Automatic frequency tracking and adjusting circuit suitable for ultrasonic grinding machine

Abstract

The invention relates to the technical field of adjusting circuits, in particular to an automatic frequency tracking adjusting circuit suitable for an ultrasonic grinding machine, which comprises a current detection module used for detecting a current signal of a transducer; the voltage detection module is used for detecting a voltage signal of the transducer; the comparison circuit is respectively connected with the output end of the current detection module and the output end of the voltage detection module; the logic processing circuit is connected with the output end of the comparison circuit and used for carrying out logic processing on signals output by the comparison circuit; and the singlechip is connected with the logic processing circuit and is used for receiving the signal output by the logic processing circuit and outputting a control signal to the frequency generator. According to the automatic frequency tracking and adjusting circuit suitable for the ultrasonic grinding machine, current signals and voltage signals of the transducer are detected through the current detection module and the voltage detection module, the current signals and the voltage signals are sent to the single chip microcomputer after being processed, and the single chip microcomputer can output control signals to the frequency generator according to the received signals; and adjusting the output frequency of the frequency generator.

Description

Technical Field

[0001] This invention relates to the field of adjustment circuit technology, specifically to an automatic frequency tracking adjustment circuit suitable for ultrasonic grinding machines. Background Technology

[0002] The main function of the generator (power supply) of an ultrasonic polishing machine is to drive a piezoelectric ceramic transducer, exciting it to operate at its mechanical resonant frequency, thereby converting electrical energy into mechanical energy for mechanical polishing. The transducer can only achieve its highest energy conversion efficiency when operating at its optimal resonant frequency.

[0003] However, the optimal resonant frequency of a transducer is not constant and can change due to several factors, such as changes in material properties caused by temperature variations, changes in pressure during grinding, changes in the tightness of the connection of the ultrasonic amplitude transformer, changes in the load caused by different methods of fixing the processing needle, and changes in performance caused by aging after long-term use of the transducer.

[0004] If the generator always outputs a fixed frequency, once it deviates from the actual resonant point of the transducer, it will lead to a decrease in output power, low efficiency, severe heat generation, and may damage the transducer or power transistor, resulting in unstable working performance and other problems.

[0005] In view of this, we propose an automatic frequency tracking and adjustment circuit suitable for ultrasonic grinders. Summary of the Invention

[0006] The purpose of this invention is to provide an automatic frequency tracking adjustment circuit suitable for ultrasonic polishing machines, which solves the problems in the prior art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: An automatic frequency tracking and adjustment circuit suitable for an ultrasonic polishing machine includes: The current detection module is used to detect the current signal of the transducer; The voltage detection module is used to detect the voltage signal of the transducer; The comparison circuit is connected to the output terminals of the current detection module and the voltage detection module, respectively. The logic processing circuit is connected to the output of the comparator circuit and is used to perform logic processing on the signal output by the comparator circuit. A microcontroller is connected to a logic processing circuit to receive signals output by the logic processing circuit and output control signals to a frequency generator.

[0008] As a preferred technical solution, the comparison circuit includes a first comparator and a second comparator. The first comparator is used to compare the output signal of the current detection module with a reference voltage, and the second comparator is used to compare the output signal of the voltage detection module with a reference voltage.

[0009] As a preferred technical solution, the inverting input terminal of the first comparator is connected to the signal output terminal of the current detection module through a first resistor, and the non-inverting input terminal of the first comparator is connected to a first variable resistor and a first capacitor in sequence, and then connected to the signal output terminal of the current detection module through the first resistor.

[0010] As a preferred technical solution, a third resistor is connected to the non-inverting input terminal of the first comparator, and the other end of the third resistor is connected to the output terminal of the first comparator.

[0011] As a preferred technical solution, the inverting input terminal of the second comparator is connected to the signal output terminal of the voltage detection module through the second resistor, and the non-inverting input terminal of the second comparator is connected to the second variable resistor and the second capacitor in sequence, and then connected to the signal output terminal of the current detection module through the second resistor.

[0012] As a preferred technical solution, the non-inverting input terminal of the second comparator is connected to a fourth resistor, and the other end of the third resistor is connected to the output terminal of the second comparator.

[0013] As a preferred technical solution, the logic processing circuit includes a hex inverter. The first signal input terminal of the hex inverter is connected to the output terminal of the first comparator. After receiving the signal output by the first comparator, the hex inverter performs inversion processing and outputs a first inverted signal through the first inverted signal output terminal. The second signal input terminal of the hex inverter is connected to the output terminal of the second comparator. After receiving the signal output by the second comparator, the hex inverter performs inversion processing and outputs the second inverted signal through the second inverted signal output terminal.

[0014] As a preferred technical solution, the logic processing circuit further includes an AND gate chip, wherein the first inverting signal input terminal of the AND gate chip is connected to the first inverting signal output terminal of the hex inverter, the second inverting signal input terminal of the AND gate chip is connected to the second inverting signal output terminal of the hex inverter, and the output terminal of the AND gate chip is connected to one of the input terminals of the microcontroller.

[0015] As a preferred technical solution, the logic processing circuit further includes a D flip-flop, the clock input terminal of which is connected to the first inverted signal output terminal of the hex inverter, the data input terminal of which is connected to the second inverted signal output terminal of the hex inverter, and the output terminal of which is connected to one of the input terminals of the microcontroller.

[0016] As a preferred technical solution, a frequency generator is also included. The serial port receiving end of the frequency generator is connected to the serial port transmitting end of the microcontroller, and the serial port transmitting end of the frequency generator is connected to the serial port receiving end of the microcontroller to form a serial communication line.

[0017] By employing the above technical solution, the present invention provides an automatic frequency tracking and adjustment circuit suitable for ultrasonic polishing machines. It possesses at least the following beneficial effects: This automatic frequency tracking and adjustment circuit, applicable to ultrasonic grinding machines, detects the current and voltage signals of the transducer through a current detection module and a voltage detection module. After processing, the signals are sent to a microcontroller. The microcontroller can output a control signal to the frequency generator based on the received signals, adjusting the output frequency of the frequency generator so that the output frequency of the frequency generator can be kept consistent with the optimal resonant frequency of the transducer, thereby improving the working stability of the transducer. Attached Figure Description

[0018] The accompanying drawings, which are provided to further illustrate the invention, constitute a part of this application: Fig. 1 This is a schematic diagram of the detection circuit in an embodiment of the present invention; Fig. 2 This is a schematic diagram of the control circuit in an embodiment of the present invention. Detailed Implementation

[0019] 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.

[0020] The main function of the generator (power supply) of an ultrasonic polishing machine is to drive a piezoelectric ceramic transducer, exciting it to operate at its mechanical resonant frequency, thereby converting electrical energy into mechanical energy for mechanical polishing. The transducer can only achieve its highest energy conversion efficiency when operating at its optimal resonant frequency.

[0021] However, in actual operation, the optimal resonant frequency of the transducer can be altered by various factors. If the generator consistently outputs a fixed frequency, deviations from the transducer's actual resonant point can lead to reduced output power, excessive heat generation, and unstable performance.

[0022] In summary, there must be a circuit that can track the transducer’s current optimal resonant frequency in real time and adjust the generator’s output frequency to synchronize with it.

[0023] Please see Figs. 1-2 The present invention provides a technical solution: An automatic frequency tracking and adjustment circuit suitable for ultrasonic grinding machines includes a detection circuit and a control circuit. The detection circuit detects the current and voltage signals of the transducer, processes them, and sends them to the control circuit. The control circuit can output a control signal to the frequency generator based on the received signals to adjust the output frequency of the generator.

[0024] Combination Fig. 1 As shown, the detection circuit includes: The current detection module U4 is used to detect the current signal of the transducer and convert it into a voltage signal, which is then output from the signal output terminal. The voltage detection module U5 is used to detect the voltage signal of the transducer and directly output the corresponding voltage signal from the signal output terminal. The comparison circuit is connected to the output terminals of the current detection module U4 and the voltage detection module U5, respectively, to compare the magnitude of the detection signal with the reference voltage and output the corresponding signal. The logic processing circuit is connected to the output of the comparator circuit and is used to perform logic processing on the signal output by the comparator circuit.

[0025] The power input terminal of the current detection module U4 is connected to the positive terminal of the power supply to obtain the operating voltage, ensuring the normal operation of the module and realizing the current detection function. The two ground terminals of the current detection module U4 are grounded, providing a return path for the internal current and ensuring that the module's operating potential remains consistent with the entire circuit system, thus ensuring the stability of the current detection. The signal output terminal of the current detection module U4 is connected to the comparator circuit to output a voltage signal corresponding to the detected current. This voltage signal enters the comparator circuit.

[0026] Similar to the current detection module U4, the voltage detection module U5 connects its power input terminal to the positive terminal of the power supply to obtain the operating voltage, ensuring normal operation and enabling the voltage detection function. The two grounding terminals of the voltage detection module U5 are grounded, providing a return path for the internal current and ensuring that the module's operating potential remains consistent with the entire circuit system, thus guaranteeing the stability of the voltage detection. The signal output terminal of the voltage detection module U5 is connected to the comparator circuit to output a voltage signal corresponding to the detected current; this voltage signal then enters the comparator circuit.

[0027] The comparison circuit includes a first comparator U8.1 and a second comparator U8.2. These two comparator units are part of the dual voltage comparator chip LM393AN, used to shape the voltage and current signals of the same frequency acquired from the transducer into square wave signals. Specifically, the first comparator U8.1 compares the output signal of the current detection module U4 with a set reference voltage, and the second comparator U8.2 compares the output signal of the voltage detection module U5 with a set reference voltage.

[0028] Specifically, the first comparator U8.1 is connected to the current detection module U4 to receive the signal output by the current detection module U4, compare it with a reference voltage, and finally output a first signal. The second comparator U8.2 is connected to the voltage detection module U5 to receive the signal output by the voltage detection module U5, compare it with a reference voltage, and finally output a second signal.

[0029] The comparator circuit also includes a first resistor R8 and a second resistor R13. One end of the first resistor R8 is connected to the signal output terminal of the current detection module U4, and the other end is split into two paths. One path is directly connected to the inverting input terminal of the first comparator U8.1, and the other path is connected to the first capacitor C9 and the first variable resistor RD1 in sequence, and then connected to the power supply to power the first comparator U8.1. The non-inverting input terminal of the first comparator U8.1 is split into two paths. One path is connected to the first variable resistor RD1 to provide a reference voltage, and the other path is connected to the third resistor R9. The other end of the third resistor R9 is connected to the output terminal of the first comparator U8.1. By changing the resistance value of the first variable resistor RD1, the reference voltage value of the non-inverting input terminal of the first comparator U8.1 can be adjusted.

[0030] Similarly, one end of the second resistor R13 is connected to the signal output terminal of the voltage detection module U5, and the other end is split into two paths. One path is directly connected to the inverting input terminal of the second comparator U8.2, and the other path is connected to the second capacitor C10 and the second variable resistor RD2 in sequence before being connected to the power supply to power the second comparator U8.2. The non-inverting input terminal of the second comparator U8.2 is split into two paths. One path is connected to the second variable resistor RD2 to provide a reference voltage. The other path is connected to the fourth resistor R10, and the other end of the fourth resistor R10 is connected to the output terminal of the second comparator U8.2. By changing the resistance value of the second variable resistor RD2, the reference voltage value of the non-inverting input terminal of the second comparator U8.2 can be adjusted.

[0031] In one embodiment, the first resistor R8 and the second resistor R13 are both 10kΩ current-limiting resistors, which limit the amount of current flowing from the output of the detection module into the input of the subsequent comparator, preventing the comparator from being damaged by excessive current, and also playing a certain role in signal voltage division.

[0032] In one embodiment, the first capacitor C9 and the second capacitor C10 are both 47pF capacitors, which serve as filters to remove high-frequency noise in the output signal of the detection module, making the signal input to the comparator more stable and improving the accuracy of detection.

[0033] In one embodiment, the first variable resistor RD1 and the second variable resistor RD2 are both 10kΩ sliding rheostats. By adjusting their resistance values, the reference voltage value at the non-inverting input of the comparator can be changed, thereby achieving flexible adjustment of the current and voltage detection thresholds.

[0034] In one embodiment, the third resistor R9 and the fourth resistor R10 are both 51kΩ resistors, which, together with the first variable resistor RD1 and the second variable resistor RD2, are used to set the reference voltage of the comparator. By changing the resistance values ​​of the variable resistors, the magnitude of the reference voltage can be adjusted, thereby adjusting the trigger threshold of the comparator.

[0035] The logic processing circuit includes a hex inverter U3, also known as a NOT gate chip, model CD4049UBE. The first signal input terminal of the hex inverter U3 is connected to the output terminal of the first comparator U8.1, and the second signal input terminal of the hex inverter U3 is connected to the output terminal of the second comparator U8.2. This circuit inverts the high and low level signals input to the two comparators and outputs a first inverted signal and a second inverted signal.

[0036] The logic processing circuit also includes an AND gate chip U6 and a D flip-flop U7. The first inverted signal output terminal of the hex inverter U3 is connected to the first inverted signal input terminal of the AND gate chip U6 and a clock input terminal of the D flip-flop U7, respectively. The second inverted signal output terminal of the hex inverter U3 is connected to the second inverted signal input terminal of the AND gate chip U6 and a data input terminal of the D flip-flop U7, respectively.

[0037] The AND gate chip U6, model number CD4081BE, is a quad 2-input AND gate chip used to perform logical AND operations on multiple signals and output enable or trigger signals. When both the first and second inverting inputs of the AND gate chip U6 are high, its output is high; when one or both of the first and second inverting inputs are low, its output is low. One end of the AND gate chip U6 is grounded, and the other end is connected to a power supply to ensure stable operation.

[0038] The D flip-flop U7, model number CD4013BD, is a dual D flip-flop chip used for latching states, providing data storage and timing control functions. The D flip-flop U7 receives the first inverted signal from the AND gate chip U6 via its clock input, controlling the flip-flop state update. When the rising edge of the clock signal arrives, the level on the data input pin is transferred to the positive data output pin and maintained in that state until the next rising edge of the clock. One end of the D flip-flop U7 is grounded, and the other end is connected to the power supply to ensure stable operation.

[0039] In addition, it includes a fifth resistor R11 and a sixth resistor R12. One end of the fifth resistor R11 is connected to the power supply, and the other end is connected between the hex inverter U3 and the first comparator U8.1. One end of the sixth resistor R12 is connected to the power supply, and the other end is connected between the hex inverter U3 and the second comparator U8.2. Both the fifth resistor R11 and the sixth resistor R12 are 10kΩ pull-up resistors, used to pull the voltage at the comparator output to the power supply level, ensuring that the output voltage is stable at VCC when the comparator output is high, and also enhancing the driving capability of the output signal.

[0040] Please see Fig. 2 The control circuit includes a microcontroller U1.

[0041] The microcontroller U1, model STC15W408AS-35I-DIP16, is used to receive detection signals, process logic, and output control signals.

[0042] The external interrupt 1 input of microcontroller U1 is used to receive the signal output by AND gate chip U6, and the external interrupt 0 input of microcontroller U1 is used to receive the signal output by D flip-flop U7, so that the detection signal is transmitted to microcontroller U1 for subsequent processing. The reset output of microcontroller U1 is used to output PWM signal.

[0043] The control circuit also includes a frequency generator U11. The serial port receiver of the frequency generator U11 is connected to the serial port transmitter of the microcontroller U1, and the serial port transmitter of the frequency generator U11 is connected to the serial port receiver of the microcontroller U1, forming a serial communication line. The microcontroller U1 can send control commands to the frequency generator U11 through the serial port, and the frequency generator U11 can also send back operating status information to the microcontroller U1 through the serial port. The PWM signal output terminal of the frequency generator U11 is used to output a clock signal.

[0044] The control circuit also includes resistors R26 and R27. Resistor R26 is connected in series between AND gate chip U6 and microcontroller U1, and resistor R27 is connected in series between D flip-flop U7 and microcontroller U1. Both resistors R26 and R27 are 10KΩ pull-down resistors.

[0045] The automatic frequency tracking and adjustment circuit of this invention, applicable to ultrasonic grinding machines, collects current and voltage signals from the transducer via current detection module U4 and voltage detection module U5, respectively. Two zero-crossing comparators from an LM393AN calibrate the voltage and current signals of the same frequency collected from the transducer into square wave signals. These signals are then isolated and simultaneously output to AND gate chip U6 and D flip-flop U7 via CD4049UBE hex inverter U3. D flip-flop U7 outputs a pulse width signal C, and AND gate chip U6 also outputs a pulse width signal C. The microcontroller U1 continuously scans the pulse width signals C and C, using a fuzzy logic algorithm to control the frequency generator U11 to output a suitable frequency value, ensuring the transducer always operates in a resonant state, thus achieving frequency tracking and adjustment.

[0046] Specifically, in operation, this circuit works as follows: First, the current detection module U4 detects the operating current of the piezoelectric ceramic transducer in the ultrasonic grinder and converts it into a voltage signal, which is output from the signal output terminal. This voltage signal passes through the first resistor R8 and is then input to the inverting input terminal of the first comparator U8.1. Simultaneously, a voltage divider circuit composed of the first variable resistor RD1 and the third resistor R9 provides a reference voltage to the non-inverting input terminal of the first comparator U8.1. The first comparator U8.1 compares the signals received at its inverting and non-inverting input terminals and outputs a first signal. When the voltage signal detected at the inverting input terminal of the first comparator U8.1 is greater than the reference voltage at the non-inverting input terminal, the first signal output by the first comparator U8.1 is low; otherwise, it is high.

[0047] On the other hand, the voltage detection module U5 detects the operating voltage of the piezoelectric ceramic transducer in the ultrasonic grinder and outputs the corresponding voltage signal. This voltage signal is input to the inverting input of the second comparator U8.2 after passing through the second resistor R13 and is compared with the reference voltage. When the voltage signal corresponding to the detected voltage is greater than the reference voltage, the second signal output by the second comparator U8.2 is low level, and vice versa.

[0048] The first signal output by the first comparator U8.1 and the second signal output by the second comparator U8.2 are respectively input to the first signal input terminal and the second signal input terminal of the hex inverter U3. The hex inverter U3 inverts the two signals and outputs the first inverted signal and the second inverted signal.

[0049] The AND gate chip U6 simultaneously receives the first and second inverted signals, performs a logical AND operation on the input signals, and finally outputs the pulse width signal C to the microcontroller U1. When the first and second inverted signal input terminals of the AND gate chip U6 are in phase, the duty cycle of the pulse width signal C is 50%. If there is a phase difference, the duty cycle of the pulse width signal C will be less than 50%.

[0050] D flip-flop U7 also receives both the first and second inverted signals. Triggered by the clock signal, D flip-flop U7 transmits data to the output terminal according to the input signal state, realizing signal storage and shifting functions. Finally, it outputs a level signal D to the microcontroller U1 to control subsequent circuit operations. If the voltage leads the current, the level signal D is low; otherwise, it is high. The level signal D is sent to the microcontroller U1 as the basis for increasing or decreasing the output frequency.

[0051] The microcontroller U1 receives the pulse width signal C output by the AND gate chip U6 and the level signal D output by the D flip-flop U7, and controls the frequency generator U11 to output a suitable frequency value so that the transducer always works in the resonant state and achieves frequency tracking.

[0052] When the resonant frequency of the transducer matches the output frequency of the frequency generator U11, its output characteristic is equivalent to that of a pure resistor. At this time, the voltage across the transducer is in phase with the current flowing through it. Once the transducer's frequency drifts, a phase difference will occur between the voltage and current signals. The microcontroller U1 continuously detects the magnitude and direction of this phase difference to control the output of the frequency generator U11, thereby achieving frequency tracking and adjustment. In this circuit, the current detection module U4 and the voltage detection module U5 can monitor the circuit's operating status parameters in real time. These parameters can reflect the impact of frequency changes on the circuit's operation. For example, frequency changes may cause fluctuations in current and voltage.

[0053] In addition, the entire circuit monitors and controls the circuit's operating status by detecting and comparing current and voltage, performing logical operations, and triggering signals. When overcurrent or overvoltage occurs, it can output corresponding control signals in a timely manner to protect the safe operation of the circuit equipment.

[0054] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0055] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An automatic frequency tracking and adjustment circuit suitable for ultrasonic grinding machines, characterized in that, include: The current detection module is used to detect the current signal of the transducer; The voltage detection module is used to detect the voltage signal of the transducer; The comparison circuit is connected to the output terminals of the current detection module and the voltage detection module, respectively. The logic processing circuit is connected to the output of the comparator circuit and is used to perform logic processing on the signal output by the comparator circuit. A microcontroller is connected to a logic processing circuit to receive signals output by the logic processing circuit and output control signals to a frequency generator.

2. The automatic frequency tracking and adjustment circuit for an ultrasonic polishing machine according to claim 1, characterized in that, The comparison circuit includes a first comparator and a second comparator. The first comparator is used to compare the output signal of the current detection module with a reference voltage, and the second comparator is used to compare the output signal of the voltage detection module with a reference voltage.

3. The automatic frequency tracking and adjustment circuit for an ultrasonic polishing machine according to claim 2, characterized in that, The inverting input of the first comparator is connected to the signal output of the current detection module through a first resistor, and the non-inverting input of the first comparator is connected to a first variable resistor and a first capacitor in sequence, and then connected to the signal output of the current detection module through the first resistor.

4. The automatic frequency tracking and adjustment circuit for an ultrasonic polishing machine according to claim 3, characterized in that, The non-inverting input of the first comparator is connected to a third resistor, and the other end of the third resistor is connected to the output of the first comparator.

5. The automatic frequency tracking and adjustment circuit for an ultrasonic polishing machine according to claim 2, characterized in that, The inverting input of the second comparator is connected to the signal output of the voltage detection module through the second resistor, and the non-inverting input of the second comparator is connected to the second variable resistor and the second capacitor in sequence, and then connected to the signal output of the current detection module through the second resistor.

6. The automatic frequency tracking and adjustment circuit for an ultrasonic polishing machine according to claim 5, characterized in that, The non-inverting input of the second comparator is connected to a fourth resistor, and the other end of the third resistor is connected to the output of the second comparator.

7. The automatic frequency tracking and adjustment circuit for an ultrasonic polishing machine according to claim 2, characterized in that, The logic processing circuit includes a hex inverter. The first signal input terminal of the hex inverter is connected to the output terminal of the first comparator. After receiving the signal output by the first comparator, the hex inverter performs inversion processing and outputs a first inverted signal through the first inverted signal output terminal. The second signal input terminal of the hex inverter is connected to the output terminal of the second comparator. After receiving the signal output by the second comparator, the hex inverter performs inversion processing and outputs the second inverted signal through the second inverted signal output terminal.

8. The automatic frequency tracking and adjustment circuit for an ultrasonic polishing machine according to claim 7, characterized in that, The logic processing circuit also includes an AND gate chip. The first inverting signal input terminal of the AND gate chip is connected to the first inverting signal output terminal of the hex inverter. The second inverting signal input terminal of the AND gate chip is connected to the second inverting signal output terminal of the hex inverter. The output terminal of the AND gate chip is connected to one of the input terminals of the microcontroller.

9. The automatic frequency tracking and adjustment circuit for an ultrasonic polishing machine according to claim 7, characterized in that, The logic processing circuit also includes a D flip-flop, the clock input of which is connected to the first inverted signal output of a hex inverter, the data input of which is connected to the second inverted signal output of the hex inverter, and the output of which is connected to one of the inputs of the microcontroller.

10. The automatic frequency tracking and adjustment circuit for an ultrasonic polishing machine according to claim 1, characterized in that, It also includes a frequency generator, the serial port receiving end of which is connected to the serial port transmitting end of the microcontroller, and the serial port transmitting end of the frequency generator is connected to the serial port receiving end of the microcontroller to form a serial communication line.

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