MEMS gyroscope and MEMS technology are new technologies that are developing rapidly in the 21st century. MEMS gyroscopes abandon the problems of traditional mechanical gyroscopes such as large size and weight. On this basis, they use micron and nanometer processing technology to develop new equipment that is smaller, has lower power consumption, is more conducive to mass production, and has excellent performance. This article aims to introduce the relevant knowledge of MEMS gyroscopes. The following will explain the working principle, characteristics, applications and future development of MEMS gyroscopes.

How MEMS gyroscopes work
MEMS gyroscope measures angular rate based on the Coriolis effect. When an object with an initial angular velocity moves straight in a rotating coordinate system, its movement trajectory is a straight line, but in an inertial coordinate system, its movement trajectory will deviate to a certain extent. The reason why the motion trajectory changes during motion is because it is interfered by external force. This force is the Coriolis force. The Coriolis force is caused by the inertia of an object in straight motion, perpendicular to the direction of motion of the object. Figure 1 illustrates the Coriolis effect.

Figure 1 Principle of Coriolis effect

As shown in the figure above, if the object m is moving uniformly along the X-axis with a velocity of v, and rotates itself around the Z-axis with an angular rate of Ωz, then the Coriolis force on m is (Figure 2) :

Figure 2 Coriolis force formula

The displacement change of MEMS gyroscope under Coriolis force can be obtained by capacitive induction. The MEMS gyro contains a vibrating block and a flexible spring. The essential condition of Coriolis force is the rotation of the MEMS gyro around the Z axis and the vibration of the vibrating block. When the MEMS gyro moves, the capacitance detection sensor on the vibration block will produce energy transfer, causing changes in the electrochemical quantity, so as to convert the angular velocity of the gyroscope to the capacitance change for detection.

Characteristics of MEMS gyro
Compared with traditional gyroscopes and fiber optic gyroscopes, MEMS gyroscope has unique advantages and characteristics:

1. The quality, volume and energy consumption are small

2. The cost is low, which is suitable for mass production

3. It has large dynamic range, high stability and high reliability.

4. It can be used in harsh mechanical environment;

5. Short preparation time for fast response weapons;

6. Medium and low precision, suitable for short time application or combination with other information systems.

Application of MEMS gyroscopes
MEMS gyroscope is widely used, according to the field classification, MEMS gyros can be applied to oil logging, aerospace, UAV, mining, mapping and other fields. According to the accuracy level classification, MEMS gyroscopes can be divided into navigation, tactical and consumer levels according to the accuracy level from high to low. The navigation level and the tactical level are generally used in areas that require high precision, while the consumer level is more close to life, such as smartphones, cars, and so on. Ericco’s navigation-grade MEMS gyros can independently realize the four functions of inertial navigation: orientation, positioning, attitude measurement and navigation. While the tactical gyroscope needs to be used with the directional positioning system to achieve more powerful functions.

1. Oil drilling
MEMS gyro is mainly used in the field of north finding in logging tools/gyroscope tools, pointing and steering in drilling equipment. In the drilling process, the drill goes deep into the ground, and the equipment operator cannot understand the real-time position and direction of the drill depth on the ground, then the MEMS gyro is needed to help to achieve the accuracy of the work.

2. Aerospace, drones
MEMS gyro can be used in the initial alignment of UAV launch systems, accurate attitude and bearing maintenance in navigational IMU/INS/AHRS, positioning, navigation, and positioning and attitude control of large UAVS, AUVs, etc.

3. Mining
MEMS gyro can be applied to the pointing and steering of advanced mining equipment. Because the working environment in the mining field is mostly in the harsh environment such as underground, the gyroscope that relies on satellite positioning can not work stably, which is the need for MEMS gyro that will not be interfered with the signal to complete the work.

4. Surveying
MEMS gyroscope can be applied to orientation, positioning and navigation of ground, sea and air mapping systems.

5. Inertial platform
Inertial stabilization platform can maintain the dynamic attitude datum because it can isolate the motion disturbance of the missile (missile, plane, chariot and ship) and adjust the attitude and position of the platform continuously.

6. Attitude balance
Because the gyroscope in the working state, maintain an absolute attitude, so you can indicate the aircraft flying posture, in order to ensure the pilot to master and control the flight attitude of the aircraft, to ensure that the aircraft safe, normal flight.

7. Electronic equipment
The main application in this field is consumer grade MEMS gyroscope. Gyroscope used in digital camera, digital camera, can achieve anti shake function, is to take photos, video more clear, true. It’s also used for mobile phone positioning and mobile game manipulation.

Development trend of MEMS gyroscope
1. The volume is smaller and smaller, the accuracy is higher and higher. The precision of gyro has been catching up with the higher precision of gyroscopes such as fiber optic gyro, and its accuracy has been comparable to it.

2. Process and packaging technology matures. Through the technological development and continuous research in recent years, many new packaging technologies have emerged, such as vacuum wafer-level packaging, making the yield of MEMS gyro more and more high.

3. Engineering applications continue to expand, more and more successful cases. Now MEMS gyro can not only be applied to the fields mentioned above, but also can be applied to some new fields, such as medical treatment, agricultural intelligence and so on.

Conclusion
This paper analyzes the working principle, characteristics, application fields and future development trends of MEMS gyros, hoping that you can have an understanding of this emerging technology.

Ericco mainly develops navigational and tactical MEMS gyroscope for the market, and the performance is very excellent. For example, the navigation-grade ER-MG2-300/400, a gyroscope designed for air navigation, has bias instability of 0.03-0.05° deg/hr and the measurement range up to ±400°/s. Tactic-grade MEMS gyro has a wider range of applications, its accuracy is slightly lower than the navigation level but the performance is still excellent, suitable for industries that need to control budgets. For example, the bias instability of the tactical grade ER-MG2-067 <0.3°/hr.

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MEMS Gyroscope