Non-conductive paste dry brain electrical electrode structure and scalp impedance self-adaptive matching method

Abstract

The application relates to the field of electroencephalogram signal collection, and discloses a dry electroencephalogram electrode structure without conductive paste and a scalp impedance self-adaptive matching method. The structure comprises a wearing support structure, a micro-actuator, an electrode base, a micro-whisker array, an impedance sensing unit and a signal matching unit. The impedance sensing unit obtains the ohm component of the scalp contact impedance, and a control unit drives the micro-actuator to adjust the physical adhesion pressure of the micro-whisker array and the scalp according to the ohm component, and writes the adaptive parameters into the signal matching unit for circuit reconstruction after mechanical adjustment is completed. The application combines the dynamic adjustment of the physical pressure and the self-adaptive matching of the circuit parameters, cooperates with a power-off self-locking mechanism and a sample-and-hold circuit, can overcome the interface impedance fluctuation caused by individual differences, blocks the electromagnetic and electromechanical interference in the adjustment process, and improves the signal collection quality and the anti-interference ability of the dry electroencephalogram electrode in the long-term wearing environment.

Description

Technical Field

[0001] This invention relates to the field of electroencephalogram (EEG) signal acquisition technology, specifically to a dry EEG electrode structure free from conductive gel and a method for adaptive matching of scalp impedance. Background Technology

[0002] Electroencephalogram (EEG) signals are important physiological electrical signals reflecting brain neural activity and have wide applications in brain-computer interfaces, sleep monitoring, and neurophysiological examinations. Traditional wet EEG electrodes require cleaning the scalp and applying conductive gel to reduce contact impedance before measurement. This process is cumbersome, and signal quality deteriorates as the conductive gel dries, making them unsuitable for prolonged wear in everyday environments. While dry electrodes, which do not require conductive gel, solve these convenience issues, the lack of a conductive buffer means that the conductive contacts are limited by individual scalp shape, hair density, and wearing position. The contact impedance between the electrode and scalp is typically high and prone to fluctuation, easily leading to EEG signal attenuation.

[0003] To reduce the contact resistance of dry electrodes, existing acquisition devices typically rely on an external headband or spring structure to apply a fixed mechanical static pressure, causing the electrode contacts to penetrate the hair and adhere tightly to the scalp. However, this fixed mechanical support cannot adapt to changes in fit caused by head movements and scalp relaxation during prolonged wear. Insufficient pressure leads to poor contact, while excessive pressure causes discomfort. Some technical solutions incorporate motors or electromagnetic drives to dynamically adjust the electrode pressure, but these active actuators continuously consume electrical energy when adjusting or maintaining the pressure. Furthermore, the electromagnetic radiation generated by the coils inside the drive device can directly interfere with the weak simulated EEG signals, creating hardware interference that is difficult to filter out using conventional filtering methods.

[0004] At the electronics level, the high impedance characteristics of dry electrodes require the back-end signal acquisition circuit to have corresponding impedance matching capabilities. In practical use, due to changes in the physical state of the contact interface, the polarization capacitance and contact resistance of the electrodes will dynamically shift, making it difficult for the fixed front-end circuit to maintain a matching state. Especially in multi-channel EEG array acquisition systems, there are significant differences in the scalp contact state at the location of different acquisition channels. This interface impedance imbalance between channels disrupts the symmetry of the amplifier input, resulting in a significant decrease in the system's common-mode rejection ratio for power frequency and environmental electromagnetic noise, ultimately causing the effective EEG signal to be covered by common-mode interference. Summary of the Invention

[0005] The technical problem solved by this invention is that, during long-term wear, existing dry EEG electrodes are easily affected by factors such as individual scalp conditions, hair obstruction, and movement, causing changes in the contact impedance between the electrode and the scalp, resulting in EEG signal attenuation. In addition, existing pressure regulation devices are prone to generating electromagnetic noise interference signals during operation, and in multi-channel acquisition scenarios, the imbalance of interface impedance between channels can cause common-mode interference, reducing signal acquisition quality.

[0006] To address the above problems, the present invention provides the following technical solution:

[0007] The first aspect of this invention provides a dry EEG electrode structure that is free of conductive gel, comprising:

[0008] Wearing support structure; micro actuator, disposed on one side of the wearing support structure;

[0009] A pressure-equalizing backing is disposed on the side of the microactuator away from the wearing support structure;

[0010] An electrode substrate is disposed on the side of the equalizing backing away from the micro actuator;

[0011] A microtendril array is disposed on the side of the electrode substrate away from the equalizing backing. The microtendril array includes microtendrils and micro / nano structures attached to the outer surface of the microtendrils.

[0012] The impedance sensing unit includes an excitation connection terminal, a sensing connection terminal, and a return electrode;

[0013] The signal matching unit includes a matching network, a control unit, a preamplifier, and a common-mode drive circuit.

[0014] Common-mode drive electrode;

[0015] The impedance sensing unit and the signal matching unit are respectively disposed on the electrode substrate;

[0016] The excitation connection terminal and the sensing connection terminal are respectively electrically connected to the micro-tendon;

[0017] The micro-touch is electrically connected to the input terminal of the matching network, and the output terminal of the matching network is electrically connected to the input terminal of the preamplifier.

[0018] The control unit is electrically connected to the impedance sensing unit, the micro actuator, the matching network, and the common-mode drive circuit, respectively.

[0019] The common-mode driving circuit is electrically connected to the common-mode driving electrode.

[0020] The first aspect of the present invention achieves dynamic adjustment of contact pressure by setting a micro-actuator between the electrode substrate and the wearing support structure, and combining it with an impedance sensing unit and a control unit.

[0021] The impedance sensing unit acquires scalp contact impedance data, and the control unit drives the micro-actuator to generate axial displacement based on this data, thereby adjusting the contact pressure between the micro-tendon array and the scalp.

[0022] Meanwhile, the signal matching unit adjusts the circuit parameters according to the contact state to achieve coordinated matching between the mechanical structure and the circuit.

[0023] Preferably, the micro actuator is a power-off self-locking linear actuator, and the power output shaft of the micro actuator is mechanically connected to the pressure equalizing backing.

[0024] The micro-actuator with a power-off self-locking structure disconnects the power supply after reaching the target displacement. It can maintain the current contact pressure by relying on its own mechanical resistance, which reduces the power consumption generated by continuous power supply and reduces the interference of electromagnetic signals on EEG signal acquisition.

[0025] Preferably, the electrode substrate has a first independent conductive path and a second independent conductive path.

[0026] The excitation connection terminal is electrically connected to the microtendon through the first independent conductive path, and the sensing connection terminal is electrically connected to the same microtendon through the second independent conductive path.

[0027] This structure separates the excitation current loop from the voltage sensing loop at the micro-touch end, reducing the impact of the conductor itself and the distributed impedance at the contact point on the measurement link and improving the accuracy of impedance measurement.

[0028] Preferably, the internal circuit of the preamplifier includes an output gate switch and a sample-and-hold circuit; the output gate switch is connected in series in the analog signal output link of the preamplifier, and the sample-and-hold circuit is connected in parallel to the input terminal of the output gate switch;

[0029] The control terminal of the output gate switch is electrically connected to the control unit.

[0030] During actuator operation, the output gate switch blocks the signal output, and the sample-and-hold circuit maintains the level of the last valid cycle before disconnection, keeping the baseline of the signal output link stable and reducing the impact of transient noise on subsequent circuits.

[0031] A second aspect of the present invention provides a scalp impedance adaptive matching method, applied to the above-mentioned conductive gel-free dry EEG electrode structure, comprising the following steps:

[0032] The control unit sends an impedance detection command to the impedance sensing unit, which outputs a dual-frequency detection AC current and simultaneously acquires voltage drop data. The ohmic component and polarization component are then calculated based on the voltage drop data.

[0033] The control unit compares the ohmic component with a calibration trigger threshold.

[0034] When the ohmic component is greater than the calibration trigger threshold and the duration reaches the preset anti-shake time, the control unit generates a blind zone trigger signal;

[0035] The preamplifier receives the dead zone trigger signal, disconnects the analog signal output, and maintains the current output level;

[0036] The control unit outputs a power drive signal to the micro actuator, which pushes the pressure equalization backing, electrode substrate and micro-tendon array to generate axial displacement.

[0037] The control unit compares the ohmic component calculated in real time with the hysteresis exit threshold.

[0038] When the ohmic component is less than or equal to the hysteresis exit threshold, the control unit sets the power drive signal to zero;

[0039] The impedance sensing unit outputs a single-frequency detection AC current to obtain the low-frequency contact impedance amplitude and impedance phase.

[0040] The control unit writes input impedance adaptation parameters to the matching network according to the low-frequency contact impedance amplitude, and writes phase compensation parameters to the matching network according to the impedance phase.

[0041] The control unit cancels the blind zone trigger signal, and the preamplifier closes the analog signal output link.

[0042] The second aspect of the invention combines impedance detection, pressure regulation, and circuit parameter configuration.

[0043] By using the ohmic component as the trigger reference, false judgments caused by polarization capacitance are reduced.

[0044] By setting blind zones, interference during actuator operation is blocked;

[0045] After pressure regulation is completed, the parameters of the matching network are updated, achieving impedance matching in both mechanical and electrical aspects.

[0046] Preferably, the step of calculating the ohmic component and polarization component based on the voltage drop data includes:

[0047] Extract the voltage drop data at two angular frequencies and calculate the total amplitude of the scalp contact impedance at the corresponding angular frequencies;

[0048] Based on the algebraic relationship that the square of the total amplitude of scalp contact impedance is equal to the sum of the squares of the ohmic component and the squares of the polarization component, a system of two simultaneous equations is constructed.

[0049] Solve the system of two simultaneous equations to separate the values ​​of the ohmic component and the polarization component.

[0050] This step calculates the ohmic component using dual-frequency data, eliminating the influence of polarization effects on impedance assessment during single-frequency detection and improving the accuracy of contact condition judgment.

[0051] Preferably, the preamplifier receives the dead zone trigger signal, disconnects the analog signal output, and maintains the current output level, including:

[0052] The control unit sends a shutdown level to the output gate switch in the preamplifier;

[0053] The control unit sends a hold command to the sample-and-hold circuit within the preamplifier;

[0054] The sample-and-hold circuit locks the EEG signal value of the last sampling cycle before the output gate switch is turned off, and uses it as the output level of the preamplifier.

[0055] This process shields the electrical disturbances at the output during electrode adjustment, ensuring baseline stability of the acquisition system.

[0056] Preferably, the control unit outputs a power drive signal to the micro-actuator, including:

[0057] Calculate the difference between the ohmic component and the hysteresis exit threshold; input the difference into the proportional-integral control model to calculate the drive power value;

[0058] The driving power value is converted into a pulse width modulation signal with a corresponding duty cycle, and output as the power driving signal to the micro actuator.

[0059] This step dynamically adjusts the drive signal based on the impedance difference to keep the micro-actuator's propulsion force stable and avoid excessive local pressure.

[0060] Preferably, the method further includes:

[0061] The low-frequency contact impedance amplitude measured by the impedance sensing unit in multiple different dry EEG electrode structures was obtained.

[0062] Calculate the maximum difference among the aforementioned low-frequency contact impedance amplitudes;

[0063] Multiplying the maximum difference by a preset scaling factor yields the inverse compensation gain.

[0064] When the inverting compensation gain is less than the gain limiting threshold, the inverting compensation gain is written into the common-mode drive circuit;

[0065] When the inverting compensation gain is greater than or equal to the gain limiting threshold, the gain limiting threshold is written into the common-mode drive circuit.

[0066] This step adjusts the gain of the common-mode drive circuit based on the impedance difference between different channels, thereby improving the common-mode rejection effect during multi-channel acquisition.

[0067] Preferably, after the preamplifier closes the analog signal output link, the method further includes: starting an internal timer to perform timing;

[0068] The current time value of the internal timer is compared with the preset polling period;

[0069] When the current timing value equals the preset polling period, the internal timer is cleared and the impedance sensing unit is controlled to output the dual-frequency detection AC power to start the next calculation of the ohmic component and polarization component.

[0070] This step, through periodic testing, enables the system to periodically check and maintain impedance matching during signal acquisition.

[0071] This invention provides a dry EEG electrode structure that is free of conductive gel and a method for adaptive scalp impedance matching. It has the following beneficial effects:

[0072] 1. This invention, by placing a micro-actuator between the wearing support structure and the pressure-equalizing backing, combined with an impedance sensing unit and a control unit, can dynamically change the contact pressure between the micro-tendon array and the scalp based on the real-time detected ohmic component of the scalp contact impedance. Simultaneously, the system, in conjunction with a signal matching unit, electronically reconstructs the input impedance and phase, achieving coordinated operation of physical structure voltage regulation and circuit parameter matching, thereby maintaining the stability of the EEG signal acquisition link when dealing with individual differences and motion interference.

[0073] 2. The micro-actuator of this invention employs a power-off self-locking linear driver and incorporates an output gate switch and a sample-and-hold circuit within the preamplifier. When the system triggers mechanical adjustment, the sample-and-hold circuit locks the baseline level before disconnection to isolate transient electromechanical noise; after adjustment, the driver power supply is cut off, and the current pressure is maintained by mechanical resistance. This structural design shields electrical disturbances during pressure regulation and eliminates electromagnetic interference and additional power consumption caused by continuous power supply.

[0074] 3. This invention separates the ohmic and polarization components by injecting dual-frequency AC current into the impedance sensing unit, eliminating the interference of polarization effects on impedance assessment and improving the accuracy of contact state judgment. Furthermore, in multi-channel acquisition scenarios, the system extracts the maximum difference in low-frequency contact impedance between channels, adaptively calculates the inverse compensation gain based on this, and writes it into the common-mode drive circuit, improving common-mode interference caused by inter-channel interface impedance imbalance and enhancing the signal-to-noise ratio. Attached Figure Description

[0075] Figure 1 This is a schematic diagram of the system hardware structure according to an embodiment of the present invention;

[0076] Figure 2 This is a schematic diagram of the system workflow according to an embodiment of the present invention;

[0077] Figure 3 This is a schematic diagram of the dual-frequency solution logic for scalp contact impedance according to an embodiment of the present invention;

[0078] Figure 4 This is a timing diagram for blind zone triggering and state switching control in an embodiment of the present invention;

[0079] Figure 5 This is a schematic diagram of the physical layer adaptive voltage regulation and self-locking execution principle in an embodiment of the present invention.

[0080] Figure 6 This is a schematic diagram illustrating the circuit layer dynamic matching and common-mode suppression principle of an embodiment of the present invention.

[0081] Figure 7 This is a flowchart of the time-division multiplexing and holographic closed-loop iterative control according to an embodiment of the present invention;

[0082] Figure 8 This is a timing verification diagram of the contact impedance dynamic tracking and adaptive voltage regulation effect in a specific application embodiment of the present invention.

[0083] Among them, 1. Electrode substrate; 2. Micro-tentacle array; 3. Equalizing backing; 4. Impedance sensing unit; 5. Micro-actuator; 6. Signal matching unit; 7. Wearing support structure; 21. Micro-tentacle; 22. Micro-nano structure; 41. Excitation connection terminal; 42. Sensing connection terminal; 43. Return electrode; 61. Matching network; 62. Control unit; 63. Preamplifier; 64. Common mode drive circuit; 65. Common mode drive electrode. Detailed Implementation

[0084] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0085] Example:

[0086] See attached document Figure 1 , Figure 1 This is a schematic diagram of the system hardware structure according to an embodiment of the present invention.

[0087] This invention provides a brainwave electrode structure, which may include:

[0088] Electrode substrate 1, micro-tweet array 2, pressure equalization backing 3, impedance sensing unit 4, micro-actuator 5, signal matching unit 6, and wearing support structure 7.

[0089] A microfiber array 2 is arranged on the side of the electrode substrate 1 facing the scalp to be tested.

[0090] The microtendril array 2 includes multiple microtendrils 21 extending along a direction perpendicular to the surface of the electrode substrate 1.

[0091] The ends of the micro-tentacles 21 are formed with micro-nano structures 22.

[0092] A pressure equalization backing 3 is provided on the side of the electrode substrate 1 that is away from the scalp to be tested.

[0093] Impedance sensing unit 4 is integrated inside the EEG electrode structure and includes coplanarly arranged excitation connection terminal 41, sensing connection terminal 42, and return electrode 43.

[0094] The excitation connection terminal 41 and the sensing connection terminal 42 are respectively connected to the same conductive bus node of the micro-touch array 2 through independent conductive paths. The excitation connection terminal 41 is connected to the constant current excitation output channel of the impedance sensing unit 4, and the sensing connection terminal 42 is connected to the high input impedance voltage sensing channel, thereby forming a measurement connection in which the current excitation path and the voltage sensing path are separated.

[0095] The return electrode 43 is positioned at another location in contact with the scalp to be tested, to form a closed loop for impedance detection current and to serve as a reference node for impedance sensing voltage.

[0096] The micro actuator 5 is disposed between the wearing support structure 7 and the pressure equalizing backing 3. One end of the micro actuator 5 is axially fixed relative to the wearing support structure 7, and the other end abuts or connects to the pressure equalizing backing 3.

[0097] The pressure equalization backing 3 is disposed between the micro actuator 5 and the electrode substrate 1 and is attached to or connected to the electrode substrate 1.

[0098] The micro actuator 5 adopts a linear drive mechanism with mechanical self-locking characteristics when power is off.

[0099] The micro-actuator 5 receives an electric drive signal and generates a linear displacement in the axial direction, changing the adhesion pressure between the micro-tendon array 2 and the scalp to be tested. After the electric drive signal is cut off, the micro-actuator 5 maintains the current displacement and adhesion pressure state by relying on mechanical resistance.

[0100] The signal matching unit 6 is disposed on a flexible circuit board at a distance of no more than 15mm from the micro-touch array 2.

[0101] The signal matching unit 6 includes a matching network 61, a control unit 62, a preamplifier 63, and a common-mode drive circuit 64.

[0102] The microtentacles 21 are formed of conductive material or have at least a continuous conductive layer. Multiple microtentacles 21 form EEG signal acquisition nodes through a conductive busbar layer disposed on the electrode substrate 1.

[0103] The conductive bus layer is electrically connected to the signal input terminal of the matching network 61, and the signal output terminal of the matching network 61 is electrically connected to the signal input terminal of the preamplifier 63. The preamplifier 63 amplifies the EEG signal acquired by the microfiber array 2 and outputs it to the control unit 62 or the subsequent EEG data acquisition unit through the analog-to-digital conversion channel.

[0104] The output of the impedance sensing unit 4 is connected to the impedance detection signal input interface of the control unit 62, and the output of the preamplifier 63 is connected to the EEG signal input interface of the control unit 62 or the subsequent EEG data acquisition unit through the analog-to-digital conversion channel.

[0105] The signal output interface of the control unit 62 is connected to the control terminal of the micro actuator 5, the parameter configuration terminal of the matching network 61, and the gain configuration terminal of the common mode drive circuit 64, respectively.

[0106] The analog signal input terminal of the common-mode drive circuit 64 is connected to the common-mode signal extraction node of the multi-channel preamplifier, and the output terminal of the common-mode drive circuit 64 is connected to the common-mode drive electrode 65. The common-mode drive electrode 65 is in contact with the wearer's skin and is used to apply the inverted common-mode feedback signal to the human body.

[0107] See attached document Figure 2 , Figure 2 This is a schematic diagram of the system workflow according to an embodiment of the present invention. The present invention provides a scalp impedance adaptive matching method, comprising the following steps:

[0108] S10, Control unit 62 controls impedance sensing unit 4 within a single impedance detection window. Dual-frequency detection AC current is continuously injected into the scalp under test through the excitation connection terminal 41. The sensing connection terminal 42 synchronously acquires the voltage drop data. The control unit 62 calculates the scalp contact impedance based on the voltage drop data and separates the scalp contact impedance into ohmic and polarization components.

[0109] S20, Control unit 62 compares the ohmic component with the calibration trigger threshold. Comparison, when the ohmic component continuously exceeds the calibration trigger threshold Reaching the preset image stabilization time The control unit 62 initiates the calibration blind zone and suspends the EEG signal output of the preamplifier 63;

[0110] S30, within the calibration blind zone, the control unit 62 sends a drive command to the micro-actuator 5. The micro-actuator 5 pushes the equalizing backing 3 and the electrode substrate 1 toward the scalp to be tested, thereby increasing the axial indentation and contact preload of the micro-tendon array 2 relative to the scalp to be tested. The control unit 62 continuously monitors the ohmic component. When the ohmic component value decreases and reaches or falls below the hysteresis exit threshold... At this time, the control unit 62 cuts off the power supply circuit of the micro actuator 5, and the micro actuator 5 enters a passive mechanical self-locking state to maintain the existing bonding pressure;

[0111] S40, the control unit 62 controls the impedance sensing unit 4 to perform low-frequency impedance calibration within the same flow control blind zone, and obtains the low-frequency contact impedance amplitude after physical voltage regulation. and impedance phase ;

[0112] The control unit 62 determines the low-frequency contact impedance amplitude based on the low-frequency contact impedance amplitude. Input impedance matching parameters are written into the matching network 61, and the impedance phase is adjusted accordingly. Configure the phase compensation parameters for matching network 61;

[0113] In the multi-channel EEG acquisition implementation, the control unit 62 further configures the feedback gain of the common-mode drive circuit 64 according to the low-frequency contact impedance difference between different acquisition channels;

[0114] S50, after the parameter reconstruction is completed, the control unit 62 controls the system to exit the calibration blind zone, the preamplifier 63 resumes EEG signal data sampling and output, and repeatedly triggers the above steps according to the set time period to maintain the dynamic electrical matching of the acquisition interface.

[0115] The principles and implementation details of the technical solution of this invention will be explained in detail below, taking into account the specific module structure and control steps.

[0116] See attached document Figure 3 , Figure 3This is a schematic diagram of the dual-frequency solution logic for scalp contact impedance according to an embodiment of the present invention.

[0117] Step S10 provided by the present invention specifically includes the following sub-steps:

[0118] S101, Set the upper limit of the effective frequency band of EEG signals to... The control unit 62 controls the impedance sensing unit 4 to generate ordinary frequencies respectively. and The corresponding angular frequencies are respectively , Dual-frequency sinusoidal alternating current, among which .

[0119] To avoid crosstalk between the alternating current excitation signal and the target EEG signal in the frequency spectrum, the set angular frequency... and All are greater than the angular frequency corresponding to the upper limit of the effective frequency band of the target EEG signal. .

[0120] To ensure detection accuracy and avoid frequency aliasing, ordinary frequencies and Each was set within the range of 1kHz to 10kHz, and and Different values ​​are selected, while maintaining a preset frequency interval greater than the system's frequency resolution capability.

[0121] In one specific implementation, set .

[0122] Impedance sensing unit 4 is connected to excitation connection terminal 41 within the single impedance detection window. The dual-frequency sinusoidal alternating current is continuously injected into the scalp to be tested in the form of microcurrent.

[0123] The detection current injected by the excitation connection terminal 41 is conducted through the scalp tissue and then returned to the power supply of the impedance sensing unit 4 by the return electrode 43, thereby forming a closed AC detection circuit.

[0124] The sensing connection 42 acquires the voltage response at the corresponding detection frequency relative to the return electrode 43. For the DC digital frequency synthesis mechanism that generates dual-frequency sinusoidal alternating current and the constant current source topology that drives the micro-current output, those skilled in the art can combine it with the impedance measurement module inside a conventional physiological signal acquisition front-end chip for hardware configuration. The underlying hardware topology and register configuration are well-known technologies in the field and will not be elaborated upon here.

[0125] S102, the sensing connection terminal 42 synchronously acquires the voltage response signal generated by the scalp interface under AC excitation at different frequencies.

[0126] The analog-to-digital conversion channel inside the impedance sensing unit 4 acquires the voltage response signal and sends it to the control unit 62.

[0127] The known amplitude of the injected microcurrent is The control unit 62 extracts the amplitude data of the voltage response. According to Ohm's law, the angular frequency is calculated. and The corresponding total amplitude of scalp contact impedance is denoted as follows: and The computational relation satisfies .

[0128] S103, the control unit 62 calls the internally stored impedance decomposition algorithm to separate and calculate the total amplitude of the extracted scalp contact impedance.

[0129] In applications of dry electrodes, the measured impedance is usually fluctuating due to factors such as scalp sweat secretion, differences in stratum corneum thickness, and slight movements.

[0130] This invention solves the problem by introducing an equivalent circuit model.

[0131] Under the set high-frequency AC excitation, the charge transfer resistance at the electrode-electrolyte interface is short-circuited by the double-layer polarization capacitor.

[0132] The square of the total amplitude of the scalp contact impedance is equivalent to the sum of the squares of the ohmic component and the polarization component.

[0133] Ohmic components The equivalent ohmic component of the electrode-scalp interface, in the equivalent circuit model and detection frequency range used in this embodiment, the change of this ohmic component mainly characterizes the change of the mechanical contact state between the micro-touch item 21 and the scalp to be tested.

[0134] The polarization components mainly correspond to the double-layer polarization capacitance. Capacitive reactance generated under high-frequency conditions.

[0135] The total amplitude of scalp contact impedance and its components satisfy the following relationship:

[0136] ;

[0137] In the formula, Indicates at a specific angular frequency The total amplitude of the scalp contact impedance measured below, Represents the ohmic component. Indicates double-layer polarized capacitance. This represents the angular frequency of the injected sinusoidal alternating current.

[0138] S104, the control unit 62 obtains the scalp contact impedance amplitude at two synchronously acquired angular frequencies. and Construct a system of two simultaneous equations.

[0139] Through algebraic elimination logic, the control unit 62 calculates the ohmic component independent of the interface polarization effect. :

[0140] ;

[0141] Control unit 62 synchronously calculates the double-layer polarization capacitance characterizing the polarization effect. :

[0142] ;

[0143] To prevent calculation errors caused by front-end sampling noise or momentary electrode detachment, the control unit 62 performs a numerical validity check before performing square root and division operations.

[0144] when , ,or When the current sampling period data does not meet the model solution conditions, the control unit 62 determines that the current data does not meet the model solution conditions and discards the current data or uses the historical effective impedance parameters of the previous sampling period.

[0145] Through the above dual-frequency calculation process, the control unit 62 is able to remove the polarization component that is affected by sweat secretion and interfacial chemical reactions, resulting in low-frequency fluctuations.

[0146] Calculated ohmic components It can substantially reflect the mechanical contact state between the micro-tweezers 21 and the scalp to be tested.

[0147] The control unit 62 writes the calculated ohmic and polarization components into the internal cache register as feedback control variables to trigger the subsequent physical layer adaptive voltage regulation and circuit layer parameter compensation stages.

[0148] See attached document Figure 4 , Figure 4 This is a timing diagram for blind zone triggering and state switching control according to an embodiment of the present invention.

[0149] Step S20 provided by the present invention specifically includes the following sub-steps: S201, the control unit 62 is pre-configured with a calibration trigger threshold. and delayed exit threshold ,in Together, they constitute the hysteresis control interval.

[0150] To prevent the system from frequently entering and exiting the calibration blind zone near the critical impedance due to impedance fluctuations, a hysteresis exit threshold is used. Set to less than the upper limit threshold .

[0151] In practical implementation, for non-invasive scalp EEG acquisition scenarios, The value range can be configured from 5kΩ to 15kΩ.

[0152] The control unit 62 also has an internal anti-shake time window. It is used to filter out impedance spikes caused by instantaneous human movements.

[0153] To prevent the system from getting stuck in an abnormal deadlock, the control unit 62 is also equipped with a maximum blind zone timeout period. This is used to limit the maximum duration for which the system is in the calibration blind zone at any given time.

[0154] S202, Internal maintenance and calibration completion indicator for control unit 62 and fault signs .

[0155] When the ohmic component reaches the hysteresis exit threshold At that time, only the physical voltage regulation action of microactuator 5 is terminated, but the voltage regulation continues to be maintained. This keeps the system in the calibration blind zone and continues to perform the circuit layer parameter reconstruction in step S40;

[0156] Only after parameter reconstruction and hardware setup are completed Set to 1, or set to 1 in case of timeout or hardware failure. Set to 1, then exit the current calibration process.

[0157] The state transition logic is as follows:

[0158] ;

[0159] In the formula, This represents the blind zone state variable at the current moment. This represents the ohmic component calculated at the current moment. Indicates the sampling period.

[0160] S203, when the continuously monitored ohmic component Greater than the upper limit threshold And the duration of this exceeding state meets or exceeds the stabilization time window. At that time, the control unit 62 confirmed that the current increase in impedance was not caused by a short-term micro-motion, but by a substantial contact failure.

[0161] The duration of a single impedance detection window is denoted as . and satisfy This ensures that the control unit 62 can complete the anti-jitter judgment of impedance over-limit state within a series of continuous detection windows.

[0162] At this time, the control unit 62 will change the blind zone state variable. The value is set from 0 to 1, and the system starts calibrating the blind zone.

[0163] If within the stabilization time window When the internal ohmic component falls below the upper limit threshold, the control unit 62 resets the timer, and the blind zone state variable remains at 0.

[0164] The calibration blind zone is essentially a hardware interference window defined in the time dimension. The system uses this window to centrally perform physical voltage regulation and circuit adjustment actions.

[0165] S204, State variables in the blind zone Placed within the calibration blind zone of 1, the control unit 62 sends a control command to the signal matching unit 6 to suspend the EEG signal output of the preamplifier 63.

[0166] The preamplifier 63 is internally equipped with a sample-and-hold circuit and an output gate switch.

[0167] Control unit 62 shuts down the output gate switch, causing preamplifier 63 to pause outputting real-time amplified analog signals to subsequent analog conversion links; control unit 62 synchronously controls the sample-and-hold circuit to lock the output value of the EEG signal to the value of the last valid sampling cycle before entering the calibration blind zone.

[0168] For the transistor-level topology of the sample-and-hold circuit and gate switch inside the preamplifier, those skilled in the art can combine it with the internal architecture of conventional physiological signal amplification chips for hardware design. Its underlying hardware topology and register configuration are well-known technologies in the field and will not be described in detail here.

[0169] This signal suspension mechanism helps to block the path of electromagnetic signals generated by subsequent actions of the micro-actuator 5 along the data link to the next stage, thereby improving the signal-to-noise ratio of the overall acquired data.

[0170] See attached document Figure 5 , Figure 5 This is a schematic diagram of the physical layer adaptive voltage regulation and self-locking execution principle according to an embodiment of the present invention.

[0171] Step S30 provided by the present invention specifically includes the following sub-steps:

[0172] S301, after the control unit 62 sets the blind zone state variable to 1 and suspends the EEG signal output, the drive module inside the control unit 62 generates a power drive signal in pulse width modulation format or analog voltage format.

[0173] The control unit 62 sends the power drive signal to the control terminal of the micro actuator 5.

[0174] The micro actuator 5 receives electrical energy and drives the internal micro stepper motor and self-locking screw and nut pair to move, thereby converting the electrical energy into axial mechanical thrust along the direction perpendicular to the surface of the electrode substrate 1.

[0175] The control unit 62 uses a proportional-integral control strategy to adjust the output drive power, first calculating the impedance error. :

[0176] ;

[0177] The drive power control expression is:

[0178] ;

[0179] In the formula, This indicates that the calculation result will be limited to 0. Within the safety limits. When At that time, the error and drive power Set to zero; when the calculated value reaches zero. The integration term is stopped from accumulating further to avoid integration saturation. Parameters and The specific values ​​can be pre-calibrated by technicians using the Ziegler-Nichols tuning rule or actual testing.

[0180] S302, the axial mechanical thrust generated by the micro actuator 5 acts directly on the equalizing back 3.

[0181] The equalizing back 3 utilizes the elastic material properties of its material to absorb local stress concentration through its own flexible deformation, dispersing the single-point mechanical thrust into a uniform pressure distributed over a surface.

[0182] The uniform pressure is transmitted from the electrode substrate 1 to the micro-touch array 2, and pushes the electrode substrate 1 and the micro-touch array 2 together to move axially toward the scalp to be tested, thereby overcoming the mechanical obstruction caused by local hair to the electrode contact.

[0183] The axial displacement increases the amount of indentation and contact tightness of the micro-tentacle 21 relative to the scalp to be tested, and expands the effective electrical contact area between the micro-nano structure 22 at the end of the micro-tentacle 21 and the stratum corneum of the scalp, thereby reducing the equivalent contact impedance of the electrode-scalp interface.

[0184] S303, as the micro-actuator 5 continues to advance, the control unit 62 polls and calls the dual-frequency calculation logic in step S10 at a set sampling frequency to establish real-time closed-loop monitoring between the physical path and electrical impedance.

[0185] The control unit 62 inverts the latest ohmic component obtained into the drive power control expression in step S301, and dynamically adjusts the propulsion speed and force of the micro actuator 5.

[0186] As the micro-actuator 5 continues to advance, the control unit 62 simultaneously acquires the current axial displacement of the micro-actuator 5. and the preset maximum allowable displacement Compare them.

[0187] Current axial displacement It can be calculated based on the cumulative number of stepper motor drive pulses and the lead screw, or it can be directly detected by the position sensor set on the micro actuator 5.

[0188] when Reaching or exceeding And the ohm weight Still above the delayed exit threshold At that time, the control unit 62 immediately ordered the drive power If the value is zero, the fault flag will be set. Set to 1 and terminate the current calibration process.

[0189] When the ohmic component value is detected to decrease and reach the hysteresis exit threshold When the control unit 62 determines that the physical layer voltage regulation task has been completed, it immediately orders the output drive power to be increased. When the value is zero, the power supply circuit of micro-actuator 5 is cut off.

[0190] If the time that the control unit 62 is in the calibration blind zone reaches the maximum blind zone timeout time. Furthermore, the ohmic component still did not meet the standard, so the control unit 62 forcibly set the output drive power to zero and set the fault flag. Set to 1 and terminate the normal calibration process for this round, and no longer continue to execute the normal parameter reconstruction in step S40;

[0191] The output gate of the preamplifier 63 remains closed, while simultaneously outputting a contact abnormality signal to the host computer or system fault management module, waiting for re-wearing, reset, or the next manual trigger calibration.

[0192] S304, after the power supply circuit is cut off, the micro actuator 5 synchronously enters the passive motor self-locking state. The micro actuator 5 relies on the static friction of the threaded pair in the self-locking screw and nut pair to lock the current axial displacement state under the condition of zero power consumption, maintaining the physical contact pressure established between the pressure equalizing back 3 and the micro-touch array 2 and the scalp.

[0193] In one specific implementation, the micro actuator 5 uses a micro stepper motor to drive a self-locking lead screw and nut pair, and the lead screw adopts a threaded structure with mechanical self-locking capability.

[0194] After the micro stepper motor stops receiving power, the lead screw and nut pair relies on the static friction of the threaded pair to prevent the axial feedback from driving the lead screw to rotate in the opposite direction, thereby maintaining the current axial position of the equalizing back 3 and the electrode substrate 1.

[0195] The passive motor self-locking mechanism enables the system to operate with zero static power consumption during the blocking maintenance phase, preventing the problem of local heat accumulation caused by continuous motor power supply, and avoiding electromagnetic interference from the high-frequency motor drive current to subsequent weak EEG signals.

[0196] S305, when the system is re-biased, restarted, or receives a reset command, the control unit 62 controls the micro-actuator 5 to move in the opposite direction of reducing the contact force to the preset initial position. The initial position The position is determined by a travel limit switch, position sensor, or pre-calibrated step pulse zero position set on the micro actuator 5. After the control unit 62 confirms that the micro actuator 5 has reached the initial position, it sets the current axial displacement. Reset to zero or update to the preset initial displacement value.

[0197] See attached document Figure 6 , Figure 6 This is a schematic diagram of circuit layer dynamic matching and common-mode suppression according to an embodiment of the present invention.

[0198] The following step S401 of the present invention specifically includes the following sub-steps:

[0199] S401, after the micro actuator 5 is powered off and enters a passive mechanical self-locking state and the physical pressure is stable, the control unit 62 controls the impedance sensing unit 4 to perform low-frequency impedance calibration within the same calibration area.

[0200] Control unit 62 utilizes the same AC micro-current generation and voltage acquisition hardware as in step S10, at a preset low-frequency calibration frequency. Alternatively, a known amplitude AC detection microcurrent is injected into the scalp to be tested, either at a frequency set containing multiple low-frequency calibration points or within that frequency set.

[0201] The amplitude of the AC detection microcurrent does not exceed the preset safety current limit. The impedance sensing unit 4 is equipped with a hardware current limiting circuit to limit the maximum detection current flowing through the human body under low-frequency calibration conditions, i.e., to meet the requirements. .

[0202] Since the EEG data output of the preamplifier 63 is suspended at this time, the low-frequency calibration signal will not be used as valid EEG data output.

[0203] The control unit 62 directly determines the contact impedance amplitude at the corresponding calibration frequency based on the voltage amplitude and phase information obtained during low-frequency calibration. and impedance phase This parameter is used as the electrical reference parameter for low-frequency input impedance matching and phase compensation in matching network 61. The calculation relationship satisfies:

[0204] ;

[0205] ;

[0206] In the formula, and Indicates low-frequency calibration frequency (corresponding angular frequency) Voltage amplitude and phase under ) and This indicates the amplitude and phase of the injected current.

[0207] This step aims to obtain the actual electrical reference parameters after the physical interface morphology changes, providing data support for subsequent circuit layer reconstruction.

[0208] S402, the control unit 62, based on the low-frequency contact impedance amplitude actually measured in step S401, Write the input impedance matching parameters into the matching network 61.

[0209] The matching network 61 employs an active feedback circuit with bootstrap following characteristics or a programmable digital impedance array.

[0210] To prevent attenuation of high-impedance biosignals at the acquisition interface, the matching network 61 adjusts its equivalent input impedance. This ensures that it meets the high input impedance constraint relationship relative to the electrode-scalp contact impedance:

[0211] ;

[0212] In the formula, and These represent the channels actually measured in step S401. With acquisition channel Contact impedance value under corresponding low-frequency calibration conditions.

[0213] The control unit 62 extracts the maximum impedance deviation of the entire network and adaptively adjusts the reverse compensation gain of the common-mode drive circuit 64 accordingly. The regulatory mechanism follows the following relationship:

[0214] ;

[0215] In the formula, This represents the base loop gain of the common-mode drive circuit 64. This represents the gain sensitivity coefficient, the value of which can be determined based on the maximum allowable common-mode rejection ratio attenuation range of the system.

[0216] This represents the gain limiting threshold used to prevent the closed-loop system's poles from crossing the imaginary axis, which could lead to high-frequency self-oscillations.

[0217] When the calculated gain exceeds the threshold, the control unit 62 clamps the actual gain parameter to the specified value. This ensures that the common-mode feedback loop has a preset stability margin.

[0218] When the impedance difference between channels increases, the control unit 62 automatically increases the common-mode negative feedback depth according to the above formula, suppressing the environmental power frequency common-mode interference within the set safety margin.

[0219] For the common-mode drive circuit 64, which uses a common-mode feedback reverse amplification topology similar to the right leg drive principle, those skilled in the art can combine it with conventional multi-channel physiological electrophysiological signal acquisition front-end chips for circuit design. The closed-loop resistor network connection method of its internal operational amplifier is a well-known technology in the field and will not be described in detail here.

[0220] See attached document Figure 7 , Figure 7 This is a flowchart of time-division multiplexing and holographic closed-loop iterative control according to an embodiment of the present invention.

[0221] Step S50 provided by the present invention specifically includes the following sub-steps:

[0222] S501, after the parameter reconfiguration command of the matching network 61 and the common mode drive circuit 64 is issued, the hardware setup timer is started inside the control unit 62.

[0223] Waiting for the set hardware setup time Then, the control unit 62 reads the feedback confirmation signal from the internal status register to verify whether the circuit layer parameters have been successfully fixed. This hardware setup time... The value is usually set to 1 millisecond to 5 milliseconds to cover the charge injection transient process caused by the analog switch switching action and the capacitor charging time.

[0224] If the feedback confirmation signal indicates that parameter fixing has failed, the control unit 62 will reissue the reconstruction command within a preset number of retries. Once the register state is confirmed to be correct and the underlying hardware electrical state is stable, the control unit 62 will display a calibration completion flag. Set to 1, and adjust the blind zone state variable according to the state switching logic in step S202. Reset from 1 to 0, and the control system exits the calibration blind zone.

[0225] If the retries exceed the limit and the firmware still fails to solidify successfully, the control unit 62 will display a fault flag. Set to 1 to stop the current calibration process and trigger a system hardware failure interrupt;

[0226] The output gate of preamplifier 63 remains closed until a fault reset or reinitialization is complete.

[0227] S502, accompanying blind zone state variables The value is reset to 0, and the control unit 62 sends a recovery command to the signaling matching unit 6.

[0228] The control unit 62 directs the output gate switch of the preamplifier 63 and simultaneously releases the sample-and-hold circuit inside the preamplifier 63. The preamplifier 63 then resumes real-time analog amplification and data sampling output of the EEG signal.

[0229] Since the micro-actuator 5 is now in a passive mechanical self-locking state and the matching network 61 has completed the static writing of electronic parameters, the EEG data link output by the preamplifier 63 is in a state without physical motor interference and without electrical switch switching, thus ensuring the signal-to-noise ratio of the EEG signal after recovery.

[0230] For the charge punch-through suppression technology of the output gate switch, those skilled in the art can combine it with conventional low-noise analog switches for hardware configuration. The specific selection and wiring layout are well-known technologies in the field and will not be elaborated here.

[0231] S503, Control unit 62 polls according to the set cycle. The impedance detection window in step S10 is triggered cyclically, and the duration of each impedance detection window is [duration missing]. Dual-frequency impedance sampling is continuously performed within this detection window. The control unit 62 uses a time-division multiplexing architecture to alternately plan physical voltage regulation, circuit matching, and EEG data acquisition on the time axis. The triggering logic for the global closed-loop iteration satisfies the following expression:

[0232] ;

[0233] In the formula, This indicates the command status for triggering a new impedance sensing cycle at the current moment. A value of 1 represents the trigger status, and a value of 0 represents maintaining the current acquisition status.

[0234] This indicates the duration during which the system is currently in a normal EEG acquisition state.

[0235] Indicates the preset polling period;

[0236] This indicates a forced calibration trigger flag issued by an external host computer.

[0237] In practical EEG monitoring scenarios, to balance the real-time nature of impedance monitoring with the continuity of data acquisition, the polling cycle... The value range is typically configured to be between 10 seconds and 60 seconds.

[0238] S504, when When the value is determined to be 1, the control unit 62 will continue timing for a certain period of time. Reset to zero and activate for a duration of [duration]. The impedance detection window sends a dual-frequency AC injection command to the impedance sensing unit 4 within the impedance detection window and continuously acquires multiple impedance sampling results.

[0239] The control unit 62 adaptively responds to contact impedance drift caused by wearer micro-movements, scalp sweat evaporation, and changes in environmental humidity through the aforementioned periodic iteration mechanism.

[0240] The control unit 62 dynamically corrects the physical contact pressure and input impedance parameters to maintain long-term dynamic electrical matching and signal fidelity of the EEG acquisition interface.

[0241] See attached document Figure 8 , Figure 8 This is a timing verification diagram of the contact impedance dynamic tracking and adaptive voltage regulation effect according to a specific application embodiment of the present invention.

[0242] The following are specific application examples combining numerical calculations, and in conjunction with the appendix... Figure 8 Experimental verification and effect comparison:

[0243] Specific Application Examples and Numerical Calculation Logic 1. Dual-Frequency Impedance Algorithm Stage In order to monitor the real-time mechanical contact state between the micro-neck array 2 and the multi-scalp, the control unit 62 is configured with dual-frequency detection sinusoidal alternating current at ordinary frequencies of [missing information]. and (corresponding angular frequency) Injected microcurrent amplitude .

[0244] During a certain detection window, due to a slight tilt of the user's head causing the electrodes to loosen, the voltage drop values ​​obtained by the impedance sensing unit 4 at two frequencies were respectively .

[0245] Calculate the total contact resistance magnitude using Ohm's law:

[0246] ;

[0247] Substituting into the ohmic component decomposition formula of this invention:

[0248] ;

[0249] Substitute the values: , .

[0250] ;

[0251] This calculation strips away the polarization component of low-frequency fluctuations, accurately extracting the ohmic component reflecting the current mechanical contact. .

[0252] Physical layer adaptive voltage regulation phase system preset calibration trigger threshold Hysteresis exit threshold Image stabilization time .

[0253] Current Ohm Components .

[0254] After 2 seconds, the control unit 62 confirms that the micro-motion is not instantaneous and triggers the calibration blind zone (the state variable is set to 1).

[0255] The EEG signal output of the preamplifier 63 was immediately suspended.

[0256] When the micro actuator 5 is powered on, it generates axial mechanical thrust to propel the uniform backing 3 downward according to the PID control law.

[0257] As the micro-touch neck is pressed into the scalp, the ohmic component... from Dynamically decreasing to At this time, it was detected The control unit 62 cuts off the power supply to the micro actuator, and the mechanism enters a passive mechanical self-locking state to maintain the existing physical pressure.

[0258] 3. Dynamic matching stage of circuit layer

[0259] After the physical pressure stabilizes, the control unit 62... Injecting 1 at Hz frequency Alternating current was used to measure the low-frequency contact impedance amplitude. k Impedance phase .

[0260] Set matching coefficient The control unit 62 configures the equivalent input impedance of the matching network 61. M

[0261] It then looks up the parameters of the compensation capacitor and resistor in the table to generate the active phase compensation branch. The amount of advance compensation.

[0262] After the parameters are reconstructed, the system exits the calibration blind zone and resumes the acquisition of high-fidelity EEG signals.

[0263] Experimental verification and effect comparison (combined) Figure 8 To verify the effectiveness of the above embodiments, a comparative experiment was conducted under motion artifact interference. The data obtained from the experiment was processed by scientific computing software to generate an appendix. Figure 8 .

[0264] The experiment set up a control group (using a traditional fixed-pressure dry electrode system) and an experimental group (using the adaptive EEG electrode system of this invention), both of which experienced the same motion interference at the same scalp location.

[0265] Appendix Figure 8 Graphical features and data analysis: Appendix Figure 8 The horizontal axis represents the test time (0-60 seconds), and the vertical axis represents the ohmic component impedance value (kΩ).

[0266] During the 20th to 30th second of the test, the subjects performed continuous shaking and chewing motions.

[0267] The control group showed the following (dashed line trajectory in the figure): After the motion interference occurred at the 20th second, the dashed line trajectory fluctuated violently and the impedance soared rapidly, with the peak value once exceeding 45kΩ.

[0268] Even more seriously, after the movement stopped at the 30th second, due to the irreversible physical displacement of the traditional electrodes, the impedance of the dotted line remained permanently at a high resistance state of about 25kΩ and could not recover to the contact baseline on its own, resulting in severe attenuation and distortion of subsequent EEG signals.

[0269] The invention demonstrates (solid line trajectory and gray shaded area in the figure): at 22 seconds, the solid line impedance exceeded the upper limit threshold. And the duration reaches the stabilization time (2 seconds).

[0270] this Figure 8 A gray rectangular shaded background area appeared, indicating that the system had automatically triggered the calibration blind zone.

[0271] Within the blind zone, as the micro-actuator advances in a closed loop, a sharp drop in the solid line impedance can be observed within just 1.5 seconds, rapidly converging to the far-hysteresis exit threshold. the following.

[0272] After exiting the gray blind zone, the micro actuator is powered off and self-locked, and the solid line trajectory remains stably on the optimal contact baseline of about 8kΩ in the subsequent time.

[0273] Verification conclusion: Combined with the appendix Figure 8 The intuitive curve comparison and the aforementioned numerical calculations confirm that the present invention can not only accurately remove polarization interference by relying on dual-frequency solution, but also achieve rapid and closed-loop physical interface self-repair when contact deterioration is caused by motion.

[0274] Compared to traditional solutions, this invention demonstrates strong robustness and interface self-healing ability in the face of environmental changes and motion interference, significantly improving the long-term reliability of wearable EEG acquisition.

[0275] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A dry EEG electrode structure that does not require conductive gel, characterized in that, include: Wearing a support structure (7); A micro actuator (5) is disposed on one side of the wearing support structure (7); A pressure equalizing backing (3) is disposed on the side of the micro-actuator (5) away from the wearing support structure (7); An electrode substrate (1) is disposed on the side of the pressure equalization backing (3) away from the micro actuator (5); A micro-tent array (2) is disposed on the side of the electrode substrate (1) away from the equalizing backing (3). The micro-tent array (2) includes micro-tents (21) and micro / nano structures (22) attached to the outer surface of the micro-tents (21). The impedance sensing unit (4) includes an excitation connection terminal (41), a sensing connection terminal (42), and a return electrode (43). The signal matching unit (6) includes a matching network (61), a control unit (62), a preamplifier (63), and a common-mode drive circuit (64). Common-mode drive electrode (65); The impedance sensing unit (4) and the signal matching unit (6) are respectively disposed on the electrode substrate (1); The excitation connection terminal (41) and the sensing connection terminal (42) are respectively electrically connected to the micro-tweet (21); The micro-tentacle (21) is electrically connected to the input terminal of the matching network (61), and the output terminal of the matching network (61) is electrically connected to the input terminal of the preamplifier (63). The control unit (62) is electrically connected to the impedance sensing unit (4), the micro actuator (5), the matching network (61), and the common mode drive circuit (64), respectively. The common-mode driving circuit (64) is electrically connected to the common-mode driving electrode (65).

2. The dry EEG electrode structure without conductive gel according to claim 1, characterized in that: The micro actuator (5) is a power-off self-locking linear actuator, and the power output shaft of the micro actuator (5) is mechanically connected to the pressure equalization backing (3).

3. The dry EEG electrode structure without conductive gel according to claim 1, characterized in that: The electrode substrate (1) is provided with a first independent conductive path and a second independent conductive path; The excitation connection terminal (41) is electrically connected to the micro-tweet (21) through the first independent conductive path, and the sensing connection terminal (42) is electrically connected to the same micro-tweet (21) through the second independent conductive path.

4. The dry EEG electrode structure without conductive gel according to claim 1, characterized in that: The internal circuit of the preamplifier (63) is equipped with an output gate switch and a sample-and-hold circuit; The output gate switch is connected in series on the analog signal output link of the preamplifier (63), and the sample-and-hold circuit is connected in parallel to the input terminal of the output gate switch; The control terminal of the output gate switch is electrically connected to the control unit (62).

5. A scalp impedance adaptive matching method, applied to the electrode structure of the dry EEG electrode without conductive gel as described in claim 1, characterized in that, Includes the following steps: The control unit (62) sends an impedance detection command to the impedance sensing unit (4), the impedance sensing unit (4) outputs dual-frequency detection AC power, synchronously acquires voltage drop data, and calculates the ohmic component and polarization component based on the voltage drop data; The control unit (62) compares the ohmic component with the calibration trigger threshold; When the ohmic component is greater than the calibration trigger threshold and the duration reaches the preset anti-shake time, the control unit (62) generates a blind zone trigger signal; The preamplifier (63) receives the dead zone trigger signal, disconnects the analog signal output, and maintains the current output level; The control unit (62) outputs a power drive signal to the micro actuator (5), which pushes the pressure equalization backing (3), the electrode substrate (1) and the micro-tendon array (2) to generate axial displacement. The control unit (62) compares the ohmic component calculated in real time with the hysteresis exit threshold; When the ohmic component is less than or equal to the hysteresis exit threshold, the control unit (62) sets the power drive signal to zero; The impedance sensing unit (4) outputs a single-frequency detection AC current to obtain the low-frequency contact impedance amplitude and impedance phase; The control unit (62) writes the input impedance adaptation parameters to the matching network (61) according to the low-frequency contact impedance amplitude, and writes the phase compensation parameters to the matching network (61) according to the impedance phase. The control unit (62) cancels the blind zone trigger signal, and the preamplifier (63) closes the analog signal output link.

6. The scalp impedance adaptive matching method according to claim 5, characterized in that, The calculation of the ohmic component and polarization component based on the voltage drop data includes: Extract the voltage drop data at two angular frequencies and calculate the total amplitude of the scalp contact impedance at the corresponding angular frequencies; Based on the algebraic relationship that the square of the total amplitude of scalp contact impedance is equal to the sum of the squares of the ohmic component and the squares of the polarization component, a system of two simultaneous equations is constructed. Solve the system of two simultaneous equations to separate the values ​​of the ohmic component and the polarization component.

7. The scalp impedance adaptive matching method according to claim 5, characterized in that, The preamplifier (63) receives the dead zone trigger signal, disconnects the analog signal output, and maintains the current output level, including: The control unit (62) sends a shutdown level to the output gate switch in the preamplifier (63); The control unit (62) sends a hold command to the sample-and-hold circuit within the preamplifier (63); The sample-and-hold circuit locks the EEG signal value of the last sampling cycle before the output gate switch is turned off, and uses it as the output level of the preamplifier (63).

8. The scalp impedance adaptive matching method according to claim 5, characterized in that, The control unit (62) outputs a power drive signal to the micro-actuator (5), including: Calculate the difference between the ohmic component and the hysteresis exit threshold; The difference is input into the proportional-integral control model to calculate the drive power value; The driving power value is converted into a pulse width modulation signal with a corresponding duty cycle and output as the power driving signal to the micro actuator (5).

9. The scalp impedance adaptive matching method according to claim 5, characterized in that, The method further includes: The low-frequency contact impedance amplitude measured by the impedance sensing unit (4) in multiple different dry EEG electrode structures was obtained; Calculate the maximum difference among the aforementioned low-frequency contact impedance amplitudes; multiply the maximum difference by a preset scaling factor to obtain the inverse compensation gain; When the inverting compensation gain is less than the gain limiting threshold, the inverting compensation gain is written into the common-mode drive circuit (64). When the inverting compensation gain is greater than or equal to the gain limiting threshold, the gain limiting threshold is written into the common-mode drive circuit (64).

10. The scalp impedance adaptive matching method according to claim 5, characterized in that, After the preamplifier (63) closes the analog signal output link, the method further includes: Start the internal timer to begin timing; The current time value of the internal timer is compared with the preset polling period; When the current timing value is equal to the preset polling period, the internal timer is cleared and the impedance sensing unit (4) is controlled to output the dual-frequency detection AC power to start the next calculation of the ohmic component and polarization component.

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