Ultrasonic motor driver based on push-pull converter preceding stage and linear voltage regulation

Abstract

The invention relates to the technical field of drivers, in particular to an ultrasonic motor driver based on push-pull converter preceding stage and linear voltage regulation, which comprises an upper computer, a master control MCU (Microprogrammed Control Unit), an inversion boost circuit, a resonance boost network, an ultrasonic motor load, a voltage acquisition circuit, a PID (Proportion Integration Differentiation) controller and a preceding stage linear voltage regulation circuit, four MOS tubes are driven to be switched on alternately through an inversion boost circuit, a transformer is connected with a preceding-stage linear voltage regulation circuit, signals are amplified in an equal proportion through a primary winding of the transformer, so that direct-current signals are converted into two high-frequency alternating-current square wave signals with the phase difference of 90 degrees, the signals are subjected to resonance amplification through a resonance boost network after being connected with an ultrasonic motor, and then the signals are output. By adjusting the original signal frequency, the voltage value after resonance boosting meets the driving voltage of the ultrasonic motor, so that the ultrasonic motor is driven, the driver amplifies the driving signal through the preceding-stage linear voltage regulation circuit technology in combination with the push-pull inverter resonance circuit, independent voltage regulation is achieved, and the problem of strong coupling of the frequency and the amplitude in a traditional scheme is solved.

Description

Technical Field

[0001] This invention relates to the field of driver technology, and in particular to an ultrasonic motor driver based on a push-pull converter preamp and linear voltage regulation. Background Technology

[0002] Ultrasonic motors, as a novel type of actuator, are the product of multidisciplinary collaboration, incorporating new technologies from fields such as vibration, tribology, dynamic design, power electronics, automatic control, new materials, and new processes. Compared to traditional electromagnetic motors, they offer advantages not found in traditional electromagnetic motors, including simple structure, small weight, high torque at low speeds, fast response, no electromagnetic interference, and self-locking upon power failure. They are widely used in high-precision technology fields such as aerospace, medical, and defense.

[0003] In ultrasonic motor control systems, the controllable independent variables used to achieve control objectives include three variables: the amplitude of the motor drive voltage, its frequency, and the phase difference between the two phase voltages. For drive control, it is generally desirable for the control variables to be decoupled, meaning that the drive voltage amplitude should remain constant when the frequency is adjusted. However, this is impossible for common series inductive resonant actuators. This is because the voltage amplitude of a series inductive resonant actuator is necessarily related to the drive frequency. Furthermore, due to the unique operating mode of ultrasonic motors, their frequency and amplitude are coupled, and the drive voltage is positively correlated with the motor speed. This causes the frequency resonant point to shift when the temperature rises, resulting in instability in the resonant amplitude and motor speed, and significant voltage changes with frequency variations, which significantly increases the difficulty of motor control.

[0004] In ultrasonic motor speed control methods, frequency modulation, phase modulation, and voltage modulation are commonly used. Currently, variable frequency speed control is most prevalent, but this method has a very limited adjustable frequency range, and the speed change with frequency is severely nonlinear. More importantly, the operating point of an ultrasonic motor is generally chosen near its resonant frequency. When variable frequency speed control is used, the ultrasonic motor's operating frequency will deviate from its operating point, deteriorating the motor's performance and even causing it to stop, thus failing to achieve the desired speed control. As an actuator component, the ultrasonic motor must possess low-speed adjustability, excellent linearity, and convenient forward and reverse rotation control. Therefore, variable frequency speed control alone cannot meet the strong coupling problem between the ultrasonic motor's drive frequency and amplitude. Summary of the Invention

[0005] The purpose of this invention is to provide an ultrasonic motor driver based on a push-pull converter preamplifier and linear voltage regulation, which solves the problem of strong coupling between the driving frequency and amplitude of the ultrasonic motor.

[0006] To achieve the above objectives, the present invention provides an ultrasonic motor driver based on a push-pull converter preamplifier and linear voltage regulation, comprising a host computer, a main control MCU, an inverter boost circuit, a resonant boost network, an ultrasonic motor load, a voltage acquisition circuit, a PID controller, and a preamplifier linear voltage regulation circuit.

[0007] The host computer is connected to the main control MCU. The main control MCU, the inverter boost circuit, the resonant boost network and the ultrasonic motor load are connected in sequence. The main control MCU, the PID controller, the front-stage linear voltage regulation circuit and the inverter boost circuit are connected in sequence. The voltage acquisition circuit is connected to the ultrasonic motor load and the main control MCU respectively.

[0008] The voltage regulation accuracy of the pre-stage linear voltage regulator circuit is within 0.2V.

[0009] The output voltage of the inverter boost circuit is independently adjusted by the preceding linear voltage regulation circuit.

[0010] The resonant boost network is provided by a microcontroller that simultaneously outputs four high-frequency square wave signals: PWMA, PWMB, PWMC, and PWMD. PWMA and PWMB are inverted in pairs, PWMC and PWMD are inverted in pairs, and PWMA and PWMC are 90 degrees out of phase.

[0011] The main control MCU is an STM32 series microcontroller with a 72MHz main frequency, three general-purpose timers, and one advanced timer.

[0012] The general-purpose timer and the advanced timer channel respectively generate two high-frequency pulse signals with a 90° phase difference.

[0013] The aforementioned front-stage linear voltage regulation circuit consists of a BUCK chip circuit and an RC filter circuit. The main control MCU achieves front-stage linear voltage regulation by adjusting the duty cycle of the VPWM signal.

[0014] This invention discloses an ultrasonic motor driver based on a push-pull converter preamplifier and linear voltage regulation. The push-pull inverter boost circuit drives four MOSFETs to alternately switch on and off. The center tap of the transformer is connected to the preamplifier linear voltage regulation circuit. The signal is proportionally amplified by the primary winding of the transformer with the center tap, converting the DC signal into two high-frequency AC square wave signals with a 90-degree phase difference. When connected to the ultrasonic motor, which is equivalent to a resistive-capacitive load, the resonant boost network formed by the driver inductor amplifies the signal. By adjusting the original signal frequency, the boosted voltage meets the driving voltage requirements of the ultrasonic motor, thus driving it. The voltage acquisition circuit acquires the driving voltage in real time, converts it into a digital signal via operational amplifiers, and feeds it back to the microcontroller for processing. The PID controller calculates and adjusts the duty cycle of the preamplifier linear voltage regulation circuit in real time, thereby achieving voltage compensation regulation. The host computer displays the ultrasonic motor's operating status in real time. This driver uses the aforementioned pre-stage linear voltage regulation circuit technology, combined with a push-pull inverter resonant circuit to amplify the drive signal and thus independently regulate the voltage, overcoming the strong coupling problem between frequency and amplitude in traditional solutions. Attached Figure Description

[0015] To make the technical solution and advantages of this application clearer, the embodiments of this application will be described in further detail below.

[0016] The terms "first," "second," "third," and "fourth," etc., used in the specification, claims, and accompanying drawings of this application are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or apparatuses.

[0017] It should be noted that all information (including but not limited to user device information, user personal information, etc.), data (including but not limited to data used for analysis, stored data, displayed data, etc.), and signals involved in this application have been authorized by the user or fully authorized by all parties, and the collection, use, and processing of related data must comply with the relevant laws, regulations, and standards of the relevant countries and regions. For example, the strain data, acceleration data, displacement data, pressure data, and video data involved in this application were all obtained with full authorization.

[0018] Figure 1 This is a connection diagram of an ultrasonic motor driver based on a push-pull converter preamplifier and linear voltage regulation, provided by the present invention.

[0019] Figure 2 This is a schematic diagram of the front-end linear voltage regulator circuit.

[0020] Figure 3 This is a schematic diagram showing the relationship between duty cycle and output voltage.

[0021] Figure 4 This is a schematic diagram of a single-channel push-pull inverter boost circuit.

[0022] Figure 5 This is a schematic diagram of the program design for the driver control signals.

[0023] Figure 6 This is a schematic diagram of an ultrasonic motor-driven physical testing platform.

[0024] Figure 7 (a) is a waveform diagram of the simulation model, and (b) is a waveform diagram of the actual driving circuit oscilloscope.

[0025] Figure 8 This is a graph showing the relationship between duty cycle and amplitude.

[0026] Figure 9 It is a graph showing the relationship between duty cycle and rotational speed.

[0027] In the diagram: 1-Host computer, 2-Main control MCU, 3-Inverter boost circuit, 4-Resonant boost network, 5-Ultrasonic motor load, 6-Voltage acquisition circuit, 7-PID controller, 8-Pre-stage linear voltage regulation circuit. Detailed Implementation

[0028] The embodiments of the present invention are described in detail below. Examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, but should not be construed as limiting the present invention.

[0029] Please see Figures 1 to 9 The present invention provides an ultrasonic motor driver based on a push-pull converter preamplifier and linear voltage regulation, including a host computer 1, a main control MCU 2, an inverter boost circuit 3, a resonant boost network 4, an ultrasonic motor load 5, a voltage acquisition circuit 6, a PID controller 7, and a preamplifier linear voltage regulation circuit 8.

[0030] The host computer 1 is connected to the main control MCU 2. The main control MCU 2, the inverter boost circuit 3, the resonant boost network 4 and the ultrasonic motor load 5 are connected in sequence. The main control MCU 2, the PID controller 7, the front-stage linear voltage regulation circuit 8 and the inverter boost circuit 3 are connected in sequence. The voltage acquisition circuit 6 is connected to the ultrasonic motor load 5 and the main control MCU 2 respectively.

[0031] In this embodiment of the invention, the push-pull inverter boost circuit 3 drives four MOSFETs to switch on alternately. The center tap of the transformer is connected to the front-stage linear voltage regulation circuit 8. The signal is proportionally amplified by the primary winding of the transformer with the center tap, converting the DC signal into two high-frequency AC square wave signals with a 90-degree phase difference. When connected to the ultrasonic motor, since the ultrasonic motor is equivalent to a resistive-capacitive load, the resonant boost network 4, composed of the driving inductor, amplifies the signal through resonance. By adjusting the frequency of the original signal, the voltage value after resonant boosting is made to meet the driving voltage of the ultrasonic motor, thereby driving the ultrasonic motor. The voltage acquisition circuit 6 acquires the driving voltage in real time, converts it into a digital signal through operational amplifiers, and feeds it back to the microcontroller for processing. The PID controller 7 calculates and adjusts the duty cycle of the front-stage linear voltage regulation circuit 8 in real time, thereby achieving voltage compensation regulation. The host computer 1 displays the working status of the ultrasonic motor in real time. This driver, through the front-stage linear voltage regulation circuit 8 technology, combined with the push-pull inverter resonant circuit to amplify the driving signal for independent voltage regulation, overcomes the strong coupling problem between frequency and amplitude in traditional solutions.

[0032] Furthermore, the pre-stage linear voltage regulation circuit 8 utilizes the voltage linear control technology of the chip feedback port (such as... Figure 2 When applied to an ultrasonic motor drive circuit, circuit analysis at point VFB yields the following results:

[0033]

[0034]

[0035]

[0036] From Kirchhoff's current law, we can obtain: .

[0037] in, For the switching node voltage, This is the on-state voltage drop of the switching transistor. The output voltage can be obtained by combining these equations. Duty cycle of input voltage Relationship:

[0038]

[0039] As can be seen from the formula, the output voltage Voltage at FB point (Obtained from the PWM duty cycle after RC filtering) shows a linear relationship. In this scheme, the PWM signal generated by the microcontroller is filtered by an RC low-pass filter to generate an analog voltage. It is then connected to the feedback pin of the power supply chip. The chip's built-in error amplifier adjusts the output voltage based on the superimposed voltage. The duty cycle and output voltage are linearly related.

[0040] The experimentally measured curve showing the relationship between duty cycle and output voltage is as follows: Figure 3 As shown, it has high linearity, voltage regulation accuracy within 0.2V, and internal chip compensation regulation, so the output voltage is stable and not easily affected by other devices. It can stably regulate the driving voltage of the subsequent stage resonance to the ultrasonic motor.

[0041] Furthermore, the pre-amplifier circuit of the resonant boost network 4 simultaneously outputs four high-frequency square wave signals: PWMA, PWMB, PWMC, and PWMD from the microcontroller. PWMA and PWMB are inverted pairwise, as are PWMC and PWMD, with PWMA and PWMC having a 90-degree phase difference. After being amplified by the gate driver chip, the square wave signals control the power MOSFETs in the push-pull inverter circuit, converting the DC signal into an AC square wave which is then applied to the primary side of the transformer.

[0042] In this circuit, PWMA-D is the gate drive signal, generated by the microcontroller. Due to the insufficient drive signal capability of the microcontroller, it must be amplified by the gate drive chip. Vout is the output voltage of the linearly adjustable circuit, used to adjust the duty cycle and amplitude of the resonant voltage. The VPWM signal generated by the microcontroller is filtered by RC and then input to the linearly adjustable circuit described in Section 2.1 to control the amplitude of the primary voltage of the transformer, thereby controlling the drive voltage. The signal is resonantly matched with the capacitive load of the ultrasonic motor through the drive inductor, generating two sinusoidal signals with a 90-degree phase difference to drive the ultrasonic motor. The voltage sampling circuit monitors the drive voltage in real time, and the voltage feedback control can be achieved through the PID controller 7.

[0043] Furthermore, the main control MCU2 is an STM32 series microcontroller with a 72MHz clock frequency, three general-purpose timers, and one advanced timer. The general-purpose timer and the advanced timer channels each generate two high-frequency pulse signals with a 90° phase difference.

[0044] To better understand this technical solution, the following embodiments are provided for further explanation:

[0045] Programming of driver control signals

[0046] To generate two sinusoidal signals with independently adjustable frequency and phase, at the software design level, the four PWM square waves in the front-end are generated by an STM32 series microcontroller, forming two pairs of complementary signals. These signals are then passed through a push-pull inverter resonant boost circuit to generate sinusoidal signals with a 90-degree phase difference. Programming Flow Figure 5 As shown.

[0047] First, the system initializes the timer to up-counting mode (PSC=28, ARR=31) and configures the output comparison mode to level flipping and complementary polarity. Then, it selects two channel combinations based on a flag (1 or 0): if the flag is 1, it sets parameters such as CCR1=22 (high level) and CCR4=2 (low level) to generate a PWM signal with a 90° phase lead; otherwise, it configures parameters such as CCR1=8 (high level) and CCR4=2 (low level) to output a complementary PWM signal with a 90° phase lag. This software design, through precise timer configuration and channel control, achieves the generation of a 90° phase difference between two pairs of complementary square wave signals. This signal provides the foundation for the resonant boost and driving of the ultrasonic motor in subsequent circuits.

[0048] Driver control circuit experimental verification

[0049] Building a Simulink circuit simulation platform

[0050] This model simulates an ultrasonic motor drive system with two independent pre-stage linear voltage regulating circuits 8. This facilitates the research and practical verification of control strategies.

[0051] To study control strategies and verify driver performance, this paper is based on the principle of amplitude modulation speed regulation.

[0052] Building a physical platform

[0053] To verify the rationality of the simulation model, this paper builds a physical actuator test platform, such as... Figure 6 As shown. Based on the calculated ultrasonic equivalent circuit, this paper selects a driving inductance of 1.5mH. To ensure consistency, the actual circuit construction and the simulation model have strictly the same relevant parameters. Experiments have shown that... Figure 7 As shown, the waveform of the simulation model is as follows (e.g.) Figure 7 a) The waveform of the actual driver circuit on the oscilloscope (e.g.) Figure 7 (b) The results are basically consistent and have good sinusoidal properties, further verifying the accuracy and reliability of the simulation model and the theory.

[0054] Driver performance test

[0055] On the physical platform, the input analog voltage VPWM duty cycle and the driver output voltage amplitude (e.g., at different frequencies) of the pre-stage linear voltage regulation circuit 8 were tested. Figure 8 The relationship between ) and motor speed (e.g. Figure 9As shown in the experimental results, the duty cycle of the linear voltage regulation control signal VPWM is negatively correlated with the output voltage amplitude and the motor speed. The speed and resonant voltage differ at different frequencies because the piezoelectric ceramic has a larger amplitude near the resonant point, resulting in a wider amplitude and speed adjustment range and better linearity under the same linear voltage regulation environment. In the working environment, the frequency level can be flexibly set according to the actual required amplitude and speed range to adapt to different working scenarios. Under actual testing, the motor speed response is smooth, the closed-loop control effect is good, and the voltage and speed regulation range is wide and controllable, demonstrating the excellent performance of the drive solution.

[0056] The above-disclosed embodiments are merely preferred embodiments of an ultrasonic motor driver based on a push-pull converter preamplifier and linear voltage regulation, and should not be construed as limiting the scope of this application. Those skilled in the art will understand that all or part of the processes for implementing the above embodiments, and equivalent variations made in accordance with the claims of this application, still fall within the scope of this application.

Claims

1. An ultrasonic motor driver based on push-pull converter front stage and linear voltage regulation, characterized in that, comprising a host computer, a master MCU, an inverter boost circuit, a resonant boost network, an ultrasonic motor load, a voltage acquisition circuit, a PID controller and a front linear voltage regulation circuit; the host computer and the master MCU are connected, the master MCU, the inverter boost circuit, the resonant boost network and the ultrasonic motor load are connected in turn, the master MCU, the PID controller, the front linear voltage regulation circuit and the inverter boost circuit are connected in turn, and the voltage acquisition circuit is connected with the ultrasonic motor load and the master MCU respectively.

2. The ultrasonic motor driver based on push-pull converter front stage and linear voltage regulation according to claim 1, characterized in that, the front linear voltage regulation circuit has a voltage regulation precision within 0.2V, wherein the voltage amplitude of two-phase inverter signals can be independently linearly adjusted through the front linear voltage regulation circuit.

3. The ultrasonic motor driver based on push-pull converter front stage and linear voltage regulation according to claim 1, characterized in that, the resonant boost network is outputted by a single-chip microcomputer with four high-frequency square wave signals PWMA, PWMB, PWMC and PWMD, wherein PWMA and PWMB are opposite to each other, PWMC and PWMD are opposite to each other, and PWMA and PWMC are 90 degrees out of phase.

4. The ultrasonic motor driver based on push-pull converter front stage and linear voltage regulation according to claim 1, characterized in that, the master MCU selects STM32 series single-chip microcomputer, has a 72MHz main frequency, three general-purpose timers and one advanced timer.

5. The ultrasonic motor driver based on push-pull converter front stage and linear voltage regulation according to claim 1, characterized in that, the general-purpose timer and the advanced timer channel respectively generate two high-frequency pulse signals with a phase difference of 90 degrees.

6. The ultrasonic motor driver based on push-pull converter front stage and linear voltage regulation according to claim 1, characterized in that, the front linear voltage regulation circuit comprises a BUCK chip circuit and an RC filter circuit, and the master MCU realizes front linear voltage regulation by adjusting the duty cycle of the VPWM signal.

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