Capacitive silicon micromachined gyro with mechanical coupling for sensitive signal reading 2

For micro gyroscopes, the task of the correlation detector with analog circuits such as multipliers and low-pass filters as the core is to accurately separate very small Coriolis acceleration sensitive information from large background interference signals. Usually, the amplitude of background interference signals is much larger than the range of sensitive signals. Due to the non absolute linearity of analog circuits, both interference signals and sensitive signals suffer from issues such as harmonics and asymmetric positive and negative half waves. Therefore, correlation detection based on multipliers and low-pass filters has poor practical performance and instability.

This article intends to propose a sensitive signal reading method based on the mechanical coupling analysis already proposed in the literature: sampling at the zero crossing point of coupling interference.  diode

2、 Mechanical coupling analysis

We analyze using a linear vibration micro mechanical gyroscope model. For idealized (non mechanically coupled) micro mechanical gyroscopes, theoretical analysis shows that when measuring a single degree of freedom

Due to the presence of φ 1, x (t) and y1 (t) are not completely orthogonal, and the frequency sensitivity coefficient is related to the inconsistency of gyroscope processing. If it is assumed that the sensitive signal voltage is proportional to the displacement in the sensitive direction, and there is interference from the driving voltage mixed in the sensitive voltage output, without considering the phase shift of the circuit, the signal output before the relevant detector is

Among them, A and B are coefficients, and B is the interference coefficient;

The phase angle difference between the driving voltage and the displacement in the driving direction.

In fact, the B value is relatively large, and even under ideal conditions without mechanical coupling, useful sensitive signals and electrical interference are not completely orthogonal. The phase adjustment of the reference voltage for the relevant detector must first ensure the removal of electrical interference.diode