基于FPGA的超声手术刀频率跟踪技术设计

Design of Frequency Tracking Technology of Ultrasonic Scalpel Based on FPGA

超声手术刀在工作过程中由于超声换能器的声阻抗变化、自身发热等情况导致其谐振频率产生漂移,驱动信号的频率难以准确地工作在换能器的谐振频率处,从而导致超声换能器停震或损坏。为解决上述问题,采用等效电路法分析超声换能器的谐振频率特性,设计基于FPGA的频率跟踪方法实时跟踪超声换能器的谐振频率。首先利用DDS产生频率可调节的驱动信号,然后设计相位检测模块实时检测换能器电流和电压的相位差,同时为了提高跟踪效率,通过PID算法进行控制以实现频率跟踪。实验结果表明,所设计的频率跟踪方法可以快速实现频率跟踪,跟踪误差保持在±2Hz内,避免了跟踪过程中出现的反谐振频率跟踪和失锁等问题,具有响应速度快、鲁棒性强等优点。

During the operation of the ultrasonic scalpel,the resonant frequency of the ultrasonic transducer drifts due to the change of acoustic impedance and self-heating of the ultrasonic scalpel,which makes it difficult for the frequency of the driving signal to accurately work at the resonant frequency of the transducer,thus causing the ultrasonic transducer to stop or be damaged.In order to solve this problem,the equivalent circuit method is used to analyze the resonant frequency characteristics of the ultrasonic transducer,and a frequency tracking method based on FPGA is designed to track the resonant frequency of the ultrasonic transducer in real time.First of all,DDS is used to generate drive signals with adjustable frequency.Then a phase detection module is designed to detect the current and voltage phases of the transducer in real time.At the same time,in order to improve the tracking efficiency,frequency tracking is realized by PID algorithm.The experimental results show that the frequency tracking method designed in the experiment can quickly achieve frequency tracking,and the tracking error is kept within±2Hz and avoiding the problems of anti-resonance frequency tracking and locking loss during the tracking process.It has the characteristics of fast response speed and strong robustness.