crests and troughs of the elastic adjustment structure, and elastic ropes pass through the openings to connect the crests and troughs.

[0027] Compared with the prior art, the present invention has at least the following beneficial effects: The in-ear electrodes of the present invention have more signal channels and can provide higher spatial resolution. Compared with the existing in-ear bioelectric signal acquisition devices, the present invention can simultaneously acquire ear EEG signals and motion state information, providing more comprehensive physiological data, which is helpful for a wider range of application scenarios, such as sleep detection, cognitive assessment, emotion monitoring, etc. The present invention adopts memory foam earplugs and elastic support structures to improve the adaptability of in-ear electrodes to the ear canal, while ensuring the connection between the ear canal and the outside world, making it suitable for long-term use. At the same time, the present invention can collect ear EEG signals without the assistance of others, and users can wear them by themselves in a short time, which provides excellent wearing comfort and wearing experience; The present invention adopts active electrodes and multi-stage signal processing, including primary amplification, filtering, secondary amplification and analog-to-digital conversion, thereby improving the quality of collected signals. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0029] Figure 1 It is a schematic diagram of the electroencephalogram collection area in the prior art; Figure 2 is a cross-sectional view of the in-ear electrode of the present invention; Figure 3 is a front view of the ear-entry electrode of the present invention; Figure 4 This is a structural diagram of the control mainboard in the present invention; Figure 5 This is a flow chart of the acquisition and processing of middle ear EEG signals of the present invention; Figure 6 It is a structural schematic diagram of the connection assembly in the present invention; Figure 7 A circuit topology diagram of the front-end amplifier circuit in the present invention; Figure 8 This is a system framework diagram of the control mainboard in the present invention; Fig. 9 is a circuit topology diagram of the charging circuit in the present invention; Fig.10 A circuit topology diagram of the lithium battery power supply circuit in the present invention; Fig.11 A circuit topology diagram of the electric quantity detection circuit in the present invention; Fig.12 A circuit topology diagram of a digital power supply in the present invention; Fig.13 A circuit topology diagram of the first analog power supply in the present invention; Fig.14 is a circuit topology diagram of the second analog power supply in the present invention; Fig.15 is a circuit topology diagram of the third analog power supply in the present invention; Fig.16 A circuit topology diagram of the analog front end in the present invention; Fig.17 is a circuit topology diagram of the motion sensor in the present invention; Fig.18 The circuit topology diagram of the Bluetooth module in the present invention; Fig.19 This is a circuit topology diagram of the main control chip in the present invention; Fig. 20 It is the embedded software flow chart of the present invention; Fig.21 This is a schematic diagram of the data packet format in the present invention; Fig. 22 A schematic diagram of the base noise level of each channel in an embodiment of the present invention; Fig.23 This is the average time-frequency diagram of the Alpha rhythm in the upper channel of the left ear; Fig.24 This is the average time-frequency diagram of the Alpha rhythm in the upper channel of the right ear; Fig.25 This is the average time-frequency diagram of the Alpha rhythm in the lower channel of the left ear; Fig.26 This is the average time-frequency diagram of the Alpha rhythm in the Q1 area; Fig. 27 The waveform of the corresponding period of the alpha rhythm experiment in one embodiment of the present invention; Fig.28 for Fig. 27 Spectrum diagram corresponding to the embodiment; Fig.29 It is the power spectrum density of the collected signal under the stimulation of sound of different frequencies in the present invention. DETAILED DESCRIPTION

[0030] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0031] Thus, a feature indicated in this specification will be used to illustrate one of the features of an embodiment of the present invention, rather than implying that each embodiment of the present invention must have the described feature. In addition, it should be noted that this specification describes many features. Although some features can be combined together to illustrate possible system designs, these features can also be used in other combinations that are not explicitly described. Thus, unless otherwise stated, the described combinations are not intended to be limiting.

[0032] The principle and structure of the present invention are described in detail below with reference to the accompanying drawings and embodiments.

[0033] In view of the problems existing in the prior art, the present invention designs an in-ear multi-channel ear electroencephalogram signal acquisition device, which is mainly composed of three parts, namely a front-end acquisition device, a control mainboard, and a connection component; The present invention is described below with respect to the above three parts respectively. First, the front-end acquisition device is mainly divided into three parts, namely: an in-ear electrode, an earphone housing, and a front-end amplifier circuit; Here, the in-ear electrodes are used to collect ear EEG signals, the earphone shell is used to install the in-ear electrodes, and the front-end amplifier circuit is used to amplify the ear EEG signals collected by the in-ear electrodes. In order to solve the problem of the single signal acquisition channel in the prior art, the present invention designs multiple signal acquisition channels for collecting ear EEG signals when designing the in-ear electrodes. This design can provide EEG data with higher spatial resolution, which is conducive to accurate monitoring and analysis of the brain state.

[0034] Specifically, the in-ear electrode of the present invention comprises: a silicone earpiece tube, a memory foam earplug, and a plurality of metal conductive fabrics; The silicone earpiece tube is configured as a double-layer structure, and a copper wire is arranged between the two layers of the silicone earpiece tube. The memory foam earplug is coated on the outside of the silicone earpiece tube. The metal conductive fabric is used as a signal collection channel, which is assembled inside the memory foam earplug and connected to the copper wire.

[0035] See also Figure 2 In the present invention, the silicone earpiece tube is made of a rubber material with a certain rigidity, so that the earphone can still maintain the connection between the ear canal and the outside world when the sponge (here the sponge is mainly a memory sponge earplug) expands. The two layers of silicone tubes are Figure 2 The inner silicone tube and the outer silicone tube are used to fix the electrodes and lead out the copper wires for electrical connection with the metal wire fabric. The memory foam earplug can return to its original shape after being compressed, which is comfortable and easy to wear. After expanding in the ear canal, the pressure on the outer surface of the memory foam earplug is evenly redistributed, so that the in-ear electrode forms a good contact with the skin.

[0036] See also Figure 3 , when the in-ear electrode is used, the memory foam (also known as the memory foam earplug) is used as the base, and the conductive fabric (also known as the metal conductive fabric) is used as the electrode for collecting the ear EEG signal. In order to match the high level of compression required by the memory foam earplug before insertion, the electrode must be made of the same flexible but strong material. After testing, it was found that the use of adhesives and coatings on the surface of the base does not have the required firmness. First, the loose porous structure of the memory foam makes it impossible for the conductive coating to adhere firmly, and it will fall off after compression; second, the strength of the flexible adhesive after drying is not enough, and the hardness of the ordinary adhesive after curing is too high, which affects the wearing comfort. Finally, the present invention chooses to use a conductive fabric with a certain stretchability as the collection electrode. The connection between the electrode and the copper wire is fixed by a conductive adhesive, and the fixation of the electrode to the base is achieved by pre-stretching the electrode to a certain extent, and bonding it at the silicone earpiece tube inside the memory foam that does not contact the ear canal to ensure the wearing comfort.

[0037] Furthermore, the in-ear electrode comprises a reference electrode and a bias electrode, and both the reference electrode and the bias electrode are arranged in the earphone housing; The shape of the earphone shell matches the shape of the user's concha, so that the reference electrode is installed at the concha cavity and the bias electrode is installed at the concha cyna.

[0038] Specifically, the earphone shell is manufactured by 3D printing technology, and its shape fits the structure of the concha. The reference electrode is installed at the position corresponding to the concha cavity, and the bias electrode is installed at the position corresponding to the cymba concha. Both electrodes use gold-plated spring electrodes.

[0039] Among them, the earphone shell is also used to install the front-end amplifier circuit, which is used for the primary amplification of the ear electroencephalogram signal. The electrodes used in the present invention are all used as dry electrodes. In order to ensure the quality of collection, active electrodes are used, which can shield the electrodes from external interference and compensate for parasitic capacitance. This electrode is implemented using an integrated operational amplifier (i.e., a front-end amplifier circuit). The required operational amplifier has the following characteristics, including sufficiently low input reference noise, high input impedance and low bias current, low input reference offset, low output impedance, high common mode rejection ratio and power supply rejection ratio. All collection electrodes and reference electrodes are respectively connected to the input terminal of the operational amplifier, and the signal is led out and connected to the main circuit after preliminary amplification. At the same time, the main circuit supplies power to the front-end operational amplifier.

[0040] Specifically, the above-mentioned in-ear electrode production process is as follows: The in-ear electrodes are made of memory foam and silver fiber conductive cloth. The memory foam earplugs use 1100 noise-proof foam earplugs from 3M Company in the United States. The earplugs are too long and are shortened to 1 cm. Then a 4 mm diameter drill is used to drill through the earplugs axially. A 1 cm long, 5 mm outer diameter, 4 mm inner diameter silicone earpiece tube is installed in the hole as an electrode routing channel. The base part is completed.

[0041] Use a manual die-cutting punch to punch the silver fiber conductive fabric into a 2.5 cm, 2 mm wide rounded rectangle. Use a mixture of warm water and baking soda to clean the surface of the metal conductive fabric, wipe off excess water and dry it, use Kingstar K-818 nano silver ion conductive glue to bond the copper wire to one end of the cut metal conductive fabric, put it in an oven at 60°C for 45 minutes to heat and cure, and the flexible electrode is completed.

[0042] First, use ergo 6710 glue to fix the end of the electrode that is not connected to the wire to the inner wall of the silicone tube. Then, wrap the electrode around the outside of the sponge and return it to the catheter. Gently pull it in and use glue again to completely fix the electrode. Repeat this step to place the other three electrodes. The three electrodes are vertically distributed and do not touch each other. Finally, insert another silicone tube with an outer diameter of 3 mm and an inner diameter of 2 mm into the silicone tube, stick it in place, and the ear canal electrode is completed.

[0043] The production process of the above earphone shell is as follows: Use Shure SE535 as the earphone shell, or use 3D printing to make the shell. Drill holes with a diameter of 2.5 mm on the inner side of the earphone shell corresponding to the concha cavity and the hymen of the concha. Install gold-plated spring electrodes after chamfering, and use copper wires to lead out the contacts.

[0044] See also Figure 7The front-end amplifier circuit of the present invention specifically includes: resistor R4, resistor R5, resistor R6, capacitor C8, capacitor C9, capacitor C10, capacitor C16, amplifier U3, amplifier U17; The third terminal of the amplifier U3 is connected in series with the resistor R6 and then connected to the ear and brain electroencephalogram signal, the fourth terminal of the amplifier U3 is connected in series with the resistor R4 and then grounded, the first terminal of the amplifier U3 is connected to the third terminal of the amplifier U17, the fifth terminal of the amplifier U3 is connected to the positive electrode of the 2.5V power supply, and the second terminal of the amplifier U3 is connected to the negative electrode of the 2.5V power supply; The first end of the amplifier U17 is used to output the ear and brain electroencephalogram signal after primary amplification, the fourth end of the amplifier U17 is connected to the first end of the amplifier U17, the fifth end of the amplifier U17 is connected to the positive pole of the 2.5V power supply, and the second end of the amplifier U17 is connected to the negative pole of the 2.5V power supply; One end of the resistor R5 is connected between the resistor R4 and the fourth end of the amplifier U3, and the other end of the resistor R5 is connected between the first end of the amplifier U3 and the third end of the amplifier U17; One end of the capacitor C10 is connected between the fifth end of the amplifier U3 and the positive electrode of the 2.5V power supply, the other end of the capacitor C10 is grounded, and the capacitor C8 is connected in parallel across the capacitor C10; One end of the capacitor C9 is connected between the second end of the amplifier U3 and the negative electrode of the 2.5V power supply, the other end of the capacitor C9 is grounded, and the capacitor C16 is connected in parallel across the capacitor C9.

[0045] Based on the above structure, the manufacturing process of the front-end amplifier circuit in the present invention is as follows: The present invention uses AD8638 (both amplifiers U3 and U17 in the above text use this model) to design the front-end amplifier circuit. The operational amplifier has an input impedance of 22.5TΩ, which can improve the signal-to-noise ratio, reduce signal attenuation, and ensure that the signal can be stably collected when the contact impedance is high. At the same time, this preamplification can also reduce the noise pollution of the EEG signal during the long wire transmission process. Its core circuit is shown in Figure 7. Except for the electrode at the concha cavity, each electrode uses a unidirectional amplifier circuit composed of AD8638, with an amplification factor of 2. The amplified voltage is then stabilized by a voltage follower. The circuit board uses a double-layer board, the shape of which conforms to the internal structure of the earphone shell, and a connector is used to lead out the amplified signal and power supply line.

[0046] Lead the previously made in-ear electrode wires through the earphone shell into the ear hole, and insert the earphone shell into the silicone tube of the earplug. Adjust the wire length, and solder the wires connected to the electrodes in the ear canal and the wires connected to the spring electrodes to the corresponding positions of the front-end amplifier circuit board. Use glue to fix the circuit board in the earphone shell and then seal the shell.

[0047] Furthermore, the second component of the present invention is a control mainboard, which has at least an analog front end for converting ear and brain electroencephalogram signals into digital signals, a main control chip for receiving digital signals, and a power supply module for supplying power to the analog front end and the main control chip; In a preferred embodiment of the present invention, the control mainboard further includes a motion sensor and a Bluetooth module; Specifically, the control main board includes a microcontroller unit (MCU) and its embedded software design, EEG signal filtering, analog-to-digital conversion amplifier circuit, motion sensor module, power management and voltage conversion circuit and wireless communication module.

[0048] The control unit and its embedded software design here are the main control chip mentioned above, the EEG signal filtering and analog-to-digital conversion amplifier circuit is the analog front end mentioned above, the motion sensor module is the motion sensor mentioned above, the power management and voltage conversion circuit is the power module mentioned above, and the wireless communication module is the Bluetooth module mentioned above. The system architecture of the control motherboard is divided as follows: Figure 8 According to the above structure, it is mainly divided into analog front end, motion sensor, low-power Bluetooth, main control chip, and power module.

[0049] See also Figure 4 , the battery is transformed to power all modules, and the main control chip and each module communicate through their own communication protocols. The ear EEG signal collected by the electrode is filtered and amplified by the analog-to-digital conversion amplifier circuit, and finally converted into a digital signal by the analog-to-digital converter and sent to the MCU. The transmission path of the ear EEG signal is shown in Figure 5. In addition to the ear EEG signal, the present invention also uses a six-axis motion sensor to collect head movement information, and collects the remaining power of the lithium battery at intervals. The above data can be packaged and sent to the host computer.

[0050] The MCU communicates with the host computer via Bluetooth. All functions are integrated on a four-layer circuit board, which is powered by a lithium battery and has a Type-C interface for charging. In addition, there are two control buttons (on and off and reset) and four indicator lights (charging status, on and off status, Bluetooth connection status). The outer shell of the circuit board is designed with a certain curvature to fit the back of the head better.

[0051] See also Fig. 9 The power module of the present invention includes a charging circuit, and the charging circuit includes: a resistor R29, a resistor R30, a thermistor R31, a resistor R34, a capacitor C84, a capacitor C85, a light emitting diode LED1, a light emitting diode LED2, a fuse F2, an inductor L8, a bidirectional voltage regulator U12, and a charging management chip U11; One end of the fuse F2 is connected to the charging interface, the other end of the fuse F2 is connected to one end of the inductor L8, the other end of the inductor L8 is respectively connected to the CE pin of the charging management chip U11, the positive electrode of the light-emitting diode LED1, and the positive electrode of the light-emitting diode LED2, the negative electrode of the light-emitting diode LED1 is connected in series with a resistor R29 and then connected to the CHRG pin of the charging management chip U11, and the negative electrode of the light-emitting diode LED2 is connected in series with a resistor R30 and then connected to the STDBY pin of the charging management chip U11; The BAT pin of the charging management chip U11 outputs the charging voltage as the output end of the charging circuit, the TEMP pin and the GND pin of the charging management chip U11 are grounded, the PROG pin of the charging management chip U11 is connected in series with a resistor R34 and then grounded, and the VCC pin of the charging management chip U11 is connected between the inductor L8 and the CE pin of the charging management chip U11; One end of the thermistor R31 is connected between the charging port and the fuse F2, and the other end of the thermistor R31 is grounded; One end of the bidirectional voltage regulator U12 is connected between the fuse F2 and the inductor L8, and the other end of the bidirectional voltage regulator U12 is grounded; One end of the capacitor C84 is connected between the inductor L8 and the CE pin of the charging management chip U11, and the other end of the capacitor C84 is grounded.

[0052] Specifically, the charging circuit of the present invention uses TP4056 (i.e., the charging management chip U11 mentioned above) as a lithium battery charging management chip, which requires only a few peripheral components to use, and the charging voltage is fixed at 4.2V. When the connection is disconnected, the chip can automatically enter a sleep state, and the battery leakage current will drop to 1μA.

[0053] The charging interface uses a 16-pin Type-C interface, which is connected to the chip through filtering and protection circuits. The charging status is displayed by LED lights (there are two LEDs here, which are the light-emitting diodes D1 and D2 mentioned above). The red light is always on when the battery is charging, and the red light goes out when it is full, and the green light turns on.

[0054] The temperature detection of the chip is not used this time, so the TEMP pin is directly grounded. The charging current is set by the external resistor R34. The current charging current is about 800mA with an error of 10%. When the charging current is reduced to one tenth of the maximum value, charging is completed and the chip enters shutdown mode.

[0055] See also Fig.10 and Fig.11 , the power module in the present invention includes: a lithium battery power supply circuit and a power detection circuit; The lithium battery power supply circuit includes: resistor R7, resistor R8, resistor R9, resistor R10, resistor R11, capacitor C56, capacitor C57, capacitor C58, fuse F1, inductor L6, voltage regulator U9, switch TA-3525, connector U6, and voltage regulator U7; A first end of the switch TA-3525 is connected to a second end of the connector U6, a second end of the switch TA-3525 is connected in series with a fuse F1 and a resistor R7 and then connected to an EN pin of a voltage regulator U7, and a third end of the switch TA-3525 is grounded; One end of the resistor R10 is connected between the fuse F1 and the resistor R7, and the other end of the resistor R10 is connected in series with the resistor R11 and then grounded; one end of the capacitor C57 is connected between the fuse F1 and the resistor R7, and the other end of the capacitor C57 is grounded; one end of the capacitor C58 is connected between the fuse F1 and the resistor R7, and the other end of the capacitor C58 is grounded; The NC pin of the voltage regulator U7 is vacant, the IN pin of the voltage regulator U7 is connected between the fuse F1 and the resistor R7, the GND pin of the voltage regulator U7 is grounded, the FB pin of the voltage regulator U7 is connected in series with the resistor R9 and then connected to the positive electrode of the 5V power supply, one end of the resistor R8 is connected between the GND pin of the voltage regulator U7 and the ground, the other end of the resistor R8 is connected between the FB pin of the voltage regulator U7 and the resistor R9, one end of the capacitor C56 is connected between the GND pin of the voltage regulator U7 and the ground, the other end of the capacitor C56 is connected between the positive electrode of the 5V power supply and the resistor R9; One end of the inductor L6 is connected to the IN pin of the voltage regulator U7, the other end of the inductor L6 is connected to the positive electrode of the voltage regulator U9, the negative electrode of the voltage regulator U9 is connected between the positive electrode of the 5V power supply and the resistor R9, and the SW pin of the voltage regulator U7 is connected between the inductor L6 and the voltage regulator U9.

[0056] The power detection circuit includes: resistor R35, resistor R36, capacitor C86, and amplifier U14; The third end of the amplifier U14 is connected in series with the resistor R35 to receive the power supply voltage of the lithium battery. The first end of the amplifier U14 is connected in series with the resistor R36 and then connected to the ADC pin of the microcontroller to detect the power. The second end of the amplifier U14 is connected between the first end of the amplifier U14 and the resistor R36. One end of the capacitor C86 is connected between the resistor R36 and the ADC pin of the microcontroller, and the other end of the capacitor C86 is grounded.

[0057] In practical applications, the standard voltage of lithium batteries is 3.7V, but its output voltage varies with the power level, usually ranging from 2.8V to 4.2V. In addition, some modules require a 5V power supply voltage, so the battery output voltage needs to be boosted and stabilized. This design uses CJ9340T6 (also known as the regulator U7 mentioned above) to boost and stabilize the power supply. CJ9340T6 is a boost switching regulator for small, low-power devices. Its input voltage range is 2V to 24V, and its output voltage can reach up to 28V. It has undervoltage lockout, current limiting and overheating protection functions.

[0058] The peripheral circuit of the battery part is shown in Figure 10. The output voltage is set by the resistance value of the external resistor divider connected to the FB pin. The calculation formula is as follows: ; The voltage of the FB pin is 0.6V. To ensure accurate output, the voltage divider resistor needs to be a high-precision resistor. This time, R8 is 3kΩ and R9 is 25kΩ. The theoretical output voltage value is 5.6V. The converted voltage also needs to be stabilized before it can power other modules.

[0059] The lithium battery power supply voltage will drop as the power is consumed. Here, R10 and R11 are used to divide the power supply voltage, and the LM358 op amp (that is, amplifier U14 in the previous article) is used as a voltage follower to protect the output voltage from interference. The stabilized voltage is then connected to the microcontroller ADC pin for collection to detect the battery power.

[0060] See also Fig.12 ,The power module includes: an analog power supply circuit; The analog power supply circuit includes a digital power supply, and the digital power supply includes: capacitor C67, capacitor C68, capacitor C71, capacitor C72, inductor L7, and linear regulator U10; The Vin pin of the linear regulator U10 is connected to a 5V power supply, the Vout pin of the linear regulator U10 is connected in series with the inductor L7 to output a 3.3V voltage, and the GND pin of the linear regulator U10 is grounded; One end of the capacitor C71 is connected between the Vin pin of the linear regulator U10 and the 5V power supply, the other end of the capacitor C71 is grounded, and the capacitor C72 is connected in parallel across the capacitor C71; One end of the capacitor C67 is connected between the Vout pin of the linear regulator U10 and the inductor L7, the other end of the capacitor C67 is grounded, and the capacitor C68 is connected in parallel across the capacitor C67.

[0061] The module power supply circuit can be divided into two parts: digital power supply and analog power supply, which are obtained by voltage conversion of battery output.

[0062] The above part is attached Fig.12 The introduction mainly focuses on the digital power supply part, which mainly provides 3.3V power supply for the microcontroller, motion sensor, Bluetooth module and ADS1299 digital power supply. The specific circuit is shown in Figure 12. Here, the XC6206 linear regulator (that is, the linear regulator U10 mentioned above) is used to convert 5V to 3.3V.

[0063] See also Figures 13 to 15 , the analog power supply circuit includes a first analog power supply for providing a -5V voltage, a second analog power supply for providing a +2.5V voltage, and a third analog power supply for providing a -2.5V voltage; The first analog power supply includes: a linear regulator U2, an inductor L1, an inductor L2, a capacitor C2, a capacitor C3, a capacitor C4, a capacitor C6, a capacitor C7, a capacitor C78, ​​and a capacitor C79; One end of capacitor C6 is connected to +5V voltage, and the other end of capacitor C6 is grounded; The IN pin of the linear regulator U2 is connected in series with the inductor L1 and then connected to the capacitor C6. The OUT pin of the linear regulator U2 is connected in series with the inductor L2 and then outputs a -5V voltage. The CFLY+ pin of the linear regulator U2 is connected in series with the capacitor C79 and then connected to the CFLY- pin of the linear regulator U2. The GND pin of the linear regulator U2 is grounded. One end of the capacitor C7 is connected between the inductor L1 and the IN pin of the linear regulator U2, the other end of the capacitor C7 is grounded, and the capacitor C78 is connected in parallel across the capacitor C7; One end of the capacitor C2 is connected between the inductor L2 and the OUT pin of the linear regulator U2, the other end of the capacitor C2 is grounded, and the capacitor C3 is connected in parallel across the capacitor C2; One end of the capacitor C4 is connected to the other end of the inductor L2, and the other end of the capacitor C4 is grounded.

[0064] here Figures 13 to 15 They correspond to the first analog power supply, the second analog power supply and the third analog power supply respectively. Since the circuit topologies of the three analog power supplies are basically the same, only the connection method of the first analog circuit is introduced here.

[0065] The analog power supply is mainly used to power the analog front end and the front end amplifier circuit. In order to obtain better stability, a positive and negative dual power supply is selected: AVDD is +2.5V and AVSS is -2.5V. The specific circuit is shown in Figure 13 to Fig.15As shown in the figure, the boosted 5V voltage is reversed to -5V after passing through the switching regulator, and the ±5V is stepped down to ±2.5V by the linear regulator to power the ADS1299 analog power supply. In order to reduce the noise of the power supply as much as possible, the chips used here are all high-precision regulators from Texas Instruments. In addition, multiple groups of ceramic capacitors are placed near the power chip to reduce the coupling noise between the power supply and the ground.

[0066] See also Fig.16 The analog front end adopts the integrated chip ADS1299, and each input pin of the integrated chip ADS1299 is connected in series with a protection resistor and a filter capacitor.

[0067] The EEG signal is a weak low-frequency signal and is easily interfered by noise. Usually, the EEG signal acquisition needs to go through pre-amplification, filtering, multi-stage amplification, analog-to-digital conversion and other operations to obtain high-quality EEG signals. However, from the perspective of portability and cost, the integrated chip ADS1299 produced by Texas Instruments is used here to achieve signal amplification and analog-to-digital conversion. The specific peripheral circuit design can be referred to, and the specific circuit topology is as follows: Fig.16 As shown, the low-pass filter circuit is omitted here: each input pin is connected in series with a 4.7kΩ resistor and a 4.7nF capacitor. The resistor plays a protective role, and the capacitor is used to filter out high-frequency noise and improve signal quality.

[0068] In addition to the bypass capacitors used for noise reduction, the RESET pin, CLKSEL pin, and PWDN pin of the integrated chip ADS1299 are set to high level using pull-up resistors, and the chip ADS1299 is set to use the internal clock source signal to ensure that the chip ADS1299 can be reset and shut down through the SPI instruction software control chip. The BIASOUT pin filters the collected signal and outputs it to the electrodes at the concha of both ears to suppress common-mode interference.

[0069] See also Fig.17 and Fig.18 , the circuits of the motion sensor and Bluetooth parts are relatively simple.

[0070] The motion sensor uses ST's chip LSM6DSL, which has an operating current of only 0.65mA in high-performance mode, a compact size, and supports both SPI and integrated circuit bus (I2C) interfaces, such as Fig.17 As shown in this design, SPI is used for communication.

[0071] The Bluetooth module uses customized Bluetooth from Hongjia Electronics, which is only 5mm*5mm*1.3mm in size. It supports low-power Bluetooth protocol and serial port flow control to achieve high communication rate and lowest packet loss rate. The peak current of sending and receiving is less than 1.6mA, with low power consumption and small size, which is very suitable for use in wearable devices.

[0072] See also Fig.19 The main control chip is the STM32f411RCT6 chip from ST using the M4 core. The chip is rich in resources. This design uses two groups of SPI, one group of UART, one ADC and multiple IO control ports to realize the collection and data transmission functions.

[0073] Specific circuit Fig.19 As shown, the SPI1 of the microcontroller communicates with the chip ADS1299 through DMA to control the chip ADS1299 to collect data; SPI2 communicates with the six-axis sensor LSM6DSL to read the accelerometer and gyroscope data; ADC1 converts the power supply voltage data, and all the data are packaged and sent to the Bluetooth module through the serial port and then transmitted to the host computer.

[0074] After the circuit is designed, layout and wiring are carried out, and a 4-layer circuit board is used. The top and bottom layers are signal layers, the bottom layer is mainly the chip ADS1299 and peripheral circuits, the top layer is the charging circuit and other components, the middle layer is the power layer and the ground layer, and all four layers are copper-plated for grounding. The analog ground and digital ground are separated by about 2.5mm, and a 0Ω resistor is used for single-point connection to make the potential at both ends equal.

[0075] After the board is printed, power on to detect that the power supply voltage at specific locations is accurate, and the charging and switching functions are normal.

[0076] See also Figure 6 , the connection assembly in the present invention comprises: An ear-hanging structure, which is connected to the front-end collection device, and the outer contour of the ear-hanging structure matches the auricle of the user, and is used to hook the auricle to support the front-end collection device; The rear ear support structure is arranged at the rear end of the ear hanging structure and has a support portion pressed against the connection between the ear root and the mastoid of the user; The elastic adjustment structure is connected between the behind-the-ear support structure and the control mainboard, and is shaped like a wave. Openings are provided at the crests and troughs of the elastic adjustment structure, and elastic ropes pass through the openings to connect the crests and troughs.

[0077] The elastic adjustment structure can be adjusted in size through the elastic rope. Figure 6 The size adjustment structure can adapt to the user's ear canal for assembly, improving the user's comfort.

[0078] The above is a description of the components of the three parts of the present invention: the front-end acquisition device, the control mainboard, and the connection components.

[0079] To further realize the above control, the main control chip in the control mainboard of the present invention also adopts embedded software design. The setting of the embedded software design in the present invention is described below: See also Fig. 20 and Fig.21 The embedded software design in the present invention mainly involves the following parts: SPI transmission program for communication between the single-chip microcomputer and the chip ADS1299, chip ADS1299 transmission interrupt response program, chip ADS1299 I / O control program, power supply and quantity detection program, SPI transmission program for communication with the chip LSM6DSL, serial port transmission program for communication with the Bluetooth module, data packaging and sending program, and host computer instruction decoding program. The above functions are realized by programming using the library functions of the Hardware Abstraction Layer (HAL).

[0080] The main process of device operation is shown in Figure 20. The left side is the program operation process, with the focus on the initialization of each module and the main function corresponding to the instructions.

[0081] After the system is powered on, the system and each functional module are initialized. After the initialization is completed, it waits for the host computer's instructions. When receiving the host computer's setting instructions, it disassembles the command according to the specified protocol to determine the execution task.

[0082] On the right are the basic types of instructions, which are divided into four types.

[0083] (1) Setting instructions: When receiving a setting instruction, the system will first stop all data transmission and decompose the instruction to set the system function, such as the sampling rate of the chip ADS1299, the motion sensor acquisition mode, etc., and set it according to the instruction requirements.

[0084] (2) Start acquisition command: When the command to start acquisition is received, the low power mode is exited and the data of each module is acquired according to the settings. Then, at the end of each data conversion of the chip ADS1299 (triggering the interrupt of the microcontroller), the data is packaged according to the set data packet format. The specific format is shown in Figure 21. The packaged data is finally sent to Bluetooth through the serial port.

[0085] (3) Stop acquisition command: When receiving the stop acquisition command, the system stops data transmission after sending the complete current data packet, and then shuts down the data conversion of each module. If the stop time reaches 5 minutes, the system enters low power mode.

[0086] (4) Restart command: After receiving the restart command, the system software is reset to restore the system settings to the default settings.

[0087] The detection results of the present invention are analyzed and explained below in conjunction with a specific embodiment of the present invention: After the device is manufactured, the serial port assistant tool is used on the computer to send the setting command. The functions are normal, data transmission can be performed, and the internal test square wave of the chip is read and displayed normally. When the channel is short-circuited, the base noise of the system is measured as shown in Figure 22. Fig. 22 (a) is the interpolation of the maximum and minimum noise values ​​of each channel, which is about 1.1μV; Fig. 22 (b) is the root mean square (RMS) of each channel noise, which is about 0.14μV. The test results show that the device base noise is small.

[0088] In order to verify whether the device can achieve the intended purpose, an alpha wave rhythm experiment was designed for preliminary verification.

[0089] Alpha wave rhythm is a kind of spontaneous EEG activity, also known as Berger rhythm, which was first discovered by Hans Berger. The phenomenon of this spontaneous activity is that when a person closes his eyes, the alpha activity will be enhanced, that is, the signal in the 8-12Hz frequency band in the spectrum will be enhanced, and when the eyes are open, the signal in this frequency band will be blocked.

[0090] This phenomenon is very obvious in the occipital area, so we chose to detect this activity to test whether the acquisition system is functioning normally. The experiment simultaneously collected EEG signals from both ears and the O1 site in the occipital area.

[0091] The experimental program was written using Psychopy. The experiment was conducted in a quiet environment with a noise intensity of no more than 35 decibels. The subjects sat in front of a computer screen, and the computer reminded the subjects to open and close their eyes through text and sound playback. During the experiment, the subjects were required to keep their heads stable and minimize body movements such as blinking. During the period of opening their eyes, the subjects were required to look at the cross arrow in the center of the screen, prepare to close their eyes after hearing the "beep", and then close their eyes after the "beep"; similarly, when closing their eyes, they opened their eyes after hearing the beep, and the time for opening and closing their eyes was 15 seconds each.

[0092] Figure 23 to Fig.26 The average spectrum of 5 experiments (one experiment with eyes open and closed) is shown. Here, the spectrum of the upper and lower channels of the left ear, the upper channel of the right ear, and the spectrum of the O1 area of ​​the scalp EEG are selected. Fig.23 This is the spectrum diagram of the left ear upper channel. Fig.24 This is the spectrum diagram of the upper channel of the right ear. Fig.25 This is the spectrum diagram of the left ear lower channel. Fig.26 This is the spectrum diagram of the O1 area of ​​the scalp EEG. The O1 area of ​​the scalp EEG is also the occipital area that is prone to alpha wave rhythm as mentioned above.

[0093] It can be seen that when the subjects closed their eyes, the scalp and ear EEG showed an increase in power except for the Alpha band. The signal strength of the lower left ear was slightly lower, and the ear signal was not as strong as the signal strength of the O1 area, which is consistent with the results of previous studies.

[0094] Then the data of left ear channel 1 is analyzed, and a section of continuous eye opening and closing data is taken. The results are as follows Fig. 27 and Fig.28 As shown, Fig. 27 A in the middle is an indication of the state of the eyes; Fig. 27 Middle B is the original waveform; Fig. 27 Middle C is the waveform obtained by filtering the original waveform with a fifth-order Butterworth filter at 7-12Hz bandpass; Fig.28 This is the spectrum diagram corresponding to this segment of original data.

[0095] It can be seen that both the spectrum and waveform data can prove that the device can detect the increase in the intensity of the Alpha frequency band of the EEG signal when the eyes are closed. This result shows that the acquisition system has the ability to collect EEG signals.

[0096] In order to further test the acquisition performance of the system, an auditory steady-state evoked response (ASSR) experiment was designed for further verification. Auditory steady-state evoked potential is a steady-state EEG response induced by continuous modulated sound stimulation. This response corresponds to the frequency of the sound stimulation signal and has a stable phase relationship within a certain frequency range.

[0097] The stimulation sounds in this experiment were amplitude modulated signals obtained by amplitude modulating a 1000Hz sinusoidal carrier signal with 38Hz, 40Hz, and 42Hz sinusoidal signals, and randomly generated Gaussian white noise. The subjects were exposed to the sound stimulation for two minutes with their eyes closed.

[0098] The environmental requirements of the experiment are basically the same as those of the alpha rhythm experiment. Both need to be conducted in an environment without noise interference. The sound level of the experimental stimulus is set to 75 decibels during the experiment.

[0099] Figure 29 is a signal power spectrum diagram corresponding to different stimulation sounds in the auditory steady-state evoked potential experiment, in which A, B and C are the power spectrum density of the auricle EEG signal under 38 Hz, 40 Hz and 42 Hz sound stimulation respectively. It can be observed that under the stimulation of the corresponding frequency sound, the ear EEG signal shows a clear neural response.

[0100] When white noise was used for stimulation, no response occurred. In addition, in order to reduce the interference caused by blinking, the subjects were asked to close their eyes for testing. Here, we can also see the same results as in the alpha rhythm experiment. This result shows that the device can detect auditory-based responses.

[0101] In summary, compared with the prior art, the present invention has at least the following beneficial effects: 1. The in-ear electrodes of the present invention have more signal channels and can provide higher spatial resolution. Compared with the existing in-ear bioelectric signal acquisition equipment, the present invention can simultaneously collect ear EEG signals and motion state information, providing more comprehensive physiological data, which is helpful for a wider range of application scenarios, such as sleep detection, cognitive assessment, emotion monitoring, etc.; 2. The present invention adopts memory foam earplugs and elastic support structures to improve the adaptability of in-ear electrodes to the ear canal, while ensuring the connection between the ear canal and the outside world, making it suitable for long-term use. At the same time, the present invention can collect ear EEG signals without the assistance of others, and users can wear them by themselves in a short time, which provides excellent wearing comfort and wearing experience; 3. The present invention adopts active electrodes and multi-stage signal processing, including primary amplification, filtering, secondary amplification and analog-to-digital conversion, which improves the quality of the collected signal.

[0102] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An in-ear multi-channel electroencephalogram signal acquisition device, characterized in that: include: A front-end acquisition device, which is used to be worn on the ear of the user to collect ear electroencephalogram signals, and the front-end acquisition device has an in-ear electrode, an earphone shell for installing the in-ear electrode, and a front-end amplification circuit for amplifying the ear electroencephalogram signals, and the in-ear electrode has a plurality of signal acquisition channels for collecting the ear electroencephalogram signals; A control mainboard, which at least has an analog front end for converting the ear and brain electroencephalogram signals into digital signals, a main control chip for receiving the digital signals, and a power supply module for supplying power to the analog front end and the main control chip; A connecting component is used to connect and fix the front-end acquisition device and the control mainboard.

2. The in-ear multi-channel EEG signal acquisition device according to claim 1, characterized in that: The in-ear electrode comprises: a silicone earpiece tube, a memory foam earplug, and a plurality of metal conductive fabrics; The silicone earpiece tube is configured as a double-layer structure, and a copper wire is disposed between the two layers of the silicone earpiece tube. The memory foam earplug is coated on the outside of the silicone earpiece tube. The metal conductive fabric is used as the signal acquisition channel and is assembled inside the memory foam earplug, and is connected to the copper wire inside the memory foam earplug.

3. The in-ear multi-channel EEG signal acquisition device according to claim 2, characterized in that: The in-ear electrode comprises a reference electrode and a bias electrode, and both the reference electrode and the bias electrode are arranged in the earphone housing; The shape of the earphone shell matches the shape of the user's concha, so that the reference electrode is installed at the concha cavity and the bias electrode is installed at the cymba concha.

4. The in-ear multi-channel electroencephalogram signal acquisition device according to claim 1, characterized in that: The front-end amplifier circuit includes: resistor R4, resistor R5, resistor R6, capacitor C8, capacitor C9, capacitor C10, capacitor C16, amplifier U3, amplifier U17; The third end of the amplifier U3 is connected in series with the resistor R6 and then connected to the ear and brain electroencephalogram signal, the fourth end of the amplifier U3 is connected in series with the resistor R4 and then grounded, the first end of the amplifier U3 is connected to the third end of the amplifier U17, the fifth end of the amplifier U3 is connected to the positive electrode of the 2.5V power supply, and the second end of the amplifier U3 is connected to the negative electrode of the 2.5V power supply; The first end of the amplifier U17 is used to output the ear and brain electroencephalogram signal after primary amplification, the fourth end of the amplifier U17 is connected to the first end of the amplifier U17, the fifth end of the amplifier U17 is connected to the positive pole of the 2.5V power supply, and the second end of the amplifier U17 is connected to the negative pole of the 2.5V power supply; One end of the resistor R5 is connected between the resistor R4 and the fourth end of the amplifier U3, and the other end of the resistor R5 is connected between the first end of the amplifier U3 and the third end of the amplifier U17; One end of the capacitor C10 is connected between the fifth end of the amplifier U3 and the positive electrode of the 2.5V power supply, the other end of the capacitor C10 is grounded, and the capacitor C8 is connected in parallel to both ends of the capacitor C10; One end of the capacitor C9 is connected between the second end of the amplifier U3 and the negative electrode of the 2.5V power supply, the other end of the capacitor C9 is grounded, and the capacitor C16 is connected in parallel across the capacitor C9.

5. The in-ear multi-channel EEG signal acquisition device according to claim 1, characterized in that: The power module includes a charging circuit, which includes: a resistor R29, a resistor R30, a thermistor R31, a resistor R34, a capacitor C84, a capacitor C85, a light emitting diode LED1, a light emitting diode LED2, a fuse F2, an inductor L8, a bidirectional voltage regulator U12, and a charging management chip U11; One end of the fuse F2 is connected to the charging interface, the other end of the fuse F2 is connected to one end of the inductor L8, the other end of the inductor L8 is respectively connected to the CE pin of the charging management chip U11, the positive electrode of the light-emitting diode LED1, and the positive electrode of the light-emitting diode LED2, the negative electrode of the light-emitting diode LED1 is connected in series with the resistor R29 and then connected to the CHRG pin of the charging management chip U11, and the negative electrode of the light-emitting diode LED2 is connected in series with the resistor R30 and then connected to the STDBY pin of the charging management chip U11; The BAT pin of the charging management chip U11 outputs the charging voltage as the output end of the charging circuit, the TEMP pin and the GND pin of the charging management chip U11 are grounded, the PROG pin of the charging management chip U11 is connected in series with the resistor R34 and then grounded, and the VCC pin of the charging management chip U11 is connected between the inductor L8 and the CE pin of the charging management chip U11; One end of the thermistor R31 is connected between the charging port and the fuse F2, and the other end of the thermistor R31 is grounded; One end of the bidirectional voltage regulator U12 is connected between the fuse F2 and the inductor L8, and the other end of the bidirectional voltage regulator U12 is grounded; One end of the capacitor C84 is connected between the inductor L8 and the CE pin of the charging management chip U11, and the other end of the capacitor C84 is grounded.

6. The in-ear multi-channel EEG signal acquisition device according to claim 1, characterized in that: The power module includes: a lithium battery power supply circuit and a power detection circuit; The lithium battery power supply circuit includes: resistor R7, resistor R8, resistor R9, resistor R10, resistor R11, capacitor C56, capacitor C57, capacitor C58, fuse F1, inductor L6, voltage regulator U9, switch TA-3525, connector U6, and voltage regulator U7; The first end of the switching switch TA-3525 is connected to the second end of the connector U6, the second end of the switching switch TA-3525 is connected in series with the fuse F1 and the resistor R7 and then connected to the EN pin of the voltage regulator U7, and the third end of the switching switch TA-3525 is grounded; One end of the resistor R10 is connected between the fuse F1 and the resistor R7, and the other end of the resistor R10 is connected in series with the resistor R11 and then grounded; one end of the capacitor C57 is connected between the fuse F1 and the resistor R7, and the other end of the capacitor C57 is grounded; one end of the capacitor C58 is connected between the fuse F1 and the resistor R7, and the other end of the capacitor C58 is grounded; The NC pin of the voltage regulator U7 is vacant, the IN pin of the voltage regulator U7 is connected between the fuse F1 and the resistor R7, the GND pin of the voltage regulator U7 is grounded, the FB pin of the voltage regulator U7 is connected in series with the resistor R9 and then connected to the positive electrode of the 5V power supply, one end of the resistor R8 is connected between the GND pin of the voltage regulator U7 and the ground, and the other end of the resistor R8 is connected between the FB pin of the voltage regulator U7 and the resistor R9, one end of the capacitor C56 is connected between the GND pin of the voltage regulator U7 and the ground, and the other end of the capacitor C56 is connected between the positive electrode of the 5V power supply and the resistor R9; One end of the inductor L6 is connected to the IN pin of the voltage regulator U7, the other end of the inductor L6 is connected to the positive electrode of the voltage regulator U9, the negative electrode of the voltage regulator U9 is connected between the positive electrode of the 5V power supply and the resistor R9, and the SW pin of the voltage regulator U7 is connected between the inductor L6 and the voltage regulator U9.

7. The in-ear multi-channel electroencephalogram signal acquisition device according to claim 6, characterized in that: The power detection circuit includes: a resistor R35, a resistor R36, a capacitor C86, and an amplifier U14; The third end of the amplifier U14 is connected in series with the resistor R35 to receive the power supply voltage of the lithium battery, the first end of the amplifier U14 is connected in series with the resistor R36 to the ADC pin of the microcontroller to detect the power, the second end of the amplifier U14 is connected between the first end of the amplifier U14 and the resistor R36, one end of the capacitor C86 is connected between the resistor R36 and the ADC pin of the microcontroller, and the other end of the capacitor C86 is grounded.

8. The in-ear multi-channel EEG signal acquisition device according to claim 1, characterized in that: The power supply module includes: an analog power supply circuit; The analog power supply circuit includes a digital power supply, and the digital power supply includes: capacitor C67, capacitor C68, capacitor C71, capacitor C72, inductor L7, and linear regulator U10; The Vin pin of the linear regulator U10 is connected to a 5V power supply, the Vout pin of the linear regulator U10 is connected in series with the inductor L7 to output a 3.3V voltage, and the GND pin of the linear regulator U10 is grounded; One end of the capacitor C71 is connected between the Vin pin of the linear regulator U10 and the 5V power supply, the other end of the capacitor C71 is grounded, and the capacitor C72 is connected in parallel across the capacitor C71; One end of the capacitor C67 is connected between the Vout pin of the linear regulator U10 and the inductor L7 , the other end of the capacitor C67 is grounded, and the capacitor C68 is connected in parallel across the capacitor C67 .

9. The in-ear multi-channel electroencephalogram signal acquisition device according to claim 8, characterized in that: The analog power supply circuit also includes a first analog power supply for providing a -5V voltage, a second analog power supply for providing a +2.5V voltage, and a third analog power supply for providing a -2.5V voltage; The first analog power supply includes: a linear regulator U2, an inductor L1, an inductor L2, a capacitor C2, a capacitor C3, a capacitor C4, a capacitor C6, a capacitor C7, a capacitor C78, ​​and a capacitor C79; One end of the capacitor C6 is connected to a +5V voltage, and the other end of the capacitor C6 is grounded; The IN pin of the linear regulator U2 is connected in series with the inductor L1 and then connected to the capacitor C6, the OUT pin of the linear regulator U2 is connected in series with the inductor L2 and then outputs a -5V voltage, the CFLY+ pin of the linear regulator U2 is connected in series with the capacitor C79 and then connected to the CFLY- pin of the linear regulator U2, and the GND pin of the linear regulator U2 is grounded; One end of the capacitor C7 is connected between the inductor L1 and the IN pin of the linear regulator U2, the other end of the capacitor C7 is grounded, and the capacitor C78 is connected in parallel across the capacitor C7; One end of the capacitor C2 is connected between the inductor L2 and the OUT pin of the linear regulator U2, the other end of the capacitor C2 is grounded, and the capacitor C3 is connected in parallel to both ends of the capacitor C2; One end of the capacitor C4 is connected to the other end of the inductor L2 , and the other end of the capacitor C4 is grounded.

10. The in-ear multi-channel electroencephalogram signal acquisition device according to claim 1, characterized in that: The analog front end adopts an integrated chip ADS1299, and each input pin of the integrated chip ADS1299 is connected in series with a protection resistor and a filter capacitor.

11. The in-ear multi-channel electroencephalogram signal acquisition device according to claim 1, characterized in that: The main control chip adopts the chip STM32f411RCT6 with M4 core.

12. The in-ear multi-channel electroencephalogram signal acquisition device according to claim 1, characterized in that: The control mainboard also includes a motion sensor and a Bluetooth module, and the motion sensor uses a chip LSM6DSL.

13. The in-ear multi-channel electroencephalogram signal acquisition device according to claim 1, characterized in that: The connection component comprises: An ear-hanging structure, which is connected to the front-end acquisition device, and the outer contour of the ear-hanging structure matches the auricle of the user, and is used to hook the auricle to support the front-end acquisition device; A rear ear support structure, which is arranged at the rear end of the ear hanging structure and has a support portion pressed against the connection between the ear root and the mastoid of the user; An elastic adjustment structure is connected between the behind-the-ear support structure and the control mainboard and is wavy in shape. Openings are provided at the crests and troughs of the elastic adjustment structure, and elastic ropes pass through the openings to connect the crests and troughs.

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