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This paper presents a novel cost-effective automatic resonance tracking scheme with maximum power transfer (MPT) for piezoelectric transducers (PT). The conventional approaches compensate the PT with complex power factor correction schemes or drive it in resonance using intricate loops with limited operating range. The proposed tracking scheme is b...
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Context 1
... principle of the sensing scheme can be obtained by a simplified model as shown in Fig. 4 with the nodal analysis. Z represents the series impedance of components L m , R m and C m in Fig. 3 ...
Context 2
... í µí°¾ 1 = í µí»¼�í µí¼ 0,í µí± �í µí°¾ í µí±í µí± í µí°¿ í µí± ⁄ , í µí»¼�í µí¼ 0,í µí± � is í µí»¼(í µí± ) value at resonance and approximately equals -R 2 as shown in Fig. 4 and (4). í µí°¾ í µí±í µí± = −1 is the phase inversion of H-bridge in Fig. 5. Although V MFB (s) and V IN (s) are frequency dependent in (6), ...
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... system stability under various loading conditions. Because pure glycerin is commonly used to mimic blood and tissues, the load settling time is measured by changing the mechanical load. The surgical tip is quickly plugged into glycerin and captures V MFB with a single trigger in the oscilloscope. The step response of V MFB is demonstrated in Fig. 14. In the zoomed-in plot, the PT resonates with a 55.4 kHz sinusoidal wave. It takes 10 ms to converge to a higher value, which is longer than the compensated Loop 2 in Section IV-C. This is because the PT is non-ideal. Parasitics will affect the buildup of the amplitude, taking additional time to settle the transient ...
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Citations
... At the series resonant frequency, the dynamic branch impedance is minimized, so the dynamic branch current is at its maximum. Physically, is proportional to the velocity of the piezoelectric transducer [21]. Therefore, the maximum vibration speed can be obtained. ...
... At the series resonant frequency, the dynamic branch impedance Z 1 is minimized, so the dynamic branch current I 1 is at its maximum. Physically, I 1 is proportional to the velocity of the piezoelectric transducer [21]. Therefore, the maximum vibration speed can be obtained. ...
... In the BVD equivalent model, the tip velocity of piezoelectric transducers is linear to the dynamic branch current [21]. ...
Frequency tracking and amplitude control are essential for piezoelectric transducers. Frequency tracking ensures the piezoelectric transducer operates at the resonant frequency for maximum power output, and amplitude control regulates the mechanical motion of the output. This paper presents a novel driver based on a push–pull inverter for piezoelectric transducers. The proposed driver realizes the frequency tracking and amplitude control scheme by a voltage sensing bridge in the case of transformer secondary matching, guaranteeing automatic frequency tracking and precise mechanical functions regardless of environmental and load variations. The proposed scheme is verified by the ultrasonic scalpel and the ultrasonic motor (USM). The experimental results show that this scheme reduces the build-up time from 10 ms to 3 ms and loaded frequency variations from 250 Hz to 200 Hz. In addition, the amplitude control performance was further observed on USM for various loads. The overshoot is less than 5.4% under different load torques. Therefore, the proposed scheme improves the load adaptability and stability of piezoelectric transducers and promotes the application of piezoelectric transducers under various conditions.
... [14][15][16][17] Specifically, the shifting of the resonance frequency is a manifestation of nonlinearity in the vibration behavior. [18][19][20] The ultrasonic transducer operating at resonance can be thought of as a lightly damped resonator. In addition to a certain mass, it also has certain stiffness and an effective damping factor. ...
Pre-tightening torque has a significant impact on the performance of a bolt-clamped high-frequency piezoelectric ultrasonic transducer widely used in wire bonding. To develop a vibratory response-based method for the determination of optimal pre-tightening torque, the vibration amplitude signals of the transducer under different excitation conditions were monitored, and the characteristic parameters of the response, involving the resonance frequency, settling time within the initial transient response, and vibration amplitude of the steady-state stage, were extracted. Based on a series of in-depth tests, analyses, and discussions, the influences that the pre-tightening torque has on the vibratory response properties were investigated. Then, the experimental measurement and the random forest method were combined to determine the optimal pre-tightening torque. The performance test results show that the developed method can give the optimal pre-tightening torque according to the desired vibrational response properties, and it is feasible, effective, and reliable as well as improves the adaptability and flexibility of the high-frequency ultrasonic transducer in the application.
... In order to obtain stable ultrasonic energy, the ultrasonic power source requires two functions, automatic frequency tracking and power regulation [9,10]. A piezoelectric transducer is an oscillating unit that can achieve maximum power transfer only if it is made to work in a resonance state [11,12]. When the system environment and working conditions change, the piezoelectric transducer impedance and series resonance frequency also change [13,14], the frequency tracking function makes the ultrasonic power supply operating frequency follow the transducer series resonance frequency change accurately and timely to ensure that the transducer always works in the resonance state [15]. ...
In the ultrasonic welding system, the ultrasonic power supply drives the piezoelectric transducer to work in the resonant state to realize the conversion of electrical energy into mechanical energy. In order to obtain stable ultrasonic energy and ensure welding quality, this paper designs a driving power supply based on an improved LC matching network with two functions, frequency tracking and power regulation. First, in order to analyze the dynamic branch of the piezoelectric transducer, we propose an improved LC matching network, in which three voltage RMS values are used to analyze the dynamic branch and discriminate the series resonant frequency. Further, the driving power system is designed using the three RMS voltage values as feedback. A fuzzy control method is used for frequency tracking. The double closed-loop control method of the power outer loop and the current inner loop is used for power regulation. Through MATLAB software simulation and experimental testing, it is verified that the power supply can effectively track the series resonant frequency and control the power while being continuously adjustable. This study has promising applications in ultrasonic welding technology with complex loads.
... Typically, ultrasonic mechanical vibration is excited and controlled by PUG's electrical signals. Till date, most PUGs still cannot respond quickly and accurately to the resonance frequency drift caused by the load, temperature, stiffness, processing area, tool wear, and other factors of the ultrasonic vibration system, which leads to the power ultrasonic vibration system operating in the demodulation state at the non-resonant frequency [14,15]. In this state, the amplitude of the vibration device decreases even to zero [16]. ...
... On the strength of possessing characteristics of both ultrasonic welding and laminated additive manufacturing processes, it has been better utilized in material manufacture including metal layered composite structures [52], functionally graded material structures [53], fiber-reinforced metal matrix composite materials [54], smart metal composite materials [55], and sandwich foam honeycomb structures [56][57][58], etc. Especially, ultrasonic-assisted machining technology mainly used in drilling [59], turning [60], milling [16], grinding [16], and impact treatment [61][62][63][64] has been studied in recent decades, which can effectively solve the problems of excessive cutting force, high cutting temperature, severe tool wear, and poor surface quality, and process high-performance materials with high hardness, high brittleness, high wear resistance, and high-temperature resistance, such as titanium alloys, carbon fiberreinforced composite materials, cobalt oxide ceramics, silicon carbide semiconductors. In addition, the PUT has continuously extended its application fields to ultrasonic surgical scalpels [14], ultrasonic vessel sealing [15], ultrasonic deicing [65], ultrasonic-assisted producing 2D nanomaterials [66], non-invasive tissue removal therapy [67], ultrasonic motors [68,69], and ultrasonic wireless power transmission by crossing metal barriers [70][71][72]. Compared with the design requirements in fluid media, the rightmost column of Table 1 clearly shows that the frequency range (20 kHz < f < 70 kHz) is more concentrated. ...
... But DSP chips also have some disadvantages such as high-frequency clocks interference and sampling delay. 3) FPGA chip belongs to a highly flexible reconfigurable semi-custom circuit which contains programmable modules such as logic block, I/O module and interconnection module, so its internal logic function can be arbitrarily set based on demands [15]. Simultaneously, the FPGA chip is a type of Ai chips due to its fine compatibility with artificial intelligence, which experts in parallel processing and peripheral control circuits processing. ...
The power ultrasonic generator (PUG) is the core device of power ultrasonic technology (PUT), and its performance determines the application of this technology in biomedicine, semiconductor, aerospace, and other fields. With the high demand for sensitive and accurate dynamic response in power ultrasonic applications, the design of PUG has become a hot topic in academic and industry. However, the previous reviews cannot be used as a universal technical manual for industrial applications. There are many technical difficulties in establishing a mature production system, which hinder the large-scale application of PUG for piezoelectric transducers. To enhance the performance of the dynamic matching and power control of PUG, the studies in various PUT applications have been reviewed in this article. Initially, the demand design covering the piezoelectric transducer application and parameter requirements for ultrasonic and electrical signals is overall summarized, and these parameter requirements have been recommended as the technical indicators of developing the new PUG. Then the factors affecting the power conversion circuit design are analyzed systematically to realize the foundational performance improvement of PUG. Furthermore, advantages and limitations of key control technologies have been summarized to provide some different ideas on how to realize automatic resonance tracking and adaptive power adjustment, and to optimize the power control and dynamic matching control. Finally, several research directions of PUG in the future have been prospected.
... However, those components may be highly dependent on the characteristic frequency of the piezo ceramic. The phase detection that tracks the operating frequency may become difficult due to harmonic current introduced by other reactive components [9][10][11][12][13]. ...
This paper presents the circuit and control method for piezo-ceramic drives. With the proposed method, a gap is imposed in the transformer core to increase the leakage inductance. This flattens the voltage gain curve of the piezo-ceramic driver over the resonant frequency range, so voltage gain changes are insensitive to frequency changes. In addition, resonant frequency tracking and power control methods are developed, while the circuit is capable of zero-voltage soft-switching such that the circuit operation efficiency can be improved. In order to solidify the practicality of the circuit design, mathematical analysis and experimental validations have been thoroughly performed. The test results help to confirm the effectiveness of the proposed method and demonstrate its practicality in industrial applications.
... A procedure of transmission and acquisition of ultrasound is one of representative energy conversion between electrical domain and mechanical domain. An energy conversion efficiency between different domains can be primarily affected by various conditions such as an actuation voltage, a center frequency, a pulse shape, and an impedance matching [6][7][8][9][10][11][12][13][14][15][16]. These conditions are related to a nature of ultrasound transducer. ...
... Previous works for high-power continuous actuation of transducer have focused on a conditioning of resonance state [6][7][8][9][10][11]. That is, a primary goal was to make a transducer impedance lowest and purely resistive so that the impedance phase becomes zero. ...
... Phase-locked loops (PLLs) were widely employed to adjust a phase difference between actuation voltage and current. However, previous works of [6][7][8][9][10][11] needed additional current sensors for phase monitoring. Also, the aforementioned works only considered continuous actuations without receiving echo signals. ...
This paper proposes a center frequency tracking scheme to optimize a pulse-echo response of ultrasonic A-mode scanner. A pulse-echo response of A-mode scanner represents an overall energy conversion characteristic from an actuation to an acquisition. A center frequency for optimized pulse-echo response can be varied depending on an actuation voltage, an acoustic medium, etc. Most of previous frequency tracking methods have focused on high-power continuous actuation applications, and have relied on a monitoring of phase difference between actuating voltage and current with auxiliary sensors. This work focuses on a monitoring of a peak envelope of echo without additional sensors. We employ a momentum based gradient ascent algorithm along with a finite state machine to track an optimum center frequency so that a peak envelope of echo becomes the maximum value. The proposed frequency tracking scheme was implemented on a field programmable gate array for real-time operation. We performed repetitive measurements to verify consistent frequency tracking performances for different acoustic mediums. The A-mode scanner adaptively tracked corresponding center frequencies for each of mediums within an average error of 61.7 kHz. When the A-mode scanner was in a steady state, an increment of signal-to-noise ratio (SNR) of echo was 7.4 dB, and an axial resolution was improved by 32.5 %.
... At this time, the resonance frequency is called the mechanical resonance frequency. In addition, since the actual operation process times of many ultrasonic systems are short (seconds), the RFT time is an important factor [19,20]. Among them, in the case of the medical ultrasonic system to be applied in this thesis, it can be said that the high-speed RFT is even more important because it can cause problems (e.g., skin necrosis) due to heat [21]. ...
... As described above, since the RFT method in the ultrasonic system has many factors to consider, related research is being actively conducted via various methods. Methods include tracking parallel resonance frequency [9], maximum power [12,20,22], maximum admittance [23], maintaining a constant amplitude [24][25][26][27][28], etc.; various methods have been attempted and implemented. Although these methods have obtained relatively good results, most have complex structures and problems that can only be applied to a specific system or field. ...
... The other arm is a mechanical part consisting of a dynamic capacitor C 1 , a dynamic inductor L 1 , and a dynamic resistance R 1 , which directly affects the mechanical output. As can be seen from the equivalent model, the PT has a structure with two resonance points as shown in the following equation [20,30,33]. ...
When driving the piezoelectric transducer (PT: piezo transducer), which is a key device, it is important for the ultrasonic system (using ultrasonic waves of 20 kHz or higher) to operate at a resonant frequency that can maximize the conversion of mechanical energy (vibration) from electrical energy. The resonant frequency of the PT changes during the actual operation according to the load fluctuations and environmental conditions. Therefore, to maintain a stable output in an ultrasonic system, it is essential to track the resonant frequency in a short time. In particular, fast resonant frequency tracking (RFT: resonant frequency tracking) is an important factor in the medical ultrasonic system, i.e., the system applied in this thesis. The reason is that in the case of a medical ultrasonic system, heat-induced skin necrosis, etc., may cause the procedure to be completed within a short period of time. Therefore, tracking the RFT time for maximum power transfer is an important factor; in this thesis, we propose a new high-speed RFT method. The proposed method finds the whole system resonance frequency by using the transient phenomenon (underdamped response characteristic) that appears in an impedance system, such as an ultrasonic generator, and uses this to derive the mechanical resonance frequency of the PT. To increase the accuracy of the proposed method, parameter fluctuations of the pressure of the PT, the equivalent circuit impedance analysis of the PT, and a MATLAB simulation were performed. Through this, the correlation between the resonance frequency of the ultrasonic system, including the LC filter with nonlinear characteristics and the mechanical resonance frequency of the PT, was analyzed. Based on the analyzed results, a method for tracking the mechanical resonance frequency that can transfer the maximum output to the PT is proposed in this thesis. Experiments show that using the proposed high-speed RFT method, the ultrasonic system can track the mechanical resonance frequency of the PT with high accuracy in a short time.
... Frequency tracking is a significant method by which to maintain the stable operation of the ultrasonic cutting system in resonance during cutting [6]- [8]. Via frequency tracking, the input frequency of the ultrasonic power supply is adjusted to meet the resonance frequencies of the ultrasonic cutting system, thereby providing a sufficient vibration amplitude [9], [10]. There are two resonance frequencies in the ultrasonic cutting system [11], the first of which is the mechanical resonance frequency determined by the structure, external force, and temperature; the second is the electrical resonance frequency determined by the circuits in the ultrasonic cutting system. ...
Ultrasonic cutting is a superior machining process for brittle materials, owing to its capability to reduce the cutting force and improve the surface quality. To avoid the destructive instability of ultrasonic vibration induced by the cutting force, the excitation frequency of the ultrasonic system must reliably track its resonance frequency. However, it remains challenging for the conventional frequency tracking methods via one parameter to simultaneously achieve both high response rate and high tracking accuracy. This study proposes that more than one parameter could be coupled to get advantages from each parameter. A frequency tracking method via the synergetic control of circuit phase and current of the ultrasonic system was proposed as an example. This method utilizes the phase to responsively determine the tracking direction, and uses the characteristic current as the endpoint frequency to ensure accuracy. Theoretical analyses and numerical simulations were conducted to demonstrate that the proposed method can accurately track the frequency of maximum vibration amplitude with a higher response rate than conventional methods. Moreover, ultrasonic cutting tests were performed on Nomex composites to evaluate the machining performance of the ultrasonic system with the proposed method. The experimental results verify that the proposed frequency tracking method enables the ultrasonic system to reach a stable state with a shorter response time, which is beneficial for the reduction of cutting-induced defects.
... However, as ultrasonic transducers work at frequencies other than resonance, it must result in poor power conversion and increased self-heating [19]. Furthermore, on account of the magnitude of the electrical impedance changing rapidly near its resonance, three loss factors, including dielectric and elastic and piezoelectric losses, become larger, which lead to generate significant heat and result in low efficiency of the piezoelectric transducers [20,21]. And therefore, it is of great significance to study the temperature effects on resonance frequency of lead zirconate titanate (PZT) material. ...
The time-dependent resonance frequency at different heating temperatures was studied for the Pb(Ti0.52Zr0.48)O3 widely applied to power ultrasonic transducers. The prediction model for the changes of resonance frequency (Δfs) was developed using the response surface methodology based on central composite design. The results of significance and analysis of variance (ANOVA) tests have proved that the prediction model has an adequate approximation to the actual values. An evaluation of the interaction effects of temperature and time parameters, heating temperature (Tc), heating time (Tt), and aging time (ta) revealed a decreasing tendency towards the resonant frequency. As the Tc is increased, the Δfs shows three regions with different variation tendency. The Δfs is slightly decreased with increasing Tt and has slow-motion escalating trend with increasing ta. The irreparability variation of resonant frequency revealed in response surface plots shows that Tc and Tt have significant effects on the piezoelectric properties of Pb(Ti0.52Zr0.48)O3. The study of aging effects on resonance frequency at different temperatures could open a road to promote the practical application of PZT-based ceramics automatic tuning.
Graphical abstract
... When the system frequency is the resonant frequency of the transducer, the transducer shows pure resistance and the load current is the largest. The maximum current method is easy to realize, but the tracking sensitivity is not high and the stability is poor [9][10][11]. Therefore, the phase difference method based on PI control is adopted in this paper, which can effectively track the series resonant frequency of the transducer and solve the problem that the series resonant point drift has great influence on the performance of the transducer. ...
In view of the low output power and high power density of ultrasonic power supply, a high power ultrasonic power supply based on 9-level inverter technology is proposed. The inverter of the power supply consists of two H-bridge units cascaded to form a 9-level converter, which outputs the 9-level voltage waveform, which can significantly improve the output power of the ultrasonic power supply, reduce the inductance of the matching network, and reduce the power density of the ultrasonic wave. The phase difference method based on PI control is used to track the resonance frequency. By analyzing the system structure, working principle and control strategy of the ultrasonic power supply, modeling and simulation were conducted on Matlab/Simulink to verify the feasibility and effectiveness of the scheme.
