Capacitive silicon micromachined gyro with mechanical coupling for sensitive signal reading 1

I. Preface

Silicon micro-mechanical sensors are sensors fabricated using semiconductor silicon processing techniques. Their compact size ensures broad application prospects. However, due to their small size, even minor absolute mechanical errors can lead to significant relative errors, causing motion interaction interference, i.e., mechanical coupling issues. The capacitive silicon micro-mechanical gyroscope is a sensor used to measure rotational angular velocity. According to mechanical principles, the rotation (angular velocity ωe) and translation (linear velocity vr) of a rigid body can generate an orthogonal acceleration (Coriolis acceleration, ac).  diode

Figure 1 Coriolis acceleration

When designing microgyro structures, the resonant frequencies of the drive axis and sensing axis are often made as close as possible to enhance sensitivity, thereby increasing the mechanical coupling sensitivity of the system. Due to manufacturing process defects, issues such as uneven microstructure mass, elastic imbalance of beams, and asymmetric damping arise. These factors amplify the vibration amplitude of the drive axis coupling to the sensing axis, i.e., the increase in mechanical coupling error, resulting in an offset output. This coupling is one of the key issues limiting the performance improvement of microgyros. Consequently, various microgyro structures have been proposed to mitigate mechanical coupling. However, the inherent structural characteristics of microgyros determine that mechanical coupling errors cannot be completely eliminated.

Currently, the solution from the circuit perspective involves assuming that the displacement in the sensitive direction is orthogonal to that in the driving direction, and extracting the sensitive signal using correlation detection methods. This essentially assumes an ideal state with no mechanical coupling, then mitigates the issue through fine circuit phase shifts and zero-point DC compensation.  diode