A ‘multiple modes’ – ‘multiple parameters’ sensing methodology part II – Experimental validation

This paper, the second of two companion papers, mainly reports experimental studies on ‘two modes’ internal resonance in coupled oscillators, including phenomenon observation of ‘two modes’ internal resonance, synchronous and successive sensing of ‘two traces’ with and without decoupling, as well as physical definition and experimental calibration of ‘two modes’ related sensitivities for ‘two traces’. Coupled oscillators comprise a sensing cantilever (SC), a detecting cantilever (DC) and a coupling overhang, desirable for high sensitivity with separation of sensing and detecting. In order to observe the occurrence of ‘two modes’ internal resonance, frequency ratios of SC to DC in the first two flexural modes need to simultaneously satisfy 1:3 via geometrical design and material selection. An experimental platform is constructed to observe and study ‘two modes’ internal resonance under different frequency excitations. ‘Two modes’ sensing by jump-down frequency shifts in two flexural modes of DC, is conducted with decoupling but without limitation of position, to characterize ‘two traces’ applied onto SC; while that is conducted without decoupling but with a distinctive position to eliminate mutual coupling between ‘two traces’. An inclination of the tangent plane for any point on ‘sensing surface’, formed by ‘two modes’ frequencies and one of two traces, is physically defined as the sensitivity. In this work however, 0.10305 Hz/mg and 0.06246 Hz/mg are thus experimentally calibrated for ‘two traces’ respectively in the case of with decoupling; while 0.76227 Hz/mg and 0.08466 Hz/mg are experimentally calibrated in the case of without decoupling. A theoretical modelling of the proposed ‘Multiple Modes’ –‘Multiple Parameters’ sensing methodology is discussed in Part I, the first of the two companion papers.