Constant-amplitude high-frequency shimmy motor and control method thereof

Abstract

The invention relates to a constant-amplitude high-frequency shimmy motor and a control method thereof, the structure comprises a motor support, an electromagnetic coil, a damping block, a vibration 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, and an inner cavity is formed in the motor support to accommodate the vibration arm assembly. The outer edge of the rear portion of the inner cavity is coated with an electromagnetic coil, 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 a shaft hole allowing the rotating shaft to penetrate through is formed in the disc part; 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, 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 more constant and reliable.

Description

Technical Field

[0001] The present invention relates to the technical field of electric toothbrush motors, and in particular to a constant-amplitude high-frequency oscillating motor suitable for electric toothbrushes and a control method thereof. Background Art

[0002] At present, electric toothbrushes are often driven by DC motors, and the maximum operating speed of DC motor-driven electric toothbrushes is less than 133Hz, and a gear set or lever connecting rod is required to complete the torque conversion. Otherwise, the direct drive output torque is too small to meet the power requirements for cleaning. For example, in order to ensure that the brush head can effectively work at 140-350Hz, the torque conversion of the gear set requires the DC motor speed to be much higher than the brush plate output by 2-4 times. Under this condition, the conventional power conversion mechanism will produce high working noise that makes the user uncomfortable, and the wear of the components will also increase sharply due to the increase in speed, affecting the product life.

[0003] Moreover, the power system of the electric toothbrush, whether it is a conventional brushed DC motor or a brushless electromagnetic force driven motor, has output power related to the working voltage and the load. Most of the time, the higher the working voltage, the higher the output speed or the larger the output swing, and vice versa. The heavier the load, the lower the speed or swing. In actual product applications, as the battery voltage decreases or the load suddenly increases, the output torque will be insufficient, and there will be a significant difference in the performance of high and low voltage load capacity, which affects the user's experience. In order to improve the motor's load resistance, dynamic compensation of the drive power must be achieved. In order to achieve dynamic compensation, it is generally necessary to rely on sensors to monitor the motor's operating conditions in real time. Conventional motor condition monitoring sensors include gratings, magnetic gratings, or Hall devices, or electromagnetic induction coils to monitor speed or swing amplitude data. Traditional methods of motor condition monitoring technology are not conducive to products that require installation space and product costs.

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

[0005] 1.1 Grating detection of displacement: Grating is a traditional displacement detection technology that requires one or more sets of infrared optical light sources and photosensitive receiving components to monitor the change signal of the grating. Due to the volume limitation of this technology, it is not suitable for the motor servo requirements mentioned in this invention.

[0006] 1.2 Hall detects changes in magnetic field. The magnet is fixed on the motor shaft, and the magnet swings at high speed with the motor 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 shaft. High-frequency Hall sensors are expensive and do not meet the motor design requirements mentioned in the present invention.

[0007] 1.3 Capacitance change detection displacement, two metal electrodes are set in parallel on the product, one electrode is a stationary electrode, and the other electrode is an electrode that moves with the swing shaft. The movement of the motor's swing shaft can change the capacitance between the two electrodes accordingly. By monitoring the change in capacitance of the measuring electrodes, the displacement of the motor's swing shaft can be quantified. Because the capacitance method of detecting displacement requires a large implementation space, it does not meet the motor design requirements mentioned in the present invention.

[0008] 1.4 Eddy current change detection displacement, the sensor has a built-in high-frequency oscillation circuit and transmits high-frequency signals to the outside. When the object to be detected is a moving metal, the high-frequency signal will generate eddy currents on the metal surface.

[0009] The distance between the metal sheet and the sensor will affect the size of the eddy current, which will further affect the resonant frequency parameters of the oscillation. By real-time monitoring of the resonant point of the oscillator, the displacement of the metal displacement sheet can be quantified. This sensor technology is costly and bulky and does not meet the motor design requirements mentioned in the present invention.

[0010] To this end, in view of the above defects, the designers of the present invention have concentrated on research and design, combined with many years of experience and achievements in related industries, and have researched and designed a constant amplitude high frequency oscillating motor and its control method to overcome the above defects. Summary of the invention

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

[0012] To achieve the above purpose, the present invention discloses a constant amplitude high frequency oscillating motor, comprising a motor bracket, an electromagnetic coil, a damping block, a vibration arm assembly, a front cover and a magnet. The front end of the motor bracket is provided with a front cover, the rear end is provided with a magnet, and the rear side of the magnet is further provided with a damping block so as to isolate the vibration of the oscillating motor from the battery at the rear side. The invention is characterized in that:

[0013] An inner hollow cavity is formed in the motor bracket to accommodate the vibration arm assembly, and the rear outer edge of the inner hollow 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 swing arm is a straight iron swing arm and the rear part is located in the electromagnetic coil at the rear of the inner hollow cavity. The front part of the swing arm forms a disc portion and the disc portion is provided with an axial hole for the rotating shaft to pass through. Both ends of the rotating shaft are rotatably supported on the motor bracket through bearings. The rear end of the connecting frame covers 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 vibration arm assembly to the output shaft for output.

[0014] The swing arm, the rotating shaft and the output shaft are integrally embedded in a connecting frame by secondary plastic injection molding to form a vibration arm assembly. The rotation axis of the rotating shaft and the swing direction of the swing arm are perpendicular to each other, so that the rotating shaft and the swing arm are in a cross shape after being combined.

[0015] Wherein: both ends of the rotating shaft are provided with shaft shoulders cooperating 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 integrated 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] 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 20 degrees without colliding with the motor bracket.

[0017] Wherein: the rear end of the motor bracket forms a step portion for accommodating the magnet so that a gap of at least 0.2-0.6 mm is maintained between the end of the swing arm and the magnet.

[0018] Wherein: the front cover at the front end of the motor bracket is provided with a sealing cover to achieve sealing.

[0019] Wherein: 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 in an array or a single magnet is used in which the N and S poles are simultaneously magnetized and polarized in the same plane.

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

[0022] The steps include:

[0023] Step 1: After the interrupt response, determine whether the 20 pulse intervals are met. If yes, go to step 2, otherwise exit;

[0024] Step 2: Determine whether it is a stop cycle, if yes, go to step 3, otherwise exit;

[0025] Step 3: Start the back electromotive force absorption and determine whether the drive pulse is ended. If yes, go to step 4, otherwise exit;

[0026] Step 4: Collect the battery voltage. If the voltage value is less than the last collected value, go to step 5, otherwise go to step 6;

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

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

[0029] From the above content, it can be known that the constant amplitude high frequency oscillating motor and the control method thereof of the present invention have the following effects:

[0030] 1. It can work effectively at 140-350Hz, and adopts high-torque output pendulum motor to replace the traditional DC motor, reducing the noise caused by the gear set or connecting rod torque conversion link.

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

[0032] 3. Use the correlation to quantify the relationship between the swing and the load, and rely on this variable relationship to change the duty cycle of the drive pulse in real time to increase or decrease the motor output swing. By adjusting the duty cycle in real time, the purpose of constant motor output swing can be achieved.

[0033] 4. The number of sensors used for swing detection is reduced and saved. Only the MCU is used 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 particularly suitable for multiple application scenarios such as electric toothbrushes, shavers, hair trimmers, etc. It has a stable output torque, simple structure, high durability, and low cost market prospects.

[0034] 5. Real-time detection of the motor working condition is realized, and the working condition information analyzed by the algorithm is used to complete real-time dynamic output power compensation by controlling the duty cycle of the driving artery, thereby achieving constant swing amplitude or constant torque output of the swing motor.

[0035] The details of the present invention can be obtained from the following description and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 The schematic diagram of the structure of the constant amplitude high frequency oscillating motor of the present invention is shown.

[0037] Figure 2 A schematic diagram showing the internal components of the constant amplitude high frequency pendulum vibration motor of the present invention in a half-cut manner is shown.

[0038] Figure 3 The exploded schematic diagram of the constant amplitude high frequency oscillating motor of the present invention is shown.

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

[0040] Figure 5 A cross-sectional view from another direction of the constant amplitude high frequency oscillating motor of the present invention is shown.

[0041] Figure 6 The schematic diagram shows the structure of the vibration arm assembly of the constant amplitude high frequency pendulum vibration motor in the present invention.

[0042] Fig. 7A , Figure 7B and Figure 7C The schematic diagram shows the three states of the constant amplitude high frequency oscillating motor under the action of electromagnetic force in the present invention, wherein Fig. 7A and Figure 7C They are in opposite swinging state. Figure 7B It is the static state where the current stops.

[0043] Fig. 8A and Figure 8B Two principle schematic diagrams of the magnetic poles in the present invention are shown.

[0044] Fig. 9 The figure shows the voltage signal waveform of a typical H-bridge output connected to a pure resistive load.

[0045] Fig.10 The schematic diagram shows the principle of power current acquisition without additional sensor devices.

[0046] Fig.11 The true value diagram of the four typical working states of the H-bridge is shown.

[0047] Fig.12 The signal diagram of the H-bridge connected to a pure resistive load and an inductive motor load is shown.

[0048] Fig.13 A schematic diagram showing the direct measurement of the battery terminal voltage during operation showing different swing amplitudes and wave clusters of the oscillating motor under different loads.

[0049] Fig.14 Shows Fig.13 A scatter plot showing the correlation data in .

[0050] Fig.15 A schematic diagram showing asynchronous continuous dense voltage sampling.

[0051] Fig.16 A schematic diagram showing the voltage data of the synchronous sampling method.

[0052] Fig.17 The schematic diagram shows the principle of shorting the H-bridge to absorb the back EMF.

[0053] Fig.18 The figure shows the comparison of the current signal before and after the back EMF of the oscillating motor is eliminated.

[0054] Fig.19 Block diagram showing the process principle of constant amplitude correction technology

[0055] Fig. 20 The comparison of the swing angle change curves with and without compensation when the load changes is shown.

[0056] Fig.21 The signal processing flow chart of the dynamic servo process for obtaining a constant output swing of the motor in the present invention is shown.

[0057] Reference numerals:

[0058] 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 DESCRIPTION

[0059] See also Figure 1 and 2 , showing the constant amplitude high frequency oscillating motor of the present invention, wherein Figure 1 The structure diagram of the constant amplitude high frequency oscillating motor of the present invention is shown. Figure 2 A schematic diagram showing the internal components of the constant amplitude high frequency pendulum vibration motor of the present invention in a half-cut manner is shown.

[0060] The constant amplitude high frequency oscillating motor of the present invention comprises a motor bracket 21, an electromagnetic coil 22, a shock absorbing block 23, a vibration arm assembly 24, a front cover 25 and a magnet 27. Figure 3 The exploded diagram shown and Figure 4 , Figure 5 It can be seen more clearly from the cross-sectional view that the front end of the motor bracket 21 is provided with a front cover 25, the rear end is provided with a magnet 27, and the rear side of the magnet 27 is also provided with a shock-absorbing block 23, so that the vibration of the swing motor 20 can be isolated from the battery on the rear side, thereby achieving a shock-absorbing function and avoiding excessive vibration during use that causes the user's comfort to deteriorate.

[0061] The motor bracket 21 forms an inner hollow cavity to accommodate the vibration arm assembly 24, and the outer edge of the rear of the inner hollow cavity is covered with an electromagnetic coil 22. Figure 6 The vibration 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 and its rear portion is located in the electromagnetic coil 22 at the rear of the inner hollow cavity. The front portion of the swing arm 241 forms a disc portion and the disc portion is provided with an axial hole for the rotating shaft 242 to pass through. 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 covers the front portion 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 vibration arm assembly 24 to the output shaft 245 for output.

[0062] Among them, the swing arm 241, the rotating shaft 242, and the output shaft 245 are embedded in one piece to form a vibration arm assembly by adopting a plastic secondary injection molding method to form a connecting frame 244. The rotation axis of the rotating shaft 242 and the swing direction of the swing arm 241 are perpendicular to each other. The rotating shaft 243 is preferably arranged in a rotating shaft hole at about 2 / 3 of the swing arm 241, so that the rotating shaft and the swing arm are cross-shaped after being combined. Both ends of the rotating shaft 242 are provided with shoulders that cooperate with the bearing 243, and the rear end of the output shaft 245 is provided with at least one concave ring, so that after the secondary injection molding, the output shaft 245 and the connecting frame 244 are stably integrated, and the at least one concave ring of the output shaft 245 can effectively prevent the output from being displaced under the action of external force.

[0063] Therefore, the oscillating motor is a power conversion device that converts electromagnetic energy into mechanical energy. Under the same power consumption conditions, the final output driving torque of the oscillating motor is 2-5 times the output torque of the traditional DC motor of the same volume under the same working conditions, so as to meet the high-frequency oscillation power requirements of the electric toothbrush.

[0064] Also see Fig. 7A , Figure 7B as well as Figure 7C The vibration arm assembly is placed in the hollow body of the device, and a space is formed between the rear part of the swing arm 241 and the inner wall of the motor bracket 21, which can allow the swing arm 241 to swing back and forth 20 degrees without colliding with the motor bracket. The rear end of the motor bracket 21 forms a step portion for accommodating the magnet 27 so that a gap of at least 0.2-0.6mm is maintained between the end of the swing arm 241 and the magnet, so that the magnet 27 at the tail can induce a magnetic force on the tail of the iron swing arm, but there is no physical contact.

[0065] Two magnets are arranged in parallel at the tail of the bracket, with the magnetized surface facing the swing arm. After the two magnets are combined, the polarities in the same direction are opposite to each other.

[0066] The front cover 25 at the front end of the motor bracket 21 is covered with a sealing cover 26 to achieve sealing. The provision of the front cover strengthens the stability of the bearings at both ends of the rotating shaft and provides a limit for the sealing cover.

[0067] The process of converting the electromagnetic force of the constant amplitude high frequency oscillating motor proposed by the present invention into oscillating mechanical energy is as follows:

[0068] 1. Connect the electromagnetic coil to a square wave power current with alternating positive and negative polarity.

[0069] 2. If Fig. 7A As shown, assuming that in the positive half cycle of the square wave, because an iron swing arm is built into the electromagnetic coil, the axis of the swing arm is in the same direction as the axis of the electromagnetic coil, and the swing arm will be polarized and magnetic under the action of the electromagnetic field. Assuming that the swing arm close to the magnetic pole is polarized to the S pole at this moment, under the principle of repulsion between the same poles and attraction between the opposite poles, the swing arm of the vibration arm assembly will swing in the direction of D1.

[0070] 3. Such as Figure 7C As shown, when the square wave current switches to the negative half cycle, the polarity of the electromagnetic coil power supply is reversed, and the current acting on the electromagnetic coil is opposite to the direction of the positive half cycle. The induced magnetic pole of the swing arm is transformed into the N pole. Similarly, the swing arm of the vibration arm assembly will switch in the opposite direction from D1 to D2 under the action of the new electromagnetic force.

[0071] 4. After completing the current switching of the positive and negative half cycles, the swing of the vibration arm assembly of the motor constitutes a complete vibration cycle. The swing frequency of the vibration arm assembly depends on the frequency of the square wave current of the driving coil. In the embodiment of the present invention, the electromagnetic coil preferably operates at 140Hz-250Hz. The strength of the swing angle of the vibration arm assembly can be adjusted by the duty cycle of the square wave, and the swing angle is proportional to the duty cycle.

[0072] The swing arm 241 is made of ferromagnetic material. Since the operating frequency can be as high as 250 Hz, the swing arm 241 is made of stacked silicon steel sheets with high frequency and low eddy current loss.

[0073] like Fig. 8A As shown, the magnet 27 of the present invention can be two independent magnets M1 arranged to form a magnetic pole, or it can be as shown in FIG. Figure 8B As shown, the same-plane multi-pole magnetization process is adopted, and only one magnet M2 is used to magnetize the N and S poles simultaneously and polarize them in the same plane. The arrangement direction of N and S is consistent with the polarity of the two magnets to meet the requirements of the present invention.

[0074] Among them, the sensorless synchronous drive pulse detection battery voltage technology is adopted, relying on the specific drive pulse cycle to monitor the change of drive current caused by the dynamic impedance change of the motor. Combined with the corresponding algorithm and the monitored motor working conditions, the drive power is compensated in real time to achieve constant swing output.

[0075] The present 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 is a square wave, and the frequency of the square wave is consistent with the output oscillating frequency. Theoretically, when the motor outputs full power 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-driven bridge composed of 4 FETs. The H-bridge changes with the input signal, and the positive and negative voltages at the output end are switched at high speed. Because the FET switching has a response time difference, if the switching is performed at a duty cycle of 100%, the four FETs of the H-bridge will be turned on at the same time, causing an internal short circuit of the H-bridge, resulting in damage to the H-bridge drive. The 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 in this interval. After considering the dead zone, the maximum duty cycle of the final square wave is usually 98% to 99%, not 100%.

[0076] If the duty cycle of the pulse is reduced in the reverse direction, the effective power of the drive will decrease in the reverse direction, so that the swing amplitude of the oscillating motor will decrease accordingly. The mechanism by which the output power can be changed by adjusting the duty cycle of the pulse serves as the theoretical basis for the oscillating motor output rate compensation mentioned in the present invention.

[0077] like Fig. 9 As shown, a typical H-bridge output terminal connected to a pure resistance load voltage signal waveform diagram is shown, in which: S1 is a positive half-cycle effective working pulse, S2 is a negative half-cycle effective working pulse, t12, t22 are respectively positive and negative half-cycle work stop cycles, which include the necessary dead zone control time and the stop time for adjusting the entire pulse duty cycle, t is a complete drive cycle, t=S1+S2+t12+t22; assuming that S1=S2, t12=t22 positive and negative half cycles are completely symmetrical; Duty=S1 / (t12+S1)X100% or Duty=S2 / (t22+S2)X100%, in actual control, by synchronously adjusting the ratio of t12, t22 in the entire pulse t, that is, the duty ratio parameter, the power control of the drive can be achieved. It is obvious that the larger the proportion of t12 and t22 cycles, the smaller the output power. Controlling the output power by adjusting the duty ratio is the theoretical basis of the control technology of the motor of the present invention.

[0078] Before discussing how to implement the motor constant amplitude control theory mentioned in the present invention, the principle and method of collecting power current without additional sensor devices are first explained. Fig.10 As shown, a schematic diagram of the power current acquisition principle without additional sensor devices is shown, wherein BT: represents a battery pack, V inside the battery pack is a standard battery, and R0 is the internal resistance of the battery pack; MCU: is a microprocessor of a line control unit, and the microprocessor contains an analog-to-digital converter marked as ADC and a reference voltage reference source for ADC with an internal mark Vref; S1~S4: are output drive signal ports specially set by the MCU for the H bridge; H: is an H power drive bridge composed of two pairs of complementary FETs; M: is the oscillating motor involved in the present invention; I: is the power current.

[0079] Fig.11 The true values ​​of the four typical working states of the H-bridge are shown.

[0080] Among them, the current sampling required by the constant amplitude technology involved in the present invention has two key points:

[0081] 1. Taking advantage of the internal resistance R0 of the battery pack, during power driving, the changing power current I will inevitably produce a changing voltage drop Vdp at R0. The change in load current can be reflected by detecting Vdp through the MCU control unit, that is, Vdp = R0 XI.

[0082] 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 of power current can be calculated directly without more external designs.

[0083] Unless otherwise specified, the power current change detection discussed in this article is implemented based on the method of detecting the change of R0 voltage drop Vdp.

[0084] The following is divided into two parts to further explain the implementation method and process of constant amplitude compensation.

[0085] The signals of the H-bridge connected to pure resistance load and inductive motor load will show obvious differences, such as Fig.12 As shown in the figure, the solid line CV1 is the waveform of the pure resistance load, and the dotted line is the waveform of the pendulum motor with actual inductive reactance. The obvious difference between these two sets of waveforms is that the peak ringing marked as D appears in each working pulse, and each effective working waveform from the starting point a to the end point b, under the influence of the inductive load, changes from the horizontal line of the standard rectangular square wave to a slope line.

[0086] When the drive end is connected to the motor, the square wave has obvious overshoot and ringing, mainly in the stop cycle (dead zone cycle + power regulation cycle), the motor coil is stopped from being powered, the coil is an inductive load and will generate back electromotive force, and the swing arm will continue to cut the magnetic lines of force generated by the magnet under the action of inertia, forming a variable impedance to the coil. The superposition of the back electromotive force of the coil and the variable impedance on the power supply directly affects the stability of the square wave rising edge and pulse width.

[0087] 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 force lines, and the greater the impact on the variable impedance generated by the coil. Obviously, if the instantaneous current related to the impact of the variable impedance can be measured, the current linear velocity of the swing arm can be relatively mapped, that is, the current relative change in the output swing. This idea is the most important theoretical basis for the real-time swing amplitude measurement involved in the constant amplitude drive technology mentioned in the present invention.

[0088] In order to reduce the impact of electromagnetic interference in stray space on signal detection, the swing-related data detection mentioned in the present invention is not set at the motor drive output end, but directly measures the instantaneous voltage change at the battery end. The voltage change has a mutual mapping relationship with the current change at the motor drive end.

[0089] Fig.13The battery terminal voltage during direct measurement is shown. Under different loads, the oscillating motor exhibits different swing amplitudes and wave clusters. The solid line curve CV1 in the figure is the waveform under no-load conditions, and the dashed line curves CV2, CV3, CV4, and CV5 are the waveforms of loads from small to large. It can be observed that the voltage at the battery terminal changes with the load at a certain timing of each drive pulse. As shown in the attached figure t1-t2 interval, the correlation between the motor load and the voltage can be clearly observed. The heavier the load, the higher the voltage. The rules summarized are:

[0090] Load: CV5>CV4>CV3>CV2>CV1;

[0091] Pulse end voltage: V5>V4>V3>V2>V1.

[0092] Fig.14 The data is displayed in 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 shaft. The heavier the load, the smaller the swing angle of the pendulum shaft.

[0093] V5~V1 are 5 sampling points, and curve a is the curve obtained by connecting the actual sampling points in series. It can be clearly seen from the attached figure that the voltage of the sampling point is strongly correlated with the swing angle under different loads. In order to simplify the calculation amount of the microprocessor, the above sampling data can be fitted with a straight line b using the least squares method.

[0094] The instantaneous voltage change U at the battery end is affected by two important factors, namely U=Ub+Ur, where Ub is the back electromotive force generated by the motor power-off stop cycle, and Ur is the change in the dynamic inductance of the coil caused by the change in the swing amplitude of the vibration arm position. The change in dynamic inductance directly affects the change in the conduction rate of the current in the coil, essentially forming a changing impedance. The change in coil impedance will eventually affect the performance of the rising edge of each pulse at the motor coil end.

[0095] Therefore, as long as the voltage change component caused by the impedance change of the motor at the rising edge of each pulse can be effectively separated, the current motor swing data can be quantified.

[0096] In order to better separate the changing impedance of the motor coil, it is particularly important to select the right sampling point for the current. It can be seen from the wave cluster that, unlike the conventional sampling method, if it is a conventional DC motor working condition, the conventional method is to ignore the pulse synchronization information and continuously perform equidistant and dense sampling. The longer the sampling period, the more stable the value after weighted averaging, which can well reflect the relationship between voltage and load. However, it has been proved that this non-synchronous averaging method is ineffective for brushless motors driven by pulse commutation. The voltage results obtained by continuous sampling without pulse synchronization have no obvious correlation with load changes.

[0097] Fig.15The performance of asynchronous continuous and intensive voltage sampling in brushless motors is demonstrated: in the figure: V axis: voltage scalar, T axis: time scalar, S1~Sn is the timing of asynchronous continuous sampling, t2 is the sampling period, P1~pn is the voltage change periodic signal observed at the battery end. Obviously, the period is related to and synchronized with the motor drive pulse phase, t1 is the motor drive pulse period, and D1~Dn are the sampled voltage values.

[0098] 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 pulse rise and fall positions, where D1 is close to the head of pulse P1 and D5 is close to the tail of pulse P3, and the difference between the two sampling values ​​is large. Therefore, the weighted average method can be used to average the data: that is, Avg = (D1 + D2 + Dn...) / n... The average value Avg does not correctly capture the correct correlation data between load and voltage, so the traditional asynchronous voltage sampling is not suitable for the oscillating motor working condition mentioned in the present invention.

[0099] Fig.16 The performance of voltage data in synchronous sampling mode is shown in the figure: V axis: voltage scalar, T axis: time scalar, S1~Sn is the timing of asynchronous continuous sampling, t2 is the sampling period, P1~pn is the voltage change period signal observed at the battery end, and it is obvious that the period is related and synchronized with the pulse phase. t1 is the motor drive pulse period, and D1~Dn are the sampled voltage values.

[0100] from Fig.16 It can be observed that, if t1 is synchronized with t2, the sampling positions of D1, D2, D3...Dn are consistent with the pulse rise and fall 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 correct correlation data between the load and the voltage. Therefore, synchronous voltage sampling is the preferred current sampling scheme for the oscillating motor mentioned in the present invention.

[0101] Based on the data performance in the above two figures, it is obvious to explain the difference between the traditional simple weighted average current sampling mode and the synchronous sampling. The oscillating motor generally belongs to the category of brushless motors, which are all power pulse drives with high-frequency switching of positive and negative polarity pulses. The sampling mode synchronized with the pulse phase must be used to parse out the current information related to the load.

[0102] After synchronous sampling is adopted, in order to further improve the signal quality, some additional technical means are still needed to filter the back electromotive force signal generated by the unnecessary coil that affects the load current performance.

[0103] In addition to including the dynamic impedance information of the coil, the overcharge amount on the rising edge of the pulse also includes the back electromotive force generated after the coil is powered off. If the information of the overshoot amount on the rising edge of each pulse is directly used to quantify the swing amplitude relationship without considering the superposition effect of the back electromotive force on the signal, the existence of the back electromotive force will more or less reduce the accuracy of the quantitative analysis. In order to eliminate the influence of the back electromotive force on the overshoot amount on the rising edge of each pulse, the H-bridge can be used to momentarily short-circuit the motor coil during each stop cycle of the drive to quickly release the back electromotive force. The embodiment proves that after eliminating the back electromotive force, the motor swing amplitude change can be monitored more sensitively, which improves the signal-to-noise ratio of the signal.

[0104] thus, Fig.17 This 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 two pairs of complementary NP-channel FETs that form an H-bridge as the drive of the oscillating motor, and M is the oscillating motor. Before starting the motor current detection and after the driving power is disconnected, the S1 and S2 inputs are set to a high level, and F1 and F2 enter the cut-off state. The S3 and S4 inputs are also input to a high level, and F3 and F4 are turned on. After F3 and F4 are turned on, 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.

[0105] When the back electromotive force is completely absorbed, S3 and S4 jump to high level and enter the cut-off state, starting the ADC conversion of the MCU for current detection.

[0106] Fig.18 A comparison diagram of the current signal before and after the back EMF of the oscillating motor is eliminated is shown. In the figure: V axis: voltage scalar, T axis: time scalar, P1~P3 show 3 groups of pulse periodic signals, CV1 solid line curve is the voltage curve after the back EMF is eliminated by short-circuit technology, CV2 dotted line curve is the voltage curve affected by the back EMF, Ts is an important area that includes load change information, C is a ringing peak signal that appears when short-circuiting is not used to eliminate the back EMF, and a is an area where the back EMF has a greater impact.

[0107] Since the shaded area marked a is caused by the signal ringing peak generated by the back electromotive force, it has a serious impact on the effective load signal in the Ts interval. After the ringing peak is absorbed by technical means, it has a positive significance for analyzing the load signal.

[0108] Short-circuiting the back-EMF to eliminate it is helpful 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 of short-circuiting the coil current, heat energy will be generated in the coil, causing the coil operating temperature to rise. Whether to use the back-EMF elimination technology or choose a reasonable short-circuit timing can be determined according to the actual application.

[0109] After obtaining effective swing quantification data, the 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, the pulse duty cycle is continuously increased, and the drive power is increased to increase the swing. On the contrary, the duty cycle is continuously reduced, and the drive pulse power is reduced to reduce the swing. By using the above-discussed method to dynamically monitor the swing value in real time and dynamically adjust the pulse drive power, a stable output swing can be obtained under load changes.

[0110] Fig.19 This is a process principle block diagram of the constant amplitude correction technology involved in the present invention. In the specific implementation column, in addition to solving the problem of analyzing the battery voltage change associated with the swing amplitude, it is also necessary to correctly select the appropriate sampling frequency and adjustment frequency, because ADC data acquisition and processing will consume resources, and too dense data sampling will interfere with the stability of the pulse phase of the drive, resulting in phase jitter, and the motor swing shaft will show irregular swing jitter and produce abnormal noise. The density of the pulse duty cycle adjustment also needs to be appropriate, because the motor swing shaft has rotational inertia and has response time domain requirements. Too dense adjustment will weaken the useful amplitude information analyzed, resulting in overshoot, overshoot oscillation, and inability to control normally. Too sparse adjustment will cause the control to be sluggish and delayed, and the compensation effect is not ideal. Generally, the following factors should be considered in actual control:

[0111] 1. Synchronization point with motor signal: The implementation column proves that it is preferable to select sampling before the pulse is about to end, so that the data is most stable and the signal-to-noise ratio is high.

[0112] 2. Start-up back-EMF duration and density: Back-EMF absorption cannot be turned on for every pulse. It should only be enabled before detecting the battery voltage and turned off immediately after the detection is completed. Otherwise, a large amount of heat will be dissipated in the motor coil, causing the motor operating temperature to rise sharply. Similarly, the absorption duration is also a key point in controlling heat, which should be based on the actual situation and the test results.

[0113] 3. Battery voltage sampling: It cannot be performed for every pulse. In the example test of the embodiment, it is better to sample once every 20 pulses. Too intensive sampling will cause phase jitter and abnormal noise in the motor.

[0114] 4. Adjust the duty cycle frequency of the motor drive pulse: It also needs to be reasonable. Too dense correction will cause overshoot oscillation, too sparse compensation will cause slow response, and the swing amplitude will be unstable after load changes.

[0115] Therefore, the control method comprises the following steps:

[0116] Step 1: Synchronously output pulses (which may be the square wave pulses mentioned above);

[0117] Step 2: Start back-EMF absorption;

[0118] Step 3: synchronously collect battery voltage;

[0119] Step 4: Analyze the load-related variables;

[0120] Step 5: Calculate the correction amount;

[0121] Step 6: Correct the drive duty cycle and return to step 1.

[0122] Fig.21 The flowchart of signal processing of the dynamic servo process mentioned in the present invention for obtaining a constant output swing of the motor is shown.

[0123] The steps include:

[0124] Step 1: After the interrupt response, determine whether the 20 pulse intervals are met. If yes, go to step 2, otherwise exit;

[0125] Step 2: Determine whether it is a stop cycle, if yes, go to step 3, otherwise exit;

[0126] Step 3: Start the back electromotive force absorption and determine whether the drive pulse is ended. If yes, go to step 4, otherwise exit;

[0127] Step 4: Collect the battery voltage. If the voltage value is less than the last collected value, go to step 5, otherwise go to step 6;

[0128] Step 5: Increase the duty cycle of the drive pulse and then exit;

[0129] Step 6: Is the voltage value greater than the last collected value? If so, decrease the duty cycle of the drive pulse and exit; otherwise, exit directly.

[0130] The above exit is to directly exit the interrupt response.

[0131] In the embodiment of the present invention, after the system is initialized, the initial pulse duty cycle without compensation is preset to 45%, and the maximum compensation is 98%.

[0132] Fig. 20 The following is a comparison of the swing angle change curves with and without compensation when the load changes, where the ordinate is the swing angle of the swing axis and the abscissa 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.

[0133] It is obvious that the above description and record are only examples and are not intended to limit the disclosure, application or use of the present invention. Although the embodiments have been described in the embodiments and described in the drawings, the present invention is not limited to the specific examples of the teachings of the present invention as the best mode currently considered by the drawings and described in the embodiments, and the scope of the present invention will include any embodiment falling within the previous description and the attached claims.

Claims

1. A constant amplitude high frequency oscillating motor, comprising a motor bracket, an electromagnetic coil, a damping block, a vibration arm assembly, a front cover and a magnet, wherein the front end of the motor bracket is provided with a front cover, the rear end is provided with a magnet, and the rear side of the magnet is further provided with a damping block so as to isolate the vibration of the oscillating motor from the battery at the rear side, characterized in that: An inner hollow cavity is formed in the motor bracket to accommodate the vibration arm assembly, and the rear outer edge of the inner hollow 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 swing arm is a straight iron swing arm and the rear part is located in the electromagnetic coil at the rear of the inner hollow cavity. The front part of the swing arm forms a disc portion and the disc portion is provided with an axial hole for the rotating shaft to pass through. Both ends of the rotating shaft are rotatably supported on the motor bracket through bearings. The rear end of the connecting frame covers 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 vibration arm assembly to the output shaft for output.

2. The constant amplitude high frequency oscillating motor according to claim 1, characterized in that: The swing arm, the rotating shaft and the output shaft are integrally embedded in a connecting frame by secondary plastic injection molding to form a vibration arm assembly. The rotation axis of the rotating shaft and the swing direction of the swing arm are perpendicular to each other, so that the rotating shaft and the swing arm are combined to form a cross shape.

3. The constant amplitude high frequency oscillating motor according to claim 2, characterized in that: 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 integrated 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 according to claim 1, characterized in that: A space is formed between the rear portion of the swing arm and the inner wall of the motor bracket to allow the swing arm to swing back and forth 20 degrees without colliding with the motor bracket.

5. The constant amplitude high frequency oscillating motor according to claim 1, characterized in that: The rear end of the motor bracket forms a step portion for accommodating the magnet so that a gap of at least 0.2-0.6 mm is maintained between the end of the swing arm and the magnet.

6. The constant amplitude high frequency oscillating motor according to claim 1, characterized in that: The front cover at the front end of the motor bracket is provided with a sealing cover to achieve sealing.

7. The constant amplitude high frequency oscillating motor according to claim 1, characterized in that: The swing arm is formed by stacking high-frequency and low eddy-current loss silicon steel sheets.

8. The constant amplitude high frequency oscillating motor according to claim 1, characterized in that: The magnet is composed of two independent magnets arranged in an array or one magnet is used in which the N and S poles are simultaneously magnetized and polarized in the same plane.

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

10. The control method of the constant amplitude high frequency oscillating motor according to claim 9, characterized in that The following steps are included: Step 1: After the interrupt response, determine whether the 20 pulse intervals are met. If yes, go to step 2, otherwise exit; Step 2: Determine whether it is a stop cycle, if yes, go to step 3, otherwise exit; Step 3: Start the back electromotive force absorption and determine whether the drive pulse is ended. If yes, go to step 4, otherwise exit; Step 4: Collect the battery voltage. If the voltage value is less than the last collected value, go to step 5, otherwise go to step 6; Step 5: Increase the duty cycle of the drive pulse and then exit; Step 6: Is the voltage value greater than the last collected value? If so, decrease the duty cycle of the drive pulse and exit; otherwise, exit directly.

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