Design and validation of a spring-mass-based lift measurement platform for FWMAVs under strong flapping disturbances

This paper aims to achieve resolvable, real-time lift measurement of flapping wing micro air vehicles (FWMAVs) under strong flapping disturbances. To address the challenge of obtaining resolvable lift signals in high-noise environments caused by unsteady aerodynamics and vibrational noise from high-frequency flexible flapping wings, a novel lift measurement method is proposed, and a spring-mass lift measurement platform (SM-LMP) is developed. The platform utilizes the mechanical filtering characteristics of a single-degree-of-freedom spring-mass system, combined with a simple and fast post-processing low-pass filter, to effectively suppress vibration noise induced by reciprocating flapping motions. To verify its effectiveness, comparative experiments were conducted between the SM-LMP system and direct measurement using a Nano17 sensor. Based on theoretical analysis, five springs with different stiffness coefficients were designed, and SM-LMP parameters were optimized experimentally. Finally, the SM-LMP’s ability to resolve FWMAV lift was evaluated using two wings with different chord lengths under five driving voltage conditions. Measurement results demonstrate high agreement between the SM-LMP and direct Nano17 measurements (NRMSE < 5%), validating the platform’s effectiveness. Spring stiffness can be customized for different FWMAV configurations; in this study, the SM-LMP performed optimally with a spring stiffness of k = 15.31 N/mm for the measured hummingbird-inspired vehicle. Tests under varying chord lengths, five driving voltages, dynamic angle of attack variations and asymmetric wing root configurations demonstrate that the SM-LMP effectively determines real-time lift range without relying on signal averaging, successfully preserving the aerodynamic signal characteristics within each flapping cycle and enabling resolvable real-time lift signal measurement. By integrating a spring-mass system as a physical pre-processing method with post-processing low-pass filtering, resolvable real-time lift measurement are achieved, reducing vibration noise by an order of magnitude compared to direct Nano17 measurements (RMS from 0.7746 to 0.0214 N, and SNR from −15.2849 to 15.7406 dB).