Abstract:

A bimorph piezoelectric cantilever structure is introduced as sensor for icing detection. First of all, the resonant frequencies of the piezoelectric cantilever with water droplet and ice attached are calculated by using the finite element method (FEM), and the results are inspected through error evaluation with the help of an Agilent 35670A dynamic signal analyzer and a traditional transmission measuring method. In this way, the relationship between the variation of resonant frequencies and the change of piezoelectric cantilever structure, such as partial mass and stiffness, is revealed. The result shows that the combined effects of corresponding partial mass and stiffness on resonant frequencies of a piezoelectric cantilever are multivariant with the occurrence of freezing and accretion of ice. Then a substituted feedback measuring method based on the special structure of the bimorph piezoelectric cantilever is employed to obtain the resonant frequencies. The effectiveness of this measuring method is confirmed by comparing its results with those of the transmission measuring method and FEM. Finally, an appropriate operational mode is determined according to previous measured and calculated results, and the variation of the resonant frequency of the sensor throughout the icing process is summarized as well. The conclusions indicate that the employment of bimorph piezoelectric cantilevers on icing detection is feasible. It is simple in structure and measurement, yet it can effectively detect the existence of different icing conditions.

Key words: bimorph piezoelectric cantilever, icing detection, impedance measurement, resonant frequency, dynamic signal