基于PLL载频跟踪的电容式叶尖间隙测量技术

Technique for Capacitance-Type Blade Tip Clearance Measurement Based on PLL Carrier Frequency Tracking

针对电容调频式叶尖间隙测量中存在的杂散电容问题和叶尖间隙信号的在线检测需求,设计了基于锁相环(PLL)载频跟踪的测量方案.方案中PLL无差载频跟踪环路能够有效地抑制杂散电容造成的缓慢载频漂移;选择1,MHz的中频频率将信号带宽提高到200,kHz,并设计了峰值采集控制时序以提高系统测量效率;理论推导出并用实验数据验证了信号的非线性模型.模拟实验结果表明,测量系统灵敏度高,具备了高速在线检测能力.

A capacitance FM type blade tip clearance measuring scheme based on PLL carrier frequency tracking was designed to cope with the interference of stray capacitance and meet demand of on-line monitoring.The PLL non-difference carrier frequency tracking loop effectively inhibited the slow carrier frequency drift caused by stray capaci-tance.The signal band was set at 200,kHz by choosing 1,MHz as IF frequency and signal peak acquisition control tim-ing was developed to improve the system′s working efficiency.Also the signal′s nonlinear model was derived theoreti-cally and verified.Simulative results show that the system has a high level of sensitivity and an ability of high speed on-line detection.