Design and Implementation of a Tunable, Duffing-Like Electronic Resonator via Nonlinear Feedback

To date, many vibration-based sensing modalities have relied upon monitoring small shifts in the natural frequency of a system to detect structural changes (e.g., in mass or stiffness), which are attributable to the chemical or biological species, or other phenomena, that are being measured. Often, this approach carries significant signal processing expense due to the presence of electronics, such as precision phase-locked loops, when high sensitivities are required. Bifurcation-based sensing modalities, in contrast, can produce large easy to detect changes in response amplitude with high sensitivity to structural change if applied appropriately. This paper demonstrates the design and implementation of a tunable, Duffing-like electronic resonator realized via nonlinear feedback electronics, which uses a quartz crystal tuning fork as the device platform. The system in this manifestation uses collocated sensing and actuation, along with readily available electronic components, to realize the desired behavior. The sensitivity of the device is tunable via the control of feedback gain and the type of Duffing-like response (hardening or softening) is also selectable, thus creating a versatile bifurcation-based sensing platform. [2015-0014]