为提高碳纤维复合材料超声振动钻孔过程中压电换能器频率跟踪的精度及可靠性，以压电换能器等效电路为基础，分析了目前锁相环频率跟踪系统存在的失锁、误跟踪、死锁和跟踪误差大等4种失效形式的原因，指出抵消静态电容是解决跟踪失效的必由之路．据此提出一种基于静态电容补偿法的锁相环频率跟踪技术，该技术可使换能器对锁相环呈现理想的LCR串联谐振特性，有效解决了跟踪失效问题．实验表明：通过该技术，换能器机械谐振频率的跟踪精度可优于-20～10Hz，避免了误跟踪和死锁，跟踪带宽可达6kHz．

In the uhrasonic order to improve the precision and reliability of frequency tracking of piezoelectric transducers during drilling of carbon-fiber composites, four kinds of tracking degradations of the traditional phase-locked loop （PLL） system, namely the lock losing, the mis-tracking, the dead lock and the large tracking error, are ana- lyzed based on the equivalent circuit of piezoelectric transducers. Then, the reasons for the degradations are ex- plained, finding out that to counteract the static capacitance is the only way to overcoming the degradation. Accor- dingly, a PLL frequency tracking technique based on the static capacitance compensation is proposed, by which the transducer is equivalent to an ideal LCR serial resonance circuit, thus the tracking degradations being effectively solved. Experimental results show that, by using the proposed technique, the frequency tracking precision of trans- ducer mechanical resonance is higher than -20 - 10 Hz, that the mis-tracking and the dead lock are effectively overcome, and that the tracking bandwidth is up to 6 kHz.