High-Precision Measurement of Helicopter Inter-Blades Distance Using Millimeter-Wave Radar

To address the measurement requirements for coaxial helicopter blade pitch in complex environments, a high-precision measurement method for upper and lower rotor tip pitch based on FMCW millimeter-wave radar is proposed. By establishing a measurement triggering mechanism based on predicting the moment of upper and lower blade encounters, this approach avoids redundant measurement data while achieving full-cycle measurement of dynamic pitch changes during encounters. A super-resolution ranging algorithm based on CZT combined with Doppler cancellation effectively addresses the impact of FFT aliasing effects and Doppler shifts caused by high-speed blade rotation on ranging accuracy. Experimental results demonstrate that the proposed measurement method covers the dynamic pitch variation range of 200 mm–1600 mm, achieving a maximum RMS error not exceeding 5.8 mm. It also offers advantages such as compact size and strong environmental adaptability.