Study On Internal Resonance Based Mass Sensing Mechanism With Coupled Cantilevers

For the real-time monitoring of toxic,harmful,flammable,explosive and other substances,the single-substance resonant detection technology is relatively mature,while the multi-substance resonant detection technology is still in its initial stage,and the sensing mechanism and methods still have limited-sensitivity,multi-output,difficult to miniaturize and other problems,it is urgent to explore a high-sensitivity,wide-range,single-output multi-substance detection mechanism.In this paper,a resonant two-substance sensor with coupled cantilevers structure as the core is designed,and a new high-sensitivity detection method of two-substances based on multi-order modal nonlinear internal resonance is proposed.Theoretical Section: the theoretical expression of two-substance synchronous detection mechanism based on the first and second bending modes of the cantilever beam is derived,and the influence of the mass disturbance position on the frequency of the first and second bending modes of the cantilever is analyzed.Lumped parameters model of the Coupled cantilever structure is established,and multi-scale method is used to derive and solve the two degree of freedom coupling motion equation.Combined with the numerical iterative algorithm,the numerical simulation in MATLAB software was carried out,and the influence of system parameters on nonlinear resonance response is analyzed.A sensitivity triple magnification scheme for mass detection based on nonlinear internal resonance is proposed.Simulation Section: A three-dimensional finite element model of the coupled cantilever structure was established,and the effects of the overall thickness,the length and width of the high-frequency detection cantilever,and the length and width of the coupled element on the natural frequencies of the four main working modes of the coupled cantilever structure were simulated and analyzed,and the geometric parameters of the coupled cantilevers structure are preliminarily determined.The influence of the adsorption layer position on the first-order and second-order bending modal frequencies of the low-frequency sensing cantilever was simulated and analyzed,and the optimal position of the adsorption layer was determined.The theoretical analysis of the simultaneous detection mechanism of the two substances was preliminarily verified.Experimental Section: The coupled cantilevers structure samples,fixtures were fabricated and an experimental verification platform was built.First,for the single-cantilever two-substance detection,the two-substance detection mechanism based on multi-order mode shapes is preliminarily verified.Next,for the high-sensitivity single-substance detection,the mass detection sensitivity triple magnification scheme based on nonlinear internal resonance is preliminarily verified.Finally,mass perturbations are simultaneously applied at two adsorption positions A and B on the low-frequency sensing cantilever,first-order and second-order nonlinear internal resonance response output of high frequency detection beam were detected,the sensing characteristics of coupled cantilevers structure for high-sensitivity two-substance detection are analyzed.The experimental results show that when the position of the specific adsorption layer is fixed,simultaneous detection of the two substances can be achieved by measuring the first and second bending modes frequencies of the sensing cantilever in the coupled cantilevers structure,and the detection sensitivity can be tripled by using the first and second nonlinear internal resonance of the coupled cantilevers structure.Optimization Section: A permanent magnet-permanent magnet magnetic force tuning/compensation mechanism is initially designed.On the one hand,it can perform frequency tuning to meet the internal resonance conditions;on the other hand,it can perform frequency compensation to improve the sensor range and life.The finite element simulation method is used to preliminarily explore the influence of the coupling element’s size parameters on the support loss of the coupled cantilevers structure,and it is proposed that the reasonable setting of the length of the coupling element can effectively reduce the support loss.