Ultrasonic motor micro-driver based on self-excitation oscillation principle and use method thereof

Abstract

This invention relates to the field of ultrasonic motor drive technology, and discloses a micro-driver for an ultrasonic motor based on the principle of self-excited oscillation and its usage method. The driver includes: an amplification circuit module, comprising a voltage series negative feedback amplification circuit composed of integrated operational amplifiers, the output of which is connected to a feedback network via an inductor; a temperature compensation module, which directly senses temperature changes through the equivalent circuit of the ultrasonic motor and dynamically adjusts circuit parameters; and a frequency selection network module, composed of three impedance elements, which are respectively connected to the temperature compensation module, the amplification circuit module, and the feedback network module. By utilizing the self-excited oscillation principle and the feedback characteristics of the ultrasonic motor, a complex external frequency tracking loop is eliminated, simplifying and miniaturizing the circuit design. The temperature compensation module automatically adjusts the driving frequency, achieving adaptability to resonant frequency drift. Optimized feedback network reduces power consumption and improves driving efficiency.

Description

Technical Field

[0001] This invention relates to the field of ultrasonic motor drive technology, specifically to a micro-driver for ultrasonic motors based on the principle of self-excited oscillation and its usage. Background Technology

[0002] With the widespread application of ultrasonic motors in precision control, their driving technology has become a key research area. Traditional ultrasonic motor driving technology typically relies on external resonant circuits. By generating pulse signals of a specific frequency and applying them to both ends of the motor, the microscopic vibration of the stator is converted into macroscopic rotation of the rotor through friction between the piezoelectric stator and rotor, thus achieving the driving function. This technology has important applications in medical equipment, industrial automation, and aerospace.

[0003] However, in practical applications, temperature changes can cause the resonant frequency of ultrasonic motors to drift. Traditional methods require the addition of an extra frequency tracking circuit, which not only complicates the design of the drive circuit but also limits the miniaturization and integration of the driver. On the other hand, traditional drivers rely on fixed amplitude signals, making it difficult to maintain the stability of the drive signal under dynamic load and temperature changes, resulting in low operating efficiency and reliability. In addition, the frequency adjustment response of existing external resonant circuits is slow, making it difficult to meet the requirements of rapidly changing environments and significantly limiting their applicability in high-precision and multi-condition environments. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a micro-driver for an ultrasonic motor based on the principle of self-excited oscillation and its usage method, which solves the problems of frequency drift, complex design, and unstable signal caused by temperature changes and load fluctuations in existing technologies.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a micro-actuator for an ultrasonic motor based on the principle of self-excited oscillation and a method for using it, comprising:

[0006] The amplifier circuit module consists of a voltage series negative feedback amplifier circuit composed of an integrated operational amplifier, and its output is connected to the feedback network through an inductor.

[0007] The temperature compensation module directly senses temperature changes through the equivalent circuit of the ultrasonic motor and dynamically adjusts the circuit parameters.

[0008] The frequency selection network module consists of three impedance elements, which are respectively connected to the temperature compensation module, the amplification circuit module and the feedback network module, and are used to dynamically adjust the frequency of the drive signal to match the resonant frequency of the ultrasonic motor.

[0009] The feedback network module contains at least two diodes pointing in opposite directions, forming a dynamic stability control loop for the signal amplitude.

[0010] Preferably, the temperature compensation module is composed of the equivalent circuit of the ultrasonic motor, which is composed of a first resistor and a first capacitor connected in parallel. Its impedance changes with temperature, which directly affects the parameter adjustment of the frequency selection network.

[0011] Preferably, the frequency-selective network module includes:

[0012] The first part of the impedance consists of a first resistor and a first capacitor connected in parallel, with one end connected to the temperature compensation module and the other end connected to the second capacitor.

[0013] The second part of the impedance is formed solely by the second capacitor.

[0014] The third impedance consists of a third resistor and a third capacitor connected in parallel.

[0015] Preferably, the output frequency f of the frequency selective network o Satisfy the following formula:

[0016]

[0017] in:

[0018] L is the inductance value between the amplifier circuit and the frequency selection network;

[0019] C eq It is the equivalent capacitance, affected by the equivalent impedance of the ultrasonic motor temperature compensation module.

[0020] Preferably, the feedback network module includes:

[0021] A nonlinear control circuit formed by two diodes connected in parallel with opposite directions;

[0022] The second resistor and the fourth resistor are connected in series and then connected in parallel to the diode circuit.

[0023] The feedback gain is adjusted by a resistor to a factor greater than 3 during the initial stage of oscillation. After the oscillation stabilizes, the amplitude of the feedback signal is limited by the conduction of a diode.

[0024] Preferably, the amplifier circuit module includes:

[0025] An integrated operational amplifier has its non-inverting input connected to a frequency selection network, its inverting input connected to a feedback network, and its output connected to the feedback network via an inductor.

[0026] The amplifier circuit module is designed with dual power supplies, with equal positive and negative voltages, to provide symmetrical output signals.

[0027] The method for using a micro-actuator for an ultrasonic motor based on the principle of self-excited oscillation includes the following steps:

[0028] The drive signal is amplified using the amplifier circuit module of the driver;

[0029] The temperature compensation module senses the temperature change of the ultrasonic motor and adjusts its equivalent impedance.

[0030] The frequency selection network dynamically adjusts the drive signal frequency based on the feedback signal provided by the temperature compensation module.

[0031] The feedback network adjusts the amplitude and stability of the oscillation signal and outputs a drive signal that matches the resonant frequency of the ultrasonic motor.

[0032] Preferably, the dynamic response time of the temperature compensation module in adjusting the drive signal frequency is 1ms to 10ms.

[0033] Preferably, in the feedback network, the amplitude of the oscillation signal is controlled by adjusting the conduction voltage of the diode, so that the total harmonic distortion rate of the output signal is less than 1%.

[0034] Preferably, the frequency range of the driving signal is between 20kHz and 40kHz, and the amplitude of the output signal is stable within the range of 3V to 12V.

[0035] This invention provides a micro-actuator for an ultrasonic motor based on the principle of self-excited oscillation and its usage method. It has the following beneficial effects:

[0036] 1. This invention utilizes the equivalent circuit of an ultrasonic motor as a temperature compensation module, which can sense the influence of ambient temperature and internal motor temperature rise on the resonant frequency in real time. It also dynamically adjusts the drive signal frequency through a self-excited oscillation circuit to ensure that it always matches the motor's resonant frequency. Compared with traditional methods that rely on external temperature control or independent tracking circuits, this invention does not require additional sensors or complex circuit designs, which greatly improves the adaptability and accuracy of the driver and enables stable operation in various temperature environments.

[0037] 2. This invention introduces the self-excited oscillation principle into the design of ultrasonic motor drivers. Through the organic combination of frequency selection network and feedback network, the automatic frequency tracking function is directly realized without the need for additional design of resonant frequency tracking circuit or compensation control module. This design significantly reduces the number of circuit components, reduces system complexity, and makes the driver smaller, making it more suitable for highly integrated and miniaturized application scenarios, such as medical equipment, precision instruments and other space-sensitive fields.

[0038] 3. This invention optimizes the nonlinear control mechanism in the feedback network and utilizes the synergistic effect of diodes and resistors with opposite directions to ensure that the amplitude of the drive signal remains stable in a dynamic environment. This avoids the phenomenon of signal amplitude runaway when the traditional driver experiences temperature fluctuations or load changes. In addition, the self-excited oscillation mechanism achieves precise matching between the drive signal frequency and the motor resonant frequency, significantly improving energy utilization and stabilizing the drive efficiency at over 90%. Compared with traditional drivers, this invention significantly reduces energy consumption and improves operational reliability. Attached Figure Description

[0039] Figure 1 This is the circuit diagram of the present invention. Detailed Implementation

[0040] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] Please see the appendix Figure 1 This invention provides a micro-driver for an ultrasonic motor based on the principle of self-excited oscillation, including an amplifier circuit module, a temperature compensation module, a frequency selection network module, and a feedback network module.

[0042] 1. Overall structure of the driver

[0043] Amplifier circuit module

[0044] The amplifier circuit module consists of an integrated operational amplifier, adopts a voltage series negative feedback structure, and is powered by dual power supplies (the positive and negative power supply pins are connected to equal positive and negative voltages respectively).

[0045] The non-inverting input of the integrated operational amplifier is connected to the frequency selection network, the inverting input is connected to the feedback network, and the output is connected to the feedback network through the inductor L. This is used to amplify the sinusoidal excitation signal and provide stable driving energy for oscillation.

[0046] Temperature compensation module

[0047] The temperature compensation module consists of the equivalent circuit of the ultrasonic motor, which is a loop of the first resistor (R1) and the first capacitor (C1) connected in parallel. When the motor runs and causes the temperature to rise, its equivalent impedance (including resistance and capacitance) drifts with the temperature change.

[0048] The temperature compensation module applies dynamic changes in equivalent parameters to the frequency selection network and the feedback network, thereby achieving real-time matching between the drive signal frequency and the motor resonant frequency.

[0049] Frequency Selective Network Module

[0050] The frequency selection network module consists of three parts:

[0051] The first part (Z1) consists of a temperature compensation module (parallel circuit of R1 and C1) and a second capacitor (C2). One end of the capacitor is connected to the output of the amplifier circuit, and the other end is connected to the non-inverting input of the integrated operational amplifier.

[0052] The second part (Z2) consists of a separate second capacitor (C2) used to further adjust the signal frequency;

[0053] The third part (Z3) consists of a third resistor (R3) and a third capacitor (C3) connected in parallel. One end of the third part is connected to the non-inverting input of the operational amplifier, and the other end is grounded.

[0054] The frequency selection network dynamically adjusts the drive signal frequency according to the change of the motor's equivalent impedance, so that it is consistent with the motor's resonant frequency.

[0055] Feedback network module

[0056] The feedback network consists of two diodes (D1, D2) in opposite directions connected in parallel with a second resistor (R2), and connected in series with a fourth resistor (R4).

[0057] In the initial stage of oscillation, due to the small signal strength, all diodes are open, and the feedback gain is jointly controlled by R2 and R4, ensuring an amplification factor greater than 3 and rapid oscillation. After the oscillation stabilizes, one diode conducts, R2 is short-circuited, and the amplification factor is limited to the set range, ensuring stable amplitude of the output signal.

[0058] 2. Working principle of the driver

[0059] Oscillation generation and frequency tracking

[0060] The driver generates the drive signal through self-excited oscillation. The ultrasonic motor is both the receiver and the participant in the feedback signal. In the initial stage of oscillation, the amplifier circuit and the frequency selection network work together to guide the frequency of the drive signal to close to the resonant frequency of the motor.

[0061] When temperature changes during motor operation cause the resonant frequency to drift, the equivalent impedance of the temperature compensation module changes accordingly. The frequency selection network dynamically adjusts its impedance value to follow the change of the resonant frequency in real time, ensuring that the drive signal is always consistent with the motor's resonant frequency.

[0062] Dynamic control of signal amplitude

[0063] The feedback network adjusts the signal amplitude through the nonlinear characteristics of the diode. When the signal is small, the diode is off, the feedback gain is large, and the oscillation condition is quickly reached; when the signal amplitude increases to a set threshold, the diode turns on, limiting the feedback gain, ensuring the stability of the output signal amplitude, and avoiding overshoot or distortion.

[0064] 3. Core parameters and formula limitations of the driver

[0065] During the driving process, the frequency f of the driving signal o The following formula relationship must be satisfied:

[0066]

[0067] in:

[0068] L is the inductance value, used for energy storage and oscillation stabilization;

[0069] C eq The equivalent capacitance represents the dynamic capacitance value determined by the temperature compensation module (R1 and C1 in parallel) and other impedance components in the frequency selection network.

[0070] Equivalent capacitance C eq The calculation formula is:

[0071]

[0072] C1 and C2 are the values ​​of the relevant capacitors in the temperature compensation module and the frequency selection network, respectively.

[0073] The amplitude V of the driving signal o Controlled by the feedback network, its upper limit is determined by the following formula:

[0074]

[0075] Where V th This is the forward voltage of the diode.

[0076] 4. Optimized design and effects of the driver

[0077] With the above design, this driver has the following advantages:

[0078] Automatic frequency tracking: No additional frequency tracking circuit is required; dynamic frequency adjustment is achieved directly through the temperature compensation module and frequency selection network.

[0079] Miniaturization and high integration: All core modules are integrated into a compact circuit, making it suitable for miniaturized applications.

[0080] High precision and high stability: frequency error is less than 1%, and output signal harmonic distortion rate is less than 1%.

[0081] Adaptable to various temperature environments: The temperature compensation module can operate normally within the range of -20℃ to 80℃, ensuring the ability to track the resonant frequency.

[0082] 5. How to use the driver

[0083] Step 1: Connect the amplifier circuit module of the driver to the ultrasonic motor via a dual power supply.

[0084] Step 2: When the motor is initially running, use an amplifier circuit and a frequency selection network to quickly establish an oscillation signal.

[0085] Step 3: As the motor operating temperature changes, the temperature compensation module senses and dynamically adjusts the parameters of the frequency selection network to ensure that the drive signal frequency automatically tracks the resonant frequency.

[0086] Step 4: Once the amplitude of the feedback network control signal is stable, the output drive signal acts on both ends of the motor, driving the motor to operate at the optimal frequency.

[0087] Example 1: Stability test of driving frequency under fixed temperature environment

[0088] Objective: To verify the stability of the driver's drive frequency under constant temperature conditions.

[0089] Specific steps:

[0090] Step 1: At room temperature (25°C), connect the driver to a circuit with a resonant frequency f. res =25kHz ultrasonic motor.

[0091] Step 2: The driver is powered by a dual power supply with a positive and negative voltage of ±12V.

[0092] Step 3: Set the diode threshold voltage in the feedback network to 0.7V, the second resistor R2 = 10kA, and the fourth resistor R4 = 30kΩ.

[0093] Step 4: Monitor the driving frequency f using a frequency meter. t The changes were recorded, and the frequency fluctuation range within 10 minutes was recorded.

[0094] Process parameters:

[0095] Inductance L = 10mH, equivalent capacitance G = 0.01μF, feedback gain G = 3.

[0096] Drive signal amplitude V o =6V o =6V o .

[0097] Comparative Example 1: Using a traditional external resonant circuit to drive an ultrasonic motor, the frequency stability under the same working conditions was tested.

[0098] Example 2: Frequency tracking capability under dynamic temperature changes

[0099] Objective: To test the driver's frequency auto-tracking performance under temperature variation conditions.

[0100] Specific steps:

[0101] Step 1: Connect the driver to the ultrasonic motor and set the initial resonant frequency f of the motor. res =30kHz.

[0102] Step 2: Gradually increase the ambient temperature from 20℃ to 80℃ at a heating rate of 10℃ / min.

[0103] Step 3: The equivalent impedance in the temperature compensation module is R1 = 2kΩ, C1 = 0.02μF; the frequency selection network parameters are C2 = 0.015μF, C3 = 0.01μF.

[0104] Step 4: Record the driver output frequency f using a real-time frequency measurement device. o With the resonant frequency f of the motor res The deviation.

[0105] Process parameters:

[0106] Drive signal amplitude V o =8V, feedback gain initially set to 3 times.

[0107] Comparative Example 2: Using a conventional driver with external temperature compensation, the frequency tracking capability under the same operating conditions was tested.

[0108] Example 3: Stability Tests Under Different Load Conditions

[0109] Objective: To verify the frequency and amplitude stability of the driver under different load conditions.

[0110] Specific steps:

[0111] Step 1: Connect the driver to an ultrasonic motor with a load range of 10g to 50g.

[0112] Step 2: Set the initial resonant frequency f res =35kHz, driver operating voltage ±15V, frequency selection network parameters Z1=2kΩ||0.02μF, Z2=0.02μF, Z3=3kΩ||0.01μF.

[0113] Step 3: Gradually increase the load by 10g each time, and monitor the drive frequency f. o and signal amplitude V o .

[0114] Step 4: Record the frequency drift and amplitude changes.

[0115] Process parameters:

[0116] The inductance L = 8mH and the maximum amplitude of the drive signal is 10V.

[0117] Comparative Example 3: The characteristics of the drive signal under load changes were tested using a traditional resonant drive circuit.

[0118] Comparative experimental design

[0119] Target:

[0120] The test examines the frequency tracking capability, amplitude stability, and efficiency of the self-excited oscillation-based driver under different temperature and load conditions, highlighting the advantages of the invention compared to traditional drivers.

[0121] Experimental plan:

[0122] Experimental conditions:

[0123] Ambient temperature range: 20℃-80℃.

[0124] Load range: 10g-50g.

[0125] Test duration: 10 minutes per set of conditions.

[0126] Experimental data recording:

[0127] Frequency deviation (f) o -f res ).

[0128] Amplitude change (ΔV) o ).

[0129] Drive efficiency

[0130] Experimental data table:

[0131]

[0132]

[0133] According to the table: the frequency deviation of the driver of the present invention is controlled within ±3, which is far superior to the traditional driver (the deviation is as high as 20Hz); under dynamic temperature and load conditions, the signal amplitude change of the present invention is controlled within ±0.1V, while the amplitude fluctuation of the traditional driver is large; the driving efficiency of the present invention is generally higher than 90%, which is significantly better than the traditional driver.

[0134] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An ultrasonic motor micro-driver based on the principle of self-excitation oscillation, characterized in that, include: The amplifier circuit module consists of a voltage series negative feedback amplifier circuit composed of an integrated operational amplifier, and its output is connected to the feedback network through an inductor. The temperature compensation module directly senses temperature changes through the equivalent circuit of the ultrasonic motor and dynamically adjusts the circuit parameters. The frequency selection network module consists of three impedance elements, which are respectively connected to the temperature compensation module, the amplification circuit module and the feedback network module, and are used to dynamically adjust the frequency of the drive signal to match the resonant frequency of the ultrasonic motor. The feedback network module contains at least two diodes pointing in opposite directions, forming a dynamic stabilization control loop for the signal amplitude; The temperature compensation module is composed of the equivalent circuit of the ultrasonic motor, which is composed of a first resistor and a first capacitor connected in parallel. Its impedance changes with temperature, which directly affects the parameter adjustment of the frequency selection network. The frequency-selective network module includes: The first part of the impedance consists of a first resistor and a first capacitor connected in parallel, with one end connected to the temperature compensation module and the other end connected to the second capacitor. The second part of the impedance is formed solely by the second capacitor. The third impedance consists of a third resistor and a third capacitor connected in parallel. Output frequency of the frequency selective network satisfies the following equation: ; in: L is the inductance value between the amplifier circuit and the selective network; The equivalent capacitance is affected by the equivalent impedance of the temperature compensation module of the ultrasonic motor.

2. The ultrasonic motor micro-driver based on the self-excitation oscillation principle according to claim 1, characterized in that, The feedback network module includes: A nonlinear control circuit formed by two diodes connected in parallel with opposite directions; The second resistor and the fourth resistor are connected in series and then connected in parallel to the diode circuit. The feedback gain is adjusted by a resistor to a factor greater than 3 during the initial stage of oscillation. After the oscillation stabilizes, the amplitude of the feedback signal is limited by the conduction of a diode.

3. The ultrasonic motor micro-driver based on the self-excitation oscillation principle according to claim 1, characterized in that, The amplifier circuit module includes: An integrated operational amplifier has its non-inverting input connected to a frequency selection network, its inverting input connected to a feedback network, and its output connected to the feedback network via an inductor. The amplifier circuit module is designed with dual power supplies, with equal positive and negative voltages, to provide symmetrical output signals.

4. A method for using a micro-actuator for an ultrasonic motor based on the principle of self-excited oscillation, as described in any one of claims 1-3, characterized in that... Includes the following steps: The drive signal is amplified using the amplifier circuit module of the driver; The temperature compensation module senses the temperature change of the ultrasonic motor and adjusts its equivalent impedance. The frequency selection network dynamically adjusts the drive signal frequency based on the feedback signal provided by the temperature compensation module. The feedback network adjusts the amplitude and stability of the oscillation signal and outputs a drive signal that matches the resonant frequency of the ultrasonic motor.

5. The method of using a micro-driver for an ultrasonic motor based on the principle of self-excitation oscillation according to claim 4, characterized in that, The temperature compensation module adjusts the dynamic response time of the drive signal frequency from 1ms to 10ms.

6. The method of using a self-oscillating principle based ultrasonic motor micro-driver according to claim 4, wherein, The feedback network controls the amplitude of the oscillation signal by adjusting the conduction voltage of the diode, so that the total harmonic distortion rate of the output signal is less than 1%.

7. The method of using a self-oscillating principle based ultrasonic motor micro-driver according to claim 4, wherein, The frequency range of the drive signal is between 20kHz and 40kHz, and the amplitude of the output signal is stable within the range of 3V to 12V.

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