Stochastic analysis of a novel force sensor based on bifurcation of a micro-structure

In this paper, the stochastic dynamics of a novel sensing micro-mechanism is investigated. The structure of the micro-mechanism includes a micro-bridge and two equally spaced parallel electrodes on either side. The sensing scheme is based on the detection of the bifurcation of the equilibrium position of the micro-bridge as the axial force of the micro-bridge and the applied voltage to the electrodes change. An analytical model is developed that takes into account the mechanical and electrostatic domains nonlinearities. The behavior of the mechanism is investigated in time domain. The uncertainty in the operating condition, hence the dynamic behavior, of the micro-mechanism is studied using a statistic approach. Although, the dynamic model demonstrates significant deviation from the static model, the narrow statistical distribution of the sensor reading error indicates that the sensor can be easily calibrated for practical purposes. The advantage of this sensor is that it provides very high sensitivity, in the order of 2 mV / μ N , while eliminating the need for permanent oscillation and vacuum encapsulation of the sensing structure. These advantages lead to improved fatigue-life of the sensor as well as the power consumption. As the sensor transduces the force into a voltage reading, measurements can be performed accurately with relatively simple electronics. The result presented in this work provides improved estimation of parameters measured using this sensing micro-mechanism.