Frequency locking method for dynamically adjusting ultrasonic broach vibration mode driving frequency

Abstract

The invention belongs to the technical field of machining, and particularly relates to a frequency locking method for dynamically adjusting the vibration mode driving frequency of an ultrasonic broach, which comprises the following steps of: designing a hybrid PLL (Phase Locked Loop) system, and calculating a phase difference and accurately adjusting the driving frequency in combination with a digital phase discriminator and a CORDIC (Coordinated Rotation Digital Computer) algorithm; a dual-mode tracking strategy is adopted, a fault protection mechanism is added, and when the system detects that phase mutation exceeds 30 degrees, emergency stop is triggered, and a backup analog filter is automatically switched; by designing an accurate band-pass filter and combining hardware deployment and a dynamic frequency tracking technology, the position of a harmonic peak is detected in real time, and the passband range of the filter is correspondingly adjusted. According to the frequency locking method for dynamically adjusting the ultrasonic broach vibration mode driving frequency, the dynamic driving frequency can be adjusted in real time, it is ensured that the signal is close to the resonant frequency, an ultrasonic auxiliary broaching system is kept in the target vibration mode all the time, accurate control over the broach vibration mode is achieved, and the performance of ultrasonic machining equipment is improved.

Description

Technical Field

[0001] This invention relates to the field of machining technology, and specifically to a frequency locking method for dynamically adjusting the vibration mode drive frequency of an ultrasonic broach. Background Technology

[0002] Broaching, as one of the core technologies in modern high-efficiency precision cutting, has demonstrated outstanding comprehensive advantages in machining complex workpieces with highly repeatable geometric features (such as turbine disk tenons, involute tooth profiles of heavy-duty gears, splined shafts, etc.). Compared with traditional processes such as turning and milling that rely on intermittent cutting, broaching, with its continuous and stable cutting characteristics, has achieved significant improvements in machining accuracy, production efficiency, and cost control in large-scale manufacturing. In recent years, the successful introduction of Ultrasonic Assisted Machining (UAM) technology into the broaching field has injected new vitality into this traditional process. This innovative integration has brought many significant advantages: on the one hand, UAM technology significantly improves the cutting performance of broaching tools, enabling them to remove material more efficiently during machining; on the other hand, it effectively alleviates the extreme loads and wear on the tools, extends tool life, and reduces machining costs. More importantly, the application of UAM technology has greatly broken through the bottlenecks faced by traditional broaching in dealing with high-strength, high-hardness, and visco-tough materials, significantly expanding its material adaptability and machining capabilities. In conclusion, the combination of UAM technology and broaching process has not only brought new development opportunities to the broaching field, but also provided more efficient and reliable processing methods for related industries, thus powerfully promoting the development and progress of the entire manufacturing industry.

[0003] Currently, through in-depth exploration and research by technical personnel, it has been fully verified that using a resonant broach to achieve ultrasonic broaching is a feasible and highly promising method. However, in actual ultrasonic broaching processes, the vibration mode of the broach changes significantly, and the vibration frequency of the broach also drifts with changes in working conditions. These changes severely affect the machining accuracy and efficiency. To solve this problem, this invention aims to provide a dynamic frequency tracking system and method that can adjust the drive frequency signal in real time and dynamically, ensuring that the signal remains stable near the resonant frequency. This allows the ultrasonic-assisted broaching system to always maintain the target vibration mode, significantly improving the machining performance of the ultrasonic broaching machine and enabling it to play a greater role in high-precision and high-efficiency machining. Summary of the Invention

[0004] The purpose of this invention is to overcome the above-mentioned shortcomings of the prior art and provide a frequency locking method for dynamically adjusting the driving frequency of an ultrasonic broach. This method can dynamically adjust the driving frequency to ensure that the signal is near the resonant frequency, so that the ultrasonic-assisted broaching system remains in the target mode shape, thereby improving the machining performance of the ultrasonic broaching machine.

[0005] To achieve the above objectives, the present invention provides a frequency-locking method for dynamically adjusting the driving frequency of an ultrasonic broach, comprising the following operations: S1. Design a PLL system; Design a hybrid PLL (Phase-Locked Loop) system that combines a digital phase detector and the CORDIC algorithm to calculate the phase difference and precisely adjust the drive frequency. Through phase-locked loop (PLL) technology, the frequency of the drive signal can be adjusted in real time to ensure that the drive frequency is always synchronized with the resonant frequency.

[0006] S2. Adopt a dual-mode tracking strategy; To improve frequency tracking efficiency, a dual-mode tracking strategy was designed. During the locking phase, the PLL system quickly locks the frequency in coarse adjustment mode with a step size of 100Hz. In the steady-state phase, it enters fine adjustment mode with a step size of 1Hz to achieve more precise frequency adjustment. This dual-mode tracking strategy not only improves the tracking speed but also ensures that the system maintains high accuracy during long-term operation.

[0007] S3. Add a fault protection mechanism; To prevent system failures, a fault protection mechanism was added. When the PLL system detects a phase change exceeding 30°, it triggers an emergency stop and automatically switches to the backup analog filter. This design effectively improves the reliability of the entire system.

[0008] S4, Adaptive bandwidth adjustment; Under varying loads or environmental conditions, the resonant frequency may shift, necessitating real-time updates to the passband of the bandpass filter. This can be achieved by detecting the position of the resonant peak in real time and adjusting the filter's passband accordingly. By designing a precise bandpass filter, combined with hardware deployment and dynamic frequency tracking technology, efficient signal processing and control can be realized. Both the real-time implementation of the digital filter and the dynamic frequency adaptation mechanism ensure that the system can cope with various frequency changes and interferences in real-world operating environments, providing stable and reliable performance.

[0009] Furthermore, in S1, the PLL system includes a phase detector, a voltage-controlled oscillator (VCO), and a frequency adjustment module. The phase detector is used to compare the phase difference between the current and voltage of the PZT so that the drive frequency can be dynamically adjusted by the VCO to always match the resonant frequency.

[0010] Furthermore, the digital phase detector employs the CORDIC algorithm, which can calculate the phase difference with an accuracy of ±0.1°, thereby significantly improving the tracking accuracy of the PLL system in practical operation. The FPGA (Field Programmable Gate Array) using the CORDIC algorithm effectively avoids the accuracy loss of traditional calculation methods, making the phase difference calculation more precise and ensuring that the system can accurately lock onto the target frequency.

[0011] Furthermore, the PZT driver circuit traces are impedance matched, and 50Ω microstrip lines are used to optimize signal transmission quality.

[0012] Furthermore, a vapor chamber is installed on the FPGA to ensure that its junction temperature is below 85°C.

[0013] Furthermore, the PZT substrate uses AlN ceramic, whose high thermal conductivity effectively reduces the temperature rise of the equipment.

[0014] Furthermore, Fault Tree Analysis (FTA) was employed to identify faults, and countermeasures were developed for each fault mode. FTA not only optimizes the reliability design of the system but also provides a valuable reference for future fault diagnosis and repair.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: The frequency locking method for dynamically adjusting the driving frequency of the ultrasonic broach vibration mode provided by the present invention can adjust the dynamic driving frequency in real time to ensure that the signal is near the resonant frequency, so that the ultrasonic-assisted broaching system always maintains the target vibration mode, realizes precise control of the broach vibration mode, and improves the performance of ultrasonic processing equipment. Attached Figure Description

[0016] Figure 1 This is a flowchart illustrating the dual-mode tracking strategy of the present invention; Figure 2 This is a flowchart illustrating the Fault Tree Analysis (FTA) method. Detailed Implementation

[0017] To make the objectives, technical solutions and advantages of the present invention clearer, descriptions of well-known structures and technologies are omitted in the following description in order to avoid unnecessarily obscuring the concepts in the present invention. Example

[0018] This embodiment provides a frequency locking method for dynamically adjusting the driving frequency of an ultrasonic broach, including the following operations: S1. Design a PLL system; Design a hybrid PLL (Phase-Locked Loop) system that combines a digital phase detector and the CORDIC algorithm to calculate the phase difference and precisely adjust the drive frequency. The PLL technology allows for real-time adjustment of the drive signal frequency, ensuring it remains synchronized with the resonant frequency. The PLL configuration includes a phase detector, a voltage-controlled oscillator (VCO), and a frequency adjustment module. The phase detector compares the phase difference between the current and voltage of the PZT and adjusts the drive frequency via the VCO to maintain consistency with the resonant frequency. The VCO dynamically adjusts the drive frequency to maintain resonance locking. The digital phase detector employs the CORDIC algorithm, enabling phase difference calculation with an accuracy of ±0.1°, significantly improving the system's tracking accuracy in practical applications. The FPGA using the CORDIC algorithm effectively avoids the accuracy loss associated with traditional calculation methods, resulting in more precise phase difference calculations and ensuring accurate target frequency locking.

[0019] S2. Adopt a dual-mode tracking strategy; To improve the efficiency of frequency tracking, a dual-mode tracking strategy was designed. During the locking phase, the system quickly locks the frequency in coarse adjustment mode with a step size of 100Hz. In the steady-state phase, it enters fine adjustment mode with a step size of 1Hz to achieve more precise frequency adjustment. This dual-mode tracking strategy not only improves the tracking speed but also ensures that the system maintains high accuracy during long-term operation.

[0020] S3. Add a fault protection mechanism; To prevent system failures, a fault protection mechanism was added. When the PLL system detects a phase change exceeding 30°, it triggers an emergency stop and automatically switches to the backup analog filter. This design effectively improves the reliability of the entire system.

[0021] We employed Fault Tree Analysis (FTA) to identify potential failure modes and developed countermeasures for each mode. FTA not only helped us optimize the system's reliability design but also provided a valuable reference for future fault diagnosis and repair. S4, Adaptive bandwidth adjustment; Under varying loads or environmental conditions, the resonant frequency may shift, necessitating real-time updates to the passband of the bandpass filter. This can be achieved by detecting the position of the resonant peak in real time and adjusting the filter's passband accordingly. By designing a precise bandpass filter, combined with hardware deployment and dynamic frequency tracking technology, efficient signal processing and control can be achieved. Both the real-time implementation of the digital filter and the dynamic frequency adaptation mechanism ensure that the system can cope with various frequency changes and interferences in real-world operating environments, providing stable and reliable performance.

[0022] In practical applications, the hardware devices used in the method can be optimized. For example, impedance matching can be performed on the traces of the PZT driving circuit, and 50Ω microstrip lines can be used to optimize signal transmission quality. A heat spreader can be added to the FPGA to ensure that its junction temperature is below 85℃. The PZT substrate can be made of AlN ceramic with excellent thermal conductivity, which can effectively reduce the temperature rise of the entire device.

[0023] The above are only some embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various combinations and modifications of the aforementioned technical features. Any improvements, modifications, equivalent substitutions, or applications of the structure or method of the present invention to other fields to achieve the same effect without departing from the spirit and scope of the present invention shall fall within the protection scope of the present invention.

Claims

1. A frequency-locking method for dynamically adjusting the driving frequency of an ultrasonic broach vibration mode, characterized in that, Includes the following operations: S1. Design a PLL system Design a hybrid PLL system that combines a digital phase detector and the CORDIC algorithm to calculate the phase difference and precisely adjust the drive frequency; S2, Employing a dual-mode tracking strategy During the locking phase, the system quickly locks the frequency using a coarse adjustment mode with a step size of 100Hz; during the steady-state phase, it enters a fine adjustment mode with a step size of 1Hz to achieve more precise frequency adjustment. S3, Add fault protection mechanism When the system detects a phase change exceeding 30°, it triggers an emergency stop and automatically switches to the backup analog filter. S4, Adaptive Bandwidth Adjustment By designing precise bandpass filters, combining hardware deployment and dynamic frequency tracking technology, the position of the resonant peak is detected in real time, and the passband range of the filter is adjusted accordingly.

2. The frequency locking method for dynamically adjusting the driving frequency of an ultrasonic broach according to claim 1, characterized in that: In S1, the PLL system includes a phase detector, a voltage-controlled oscillator, and a frequency adjustment module. The phase detector is used to compare the phase difference between the current and voltage of the PZT, and the voltage-controlled oscillator is used to adjust the drive frequency so that it is always consistent with the resonant frequency.

3. The frequency locking method for dynamically adjusting the driving frequency of an ultrasonic broach according to claim 2, characterized in that: The digital phase detector uses the CORDIC algorithm to calculate the phase difference with an accuracy of ±0.1°.

4. The frequency locking method for dynamically adjusting the driving frequency of an ultrasonic broach according to claim 1, characterized in that: The PZT driver circuit traces are impedance matched, and 50Ω microstrip lines are used to optimize signal transmission quality.

5. The frequency locking method for dynamically adjusting the driving frequency of an ultrasonic broach according to claim 1, characterized in that: Install a vapor chamber on the FPGA to ensure its junction temperature is below 85°C.

6. The frequency locking method for dynamically adjusting the driving frequency of an ultrasonic broach according to claim 1, characterized in that: The PZT substrate uses AlN ceramic, whose high thermal conductivity effectively reduces the temperature rise of the device.

7. The frequency locking method for dynamically adjusting the driving frequency of an ultrasonic broach according to claim 1, characterized in that, Also includes: Fault tree analysis (FTA) was used to identify faults, and countermeasures were developed for each fault mode.

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