Constant-amplitude high-frequency vibration motor and control method therefor

Abstract

A constant-amplitude high-frequency vibration motor and a control method therefor. The structure of the constant-amplitude high-frequency vibration motor comprises a motor frame, an electromagnetic coil, a damping block, a vibration arm assembly, a front cover, and magnets; the front cover is arranged at the front end of the motor frame, and the magnets are arranged at the rear end of the motor frame; an inner cavity is formed in the motor frame to accommodate the vibration arm assembly; the outer edge of the rear portion of the inner cavity is covered with the electromagnetic coil; the vibration arm assembly comprises a swing arm, a rotating shaft, a bearing, and a connecting frame; the swing arm is a linear iron swing arm; the rear portion of the swing arm is located in the electromagnetic coil on the rear portion of the inner cavity; a disc portion is formed at the front portion of the swing arm, and the disc portion is provided with a shaft hole for the rotating shaft to pass through; and the rear end of the connecting frame covers the front portion of the swing arm and forms a cylindrical structure for accommodating the disc portion of the swing arm, and the front end of the connecting frame is connected to the rear end of an output shaft to output power. In this way, the present invention can overcome defects of the prior art, solve the problems of excessive noise and wear-induced lifespan issue in actual use, and provide more constant and reliable power output.

Description

Constant Amplitude High-Frequency Vibration Motor and Its Control Method Technical Field

[0001] This invention relates to the technical field of motors for electric toothbrushes, and more particularly to a constant amplitude high-frequency oscillating motor suitable for electric toothbrushes and its control method. Background Technology

[0002] Currently, electric toothbrushes commonly use DC motors for driving. However, the maximum operating speed of a DC motor-driven electric toothbrush is less than 133Hz, and it requires gear sets or lever linkages to complete torque conversion. Otherwise, the direct-drive output torque would be too small to meet the power requirements for cleaning. For example, to ensure the brush head can operate effectively at 140-350Hz, the DC motor speed must be 2-4 times higher than the brush plate's output speed for the gear set's torque conversion. Under these conditions, conventional power conversion mechanisms generate excessive noise that is uncomfortable for the user, and component wear increases dramatically with the increased speed, affecting the product's lifespan.

[0003] Furthermore, the power system of electric toothbrushes, whether using conventional brushed DC motors or brushless electromagnetically driven motors, exhibits output power that is related to the operating voltage and the load. Generally, higher operating voltage results in higher output speed or greater output amplitude, and vice versa. Heavier loads lead to lower speeds or amplitudes. In practical applications, this manifests as insufficient output torque with decreasing battery voltage or a sudden increase in load, showing a significant difference in performance under varying voltage and load conditions, impacting the user experience. To improve the motor's load-bearing capacity, dynamic compensation of the drive power is necessary. This dynamic compensation typically relies on sensors to monitor the motor's operating conditions in real time. Conventional motor condition monitoring sensors include optical gratings, magnetic gratings, Hall effect devices, or electromagnetic induction coils to monitor speed or amplitude data. However, traditional motor condition monitoring technologies are disadvantageous for products with limited installation space and cost constraints.

[0004] Generally, in order to further utilize the monitored swing amplitude data for power compensation, conventional techniques include the following types:

[0005] 1.1 Grating-based displacement detection: Gratings are a traditional displacement detection technique that requires one or more sets of infrared optical light sources and photosensitive receiving components to monitor changes in the grating signal. Due to size limitations, this technique is not suitable for the motor servo requirements mentioned in this invention.

[0006] 1.2 Hall effect detection of magnetic field changes involves fixing a magnet to the motor swing shaft, and having the magnet swing at high speed with the motor swing shaft. A linear Hall effect device is fixed on a bracket to monitor the change in magnetic flux when the magnet moves. The change in magnetic flux can quantify the displacement of the motor swing shaft. High-frequency Hall effect sensors are expensive and do not meet the motor design requirements mentioned in this invention.

[0007] 1.3 Displacement detection by capacitance change: Two metal electrodes are arranged in parallel on the product. One electrode is stationary, and the other moves with the pendulum shaft. The movement of the motor's pendulum shaft changes the capacitance between the two electrodes. By monitoring the change in capacitance, the displacement of the motor's pendulum shaft can be quantified. However, this capacitance-based displacement detection requires a large implementation space and does not meet the motor design requirements mentioned in this invention.

[0008] 1.4 Displacement detection by eddy current change: The sensor has a built-in high-frequency oscillation circuit and emits high-frequency signals. When the object being detected is moving metal, the high-frequency signal will generate eddy currents on the metal surface.

[0009] The distance between the metal plate and the sensor affects the magnitude of the eddy current, which in turn affects the resonant frequency parameter of the oscillation. By monitoring the resonant point of the oscillator in real time, the displacement of the metal displacement plate can be quantified. However, this sensing technology is costly and bulky, and does not meet the motor design requirements mentioned in this invention.

[0010] Therefore, in view of the above-mentioned defects, the designers of this invention, through dedicated research and design, and by integrating years of experience and achievements in related industries, have researched and designed a constant amplitude high-frequency oscillation motor and its control method to overcome the above-mentioned defects. Summary of the Invention

[0011] The purpose of this invention is to provide a constant amplitude high-frequency oscillation motor and its control method, which can overcome the defects of the prior art and solve the problems of high noise and easy wear in actual use. It is particularly suitable for multiple application scenarios such as electric toothbrushes, shavers, hair trimmers, etc., and has a market prospect with stable output torque, simple structure, high durability and low cost.

[0012] To achieve the above objectives, this invention discloses a constant amplitude high-frequency oscillating motor, comprising a motor bracket, an electromagnetic coil, a damping block, a vibrating arm assembly, a front cover, and a magnet. The front cover is located at the front end of the motor bracket, and the magnet is located at the rear end. A damping block is also located on the rear side of the magnet to isolate the vibration of the oscillating motor from the battery at the rear. The invention is characterized by:

[0013] The motor bracket forms an inner cavity to house the vibrating arm assembly. The rear outer edge of the inner cavity is covered with an electromagnetic coil. The vibrating arm assembly includes a swing arm, a rotating shaft, bearings, and a connecting frame. The swing arm is a straight iron swing arm with its rear part located in the electromagnetic coil at the rear of the inner cavity. The front part of the swing arm forms a disc portion with a shaft hole for the rotating shaft to pass through. Both ends of the rotating shaft are rotatably supported on the motor bracket by bearings. The rear end of the connecting frame covers the front part of the swing arm and forms a cylindrical structure to house the disc portion of the swing arm. The front end of the connecting frame is connected to the rear end of the output shaft to transmit the vibration generated by the vibrating arm assembly to the output shaft for output.

[0014] The swing arm, rotating shaft, and output shaft are integrated into a vibrating arm assembly by forming a connecting frame through secondary plastic injection molding. The rotation axis of the rotating shaft is perpendicular to the swing direction of the swing arm, so that the rotating shaft and the swing arm are combined in a cross shape.

[0015] Wherein: both ends of the rotating shaft are provided with shaft shoulders that cooperate with bearings, and the rear end of the output shaft is provided with at least one concave ring so that the output shaft and the connecting frame are stably integrally formed after secondary injection molding, and the at least one concave ring of the output shaft effectively prevents the output from being displaced under the action of external force.

[0016] Specifically, the rear of the swing arm and the inner wall of the motor bracket form a space that allows the swing arm to swing back and forth by 20 degrees without colliding with the motor bracket.

[0017] Wherein: the rear end of the motor bracket forms a stepped portion to accommodate the magnet, thereby maintaining a gap of at least 0.2-0.6mm between the end of the swing arm and the magnet.

[0018] Wherein: the front cover of the motor bracket is covered with a sealing cap to achieve a seal.

[0019] The swing arm is made of stacked silicon steel sheets with high frequency and low eddy current loss.

[0020] Wherein: the magnet is composed of two independent magnets arranged together, or the N and S poles are simultaneously magnetized and polarized on the same plane using a single magnet.

[0021] A control method for a constant amplitude high-frequency oscillating motor as described above, characterized in that: the driving wave voltage is a square wave.

[0022] It includes the following steps:

[0023] Step 1: After the interrupt response, determine whether the 20-pulse interval is met. If yes, proceed to Step 2; otherwise, exit.

[0024] Step 2: Determine if it is a stop cycle. If yes, proceed to Step 3; otherwise, exit.

[0025] Step 3: Start back EMF absorption, determine whether the drive pulse has ended; if yes, proceed to step 4; otherwise, exit.

[0026] Step 4: Collect the battery voltage. If the voltage value is lower than the previous value, proceed to step 5; otherwise, proceed to step 6.

[0027] Step 5: Increment the duty cycle of the drive pulse and then exit;

[0028] Step 6: Is the voltage value greater than the previous acquisition value? If yes, decrease the duty cycle of the drive pulse and exit; otherwise, exit directly.

[0029] As can be seen from the above, the constant amplitude high-frequency oscillation motor and its control method of the present invention have the following effects:

[0030] 1. It can operate effectively in the 140-350Hz range, and uses a high-torque output oscillating motor to replace the traditional DC motor, reducing noise caused by gear sets or connecting rod torque conversion links.

[0031] 2. This invention drives the brush rod using a linkage and lever mechanism, and sets a gap compensation mechanism at the linkage joint and lever fulcrum, which effectively solves the problems of high noise and easy wear in actual use.

[0032] 3. By using correlation quantification to determine the relationship between the swing amplitude and the load, and relying on this variable relationship to change the duty cycle of the drive pulse in real time, the motor output swing amplitude can be enhanced or weakened. By adjusting the duty cycle in real time, the purpose of constant motor output swing amplitude can be achieved.

[0033] 4. By eliminating the need for sensors for amplitude detection, the motor utilizes only the MCU to monitor instantaneous current changes during a specific drive cycle, along with an algorithm, to achieve real-time constant amplitude output. This motor is particularly suitable for various applications such as electric toothbrushes, shavers, and hair trimmers, and boasts a promising market prospect with stable output torque, simple structure, high durability, and low cost.

[0034] 5. Real-time detection of motor operating conditions is achieved, and the operating condition information parsed by the algorithm is used to control the duty cycle of the drive artery to complete real-time dynamic output power compensation, thereby realizing constant swing amplitude or constant torque output of the oscillating motor.

[0035] The details of this invention will become apparent from the following description and the accompanying drawings. Attached Figure Description

[0036] Figure 1 shows a schematic diagram of the constant amplitude high-frequency oscillation motor of the present invention.

[0037] Figure 2 shows a schematic diagram of the internal components of the constant amplitude high-frequency oscillating motor in this invention, displayed in a half-section.

[0038] Figure 3 shows an exploded view of the constant amplitude high-frequency oscillating motor in this invention.

[0039] Figure 4 shows a cross-sectional view of the constant amplitude high-frequency oscillating motor of the present invention.

[0040] Figure 5 shows a cross-sectional view of the constant amplitude high-frequency oscillating motor in this invention from another direction.

[0041] Figure 6 shows a schematic diagram of the structure of the vibration arm assembly of the constant amplitude high-frequency oscillating motor in this invention.

[0042] Figures 7A, 7B, and 7C show schematic diagrams of the constant amplitude high-frequency oscillating motor in this invention under the action of electromagnetic force in three states, where Figures 7A and 7C are oscillating states in opposite directions, and Figure 7B is the stationary state when the current is terminated.

[0043] Figures 8A and 8B show two schematic diagrams illustrating the principles of magnetic poles in this invention.

[0044] Figure 9 shows the voltage signal waveform when the output of an H-bridge is connected to a purely resistive load.

[0045] Figure 10 shows a schematic diagram of the principle of power current acquisition without additional sensors.

[0046] Figure 11 shows the truth diagram of four typical operating states of the H-bridge.

[0047] Figure 12 shows a signal diagram of the H drive bridge connected to a purely resistive load and an inductive motor load.

[0048] Figure 13 shows a schematic diagram of the swing motor exhibiting different swing amplitudes and wave clusters under different loads when the battery terminal voltage is directly measured during operation.

[0049] Figure 14 shows a scatter plot of the relevant data in Figure 13.

[0050] Figure 15 shows a schematic diagram of asynchronous continuous dense voltage sampling.

[0051] Figure 16 shows a schematic diagram of voltage data in synchronous sampling mode.

[0052] Figure 17 shows a schematic diagram illustrating the principle of absorbing back electromotive force by shorting the H-bridge.

[0053] Figure 18 shows a comparison of the current signals before and after the back EMF of the oscillating motor is eliminated.

[0054] Figure 19 shows a block diagram illustrating the process principle of constant amplitude correction technology.

[0055] Figure 20 shows a comparison of the swing angle variation curves with and without compensation when the load changes.

[0056] Figure 21 shows a flowchart of the dynamic servo process for obtaining a constant output swing of the motor in this invention.

[0057] Reference numerals: 21, motor bracket; 22, electromagnetic coil; 23, shock absorber; 24, vibrating arm assembly; 241, swing arm; 242, rotating shaft; 243, bearing; 244, connecting frame; 245, output shaft; 25, front cover; 26, sealing cover; 27, magnet. Detailed Implementation

[0058] Referring to Figures 1 and 2, the constant amplitude high-frequency oscillating motor of the present invention is shown. Figure 1 shows a structural schematic diagram of the constant amplitude high-frequency oscillating motor of the present invention, and Figure 2 shows a schematic diagram of the internal components of the constant amplitude high-frequency oscillating motor of the present invention in a half-section view.

[0059] The constant amplitude high-frequency oscillation motor of the present invention includes a motor bracket 21, an electromagnetic coil 22, a shock absorber 23, a vibration arm assembly 24, a front cover 25, and a magnet 27. As can be seen more clearly from the exploded view shown in FIG3 and the cross-sectional views in FIG4 and FIG5, the front end of the motor bracket 21 is provided with a front cover 25 and the rear end is provided with a magnet 27. The rear side of the magnet 27 is also provided with a shock absorber 23, which can isolate the vibration of the oscillation motor 20 from the battery on the rear side, realize the shock absorption function, and avoid the user's comfort being reduced due to excessive vibration during use.

[0060] The motor bracket 21 has an inner cavity to house the vibrating arm assembly 24. The rear outer edge of the inner cavity is covered with an electromagnetic coil 22. Referring to Figure 6, the vibrating arm assembly 24 includes a swing arm 241, a rotating shaft 242, a bearing 243, and a connecting frame 244. The swing arm 241 is a straight iron swing arm with its rear end located in the electromagnetic coil 22 at the rear of the inner cavity. The front part of the swing arm 241 forms a disc portion with a shaft hole through which the rotating shaft 242 passes. The two ends of the rotating shaft 242 are rotatably supported on the motor bracket 21 by the bearings 243. The rear end of the connecting frame 244 covers the front part of the swing arm 241 and forms a cylindrical structure to house the disc portion of the swing arm 241. The front end of the connecting frame 244 is connected to the rear end of the output shaft 245 to transmit the vibration generated by the vibrating arm assembly 244 to the output shaft 245 for output.

[0061] The swing arm 241, rotating shaft 242, and output shaft 245 are integrally formed by plastic secondary injection molding to create a connecting frame 244, thus constituting a vibrating arm assembly. The rotation axis of the rotating shaft 242 is perpendicular to the swing direction of the swing arm 241. The rotating shaft 243 is preferably located in the rotating shaft hole at approximately 2 / 3 of the length of the swing arm 241, so that the rotating shaft and the swing arm are combined in a cross shape. The two ends of the rotating shaft 242 are provided with shaft shoulders that cooperate with the bearings 243. The rear end of the output shaft 245 is provided with at least one concave ring, so that the output shaft 245 and the connecting frame 244 are stably integrally formed after secondary injection molding. The at least one concave ring of the output shaft 245 can effectively prevent displacement of the output shaft under external force.

[0062] Therefore, as a power conversion device that converts electromagnetic energy into mechanical energy, the oscillating motor ultimately outputs a driving torque that is 2-5 times that of a traditional DC motor of the same volume under the same working conditions under the same power consumption conditions, in order to meet the high-frequency oscillation power requirements of electric toothbrushes.

[0063] Referring to Figures 7A, 7B, and 7C, the vibrating arm assembly is housed within the cavity of the device. A space is formed between the rear of the swing arm 241 and the inner wall of the motor bracket 21, allowing the swing arm 241 to swing back and forth by 20 degrees without colliding with the motor bracket. The rear end of the motor bracket 21 forms a stepped portion to accommodate the magnet 27, thereby maintaining a gap of at least 0.2-0.6 mm between the end of the swing arm 241 and the magnet. Thus, the magnet 27 at the tail end can induce a magnetic force on the tail end of the iron swing arm, but there is no physical contact.

[0064] Two magnets are arranged in parallel at the tail of the support, with their magnetized surfaces facing the swing arm. When the two magnets are combined, they are of the same polarity but have different names.

[0065] The front cover 25 of the motor bracket 21 is covered with a sealing cover 26 to achieve a seal. The front cover strengthens the stability of the bearings at both ends of the shaft and provides a limit for the sealing cover.

[0066] The process by which the electromagnetic force of the constant amplitude high-frequency oscillating motor proposed in this invention is converted into oscillating mechanical energy is as follows:

[0067] 1. Connect a square wave power current with alternating positive and negative polarities to the electromagnetic coil.

[0068] 2. As shown in Figure 7A, assuming that during the positive half-cycle of the square wave, since the electromagnetic coil has an iron swing arm built inside, and the axis of the swing arm is in the same direction as the axis of the electromagnetic coil, the swing arm will be polarized and magnetized under the action of the electromagnetic field. Assuming that the swing arm closest to the magnetic pole is polarized to the S pole at this moment, under the principle of like poles repelling and unlike poles attracting, the swing arm of the vibrating arm assembly will swing in the direction of D1.

[0069] 3. As shown in Figure 7C, when the square wave current switches to the negative half-cycle, the polarity of the electromagnetic coil is reversed, and the current acting on the electromagnetic coil is opposite to that of the positive half-cycle. The magnetic pole induced by the swing arm changes to the N pole. Similarly, under the action of the new electromagnetic force, the swing arm of the vibrating arm assembly will switch from the D1 direction to the D2 direction.

[0070] 4. After the positive and negative half-cycles of current switching are completed, the swing of the motor's vibrating arm assembly constitutes a complete vibration cycle. The swing frequency of the vibrating arm assembly depends on the frequency of the square wave current of the drive coil. In this embodiment of the invention, the electromagnetic coil preferably operates at 140Hz-250Hz. The strength of the swing angle of the vibrating arm assembly can be adjusted by the duty cycle of the square wave. The swing angle is proportional to the size of the duty cycle.

[0071] The swing arm 241 is made of ferromagnetic material. Because the working frequency can be up to 250Hz, the swing arm 241 is made of stacked silicon steel sheets with high frequency and low eddy current loss.

[0072] As shown in Figure 8A, the magnet 27 of this invention can be composed of two independent magnets M1 arranged to form magnetic poles, or as shown in Figure 8B, it can be constructed using a coplanar multi-pole magnetization process, employing only one magnet M2 to simultaneously magnetize and polarize the N and S poles on the same plane. The N and S poles being aligned with the polarities of the two magnets is sufficient to meet the requirements of this invention.

[0073] Among them, the sensorless synchronous drive pulse detection battery voltage technology is adopted. It relies on a specific drive pulse cycle to monitor the change of drive current caused by the change of motor dynamic impedance. Combined with the corresponding algorithm, the drive power is compensated in real time based on the monitored motor operating conditions to achieve constant swing output.

[0074] This invention also discloses a control method for a constant-amplitude high-frequency oscillating motor as described above. In one embodiment of the oscillating motor, the typical driving wave voltage shape is a square wave, and the frequency of the square wave is consistent with the output oscillation frequency. Theoretically, when the motor is at full power output under constant voltage conditions, the duty cycle of the square wave should be 100%. In practical applications, the most basic driving power device is an H-bridge consisting of four FETs. The H-bridge switches between positive and negative voltages at high speed according to the input signal. Because there is a response time difference in FET switching, if switching is performed at a 100% duty cycle, all four FETs of the H-bridge will conduct simultaneously, causing a short circuit inside the H-bridge and damaging the H-bridge drive. This fastest response interval is usually called the dead zone of the H-bridge drive. Therefore, the H-bridge should avoid operating in the dead zone, and the power supply to the motor should be stopped in this interval. Considering the dead zone, the maximum duty cycle of the square wave is usually 98% to 99%, not 100%.

[0075] If the duty cycle of the pulse is reduced in the opposite direction, the effective power of the drive will decrease in the opposite direction, and the swing amplitude of the oscillating motor will decrease accordingly. The mechanism of changing the output power by adjusting the duty cycle of the pulse serves as the theoretical basis for the output rate compensation of the oscillating motor mentioned in this invention.

[0076] Figure 9 shows a typical voltage signal waveform when the output of an H-bridge is connected to a purely resistive load. In the figure: S1 is the effective working pulse of the positive half-cycle, S2 is the effective working pulse of the negative half-cycle, t12 and t22 are the working stop cycles of the positive and negative half-cycles, respectively, which include the necessary dead zone control time and the stop time for adjusting the duty cycle of the entire pulse. t is a complete drive cycle, t = S1 + S2 + t12 + t22; assuming S1 = S2 and t12 = t22, the positive and negative half-cycles are completely symmetrical; the duty cycle is Duty = S1 / (t12 + S1) × 100% or Duty = S2 / (t22 + S2) × 100%. In actual control, the power control of the drive can be achieved by synchronously adjusting the proportion of t12 and t22 in the entire pulse t, i.e., the duty cycle parameter Duty. Obviously, the larger the proportion of t12 and t22, the smaller the output power. Controlling the output power by adjusting the duty cycle ratio is the theoretical basis of the motor control technology of this invention.

[0077] Before discussing how to implement the constant amplitude control theory of the motor mentioned in this invention, we will first explain the principle and method of acquiring power current without additional sensors. As shown in Figure 10, a schematic diagram of the principle of acquiring power current without additional sensors is displayed. In this diagram, BT represents the battery pack, V is the standard battery, and R0 is the internal resistance of the battery pack; MCU is the microprocessor of the circuit control unit, which contains an analog-to-digital converter labeled ADC and a reference voltage reference source for the ADC labeled Vref; S1 to S4 are the output drive signal ports of the MCU dedicated to the H-bridge; H is the H power drive bridge composed of two pairs of complementary FETs; M is the oscillating motor involved in this invention; and I is the power current.

[0078] Figure 11 shows the true values ​​for four typical operating states of the H-bridge.

[0079] Among them, the current sampling required for the constant amplitude technology involved in this invention has two key aspects:

[0080] 1. Utilizing the internal resistance R0 of the battery pack, during power drive, the changing power current I will inevitably generate a changing voltage drop Vdp in R0. The change in load current can be reflected by detecting Vdp through the MCU control unit, i.e., Vdp = R0 XI.

[0081] 2. To simplify the hardware design, a microprocessor with a built-in analog-to-digital converter (ADC) and a voltage reference source (Vref) is selected. This allows the power current change to be calculated directly without the need for additional external designs.

[0082] Unless otherwise specified, the power current change detection discussed in this article is based on the method of detecting the change in voltage drop Vdp of R0.

[0083] The following sections will further explain the implementation method and process of constant amplitude compensation in two parts.

[0084] The signals from a purely resistive load and an inductive motor load connected to the H-drive bridge exhibit significant differences, as shown in Figure 12. In the figure, the solid line CV1 represents the waveform of a purely resistive load, while the dashed line represents the waveform of a oscillating motor with an inductive load. The obvious difference between these two sets of waveforms is the presence of a peak ringing (marked as D) in each working pulse. Furthermore, under the influence of the inductive load, the horizontal line of a standard rectangular square wave changes to a slope line from the starting point a to the ending point b of each effective working waveform.

[0085] When the motor is connected to the drive end, the square wave exhibits significant overshoot and ringing. This is mainly due to the stopping cycle (dead zone cycle + power adjustment cycle), when power supply to the motor coil stops. Since the coil is an inductive load, it generates a back electromotive force (EMF). Additionally, the swing arm continues to cut the magnetic lines of force generated by the magnet due to inertia, creating a variable impedance to the coil. The superposition of the coil's back EMF and the variable impedance on the power supply directly affects the smoothness of the square wave's rising edge and pulse width.

[0086] After the coil is de-energized, the swing arm continues to oscillate due to inertia. Assuming the oscillation frequency remains constant, the larger the amplitude, the greater the velocity at which the magnetized swing arm cuts the magnetic field lines, and the greater the impact on the variable impedance generated by the coil. Clearly, if the instantaneous current related to the variable impedance can be measured, the current oscillation linear velocity of the swing arm can be mapped, i.e., the relative change in the current output swing. This idea is the most important theoretical basis for the real-time amplitude measurement involved in the constant amplitude drive technology mentioned in this invention.

[0087] To reduce the impact of stray electromagnetic interference on signal detection, the swing correlation data detection mentioned in this invention is not located at the motor drive output end, but rather the instantaneous voltage change at the battery terminal is measured directly. This voltage change has a corresponding mapping relationship with the current change at the motor drive end.

[0088] Figure 13 shows the battery terminal voltage measured directly during operation. Under different loads, the oscillating motor exhibits different oscillation amplitudes and waveforms. The solid curve CV1 in the figure represents the waveform under no-load conditions, while the dashed curves CV2, CV3, CV4, and CV5 represent the waveforms exhibited under increasing loads. It can be observed that the battery terminal voltage changes with the load at a certain time interval of each drive pulse. As shown in the attached figure, the correlation between motor load and voltage is clearly observed in the t1-t2 interval; the heavier the load, the higher the voltage. The summarized pattern is:

[0089] Load: CV5 > CV4 > CV3 > CV2 > CV1;

[0090] Pulse end voltage: V5>V4>V3>V2>V1.

[0091] Figure 14 shows the data as a scatter plot. In the figure, the V-axis is the battery terminal voltage, and the D-axis is the swing angle of the pendulum. The heavier the load, the smaller the swing angle of the pendulum.

[0092] V5 to V1 represent 5 sampling points, and curve a is the curve formed by connecting the actual sampling points in series. The attached figure clearly shows a strong correlation between the voltage at the sampling points and the angle of oscillation under different loads. To simplify the computational load on the microprocessor, the above sampling data can be fitted with a straight line b using the least squares method.

[0093] The instantaneous voltage change U at the battery terminals is affected by two important factors: U = Ub + Ur. Ub is the back electromotive force generated during the motor's power-off and stop cycle, while Ur is the change in the dynamic inductive reactance of the coil caused by the change in the swing amplitude of the vibrating arm. This change in dynamic inductive reactance directly affects the rate of current conduction in the coil, essentially creating a changing impedance. Ultimately, this change in coil impedance affects the performance of the rising edge of each pulse at the motor coil terminals.

[0094] Therefore, as long as the voltage change component caused by impedance change at the rising edge of each pulse can be effectively separated, the current motor swing data can be quantified.

[0095] To better separate the changing impedance of the motor coil, appropriate and accurate current sampling points are crucial. As can be seen from the waveform, unlike conventional sampling methods, the conventional approach for typical DC motors ignores pulse synchronization information and uses continuous, equidistant, dense sampling. The longer the sampling period, the more stable the weighted average, thus better reflecting the relationship between voltage and load. However, this asynchronous averaging method has proven ineffective for brushless motors driven by pulse commutation. The voltage results obtained from continuous sampling without pulse synchronization show no significant correlation with load changes.

[0096] Figure 15 illustrates the performance of asynchronous continuous dense voltage sampling in a brushless motor: In the figure: V-axis: voltage scalar, T-axis: time scalar, S1~Sn is the timing sequence of asynchronous continuous sampling, t2 is the sampling period, P1~pn is the voltage change periodic signal observed at the battery terminal. Obviously, this period is phase-related and synchronous with the motor drive pulse, t1 is the motor drive pulse period, and D1~Dn is the sampled voltage value.

[0097] As shown in the figure, if t1 and t2 are out of sync, the sampling positions of D1 and D5 differ significantly from the pulse start and end positions. D1 is closer to the beginning of pulse P1, while D5 is closer to the end of pulse P3, resulting in a large difference between these two sampled values. Therefore, a weighted average method can be used to average the data: Avg = (D1 + D2 + Dn…) / n…. However, the average value Avg fails to accurately capture the data that correctly correlates the load and voltage. Therefore, traditional asynchronous voltage sampling is not suitable for the oscillating motor operating conditions mentioned in this invention.

[0098] Figure 16 illustrates the performance of voltage data in the synchronous sampling method: In the figure: V-axis: voltage scalar, T-axis: time scalar, S1~Sn is the timing sequence of asynchronous continuous sampling, t2 is the sampling period, P1~pn is the voltage change periodic signal observed at the battery terminal, which is obviously phase-dependent and synchronous with the pulse. t1 is the motor drive pulse period, and D1~Dn are the sampled voltage values.

[0099] As can be observed from Figure 16, if t1 and t2 are synchronized, the sampling positions of D1, D2, D3...Dn are consistent with the pulse start and stop positions. Assuming that the weighted average method is used to average the data: that is, Avg=(D1+D2+Dn…) / n…, the average value Avg can correctly capture the data that correctly correlates the load and voltage. Therefore, synchronous voltage sampling is the preferred current sampling scheme for the oscillating motor mentioned in this invention.

[0100] Based on the data in the two figures above, the difference between the traditional simple weighted average current sampling mode and synchronous sampling is clearly explained. The oscillating motor, in a broad sense, belongs to the category of brushless motors. Both are driven by power pulses that switch between positive and negative polarity pulses at high frequency. The sampling mode that is synchronized with the pulse phase must be used to analyze the current information related to the load.

[0101] Even after synchronous sampling, additional technical means are still needed to filter out the back electromotive force signal generated by unnecessary coils that affect the load current performance in order to further improve signal quality.

[0102] The overcharge amount at the rising edge of the pulse contains not only information about the coil's dynamic impedance but also the back electromotive force (EMF) generated after the coil is de-energized. If the overcharge information of each pulse rising edge is used directly to quantize the swing amplitude relationship without considering the influence of the back EMF on signal superposition, the presence of the back EMF will more or less reduce the accuracy of quantization. To eliminate the influence of the back EMF on the overcharge of each pulse rising edge, the motor coil can be momentarily short-circuited using an H-bridge during each drive stop cycle, allowing the back EMF to be released quickly. Examples demonstrate that eliminating the back EMF enables more sensitive monitoring of motor swing amplitude changes and improves the signal-to-noise ratio.

[0103] Therefore, Figure 17 is a schematic diagram of the principle of short-circuited H-bridge absorbing back EMF. In the figure: F1 to F4 are two pairs of complementary NP-channel FETs forming an H-bridge to drive the oscillating motor. M is the oscillating motor. Before the motor current is detected and the drive power is disconnected, the inputs of S1 and S2 are set to high level, and F1 and F2 enter the cutoff state. The inputs of S3 and S4 are also high level, and F3 and F4 are turned on. After F3 and F4 are turned on, F3, F4 and M form a loop, which short-circuits the back EMF generated at both ends of the motor M, generating a short-circuit current loop C. The back EMF is converted into heat energy and dissipated on the motor coil.

[0104] Once the back electromotive force is absorbed, S3 and S4 switch to high level and enter the cutoff state, starting the MCU's ADC conversion for current detection.

[0105] Figure 18 shows a comparison of current signals before and after eliminating back EMF in the oscillating motor. In the figure: V axis: voltage scalar, T axis: time scalar, P1 to P3 show three sets of pulse period signals, CV1 solid curve is the voltage curve after eliminating back EMF using short-circuit technology, CV2 dashed curve is the voltage curve affected by back EMF, Ts is the important area containing load change information, C is the ringing peak signal that appears when back EMF is not eliminated by short-circuiting, and a is the area with a large influence of back EMF.

[0106] Since the shadowed area caused by the ringing peak of the signal due to the back electromotive force in the a region has a significant impact on the effective load signal in the Ts interval, absorbing the ringing peak using technical means is of positive significance for analyzing the load signal.

[0107] Short-circuiting to eliminate back EMF is beneficial for analyzing changes in the dynamic impedance of the coil, but it can also have a negative impact on the motor. When the coil current is short-circuited, heat will be generated in the coil, causing the coil operating temperature to rise. Whether to use back EMF elimination technology or choose a reasonable short-circuit sequence can be decided based on the actual application.

[0108] Once valid amplitude quantization data is obtained, this data can be used to adjust the duty cycle of the drive pulse in real time. When the amplitude is lower than the set value, the pulse duty cycle is continuously increased to increase the drive power and improve the amplitude; conversely, the duty cycle is continuously decreased to reduce the drive pulse power and decrease the amplitude. By dynamically monitoring the amplitude value and dynamically adjusting the pulse drive power in real time using the methods discussed above, a stable output amplitude can be obtained under load variations.

[0109] Figure 19 is a block diagram illustrating the process principle of the constant amplitude correction technology involved in this invention. In specific implementations, besides addressing the battery voltage change related to the swing amplitude, it is also necessary to correctly select appropriate sampling and adjustment frequencies. This is because ADC data acquisition and processing consumes resources, and overly dense data sampling can interfere with the stability of the driving pulse phase, causing phase jitter, resulting in irregular oscillations and abnormal noise from the motor swing shaft. The density of the adjustment pulse duty cycle also needs to be appropriate, as the motor swing shaft has rotational inertia and response time domain requirements. Overly dense adjustments will weaken the useful amplitude information being analyzed, leading to overshoot and overshoot oscillations, making normal control impossible. Overly sparse adjustments will result in sluggish control response and unsatisfactory compensation effects. Generally, the following factors should be considered in practical control applications:

[0110] 1. Synchronization point with motor signal: The implementation example proves that sampling data is most stable and has a high signal-to-noise ratio when the pulse is about to end.

[0111] 2. Back EMF Activation Duration and Density: Back EMF absorption should not be activated for every pulse. It should only be enabled before detecting the battery voltage and immediately disabled after detection. Otherwise, a large amount of heat will be dissipated into the motor coils, causing the motor operating temperature to rise sharply. Similarly, the absorption duration is also a key point in controlling heat, and the specific duration should be determined based on actual conditions and experimental results.

[0112] 3. Battery voltage sampling: Sampling should not be performed for every pulse. In the example sub-test, sampling once every 20 pulses is optimal. Overly frequent sampling will cause phase jitter and abnormal noise in the motor.

[0113] 4. Adjusting the frequency of the motor drive pulse duty cycle: This also needs to be reasonable. Too frequent corrections will result in overshoot oscillation, while too sparse compensation will lead to sluggish response and unstable swing after load changes.

[0114] Therefore, the control method includes the following steps:

[0115] Step 1: Synchronize the output pulse (which can be the square wave pulse mentioned above);

[0116] Step 2: Initiate back electromotive force absorption;

[0117] Step 3: Synchronously collect battery voltage;

[0118] Step 4: Analyze load-related variables;

[0119] Step 5: Calculate the correction amount;

[0120] Step 6: After correcting the drive duty cycle, return to Step 1.

[0121] Figure 21 shows a flowchart of the dynamic servo process for obtaining a constant output swing of the motor, as mentioned in this invention.

[0122] It includes the following steps:

[0123] Step 1: After the interrupt response, determine whether the 20-pulse interval is met. If yes, proceed to Step 2; otherwise, exit.

[0124] Step 2: Determine if it is a stop cycle. If yes, proceed to Step 3; otherwise, exit.

[0125] Step 3: Start back EMF absorption, determine whether the drive pulse has ended; if yes, proceed to step 4; otherwise, exit.

[0126] Step 4: Collect the battery voltage. If the voltage value is lower than the previous value, proceed to step 5; otherwise, proceed to step 6.

[0127] Step 5: Increment the duty cycle of the drive pulse and then exit;

[0128] Step 6: Is the voltage value greater than the previous acquisition value? If yes, decrease the duty cycle of the drive pulse and exit; otherwise, exit directly.

[0129] The above exit method directly exits the interrupt response.

[0130] In embodiments of the present invention, after system initialization, the initial pulse duty cycle without compensation is preset to 45%, and the maximum compensation is 98%.

[0131] Figure 20 shows a comparison of the swing angle variation curves with and without compensation under varying loads. The vertical axis represents the swing angle exhibited by the swing axis, and the horizontal axis represents the force applied to the swing axis. Curve CV1 represents the output performance without compensation, and CV2 represents the performance after real-time dynamic compensation. As can be seen from the figure, the swing amplitude's ability to withstand load changes is significantly improved after compensation.

[0132] It is obvious that the above description and account are merely illustrative and not intended to limit the disclosure, application, or use of this invention. Although embodiments have been described and illustrated in the accompanying drawings, the invention is not limited to the specific examples exemplified by the drawings and described in the embodiments as currently considered the best mode for carrying out the teachings of the invention. The scope of the invention will include any embodiments falling within the foregoing description and the appended claims.

Claims

1. A constant amplitude high-frequency oscillating motor, comprising a motor bracket, an electromagnetic coil, a damping block, a vibrating arm assembly, a front cover, and a magnet, wherein the front cover is provided at the front end of the motor bracket, and the magnet is provided at the rear end; a damping block is also provided on the rear side of the magnet to isolate the vibration of the oscillating motor from the battery at the rear, characterized in that: The motor bracket forms an inner cavity to house the vibrating arm assembly. The rear outer edge of the inner cavity is covered with an electromagnetic coil. The vibrating arm assembly includes a swing arm, a rotating shaft, bearings, and a connecting frame. The swing arm is a straight iron swing arm with its rear part located in the electromagnetic coil at the rear of the inner cavity. The front part of the swing arm forms a disc portion with a shaft hole for the rotating shaft to pass through. Both ends of the rotating shaft are rotatably supported on the motor bracket by bearings. The rear end of the connecting frame covers the front part of the swing arm and forms a cylindrical structure to house the disc portion of the swing arm. The front end of the connecting frame is connected to the rear end of the output shaft to transmit the vibration generated by the vibrating arm assembly to the output shaft for output.

2. The constant amplitude high-frequency oscillating motor as described in claim 1, characterized in that: The swing arm, rotating shaft, and output shaft are integrated into a vibrating arm assembly by forming a connecting frame through secondary plastic injection molding. The rotation axis of the rotating shaft is perpendicular to the swing direction of the swing arm, so that the rotating shaft and the swing arm are combined in a cross shape.

3. The constant amplitude high-frequency oscillating motor as described in claim 2, characterized in that: The two ends of the rotating shaft are provided with shaft shoulders that cooperate with the bearings, and the rear end of the output shaft is provided with at least one concave ring so that the output shaft and the connecting frame are stably integrally formed after secondary injection molding. The at least one concave ring of the output shaft effectively prevents the output from being displaced under the action of external force.

4. The constant amplitude high-frequency oscillating motor as described in claim 1, characterized in that: The rear of the swing arm and the inner wall of the motor bracket form a space that allows the swing arm to swing back and forth by 20 degrees without colliding with the motor bracket.

5. The constant amplitude high-frequency oscillating motor as described in claim 1, characterized in that: The rear end of the motor bracket forms a stepped portion to accommodate the magnet, thereby maintaining a gap of at least 0.2-0.6 mm between the end of the swing arm and the magnet.

6. The constant amplitude high-frequency oscillating motor as described in claim 1, characterized in that: The front cover of the motor bracket is equipped with a sealing cap to achieve a seal.

7. The constant amplitude high-frequency oscillating motor as described in claim 1, characterized in that: The swing arm is made of stacked silicon steel sheets with high frequency and low eddy current loss.

8. The constant amplitude high-frequency oscillating motor as described in claim 1, characterized in that: The magnet can be composed of two independent magnets arranged together, or a single magnet can be used to simultaneously magnetize and polarize the N and S poles on the same plane.

9. A control method for a constant amplitude high-frequency oscillating motor as described in any one of claims 1-8, characterized in that: The driving wave voltage is a square wave.

10. The control method for a constant amplitude high-frequency oscillating motor as described in claim 9, characterized in that... It includes the following steps: Step 1: After the interrupt response, determine whether the 20-pulse interval is met. If yes, proceed to Step 2; otherwise, exit. Step 2: Determine if it is a stop cycle. If yes, proceed to Step 3; otherwise, exit. Step 3: Start back EMF absorption, determine whether the drive pulse has ended; if yes, proceed to step 4; otherwise, exit. Step 4: Collect the battery voltage. If the voltage value is lower than the previous value, proceed to step 5; otherwise, proceed to step 6. Step 5: Increment the duty cycle of the drive pulse and then exit; Step 6: Is the voltage value greater than the previous acquisition value? If yes, decrease the duty cycle of the drive pulse and exit; otherwise, exit directly.

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