Квашнин С.Е. «Снижение потерь в ультразвуковых пьезокерамических преобразователях для хирургии» Биомедицинская радиоэлектроника, № 10, с. 9-14 (2011)

Проведен анализ влияния алгоритмов управления пьезокерамическим электроакустическим преобразователем продольных колебаний на его коэффициент полезного действия и мощность, рассеиваемую в преобразователе в процессе работы в режимах холостого хода и под нагрузкой. Показано, что использование алгоритмов управления, обеспечивающих поддержание резонансного режима работы с одновременной стабилизацией амплитуды колебаний рабочего окончания волновода-инструмента, снижает мощность тепловых потерь в преобразователе и колебательной системе в 3–5 раз, позволяя существенно увеличить продолжительность непрерывной работы колебательной системы, что особенно важно для систем, работающих на больших мощностях. Даны рекомендации по выбору коэффициентов усиления для волноводов-инструментов в зависимости от видов их работы на биологических тканях. Получены расчетные математические модели, в которых основным критерием являлось условие минимальности нагрева при заданной амплитуде колебаний рабочего окончания при номинальной нагрузке со стороны обрабатываемой ткани. Ultrasonic surgical instruments of longitudinal vibrations are used for cutting, coagulation, destruction, tissues separation, to destroy pathogenic microflora in infected wounds and cavities. However, the electro-acoustic transducers (EAT), used in these tools get heated significantly in the process. Mathematical modeling of EAT heating at different load impedance and different amplitudes was carried out for three EATs of longitudinal vibrations, based on the Langevin scheme and being double half-wave transducers with similar geometric characteristics and the same materials of all EAT parts. Working resonance frequencies of all EATs matched. The internal dissipation of mechanical energy was described in the ultrasonic vibration system materials as the elastic-viscous friction model. Steady-state forced vibrations with frequency ω were considered. The electrical active output resistance of the ultrasonic generator was assumed to be equal to 10 Ohms, and reactive resistance was assumed to be equal to zero. The longitudinal vibrations calculations were carried out for different values of load impedance at the EAT working tip. They resulted in dependences of the longitudinal displacement amplitude of the EAT working end, the EAT electrical impedance, EAT efficiency as a function of the mechanical load impedance Z_E real part at the EAT working end. It is that The EAT work in the mean values of load impedance (15 to 40 NS / m) per transducer is shown to be the most efficient due to high (70 to 92%) values of efficiency, EAT low heating, and the system low sensitivity to the load. It was noted that the modes of the EAT weak loading lead to the EAT significant heating. The two control algorithms of ultrasonic vibration system heating were compared: A) the resonance frequency maintenance, B) the maintenance of resonance frequency and a constant amplitude of mechanical vibrations of the EAT working end. The use of the control algorithm B proved reduction of the heat losses in the transducer and in the vibration system many times compared to the control algorithm A. Assuming that during the surgical manipulation the system is in the idle mode for K% of time, and is at rated load for (1–K)% of time, the ratio of average power dissipation to the power dissipation at nominal load for K = 20% is 3–27, for K=40% is 5–27 for algorithm A. While using the control algorithm B, the average power dissipation to the power dissipation at nominal load is equal to 1.

Карпухин В.А., Вишнева Н.В., Косоруков А.Е. «Алгоритм многочастотного анализа электрической мощности пьезопреобразователя при ультразвуковой обработке биологических тканей» Биомедицинская радиоэлектроника, № 10, с. 15-20 (2011)

Исследовано влияние числа разрядов задаваемых данных и коэффициентов на погрешность расчета значений электрических трансформант при инструментальной реализации. Установлено, что метод многочастотного анализа активной электрической мощности одновременно на трех частотах в реальном масштабе времени позволяет вычислять значения электрических трансформант акустических характеристик системы при ультразвуковом воздействии на биологические ткани с погрешностью не превышающей 4 %. Efficiency of medical ultrasonic influence is defined, first of all, by the acoustic capacity absorbed by processed biological tissues which depends on mechanical fluctuations amplitude of ultrasonic oscillatory system working part and biological tissues acoustic impedance. However, at stable amplitude of oscillatory system working part change of acoustic characteristics of contact zone can result not only in efficiency decrease of medical influence, but also to burns and necrosis processed biological tissues. Indemnification of acoustic impedance changes of interaction zone is necessary for maintenance of medical influence efficiency. One of ways of indemnification is dynamic fine tuning of amplitude and frequency of ultrasonic influence on the basis of acoustic capacity values analysis. Working out and verification of algorithm of multifrequency analysis method of the active electric capacity consumed PEAT, and error estimations of electric parameters values calculation at its tool realization is the purpose of the present paper. The algorithm of multifrequency analysis method of electric capacity has been realized in the environment of System View. Categories number influence of set data and factors on an error of electric parameters values calculation is investigated at tool realization. It is established that multifrequency analysis method of active electric capacity simultaneously on three frequencies in real time allows to calculate electric parameters values of system acoustic characteristics at ultrasonic influence on biological tissues with a margin error not exceeding 4%.