Electric toothbrush automatic start-stop control method based on oral cavity multi-sensor fusion and toothbrush

Abstract

The invention relates to the technical field of intelligent electric protector control, and discloses an electric toothbrush automatic start-stop control method based on oral cavity multi-sensor fusion and a toothbrush, the method comprises the following steps: collecting proximity sensing and ambient light illumination signals, and switching to an active detection mode when the signals accord with oral cavity darkroom characteristics; then the motor is controlled to generate micro-amplitude vibration, and the load damping characteristic quantity of the motor phase current and the optical-mechanical coupling coefficient obtained through demodulation by using the detection frequency are extracted; when it is judged that the load damping characteristic quantity and the optical-mechanical coupling coefficient both exceed a set threshold value, it is confirmed that effective contact is established between the brush head and oral soft tissue, and a motor is controlled to be started and enter a normal operation mode; and during operation, the ambient light change rate is monitored in real time, and the motor is controlled to stop when the shift-out action is recognized. According to the invention, through a multi-dimensional physical contact verification mechanism, false start splashing and invalid idling in a non-oral environment are effectively prevented.

Description

Technical Field

[0001] This invention relates to the field of intelligent personal care appliance control technology, specifically to an automatic start / stop control method and toothbrush for electric toothbrushes based on oral multi-sensor fusion. Background Technology

[0002] Currently, electric toothbrushes have become an important tool for daily oral hygiene. Traditional electric toothbrushes mainly rely on physical buttons for on / off control, requiring users to manually turn them on before placing the brush head in their mouth or manually turn them off after removing them, making the operation relatively cumbersome. To improve ease of use, some new electric toothbrushes have introduced automatic sensor-activated start / stop functions, typically using a single infrared proximity sensor or capacitive touch sensor to detect human body signals.

[0003] However, existing automatic sensing solutions have significant recognition deficiencies in practical applications. Relying solely on a single proximity sensor signal cannot accurately distinguish the nature of obstructions within the detection area. The sensor struggles to differentiate between the actual oral cavity environment and the user's fingers, palms, or other nearby non-transparent objects. When the user is applying toothpaste, cleaning the brush head, or moving the brush hand, misjudgments are easily caused by hand obstruction, leading to accidental motor activation in non-oral environments and resulting in toothpaste or water splashing.

[0004] Furthermore, to verify whether the brush head is in contact with teeth or gums, existing technologies typically require the drive motor to run at a certain speed to generate a detectable change in load current, or rely on a physical pressure sensor. If this detection method applies a high driving force before the brush head actually contacts the oral tissue, the resulting centrifugal force often disrupts the surface tension of the toothpaste or fluid, causing the toothpaste to be thrown off before entering the mouth. Simultaneously, relying solely on changes in steady-state current amplitude is insufficient to accurately capture the subtle physical characteristics of the brush head in contact with the soft tissues of the mouth, and is easily affected by friction within the mechanical structure itself or voltage fluctuations, impacting the accuracy of contact recognition.

[0005] Regarding stop control, existing technologies mostly use a fixed distance threshold as the basis for stopping the brush. When a user removes the toothbrush from their mouth, the distance between the brush head and the face or lips remains within the sensor's detection range for a certain period, causing a lag in the system's recognition of the removal action. This reaction delay allows the brush head to continue rotating at high speed even after it has completely left the oral environment, resulting in ineffective spinning and easily splashing residual foam onto the user's face or clothing. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides an automatic start-stop control method and toothbrush for electric toothbrushes based on multi-sensor fusion in the oral cavity. This solves the problem that existing electric toothbrushes rely on only a single mechanical switch or a single sensor, which makes it impossible to accurately identify the oral environment, resulting in accidental activation in non-oral environments, causing toothpaste splashing, or failure to stop in time after the toothbrush is removed from the mouth.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] The first aspect of this invention provides an automatic start / stop control method for an electric toothbrush based on oral multi-sensor fusion, comprising the following steps:

[0009] S1. Collect proximity sensing signals and ambient light intensity signals. When the proximity sensing signal indicates near-distance occlusion and the ambient light intensity signal matches the characteristics of a dark oral cavity, confirm that the electric toothbrush is in the interactive state of the oral environment to be detected, and switch to active detection mode;

[0010] S2. Control the brushless DC motor to generate micro-vibration, and use it as an active physical excitation source to verify the contact state between the brush head assembly and the oral soft tissue;

[0011] S3. Acquire the phase current signal and proximity sensing signal of the brushless DC motor. Extract the load damping characteristic quantity from the phase current signal, and use the detection frequency to demodulate the proximity sensing signal in the frequency domain to obtain the optomechanical coupling coefficient. The load damping characteristic quantity and optomechanical coupling coefficient are used as parameters characterizing the physical interaction state between the brush head assembly and the oral soft tissue;

[0012] S4. Compare the load damping characteristic quantity with the load damping threshold, and compare the optomechanical coupling coefficient with the optomechanical coupling correlation threshold. When the load damping characteristic quantity is greater than the load damping threshold and the optomechanical coupling coefficient is greater than the optomechanical coupling correlation threshold, it is determined that the brush head assembly and oral soft tissue are in contact, thereby controlling the brushless DC motor to start and enter the normal operation mode;

[0013] S5. During normal operation of the brushless DC motor, monitor the value of the proximity sensor signal and the rate of change of the ambient light intensity signal in real time. Once an interactive state change indicating that the brush head assembly is moving out of the oral cavity is detected, control the brushless DC motor to stop running.

[0014] Preferably, the process of determining that the detection area conforms to the characteristics of an oral cavity darkroom in step S1 is as follows: periodically reading the proximity sensing signal and the ambient light intensity signal according to the standby polling frequency; comparing the read proximity sensing signal with the distance determination threshold, and comparing the read ambient light intensity signal with the ambient light intensity safety threshold; when the calculated gated state variable indicates that the proximity sensing signal is greater than the distance determination threshold and the ambient light intensity signal is less than the ambient light intensity safety threshold, the detection area is determined to conform to the characteristics of an oral cavity darkroom.

[0015] Preferably, the specific method for controlling the brushless DC motor to generate micro-amplitude vibration in step S2 is as follows: generating a sine wave with a fixed frequency as a probe voltage signal sequence, wherein the fixed frequency is set to a value that avoids the first-order mechanical resonance frequency range of the overall structure of the electric toothbrush; setting the amplitude of the sine wave, wherein the output torque of the brushless DC motor corresponding to the set amplitude is less than the critical torque value required for the fluid attached to the brush head assembly to overcome the surface tension; and synthesizing the probe voltage signal sequence by adjusting the pulse width modulation duty cycle applied to the winding of the brushless DC motor.

[0016] Preferably, the process of extracting the load damping characteristic in step S3 is as follows: the acquired phase current signal is filtered using a digital bandpass filter, and the center frequency of the digital bandpass filter is matched with the detection frequency; within a preset time window, the filtered phase current signal is squared and summed to calculate the load damping characteristic.

[0017] Preferably, the process of extracting the optomechanical coupling coefficient in step S3 is as follows: using the detection frequency as a reference clock, performing quadrature synchronous demodulation operation, calculating the in-phase projection component and the quadrature projection component of the proximity sensing signal relative to the detection frequency; calculating the DC average value of the proximity sensing signal within a preset calculation time window; calculating the arithmetic square root of the sum of the squares of the in-phase projection component and the squares of the quadrature projection component, and dividing the calculation result by the DC average value to obtain the normalized optomechanical coupling coefficient.

[0018] Preferably, the process of controlling the brushless DC motor to start and enter the normal operation mode in step S4 is as follows: constructing a start-up decision function; when the load damping characteristic is greater than the load damping threshold and the optomechanical coupling coefficient is greater than the optomechanical coupling correlation threshold, setting the start-up decision function; in response to the setting of the start-up decision function, terminating the micro-amplitude vibration of the active physical excitation source; executing a soft-start program, controlling the speed of the brushless DC motor to smoothly transition from the micro-amplitude vibration state to the target clean speed according to the preset acceleration curve within the smooth start-up time, thus completing the action of entering the normal operation mode.

[0019] Preferably, the process of identifying the interactive state change of the brush head assembly moving out of the oral cavity in step S5 is as follows: the luminous flux change rate is calculated using a sliding differential algorithm; the ambient light illuminance signal collected at the current moment and the historical ambient light illuminance signal before the preset sampling time are selected for differential operation, and the corresponding time interval is divided; the calculated luminous flux change rate is compared with the positive luminous flux mutation threshold, which is set to the light intensity jump slope generated when the brush head assembly moves quickly from the shadow area inside the oral cavity to the external illumination area; when the proximity sensing signal is detected to be lower than the distance release threshold, or the luminous flux change rate is detected to exceed the positive luminous flux mutation threshold, it is determined that the brush head assembly is moving out of the oral cavity.

[0020] Preferably, the proximity sensing signal and the ambient light illuminance signal are acquired by a proximity sensor, which is located behind the optical window of the electric toothbrush, and an optical isolation structure is provided between the proximity sensor and the optical window. The proximity sensor is an integrated photoelectric sensor module, which integrates an infrared emitting diode, an infrared photodetector, and an ambient light photodiode within its physical package. The infrared photodetector is used to acquire the proximity sensing signal, and the ambient light photodiode has independent spectral response characteristics and is used to acquire the ambient light illuminance signal independently of the working state of the infrared emitting diode.

[0021] Preferably, in step S5, controlling the brushless DC motor to stop running specifically involves controlling the motor drive circuit to enter an electronic braking state, applying either a full-bridge short-circuit braking voltage vector or a reverse plug-in braking voltage vector to the three-phase windings of the brushless DC motor; the phase current signal is acquired by a current sampling module, which is connected in series with either the motor phase line or the bus circuit of the motor drive circuit.

[0022] A second aspect of this invention provides an electric toothbrush based on oral multi-sensor fusion, comprising a handle assembly, a brush head assembly, a drive unit, a proximity sensor, and a main control unit. The top of the handle assembly is provided with a power output shaft and an optical window. The brush head assembly is connected to the power output shaft, and the neck of the brush head assembly is made of a light-transmitting material. The drive unit is housed inside the handle assembly and is used to drive a brushless DC motor. The proximity sensor is disposed inside the handle assembly and located behind the optical window. The main control unit is electrically connected to both the drive unit and the proximity sensor. The main control unit is used to execute the automatic start / stop control method for the electric toothbrush based on oral multi-sensor fusion described in the first aspect.

[0023] This invention employs ambient light and proximity sensing for primary gating, combined with motor micro-perturbation signal injection technology. By analyzing the load damping characteristics in the motor phase current and the frequency domain coupling characteristics in the photoelectric signal, a multi-dimensional physical contact verification mechanism is constructed. This mechanism can distinguish between fluid load and oral soft tissue contact load, activating the motor only after confirming that the brush head has entered the oral cavity and established effective physical contact. It also triggers braking upon detecting a sudden change in light flux or distance release, thereby preventing fluid splashing and avoiding ineffective idling.

[0024] This invention provides an automatic start / stop control method and toothbrush for electric toothbrushes based on oral multi-sensor fusion. It has the following beneficial effects:

[0025] 1. This invention performs primary gating judgment by collecting proximity sensing signals and ambient light intensity signals, and performs secondary physical contact verification by combining motor load damping characteristics and optomechanical coupling coefficient, effectively distinguishing between false occlusion environments such as hand obstruction and the real oral cavity environment; this multi-sensor fusion mechanism avoids misjudgment in non-use scenarios by relying on a single signal source, and prevents fluid splashing caused by accidental activation of the electric toothbrush in non-oral environments.

[0026] 2. This invention uses the micro-amplitude vibration generated by the brushless DC motor as an active physical excitation source, extracts the load damping characteristics from the phase current, and uses the detection frequency to demodulate the proximity sensing signal in the frequency domain. Under the premise that the output torque of the brushless DC motor is less than the critical value of fluid surface tension, it can accurately identify the contact state between the brush head and the soft tissue of the oral cavity by using the load change and optical signal fluctuation generated by the micro-physical disturbance, thus improving the accuracy of start-up detection without slapping toothpaste.

[0027] 3. This invention monitors ambient light intensity signals in real time, calculates the rate of change of luminous flux using a sliding differential algorithm, and compares it with the threshold of positive luminous flux change. By utilizing the light intensity change characteristics generated when the brush head moves from the shadow area inside the oral cavity to the external illumination area, it can quickly identify the removal action and trigger electronic braking before the brush head is completely removed from the oral cavity, thus solving the problem of ineffective idling caused by the sluggish response of traditional distance sensing at critical distances. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the hardware architecture modules of an electric toothbrush system according to an embodiment of the present invention;

[0029] Figure 2 This is a general flowchart of an automatic start / stop control method for an electric toothbrush according to an embodiment of the present invention;

[0030] Figure 3 This is a timing and logic diagram of an ambient light gating and dark cavity prediction logic according to an embodiment of the present invention;

[0031] Figure 4 This is a flowchart of an optomechanical frequency domain coupling demodulation logic according to an embodiment of the present invention;

[0032] Figure 5 This is a schematic diagram of the handle assembly of the present invention;

[0033] Figure 6 This is a schematic diagram of the proximity sensor of the present invention.

[0034] The components include: 1. Handle assembly; 2. Brush head assembly; 3. Drive unit; 4. Proximity sensor; 5. Main control unit; 6. Power output shaft; and 7. Optical light transmission window. Detailed Implementation

[0035] 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.

[0036] See attached document Figure 1 Appendix Figure 5 and attached Figure 6 The present invention provides an electric toothbrush capable of recognizing the oral cavity environment and contact load characteristics, comprising a handle assembly 1, a brush head assembly 2 detachably connected to the handle assembly 1, a drive unit 3, a proximity sensor 4, and a main control unit 5.

[0037] The handle assembly 1 defines the grip body and internal space of the electric toothbrush, and its top is provided with a power output shaft 6 and an optical light transmission window 7. The brush head assembly 2 is fixedly connected to the power output shaft 6 via a mechanical coupling interface. The power output shaft 6 is configured to transmit the torque and vibration generated by the internal drive unit 3 to the bristles of the brush head assembly 2. The neck of the brush head assembly 2 is made of a light-transmitting or partially light-transmitting material, or a light-transmitting hole is provided at the position corresponding to the optical light transmission window 7 of the handle assembly 1, so as to allow light signals to pass through the neck area of ​​the brush head assembly 2 or pass through the side of the brush head assembly 2, thereby forming an effective detection field of view in front of the proximity sensor 4.

[0038] The drive unit 3, housed within the handle assembly 1, includes a brushless DC motor and a motor drive circuit. The brushless DC motor is coaxially connected to the power output shaft 6 and configured to generate rotational or acoustic vibrations for cleaning teeth. The motor drive circuit includes a full-bridge or three-phase inverter power stage, whose input is connected to the pulse-width modulation (PWM) output port of the main control unit 5. The motor drive circuit also includes a current sampling module connected in series in the motor phase line or bus circuit, configured to acquire the phase current signal flowing through the brushless DC motor windings in real time. This phase current signal is transmitted to the main control unit 5 to monitor changes in load torque and back electromotive force characteristics of the motor during operation. The drive unit 3 can switch between a high-frequency, high-amplitude vibration state in a normal cleaning mode and a high-frequency, low-amplitude disturbance state in an active detection mode, in response to control commands from the main control unit 5.

[0039] The proximity sensor 4 is located inside the handle assembly 1, behind the optical window 7, and aligned towards the brush head assembly 2. To prevent internal light reflection interference, an optical isolation structure is provided between the proximity sensor 4 and the optical window 7. The proximity sensor 4 is an integrated photoelectric sensor module, which integrates an infrared emitting diode, an infrared photodetector, and an ambient light photodiode within its physical package. The proximity sensor 4 is configured to output two dimensions of physical quantity data in parallel to the main control unit 5 via a single communication bus (e.g., I2C bus) or independent analog / digital signal lines: the first dimension is the proximity sensing signal (i.e., the intensity of the reflected signal), characterizing the distance and surface reflectivity of obstacles in front of the sensor; the second dimension is the ambient light illuminance signal, characterizing the background luminous flux density of the environment in which the sensor is located. The ambient light photodiode has independent spectral response characteristics and can continuously monitor the intensity of external visible light independently of the operating state of the infrared emitting diode.

[0040] The main control unit 5 is mounted on a printed circuit board (PCB) within the handle assembly 1 and is electrically connected to the drive unit 3 and the proximity sensor 4, respectively. The main control unit 5 includes a microprocessor (MCU), an analog-to-digital converter (ADC), and digital signal processing logic. The main control unit 5 is configured to execute multi-sensor fusion control logic, including generating and injecting a micro-disturbance detection signal of a specific frequency into the drive unit 3, and synchronously acquiring the proximity sensing signal output by the proximity sensor 4. The main control unit 5 integrates a synchronous demodulation algorithm module or hardware logic, configured to use the motor drive frequency as a reference clock to perform frequency domain demodulation on the proximity sensing signal to extract the wave component in the optical signal that is at the same frequency as the mechanical vibration frequency of the motor.

[0041] The main control unit 5 is also equipped with a data storage device for storing preset distance judgment thresholds, ambient light illuminance safety thresholds, load damping thresholds, and optomechanical coupling correlation coefficients. The main control unit 5 determines whether the brush head assembly 2 is currently located inside the oral cavity and in contact with the soft tissue by comparing real-time acquired proximity sensing signals, ambient light illuminance signals, motor feedback current signals, and calculated optomechanical coupling coefficients. It then controls the drive unit 3 to perform start-up, maintenance, or active braking operations. The electric toothbrush also includes a power supply battery and a power management module to provide a stable operating voltage for the aforementioned electronic components.

[0042] See attached document Figure 2 This invention provides an automatic start / stop control method for electric toothbrushes based on oral multi-sensor fusion. This control method is executed by the main control unit 5, which coordinates the working states of the drive unit 3 and the proximity sensor 4 to achieve automatic recognition and response to oral cleaning scenarios.

[0043] In step S1, ambient light gating and dark cavity prediction are performed. The main control unit 5 controls the proximity sensor 4 to operate in low-power mode, periodically collecting proximity sensing signals and ambient light signals. The main control unit 5 first determines whether the proximity sensing signal exceeds a preset distance judgment threshold to confirm whether an object has entered the sensor's detection range.

[0044] If an object is detected approaching, the main control unit 5 further compares the current ambient light intensity signal with a preset ambient light intensity safety threshold. If the ambient light intensity signal is higher than the safety threshold, it indicates that the current environment is a high-brightness non-oral environment, and the main control unit 5 determines that the trigger is invalid, and the system remains in standby mode to prevent accidental activation. When an object is detected approaching and the ambient light intensity signal is lower than the safety threshold, the main control unit 5 determines that the detection area matches the characteristics of an oral cavity darkroom, and the control system switches to active detection mode.

[0045] In step S2, a micro-disturbance detection signal is injected. In response to entering active detection mode, the main control unit 5 generates a micro-amplitude AC drive signal with a specific detection frequency and superimposes it onto the control port of the drive unit 3. In response to this drive signal, the drive unit 3 drives a brushless DC motor to generate high-frequency micro-amplitude vibrations. The amplitude of this vibration is set to be insufficient to generate mechanical energy that would cause fluid adhering to the brush head assembly 2 to splash, but sufficient to cause micro-displacement of the medium in contact with the brush head assembly 2.

[0046] In step S3, dual verification of optomechanical frequency domain coupling and load impedance is performed. During the high-frequency micro-amplitude vibration of the brushless DC motor, the main control unit 5 performs feature extraction in two dimensions in parallel. In the electrical dimension, the main control unit 5 acquires the phase current signal of the brushless DC motor and extracts the amplitude response of the current signal at the detection frequency to calculate the load damping characteristic quantity characterizing the mechanical impedance of the contact surface.

[0047] In the optomechanical coupling dimension, the main control unit 5 uses the detection frequency of the injected motor as a reference clock to synchronously demodulate the simultaneously acquired proximity sensing signals. The main control unit 5 calculates the cross-correlation between the fluctuation component of the proximity sensing signal and the mechanical vibration frequency of the motor to obtain the optomechanical coupling coefficient. This step is used to verify whether the reflective surface located in front of the sensor undergoes forced vibration at the same frequency as the brush head assembly 2.

[0048] In step S4, multi-dimensional data fusion decision-making and initiation are performed. The main control unit 5 compares the calculated load damping characteristic and optomechanical coupling coefficient with preset load damping threshold and optomechanical coupling correlation threshold, respectively. Only when the load damping characteristic indicates a high-damping state and the optomechanical coupling coefficient indicates that there is mechanical coupling at the same frequency on the reflecting surface, the main control unit 5 determines that the brush head assembly 2 has entered the oral cavity and established effective contact with the oral soft tissue. At this time, the main control unit 5 controls the drive unit 3 to enter the normal operation mode, and controls the brushless DC motor to smoothly transition from a micro-amplitude vibration state to the target cleaning speed according to a preset acceleration curve.

[0049] In step S5, active braking based on luminous flux mutation is performed. During normal operation of the brushless DC motor, the main control unit 5 continuously monitors the rate of change of the ambient illuminance signal and the value of the proximity sensor signal. The main control unit 5 calculates the first derivative or difference of the ambient illuminance signal with respect to time.

[0050] When the main control unit 5 detects that the proximity sensing signal is below the distance release threshold, or detects that the rate of change of the ambient light intensity signal exceeds the positive luminous flux mutation threshold, it determines that the brush head assembly 2 is being removed from the oral cavity. In response to this determination, the main control unit 5 immediately sends a braking command to the drive unit 3, controlling the motor drive circuit to enter the electronic braking state, applying a reverse braking torque to the brushless DC motor, so that the brush head assembly 2 stops vibrating the instant it leaves the oral cavity environment.

[0051] See attached document Figure 3 In step S1, the main control unit 5 is configured to periodically wake up the proximity sensor 4 at a preset standby polling frequency. The standby polling frequency is set to a value lower than the normal operating frequency, for example, 5Hz to 20Hz, to reduce the energy consumption of the system in the non-operating state.

[0052] At each sampling time The main control unit 5 synchronously reads the current proximity sensing signal from the proximity sensor 4 via a digital bus. and ambient light intensity signal These two signals are independently acquired by the infrared photodetector and ambient light photodiode inside the proximity sensor 4, respectively, ensuring the temporal consistency between distance information and ambient light information.

[0053] The main control unit 5 first processes the proximity sensing signal. The validity is determined. The main control unit 5 calls the distance determination threshold stored in the data memory. and will Compare with this threshold. Proximity sensing signal. The numerical value represents the physical distance between the object and the sensor surface; the closer the object, the stronger the reflected signal. Distance determination threshold. The signal strength value is set to correspond to a physical position where the object is approximately 2 to 5 centimeters away from the sensor surface. If Less than or equal to This indicates that there are no nearby objects obstructing the sensor, and the main control unit 5 ignores the current sampling period and maintains standby mode.

[0054] like Greater than The main control unit 5 further analyzes the ambient light intensity signal. The characteristics of the dark cavity are verified. This verification process is based on the physical characteristic that the internal environment of the oral cavity has a lower light flux compared to the external open environment. The main control unit 5 collects the ambient light intensity signal. Compared with the ambient light illuminance safety threshold preset in the data storage Comparison. Ambient light illuminance safety threshold. The value range is set to correspond to an illuminance between 10 lux and 50 lux, which can effectively distinguish the shadow area of ​​the hand from the true closed oral cavity.

[0055] The main control unit 5 calculates the gated state variables based on the comparison results of the above two dimensions. Its logical operation expression is as follows:

[0056] ;

[0057] in: This represents the gating state variable. When its value is 1, it indicates that the start-up pre-condition is met; when its value is 0, it indicates that it is not met. Indicates the first Proximity sensing signals collected at each sampling time; This indicates the preset distance threshold. Indicates the first Ambient light intensity signals were collected at each sampling time. This indicates the preset safe threshold for ambient light illuminance; Represents the logical AND operation.

[0058] When the calculated gated state variable When the value is 0, it indicates that although there is an object approaching in the current scene, the ambient light is too strong, such as when a user is rinsing the brush head under a tap or holding the brush head and moving it under a bathroom light. At this time, the main control unit 5 is prohibited from sending a start command to the drive unit 3 and continues to execute the next cycle of standby polling, thereby avoiding false triggering caused by simple distance detection.

[0059] When the calculated gated state variable When the value is 1, it indicates that the current scene simultaneously meets the characteristics of close-range occlusion and low-light darkroom, which meets the physical preconditions for the brush head assembly 2 to enter the oral cavity. In response to this state, the main control unit 5 switches the system state from standby mode to active detection mode and triggers the subsequent step S2 to perform further physical contact verification.

[0060] See attached document Figure 2 In response to the system determining that the dark cavity prediction conditions are met and entering the active detection mode, the main control unit 5 executes step S2 and begins to send specific voltage control commands to the drive unit 3 to drive the brushless DC motor to generate micro-amplitude vibrations for non-cleaning purposes.

[0061] The main control unit 5 uses an internally integrated waveform generator or a pre-stored sine lookup table to generate discrete probe voltage signal sequences. The probe voltage signal sequence is constructed into a sinusoidal waveform with a fixed frequency and limited amplitude, and is input as a modulation signal to the pulse width modulation (PWM) generation module of the motor drive circuit to control the switching state of the inverter power stage. The mathematical expression for is defined as follows:

[0062] ;

[0063] in: Indicates the first A sequence of probe voltage signals applied to the brushless DC motor at each sampling time; The value of the micro-perturbation amplitude coefficient is set to correspond to the critical torque value required for the output torque of the brushless DC motor to overcome the surface tension of the fluid (e.g., toothpaste foam or water droplets) attached to the brush head assembly 2, thereby ensuring that the mechanical displacement generated by the brush head assembly 2 during the detection process is insufficient to cause fluid splashing. It represents the operation of sine trigonometric functions, used to establish the periodic oscillation characteristics of the driving signal; It represents twice the constant of pi and is used to convert frequency values ​​into angular frequency units; The detection frequency is set to avoid the first-order mechanical resonance frequency range of the overall structure of the brush head assembly 2 and the handle assembly 1. It is usually selected between 100Hz and 200Hz to ensure the linearity of the vibration transmission characteristics and prevent the amplitude runaway caused by resonance from affecting the subsequent detection accuracy. The sampling period of the signal is represented by its reciprocal, which is the update frequency of the system control loop. This represents the current discrete time point.

[0064] The main control unit 5 synthesizes a probe voltage signal sequence by dynamically adjusting the PWM duty cycle applied to the brushless DC motor windings. The micro-disturbance detection signal is continuously injected until the system completes the contact state determination or reaches the preset timeout reset time. During this period, the rotor of the brushless DC motor is controlled to generate a small reciprocating oscillation near the magnetic balance position. This micro-oscillation is physically transmitted to the brush head assembly 2 through the power output shaft 6, serving as the active physical excitation source required for load impedance detection and optomechanical coupling verification in the subsequent step S3.

[0065] See attached document Figure 2 In step S3, along with the injection of micro-disturbance detection signals, the main control unit 5 initiates the electrical dimension feature extraction program to evaluate the mechanical load characteristics of the brush head assembly 2.

[0066] The main control unit 5 utilizes the current sampling module 33 integrated in the drive unit 3 to acquire the phase current signal flowing through the brushless DC motor windings in real time at a sampling rate synchronized with or higher than the PWM switching frequency. The phase current signal includes the motor drive torque component and the back electromotive force disturbance component caused by the reaction force of the mechanical load.

[0067] In order to separate the current signal solely by the detection frequency The resulting response component, the main control unit 5, reacts to the acquired phase current signal. Perform digital bandpass filtering. The center frequency of the digital bandpass filter is configured to precisely match the detection frequency set in step S2 above. Its bandwidth is set to a narrow range to effectively filter out DC bias, high-frequency switching noise, and mechanical vibration interference at non-detection frequencies.

[0068] The main control unit 5, based on the filtered current signal, within a preset time window length... Internal calculation of load damping characteristic quantity The load damping characteristic represents the energy consumption level of a brushless DC motor under a specific frequency excitation, and its calculation formula is defined as follows:

[0069] ;

[0070] in: This represents the calculated load damping characteristic quantity; This represents the total number of sampling points within the preset time window, i.e., the preset time window length, and is a positive integer. This represents a mathematical operation that sums up all sampled points within a time window. This indicates that a detection frequency of 10 ... The digital bandpass filter operation outputs a filtered current value that retains only the probe frequency component. Indicates the first Phase current signals acquired at each sampling time; This represents the squaring operation, used to calculate the instantaneous power or energy representation value of a signal; This represents the normalization coefficient, used to calculate the average value; This represents the arithmetic square root operation, used to restore the dimensions of a quantity to the dimension of current amplitude.

[0071] When the brush head assembly 2 operates under no-load conditions in the air, the rotor of the brushless DC motor experiences relatively large motion amplitude under micro-disturbance excitation due to the minimal air damping. Conversely, when the brush head assembly 2 contacts viscous fluids (such as toothpaste foam or saliva) or soft tissues (such as gums or cheek walls) inside the oral cavity, the mechanical damping generated at the contact interface increases, suppressing the micro-vibration of the rotor and resulting in a decrease in the load damping characteristic value. Significant changes have occurred. The main control unit 5 will calculate... It is stored in the data memory for fusion decision in the subsequent step S4.

[0072] See attached document Figure 4 In step S3, in parallel with the extraction of electrical load damping features, the main control unit 5 performs signal processing in the optomechanical coupling dimension to verify whether the reflective interface located in front of the proximity sensor 4 has a physical coupling relationship with the micro-perturbation of the brushless DC motor.

[0073] The main control unit 5 uses the detection frequency determined in the previous step S2. Using a reference clock, the acquired proximity sensing signal is... Perform orthogonal synchronous demodulation. This operation aims to extract the frequency components in the reflected signal that are strictly equal to... The dynamic amplitude is controlled while suppressing background noise interference from DC components and other frequencies. The main control unit 5 first calculates the preset time window length. Within each component, the in-phase projection component of the proximity sensing signal relative to the detection frequency is calculated. and orthogonal projection components In-phase projection components and orthogonal projection components The calculation formulas are defined as follows:

[0074] ;

[0075] ;

[0076] in: This represents the in-phase projection component of the proximity sensing signal at the detection frequency. This represents the orthogonal projection component of the proximity sensing signal at the detection frequency; This indicates that the discrete data points within the calculation window are summed. Indicates the first Proximity sensing signals collected at each sampling time; and These represent the sine and cosine functions, respectively, used to construct orthogonal reference signals; It represents twice the constant of pi and is used to convert frequency values ​​into angular frequency units; The detection frequency is set to avoid the first-order mechanical resonance frequency range of the overall structure of the brush head assembly 2 and the handle assembly 1. It is usually selected between 100Hz and 200Hz to ensure the linearity of the vibration transmission characteristics and prevent the amplitude runaway caused by resonance from affecting the subsequent detection accuracy. The sampling period of the signal is represented by its reciprocal, which is the update frequency of the system control loop. This represents the current discrete time point; This represents the total number of sampling points within the calculation window, and this value is consistent with the window length in the electrical damping extraction step.

[0077] Based on the calculated in-phase projection components and orthogonal projection components and the DC accumulation component of the proximity induction signal. The main control unit 5 further calculates the optomechanical coupling coefficient. This calculation employs a normalized modulation depth method to eliminate the influence of reflection distance on the fluctuation amplitude. Optomechanical coupling coefficient. The calculation formula is defined as follows:

[0078] ;

[0079] in: This represents the normalized optomechanical coupling coefficient, the magnitude of which directly reflects the frequency of the probe driven by the brushless DC motor on the surface of the reflecting object. The amplitude of the synchronous vibration; This represents the DC average value of the signal within the calculation window, used to eliminate the influence of the absolute distance of the object on the detection sensitivity; This represents the arithmetic square root operation, used to calculate the magnitude of a vector. and This indicates that the in-phase and quadrature components are squared separately to obtain the energy dimension value.

[0080] When the object in front of proximity sensor 4 is a stationary rigid object (such as a palm, a wall, or the surface of a stationary water tank), the proximity sensing signal will not be detected. The average value is relatively high (indicating close proximity), but since the object is not physically connected to brush head assembly 2, it does not follow the brushless DC motor to generate a detection frequency of [missing value]. Forced vibration, therefore Not included The AC component of the probe frequency is calculated. and Approaching zero, thus making It remains in an extremely low value range.

[0081] Conversely, when the brush head assembly 2 is in close contact with the soft tissues of the mouth (e.g., the inner cheek wall, tongue, or gums), micro-vibrations are transmitted through the bristles to the surface of the soft tissue, causing microscopic deformation and displacement. This synchronous microscopic displacement modulates the optical path and reflection angle of the reflected infrared light, making... Presented frequency is The periodic fluctuations. At this time, the result calculated by the aforementioned synchronization demodulation algorithm... This will result in a significantly high value, thus achieving accurate identification of the specific physical state of contact with oral tissue. The main control unit 5 will calculate... The values ​​are temporarily stored in the data storage for use in subsequent fusion decisions.

[0082] See attached document Figure 2 In step S4, the main control unit 5 calculates the load damping characteristic value obtained in parallel in the previous step S3. Optomechanical coupling coefficient The joint decision logic is executed to determine whether to trigger the formal clean operation mode of the brushless DC motor.

[0083] The main control unit 5 calls the load damping threshold pre-stored in the data memory. Correlation threshold between optomechanical coupling Load damping threshold Set to a damping value greater than the baseline under no-load conditions, used to distinguish between air media and fluid or soft tissue media. Optomechanical coupling correlation threshold. It is set to a noise floor value greater than that generated by the static reflective surface to distinguish between static obstructions and dynamically coupled oral tissues. The main control unit 5 constructs the startup decision function. This function uses a logical AND operation mechanism to ensure the uniqueness and accuracy of contact determination. Its mathematical expression is defined as follows:

[0084] ;

[0085] in: This represents the start-up decision function. When its calculation result is 1, it indicates that the start-up condition is met; when it is 0, it indicates that the start-up condition is not met. This represents the calculated load damping characteristic quantity; This indicates the greater than comparison operator; Indicates the load damping threshold; This indicates a logical AND operation or an arithmetic multiplication operation. The result is 1 only when both terms on both sides of the multiplication sign are 1. This represents the normalized optomechanical coupling coefficient, the magnitude of which directly reflects the change in the reflective surface of the object as driven by the brushless DC motor. The amplitude of the synchronous vibration; This represents the threshold for optomechanical coupling correlation. This represents an indicative function used to convert the result of a logical judgment into a numerical value. The function value is 1 when the logical condition within the parentheses is true, and 0 otherwise.

[0086] The decision function is activated only when both conditions are met simultaneously: the electrical detection indicates a high-damped load and the optical detection indicates strong mechanical coupling. Only then is it set to 1. This dual verification mechanism effectively filters out false positives caused by single-dimensional detection: for example, when the user grips the brush head assembly 2 tightly, although... Exceeding due to hand damping However, because the hand muscles cannot follow the high-frequency micro-perturbations of the brushless DC motor to produce the same frequency deformation, it leads to... Below Thus making When the value is 0, the system remains silent; similarly, when brush head assembly 2 is in the air and only water droplets are attached, although the light signal fluctuates, Even when in a low-level position, the system will not start accidentally.

[0087] Once the decision function is started Upon confirmation of a value of 1, the main control unit 5 immediately terminates the active detection mode and switches to normal operation mode, executing the soft-start procedure. The main control unit 5 no longer controls the speed of the brushless DC motor to be limited by micro-disturbance conditions, but instead increases the speed according to a preset linear acceleration curve. The main control unit 5 then performs a smooth start-up within a preset time. Within 0.5 to 1.0 seconds, the motor speed is smoothly increased from zero or a slight disturbance frequency to the user-set target operating speed. This soft-start process avoids toothpaste splattering or gum discomfort caused by sudden torque changes.

[0088] In response to the start decision function When set to 1, the main control unit 5 immediately terminates the injection of the micro-disturbance detection signal and switches to closed-loop speed control mode to execute a smooth start-up procedure. This procedure aims to establish a time-dependent speed reference trajectory, enabling the output speed of the brushless DC motor to smoothly transition from zero or a micro-disturbance state to the user-set target operating speed, thereby eliminating the risk of fluid splashing caused by sudden torque changes.

[0089] Main control unit 5 is based on a preset smooth start-up time and target operating speed Generate a discrete-time velocity reference command sequence The speed reference command sequence exhibits a linear or quasi-S-shaped increasing characteristic during the startup phase, rather than a step change. Within each speed control cycle, the main control unit 5 updates the reference speed for the current cycle based on the reference speed value from the previous speed control cycle and a fixed acceleration step size. Speed ​​Reference Command Sequence The update logic is defined as follows:

[0090] ;

[0091] in: Indicates the first A sequence of speed reference commands for each speed control cycle; This represents the minimum value function, used to implement amplitude clamping logic to ensure that the calculation result does not exceed the set upper limit value; This represents the speed reference command sequence of the previous speed control cycle, which is at the start of the soft start process ( The initial value of ) is set to zero or the average speed value actually fed back by the motor at the current moment, to ensure a smooth acceleration from a state of slight vibration to the target speed; This indicates the target operating speed determined based on the cleaning mode selected by the user (e.g., clean, whitening, sensitive mode); This represents the update control period of the speed loop, which is typically greater than or equal to the signal sampling period. (For example, set to 1 millisecond to 10 milliseconds); This represents the preset smooth start time, and its value determines the slope of the acceleration process, used to determine the speed increment per unit time.

[0092] The main control unit 5 will calculate the speed reference command sequence. This information is passed as input to the motor control loop (e.g., a PID controller or FOC controller). Based on the deviation between the speed reference command sequence and the real-time feedback speed, the motor control loop dynamically adjusts the inverter's duty cycle and commutation timing, forcing the brushless DC motor to closely follow the actual physical speed. The trajectory rises. When the actual rotational speed reaches... Afterward, the system enters a steady-state operation phase, continuously performing the teeth cleaning operation until the stop condition is triggered.

[0093] See attached document Figure 2 During the normal operation of the brushless DC motor, the main control unit 5 continuously executes step S5 to monitor the proximity sensing signal output by the proximity sensor 4 in parallel at a high sampling rate. and ambient light intensity signal This monitoring process is designed to capture physical events that cause the brush head assembly 2 to detach from the oral cavity environment in real time, thereby cutting off the power output in time before fluid splashing occurs.

[0094] The main control unit 5 first calculates the rate of change of the ambient light intensity signal over time to identify the instantaneous characteristics of the transition from the dark environment of the oral cavity to the bright external environment. To suppress the interference of high-frequency light noise on the differential calculation, the main control unit 5 employs a sliding difference algorithm to calculate the rate of change of luminous flux. The algorithm selects the current time and... The calculation is performed using historical data prior to each sampling time, and the formula is defined as follows:

[0095] ;

[0096] in: Indicates the first The rate of change of ambient illuminance at each sampling time reflects the degree of instantaneous fluctuation in luminous flux density; Indicates the first The current ambient illuminance signal collected at each sampling time; Indicates the first Historical ambient light intensity signals collected at each sampling time; This represents the sampling period of the system, and its reciprocal is the update frequency of the system control loop. This represents the time interval corresponding to the difference operation.

[0097] Based on the calculated rate of change of ambient light intensity and real-time distance signal, the main control unit 5 constructs a shutdown trigger logic. The shutdown trigger logic includes two parallel trigger conditions: the release of physical distance and a sudden change in the light environment. The main control unit 5 calculates the shutdown trigger flag according to the following logical expression. :

[0098] ;

[0099] in: This indicates a shutdown trigger flag; when its value is True, it indicates that the system must stop operating immediately. Indicates the first Proximity sensing signals collected at each sampling time; This indicates the distance release threshold, which is set to be less than the distance determination threshold in step S1. This introduces a hysteresis loop into the decision logic to prevent the system from frequently starting and stopping due to slight positional jitter during brushing. Indicates the first The rate of change of ambient illuminance at each sampling time reflects the degree of instantaneous fluctuation in luminous flux density; This represents the threshold for the abrupt change in positive luminous flux, which is set to correspond to the slope of the light intensity jump produced when the brush head assembly 2 moves rapidly from the shadow area inside the oral cavity to the external illumination area.

[0100] When the brush head assembly 2 is normally located in the oral cavity, the ambient light illuminance signal remains at a low level and changes gradually, while the reflected infrared signal remains at a high level. The status remains false, and the motor continues to run. If any of the following occurs when the user removes brush head assembly 2 from the mouth, Flip to true: or the sensor detects that the distance to the reflective object exceeds the set release distance. Or, the sensor detected a sharp increase in the intensity of external light within a short period of time. This usually happens the instant the brush head assembly 2 crosses the lip boundary.

[0101] In response to the stop trigger flag Upon activation, the main control unit 5 immediately interrupts the normal commutation sequence and enters electronic braking mode. The main control unit 5 controls the power switching transistors in the motor drive circuit to apply a full-bridge short-circuit braking or reverse plug-in braking voltage vector to the three-phase windings of the brushless DC motor. This operation generates an electromagnetic braking torque opposite to the rotor's rotation direction, causing the motor speed to rapidly decelerate to zero in a very short time (e.g., less than 100 milliseconds). This ensures that vibration stops before the brush head assembly 2 is completely removed from the mouth and exposed to open space, effectively preventing toothpaste foam or water adhering to the bristles from splashing outwards.

Claims

1. An automatic start / stop control method for electric toothbrushes based on oral multi-sensor fusion, characterized in that, Includes the following steps: S1. Collect proximity sensing signals and ambient light intensity signals. When the proximity sensing signal indicates close-range occlusion and the ambient light intensity signal matches the characteristics of an oral dark chamber, confirm that the electric toothbrush is in the oral environment interaction state to be detected, and switch to active detection mode. S2. Control the brushless DC motor to generate micro-amplitude vibration as an active physical excitation source for verifying the contact state between the brush head assembly (2) and the oral soft tissue; S3. Collect the phase current signal of the brushless DC motor and the proximity sensing signal, extract the load damping characteristic from the phase current signal, and use the detection frequency to demodulate the proximity sensing signal in the frequency domain to obtain the optomechanical coupling coefficient. S4. Compare the load damping characteristic quantity and the load damping threshold, and compare the optomechanical coupling coefficient and the optomechanical coupling correlation threshold. When the load damping characteristic quantity is greater than the load damping threshold and the optomechanical coupling coefficient is greater than the optomechanical coupling correlation threshold, determine that the brush head assembly (2) and the oral soft tissue are in contact, and control the brushless DC motor to start and enter the normal operation mode. S5. During the normal operation mode of the brushless DC motor, the value of the proximity sensing signal and the rate of change of the ambient light intensity signal are monitored in real time. When the brush head assembly (2) is detected to be moving out of the oral cavity, the brushless DC motor is controlled to stop running.

2. The method for automatic start / stop control of an electric toothbrush based on oral multi-sensor fusion according to claim 1, characterized in that, In step S1, the step of confirming that the electric toothbrush is in the oral environment interaction state to be detected is specifically as follows: The proximity sensing signal and the ambient light intensity signal are periodically read according to the standby polling frequency; The proximity sensing signal read is compared with the distance determination threshold, and the ambient light intensity signal read is compared with the ambient light intensity safety threshold. Only when the calculated gating state variable indicates that the proximity sensing signal is greater than the distance determination threshold and the ambient light intensity signal is less than the ambient light intensity safety threshold, is the detection area determined to conform to the oral cavity dark chamber characteristics, and the electric toothbrush confirmed to be in the oral environment interaction state to be detected.

3. The method for automatic start / stop control of an electric toothbrush based on oral multi-sensor fusion according to claim 1, characterized in that, In step S2, controlling the brushless DC motor to generate micro-amplitude vibration is specifically used for: A sinusoidal waveform with a fixed frequency is generated as a sequence of probe voltage signals, wherein the fixed frequency is set to a value that avoids the first-order mechanical resonance frequency range of the overall structure of the electric toothbrush. The amplitude of the sine waveform is set, and the output torque of the brushless DC motor corresponding to the set amplitude is less than the critical torque value required for the fluid attached to the brush head assembly (2) to overcome the surface tension; The probe voltage signal sequence is synthesized by adjusting the pulse width modulation duty cycle applied to the brushless DC motor windings.

4. The method for automatic start / stop control of an electric toothbrush based on oral multi-sensor fusion according to claim 1, characterized in that, In step S3, the step of extracting the load damping characteristic quantity from the phase current signal is specifically as follows: The acquired phase current signal is filtered using a digital bandpass filter, wherein the center frequency of the digital bandpass filter is matched to the detection frequency. Within a preset time window, the filtered phase current signal is squared and summed to calculate the load damping characteristic.

5. The method for automatic start / stop control of an electric toothbrush based on oral multi-sensor fusion according to claim 1, characterized in that, In step S3, the step of using the detection frequency to perform frequency domain demodulation on the proximity sensing signal to obtain the optomechanical coupling coefficient is specifically as follows: Using the detection frequency as a reference clock, an orthogonal synchronous demodulation operation is performed to calculate the in-phase projection component and the orthogonal projection component of the proximity sensing signal relative to the detection frequency; Calculate the DC average value of the proximity sensing signal within a preset time window. Calculate the arithmetic square root of the sum of the squares of the in-phase projection components and the squares of the orthogonal projection components, and divide the calculation result by the DC average value to obtain the normalized optomechanical coupling coefficient.

6. The method for automatic start / stop control of an electric toothbrush based on oral multi-sensor fusion according to claim 1, characterized in that, In step S4, the specific steps of controlling the brushless DC motor to start and enter normal operation mode are as follows: Construct a start-up decision function, and set the start-up decision function when the load damping characteristic is greater than the load damping threshold and the optomechanical coupling coefficient is greater than the optomechanical coupling correlation threshold at the same time. In response to the setting of the start decision function, the micro-amplitude vibration of the active physical excitation source is terminated; The soft start procedure is executed, and the speed of the brushless DC motor is controlled to smoothly transition from a state of slight vibration to the target clean speed according to the preset acceleration curve within the smooth start time, thus completing the action of entering the normal operation mode.

7. The method for automatic start / stop control of an electric toothbrush based on oral multi-sensor fusion according to claim 1, characterized in that, In step S5, the step of recognizing the interactive state change that the brush head assembly (2) is moving out of the oral cavity is specifically as follows: The sliding difference algorithm is used to calculate the rate of change of luminous flux. The ambient illuminance signal collected at the current time and the historical ambient illuminance signal before the preset sampling time are selected for difference operation, and the corresponding time interval is divided. The calculated rate of change of luminous flux is compared with the positive luminous flux mutation threshold, which is set to the slope of light intensity jump when the brush head assembly (2) moves rapidly from the shadow area inside the oral cavity to the external illumination area. When the proximity sensing signal is detected to be below the distance release threshold, and when the rate of change of luminous flux is detected to exceed the positive luminous flux mutation threshold, it is determined that the brush head assembly (2) is being removed from the oral cavity.

8. The method for automatic start / stop control of an electric toothbrush based on oral multi-sensor fusion according to claim 1, characterized in that, The proximity sensing signal and the ambient light intensity signal are collected by the proximity sensor (4). The proximity sensor (4) is located behind the optical light transmission window (7) of the electric toothbrush, and a light isolation structure is provided between the proximity sensor (4) and the optical light transmission window (7). The proximity sensor (4) is an integrated photoelectric sensor module. The physical package of the proximity sensor (4) module integrates an infrared emitting diode, an infrared photodetector, and an ambient light photodiode. The infrared photodetector is used to collect the proximity sensing signal, and the ambient light photodiode has independent spectral response characteristics, which are used to collect the ambient light illuminance signal independently of the working state of the infrared emitting diode.

9. The method for automatic start / stop control of an electric toothbrush based on oral multi-sensor fusion according to claim 1, characterized in that, In step S5, controlling the brushless DC motor to stop running is specifically used to control the motor drive circuit to enter the electronic braking state, and to apply either the full-bridge short-circuit braking voltage vector or the reverse plug-in braking voltage vector to the three-phase windings of the brushless DC motor. The phase current signal is acquired by a current sampling module, which is connected in series with either the motor phase line or the bus circuit of the motor drive circuit.

10. An electric toothbrush based on oral multi-sensor fusion, characterized in that, The method for automatic start-stop control of an electric toothbrush based on oral multi-sensor fusion according to any one of claims 1-9 includes a handle assembly (1), the top of which is provided with a power output shaft (6) and an optical light transmission window (7), and a brush head assembly (2) is provided on the outside of the power output shaft (6); a drive unit (3) is provided inside the handle assembly (1) for driving a brushless DC motor, and a proximity sensor (4) is also provided inside the handle assembly (1) behind the optical light transmission window (7). A main control unit (5) is also provided inside the handle assembly (1), and the main control unit (5) is electrically connected to the drive unit (3) and the proximity sensor (4) respectively.

Images