Method for controlling frequency applied to probe of ultrasonic surgical device

Abstract

The present invention relates to a method for controlling a frequency applied to a probe of an ultrasonic surgical device. According to the present invention, the frequency control method includes the steps of: obtaining a sinusoidal current waveform from a voltage waveform applied to a probe in the form of a square wave through a BLT driver; sampling the current waveform with an ADC and selecting a first point and a second point having ((θ-α) and θ), respectively, in the current waveform; calculating the phase (θ) of the current by using the ratio of the magnitude (a1) of the current measured at the first point and the magnitude (a2) of the current measured at the second point; and adjusting the frequency of the voltage applied to the probe so that the phase (θ) of the current coincides with a target phase of the voltage. Accordingly, according to the present invention, an output frequency changed by a change in the size or the position of an ultrasonic probe, a surgical site, a distance between the probe and an object, and a surrounding environment can be adaptively matched to a resonance frequency band.

Description

Method for controlling the frequency applied to the probe of an ultrasonic surgical device

[0001] The present invention relates to a method for controlling a frequency applied to a probe of an ultrasonic surgical device, and more specifically, to a method for estimating a phase of a current by sampling the magnitude of a current in three parts of a voltage phase applied to a probe of an ultrasonic surgical device, and controlling a driving frequency to match the phase of an applied voltage waveform.

[0002] Conventional liposuction often has side effects that vary from person to person, such as lumpiness after surgery, skin necrosis in the surgical area, severe swelling and bruising, extreme pain, nerve damage, and skin sagging.

[0003] Therefore, ultrasound liposuction is increasingly being used to reduce side effects and increase patient satisfaction. Ultrasonic liposuction effectively removes fat cells by applying ultrasound waves vibrating tens of thousands of times per second to the fat layer.

[0004] Figure 1 is a drawing illustrating an ultrasonic surgical device for ultrasonic liposuction.

[0005] As illustrated in FIG. 1, an ultrasonic surgical device (100) used for ultrasonic liposuction includes a handpiece (110), an ultrasonic driving unit installed within the handpiece (110), and a probe (120) configured such that one end is connected to the ultrasonic driving unit within the handpiece and one end extends outside the handpiece.

[0006] Probes vary in thickness, length, and number of grooves depending on the surgical site and individual characteristics. The longer the probe, the narrower the resonator bandwidth (ΔF) relative to the center frequency.

[0007] Then, there was a problem that the quality factor, i.e. the Q factor, increased, heat was generated in the probe, and when vibration occurred, the output frequency was outside the ΔF range, and there was no vibration or movement.

[0008] In order to maintain a constant ultrasonic output, the current waveform must be monitored in real time, and the input driving frequency must be adjusted periodically through PID control so that the resonance frequency is automatically located at the center of the square wave.

[0009] The technology underlying the present invention is disclosed in Republic of Korea Patent Publication No. 10-2020-0051283 (published on April 28, 2020).

[0010] Thus, according to the present invention, a method is provided for estimating the phase of the current by sampling the magnitude of the current in three parts of the voltage phase applied to the probe of an ultrasonic surgical instrument and controlling the driving frequency to match the phase of the applied voltage waveform.

[0011] According to an embodiment of the present invention for achieving such a technical task, the method comprises the steps of: obtaining a current waveform in the form of a sinusoidal wave from a voltage waveform applied to a probe in the form of a square wave or a sinusoidal wave through a BLT driver; sampling the current waveform with an ADC, and selecting a first point and a second point in the current waveform whose phases are (θ-α) and (θ), respectively; calculating a phase (θ) of the current using a ratio of a magnitude (a1) of the current measured at the first point and a magnitude (a2) of the current measured at the second point; and adjusting a frequency of a voltage applied to the probe so that the phase (θ) of the current matches a target phase of the voltage.

[0012] The method may further include a step of calculating the magnitude (A) of the current using the phase (θ) of the current, a step of estimating the applied power value (P) using the magnitude (A) of the current, and a step of comparing the estimated power value (P) with a target power value according to a power level set for each probe and adjusting the magnitude of the applied voltage so that they match each other.

[0013] The ratio of the magnitude of the current measured at the first point (a1) to the magnitude of the current measured at the second point (a2) can be expressed as follows.

[0014]

[0015] The step of calculating the phase (θ) of the above current can be calculated using the following mathematical formula.

[0016]

[0017] The step of selecting a third point having a phase of (θ+α) in the current waveform may further include a step of calculating the phase (θ) of the current using a ratio of the magnitude (a3) ​​of the current measured at the third point and the magnitude (a2) of the current measured at the second point.

[0018] The ratio of the magnitude of the current measured at the third point (a3) ​​to the magnitude of the current measured at the second point (a2) can be expressed as follows.

[0019]

[0020] The step of calculating the phase (θ) of the above current can be calculated using the following mathematical formula.

[0021]

[0022] The first point may be located at a point where the current value increases over time, and the third point may be located at a point where the current value decreases over time.

[0023] The step of controlling the frequency of the voltage applied to the above probe can control the frequency using a PID control algorithm.

[0024] The step of calculating the phase (θ) of the current can determine the phase (θ) of the current by using the average value of each calculated phase (θ).

[0025] In this way, according to the present invention, the output frequency, which changes depending on the size or position of the ultrasonic probe, the surgical site, the distance between the probe and the target, and the surrounding environment, can be adaptively matched to the resonance frequency band.

[0026] Figure 1 is a drawing illustrating an ultrasonic device for ultrasonic liposuction.

[0027] Fig. 2 is a schematic diagram for explaining a frequency control device according to an embodiment of the present invention.

[0028] FIG. 3 is a flowchart for explaining a frequency control method using a frequency control device according to an embodiment of the present invention.

[0029] Figure 4 is a drawing for explaining step S320 shown in Figure 3.

[0030] Figure 5 is an exemplary diagram for explaining step S340 illustrated in Figure 3.

[0031] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings. In this process, the thickness of lines and the sizes of components depicted in the drawings may be exaggerated for clarity and convenience of explanation.

[0032] Furthermore, the terms described below are defined based on their functions within the present invention, and may vary depending on the intent or custom of the user or operator. Therefore, the definitions of these terms should be based on the overall content of this specification.

[0033] First, the bolt-clamped Langevin transducer (BLT) installed in the ultrasonic driving unit of the ultrasonic surgical device (100) illustrated in Fig. 1 generates stable ultrasonic waves with respect to temperature input power and load fluctuations.

[0034] Power is transferred most efficiently when the phases of the applied voltage and the flowing current are aligned, which occurs when the resonant frequency of the bolt-tight Lanz square transducer (BLT) matches the driving frequency of the driver.

[0035] Therefore, in the embodiment of the present invention, the purpose is to adjust the driving frequency so that the phase of the current flowing in the bolt-tightening lanz-type oscillator (BLT) and the phase of the applied voltage waveform are matched by using the frequency control device (200).

[0036] Hereinafter, a frequency control device (200) according to an embodiment of the present invention will be described in more detail using FIG. 2.

[0037] Fig. 2 is a schematic diagram for explaining a frequency control device according to an embodiment of the present invention.

[0038] As illustrated in FIG. 2, a frequency control device (200) according to an embodiment of the present invention includes a waveform acquisition unit (210), a phase calculation unit (220), a current magnitude calculation unit (230), a power value estimation unit (240), a frequency adjustment unit (250), and a voltage magnitude adjustment unit (260).

[0039] First, the waveform acquisition unit (210) acquires the waveform of the current applied to the bolt-tightening lanz square transducer (BLT) driver.

[0040] The phase calculation unit (220) selects the first point, the second point, and the third point based on the phase of the current voltage applied to the ultrasonic surgical device (100), and calculates the phase (θ) of the current using the magnitude of the current measured at the first point, the second point, and the third point.

[0041] The current magnitude calculation unit (23) calculates the current magnitude using the phase (θ) of the generated current.

[0042] The power value estimation unit (240) estimates the power value using the root mean square (RMS) of the calculated current size and the voltage size and duty cycle of the driving signal.

[0043] The frequency control unit (250) controls the voltage frequency applied to the probe using a PID (Proportional-Integral-Differential controller) control algorithm so that the phase (θ) of the generated current matches the target phase of the voltage.

[0044] Finally, the voltage magnitude control unit (260) compares the estimated power value with the target power value defined according to the power level set for each probe to control the voltage magnitude.

[0045] Hereinafter, a method for controlling the frequency applied to the probe of an ultrasonic surgical device (100) using a frequency control device (200) will be described in more detail using FIGS. 3 and 4.

[0046] FIG. 3 is a flowchart for explaining a frequency control method using a frequency control device according to an embodiment of the present invention.

[0047] As illustrated in FIG. 3, a frequency control device (200) according to an embodiment of the present invention obtains a current waveform in the form of a sinusoidal wave from a voltage waveform applied in the form of a square wave to a probe through a bolt-tightening lanz-type transducer (BLT) driver (S310).

[0048] The current flowing in the LC circuit of the bolt-tightening rectifier (BLT) driver appears in the form of a sine wave near the resonant frequency.

[0049] Therefore, the waveform acquisition unit (210) acquires a current waveform in the form of a sine wave.

[0050] When step S310 is completed, the phase generator (220) samples the acquired current waveform with an ADC (Analog-to-digital converter) to select multiple points (S320).

[0051] Figure 4 is a drawing for explaining step S320 shown in Figure 3.

[0052] As illustrated in Fig. 4, the phase calculation unit (220) samples the magnitude of the current using an ADC to correspond to three parts of the applied voltage phase in order to estimate the phase of the current. At this time, the voltage and current signals and sampling positions illustrated in Fig. 4 represent an ideal case.

[0053] The sampling position is set based on the phase of the current voltage. At this time, the sampling interval is Δt, and the driving frequency applied to the bolt-tightening Lanz square transducer (BLT) driver is Then, θ1, θ2 and θ3 can be expressed as in the following mathematical expression 1.

[0054]

[0055] The phase generator (220) selects a first point (P1) corresponding to θ1, a second point (P2) corresponding to θ2, and a third point (P3) corresponding to θ3. At this time, it is preferable that the first point (P1) is located at a point where the current value increases over time, and the third point (P3) is located at a point where the current value decreases over time.

[0056] Next, the phase calculation unit (220) calculates the phase (θ) of the current using the ratio of the magnitude (a1) of the current measured at the first point (P1) and the magnitude (a2) of the current measured at the second point (P2) and the ratio of the magnitude (a3) ​​of the current measured at the third point (P3) and the magnitude (a2) of the current measured at the second point (P2) (S330).

[0057] To elaborate, voltage phase 90( In order to analytically calculate the phase (θ) and magnitude (A) of the current in [rad], the measured current is assumed to be a pure sine wave.

[0058] Then, the magnitude of the current (a1) at the first point (P1), the magnitude of the current (a2) at the second point (P2), and the magnitude of the current (a3) ​​at the third point (P3) can be expressed as in the following mathematical expression 2.

[0059]

[0060] Next, the phase calculation unit (220) calculates the ratio of the magnitude (a1) of the current at the first point (P1) obtained from the above mathematical formula 2 and the magnitude (a2) of the current at the second point (P2) using the following mathematical formula 3.

[0061]

[0062]

[0063] Here, the magnitude of the current (a1) at the first point (P1) and the magnitude of the current (a2) at the second point (P2) are measured values, and sin( ) and cos( ) is a specific driving frequency ( ) and sampling interval (Δt), so it can be expressed as the following mathematical expression 4.

[0064]

[0065] And, voltage phase ( ) of the current phase ( ) can be substituted into the following mathematical expression 5.

[0066]

[0067] In addition, the phase calculation unit (220) calculates the ratio of the current size (a3) ​​of the third point (P3) obtained from the above mathematical expression 2 and the current size (a2) of the second point (P2) using the following mathematical expression 6.

[0068]

[0069]

[0070] And, as explained above, the generated mathematical expression 6 is the current size (a3) ​​of the third point (P3) is the measured value, and sin( ) and cos( ) is a specific driving frequency ( ) and sampling interval (Δt), so it can be expressed as the following mathematical expression 7.

[0071]

[0072] At this time, the two denominators in mathematical expressions 4 and 7 can be expressed as the same value as in mathematical expression 8 below.

[0073]

[0074] Therefore, the above mathematical expressions 4 and 7 can be substituted as in the following mathematical expression 9.

[0075]

[0076] And, voltage phase ( ) of the current phase ( ) can be substituted into the following mathematical expression 10.

[0077]

[0078] When step S330 is completed, the frequency control unit (260) controls the frequency of the voltage applied to the probe so that the phase of the generated current matches the target phase of the voltage (S340).

[0079] Figure 5 is an exemplary diagram for explaining step S340 illustrated in Figure 3.

[0080] As shown in Fig. 5, the frequency control unit (260) calculates the current phase ( ) and target phase of voltage ( ) to adjust the frequency of the driving voltage.

[0081] Meanwhile, the phase obtained through mathematical expression 5 ( ) and the phase obtained through mathematical expression 10 ( ) may be the same value or different values. In the following, for convenience of explanation, the phase obtained through mathematical expression 5 is ) in the first phase ( ) and the phase obtained through mathematical expression 10 ( ) to the second phase ( ) is called.

[0082] Phase 1 ( ) and the second phase ( ) are the same, the frequency control unit (260) has the first phase ( ) and the second phase ( ) among any of the phases ( ) is used to control the frequency of the voltage.

[0083] On the other hand, the first phase ( ) and the second phase ( ) are different, the frequency control unit (260) sets the first phase ( ) and the second phase ( ) using the average value of the final phase ( ) and the resulting final phase ( ) is used to control the frequency of the voltage.

[0084] When steps S320 to S340 are completed, the current magnitude calculation unit (230) calculates the current phase ( ) is used to calculate the current size (S350).

[0085] To elaborate, the current magnitude calculation unit (230) calculates the current phase ( ) is substituted into the following mathematical expression 11 to calculate the current size (A).

[0086]

[0087] When step S350 is completed, the power value estimation unit (240) estimates the power value using the size (A) of the calculated current (S360).

[0088] The power value estimation unit (240) estimates the power value (P) using the following mathematical expression 12.

[0089]

[0090] Here, represents the voltage magnitude of the driving signal, represents the current's power value (Root Mean Square, RMS). At this time, Is can be replaced with

[0091] Finally, the voltage size control unit (260) controls the voltage size using the estimated power value (P) (S370).

[0092] That is, the voltage magnitude control unit (260) compares the estimated power value (P) with the target power value according to the power level set for each probe and controls the magnitude of the voltage applied so that they match each other.

[0093] In this way, the frequency control device according to the present invention can adaptively match the output frequency, which changes depending on the size or position of the ultrasonic probe, the surgical site, the distance between the probe and the target, and the surrounding environment, to the resonant frequency band.

[0094]

[0095] While the present invention has been described with reference to the embodiments illustrated in the drawings, these are merely exemplary, and those skilled in the art will understand that various modifications and equivalent embodiments are possible. Therefore, the true technical protection scope of the present invention should be determined by the technical spirit of the following claims.

[0096] <Explanation of symbols>

[0097] 100: Ultrasonic surgical device

[0098] 110: Handpiece

[0099] 120: Probe

[0100] 200: Frequency control device

[0101] 210: Waveform acquisition unit

[0102] 220: Phase generation unit

[0103] 230: Current size calculation unit

[0104] 240: Power value estimation unit

[0105] 250: Frequency control unit

[0106] 260: Voltage size control unit

Claims

1. A step of obtaining a current waveform in the form of a sinusoidal wave from a voltage waveform applied to the probe in the form of a square wave or sinusoidal wave through a BLT driver. A step of sampling the above current waveform with an ADC and selecting a first point and a second point in the current waveform whose phases are (θ-α) and (θ), respectively; A step of calculating the phase (θ) of the current using the ratio of the magnitude (a1) of the current measured at the first point and the magnitude (a2) of the current measured at the second point, and A frequency control method comprising a step of adjusting the frequency of a voltage applied to a probe so that the phase (θ) of the current matches the target phase of the voltage.

2. In paragraph 1, A step of calculating the magnitude (A) of the current using the phase (θ) of the above current, A step of estimating the applied power value (P) using the magnitude (A) of the above current, and A frequency control method further comprising a step of comparing the estimated power value (P) with the target power value according to the power level set for each probe and adjusting the magnitude of the voltage applied so that they match each other.

3. In paragraph 1, A frequency control method in which the ratio of the magnitude of the current measured at the first point (a1) and the magnitude of the current measured at the second point (a2) is expressed as follows:

4. In paragraph 3, The step of calculating the phase (θ) of the above current is: Frequency control method calculated using the following mathematical formula:

5. In paragraph 1, A step of selecting a third point whose phase is (θ+α) in the above current waveform, A frequency control method further comprising a step of calculating the phase (θ) of the current by using the ratio of the magnitude (a3) ​​of the current measured at the third point and the magnitude (a2) of the current measured at the second point.

6. In paragraph 5, A frequency control method in which the ratio of the magnitude of the current measured at the third point (a3) ​​and the magnitude of the current measured at the second point (a2) is expressed as follows:

7. In paragraph 6, The step of calculating the phase (θ) of the above current is: Frequency control method calculated using the following mathematical formula:

8. In paragraph 5, The above first point is located at the point where the current value increases over time, The above third point is a frequency control method located at a point where the current value decreases over time.

9. In paragraph 1, The step of controlling the frequency of the voltage applied to the above probe is: A frequency control method that adjusts frequency using a PID control algorithm.

10. In paragraph 4 or paragraph 7, The step of calculating the phase (θ) of the above current is: A frequency control method for determining the phase (θ) of a current by using the average value of the phases (θ) of each generated current.

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