Under certain initial conditions and a certain external moment, the gyro will rotate continuously around another fixed rotating shaft while continuing to rotate. This is the precession of the gyro, also known as the gyro. Effect (gyroscopic effect).
There are many types of gyroscopes, which can be divided into sensing gyroscopes and indicating gyroscopes according to their use. Sensing gyroscopes are used in automatic control systems for flight body motion as horizontal, vertical, pitch, heading and angular velocity sensors. Indicates that the gyroscope is primarily used for flight status indications and is used as a driving and pilot instrument.
We are now in contact with electronic gyroscopes, piezoelectric gyroscopes, micromachined gyroscopes, fiber optic gyroscopes, laser gyroscopes, etc., and can also be used with accelerometers, magnetoresistive chips, GPS, for inertial navigation. Control System.
Basic technical principle of MEMS gyroscope
In order to apply gyroscope technology to small devices such as mobile phones, MIDs, controllers, mice, and digital cameras, it is inevitable to miniaturize traditional gyroscopes. For this reason, MEMS gyroscopes are fully integrated into digital devices and game devices. What is MEMS? MEMS (Micro ElectroMechanical systems) is a cutting-edge technology based on micro/nano technology, which is a technology that can design, process, manufacture, measure and control micro/nano materials. It integrates mechanical components, optical systems, drive components, and electronic control systems into a single unit micro system.
MEMS products have been widely used. . . Digital camera (anti-shake and anti-vibration device, using MEMS gyroscope products to accurately perform zero-return action even in a continuous vibration environment), laptop or MID, mobile phone (such as accelerometer), MP3/MP4, game console In consumer electronics. Gyroscopes use this technique to form micron-scale precision resonant structures on silicon wafers that sense the magnitude and direction of angular velocity.
Compared to traditional gyroscopes that use the principle of conservation of angular momentum, MEMS gyroscopes use different operating principles. A conventional gyroscope is an object that rotates continuously, and the direction of its rotation axis does not change with the rotation of the holder that carries it. It is obviously more difficult to machine such a non-stop rotatable object that is continuously rotated on a silicon wafer substrate by micromechanical techniques. To this end, the MEMS gyroscope uses Coriolis force to realize the miniaturization of the device based on the characteristics of the conventional gyroscope. What is Coriolis force? The Coriolis force is also often referred to as the Coriolis force, the Coriolis force, which is the displacement of the mass point of the linear motion in the rotating system due to the linear motion of the inertia relative to the rotating system. The description comes from the inertia of the motion of the object. The biasing force acting on the moving mass of the earth due to the rotation of the earth is such a representative. The geostrophic force helps to explain some geographical phenomena, such as the side of the river The other side is washed even more.
The MEMS gyroscope is the most common application of Coriolis force. The MEMS gyroscope utilizes the Coriolis force (the tangential force that the rotating object receives when moving in the radial direction). The gyroscope in rotation can be used for various forms. The linear motion produces a reflection, and the motion measurement and control can be performed by recording the Coriolis force received by the gyroscope component. In order to generate this force, MEMS gyroscopes are usually equipped with movable capacitor plates in two directions. "The radial capacitive plates plus the oscillating voltage force the object to move radially, and the lateral capacitive plates are measured due to the lateral Coriolis motion band. The change in capacitance comes." Thus, the "gyro object" in the MEMS gyroscope will continue to make radial movements or oscillations while driving, thus simulating the movement of the Coriolis force constantly changing back and forth in the lateral direction. And can make a slight shock in the lateral direction with a driving force difference of 90 °. This Coriolis force is like the angular velocity, so the angular velocity of the MEMS gyroscope can be calculated from the change in capacitance.
Triaxial angular velocity is proportional to the rate of rotation
Taking STMicroelectronics' MEMS gyroscope as an example, its core component is a micromachining mechanical unit that is designed to operate according to a tuning fork mechanism (the tuning fork mechanism works by a pair of piezoelectric crystals mounted on the tuning fork base). The tuning fork vibrates at a certain resonant frequency. When the tuning fork of the tuning fork switch comes into contact with the measured medium, the frequency and amplitude of the tuning fork will change. These changes of the tuning fork switch are detected by the intelligent circuit, processed and converted into a switching signal. ). The motor drive part is electrostatically driven to oscillate the mechanical element back and forth to generate resonance. The Coriolis force is used to convert the angular rate into a displacement of a specific induction structure, and the two moving mass points are continuously moved in opposite directions. As long as an angular rate is applied from the outside, a force occurs, the direction of the force being perpendicular to the direction of motion of the particle. The generated force causes the sensing mass to be displaced. The magnitude of the displacement is proportional to the magnitude of the applied acceleration. The sensor located next to it senses the change in capacitance caused between the stator and the rotor, thereby achieving the steering function. Moreover, since the advanced power-off function is embedded in the control circuit, the total power consumption of the gyroscope can be greatly reduced by turning off the entire sensor when the sensor function is not required, or allowing it to enter the deep sleep mode. Thus, portable devices such as mobile phones can achieve longer battery life.
MEMS gyroscope technology development direction
Driven by Apple's iPhone and Nintendo's Wii game console, the concept of "sports sensing" is deeply rooted in people's minds. MEMS gyroscopes with miniaturized and intelligent features are becoming the focus of users and are becoming the focus of consumer electronic devices. The key device for sensing. Yole Development, a leading market research consultancy, recently predicted that sales of MEMS gyroscopes, accelerometers and magnetic sensors will reach $4.5 billion in 2013.
Advanced technology is the basis for ensuring that MEMS gyroscope technology can be brought to reality. In addition to using a large number of traditional IC processes, MEMS processing requires special processes such as double-sided etching and double-sided lithography. By integrating MEMS wafers and corresponding CMOS electronic circuits at the wafer stage, the current product has been able to reduce the package size of MEMS gyroscopes to mm, with a maximum thickness of only about 1mm, while providing higher performance. Lower noise, with lower semiconductor package cost. The new generation of MEMS gyroscopes has many advantages such as small size, low power consumption, high precision and low cost.
The three-axis MEMS gyroscope combines a so-called six-axis product with a three-axis MEMS accelerometer. The three-axis gyroscope can simultaneously measure the position, movement trajectory and acceleration in six directions.
From the application direction of MEMS gyroscopes, the gyroscope can measure the angular velocity along one axis or several axes, which can complement the advantages of MEMS accelerometers (accelerometers). If you combine the two sensors of accelerometer and gyroscope Designers can better track and capture the full motion of 3D space, providing end users with a more realistic user experience, precise navigation system and other features.
To this end, experts at InvenSense (Yingmeisheng), a leading manufacturer of this technology, believe that “to accurately describe linear and rotational motion, designers need to use both gyroscopes and accelerometers. Solutions using gyroscopes are available. For high-speed and fast-reaction rotation detection; the simple use of accelerometers can be used for applications with a fixed gravity reference coordinate system, linear or tilting motion, but rotational motion is limited to a certain range. Gyro and accelerometer solutions are required for and rotary motion."
In addition, in order to make the gyroscope designed and manufactured with high acceleration and low mechanical noise, or to correct the rotation error of the accelerometer, some manufacturers use a magnetometer to perform the sensing function traditionally implemented by the gyroscope. In order to complete the corresponding positioning, the gyroscope industry has specialized. This suggests that a hybrid gyroscope, accelerometer or magnetic sensor combination is becoming a trend in MEMS gyroscope technology applications.
InvenSense's marketing director, Doug Vargha, also said: "If you only use traditional accelerometers, users get either an agile but noisy output, or a slow but pure output, such as an accelerometer. Combined with a gyroscope, you get an output that is both pure and responsive."
Postscript, MEMS gyroscopes are promising
Jidesh Veeramachaneni, a technology consultant for HTC, a smartphone manufacturer, said: "MEMS gyro technology has become the most discussed topic among smartphone developers. It is expected that this technology will become the standard for smartphones next year, and users can get it through gyroscopes. Many new experiences, such as games, you can play fencing games more easily with your mobile phone. For this reason, vendors including ST, InvenSense, Kionix, Bosch Sensortec, ADI, Freescale, etc. have all invested in this market, with a view to Gaining more say in future competitions indicates that the future MEMS gyroscope market will become more exciting, the competition in the MEMS industry will heat up, and the cost of three-axis gyroscopes will fall below $1. Of course, in addition to the breakthrough application in hardware configuration, it is also crucial for the relevant game or program developer to develop a program that fully reflects the application of this feature. This will directly determine the product that comes standard with this feature on the market. The popularity.
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