Nonlinear dynamics of a tunable novel accelerometer, tunable with a microtriple electrode variable capacitor

In this paper, a dynamic analysis of a tunable novel triple-electrode variable capacitor is presented. It is subjected to a base excitation that can act as an accelerometer with a wide measurement range. A clamped–clamped porous microbeam connected to a frame and a proof mass in the middle of it form the structure. The sensing section of the accelerometer is in the form of capacitive sensing combs in which the fixed fingers connected to the frame are subjected to a biasing DC voltage (\({V}_{\mathrm{S}}\)). In the tuning section of the accelerometer, two fixed fingers (electrodes) connected to the frame are subjected to a DC tuning voltage (\({V}_{\mathrm{T}}\)), and two moving free electrical charge fingers connected to the beam act as a sliding connector. A DC tuning voltage applied to the fixed electrodes generates an electrostatic force that works as a tunable voltage-sliding nonlinear spring in the structure. Coupled nonlinear differential equations of the transversal and longitudinal vibration of the structure in the presence of the base excitation are extracted. The steady-state solution of the accelerometer is obtained based on a physically based learning method that makes it possible to obtain its frequency response for the first harmony as well as for the higher harmonies and to predict primary and secondary resonances in different harmonies of the response. The transient response of the accelerometer in exposure to various types of external acceleration fields such as step, single pulse, and repetitive pulse is investigated. The frequency response of the accelerometer for different values of tuning voltage is studied. It is shown that the tuning stiffness of this voltage-sliding spring provides a highly effective solution to realize instrumentation with wide-range measurement. The presented tunability can enable the structure to act as an effective accelerometer, microresonator, energy harvester, and so on.