Design of the resonant frequency tracking system of a phacoemulsification handpiece operated in the cold phacoemulsification mode
In order to solve the problems of easy loss of resonant frequency as well as high thermal damage in the conventional frequency tracking method of phacoemulsification handpiece,a resonant frequency tracking system for the phacoemulsification handpiece in cold phacoemulsification mode is proposed in this study.Firstly,a suitable impedance matching network is designed so that the series and parallel resonant frequencies of the resonant network are far away from each other to more than 1 kHz,which enlarges the reliable frequency tracking range of the system and avoids the problem of false tracking of the resonant frequency.Then,using the principle that the voltage and current phases at both ends of the phacoemulsification handpiece are the same in the resonant state,the frequency of the drive signal is adjusted according to the overshooting and lagging relationship between the voltage and current phases in the resonant network in order to maintain the handpiece in resonance.The handpiece is operated in a pulsed cold phacoemulsification mode that alternates between heat production and heat dissipation,thus reducing thermal damage to the handpiece and the human eye during the emulsification process.The actual frequency tracking experiments show that the frequency tracking system tracks rapidly and accurately,and the phacoemulsification handpiece works stably,with large amplitude and high efficiency.The handpiece works(10 ms)and dissipates heat(90 ms)alternately in a cycle of 100 ms,the effective tracking range of the system is more than 2 kHz,the resolution of frequency adjustment is 10 Hz,the tracking time is about 3 ms,and the amplitude can reach more than 100 µm,which meets the frequency tracking requirements in phacoemulsification cataract surgery.
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