MEMS gyroscope has gradually come to the fore in recent years to meet the needs of many industries, and MEMS technology is also constantly advancing to meet market needs. So why can MEMS gyroscope, as an emerging technology, beat other types of gyroscopes and become so popular? This article will introduce the history of gyroscope technology development and different types of gyroscopes.
In physics, gyroscopes are used to measure angular velocity because of their fixed-axis and precessive properties. According to Newton's first law, when an object is not acted upon by an external force, it has the property of maintaining its original state of motion. When the gyroscope rotates at high speed, without being affected by external forces, according to the principle of conservation of angular momentum, the magnitude and direction of the angular velocity of the gyroscope remain unchanged. This is the fixed axis of the gyroscope. According to Newton's second law, when an external torque is applied to a gyroscope, the torque on the object is proportional to the time rate of change of angular momentum, and the direction points to the direction of the combined external moment. The momentum moment vector of the gyro will catch up with the external moment at the minimum speed. Therefore, the gyro will move in the direction of the external moment along the axis where the angular momentum is located, thereby generating a gyro precession angular velocity. The direction can be based on the right-hand screw rule. This is the precession of the gyro.
Based on the above principles, an angular rate measuring instrument was designed, namely a gyroscope. Herman Anshutz and Elmer Sperry designed the world's first mechanical gyroscope in 1904, which enabled precise measurement of angular velocity and was later used in various industrial scenarios. With the development of electronic science, optics, etc., gyroscope technology has also changed. In the past hundred years, gyroscope technology has experienced several major development stages: traditional rotor gyroscope, optical gyroscope and resonant gyroscope, and these various Such gyroscopes are also used in a variety of application fields, such as oil logging, aerospace, mining, surveying and mapping, unmanned driving, etc., as well as some consumer fields such as smartphones, VR equipment, etc. Let's introduce these types of gyroscopes.
1. Traditional rotor gyroscope
This is the earliest gyroscope, which uses the fixed axis and precession characteristics of a high-speed rotating gyroscope to measure the angular velocity of the carrier. During use, the high-speed rotating rotor is fixed inside the frame so that it has a degree of rotational freedom. Figure 1 shows the structure of a traditional rotor gyroscope. This type of gyroscope is susceptible to interference from external vibration signals, and friction is easily generated between the rotor and the support. Therefore, the support system is a very important part of the rotor gyroscope, which directly determines the accuracy of the gyroscope.
According to different support systems, traditional rotor gyroscopes can be divided into: ball bearing supported gyroscopes, air-floating gyroscopes, liquid-floating gyroscopes, dynamically tuned gyroscopes and electrostatic gyroscopes.
Figure 1 The structure of traditional rotor gyroscope
2. Optical gyroscope
The theoretical basis of optical gyroscopes is the Sagnac effect, which was proposed by French scientist Sagnac in the early 20th century. Figure 2 shows the schematic diagram of the Sagnac effect. This effect means that for a simple ideal circular light path, when the light path does not rotate relative to the inertial space, two beams of light traveling in opposite directions are injected at a point. The two beams of light have the same optical path length after propagating for one week and can return to the injection point at the same time. When the optical loop rotates clockwise, the injection point of the light source will also rotate accordingly. When the light wave propagating in the counterclockwise direction propagates along the closed optical path for one cycle and then returns to the light wave injection point, the actual optical path traveled is less than 2πR. When light propagates in one direction and returns to the origin after one revolution, the optical path it takes is greater than 2πR. The optical path difference produces a time difference, which in turn produces a phase difference. Since the two beams of light have the same frequency and a constant phase difference, interference will occur when the two beams of light meet. When there is an angular velocity of rotation in the loop plane, the interference fringes on the screen will move. This is the Sagnac effect.
Optical gyroscopes are divided into laser gyroscopes and fiber optic gyroscopes, and their basic principles are the Sagnac effect.
Figure 2 Principle diagram of Sagnac effect
3. Vibrating gyroscope
Vibrating gyroscopes are divided into hemispheric resonant gyroscope and MEMS gyroscope.
The full name of MEMS is microelectromechanical system. The basic principle of MEMS gyroscope is the Coriolis effect, which refers to an inertial force that an object in a rotating reference system receives when it moves. An object moving in a rotating coordinate system will deflect. The phenomenon of shift, the generation of Coriolis force leads to the occurrence of this shift. When a mass element vibrates sinusoidally in a plane, if the plane rotates at an angular velocity at the same time, under the action of the Coriolis effect, the mass element will make a sinusoidal motion perpendicular to the plane (resonance axis), and the direction is consistent with the right hand Screw rule, amplitude is proportional to angular velocity. Figure 3 illustrates the Coriolis force effect.
MEMS gyroscope is a vibrating gyroscope that uses the Coriolis force to convert the rotation of the gyroscope into a sinusoidal vibration perpendicular to the plane. The input angular rate is obtained by measuring the displacement of the axis. Different types of MEMS gyroscopes detect Coriolis force in different ways.
MEMS technology was born in the 21st century and has developed rapidly in recent years. It has caused gyroscopes to undergo miniaturization changes, making the size of gyroscopes become smaller and smaller. At the same time, its accuracy is also constantly improving, meeting the needs of more and more fields.
MEMS gyroscopes are mainly divided into navigation grade, tactical grade and consumer grade according to their accuracy and application. Consumer-grade MEMS gyros generally have low accuracy and are used in popular fields, such as smartphones, VR, cameras, etc. Ericco is mainly developed for the navigation level and tactical level. The accuracy of the tactical level is lower than that of the navigation level. It needs to be used with the GNSS system to achieve the four major functions of orientation, positioning, attitude measurement and navigation. The navigation-grade MEMS gyroscope itself has these four functions and does not need to be anyone's assistant. For example, ER-MG2-50/100 is a MEMS gyroscope that can north seeking. It can be used in oil logging, mining and other ground navigation fields, while ER-MG2-300/400 is used in air and maritime navigation. Used in aeronautical and maritime surveying and mapping fields, etc.
At the same time, MEMS gyroscopes have advantages that other gyroscopes do not have:
Small size and light weight
Low power consumption
Easy to mass produce
Low cost
Wide range of applications
Good reliability
Can adapt to harsh high temperature environment
Figure 3 Coriolis force effect
To sum up, gyroscope technology has gone through different stages of development and become increasingly mature. In order to meet the needs of the market, high-precision, high-reliability and low-cost gyroscopes have become the main demand. It is true that the accuracy of MEMS gyroscope has not been comparable to other types of gyroscopes in the past, but technology is advancing every day, and the gap between their accuracy is getting smaller and smaller. Due to the unique advantages of MEMS gyros and increasing accuracy levels, more and more industries are turning to MEMS gyros with higher cost performance, which is why MEMS gyroscopes can stand out.
I hope that through this article you can learn something about MEMS gyroscopes and other types of gyroscopes. If you are interested in other contents of MEMS gyroscopes, please click on the relevant articles and related products below to learn.
More Technical Questions
1.How to select MEMS gyroscope?
2.How does MEMS gyroscope work in harsh high temperature environment?
3.What’s the north-seeking principle of MEMS gyroscope?
4.The materials and structure of MEMS gyroscope
5.What’s the advantages and disadvantages of MEMS gyroscope?
6.MEMS gyroscope VS FOG: What’s the difference between them?
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