Constant-amplitude high-frequency shimmy motor

Abstract

A constant-amplitude high-frequency shimmy motor comprises a motor support, an electromagnetic coil, a damping block, a vibrating arm assembly, a front cover and a magnet, the front cover is arranged at the front end of the motor support, the magnet is arranged at the rear end of the motor support, an inner cavity is formed in the motor support to contain the vibrating arm assembly, the outer edge of the rear portion of the inner cavity is wrapped with the electromagnetic coil, and the damping block is arranged in the inner cavity. The vibrating 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 part is formed in the front portion of the swing arm, and the disc part is provided with a shaft hole for the rotating shaft to penetrate through; the rear end of the connecting frame wraps the front portion of the swing arm and forms a cylinder structure for containing the disc portion of the swing arm, and the front end of the connecting frame is connected to the rear end of the output shaft to output power. Therefore, according to the utility model, the defects in the prior art can be overcome, the problems of large noise and easy abrasion in actual use are solved, and the power output is smoother and more reliable.

Description

Technical Field

[0001] The utility model relates to the technical field of motors for electric toothbrushes, and particularly relates to a constant-amplitude high-frequency swing-vibration motor suitable for an electric toothbrush. Background Art

[0002] At present, DC motors are commonly used to drive electric toothbrushes. The maximum operating speed of an electric toothbrush driven by a DC motor is less than 133 Hz, and a gear set or a lever linkage is required to complete torque conversion. Otherwise, the direct drive output torque is too small to meet the power demand for cleaning. For example, in order to enable the toothbrush head to effectively operate at 140 - 350 Hz and for the torque conversion of the gear set, the rotational speed of the DC motor must be far higher than 2 - 4 times the output of the brush disc. Under this condition, a conventional power conversion mechanism will generate high working noise that makes users uncomfortable, and component wear will also increase sharply due to the increase in rotational speed, affecting the product life.

[0003] Moreover, in the power system of an electric toothbrush, whether it is a conventional brushed DC motor or a brushless electromagnetic force-driven motor, the output power is related to the working voltage and the load. Most of them have a higher output rotational speed or a larger output swing amplitude as the working voltage is higher, and vice versa, the rotational speed or swing amplitude will become lower. The heavier the load, the lower the rotational speed or swing amplitude. In actual product applications, the output torque will be insufficient as the battery voltage decreases or the load suddenly increases, and there is an obvious drop in the load capacity performance at different voltages, affecting the user experience. In order to improve the load resistance ability of the motor, it is necessary to dynamically compensate the driving power. In order to achieve dynamic compensation, generally, it is necessary to rely on sensors to monitor the motor operating conditions in real time. Conventional motor operating condition monitoring sensors include grating, magnetic grating, Hall devices, or electromagnetic induction coils to monitor rotational speed or swing amplitude data. The motor operating condition monitoring technology of traditional methods is not beneficial to products with requirements for installation space and product cost.

[0004] Generally, in order to be able to monitor the swing amplitude data and further use the data to compensate the power, the conventional technologies are of the following types:

[0005] 1.1 Grating detects displacement. Grating is a traditional technology for detecting displacement, and one or more groups of infrared optical light sources and photosensitive receiving components are required to monitor the change signals of the grating. Due to the volume limitation of this technology, it is not suitable for the motor servo requirements mentioned in the present utility model.

[0006] 1.2 Hall detects the change of magnetic field. A magnet is fixed on the motor swing shaft, and the magnet swings at a high speed with the motor swing shaft. A linear Hall device is fixed on the bracket to monitor the change of magnetic flux when the magnet moves. The change of magnetic flux can quantify the displacement of the motor swing shaft. High-frequency Hall sensors are costly and do not meet the motor design requirements mentioned in the present utility model.

[0007] 1.3 Detecting displacement by capacitance change. Two metal electrodes are arranged in parallel on the product. One electrode is a stationary electrode, and the other is an electrode that moves with the swing shaft. When the swing shaft of the motor moves, the capacitance between the two electrodes can be changed accordingly. By monitoring the change in the capacitance of the electrodes, the displacement of the motor swing shaft can be quantified. Since the capacitance method for detecting displacement requires a large implementation space, it does not meet the motor design requirements mentioned in this utility model either.

[0008] 1.4 Detecting displacement by eddy current change. The sensor is internally provided with a high-frequency oscillation circuit and emits high-frequency signals externally. When the object to be detected is a moving metal, eddy currents will be generated on the metal surface due to the high-frequency signals in the metal.

[0009] The distance between the metal sheet and the sensor will affect the magnitude of the eddy current, and further affect the resonant frequency parameter of the oscillation. By real-time monitoring the resonant point of the oscillator, the displacement of the metal displacement sheet can be quantified. This sensing technology has a high cost and a large volume, and also does not meet the motor design requirements mentioned in this utility model.

[0010] Therefore, in view of the above defects, the designer of this utility model, through painstaking research and design, and integrating the experience and achievements of being engaged in related industries for many years, has researched and designed a constant-amplitude high-frequency oscillating motor to overcome the above defects. Summary of the Utility Model

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

[0012] To achieve the above purpose, this utility model discloses a constant-amplitude high-frequency oscillating motor, which includes a motor bracket, an electromagnetic coil, a shock-absorbing block, a vibration arm assembly, a front cover, and a magnet. The front end of the motor bracket is provided with a front cover, and the rear end is provided with a magnet. A shock-absorbing block is also provided at the rear side of the magnet so as to isolate the vibration of the oscillating motor from the battery at the rear side. Its characteristics are as follows:

[0013] An inner cavity is formed in the motor bracket to accommodate the vibration arm assembly. The outer edge of the rear part of the inner cavity is covered with an electromagnetic coil. The vibration arm assembly includes a swing arm, a rotating shaft, a bearing, and a connecting frame. The rear part of the swing arm is located in the electromagnetic coil at the rear part of the inner cavity. The front part of the swing arm forms a disc part, and the disc part is provided with a shaft hole for the rotating shaft to pass through. The two ends of the rotating shaft are rotatably supported on the motor bracket through bearings. The rear end of the connecting frame is covered on the front part of the swing arm and forms a cylindrical structure for accommodating the disc part 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 vibration arm assembly to the output shaft for output.

[0014] Among them: the swing arm, the rotating shaft and the output shaft are integrally formed by the method of secondary plastic injection molding to form a connecting frame and are embedded together to form a vibration arm assembly.

[0015] Among them: the swing arm is a linear iron swing arm, and the axis of rotation of the rotating shaft is perpendicular to the swinging direction of the swing arm, so that the rotating shaft and the swing arm are cross-shaped after combination.

[0016] Among them: both ends of the rotating shaft are provided with shoulders for cooperating with bearings, and at least one concave ring is provided at the rear end of the output shaft, so that the output shaft and the connecting frame are firmly integrally formed after secondary injection molding and effectively prevent the output from generating displacement under the action of external force.

[0017] Among them: a space is formed between the rear part of the swing arm and the inner wall of the motor bracket to allow the swing arm to swing back and forth by 20 degrees without collision with the motor bracket.

[0018] Among them: a stepped portion for accommodating the magnet is formed at the rear end of the motor bracket, so that a gap of 0.2 - 0.6 mm is maintained between the end of the swing arm and the magnet.

[0019] Among them: a sealing cover covers the front cover at the front end of the motor bracket to achieve sealing.

[0020] Among them: the swing arm is stacked by silicon steel sheets with high frequency and low eddy current loss.

[0021] Among them: the magnet is formed by arranging two independent magnets.

[0022] Among them: the magnet magnetizes and polarizes the N and S poles simultaneously in the same plane and uses one magnet.

[0023] It can be seen from the above that the constant amplitude high-frequency swing shock motor of the present invention has the following effects:

[0024] 1. It can effectively work at 140 - 350 Hz, uses a swing shock motor with high torque output to replace the traditional DC motor, and reduces the noise caused by the torque conversion links of the gear set or the connecting rod.

[0025] 2. The present invention drives the brush rod in the manner of a connecting rod and a lever, and a clearance compensation mechanism is arranged at the connecting rod joint point and the lever fulcrum, effectively solving the problems of large noise and easy wear in actual use.

[0026] 3. Utilize the correlation to quantify the relationship between the swing amplitude and the load, rely on this variable relationship to change the duty cycle of the driving pulse in real time to enhance or weaken the swing amplitude of the motor output, and achieve the purpose of constant output swing amplitude of the motor by adjusting the duty cycle in real time.

[0027] 4. Reduce the sensors for swing detection, and only use the MCU to monitor the instantaneous current change in a certain driving cycle and cooperate with the algorithm to achieve real-time constant amplitude output. This motor is especially suitable for multiple application scenarios such as electric toothbrushes, shavers, hair trimmers... etc., and has the market prospects of stable output torque, simple structure, high durability, and low cost.

[0028] 5. Realize the real-time detection of the motor working conditions, and use the working condition information analyzed by the algorithm to complete the real-time dynamic output power compensation by controlling the duty cycle of the driving artery, so as to achieve the constant swing amplitude or constant torque output of the swing shock motor.

[0029] The detailed content of the present utility model can be obtained through the following description and the accompanying drawings. Brief Description of the Drawings

[0030] Figure 1 Shows a schematic structural diagram of the constant amplitude high-frequency swing shock motor of the present utility model.

[0031] Figure 2 Shows a schematic diagram of the internal components of the constant amplitude high-frequency swing shock motor of the present utility model shown in a semi-sectional view.

[0032] Figure 3 Shows an exploded schematic diagram of the constant amplitude high-frequency swing shock motor of the present utility model.

[0033] Figure 4 Shows a sectional view of the constant amplitude high-frequency swing shock motor of the present utility model.

[0034] Figure 5 Shows a sectional view of the constant amplitude high-frequency swing shock motor of the present utility model in another direction.

[0035] Figure 6 Shows a schematic structural diagram of the vibration arm assembly of the constant amplitude high-frequency swing shock motor of the present utility model.

[0036] Figure 7A 、 Figure 7B and Figure 7C Show schematic diagrams of three states of the constant amplitude high-frequency swing shock motor of the present utility model under the action of electromagnetic force, where Figure 7A and Figure 7C are in the reverse swing states, Figure 7B is the stationary state with the current terminated.

[0037] Figure 8A and Figure 8B Show two schematic diagrams of the principles of the magnetic poles of the present utility model.

[0038] Figure 9 Shows a waveform diagram of the voltage signal at the output end of a typical H-bridge connected to a pure resistive load.

[0039] Figure 10 It shows a schematic diagram of the acquisition principle of power current without additional sensor devices.

[0040] Figure 11 It shows a signal schematic diagram of the H drive bridge accessing a pure resistive load and an inductive motor load.

[0041] Figure 12 It shows a schematic diagram that when directly measuring the battery terminal voltage during operation, the swing motor exhibits different swing amplitudes and wave clusters under different load effects.

[0042] Figure 13 It shows Figure 13 a scatter plot of relevant data in

[0043] Figure 14 It shows a schematic diagram of asynchronous continuous dense voltage sampling.

[0044] Figure 15 It shows a schematic diagram of voltage data in the synchronous sampling method.

[0045] Figure 16 It shows a schematic diagram of the principle of short - circuiting the H - bridge to absorb the back electromotive force.

[0046] Figure 17 It shows a comparison chart of current signals of the swing motor before and after eliminating the back electromotive force.

[0047] Figure 18 It shows a process principle block diagram of the constant - amplitude correction technology

[0048] Figure 19 It shows a comparison chart of the change curves of the swing angles with and without compensation when the load changes.

[0049] Figure 20 It shows a signal processing flow chart of the dynamic servo process for obtaining a constant output swing amplitude of the motor in the present utility model.

[0050] Reference numerals:

[0051] 21. Motor bracket; 22. Electromagnetic coil; 23. Shock absorber; 24. Vibration 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 manners

[0052] See Figure 1 and 2 which shows the constant - amplitude high - frequency swing motor of the present utility model, where Figure 1 It shows a structural schematic diagram of the constant - amplitude high - frequency swing motor of the present utility model, Figure 2Shows a schematic diagram of the internal components of the constant-amplitude high-frequency oscillating motor in the present utility model shown in a half-sectioned manner.

[0053] Among them, the constant-amplitude high-frequency oscillating motor of the present utility model includes a motor bracket 21, an electromagnetic coil 22, a shock-absorbing block 23, a vibrating arm assembly 24, a front cover 25, and a magnet 27. As shown in the exploded schematic diagram and Figure 3 the cross-sectional view shown in Figure 4 and Figure 5 can be seen more clearly. 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. A shock-absorbing block 23 is also provided at the rear side of the magnet 27, so that the vibration of the oscillating motor 20 can be isolated from the battery at the rear side, realizing the shock-absorbing function and avoiding the deterioration of comfort caused by excessive vibration during the use of the user.

[0054] Among them, an inner cavity is formed in the motor bracket 21 to accommodate the vibrating arm assembly 24. The outer edge of the rear part of the inner cavity is coated with an electromagnetic coil 22. At the same time, 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 linear iron swing arm and the rear part is located in the electromagnetic coil 22 at the rear part of the inner cavity. A disc portion is formed at the front part of the swing arm 241 and a shaft hole for the rotating shaft 242 to pass through is provided on the disc portion. Both ends of the rotating shaft 242 are rotatably supported on the motor bracket 21 through bearings 243. The rear end of the connecting frame 244 is coated on the front part of the swing arm 241 and forms a cylindrical structure for accommodating 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 24 to the output shaft 245 for output.

[0055] Among them, the swing arm 241, the rotating shaft 242, and the output shaft 245 are integrally formed by the method of secondary injection molding of plastic to form the connecting frame 244. The rotation axis of the rotating shaft 242 is perpendicular to the swinging direction of the swing arm 241. The rotating shaft 243 is preferably arranged in the shaft hole of the swing arm 241 at about 2 / 3 of the swing arm 241, so that the rotating shaft and the swing arm are in a cross shape after combination. Axial shoulders for cooperating with the bearings 243 are provided at both ends of the rotating shaft 242. At least one concave ring is provided at the rear end of the output shaft 245, so that the output shaft 245 and the connecting frame 244 are firmly integrally formed after secondary injection molding. At least one concave ring of the output shaft 245 can effectively prevent the output from generating displacement under the action of external force.

[0056] Thus, as a power conversion device for converting electromagnetic energy into mechanical energy, the oscillating motor finally outputs a driving torque 2-5 times that of a traditional DC motor under the same working conditions and the same volume under the same power consumption conditions to meet the high-frequency swinging power requirements of an electric toothbrush.

[0057] Among them, also referring to Figure 7A , Figure 7B and Figure 7C , the vibrating arm assembly is located inside the cavity of the device. A space is formed between the rear part 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. A stepped portion for accommodating the magnet 27 is formed at the rear end of the motor bracket 21, so that there is at least a gap of 0.2 - 0.6 mm between the end of the swing arm 241 and the magnet. Thus, the magnet 27 at the tail can induce a magnetic force on the tail of the iron swing arm without physical contact.

[0058] Two magnets are arranged in parallel at the tail of the bracket, with the magnetization surface facing the swing arm. After the combination of the two magnets, the same - direction polarities are opposite to each other.

[0059] The front cover 25 at the front end of the motor bracket 21 is covered with a sealing cover 26 to achieve sealing. The setting of this front cover strengthens the stability of the bearings at both ends of the rotating shaft and provides a limit for the sealing cover.

[0060] Among them, the process of converting the electromagnetic force of the constant - amplitude high - frequency oscillating motor proposed by the present utility model into swing mechanical energy is as follows:

[0061] 1. Connect a square - wave power current with alternating positive and negative polarities to the electromagnetic coil.

[0062] 2. As Figure 7A shown, assuming that in the positive half - cycle of the square wave, since there is an iron swing arm built into the electromagnetic coil 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 into magnetism under the action of the electromagnetic field. Assuming that the swing arm close to the magnetic pole is polarized into the S - pole at this moment, under the principle of like - poles repelling and opposite - poles attracting, the swing arm of the vibrating arm assembly will swing in the D1 direction.

[0063] 3. As Figure 7C shown, when the square - wave current switches to the negative half - cycle, due to the reversal of the power supply polarity of the electromagnetic coil, the current acting on the electromagnetic coil is in the opposite direction to that in the positive half - cycle, and the magnetic pole induced on 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 in reverse.

[0064] 4. After completing the current switching of the positive and negative half - cycles, the swing of the vibrating arm assembly of the motor constitutes a complete vibration cycle. The swing frequency of the vibrating arm assembly depends on the frequency of the square - wave current of the driving coil. In the embodiment of the present utility model, the electromagnetic coil preferably operates at 140 Hz - 250 Hz. The strength of the swing angle of the vibrating arm assembly can be adjusted by the duty cycle of the square wave, and the swing angle is proportional to the size of the duty cycle.

[0065] Among them, the swing arm 241 is made of ferromagnetic material. Since the working frequency can be as high as 250 Hz, the swing arm 241 is stacked by silicon steel sheets with low high - frequency eddy - current loss.

[0066] As Figure 8A shown, the magnet 27 of the present utility model can be composed of two independent magnets M1 arranged to form magnetic poles, or as Figure 8B shown, by using the same-plane multi-pole magnetization process, only one magnet M2 is used, and the N and S poles are magnetized and polarized on the same plane at the same time. The arrangement directions of N and S are the same as the polarities of the two magnets to meet the requirements of the present utility model.

[0067] Among them, the technology of detecting the battery voltage by sensorless synchronous drive pulse is adopted, relying on a specific drive pulse period to monitor the change of the drive current caused by the change of the dynamic impedance of the motor, combining corresponding algorithms, and compensating the drive power in real time according to the monitored motor working conditions to achieve a constant swing amplitude output.

[0068] Among them, in the control method related to the constant-amplitude high-frequency oscillating motor of the present utility model, the typical drive wave voltage shape is a square wave, and the frequency of the square wave is the same as the output swing frequency. Theoretically, when the motor outputs full power under the condition of constant voltage, the duty cycle of the square wave should be 100%. In practical applications, the most basic power device for driving is an H drive bridge composed of 4 FETs. The H bridge changes with the input signal, and the positive and negative voltages at the output terminal are switched at high speed. Due to the response time difference of the FET switching, if the switching is carried out at a duty cycle of 100%, there will be a situation where the 4 FETs of the H bridge conduct simultaneously, resulting in a short circuit inside the H bridge and causing damage to 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 working in the dead zone, and the power supply to the motor should be stopped during this interval. After considering the dead zone, the maximum duty cycle of the final square wave is usually 98% - 99%, not 100%.

[0069] If the duty cycle of the reverse shrinking pulse is reduced, the effective power of the drive will be reduced in the reverse direction, and thus the swing amplitude of the oscillating motor will decrease accordingly. Using the mechanism that the output power can be changed by adjusting the duty cycle of the pulse as the theoretical basis for the output rate compensation of the oscillating motor mentioned in the present utility model.

[0070] As Figure 9As shown in the figure, it shows a waveform diagram of the voltage signal at the output of a typical H-bridge connected to a pure resistive load. In the figure: S1 is the effective working pulse in the positive half cycle, S2 is the effective working pulse in the negative half cycle, t12 and t22 are the working stop cycles in the positive and negative half cycles respectively, which include the necessary dead zone control time and the stop time for adjusting the overall pulse duty cycle. t is a complete driving cycle, and t = S1 + S2 + t12 + t22; assuming S1 = S2 and t12 = t22, the positive and negative half cycles are completely symmetric; the duty cycle Duty = S1 / (t12 + S1)×100% or Duty = S2 / (t22 + S2)×100%. In actual control, by synchronously adjusting the ratio of t12 and t22 in the entire pulse t, that is, the duty cycle Duty parameter, the power control of the drive can be achieved. Obviously, the larger the proportion of the t12 and t22 cycles, the smaller the output power. Controlling the strength of the output power by adjusting the duty cycle ratio is the theoretical basis for the control technology of the motor of the present invention.

[0071] Before elaborating on how to implement the constant amplitude control theory of the motor mentioned in the present invention, first elaborate on the principle and method of collecting power current without additional sensor devices, as Figure 10 As shown in the figure, it shows a schematic diagram of the principle of collecting power current without additional sensor devices. Among them, BT represents the battery pack. Inside the battery pack, V is the standard battery and R0 is the internal resistance of the battery pack; MCU is the microprocessor of the line control unit, and inside the microprocessor, there is an analog-to-digital converter labeled ADC and a reference voltage source Vref dedicated to ADC; S1~S4 are the output drive signal ports specially set by the MCU for the H-bridge; H is the H power drive bridge composed of two pairs of complementary FETs; M is the shaking motor involved in the present invention; I is the power current.

[0072] Table 1 below shows the truth values of the typical 4 working states of the H-bridge.

[0073] Table 1

[0074]

[0075] Among them, there are two key points for the current sampling required by the constant amplitude technology involved in the present invention:

[0076] 1. Utilizing the existence of the internal resistance R0 of the battery pack, during power drive, the changing power current I will inevitably generate a changing voltage drop Vdp on R0. By detecting Vdp through the MCU control unit, the change in the load current can be reflected, that is, Vdp = R0 × I.

[0077] 2. In order to simplify the hardware design, a microprocessor with a built-in analog-to-digital converter ADC and a voltage reference source Vref is selected, so that the change in the power current can be directly calculated without supporting more external designs.

[0078] Unless otherwise explicitly stated, the power current change detection discussed in this article is all implemented based on the method of detecting the change in the voltage drop Vdp across R0.

[0079] The following will further explain the implementation method and process of constant amplitude compensation in two parts.

[0080] When the H drive bridge is connected to a pure resistive load and an inductive motor load, the signals will show obvious differences, such as Figure 11 As shown in the figure, in the figure, the solid line CV1 is the waveform performance of the pure resistive load, and the dotted line is the waveform shown by the oscillating motor actually connected to the inductive reactance. The obvious difference between these two groups of waveforms is that a peak ringing marked as D appears in each working pulse. From the starting point a to the ending point b of each effective working waveform, under the influence of the inductive reactance load, the horizontal line of the standard rectangular square wave becomes a slope line.

[0081] When the motor is connected to the driving end, obvious overshoot and ringing occur in the square wave. mainly in the stopped cycle (dead zone cycle + power adjustment cycle), the power supply to the motor coil is stopped. The coil, being an inductive load, will generate a back electromotive force, and the swing arm continues to cut the magnetic lines of force of the magnet under the action of inertia, forming a variable impedance to the coil. The superposition of the back electromotive force and the variable impedance of the coil on the power supply directly affects the smoothness of the rising edge and pulse width of the square wave.

[0082] After the coil is powered off, the swing arm continues to swing under the action of inertia. Assuming that the swing frequency remains unchanged, the larger the swing amplitude, the greater the speed at which the magnetized swing arm cuts the magnetic lines of force, and the greater the influence on the variable impedance generated by the coil. Obviously, if the instantaneous current related to the influence of the variable impedance can be measured, the current linear speed of the current swing arm can be relatively mapped, that is, the relative change amount of the current output swing. This idea is the most important theoretical basis for the real-time swing amplitude measurement involved in the constant amplitude driving technology mentioned in this utility model.

[0083] In order to reduce the influence of electromagnetic interference in the stray space on signal detection, the swing amplitude related data detection mentioned in this utility model is not set at the end of the motor drive output, but directly measures the instantaneous voltage change at the battery terminal. This voltage change has a mutual mapping and corresponding relationship with the current change at the motor drive end.

[0084] Figure 12 Shows the voltage at the battery terminal during direct measurement work. Under different loads, the oscillating motor shows different swing amplitudes and wave clusters. In the figure, the solid line curve CV1 is the waveform shown under no-load conditions, and the dotted line curves CV2, CV3, CV4, and CV5 are the waveforms shown with increasing load from small to large. It can be observed that the voltage at the battery terminal changes with the load at a certain time sequence in each driving pulse. For example, in the interval t1 - t2 of the attached drawing, the correlation between the motor load and the voltage can be clearly observed. The heavier the load, the higher the voltage. The summarized rule is:

[0085] Load: CV5 > CV4 > CV3 > CV2 > CV1;

[0086] Pulse end voltage: V5 > V4 > V3 > V2 > V1.

[0087] Figure 13 It shows that the data is presented in a scatter plot, where the V-axis is the battery terminal voltage, the D-axis is the swing angle of the pendulum axis, and the heavier the load, the smaller the swing angle of the pendulum axis.

[0088] V5 to V1 are 5 sampling points, and curve a is the curve formed by connecting the actual sampling points in series. It can be clearly seen from the attached figure that the voltage of the sampling points is strongly correlated with the swing angle under different loads. To simplify the computational workload of the microprocessor, the above sampling data can be fitted into a straight line b by the least squares method.

[0089] The instantaneous voltage change U at the battery terminal is affected by two important factors, that is, U = Ub + Ur, where Ub is the back electromotive force generated during the power-off stop period of the motor, and Ur is the change in the dynamic inductive reactance of the coil caused by the change in the swing amplitude of the vibrating arm position. The change in the dynamic inductive reactance directly affects the change in the conduction rate of the current in the coil, and essentially forms a changing impedance. The change in the coil impedance will ultimately affect the performance of the rising edge of each pulse at the motor coil terminal.

[0090] Therefore, as long as the voltage change component caused by the impedance change at the rising edge of each pulse of the motor can be effectively separated, the current motor swing amplitude data can be quantified.

[0091] To better separate the changing impedance of the motor coil, the reasonable and correct current sampling points are particularly important. It can be seen from the wave cluster that, different from the conventional sampling method, for the conventional DC motor working condition, the conventional sampling method ignores the pulse synchronization information and samples continuously at equal intervals densely. The longer the sampling period, the more stable the weighted average value, and it can well reflect the relationship between voltage and load. However, it has been proved that this non-synchronous mean sampling method is ineffective for the brushless motor driven by pulse commutation. The voltage result obtained by continuous sampling without pulse synchronization has no obvious correlation with the load change.

[0092] Figure 14 It shows the performance of non-synchronous continuous dense voltage sampling in the brushless motor: In the figure: V-axis: voltage scalar, T-axis: time scalar, S1 to Sn are the time sequences of non-synchronous continuous sampling, t2 is the sampling period, P1 to pn are the voltage change period signals observed at the battery terminal. Obviously, this period is related to and synchronized with the phase of the motor drive pulse, t1 is the motor drive pulse period, and D1 to Dn are the sampled voltage values.

[0093] As can be seen from the figure, if t1 and t2 are not synchronized, the sampling positions of D1 and D5 are significantly different from the rising and falling positions of the pulse. Among them, D1 is close to the head of pulse P1, while D5 is close to the tail of pulse P3, and the difference between these two sampling values is relatively large. Therefore, the weighted average method can be used for data averaging: that is, Avg = (D1 + D2 + Dn…) / n… The average value Avg fails to correctly capture the data correctly associating the load and the voltage. Therefore, the traditional asynchronous voltage sampling is not suitable for the shaking motor working conditions mentioned in the present invention.

[0094] Figure 15 The performance of voltage data in the synchronous sampling method is shown: In the figure: V-axis: voltage scalar, T-axis: time scalar, S1~Sn are the time sequences of asynchronous continuous sampling, t2 is the sampling period, and P1~pn are the voltage change period signals observed at the battery terminal. Obviously, this period is in phase and synchronous with the pulse. t1 is the motor drive pulse period, and D1~Dn are the sampled voltage values.

[0095] From Figure 15 it can be observed that if t1 and t2 are synchronized, the sampling positions of D1, D2, D3…Dn are consistent with the rising and falling positions of the pulse. Assuming that the weighted average method is used for data averaging: that is, Avg = (D1 + D2 + Dn…) / n… The average value Avg can correctly capture the data correctly associating the load and the voltage. Therefore, synchronous voltage sampling is the preferred current sampling scheme for the shaking motor mentioned in the present invention.

[0096] Based on the data performance of the above two figures, it is obvious to explain the difference between the traditional simple weighted average current sampling mode and synchronous sampling. The shaking motor generally belongs to the category of brushless motors, and both are driven by power pulses with high-frequency switching of positive and negative polarities. It is necessary to use a sampling mode synchronized with the pulse phase to analyze the current information related to the load.

[0097] After adopting synchronous technology for sampling, in order to further improve the signal quality, some additional technical means are still needed to filter the back electromotive force signals generated by unnecessary coils that affect the load current performance.

[0098] The overcharge amount at the rising edge of the pulse includes not only the coil dynamic impedance information but also the back electromotive force generated after the coil is powered off. If the information of each pulse rising edge overcharge amount is directly used to quantify the swing amplitude relationship without considering the influence of the back electromotive force on signal superposition, the existence of the back electromotive force will more or less reduce the quantization analysis accuracy. In order to eliminate the influence of the back electromotive force on the overcharge amount of each pulse rising edge, the motor coil can be instantaneously short-circuited by the H-bridge during each drive stop cycle to quickly release the back electromotive force. The embodiment proves that after eliminating the back electromotive force, the change of the motor swing amplitude can be monitored more sensitively, and the signal-to-noise ratio is improved.

[0099] Therefore,Figure 16 It is a schematic diagram of the principle of short - circuiting the H - bridge to absorb the back - electromotive force. In the figure: F1 - F4 are the H - bridge composed of two pairs of complementary NP - channel FETs as the drive of the shaker motor, M is the shaker motor. Before starting the motor current detection and after the drive power is disconnected, when S1 and S2 inputs are set to high level, F1 and F2 enter the cut - off state. And when S3 and S4 inputs also input high level, F3 and F4 conduct. After F3 and F4 conduct, F3, F4 and M form a loop, short - circuiting the back - electromotive force generated at both ends of the motor M, generating a short - circuit current loop C, and the back - electromotive force is converted into heat energy and dissipated on the motor coil.

[0100] When the absorption of the back - electromotive force is completed, S3 and S4 jump to high level and enter the cut - off state, and the MCU starts the ADC conversion for current detection.

[0101] Figure 17 It shows the comparison diagram of current signals before and after the shaker motor eliminates the back - electromotive force. In the figure: V - axis: voltage scalar, T - axis: time scalar, P1 - P3 show three groups of pulse - period signals, the solid curve CV1 is the voltage curve after using the short - circuit technology to eliminate the back - electromotive force, the dashed curve CV2 is the voltage curve affected by the back - electromotive force, Ts is the important area including load - change information, C is the ringing peak signal that appears without using short - circuit to eliminate the back - electromotive force, and a is the area where the influence of the back - electromotive force is larger.

[0102] Because in the shaded area where the signal ringing peak generated by the back - electromotive force in the marked a has a more serious impact on the effective load signal in the Ts interval, using technical means to absorb the ringing peak has a positive significance for analyzing the load signal.

[0103] After the back - electromotive force is short - circuited and eliminated, it is beneficial to analyze the change of the dynamic impedance of the coil, but it will also have a negative impact on the motor. At the moment when the short - circuit coil current is generated, heat energy will be generated in the coil, causing the working temperature of the coil to rise. Whether to adopt the back - electromotive force elimination technology or choose a reasonable short - circuit timing can be decided according to the actual application.

[0104] After obtaining effective swing quantization data, this data can be used to adjust the duty cycle of the drive pulse in real - time. When the swing is lower than the set value, continuously increase the pulse duty cycle to increase the drive power and raise the swing; conversely, continuously decrease the duty cycle to reduce the drive pulse power and decrease the swing. By dynamically monitoring the swing value and adjusting the pulse drive power in real - time through the above - discussed method, a stable output swing can be obtained under load changes.

[0105] Figure 18The process principle block diagram of the constant amplitude correction technology related to the present utility model. In specific embodiments, in addition to solving the battery voltage variation associated with the analysis and swing amplitude, it is also necessary to correctly select a suitable sampling frequency and adjustment frequency. Since the ADC collects and processes data, it will consume resources. Over-dense data sampling will interfere with the stability of the driving pulse phase, resulting in phase jitter. The motor swing shaft will show irregular swing jitter and generate abnormal sounds. The density of adjusting the pulse duty cycle also needs to be appropriate. Since the motor swing shaft has rotational inertia and has requirements for the response time domain, too dense adjustment will weaken the useful amplitude information analyzed and cause overshoot, resulting in overshoot oscillation and inability to control normally. Too sparse adjustment will cause the control to be slow and lagging, and the compensation effect will not be ideal. Generally, the following factors need to be considered in actual control:

[0106] 1. Synchronization point with the motor signal: Embodiments prove that it is preferably to sample data when the pulse is about to end, which is the most stable and has a high signal-to-noise ratio.

[0107] 2. Startup back electromotive force duration and density: The back electromotive force absorption should not be enabled for every pulse. It should only be enabled before detecting the battery voltage and immediately turned off after the detection is completed. Otherwise, a large amount of heat will be dissipated on the motor coil, causing the motor working temperature to rise rapidly. Similarly, the absorption duration is also a key point for controlling heat, and specifically, it should be based on the actual situation and the test results.

[0108] 3. Battery voltage sampling: It should not be carried out for every pulse. In the test of the embodiment, it is better to sample once every 20 pulses. Over-dense sampling will cause the motor to have phase jitter and abnormal sounds.

[0109] 4. Frequency of adjusting the motor drive pulse duty cycle: It also needs to be reasonable. Too dense correction will cause overshoot oscillation, and too sparse compensation will be slow to respond, and the swing amplitude will be unstable after the load changes.

[0110] Therefore, the control method includes the following steps:

[0111] Step 1: Synchronously output a pulse (which can be the above-mentioned square wave pulse);

[0112] Step 2: Start the back electromotive force absorption;

[0113] Step 3: Synchronously collect the battery voltage;

[0114] Step 4: Analyze the variables related to the load;

[0115] Step 5: Calculate the correction amount;

[0116] Step 6: After correcting the drive duty cycle, return to Step 1.

[0117] Figure 20Shows the signal processing flowchart of the dynamic servo process for obtaining a constant output swing of the motor as mentioned in the present utility model.

[0118] It includes the following steps:

[0119] Step 1: After the interrupt response, determine whether 20 pulse intervals are satisfied. If yes, enter Step 2; otherwise, exit.

[0120] Step 2: Determine whether it is a stop cycle. If yes, enter Step 3; otherwise, exit.

[0121] Step 3: Start the back electromotive force absorption. Determine whether the drive pulse ends. If yes, enter Step 4; otherwise, exit.

[0122] Step 4: Collect the battery voltage. If the voltage value is less than the previous collected value, enter Step 5; otherwise, enter Step 6.

[0123] Step 5: Increase the drive pulse duty cycle and then exit.

[0124] Step 6: Determine whether the voltage value is greater than the previous collected value. If yes, decrease the drive pulse duty cycle and then exit; otherwise, directly exit.

[0125] The above-mentioned exit is to directly exit the interrupt response.

[0126] In the embodiment of the present utility model, after the system initialization, the initial pulse duty cycle without compensation is preset to 45%, and the maximum compensation is 98%.

[0127] Figure 19 It is a comparison chart of the swing angle change curves with and without compensation when the load changes. Among them, the vertical coordinate is the swing angle shown by the swing axis, and the horizontal coordinate is the force applied to the swing axis. Curve CV1 is the output performance without compensation, and CV2 is the performance after real-time dynamic compensation. It can be seen from the figure that after compensation, the swing amplitude's ability to resist load changes is significantly improved.

[0128] Obviously, the above description and record are only examples and not intended to limit the disclosure, application, or use of the present utility model. Although it has been described in the embodiments and shown in the drawings, the present utility model does not limit to the specific examples described in the embodiments and shown in the drawings as the currently considered best mode to implement the teachings of the present utility model. The scope of the present utility model will include any embodiments falling within the previous description and the appended claims.

Claims

1. A constant-amplitude high-frequency oscillating motor, comprising a motor bracket, an electromagnetic coil, a shock absorber, a vibrating arm assembly, a front cover, and a magnet. The front end of the motor bracket is provided with a front cover, and the rear end is provided with a magnet. A shock absorber is further provided at the rear side of the magnet so as to isolate the vibration of the oscillating motor from the battery at the rear side. It is characterized in that: An inner cavity is formed in the motor bracket to accommodate the vibrating arm assembly. The outer edge of the rear part of the inner cavity is covered with an electromagnetic coil. The vibrating arm assembly includes a swing arm, a rotating shaft, a bearing, and a connecting frame. The rear part of the swing arm is located in the electromagnetic coil at the rear part of the inner cavity. The front part of the swing arm forms a disc portion, and the disc portion is provided with a shaft hole through which the rotating shaft passes. Both ends of the rotating shaft are rotatably supported on the motor bracket through bearings. The rear end of the connecting frame is covered on the front part of the swing arm and forms a cylindrical structure for accommodating 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 according to claim 1, wherein: The swing arm, the rotating shaft, and the output shaft are integrally formed by secondary injection molding of plastic to form a connecting frame to constitute the vibrating arm assembly.

3. The constant-amplitude high-frequency oscillating motor according to claim 1, wherein: The swing arm is a straight iron swing arm, and the axis of rotation of the rotating shaft is perpendicular to the swinging direction of the swing arm, so that the rotating shaft and the swing arm are cross-shaped after combination.

4. The constant-amplitude high-frequency shaking motor according to claim 2, wherein: Both ends of the rotating shaft are provided with shoulders for cooperating with the bearings. At least one concave ring is provided at the rear end of the output shaft so that the output shaft and the connecting frame are firmly integrally formed after secondary injection molding and effectively prevent the output from being displaced under the action of external force.

5. The constant-amplitude high-frequency oscillating motor according to claim 1, wherein: A space is formed between the rear part of the swing arm and the inner wall of the motor bracket to allow the swing arm to swing back and forth by 20 degrees without collision with the motor bracket.

6. The constant-amplitude high-frequency oscillating motor according to claim 1, wherein: A stepped portion for accommodating the magnet is formed at the rear end of the motor bracket so that a gap of 0.2 - 0.6 mm is maintained between the end of the swing arm and the magnet.

7. The constant-amplitude high-frequency shaking motor according to claim 1, wherein: The front cover at the front end of the motor bracket is covered with a sealing cover to achieve sealing.

8. The constant-amplitude high-frequency shaking motor according to claim 1, characterized in that: The swing arm is stacked by silicon steel sheets with high-frequency and low eddy current loss.

9. The constant-amplitude high-frequency shaking motor according to claim 1, characterized in that: The magnet is formed by arranging two independent magnets.

10. The constant-amplitude high-frequency shaking motor according to claim 1, characterized in that: The magnet magnetizes and polarizes the N and S poles simultaneously in the same plane and uses one magnet.

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