Ultrasonic fuzzy control device based on fuzzy control and electric admittance feature tracking

Abstract

The invention discloses an ultrasonic fuzzy control device based on fuzzy control and electrical admittance feature tracking, which comprises a signal acquisition module, a fuzzy control module, a digital frequency synthesis module, a power driving module, an execution module and a feedback regulation module, and all the modules are electrically connected in sequence to form a closed-loop control loop. The signal acquisition module comprises a voltage sensor, a current sensor and an electric admittance detection unit; the fuzzy control and DDS technology are combined, the frequency control precision reaches + / -0.0745 Hz, the frequency control precision is remarkably improved, the frequency control precision is far beyond the level of + / -20 Hz of domestic like products and is close to and superior to the index of + / -1.0 Hz of foreign products, and resonant frequency drift is effectively avoided; meanwhile, according to the fuzzy control strategy based on the electrical admittance characteristics, different load characteristics can be adapted without adjusting parameters on site, the load adaptability is high, the problem that large and small loads are difficult to consider in traditional PID control is solved, and the system stability is improved.

Description

Technical Field

[0001] This invention relates to ultrasonic welding technology, and in particular to an ultrasonic fuzzy control device based on fuzzy control and electrical admittance feature tracking. Background Technology

[0002] Ultrasonic plastic welding technology, with its advantages of high efficiency, high quality, and energy saving, is widely used in automobile manufacturing, 3C electronics, and other fields. Its core principle is to generate high-frequency vibrations through an ultrasonic generator, which are then transmitted to the welding head via a transducer and amplitude converter to achieve the welding of plastic workpieces.

[0003] The control technology of existing ultrasonic welding equipment has obvious defects: domestic products mostly use traditional PID control, which is difficult to cope with the wide distribution of load characteristics in ultrasonic systems. A single set of parameters cannot be adapted to both high and low load working scenarios, which can easily lead to system detuning and reduce welding reliability; the frequency tracking accuracy is low, the traditional phase tracking method has a slow dynamic response, is greatly affected by changes in ambient temperature and workpiece material, and the resonant frequency drift problem is prominent; the amplitude control accuracy is insufficient, resulting in quality problems such as uneven welding strength and excessive flash; at the same time, advanced foreign control technology monopolizes the market, and domestic products lag significantly behind in key indicators such as frequency accuracy and tracking speed, lacking market competitiveness.

[0004] These problems directly affect welding efficiency, product quality, and equipment lifespan, hindering the industrial application and upgrading of domestically produced ultrasonic welding equipment. Therefore, it is necessary to study a solution to address these issues. Summary of the Invention

[0005] In view of this, the present invention addresses the deficiencies of the existing technology, and its main objective is to provide an ultrasonic fuzzy control device based on fuzzy control and electrical admittance feature tracking, which can achieve accurate and rapid tracking of resonant frequency and high-precision control of amplitude, thereby improving welding stability and adaptability.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: An ultrasonic fuzzy control device based on fuzzy control and electrical admittance feature tracking includes a signal acquisition module, a fuzzy control module, a digital frequency synthesis module, a power drive module, an execution module, and a feedback adjustment module. Each module is electrically connected in sequence to form a closed-loop control circuit. The signal acquisition module includes a voltage sensor, a current sensor, and an admittance detection unit; the voltage sensor, current sensor, and admittance detection unit are used to acquire the voltage signal, current signal, and admittance characteristic parameters of the transducer, and convert the analog signal into a digital signal. The fuzzy control module has a built-in fuzzy controller and a PID control unit. The fuzzy controller is electrically connected to the signal acquisition module, and the PID control unit is electrically connected to the fuzzy controller. The fuzzy controller uses the system output, output error, error change, and electrical admittance characteristic parameters as fuzzy variables, and outputs control commands after fuzzification, rule reasoning, and defuzzification. The digital frequency synthesis module is electrically connected to the fuzzy control module. The digital frequency synthesis module uses DDS technology to generate a digital sine wave signal according to the frequency control command of the fuzzy control module. The power drive module includes a PPC power factor correction circuit and an inverter; the inverter is electrically connected to the PPC power factor correction circuit, and the inverter is also electrically connected to the PID control unit and the digital frequency synthesis module. The power drive module amplifies the signal output by the digital frequency synthesis module and provides stable drive power to the execution module. The execution module consists of a transducer, an amplitude transformer, and a welding head. The transducer is electrically connected to a voltage sensor, a current sensor, and an admittance detection unit. The transducer converts electrical signals into mechanical vibrations, which are amplified by the amplitude transformer and then transmitted to the workpiece through the welding head. The feedback adjustment module is electrically connected to the execution module, the signal acquisition module, and the fuzzy control module. The feedback adjustment module collects the vibration frequency, amplitude, and welding head temperature signals of the execution module in real time and feeds them back to the signal acquisition module and the fuzzy control module.

[0007] As a preferred embodiment, the control cycle of the fuzzy controller is one vibration cycle, distributed over 28 μs. The fuzzy variable domain includes frequency deviation, amplitude deviation, conductivity, and susceptance. The frequency deviation is -10 Hz to 10 Hz, the amplitude deviation is -5 μm to 5 μm, the conductivity is 0 to 5 S, and the susceptance is -5 S to 5 S.

[0008] As a preferred embodiment, the digital frequency synthesis module includes a phase accumulator, a waveform memory, an analog-to-digital converter, and a low-pass filter; the phase accumulator is electrically connected to the fuzzy control module and the reference frequency source, the waveform memory is electrically connected to the phase accumulator, the analog-to-digital converter is electrically connected to the waveform memory, and the low-pass filter is electrically connected to the analog-to-digital converter.

[0009] As a preferred embodiment, the phase accumulator is a 27-bit phase accumulator, the waveform memory is a 4096-point 16-bit quantized sine wave memory, the analog-to-digital converter is a high-speed DAC converter, the phase accumulator has a reference frequency of 10MHz and a frequency resolution of 0.0745Hz. The phase accumulator performs phase accumulation at the 10MHz reference frequency according to the frequency control command, queries the corresponding 16-bit quantized sine wave data through the waveform memory, converts it into an analog signal through the high-speed DAC converter, and outputs a high-precision sine wave.

[0010] As a preferred embodiment, the admittance detection unit extracts impedance phase angle and power spectrum information through FFT operation.

[0011] As a preferred embodiment, the PID adjustment unit of the fuzzy control module dynamically tunes the PID parameters based on the fuzzy control output results.

[0012] As a preferred embodiment, the welding head has an internal heat flow channel heat dissipation structure, and the top of the welding head is covered with a copper / titanium dissimilar alloy anti-wear coating.

[0013] Compared with the prior art, the present invention has obvious advantages and beneficial effects. Specifically, as can be seen from the above technical solution: This invention combines fuzzy control and DDS technology, achieving a frequency control accuracy of ±0.0745Hz, a significant improvement that far exceeds the ±20Hz level of similar domestic products and approaches or surpasses the ±1.0Hz performance of foreign products, effectively preventing resonant frequency drift. Simultaneously, the fuzzy control strategy based on admittance characteristics allows for adaptation to different load characteristics without on-site parameter adjustments, demonstrating strong load adaptability and solving the problem of traditional PID control's inability to handle both large and small loads, thus improving system stability. The invention boasts a frequency tracking speed of 20kHz / s, a fast response time, and a control cycle of only about 28μs, enabling rapid response to parameter fluctuations caused by changes in ambient temperature and workpiece material. The amplitude control accuracy reaches ±1μm, ensuring uniform heating of the welding interface, reducing burrs and welding defects, lowering scrap rates, and ensuring stable welding quality. Furthermore, the integrated design of this invention achieves integrated signal acquisition, control, and drive, coupled with optimized welding head heat dissipation and wear resistance, resulting in a compact and reliable structure that extends equipment lifespan.

[0014] To more clearly illustrate the structural features and effects of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0015] Figure 1 This is an overall structural block diagram of a preferred embodiment of the present invention; Figure 2This is a schematic diagram illustrating the working principle of the fuzzy control module in a preferred embodiment of the present invention; Figure 3 This is a schematic diagram of the digital frequency synthesis module structure in a preferred embodiment of the present invention; Figure 4 This is a schematic diagram of the electrical admittance feature detection process in a preferred embodiment of the present invention; Figure 5 This is a schematic diagram of the ultrasonic welding principle of plastics in a preferred embodiment of the present invention.

[0016] Explanation of reference numerals in the attached diagram: 10. Signal Acquisition Module; 11. Voltage Sensor; 12. Current Sensor; 13. Admittance Detection Unit; 20. Fuzzy Control Module; 21. Fuzzy Controller; 22. PID Adjustment Unit; 30. Digital Frequency Synthesis Module; 31. Phase Accumulator; 32. Waveform Memory; 33. Analog-to-Digital Converter; 34. Low-Pass Filter; 40. Power Drive Module; 41. PPC Power Factor Correction Circuit; 42. Inverter; 43. Rectifier and Filter Circuit; 50. Execution Module; 51. Transducer; 52. Amplifier; 53. Welding Head; 60. Feedback Adjustment Module; 71. Reference Frequency Source; 72. Workpiece. Detailed Implementation

[0017] Please refer to Figures 1 to 5 As shown, it illustrates the specific structure of a preferred embodiment of the present invention, including a signal acquisition module 10, a fuzzy control module 20, a digital frequency synthesis module 30, a power drive module 40, an execution module 50, and a feedback adjustment module 60, with each module being electrically connected in sequence to form a closed-loop control circuit.

[0018] The signal acquisition module 10 includes a voltage sensor 11, a current sensor 12, and an admittance detection unit 13. The voltage sensor 11, current sensor 12, and admittance detection unit 13 are used to acquire the voltage signal, current signal, and admittance characteristic parameters (including conductance value G and susceptance value B) of the transducer 51, respectively, and convert the analog signals into digital signals. In this embodiment, the admittance detection unit 13 extracts impedance phase angle and power spectrum information through FFT operation. Specifically, the admittance detection unit 13 processes the voltage and current signals through FFT operation, then extracts the conductance value G, susceptance value B, impedance phase angle, and power spectrum information, and transmits all digital signals to the fuzzy control module 20.

[0019] The fuzzy control module 20 integrates a fuzzy controller 21 and a PID control unit 22. The fuzzy controller 21 is electrically connected to the signal acquisition module 10, and the PID control unit 22 is electrically connected to the fuzzy controller 21. The fuzzy controller 21 uses the system output, output error, error change, and electrical admittance characteristic parameters as fuzzy variables, and outputs control commands after fuzzification, rule-based reasoning, and defuzzification. In this embodiment, the control cycle of the fuzzy controller 21 is one vibration cycle, distributed around 28 μs. The fuzzy variable domain includes frequency deviation, amplitude deviation, conductance value, and susceptance value. The frequency deviation is -10Hz to 10Hz, the amplitude deviation is -5μm to 5μm, the conductance value is 0 to 5S, and the susceptance value is -5S to 5S. The fuzzy subset membership function adopts a triangular distribution and is defuzzified using the area bisector method. The PID control unit 22 of the fuzzy control module 20 dynamically tunes the PID parameters based on the fuzzy control output results. Furthermore, the control rule base of the fuzzy controller 21 contains 50 core rules. For example, if the frequency deviation is "positive large" and the conductivity value is "large", then the frequency control word is "negative large"; if the amplitude deviation is "positive small" and the susceptance value is "medium", then the amplitude adjustment signal is "negative small"; if the frequency deviation is "zero" and the conductivity value is "medium", then the current PID parameters are maintained. The fuzzification process of the fuzzy control module 20 is as follows: the frequency deviation is quantized into 13 universes of discourse elements {-6,-5,...,0,...,5,6}, the amplitude deviation is quantized into 9 universes of discourse elements {-4,-3,...,0,...,3,4}, and the conductance and susceptance values ​​are quantized into 11 universes of discourse elements each {0,1,...,5} and {-5,-4,...,0,...,4,5}, respectively; based on preset control rules (such as "when the conductance value is large and the frequency deviation is positive, reduce the frequency control word"), logical reasoning is performed, and after defuzzification using the area bisector method, the frequency control command and amplitude adjustment signal are output; the PID control unit 22 dynamically tunes the proportional coefficient P, integral coefficient I, and derivative coefficient D according to the fuzzy output to optimize the control response.

[0020] The digital frequency synthesis module 30 is electrically connected to the fuzzy control module 20. The digital frequency synthesis module 30 employs DDS (Digital Frequency Synthesis) technology to generate a digital sine wave signal based on the frequency control commands from the fuzzy control module 20. Specifically, as... Figure 3As shown, the digital frequency synthesis module 30 includes a phase accumulator 31, a waveform memory 32, an analog-to-digital converter 33, and a low-pass filter 34. The phase accumulator 31 is electrically connected to the fuzzy control module 20 and the reference frequency source 71. The waveform memory 32 is electrically connected to the phase accumulator 31. The analog-to-digital converter 33 is electrically connected to the waveform memory 32. The low-pass filter 34 is electrically connected to the analog-to-digital converter 33. In this embodiment, the phase accumulator 31 is a 27-bit phase accumulator, the waveform memory 32 is a 4096-point 16-bit quantized sine wave memory, and the analog-to-digital converter 33 is a high-speed DAC converter. The phase accumulator has a reference frequency of 10MHz and a frequency resolution of 0.0745Hz. According to the frequency control command, the phase accumulator 31 performs phase accumulation at the 10MHz reference frequency, queries the corresponding 16-bit quantized sine wave data through the waveform memory 32, converts it into an analog signal via the high-speed DAC converter, and outputs a high-precision sine wave. The accuracy of the digital sine wave signal is ±0.0745Hz. Furthermore, the frequency control word of the digital frequency synthesis module 30 is dynamically updated through the command output by the fuzzy control module 20, achieving high-speed frequency tracking of 20kHz / s. When the workpiece material is switched from ABS to PA66, the system can complete the resonant frequency adjustment within 0.1s, ensuring stable welding quality.

[0021] The power drive module 40 includes a PPC power factor correction circuit 41 and an inverter 42. The PPC power factor correction circuit 41 is used to correct the power factor of the input power supply. The inverter 42 is used to amplify the sine wave signal into a high-power drive signal. The inverter 42 is electrically connected to the PPC power factor correction circuit 41, and is also electrically connected to the PID control unit 22 and the digital frequency synthesis module 30. The power drive module 40 amplifies the signal output from the digital frequency synthesis module 30 and provides stable drive power to the execution module 50. Furthermore, the PPC power factor correction circuit 41 is also connected to a rectifier and filter circuit 43, which is used to rectify and filter the input power supply, which is 220V and has a frequency of 50Hz.

[0022] The execution module 50 consists of a transducer 51, an amplitude transformer 52, and a welding head 53. The transducer 51 is electrically connected to the voltage sensor 11, the current sensor 12, and the admittance detection unit 13. The transducer 51 converts electrical signals into mechanical vibrations, which are amplified by the amplitude transformer 52 and then transmitted to the workpiece 72 through the welding head 53. In this embodiment, the welding head 53 has a built-in internal heat dissipation structure (not shown in the figure), and the top of the welding head 53 is covered with a copper / titanium dissimilar alloy anti-wear coating (not shown in the figure). This copper / titanium dissimilar alloy anti-wear coating can reduce frictional loss with the workpiece 72, thereby achieving precise welding of the plastic workpiece 72.

[0023] The feedback adjustment module 60 is electrically connected to the execution module 50, the signal acquisition module 10, and the fuzzy control module 20. The feedback adjustment module 60 collects the vibration frequency, amplitude, and welding head 53 temperature signals of the execution module 50 in real time and feeds them back to the signal acquisition module 10 and the fuzzy control module 20 to dynamically adjust the control parameters and ensure the stability of the welding process.

[0024] The key design features of this invention are as follows: Combining fuzzy control and DDS technology, the frequency control accuracy reaches ±0.0745Hz, a significant improvement that far exceeds the ±20Hz level of similar domestic products and approaches or surpasses the ±1.0Hz performance of foreign products, effectively preventing resonant frequency drift. Simultaneously, the fuzzy control strategy based on admittance characteristics allows for adaptation to different load characteristics without on-site parameter adjustments, demonstrating strong load adaptability and solving the problem of traditional PID control's difficulty in handling both large and small loads, thus improving system stability. The frequency tracking speed reaches 20kHz / s, with a fast response speed and a control cycle of only about 28μs, enabling rapid response to parameter fluctuations caused by changes in ambient temperature and workpiece material. The amplitude control accuracy reaches ±1μm, ensuring uniform heating of the welding interface, reducing burrs and welding defects, lowering the scrap rate, and ensuring stable welding quality. Furthermore, the integrated design of this invention achieves integrated signal acquisition, control, and drive, combined with optimized welding head heat dissipation and wear resistance, resulting in a compact and reliable structure that extends equipment lifespan.

[0025] 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. An ultrasonic fuzzy control device based on fuzzy control and electrical admittance feature tracking, characterized in that: It includes a signal acquisition module, a fuzzy control module, a digital frequency synthesis module, a power drive module, an execution module, and a feedback adjustment module. Each module is electrically connected in sequence to form a closed-loop control circuit. The signal acquisition module includes a voltage sensor, a current sensor, and an admittance detection unit. The voltage sensor, current sensor, and admittance detection unit are used to acquire the voltage signal, current signal, and admittance characteristic parameters of the transducer, respectively, and convert the analog signal into a digital signal. The admittance detection unit extracts impedance phase angle and power spectrum information through FFT operation. The fuzzy control module has a built-in fuzzy controller and a PID control unit. The fuzzy controller is electrically connected to the signal acquisition module, and the PID control unit is electrically connected to the fuzzy controller. The fuzzy controller uses the system output, output error, error change, and electrical admittance characteristic parameters as fuzzy variables, and outputs control commands after fuzzification, rule reasoning, and defuzzification. The PID control unit of the fuzzy control module dynamically tunes the PID parameters based on the fuzzy control output results. The digital frequency synthesis module is electrically connected to the fuzzy control module. The digital frequency synthesis module uses DDS technology to generate a digital sine wave signal according to the frequency control command of the fuzzy control module. The power drive module includes a PPC power factor correction circuit and an inverter; the inverter is electrically connected to the PPC power factor correction circuit, and the inverter is also electrically connected to the PID control unit and the digital frequency synthesis module. The power drive module amplifies the signal output by the digital frequency synthesis module and provides stable drive power to the execution module. The execution module consists of a transducer, an amplitude transformer, and a welding head. The transducer is electrically connected to a voltage sensor, a current sensor, and an admittance detection unit. The transducer converts electrical signals into mechanical vibrations, which are amplified by the amplitude transformer and then transmitted to the workpiece through the welding head. The feedback adjustment module is electrically connected to the execution module, the signal acquisition module, and the fuzzy control module. The feedback adjustment module collects the vibration frequency, amplitude, and welding head temperature signals of the execution module in real time and feeds them back to the signal acquisition module and the fuzzy control module.

2. The ultrasonic fuzzy control device based on fuzzy control and electrical admittance feature tracking according to claim 1, characterized in that: The control cycle of the fuzzy controller is one vibration cycle, distributed over 28 μs. The fuzzy variable domain includes frequency deviation, amplitude deviation, conductivity, and susceptance. The frequency deviation is -10 Hz to 10 Hz, the amplitude deviation is -5 μm to 5 μm, the conductivity is 0 to 5 S, and the susceptance is -5 S to 5 S.

3. The ultrasonic fuzzy control device based on fuzzy control and electrical admittance feature tracking according to claim 1, characterized in that: The digital frequency synthesis module includes a phase accumulator, a waveform memory, an analog-to-digital converter, and a low-pass filter; the phase accumulator is electrically connected to the fuzzy control module and the reference frequency source, the waveform memory is electrically connected to the phase accumulator, the analog-to-digital converter is electrically connected to the waveform memory, and the low-pass filter is electrically connected to the analog-to-digital converter.

4. The ultrasonic fuzzy control device based on fuzzy control and electrical admittance feature tracking according to claim 3, characterized in that: The phase accumulator is a 27-bit phase accumulator, the waveform memory is a 4096-point 16-bit quantized sine wave memory, the analog-to-digital converter is a high-speed DAC converter, the phase accumulator has a reference frequency of 10MHz and a frequency resolution of 0.0745Hz. The phase accumulator performs phase accumulation at the 10MHz reference frequency according to the frequency control command, queries the corresponding 16-bit quantized sine wave data through the waveform memory, converts it into an analog signal through the high-speed DAC converter, and outputs a high-precision sine wave.

5. The ultrasonic fuzzy control device based on fuzzy control and electrical admittance feature tracking according to claim 1, characterized in that: The welding head has an internal heat flow channel heat dissipation structure, and the top of the welding head is covered with a copper / titanium dissimilar alloy anti-wear coating.

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