A comprehensive modeling of a 6-axis single proof mass MEMS-based piezoelectric IMU

This work reports a comprehensive multiphysics modeling and optimization of a MEMS-based piezoelectric inertial measurement unit (IMU) sensor using a single proof mass. The studied miniaturized sensor consists of a stick-shaped cylindrical proof mass with two concentric rings connected between them with joints where the stress is concentrated. The advantage of introducing this new piezoelectric IMU concept is the concurrent detection of all six degrees of freedom (DOFs), i.e., 3-axis linear accelerations and angular velocities, using a single seismic mass and only four electrodes. The piezoelectric IMU structure optimization was carried out using finite element analysis (FEA) in order to obtain the optimal dimensions and generate the maximum stress in the piezoelectric layer. In fact, the mechanical (displacement and stress) and electrical (potential and sensitivity) performance of the IMU structure was determined when 3-axis linear accelerations and 3-axis angular velocities were applied. The simulation results showed a sensitivity of 1 mV/g and 6.8 mV/g, respectively, for linear accelerations along the x-/y- and z-axes. Along these same axes, the angular velocity sensitivity was approximately 0.39 µV/rad/s and 1.7 mV/rad/s. Moreover, the simulation results claim that the proposed IMU has good performance in terms of cross-axis sensitivity of less than 0.88% for all six DOFs, which is due to its perfectly symmetric circular structure. Finally, a simple block diagram is presented to separate the outputs related to linear acceleration from those related to angular velocity from the four sensing electrodes.