Oral cavity contact identification and tooth brushing state intelligent switching control method and electric toothbrush

Abstract

The invention relates to the technical field of intelligent personal care electric appliances, and discloses an oral cavity contact recognition and tooth brushing state intelligent switching control method and an electric toothbrush, and the method comprises the following steps: a micro control module controls a motor to drive an output shaft to generate mechanical micro motion, and injects an electric excitation signal to the output shaft; acquiring a real-time mechanical phase of the vibration motor, and performing synchronous demodulation operation on the loop feedback electric signal based on the phase; calculating a mechanical and impedance coupling coefficient according to the result, comparing the mechanical and impedance coupling coefficient with a threshold to judge whether the brush head is in contact with oral biological tissues, and if so, controlling the motor to enter a cleaning working state; the system also dynamically adjusts the decision threshold based on the ambient reference impedance. According to the invention, by utilizing the characteristic of periodic impedance modulation caused by viscoelasticity of biological tissues, false signal interference generated by fluid media such as water flow and foam is effectively shielded, the problem that the prior art is easily triggered by fluid mistakenly to cause accidental starting and splashing of a motor is solved, and oral cavity contact identification and accurate automatic starting and stopping control are realized.

Description

Technical Field

[0001] This invention relates to the field of intelligent personal care electrical appliances, specifically to a method for oral contact recognition and intelligent switching control of brushing status, and an electric toothbrush. Background Technology

[0002] Electric toothbrushes have become increasingly popular due to their efficient cleaning capabilities. Their core function relies on a motor driving the brush head to generate high-frequency vibrations or rotations to clean teeth. However, this high-frequency motion also brings user pain points: when users turn on the motor before placing the brush head in their mouth, or when removing the brush head from their mouth during brushing, toothpaste foam and water droplets adhering to the brush head are easily splashed due to the high-frequency vibrations. This not only stains clothes and the sink but also reduces the user experience. Therefore, intelligent functions that can automatically detect whether the brush head is in the mouth and control the motor's start and stop accordingly have become an important direction for the development of electric toothbrushes.

[0003] Existing automatic contact detection technologies are typically based on impedance detection or capacitive sensing principles. These solutions utilize the human body as part of a conductive circuit, determining contact by detecting changes in impedance or capacitance between the output shaft and the handle reference ground. However, the oral care environment is complex; water, saliva, and toothpaste foam mixed with saliva are all good conductors. Traditional detection technologies rely primarily on single electrical parameter thresholds, making it difficult to physically distinguish between brush head contact with oral tissue and brush head being rinsed by water or enveloped in foam. When users rinse the brush head under a tap, the conductive path created by the water flow often falsely triggers the sensor, causing the motor to start unexpectedly and splash water. Furthermore, simple pressure sensor solutions cannot distinguish between brushing pressure and accidental pressure during handling, and are often unable to detect the initial state of slight bristle contact with teeth. Existing detection methods struggle to strike a balance between sensitivity and interference resistance, failing to effectively shield against false detections caused by fluid media while ensuring rapid response. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a method for oral contact recognition and intelligent switching control of brushing states, as well as an electric toothbrush. This solves the problem that existing contact detection technologies are unable to effectively distinguish between oral biological tissues and fluid media such as water flow and toothpaste foam, which leads to the electric toothbrush accidentally starting and splashing due to misjudgment during rinsing or non-brushing states.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] The first aspect of this invention provides a method for oral cavity contact recognition and intelligent switching control of brushing state, applied to an electric toothbrush, the electric toothbrush including a handle body, an output shaft, and a brush head assembly. The method includes: a microcontroller module controlling a motor drive and feedback module to drive the output shaft to generate mechanical micro-motion; simultaneously, a control signal injection and acquisition module injects an electrical excitation signal into the output shaft. During this process, the motor drive and feedback module acquires the real-time mechanical phase of the vibrating motor and acquires the loop feedback electrical signal.

[0007] Based on the real-time mechanical phase, the feedback electrical signal is synchronously demodulated to extract signal components containing the mechanical response characteristics of the contact interface. Subsequently, the mechanical and impedance coupling coefficient is calculated based on the synchronous demodulation results. This coefficient is then compared with a preset threshold to determine whether the brush head assembly connected to the output shaft is in contact with oral tissue. If the determination indicates contact with oral tissue, the microcontroller module controls the vibration motor to enter the cleaning operation state.

[0008] In one specific implementation, to achieve high-frequency signal transmission between the rotating or vibrating component and the stationary circuit, the output shaft is connected to the signal injection and acquisition module via a non-contact capacitive coupling structure. Specifically, a moving metal plate is connected to the bottom of the output shaft, and a stationary metal plate is fixed at a corresponding position inside the handle body. A high-dielectric-constant insulating medium is filled between the two to form a coupling capacitor. The carrier frequency of the electrical excitation signal is configured such that the capacitive reactance of this coupling capacitor is less than the equivalent impedance of the human body circuit, thereby ensuring that the excitation signal can be effectively coupled to the output shaft.

[0009] To address the inertial lag problem in mechanical systems, the step of acquiring the real-time mechanical phase of the vibratory motor employs a physical feedback-based detection method. Specifically, this involves acquiring the back electromotive force voltage signal across the windings of the vibratory motor, performing zero-crossing detection on this signal to identify the zero-crossing moment, and reconstructing a continuous phase signal characterizing the real-time physical position of the rotor based on consecutive zero-crossing moments. This continuous phase signal serves as the reference for subsequent demodulation operations, eliminating the phase difference between the drive signal and the actual vibration.

[0010] To extract the weak impedance modulation signal from noise interference, the synchronous demodulation operation step employs orthogonal demodulation technology. First, the feedback signal is bandpass filtered and envelope detected to obtain a low-frequency envelope signal reflecting the instantaneous impedance change. Simultaneously, the system generates an orthogonal reference signal that is in phase-locked and at the same frequency as the mechanical micro-motion frequency. By performing correlation calculations between the low-frequency envelope signal and the orthogonal reference signal, the in-phase and quadrature components of the low-frequency envelope signal at the reference frequency are extracted.

[0011] Based on the aforementioned components, the step of calculating the mechanical and impedance coupling coefficient further includes calculating the composite vector magnitude of the in-phase component and the quadrature component, and defining this composite vector magnitude as the mechanical and impedance coupling coefficient. This coefficient characterizes the strength of the contact impedance modulated by mechanical micro-motion. In the judgment logic, when the mechanical and impedance coupling coefficient is greater than a preset judgment threshold, it indicates that the biological tissue impedance that changes synchronously with the motor vibration has been detected, thereby confirming effective oral contact.

[0012] Considering the influence of the usage environment on the measurement, this invention also includes an environmental reference impedance calibration mechanism. When the handle body is placed on the charging base or in an unloaded state, the system scans and records the environmental reference impedance. The preset judgment threshold is generated based on the environmental reference impedance mapping, realizing dynamic adjustment of the threshold: the judgment threshold is increased when the environmental reference impedance decreases, and decreased when the environmental reference impedance increases, to adapt to different humidity or medium conditions.

[0013] Furthermore, this method can also employ a multi-frequency detection strategy. The vibration motor is controlled to perform linear frequency sweeping or discrete frequency hopping within a preset frequency range, and the corresponding mechanical and impedance coupling coefficient is calculated at each frequency point. By analyzing the rate of change of this coefficient with frequency, it is verified whether it conforms to the viscoelastic frequency response characteristics of biological tissues, further improving the accuracy of identification.

[0014] A second aspect of the present invention provides an electric toothbrush configured to perform the aforementioned oral contact recognition and intelligent switching control method for brushing states. The electric toothbrush includes a handle body, an output shaft disposed at the top of the handle body, and a circuit reference electrode disposed inside the handle body at the negative terminal of the battery or in the grip area. The handle body also houses a microcontroller module, a motor drive and feedback module, and a signal injection and acquisition module. The output shaft is configured as a first detection electrode. The microcontroller module is connected to the motor drive and feedback module and the signal injection and acquisition module, respectively, and is configured to perform the synchronous demodulation operation and contact determination logic.

[0015] Regarding hardware circuit optimization, the electric toothbrush also includes an auxiliary circuit calibration unit connected in parallel between the circuit reference electrode and system ground, which includes an adjustable gain amplifier. The microcontroller module is configured to monitor the base circuit current in real time. When the detected current is lower than a preset safety baseline, it automatically increases the gain of the adjustable gain amplifier or reduces the output impedance of the signal injection and acquisition module to adapt to high-impedance contact conditions such as dry skin.

[0016] Furthermore, the electric toothbrush also integrates an inertial measurement module, which, together with the microcontroller module, enables multi-level state switching control: when the system is in a dormant state and detects that the acceleration exceeds the wake-up threshold, it enters a wake-up pre-detection state, and activates the signal injection and acquisition module to monitor the complex impedance modulus; when the complex impedance modulus changes relative to the environmental reference impedance, it enters a micro-motion lock verification state, initiates mechanical micro-motion, and performs synchronous demodulation calculation; when the algorithm determines that it is in contact with oral biological tissue, it enters a cleaning working state, controls the vibration motor to accelerate to the cleaning working frequency, and achieves a seamless switch from detection to operation.

[0017] This invention provides a method for oral contact recognition and intelligent switching control of brushing status, as well as an electric toothbrush. It has the following beneficial effects:

[0018] 1. This invention generates mechanical micro-motion by controlling the output shaft and injecting an electrical excitation signal. It extracts the impedance modulation component with the same frequency as the mechanical vibration by using synchronous demodulation operation based on real-time mechanical phase. It utilizes the physical characteristic that the viscoelasticity of biological tissue causes the contact impedance to change periodically with mechanical pressure. Since fluid media such as water do not have this modulation feature, it effectively shields the false signal interference generated by water rinsing or toothpaste foam. It solves the technical problem that existing capacitive or resistive sensors are easily triggered by fluids and realizes accurate identification of the brush head contacting oral biological tissue.

[0019] 2. The present invention adopts a non-contact capacitive coupling structure on the signal injection path of the output shaft. The high-frequency coupling capacitor formed by the moving and stationary metal plates realizes signal transmission. This structure avoids the use of physical contact brushes or conductive slip rings on the high-speed vibrating or rotating output shaft, eliminates the life bottleneck caused by mechanical wear and electrical contact noise, and maintains the high-level sealing and waterproof performance and mechanical transmission reliability of the entire electric toothbrush while ensuring stable injection of high-frequency excitation signals.

[0020] 3. This invention establishes a control logic that includes environmental reference impedance calibration and multi-level state switching. It can dynamically adjust the judgment threshold and gain according to changes in environmental humidity and loop impedance. The system only starts micro-motion locking verification after inertial wake-up and impedance change, and maintains low power consumption or micro-motion detection state during non-biological contact. This design not only solves the problem of detection sensitivity drift caused by dry user hands or humid environment, but also reduces the standby power consumption of the system and improves the robustness and battery life of the device in different usage scenarios. Attached Figure Description

[0021] Figure 1 This is a perspective view of the electric toothbrush of the present invention;

[0022] Figure 2 This is a schematic diagram of the internal structure of the electric toothbrush of the present invention;

[0023] Figure 3 This is a block diagram of the hardware architecture of the control system of the present invention;

[0024] Figure 4 This is a schematic diagram of the core detection principle and signal processing model of the present invention;

[0025] Figure 5 This is a flowchart of the synchronous demodulation algorithm based on mechanical carrier modulation of the present invention;

[0026] Figure 6 This is a flowchart of the intelligent identification and state switching control of the present invention.

[0027] The components include: 1. Charging base; 2. Handle body; 3. Output shaft; 4. Brush head assembly; 5. Display assembly; 6. Button assembly; 100. Microcontroller module; 200. Signal injection and acquisition module; 500. Motor drive and feedback module; 700. Inertial measurement module; 800. Charging interface. Detailed Implementation

[0028] The technical solutions in 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.

[0029] See attached document Figure 1 - Appendix Figure 3 This invention provides an oral cavity contact recognition and brushing state switching control system, which is applied to, for example... Figure 1 and Figure 2 The electric toothbrush shown.

[0030] like Figure 1 and Figure 2 As shown, the physical structure of the electric toothbrush includes: a charging base 1, configured to provide power supply and serve as an external reference for environmental reference impedance calibration; a handle body 2, which has an internal cavity for housing the battery, main control circuit board, and power transmission components; the outer shell of the handle body 2 is made of insulating material, or its metal body directly serves as a circuit reference electrode; an output shaft 3, located at the top of the handle body 2, is made of conductive metal material, one end of which is mechanically coupled to an internal vibration motor, and the other end is configured to mount a brush head assembly 4; in this invention, the output shaft 3 is reused as a first detection electrode for injecting an electrical excitation signal to the outside; a display component 5 and a button component 6 are located on the surface of the handle body 2 for user interaction and status display.

[0031] Combined with appendix Figure 3The hardware architecture shown, specifically the circuit system integrated inside the main body 2 of the handle, includes:

[0032] The microcontroller module 100 is installed on the main control circuit board inside the handle body 2, serving as the processing core of the system. The microcontroller module 100 is configured to perform digital signal processing, logic decision-making, and scheduling control of each sub-module, and it has a digital-to-analog conversion interface, an analog-to-digital conversion interface, and a general-purpose input / output interface.

[0033] The signal injection and acquisition module 200 is electrically connected to the microcontroller module 100 and such Figure 2 The output shaft 3 is shown. The signal injection and acquisition module 200 is configured to apply an electrical excitation signal to the output shaft 3 and acquire the feedback electrical signal in the circuit. Specifically, the output shaft 3 is electrically isolated from other grounding points in the handle body 2 through an internal insulated bearing structure, and is connected to the signal output terminal of the signal injection and acquisition module 200 only through a conductive slip ring, brush, or non-contact capacitive coupling structure.

[0034] Specifically, in the non-contact capacitive coupling implementation, a moving metal plate is connected to the bottom of the output shaft 3, and a stationary metal plate is fixed at a corresponding position inside the handle body 2. The space between the two is filled with insulating grease or a polytetrafluoroethylene film with a high dielectric constant, forming a coupling capacitor. The carrier frequency generated by the signal injection and acquisition module 200... The coupling capacitor is configured such that its capacitive reactance is much smaller than the equivalent impedance of the human body circuit (e.g., less than 100 ohms), thus acting as an AC short circuit and ensuring that the high-frequency excitation signal can be coupled to the vibrating output shaft 3 without loss. When the brush head assembly 4 comes into contact with the external medium, the current signal is transmitted to the contact interface via the output shaft 3.

[0035] The motor drive and feedback module 500 is electrically connected to the microcontroller module 100 and a vibration motor housed inside the handle body 2. The vibration motor is mechanically connected to the output shaft 3. The motor drive and feedback module 500 is configured to drive the vibration motor to generate mechanical vibration of the output shaft 3, and to detect the back electromotive force signal or Hall signal of the vibration motor to obtain the real-time mechanical phase of the output shaft 3.

[0036] The inertial measurement module 700 is electrically connected to the microcontroller module 100 and is configured to detect the spatial attitude and acceleration data of the handle body 2 for system wake-up and auxiliary motion recognition.

[0037] The charging interface 800 is located at the bottom of the handle body 2. When the handle body 2 is placed on the charging base 1, the microcontroller module 100 identifies the charging connection status through the charging interface 800 and initiates a parasitic parameter scanning process for the charging base 1 to establish an environmental reference impedance model.

[0038] The loop reference electrode 400 is formed by either the negative ground plane of the battery inside the handle body 2 or a capacitive sensing plate located in the handle grip area. When the user holds the handle body 2, the loop reference electrode 400 forms an electrical circuit with the output shaft 3 through the human body. Furthermore, to address situations where the user's gloves or extremely dry hands cause excessive loop impedance, the system also includes an auxiliary loop calibration unit. This unit, connected in parallel between the loop reference electrode 400 and system ground, contains an adjustable gain amplifier. When the microcontroller module 100 detects that the base loop current is lower than a preset safety baseline, it automatically increases the gain of the adjustable gain amplifier or decreases the output impedance of the excitation generation unit 201 to dynamically match the current contact impedance between the human body and the handle, ensuring the dynamic range of signal acquisition.

[0039] The microcontroller module 100 is connected to the signal injection and acquisition module 200, the motor drive and feedback module 500, and the inertial measurement module 700 via a signal bus. The microcontroller module 100 is configured to control the motor drive and feedback module 500 to drive the output shaft 3 to generate a frequency of... The mechanical micro-motion; the control signal injection and acquisition module 200 injects a carrier frequency of 200 into the output shaft 3. The electric carrier wave; based on the real-time mechanical phase feedback from the motor drive and feedback module 500, the feedback signal collected by the signal injection and acquisition module 200 is synchronously demodulated; based on the calculation result, it is determined whether the brush head assembly 4 connected to the output shaft 3 is in contact with oral biological tissue.

[0040] See attached document Figure 4 This invention constructs a detection model to distinguish between fluid media and biological tissue media based on the physical coupling mechanism of electrochemical impedance spectroscopy characteristics and mechanical response characteristics. This detection model measures the impedance changes at the contact interface. Considered as a modulation function of the electrical excitation signal, mechanical vibration... It is considered as a modulation source of contact impedance.

[0041] In this model, the impedance change at the contact interface Due to the volume impedance of the medium itself With contact resistance Series configuration. When the contact medium is a Newtonian fluid or a non-Newtonian fluid such as water or toothpaste foam, the contact area between the output shaft electrode 3 and the fluid is increased due to the fluid's fluidity and wettability on the surface of the object. and contact pressure The periodic change is not influenced by the minute mechanical vibration of the output shaft's three electrodes, or the change is extremely small and exhibits random phase lag. In this case, the equivalent impedance of the contact interface... It manifests as a DC component superimposed with broadband random noise, i.e. ,in Static impedance This represents the noise component.

[0042] When the contact medium is biological tissue with a fixed shape and elastic modulus, such as teeth or gums, a non-ideal electrical contact is formed between the output shaft electrode 3 and the biological tissue. When the output shaft electrode 3 contacts the biological tissue, due to the viscoelasticity of the tissue, the microscopic contact area and contact tightness at the contact interface will periodically change with the mechanical fretting. This change in physical contact state directly leads to the generation of contact impedance (including contact resistance and contact capacitance) that varies with the frequency of the mechanical fretting. The contact resistance exhibits periodic modulation at the same frequency. In contrast, fluid media, due to their fluidity, can rapidly fill the contact gap, and their contact resistance does not fluctuate periodically with slight vibrations. Based on this, the equivalent impedance of the contact interface... It can be considered as a time-varying signal, which contains a relatively stable static component and a component that varies with time according to the mechanical micro-motion frequency. A changing dynamic modulation component. For example, in a mathematical model, this dynamic modulation component can be represented as having an amplitude of The mechanical micro-motion frequency is The cosine or sine function, and there is a specific impedance phase difference between it and the mechanical vibration. .

[0043] The signal processing model is configured to extract the impedance modulation amplitude from the total feedback signal. The microcontroller module 100 generates a signal including the carrier frequency. A high-frequency electrical signal (such as a sine wave, square wave, or pulse wave) is injected into the circuit as a carrier wave. The feedback electrical signal (voltage or current) is essentially the result of the carrier signal being modulated by the contact impedance. For biological tissue media, due to the periodic fluctuations in impedance, the feedback signal exhibits amplitude modulation characteristics, and its spectrum includes the carrier frequency. In addition to the carrier frequency component, a frequency of is also derived. The sideband components.

[0044] The signal processing model includes an envelope extraction stage and a synchronous demodulation stage. The envelope extraction stage includes a bandpass filter and a detector, configured to filter out power frequency interference and high-frequency noise, and extracts... The signal frequency band centered on the impedance is demodulated to extract the low-frequency envelope signal reflecting impedance changes. For biological tissues, The included frequency is The alternating component; for fluids, It contains only DC components or non-co-frequency noise.

[0045] The synchronous demodulation stage utilizes digital phase-locked loop technology, introducing a frequency synchronized with the mechanical micro-motion frequency. Strictly synchronous and phase-locked reference signal Reference signal This is based on the real-time physical position generation of the motor rotor, rather than on motor drive commands, to compensate for the inertial lag of the mechanical system. The signal processing model will process the low-frequency envelope signal. With reference signal Integral operations, integration time for Integer multiples of.

[0046] Calculation result Characterized the low-frequency envelope signal Reference mechanical micro-motion frequency The projected component on. When When the resistance exceeds a preset threshold, it indicates that the contact impedance has undergone synchronous modulation with the motor vibration, and the system determines that biological tissue with elastic modulus has been detected; when When the impedance is below a preset threshold, the system determines that no effective coupling medium has been identified. This model achieves joint identification of the mechanical and electrical properties of the medium by detecting physical modulation effects rather than simply impedance amplitude.

[0047] See attached document Figure 5 The algorithm is executed by the firmware program inside the microcontroller module 100 and is designed to quantify the degree of response of the contact interface to mechanical micro-vibrations.

[0048] After entering the micro-motion detection mode, the microcontroller module 100 first executes the mechanical carrier generation step. The microcontroller module 100 configures the motor drive unit to output a specifically coded pulse width modulation sequence, driving the vibration motor to generate a mechanical micro-motion frequency of... The reciprocating micro-motion. Mechanical micro-motion frequency. The frequency point is preferably set to a non-power frequency or its harmonics, such as any value in the range of 110Hz to 140Hz, to avoid power grid interference. At the same time, the microcontroller module 100 limits the duty cycle of the pulse width modulation sequence to a low power range of 5% to 15%, so that the mechanical vibration amplitude generated by the output shaft 3 is controlled within a range that is barely perceptible to human touch and cannot shake off the attached water droplets.

[0049] The specific pulse width modulation control strategy employs sparse pulse modulation technology. The microcontroller module 100 does not output a continuous pulse width modulation waveform, but rather outputs a waveform at intervals of... Each carrier cycle outputs a short pulse sequence, or a driving waveform is generated using sinusoidal pulse width modulation. The energy spectral density of this driving waveform is mainly concentrated in... The energy components in the high-frequency hearing range are suppressed, thus achieving a silent micro-vibration effect. This micro-vibration not only serves as a source of detection signals but also avoids generating noise or splashing when not in operation.

[0050] Subsequently, the algorithm performs a real-time mechanical phase acquisition step. Due to the rotational inertia of the vibratory motor rotor and the mechanical damping of the output shaft assembly 3, its actual vibration phase... It lags behind the phase of the drive signal. To obtain an accurate demodulation reference, the microcontroller module 100 acquires the back electromotive force voltage signal across the motor windings at high speed via an analog-to-digital converter interface. The algorithm for Zero-crossing detection is performed to identify the moment when the back electromotive force changes from negative to positive or from positive to negative. Based on continuous zero-crossing moments, the algorithm reconstructs a continuous phase signal characterizing the real-time physical position of the rotor using interpolation or a phase-locked loop. Continuous phase signal It is an angle value that increases linearly with time, and its period strictly corresponds to the mechanical rotation period of the motor rotor.

[0051] Next, the algorithm executes the synchronous phase-sensitive detection step. The microcontroller module 100 synchronously acquires the feedback voltage signal injected into and output by the acquisition module 200, and performs digital bandpass filtering and envelope detection on it to obtain a low-frequency envelope signal reflecting the instantaneous impedance change. .

[0052] Algorithm generation and mechanical micro-motion frequency A reference signal with the same frequency and phase locked. Preferably, in order to eliminate the influence of phase uncertainty, the algorithm generates a pair of orthogonal reference signals (i.e., a sine and a cosine reference with a phase difference of 90 degrees).

[0053] Subsequently, the algorithm processed the low-frequency envelope signal. Perform quadrature demodulation. Specifically, demodulate the low-frequency envelope signal. Correlation operations (e.g., product followed by integration, or product followed by low-pass filtering) are performed with the in-phase reference signal and the quadrature reference signal respectively to extract the envelope signal at the reference mechanical micro-motion frequency. In-phase components and orthogonal components These two components characterize the signal energy in the feedback signal that is strictly synchronized with the mechanical vibration.

[0054] Finally, the algorithm is based on in-phase components. and orthogonal components Calculate the magnitude of the composite vector and define it as the mechanical-impedance coupling coefficient. (For example, calculating using the Pythagorean theorem) This coupling coefficient directly reflects the intensity of the contact impedance modulated by mechanical vibration, and is unaffected by the inherent phase difference between mechanical vibration and impedance change.

[0055] This calculation process eliminates the phase difference between mechanical and electrical reactance. The influence of this ensures consistent detection under different contact angles and pressures. It's worth noting that the system performs a phase scan during factory calibration or each power-on self-test to determine the optimal demodulation phase offset. The microcontroller module 100 controls the motor to operate at a mechanical micro-motion frequency under no-load conditions. Vibration was observed, and the inherent system delay between the back EMF signal and the current noise floor was recorded. In subsequent synchronous demodulation operations, the real-time mechanical continuous phase signal... A calibration phase will be added beforehand. This aligns the timelines of the mechanical system and the electronic acquisition system, eliminating demodulation errors caused by hardware group delays. The microcontroller module 100 will calculate the... Compared with the preset biological tissue determination threshold Compare them.

[0056] Determination threshold It is not a fixed constant, but rather based on the environmental reference impedance. Dynamic variables generated by linear or nonlinear mappings. When detected... When the humidity is low (e.g., in high ambient humidity or when using toothpaste containing salt), the system automatically adjusts the humidity level higher. To suppress spurious coupling components generated by high conductivity fluids; when detected When the temperature is high (e.g., when using pure water or when the user's skin is dry), the system automatically lowers the temperature. This is to improve sensitivity to weak bioimpedance modulation signals. If the duration exceeds the preset anti-shake window time (e.g., 50ms), it is determined that the biological tissue impedance that changes synchronously with the motor vibration has been detected, and it is confirmed as a valid oral contact event; otherwise, it is determined as invalid contact or fluid interference.

[0057] In a preferred embodiment, the algorithm further includes a frequency sweep detection mechanism. The microcontroller module 100 controls the vibration motor to perform linear frequency sweep or discrete frequency hopping within a preset frequency range (e.g., 80Hz to 150Hz), and calculates the corresponding mechanical and impedance coupling coefficients at each frequency point. Algorithm Analysis If the rate of change with frequency matches the viscoelastic frequency response characteristic curve of biological tissue, the effectiveness of the contact is further confirmed. This mechanism utilizes the rheological properties of the dynamic modulus of biological soft tissue changing with frequency, further enhancing the ability to distinguish non-biological simulated materials (such as wet sponges or rubber).

[0058] See attached document Figure 6 This process describes the complete control logic of an electric toothbrush from sleep state to working state and then to shutdown state.

[0059] In step S401, the system enters a low-power sleep state. The microcontroller module 100 shuts down all peripheral clocks except for the inertial measurement module 700 and the charging interface 800. When the charging interface 800 detects an external power supply connection, the system enters the reference calibration sub-process. In this sub-process, the microcontroller module 100 periodically activates the signal injection and acquisition module 200, scanning and recording the current environmental reference impedance when the output shaft 3 is unloaded or connected to the charging dock. And environmental capacitance parameters. These parameters are stored in non-volatile memory and used to update the differential reference in subsequent measurements to compensate for measurement zero drift caused by changes in ambient temperature, humidity, or component aging.

[0060] In step S402, when the inertial measurement module 700 detects that the acceleration or angular velocity of the handle exceeds a preset wake-up threshold (e.g., the change in acceleration is greater than 0.2g), the system exits sleep mode and enters the wake-up pre-probe state. The microcontroller module 100 activates the signal injection and acquisition module 200, injects a high-frequency probe current into the output shaft 3, and monitors the complex impedance modulus of the circuit at a low sampling rate. During this stage, the vibratory motor remains stationary. If the measured complex impedance modulus... relative to environmental reference impedance A change occurs (usually manifested as a decrease in impedance modulus, or an absolute value of the impedance change exceeding a preset threshold), indicating that the output shaft 3 electrode has changed from an open circuit state to contact with a conductive medium (such as water, skin, or oral tissue), and the system then triggers a micro-motion lock verification state.

[0061] In step S403, the system executes the synchronous demodulation algorithm of Embodiment 3. The microcontroller module 100 controls the vibration motor to detect the mechanical micro-motion frequency. The system generates minute vibrations and initiates high-speed sampling and digital phase-locked loop (PLL) calculations. The system then calculates the mechanical and impedance coupling coefficients in real time. If the calculated If the temperature remains below the biological tissue detection threshold, the system determines that the current contact is due to water rinsing or accidental hand contact, maintains the motor in micro-motion mode or stops the motor, and returns to step S402 to continue monitoring; if If the temperature remains above the biological tissue detection threshold, the system determines that the brush head has effectively contacted the teeth or gums in the mouth, and then proceeds to step S404.

[0062] In step S404, the system enters the cleaning operation state. The microcontroller module 100 controls the vibration motor to detect the micro-motion frequency of the mechanical micro-motion sensor. The system smoothly accelerates to the user-preset cleaning frequency (e.g., 250Hz to 300Hz) and increases the drive duty cycle to output rated torque. During cleaning, the microcontroller module 100 no longer performs complete synchronous demodulation (due to the large vibration amplitude at the operating frequency, weak signal detection is unnecessary), but it continues to monitor the DC impedance amplitude of the circuit and the waveform characteristics of the motor drive current. The system estimates the load torque by analyzing the higher harmonic components in the motor current, serving as auxiliary contact status feedback.

[0063] In step S405, the system executes the off-circuit determination logic. When it detects that the DC impedance amplitude has returned to the open-circuit level, or the auxiliary load torque characteristic has disappeared, the system does not immediately stop, but instead starts a timer to enter a period of [duration missing]. A hysteresis hold window (e.g., 1.5 seconds) is established. Within this window, if the impedance signal meets the contact condition again, the system resets the timer and maintains the cleaning operation, thereby avoiding frequent motor starts and stops when the user changes brushing areas or adjusts posture. If the impedance signal does not recover within the window, and the inertial measurement module 700 detects a sharp acceleration fluctuation (characteristics matching rinsing or shaking actions), or the timer overflows, the system controls the motor to decelerate and stop, and returns to step S401 to enter sleep mode.

[0064] This control process, through a phased detection strategy, combines static impedance screening and dynamic modulation verification, ensuring both low power consumption in the sleep state and high robustness in the working state, effectively preventing false triggering during water rinsing and unexpected interruptions during brushing.

[0065] The oral contact recognition method and system disclosed in this invention are not limited to a specific motor type or driving method. In the above embodiments, the vibration motor is described as a brushless magnetic levitation motor or a linear motor that generates reciprocating vibration. In alternative embodiments, the vibration motor can also be a brushed DC motor or a coreless motor that generates rotational motion, with its output shaft 3 converting the rotational motion into the oscillation or vibration of the brush head through an eccentric wheel or gearbox mechanism. For rotary motors, the phase detection unit can be configured to detect the current ripple frequency generated by the motor commutator, or to obtain the rotation angle information through a photoelectric encoder disk, thereby serving as a phase reference for synchronous demodulation. As long as the mechanical motion can cause a periodic change in pressure between the brush head and the contact surface, the mechanical carrier modulation principle of this invention is applicable.

[0066] Regarding the signal injection method, the above embodiment uses single-frequency high-frequency carrier injection. In an alternative embodiment, the excitation generation unit can be configured to generate a composite excitation signal containing multiple frequency components, such as simultaneously injecting a low-frequency carrier (e.g., 10kHz) and a high-frequency carrier (e.g., 100kHz). The microcontroller module 100 synchronously demodulates the feedback signals at different carrier frequencies and calculates the mechanical and impedance coupling coefficients at different frequencies. By utilizing the dielectric dispersion characteristics of biological tissues, i.e., the ratio of low-frequency impedance to high-frequency impedance, and combining the coupling coefficients for weighted decision-making, the recognition accuracy for simulated materials or extremely complex environments can be further improved.

[0067] Regarding the setting of the loop reference electrode, in addition to using the handle housing or the negative terminal of the battery as a reference ground, in an alternative embodiment, a capacitive touch sensing electrode can also be integrated into the electric toothbrush handle. The microcontroller module 100 uses the signal from the capacitive sensing electrode as a third-dimensional decision input. The motor is only allowed to start when the capacitive sensing electrode detects a hand grip signal and the synchronous demodulation algorithm confirms a mouth contact signal. This multimodal fusion logic can completely prevent accidental start-up of the toothbrush when it is not held (such as when dropped or accidentally touched).

[0068] Furthermore, the digital phase-locked demodulation algorithm of this invention can be implemented not only in the time domain through product integration, but also in the frequency domain. The microcontroller module 100 can perform a fast Fourier transform on the acquired feedback signal to directly extract the frequency corresponding to the mechanical vibration. The frequency domain method calculates the signal-to-noise ratio by comparing the amplitude of the spectral components with the noise floor. This method offers greater flexibility when dealing with multi-frequency mechanical vibrations or non-sinusoidal vibration waveforms.

[0069] In summary, this invention solves the problem that traditional single-sensor technology cannot effectively distinguish between water flow and the oral environment by introducing an active mechanical and electrical modulation detection mechanism into the electric toothbrush and utilizing the unique mechanical and electrical coupling response of biological tissues. This solution eliminates the need for additional optical or acoustic sensors by drilling holes in the brush head or handle, maintaining the overall waterproof performance and aesthetics of the device. Furthermore, it utilizes existing motor and control circuit resources, resulting in high feasibility for mass production and significant cost advantages.

Claims

1. A method for oral cavity contact recognition and intelligent switching control of brushing status, applied to an electric toothbrush, the electric toothbrush comprising a handle body (2), an output shaft (3), and a brush head assembly (4), characterized in that, The method includes: The microcontroller module controls the motor drive and the feedback module to drive the output shaft (3) to generate mechanical micro-motion; The control signal injection and acquisition module injects an electrical excitation signal into the output shaft (3); The real-time mechanical phase of the vibration motor is obtained through the motor drive and feedback module. The feedback electrical signal from the acquisition loop is collected, and the feedback electrical signal is synchronously demodulated based on the real-time mechanical phase. The mechanical and impedance coupling coefficient is calculated based on the synchronous demodulation operation result. The mechanical and impedance coupling coefficient is compared with a preset judgment threshold to determine whether the brush head assembly (4) connected to the output shaft (3) is in contact with oral biological tissue. If the determination result is contact with oral biological tissue, the vibration motor is controlled to enter the cleaning working state.

2. The oral cavity contact recognition and brushing state intelligent switching control method according to claim 1, characterized in that, The output shaft (3) is connected to the signal injection and acquisition module through a non-contact capacitive coupling structure. A metal moving piece is connected to the bottom of the output shaft (3). A metal stationary piece is fixed inside the handle body (2) at the corresponding position. A high dielectric constant insulating medium is filled between the metal moving piece and the metal stationary piece to form a coupling capacitor. The carrier frequency of the electrical excitation signal is configured such that the capacitive reactance of the coupling capacitor is less than the equivalent impedance of the human body circuit.

3. The oral contact recognition and brushing state intelligent switching control method according to claim 1, characterized in that, The step of obtaining the real-time mechanical phase of the vibration motor includes: Collect the back electromotive force voltage signal at both ends of the vibration motor winding; Zero-crossing detection is performed on the back electromotive force voltage signal to identify the zero-crossing moment; The continuous phase signal characterizing the real-time physical position of the rotor is based on the reconstruction of continuous zero-crossing moments.

4. The oral cavity contact recognition and brushing state intelligent switching control method according to claim 3, characterized in that, The synchronous demodulation operation steps include: The feedback electrical signal is subjected to bandpass filtering and envelope detection to obtain a low-frequency envelope signal that reflects the instantaneous change in impedance; Generate a reference signal that is synchronous with the mechanical micro-motion frequency and is phase-locked and orthogonal; The low-frequency envelope signal is correlated with the orthogonal reference signal to extract the in-phase and quadrature components of the low-frequency envelope signal at the reference frequency.

5. The oral cavity contact recognition and brushing state intelligent switching control method according to claim 4, characterized in that, The steps for calculating the mechanical and impedance coupling coefficients include: Calculate the combined vector magnitude of the in-phase component and the quadrature component, and define the combined vector magnitude as the mechanical and impedance coupling coefficient; The determination step includes: when the mechanical and impedance coupling coefficient is greater than the preset determination threshold, it is determined that the biological tissue impedance changes synchronously with the motor vibration, thus confirming effective oral contact.

6. The oral cavity contact recognition and brushing state intelligent switching control method according to claim 1, characterized in that, The method also includes an environmental reference impedance calibration step: When the handle body (2) is placed on the charging base (1) or in an unloaded state, the environmental reference impedance is scanned and recorded; The preset judgment threshold is generated based on the environmental reference impedance mapping. When the environmental reference impedance decreases, the preset judgment threshold is increased; when the environmental reference impedance increases, the preset judgment threshold is decreased.

7. The oral cavity contact recognition and brushing state intelligent switching control method according to claim 1, characterized in that, The method also includes a frequency sweep detection step: The vibration motor is controlled to perform linear frequency sweeping or discrete frequency hopping within a preset frequency range, and the corresponding mechanical and impedance coupling coefficients are calculated at each frequency point. Analyze the rate of change of the mechanical and impedance coupling coefficient with frequency. If the rate of change conforms to the viscoelastic frequency response characteristics of biological tissue, the effectiveness of the contact is confirmed.

8. An electric toothbrush, characterized in that, The electric toothbrush, using the oral contact recognition and brushing state intelligent switching control method according to any one of claims 1 to 7, comprises: The handle body (2) is equipped with a micro-control module, a motor drive and feedback module and a signal injection and acquisition module; The output shaft (3) is located at the top of the handle body (2) and is configured as the first detection electrode; The circuit reference electrode is disposed on the negative battery ground plane inside the handle body (2) or in the gripping area of ​​the handle body (2); The microcontroller module is connected to the motor drive and feedback module and the signal injection and acquisition module, respectively, and is configured to perform synchronous demodulation operation and contact determination.

9. The electric toothbrush according to claim 8, characterized in that, It also includes an auxiliary loop calibration unit, which is connected in parallel between the loop reference electrode and system ground, and includes an adjustable gain amplifier; The microcontroller module is configured to increase the gain of the adjustable gain amplifier or decrease the output impedance of the signal injection and acquisition module when the base circuit current is detected to be lower than a preset safety baseline.

10. The electric toothbrush according to claim 8, characterized in that, It also includes an inertial measurement module, the microcontroller module being configured to perform the following state transitions: When the system is in a dormant state and the inertial measurement module detects that the acceleration exceeds the wake-up threshold, it enters the wake-up pre-detection state and activates the signal injection and acquisition module to monitor the complex impedance modulus. When the complex impedance modulus changes relative to the environmental reference impedance, it enters the micro-motion lock verification state and performs the synchronous demodulation operation. When contact with oral biological tissue is detected, the system enters the cleaning state and controls the vibration motor to accelerate to the cleaning frequency.

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