Measurement of Tidal Tilt by a Micromechanical Inertial Sensor Employing Quasi-Zero- Stiffness Mechanism

High-precision microelectromechanical inertial sensors based on spring-mass structures are of great interests for a wide range of applications, including inertial navigation, disaster warning and resource exploration. Lowering the resonant frequency is essential to further improve the sensitivity of the sensors. However, conventional approaches are facing insurmountable difficulties from size reduction to machining precision. This paper proposed a novel quasi-zero-stiffness mechanism that is compatible with MEMS technologies together with a micromaching approach for adjusting the stiffness precisely. By improving the compliance of a typical spring with a negative-stiffness compensation mechanism induced by axial force, the resonant frequency of the micro spring-mass structure is lowered to 0.7 Hz, which is at least 3 times lower than current state-of-the-art micro structures. Based on this ultra-sensitive micro structure base on the quasi-zero-stiffness mechanism, the micro inertial sensor, with a chip size of a postage stamp, has shown a low self-noise of 0.6 nrad/ $\surd $ Hz at 0.04 Hz and a high long-term stability that are comparable to traditional pendulum inertial sensors. It is the first micro device, to our knowledge, that can successfully measure the tidal tilt signal. [2020-0048]