Rapid frequency tracking method for ultrasonic scalpel

Abstract

The invention discloses a rapid frequency tracking method for an ultrasonic scalpel, which comprises the following steps of: outputting two alternating excitation signals with different frequencies through an ultrasonic generator, collecting voltage, current and phase difference of a transducer under the excitation of two different frequencies, calculating a tangent value of a load impedance angle under the excitation of two different frequencies, and calculating the frequency of the ultrasonic scalpel according to the tangent value. The dynamic resistance, the dynamic capacitance and the dynamic inductance of the transducer are calculated through the tangent values of the two different impedance angles; obtaining the current resonant frequency of the transducer through the obtained dynamic resistance, dynamic capacitance and dynamic inductance of the transducer; determining a load impedance angle threshold value of the transducer through impedance curve characteristics of the transducer, and determining a frequency step length required to be adjusted for frequency tracking according to the determined load impedance angle threshold value of the transducer; according to the ultrasonic scalpel system, the time of the detuning state of the transducer is shortened, the dynamic response performance of the ultrasonic scalpel system is improved, and the ultrasonic scalpel is higher in cutting speed and lower in heat damage in the working process.

Description

Technical Field

[0001] The invention relates to the technical field of ultrasonic surgical knives, and in particular to a fast frequency tracking method for ultrasonic surgical knives. Background Art

[0002] The ultrasonic scalpel system is a surgical device that uses ultrasonic energy to cut and stop bleeding on soft tissue. The ultrasonic generator generates an alternating electrical signal of a certain frequency to excite the ultrasonic transducer. The transducer converts the electrical signal into an ultrasonic signal of the same frequency. The ultrasonic signal is transmitted to the tip of the scalpel through the ultrasonic scalpel rod, causing the tip of the scalpel to generate high-frequency vibration (for example, 55.5KHz). The tip of the scalpel acts on the soft tissue to denature the protein in the tissue to form a viscoelastic coagulant. When the soft tissue here is incised, the formed viscoelastic coagulant forms a hemostatic seal on the tissue.

[0003] Because the energy of ultrasound is concentrated at the tip of the blade, it causes minimal thermal damage to surrounding tissues, and can accurately cut soft tissues and reduce damage to surrounding healthy tissues. The ultrasonic scalpel can form a coagulant while cutting, effectively stop bleeding, and reduce bleeding during surgery. The ultrasonic scalpel does not generate electric current to pass through the patient's body, so it is safe for patients with pacemakers or other electronic medical devices. Compared with electric scalpels, ultrasonic scalpels do not produce smoke, keep the surgical field clear, and facilitate doctors to perform precise operations.

[0004] In the prior art, traditional ultrasonic generator automatic frequency tracking methods include maximum current search resonant frequency method, phase-locked loop frequency tracking method, and matching inductance adjustment method. In these methods, when the resonant frequency of the transducer changes, the generator adjusts the frequency to the current resonant frequency of the transducer for a long time, causing the transducer to be in a detuned state for a long time, thereby reducing the cutting efficiency. At the same time, during the operation of the ultrasonic scalpel system, the ultrasonic transducer load changes in real time with the changes in the cutting tissue. If the ultrasonic generator always maintains the same output excitation signal frequency, the ultrasonic transducer will operate in a detuned state, which will cause the active power to decrease, the reactive power to increase, the cutting ability to decrease, and the heat to be serious.

[0005] Therefore, the ultrasonic surgical knife system needs to have the function of automatically adjusting the resonant frequency during operation. Summary of the invention

[0006] The invention overcomes the shortcomings of the prior art and provides a fast frequency tracking method for an ultrasonic surgical knife.

[0007] To achieve the above object, the technical solution adopted by the present invention is: a fast frequency tracking method for an ultrasonic surgical knife, the method is applied to an ultrasonic knife system, the ultrasonic knife system comprises: an ultrasonic knife head, an ultrasonic transducer connected to the ultrasonic knife head, and an ultrasonic generator connected to the ultrasonic transducer via a cable; characterized in that the fast frequency tracking method comprises the following steps:

[0008] S1, the ultrasonic generator starts and outputs a preset reference frequency f std =55.0KHz;

[0009] S2. At the reference frequency, use the ultrasonic generator to collect the output frequency f std The voltage and current signals of the ultrasonic transducer are used to calculate the phase difference between the two signals and obtain the first phase difference value.

[0010] S3, the ultrasonic generator changes the output frequency to a preset reference frequency f ref ;

[0011] S4. Under the reference frequency, use the ultrasonic generator to collect the output frequency f ref The voltage and current signals when passing through the ultrasonic transducer are calculated, and the phase difference between the two signals is obtained to obtain the second phase difference value.

[0012] S5. Calculate the sampling to get the phase difference and Quickly calculate the resonant frequency f of the ultrasonic knife system s ;

[0013] S6, the ultrasonic generator adjusts the output frequency to the resonant frequency f calculated in S5 s , driving the ultrasonic transducer to work at this frequency;

[0014] S7: The voltage and current of the ultrasonic transducer are sampled in real time through the ultrasonic knife system, and the phase difference of the voltage and current signals is calculated.

[0015] S8, according to the phase difference sampled in real time in S7 The ultrasonic generator adjusts the output excitation frequency in a variable step-size manner to keep the ultrasonic transducer operating in a resonant state.

[0016] In a preferred embodiment of the present invention, the reference frequency f in step S3 is ref =56.0KHz.

[0017] In a preferred embodiment of the present invention, the resonant frequency f is calculated in step S5 s When the ultrasonic transducer equivalent circuit includes a dynamic resistance R1 , dynamic inductance L 1 And the dynamic capacitance C 1 ; R 1 , L 1 , C 1 Form a series branch, and the static capacitance C 0 connected in parallel in the equivalent circuit.

[0018] In a preferred embodiment of the present invention, when the excitation frequency of the ultrasonic generator satisfies At this time, the ultrasonic transducer works in the series resonance state, and the phase difference between the voltage and current is 0, which is equivalent to a pure resistance impedance R 1 The impedance is minimal and the output efficiency is highest.

[0019] In a preferred embodiment of the present invention, when the ultrasonic knife system operates in a non-resonant state, the phase difference between the voltage and the current is the same as the load impedance angle of the ultrasonic knife head.

[0020] In a preferred embodiment of the present invention, the ultrasonic transducer includes: a housing, a pre-tightening bolt disposed in the housing, a sandwich piezoelectric ceramic sheet installed in cooperation with the pre-tightening bolt, and a horn installed at one end away from the pre-tightening bolt.

[0021] In a preferred embodiment of the present invention, the ultrasonic blade head includes: a sleeve, a blade rod and a jaw arranged at one end of the sleeve, and a steering knob installed in cooperation with the other end of the sleeve; the ultrasonic blade head also includes a handle, the handle is installed in cooperation with the steering knob, and a closing switch is provided on the handle, and a MAX switch and a MIN switch are provided on the closing switch.

[0022] In a preferred embodiment of the present invention, the knife rod is connected to the ultrasonic transducer inside the sleeve, and the ultrasonic transducer is connected to the ultrasonic generator via a cable.

[0023] In a preferred embodiment of the present invention, the adjustment step length of adjusting the excitation frequency of the ultrasonic generator in step S8 is determined by judging the voltage and current phase difference sampled in real time. Is it greater than the set phase difference threshold? This judgment is based on the maximum step length step max Adjust the frequency, or with the minimum step size step min Adjust the frequency.

[0024] In a preferred embodiment of the present invention, the direction of adjusting the excitation frequency of the ultrasonic generator in step S8 is determined by judging the voltage and current phase difference sampled in real time. Whether it is greater than 0 is used to determine whether to increase or decrease the frequency.

[0025] The present invention solves the defects existing in the background technology and has the following beneficial effects:

[0026] (1) The present invention proposes a fast frequency tracking method for an ultrasonic surgical knife, which outputs two alternating excitation signals of different frequencies through an ultrasonic generator, and collects the voltage, current and phase difference of the ultrasonic transducer and the tangent value of the load impedance angle under the two different frequency excitations, and then calculates the dynamic resistance, dynamic capacitance and dynamic inductance of the ultrasonic transducer through the tangent values ​​of the two different impedance angles, and then calculates the current resonant frequency of the ultrasonic transducer through the obtained numerical values, that is, only two calculation cycles are required to determine the current resonant frequency of the transducer, which shortens the time of the transducer detuning state, improves the startup speed of the ultrasonic generator, shortens the frequency tracking transition time, improves the dynamic response performance of the system, and makes the ultrasonic surgical knife cut faster and cause less thermal damage during operation.

[0027] (2) The present invention determines the load impedance angle threshold of the ultrasonic transducer through the impedance curve characteristics of the ultrasonic transducer, and determines the frequency step required for frequency tracking according to the load impedance angle threshold, that is, the ultrasonic generator adjusts the output frequency according to the change of the impedance angle and a predetermined control strategy. When the impedance angle is close to the minimum value, it means that the transducer is close to the resonant state. At this time, the frequency adjustment step is reduced for fine-tuning. When the impedance angle has a large deviation from the minimum value, it means that the ultrasonic transducer deviates far from the resonant state. At this time, the frequency adjustment step is increased to quickly approach the resonant frequency. The excitation frequency is dynamically adjusted according to the actual working state of the ultrasonic transducer to achieve fast and accurate frequency tracking, thereby improving the overall performance and efficiency of the ultrasonic surgical knife system.

[0028] (3) The present invention can respond to the drift of the resonant frequency in a timely manner through its fast frequency tracking method, ensuring that the system always operates in the best state, and ensures that the ultrasonic transducer always works in the best state through real-time sampling and compensation mechanism. Even in the case of load changes or voltage and current sampling errors, it can maintain a stable resonant state, thereby improving the reliability and stability of the entire system. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art are briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative work.

[0030] Figure 1 is a block diagram of an automatic frequency tracking method of an ultrasonic surgical knife system according to a preferred embodiment of the present invention;

[0031] Figure 2 is a schematic diagram of an ultrasonic cutter head according to a preferred embodiment of the present invention;

[0032] Figure 3 Schematic diagram of the exterior and interior of an ultrasonic transducer of a preferred embodiment of the present invention;

[0033] Figure 4 It is an ultrasonic generator excitation circuit of a preferred embodiment of the present invention;

[0034] Figure 5 is an equivalent circuit of an ultrasonic transducer of a preferred embodiment of the present invention;

[0035] Figure 6 is an equivalent circuit of the ultrasonic transducer of the preferred embodiment of the present invention when it resonates;

[0036] Figure 7 is a transducer impedance curve of a preferred embodiment of the present invention; Figure 8 It is a frequency locking time diagram obtained by using the frequency automatic tracking technology in the prior art; Fig. 9 It is a frequency locking time diagram obtained by using the fast frequency tracking method of the present invention;

[0037] In the figure: 1. handle; 2. jaws; 3. sleeve; 4. steering knob; 5. handle; 6. closing switch; 7. MAN switch; 8. MIN switch; 9. housing; 10. pre-tightening bolt; 11. sandwich piezoelectric ceramic piece; 12. amplitude transformer. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein. Therefore, the protection scope of the present invention is not limited to the specific embodiments disclosed below.

[0040] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood by specific circumstances.

[0041] like Figure 2 and Figure 3 As shown, a fast frequency tracking method for an ultrasonic surgical knife is applied to an ultrasonic knife system, which includes: an ultrasonic knife head, an ultrasonic transducer connected to the ultrasonic knife head, and an ultrasonic generator connected to the ultrasonic transducer through a cable.

[0042] The ultrasonic transducer comprises: a shell, a pre-tightening bolt arranged in the shell, a sandwich piezoelectric ceramic sheet installed in cooperation with the pre-tightening bolt, and a horn installed at one end away from the pre-tightening bolt.

[0043] The ultrasonic blade head includes: a sleeve, a blade rod and a jaw arranged at one end of the sleeve, and a steering knob installed in cooperation with the other end of the sleeve; the ultrasonic blade head also includes a handle, the handle is installed in cooperation with the steering knob, and a closing switch is arranged on the handle, and a MAX switch and a MIN switch are arranged on the closing switch; the blade rod is connected to the ultrasonic transducer inside the sleeve, and the ultrasonic transducer is connected to the ultrasonic generator through a cable.

[0044] like Figure 4 The figure shows the ultrasonic generator excitation circuit. The full-bridge inverter circuit composed of VT1, VT2, VT3, and VT4 inverts the DC voltage on the output side of the main circuit BUCK chopper into a high-frequency AC voltage, which passes through the high-frequency transformer, the matching inductor L1, and finally the ultrasonic transducer PZT.

[0045] like Figure 1 As shown, the fast frequency tracking method steps include:

[0046] S1, the ultrasonic generator starts and outputs a preset reference frequency f std =55.0KHz;

[0047] S2. At the reference frequency, use the ultrasonic generator to collect the output frequency f std The voltage and current signals of the ultrasonic transducer are used to calculate the phase difference between the two signals and obtain the first phase difference value.

[0048] S3, the ultrasonic generator changes the output frequency to a preset reference frequency f ref ;

[0049] S4. Under the reference frequency, use the ultrasonic generator to collect the output frequency f ref The voltage and current signals when passing through the ultrasonic transducer are calculated, and the phase difference between the two signals is obtained to obtain the second phase difference value.

[0050] S5. Calculate the sampling to get the phase difference and Quickly calculate the resonant frequency f of the ultrasonic knife system s ;

[0051] S6, the ultrasonic generator adjusts the output frequency to the resonant frequency f calculated in S5 s , driving the ultrasonic transducer to work at this frequency;

[0052] S7: The voltage and current of the ultrasonic transducer are sampled in real time through the ultrasonic knife system, and the phase difference of the voltage and current signals is calculated.

[0053] S8, according to the phase difference sampled in real time in S7 The ultrasonic generator adjusts the output excitation frequency in a variable step-size manner to keep the ultrasonic transducer operating in a resonant state.

[0054] Wherein, step S3 reference frequency f ref =56.0KHz, this frequency is close to the anti-resonance frequency of the ultrasonic transducer, and f std With f ref There is a wide enough frequency range between the resonant frequency f s Included.

[0055] In step S5, the resonant frequency f is calculated by an algorithm. s When the equivalent circuit of the ultrasonic transducer is Figure 5 As shown in the dotted box, the equivalent circuit of the ultrasonic transducer includes a dynamic resistor R 1 , dynamic inductance L 1 And the dynamic capacitance C 1 ; R 1 , L 1 , C 1 Form a series branch, and the static capacitance C 0 connected in parallel in the equivalent circuit.

[0056] When the ultrasonic generator excitation frequency meets At this time, the ultrasonic transducer works in the series resonance state, and the series branch equivalent circuit is as follows: Figure 6 As shown, the phase difference between voltage and current is 0, which is equivalent to pure resistance R 1The impedance is the smallest and the output efficiency is the highest; and when the ultrasonic knife system operates in a non-resonant state, the phase difference between the voltage and current is the same as the load impedance angle of the ultrasonic knife head.

[0057] Among them, the ultrasonic transducer equivalent impedance Z std and Z ref The ratio of the imaginary part to the real part, equivalent impedance Z std and Z ref As shown in formula (1):

[0058]

[0059] In formula (1):

[0060] Z std , Z ref : Transducer equivalent impedance;

[0061] ω std ,ω ref : Ultrasonic generator excitation frequency;

[0062] Load impedance angle and The tangent value of and The calculation formula is formula (2):

[0063]

[0064] In formula (2):

[0065] f std and f ref The corresponding voltage and current phase difference at the excitation frequency;

[0066] The corresponding tangent value;

[0067] According to formula (2), the time constant of the equivalent circuit is calculated as: RC =1 / (R 1 C 1 ), τ RL =L 1 / R 1 ,

[0068] As shown in formula (3):

[0069]

[0070] According to the resonant frequency of the ultrasonic transducer series branch resonance

[0071] The resonant frequency f is calculated by formula (3): s Formula (4):

[0072]

[0073] In the above step S5, only the phase difference and The resonant frequency f can be calculated s The traditional method requires a frequency sweep, starting from a frequency far away from the resonant frequency and ending at a frequency exceeding the anti-resonant frequency. Generally, hundreds of phase differences need to be calculated to determine the resonant frequency f. s This step can greatly shorten the time it takes for the ultrasonic generator to initially search for the resonant frequency.

[0074] In step S8, the adjustment step size of the ultrasonic generator excitation frequency is determined by judging the voltage and current phase difference of the real-time sampling. Is it greater than the set phase difference threshold? This judgment is based on the maximum step length step max Adjust the frequency, or with the minimum step size step min Adjust the frequency; and determine the direction of adjusting the ultrasonic generator excitation frequency by judging the voltage and current phase difference sampled in real time Whether it is greater than 0 is used to determine whether to increase or decrease the frequency.

[0075] Among them, the ultrasonic surgical knife transducer is a narrow bandwidth transducer with a very small half-power range, generally slightly greater than 10Hz, and the phase difference threshold used as the step switching benchmark is The selection of affects the resonant frequency tracking performance of the system, especially when the step size is switched. Enables the system to quickly and accurately track the resonant frequency; Improper selection will result in the frequency changing at the maximum step size at the resonant frequency f s Oscillates left and right, and cannot lock on the resonant frequency f s .

[0076] Since the resonant frequency f s Between std and f ref Between, we have formula (5):

[0077] f std ≤f s ≤f ref (5)

[0078] Phase Difference Between and That is, we have formula (6):

[0079]

[0080] The load impedance angle threshold is determined by the ultrasonic transducer impedance curve characteristics. Figure 7 It can be seen that is the load phase angle of the ultrasonic transducer when it is close to the anti-resonance frequency, which is close to 90° and very large; std Change to f s , the ultrasonic transducer load phase angle changes very little, so And when the frequency changes to f s Before, so It can be used as the judgment threshold of the transducer load phase angle, that is, formula (7):

[0081]

[0082] From formula (2) and formula (7), we can know that:

[0083]

[0084] Then the present invention sets That is, when adjusting the direction of the ultrasonic generator excitation frequency, the frequency is increased, and when adjusting the adjustment step of the ultrasonic generator excitation frequency, the maximum step length is used to judge. max Adjust the frequency, or with the minimum step size step min Adjust the frequency.

[0085] Among them, during the working process, the ultrasonic knife load changes in real time, causing the resonant frequency to drift, and the voltage and current errors sampled by the ultrasonic system will also cause the resonant frequency drift, which will cause the transducer to shift from the resonant state. Therefore, during the working process, it is necessary to sample the voltage and current of the transducer in real time, and compensate the excitation frequency according to the state of the transducer shifting from the resonance, so that the transducer always works in the resonant state.

[0086] It should be noted that the core control technology of the ultrasonic generator is the automatic frequency tracking technology, that is, the ultrasonic generator has the function of automatically adjusting the resonant frequency by tracking the changes in the transducer load; during the operation of the ultrasonic transducer, the resonant frequency changes with the changes in the arbor load. The automatic frequency tracking technology samples and filters the voltage and current on the transducer side, and feeds back the amplitude and phase relationship of the output voltage and current to the control chip of the generator. The control chip changes the frequency of the output voltage according to the feedback of the amplitude, phase and other relationships of the output voltage and current to track the current resonant frequency of the transducer.

[0087] The results are as follows Figure 8 and Fig. 9As shown in FIG. 1 , the frequency locking time obtained by the fast frequency tracking method adopted by the present invention and the frequency locking time of the traditional frequency tracking method can be seen that the present invention shortens the time of the transducer detuning state and improves the dynamic response performance of the ultrasonic surgical knife system.

[0088] The above is based on the ideal embodiment of the present invention. Through the above description, relevant personnel can make various changes and modifications without departing from the technical concept of the present invention. The technical scope of the present invention is not limited to the content in the specification, and the technical scope must be determined according to the scope of the claims.

Claims

1. A fast frequency tracking method for an ultrasonic surgical knife, the method being applied to an ultrasonic surgical knife system, the ultrasonic surgical knife system comprising: An ultrasonic blade, an ultrasonic transducer connected to the ultrasonic blade, and an ultrasonic generator connected to the ultrasonic transducer via a cable; wherein the rapid frequency tracking method comprises the following steps: S1, the ultrasonic generator starts and outputs a preset reference frequency f std =55.0KHz; S2. At the reference frequency, use the ultrasonic generator to collect the output frequency f std The voltage and current signals of the ultrasonic transducer are used to calculate the phase difference between the two signals and obtain the first phase difference value. S3, the ultrasonic generator changes the output frequency to a preset reference frequency f ref ; S4. Under the reference frequency, use the ultrasonic generator to collect the output frequency f ref The voltage and current signals when passing through the ultrasonic transducer are calculated, and the phase difference between the two signals is obtained to obtain the second phase difference value. S5. Calculate the sampling to get the phase difference and Quickly calculate the resonant frequency f of the ultrasonic knife system s ; S6, the ultrasonic generator adjusts the output frequency to the resonant frequency f calculated in S5 s , driving the ultrasonic transducer to work at this frequency; S7: The voltage and current of the ultrasonic transducer are sampled in real time through the ultrasonic knife system, and the phase difference of the voltage and current signals is calculated. S8, according to the phase difference sampled in real time in S7 The ultrasonic generator adjusts the output excitation frequency in a variable step-size manner to keep the ultrasonic transducer operating in a resonant state.

2. The method for fast frequency tracking of an ultrasonic surgical knife according to claim 1, characterized in that: In step S3, the reference frequency f ref =56.0KHz.

3. The method for fast frequency tracking of an ultrasonic surgical knife according to claim 1, characterized in that: In step S5, the resonant frequency f is calculated. s When , the equivalent circuit of the ultrasonic transducer includes a dynamic resistor R1, a dynamic inductor L1 and a dynamic capacitor C1; R1, L1 and C1 form a series branch, and the static capacitor C0 is connected in parallel in the equivalent circuit.

4. The method for fast frequency tracking of an ultrasonic surgical knife according to claim 3, characterized in that: When the ultrasonic generator excitation frequency meets At this time, the ultrasonic transducer works in a series resonance state. At this time, the phase difference between voltage and current is 0, which is equivalent to a pure resistance R1 with the smallest impedance and the highest output efficiency.

5. The method for fast frequency tracking of an ultrasonic surgical knife according to claim 4, characterized in that: When the ultrasonic knife system operates in a non-resonant state, the phase difference between the voltage and current is the same as the load impedance angle of the ultrasonic knife head.

6. The method for fast frequency tracking of an ultrasonic surgical knife according to claim 1, characterized in that: The ultrasonic transducer comprises: a housing, a pre-tightening bolt arranged in the housing, a sandwich piezoelectric ceramic sheet installed in cooperation with the pre-tightening bolt, and a horn installed at one end away from the pre-tightening bolt.

7. The method for fast frequency tracking of an ultrasonic surgical knife according to claim 1, characterized in that: The ultrasonic blade head includes: a sleeve, a blade rod and a jaw arranged at one end of the sleeve, and a steering knob installed in cooperation with the other end of the sleeve; the ultrasonic blade head also includes a handle, the handle is installed in cooperation with the steering knob, and a closing switch is arranged on the handle, and a MAX switch and a MIN switch are arranged on the closing switch.

8. The method for fast frequency tracking of an ultrasonic surgical knife according to claim 7, characterized in that: The knife rod is connected to the ultrasonic transducer inside the sleeve, and the ultrasonic transducer is connected to the ultrasonic generator through a cable.

9. The method for fast frequency tracking of an ultrasonic surgical knife according to claim 1, characterized in that: In step S8, the adjustment step length of the ultrasonic generator excitation frequency is determined by judging the voltage and current phase difference of the real-time sampling. Is it greater than the set phase difference threshold? This judgment is based on the maximum step length step max Adjust the frequency, or with the minimum step size step min Adjust the frequency.

10. The method for fast frequency tracking of an ultrasonic surgical knife according to claim 1, characterized in that: In step S8, the direction of adjusting the excitation frequency of the ultrasonic generator is determined by judging the voltage and current phase difference of the real-time sampling. Whether it is greater than 0 is used to determine whether to increase or decrease the frequency.

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