Traveling wave pulse-based ultrasonic motor strong stiffness driving method and system

Abstract

The application discloses a strong stiffness driving method and system of an ultrasonic motor based on beat wave pulses, sets a beat wave signal frequency difference Delta f, an initial phase difference Psi and periodic time data T1 and T2 of step movement of the ultrasonic motor driven by pulses, at a pulse period 0 to T1 moment, a driving system outputs the set beat wave signal, and the ultrasonic motor moves in a beat wave mode; the driving system is powered off at the T1 moment, the ultrasonic motor moves at low speed and stops moving; the ultrasonic motor keeps a static state at the stop moving to T2 moment; the ultrasonic motor is driven by the beat wave signal again at the T2 moment, i.e. the 0 moment of the next pulse period, so that the ultrasonic motor is driven by pulses based on beat waves, the method is simple and efficient, and the ultrasonic motor can realize strong stiffness, ultralow speed, low noise, high resolution and step movement; meanwhile, the ultrasonic motor beat wave driving system based on FPGA is equipped, and various parameters of the beat wave signal and pulse driving can be adjusted.

Description

Technical Field

[0001] This invention relates to the field of ultrasonic motor stepping motion control technology, specifically to a high-stiffness driving method and system for ultrasonic motors based on beat wave pulses. Background Technology

[0002] Space laser communication is a high-tech method that uses laser beams as carriers for direct information transmission in space, with the primary carrier being a terminal. It boasts significant advantages such as strong anti-interference capabilities, high security, high communication rates, and fast transmission speeds. The coarse tracking process in a space laser communication system requires sending the calculated scanning trajectory and position tracking trajectory to the drive unit to power the coarse tracking control system. This places high demands on the drive unit's control accuracy, speed stability, and response time. Ultrasonic motors, as a novel actuator, rely on the inverse piezoelectric effect of piezoelectric ceramics to excite stator vibration, and then use the friction between the stator and rotor to drive the rotor, thus converting electrical energy into mechanical energy. Due to its unique mechanism, stepper ultrasonic motors have many advantages over traditional electromagnetic stepper motors, such as fast response, low-speed high torque, no electromagnetic interference, and power-off self-locking. Therefore, they have broad application prospects in various fields such as aviation, aerospace, and medicine. However, when using ultrasonic motor pulse drive in high-precision systems such as space laser communication and precision control platform systems, high demands are placed on the accuracy of the drive control system and the stability of the entire system, posing a significant challenge to the pulse drive control of ultrasonic motors.

[0003] Existing ultrasonic motor pulse-driven stepping motion is widely used in engineering applications, offering advantages such as simplicity, speed, and high resolution. However, it suffers from problems including unstable ultrasonic motor drive control and intermittent speed fluctuations caused by continuous pulse operation, leading to rigid impacts and high-frequency noise interference. Therefore, in some special applications, there is an urgent need for an ultrasonic motor pulse-driven method that guarantees high-resolution stepping while also possessing high rigidity, ultra-low speed, and noise-free operation.

[0004] A variable frequency vibration method and vibration actuator (patent number CN1109325977A) that can shorten response time combines a beat wave signal with a novel ultrasonic motor structure, resulting in a vibration actuator with fast response speed. An ultrasonic motor positioning method and drive system based on frequency difference signal control (patent number CN116111876A) utilizes the characteristic of ultrasonic motor deceleration after switching from a normal traveling wave to a beat wave, achieving precise positioning of the ultrasonic motor through micro-stepping compensation after deceleration to a preset position. Neither of the above two different utilization methods of beat waves has solved a series of problems existing in the short-time pulse drive process of ultrasonic motors. This invention utilizes beat wave pulse drive to achieve high stiffness and ultra-low speed stepping motion of ultrasonic motors, representing a novel ultrasonic motor pulse drive method that can ensure continuous low-noise, high-resolution stepping motion of the ultrasonic motor. Summary of the Invention

[0005] In view of this, the present invention provides a method and system for driving ultrasonic motors with high stiffness based on beat wave pulses.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] A high-stiffness driving method for ultrasonic motors based on beat wave pulses, characterized by the following steps:

[0008] Step S1: Based on the stepping requirements of the ultrasonic motor and the timing requirements of the pulse drive, set the frequency difference Δf and the initial phase difference of the beat wave signal driving the ultrasonic motor. And the periodic time data T1 and T2 of the stepping motion;

[0009] Step S2: From time 0 to T1, the frequency difference between the two phases of the driver output is Δf, and the initial phase difference is... Furthermore, a sinusoidal signal with consistent amplitude drives an ultrasonic motor. During this process, the ultrasonic motor first accelerates in the positive direction and then decelerates in the positive direction, which is in the beat wave motion stage.

[0010] Step S3: At time T1, the driver issues a power-off command, and the ultrasonic motor decelerates forward until it stops moving, entering the power-off movement stage;

[0011] Step S4: From the time the ultrasonic motor stops running until time T2, the ultrasonic motor is in a stationary phase;

[0012] Step S5: At time T2, which is the 0th time of the next cycle, the driver outputs the beat wave signal again; repeat steps S2, S3, and S4 to realize the ultrasonic motor pulse drive based on the beat wave.

[0013] Preferably, the feature is that the ultrasonic motor is driven by a beat wave signal, which is a waveform with two phase frequencies that are inconsistent, an initial phase of any value from 0 to 360° and a consistent amplitude, and has the characteristics of both beat waves and traveling waves.

[0014] Preferably, the frequency difference Δf of the beat wave signal needs to be controlled within the range of 0% to 15% of the normal driving frequency of the ultrasonic motor, i.e., 0 < Δf < f. 驱 ×15%; the initial phase difference of the beat wave can be any value from 0 to 360°.

[0015] Preferably, the feature is that: the set time data T1 and T2 are time nodes within one cycle of ultrasonic motor pulse drive; the preset time T1 is the moment when the beat wave signal drive is cut off, that is, the power is turned off, and the preset time T2 is the moment when the cycle ends and also the 0 moment of the next cycle; T1 and T2 need to be set according to the stepping motion requirements.

[0016] Preferably, the feature is that: from time 0 to T1, the ultrasonic motor has a two-phase frequency difference of Δf and an initial phase difference of... Driven by a sinusoidal signal with consistent amplitude, the ultrasonic motor moves in a beat wave motion phase, characterized by initial positive acceleration followed by positive deceleration. From T1 until the ultrasonic motor stops moving, it enters a power-off motion phase, decelerating to a standstill. From T2 until the ultrasonic motor stops moving, it enters a stationary phase, remaining stationary.

[0017] Preferably, the driver for outputting two-phase adjustable frequency and phase-modulated beat wave signals is a DDS signal generator driver system implemented based on FPGA.

[0018] The ultrasonic motor high-rigidity drive system based on beating wave pulses is characterized by the following: the driver includes a control module, a signal generation module, a power amplification module, and a power supply module; the control module uses a host computer to control the output and interruption of the drive signal and adjust the frequency difference of the beating wave; the signal generation module uses an FPGA to implement a DDS signal generator function, outputting a two-phase high-resolution frequency- and phase-modulated sinusoidal digital signal, and uses two high-speed D / A converters to convert the digital signal into an analog signal; the power amplification module includes a preamplifier and a secondary power amplifier to boost the drive signal; the power supply module provides DC power to the FPGA, the D / A converter, and the power amplification module.

[0019] Preferably, the FPGA uses the Cyclone IV series EP4CE10 chip; the preamplifier circuit uses the LF353 operational amplifier; and the power supply module uses a high-precision digital display adjustable 40V 8A programmable regulated power supply with an output power of 320W.

[0020] Preferably, the FPGA implements the DDS signal generator by calling the IP core to instantiate a ROM module and digitizing the required analog signal into the ROM, and by setting the accumulator register to control the frequency of reading the digital signal for signal output.

[0021] The present invention achieves the following technical effects compared to the prior art:

[0022] 1. The method provided by the present invention uses the frequency difference and start-up / stop of the beat wave as the main control elements, which makes the implementation of the entire pulse driving method simple and easy to apply in engineering.

[0023] 2. The method provided by this invention is based on the beat wave theory and has a mature theoretical foundation. It utilizes beat waves to achieve low-noise motion in the stepping motion driven by ultrasonic motor pulses, and reduces the rigid impact on the entire system. At the same time, it has high-resolution stepping, which broadens the application of ultrasonic motors in the engineering field.

[0024] 3. The ultrasonic motor drive system used in the method provided by the present invention utilizes FPGA to implement the DDS signal generator function, so that the two-phase frequency, amplitude and phase of the drive signal can be arbitrarily adjusted and the adjustment resolution is high enough, so as to achieve a more refined output effect of different frequency difference beat wave signals.

[0025] 4. The method provided by the present invention, by designing three stages in the stepping motion of the ultrasonic motor under the drive of the beat wave pulse—the beat wave motion stage, the power-off motion stage, and the stationary stage—achieves the analysis of the motion characteristics of the ultrasonic motor within one pulse cycle; at the same time, it reduces the step distance of the ultrasonic motor within one pulse cycle and improves the stepping resolution.

[0026] 5. The method provided by the present invention, by setting the frequency difference of the traveling wave, the power-off time and the excitation interval, makes the stepping motion within one cycle have the characteristics of sufficiently small speed of the ultrasonic motor and relatively stable motion process when the power is off, avoiding the problem of sudden increase and decrease of speed in normal pulse drive process, ensuring the strong rigidity of ultrasonic motor pulse drive process and achieving the effect of low noise in stepping motion process. Attached Figure Description

[0027] Figure 1 This is a principle block diagram of the ultrasonic motor high stiffness driving method based on beat wave pulses according to the present invention;

[0028] Figure 2 This is a schematic diagram of the starting characteristics of an ultrasonic motor with different initial phase differences, based on the ultrasonic motor high stiffness driving method of the present invention using beat wave pulses.

[0029] Figure 3This is a schematic diagram of the multi-stage implementation of the initial cycle of ultrasonic motor pulse driving, based on the ultrasonic motor high stiffness driving method and system of the present invention.

[0030] Figure 4 This invention relates to a high-rigidity ultrasonic motor driving method and system based on beat wave pulses, and provides a schematic diagram of the ultrasonic motor speed curve for multi-cycle pulse driving of the ultrasonic motor.

[0031] Figure 5 This is a schematic diagram comparing the speed of an ultrasonic motor driven by a pulse for one cycle in the beat wave mode and the normal traveling wave mode, based on the beat wave pulse high stiffness driving method and system of the present invention.

[0032] Figure 6 This is a schematic diagram showing the displacement comparison curves of an ultrasonic motor driven by a pulse for one cycle in the beat wave mode and the normal traveling wave mode pulse driving one cycle of the ultrasonic motor based on the beat wave pulse high stiffness driving method and system of the present invention.

[0033] Figure 7 This is a schematic diagram of the principle of the ultrasonic motor high stiffness drive system based on beat wave pulse of the present invention. Detailed Implementation

[0034] The technical solutions of 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.

[0035] Example

[0036] As described in the background section, existing ultrasonic motor pulse-driven stepping motion is widely used in engineering applications, offering advantages such as simplicity, speed, and high resolution. However, it suffers from problems including unstable ultrasonic motor drive control and intermittent speed fluctuations caused by continuous pulse operation, leading to rigid impacts and high-frequency noise interference. Therefore, this application aims to develop a new ultrasonic motor pulse-driven method that achieves better noise reduction while ensuring more precise stepping distances.

[0037] Figure 1 The diagram shown is a principle block diagram of the ultrasonic motor pulse driving method provided in this application, which includes the following steps:

[0038] Step S1: Based on the stepping requirements of the ultrasonic motor and the timing requirements of the pulse drive, set the frequency difference Δf and the initial phase difference of the beat wave signal driving the ultrasonic motor. And the periodic time data T1 and T2 of the stepping motion.

[0039] The preset frequency difference Δf of the beat wave signal is usually achieved by ensuring that one phase of the drive signal is at its normal drive frequency while increasing the frequency of the other phase. The value of Δf needs to be controlled within the range of 0% to 15% of the normal drive frequency of the ultrasonic motor, i.e., 0 < Δf < f. 驱 ×15%, the specific value of which must be selected to ensure that the speed of the ultrasonic motor remains sufficiently small when the power is cut off during the beat wave phase of the movement under this frequency difference to avoid system impact; the preset time T1 is the time when the beat wave signal drive is cut off, that is, the power is turned off, and the preset time T2 is the time when the cycle ends and also the 0 time of the next cycle.

[0040] The aforementioned frequency difference Δf of the beating wave, when the ultrasonic motor driven by the beating wave reaches a steady state, the ultrasonic motor will... The ultrasonic motor performs a periodic motion that first rotates forward and then reverses. Because the pulse drive time of the ultrasonic motor is extremely short, the vibration of the stator and rotor is still unstable at the start. During this process, the motion cycle of the ultrasonic motor will not strictly follow the reciprocal of the frequency difference to perform forward and reverse motion. Therefore, the selection of the traveling wave frequency difference Δf needs to ensure that when the traveling wave pulse drive is de-energized at this frequency difference, the speed of the ultrasonic motor is small enough to be in the stage of forward deceleration but not yet decelerated to zero.

[0041] Preset initial phase difference of the beat wave The initial motion state of the ultrasonic motor is affected, thus influencing the entire motion process. The motion of the ultrasonic motor driven by a beat wave with an initial phase difference of 0 is achieved in a cyclical manner of "zero – forward acceleration – forward deceleration – zero – reverse acceleration – reverse deceleration – zero," with the period being the reciprocal of the frequency difference between the two phases. To illustrate the relationship between the motor's starting characteristics and the initial phase difference, the following is given: Figure 2 .

[0042] Step S2: From time 0 to T1, the frequency difference between the two phases of the driver output is Δf, and the initial phase difference is... Furthermore, the ultrasonic motor is driven by a sinusoidal signal with consistent amplitude. During this process, the ultrasonic motor first accelerates in the forward direction and then decelerates in the forward direction, which is in the beat wave motion stage.

[0043] Step S3: At time T1, the driver issues a power-off command, and the ultrasonic motor decelerates forward until it stops, entering the power-off movement stage. Since the speed of the ultrasonic motor is already small enough when the power is off, it can ensure that the ultrasonic motor moves smoothly and quickly to a stationary state after the power is off.

[0044] The aforementioned ultrasonic motor speed is sufficiently low when it is turned off, but it cannot be zero or too close to zero. This is because ultrasonic motors have a certain hysteresis. In the very short time after being turned off, the ultrasonic motor will still maintain its original motion state. If the speed is zero or too close to zero when the power is off, the ultrasonic motor will exhibit a rotation phenomenon, which is not conducive to the control of stepping motion and engineering applications.

[0045] Step S4: From the time the ultrasonic motor stops running until time T2, the ultrasonic motor is in a stationary phase;

[0046] Step S5: At time T2, which is the 0th time of the next cycle, the driver outputs the beat wave signal again; repeat steps S2, S3, and S4 to realize the ultrasonic motor pulse drive based on the beat wave.

[0047] from Figure 3 It is known that the beat wave pulse driving process within one cycle includes three stages. The first stage is the beat wave motion stage, in which the ultrasonic motor, driven by the beat wave signal, first accelerates and then decelerates in the forward direction. During this stage, the ultrasonic motor completes most of the step distance within one cycle. The second stage is the power-off deceleration stage, in which the ultrasonic motor gradually decelerates to a stationary state after the power-off command is issued. During this stage, the ultrasonic motor's step distance accounts for a small portion of the total step distance within the entire cycle. These two stages, as the key to the beat wave signal pulse driving, are the focus of this application and represent the entire motion process of the ultrasonic motor within one cycle. The frequency difference Δf of the beat wave signal and the initial phase difference... The pulse drive is crucial. When the cutoff time of the drive signal is fixed, if Δf is too large, it may cause the ultrasonic motor to reverse; if Δf is too small, the ultrasonic motor will rotate too fast when the power is off, resulting in greater impact and noise on the system. Therefore, the values ​​of Δf and T1 need to be determined based on the step size of the pulse drive within one cycle, while the initial phase difference... This will affect the initial motion of the motor. The third stage is the stationary stage, which is the long-interval stage of the stepping motion. The value of T2 mainly depends on the excitation interval of the pulse drive. Generally, the excitation interval of a long-interval pulse is usually greater than 10ms. During this stage, the ultrasonic motor is not excited by any drive signal and remains stationary. Repeating the three stages of stepping motion within one cycle can realize the pulse drive of the ultrasonic motor with a clapping wave. To better illustrate the speed of the ultrasonic motor in different cycles during the entire pulse drive process, this application provides... Figure 4 .

[0048] As the focus of this application, the first and second stages, in order to highlight the characteristics of this application and demonstrate the advantages compared with ultrasonic motor pulse drive schemes driven by normal traveling wave signals, are presented as follows: Figure 5Under the driving force of a traveling wave signal, the ultrasonic motor accelerates forward and then decelerates, finally being powered off when its speed drops to a certain value. After power failure, the ultrasonic motor continues to decelerate until it comes to a standstill. Under the driving force of a normal traveling wave signal, the ultrasonic motor is in a state of forward acceleration with a large acceleration before the power failure signal is issued. However, due to the hysteresis characteristic of ultrasonic motors, after power failure, the ultrasonic motor initially continues to accelerate forward for a very short time before decelerating to zero speed, and there is also a very short period of rotation due to system impact. Comparing the ultrasonic motor pulse drive schemes under the two different modes, it is clear that the pulse drive in the traveling wave mode solves the problem of sudden speed increases and decreases caused by rapid vibration response and power failure in ultrasonic motors driven by normal traveling wave pulses, thus solving the system impact and noise problems in the stepping motion of ultrasonic motors.

[0049] As a feature of this application, the high-resolution stepping of the ultrasonic motor is given... Figure 6 Based on the above description of the ultrasonic motor's motion process in both the beat wave mode and the normal traveling wave mode, it can be seen that, under the same driving time and power-off conditions, the ultrasonic motor in the beat wave mode has higher resolution of stepping motion displacement, shorter time from the start of motion to complete stillness, and smaller acceleration from power-off to stillness, thus exhibiting stronger controllability and maneuverability.

[0050] As the first stage of this application, a beat-wave signal is used to drive an ultrasonic motor, which first accelerates and then decelerates in the forward direction. Regarding the beat-wave's operating mechanism, it is based on the normal traveling wave synthesis theory, consisting of the superposition of two standing waves with similar frequencies and an arbitrary phase difference of 0-360° in space. By changing the frequency and phase differences between the two phases, the waveform exhibits periodic changes in the microscopic form of a forward traveling wave, a standing wave, a reverse traveling wave, and a standing wave. Macroscopically, this manifests as a beat-wave operating direction that is half forward and half reverse, with a period equal to the reciprocal of the frequency difference between the two phases. Its waveform exhibits characteristics of both traveling waves and beat vibrations. Therefore, applying beat-waves to an ultrasonic motor alters its operating mode. When a beat-wave acts, the particles on the stator surface, through formula derivation, still exhibit elliptical motion consistent with the traveling wave drive. The direction of this elliptical motion changes periodically with the reciprocal of the frequency difference between the two driving signals as its period. When a traveling wave acts, the particles on the stator surface, derived from the formula, still exhibit elliptical motion consistent with the wave drive. The direction of this elliptical motion changes periodically with the reciprocal of the frequency difference between the two-phase drive signals. Within each period, the first half is clockwise and the second half is counterclockwise, with the size of the ellipse periodically scaling within each half-cycle. According to the ultrasonic motor driving mechanism, the corresponding clockwise elliptical motion drives the rotor to rotate in the forward direction, and the counterclockwise elliptical motion drives the rotor to rotate in the reverse direction. Since the rotor speed of the ultrasonic motor is proportional to the speed of the stator's elliptical motion, the output speed of the rotor varies sinusoidally, with the period consistent with the period of the elliptical motion direction. Therefore, the first stage utilizes the motion process of the ultrasonic motor accelerating forward and then decelerating forward under the action of the traveling wave, before reaching zero deceleration. By utilizing this theory's unique manifestation in ultrasonic motors, the application of ultrasonic motors in systems such as vibration actuators and precision control positioning platforms can be broadened. However, due to limitations such as crystal oscillator frequency, synchronization, and insufficient chip processing power, traditional drivers can generally only generate a frequency difference of 10Hz between two phase traveling waves, and the initial phase difference cannot be effectively adjusted, thus failing to leverage the advantages of beat waves in ultrasonic motor pulse drives.

[0051] Therefore, the preferred embodiment of this application provides an ultrasonic motor pulse drive system based on FPGA capable of generating beat wave signals. This overcomes the problem of complex frequency difference adjustment in traditional drive systems, while fully utilizing the advantages of FPGA—multiple available modules, high precision, and excellent synchronization—to achieve ultrasonic motor drive frequency difference adjustment to 0.1Hz or even smaller, as well as two-phase phase adjustment. Specifically, as shown... Figure 2As shown, the system includes a host computer, FPGA, D / A digital-to-analog converter, preamplifier circuit, secondary power amplifier, and power supply module. The beating wave signal is generated using a DDS signal generator implemented on the FPGA. The principle is that the FPGA calls an IP core to instantiate a ROM module and digitizes the required analog signal into the ROM. The frequency of the digital signal is controlled by setting an accumulator register for signal output. The FPGA-implemented DDS signal generator consists of two phases, each containing a connected D / A digital-to-analog converter. The sine and cosine current signals generated by each phase's signal generation module are input to matching preamplifier circuits. Each preamplifier circuit is connected to a secondary power amplifier. The power supply module provides DC power to the FPGA, D / A digital-to-analog converter, and preamplifier circuit.

[0052] The frequency, amplitude, phase control words, power-off time, and excitation interval are set and transmitted to the FPGA chip through programming on the host computer. The FPGA uses Altera's Cyclone IV series EP4CE10 chip with a crystal oscillator frequency of 50MHz. The main control chip has a built-in 414Kbit embedded RAM block, and is externally expanded with 256Mbit SDRAM and 64Kbit EEPROM. Since all channels of the FPGA share the PLL clock set by the IP core, it has good synchronization. The D / A converter uses two 3PD5651E DAC series digital-to-analog converters, which are characterized by high performance and low power consumption. Its digital-to-analog conversion bit depth is 10 bits, and its maximum conversion speed is 125MSPS. The FPGA chip receives the control words from the host computer and sends them to its corresponding control word register. Based on accumulation and table lookup, it calls the digitized signals instantiated in the ROM module. After passing through the D / A converter, the digital signals are converted into analog signals, outputting two stable sine and cosine current signals with a frequency difference. The maximum output amplitude is about 500mVp-p. Then continue from Figure 7 As can be seen, the output current signal of approximately 500mVp-p is input to the preamplifier circuit and the secondary power amplifier for two-stage amplification. The power module uses a high-precision digital display adjustable 40V 8A programmable regulated power supply with an output power of 320W to power the FPGA, D / A digital-to-analog converter, and preamplifier circuit. The FPGA and D / A digital-to-analog converter are both powered by 5V, while the preamplifier circuit is powered by 12V.

[0053] This application first sets the frequency difference Δf and the initial phase difference of the beat wave signal of the pulse-driven ultrasonic motor. The system includes periodic time data T1 and T2 for the stepping motion. During a pulse cycle from 0 to T1, the drive system outputs a set beat wave signal, and the ultrasonic motor moves in beat wave mode. At T1, the drive system is powered off, and the ultrasonic motor moves at low speed until it stops. From T1 to T2, the ultrasonic motor remains stationary. At T2, the beginning of the next pulse cycle, the ultrasonic motor is driven again by the beat wave signal, thus achieving beat wave-based pulse drive of the ultrasonic motor. This method is not only simple and efficient but also enables high rigidity, ultra-low speed, low noise, and high-resolution stepping of the ultrasonic motor. Furthermore, it is equipped with an FPGA-based ultrasonic motor beat wave drive system, which allows adjustment of various parameters of the beat wave signal and pulse drive.

[0054] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation on the technical scope of the present invention. Therefore, any minor modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A high-stiffness driving method for ultrasonic motors based on beat wave pulses, characterized in that: Specifically, the following steps are included: Step S1: Based on the stepping requirements of the ultrasonic motor and the timing requirements of the pulse drive, set the frequency difference of the beat wave signal driving the ultrasonic motor. Initial phase difference and periodic time data of stepping motion , ; Step S2: From 0 to At time t, the frequency difference between the two phases of the driver output is The initial phase difference is Furthermore, a sinusoidal signal with consistent amplitude drives an ultrasonic motor. During this process, the ultrasonic motor first accelerates in the positive direction and then decelerates in the positive direction, which is in the beat wave motion stage. Step S3: In At that moment, the driver issues a power-off command, and the ultrasonic motor decelerates forward until it stops moving, entering the power-off movement phase; Step S4: After the ultrasonic motor stops running... At that moment, the ultrasonic motor is in a stationary state; Step S5: In At time 0, which is the start of the next cycle, the driver outputs the beat wave signal again; repeat steps S2, S3, and S4 to realize the ultrasonic motor pulse drive based on the beat wave.

2. The ultrasonic motor high-stiffness driving method based on beat wave pulses according to claim 1, characterized in that: The ultrasonic motor is driven by a beat wave signal. A beat wave is a waveform with two phases of different frequencies, an initial phase of any value from 0 to 360° and the same amplitude. It has the characteristics of both beat waves and traveling waves.

3. The ultrasonic motor high-stiffness driving method based on beat wave pulses according to claim 2, characterized in that: Frequency difference of traveling wave signal It needs to be controlled within the range of 0-15% of the normal driving frequency of the ultrasonic motor, that is... The initial phase difference of the beat wave can be any value from 0 to 360°.

4. The ultrasonic motor high-stiffness driving method based on beat wave pulses according to claim 3, characterized in that: Set time data and The time point within one cycle of the ultrasonic motor pulse drive; preset time The preset time is the moment when the traveling wave signal is driven to cut off, i.e., when the power is turned off. The moment when this cycle ends is also the 0th moment of the next cycle; and It needs to be set according to the needs of stepping motion.

5. The ultrasonic motor high-stiffness driving method based on beat wave pulses according to claim 4, characterized in that: 0 to At time , the ultrasonic motor has a frequency difference of between the two phases. The initial phase difference is Furthermore, the motion is driven by a sinusoidal signal with consistent amplitude, and it is in the beat wave motion stage, with the motion being first positive acceleration and then positive deceleration; The ultrasonic motor stops moving; during the power-off phase, the ultrasonic motor decelerates forward until it comes to a stop. At any given moment, the ultrasonic motor is in a stationary phase, remaining stationary.

6. The ultrasonic motor high-stiffness driving method based on beat wave pulses according to claim 5, characterized in that: The driver that outputs a two-phase adjustable frequency and phase-modulated beat wave signal is a DDS signal generator driver system implemented based on FPGA.

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