Mechanical properties of MEMS gyroscope sensitive structures

From the theoretical description of the Coriolis effect in the previous section, the magnitude of the angular rate can be obtained by measuring the magnitude of the Coriolis acceleration of a moving object. As a kind of angular rate sensor, gyro usually generates Coriolis acceleration by detecting the rotation, vibration or surge of mass. Most MEMS gyros are vibrating angular rate gyros, whose main mechanical component is a two-degree-of-freedom vibrating structure. The vibration structure can vibrate in two directions in the same plane. Considering the difficulty of micromachining, MEMS gyroscope adopts simple planar rigid mass structure. MEMS vibrating gyro can be divided into two types: linear vibrating gyro and angular vibrating gyro according to the different modes of vibration mass movement. This paper mainly discusses linear vibrating gyro, but most of the conclusions given in this paper can also be applied to angular vibrating gyro. In general, the main components of MEMS line vibration gyro include: a detection mass block supported by an elastic support beam, an electrostatic drive module and a detection module. Among them, the electrostatic driving module is used to drive the detection mass block to vibrate, and the detection module is used to detect the displacement or speed of the mass block. According to the different detection mechanism, the detection module can be divided into capacitive, piezoelectric, piezoresistive and optical types. The mechanical structure of MEMS gyroscope can be equivalent to a two-degree-of-freedom mass-spring-damping system model.

The detection mass block in the gyro can move in the XOY plane. Because it is driven by the electrostatic driving module, it vibrates along the X axis, so the direction along the X axis is the driving direction, and the vibration mode along the X axis is the driving mode. The overall structure is affected by the angular rate around the Z axis, so that the mass block vibrates along the Y axis and generates Coriolis force. Then the Y axis direction is the detection direction, and the vibration mode along the Y axis is the detection mode.

Conclusion

This paper introduces the Coriolis force and sensitive structural mechanical properties of MEMS gyro. MEMS is a new type of technology, with the continuous optimization of its own structure calibration in recent years, constantly improve the level of accuracy, and continue to get involved in a wider range of applications, MEMS gyroscopes have been enough to compete with other types of gyroscopes. MEMS gyro is not only active in the consumer field, it has gone deep into the high-precision field such as the tactical level and navigation level. In order to develop and produce MEMS gyroscopes with excellent performance, Ericco uses advanced equipment to test and calibrate MEMS gyroscopes, mainly for tactical and navigation level fields. For example, the excellent ER-MG2-50/100 is a navigation-grade north finding MEMS gyroscope developed specifically for ground navigation, while the ER-MG2-300/400 is a navigational MEMS gyroscope developed specifically for air and sea navigation. There are also tactical gyroscopes ER-MG-067 and ER-MG-068, which are slightly less accurate than the navigation level, but still have excellent performance.

Basic dynamics analysis of MEMS gyroscope