The important role of the inertial measurement unit IMU in autonomous driving and navigation is introduced. It is also known that the important component of the IMU is the gyroscope, then what is the gyroscope? What? Next, let's take a look at the basics of the gyroscope.
Another name for gyroscopes is also called angular velocity sensor. By definition, gyroscope is a sensor that measures carrier angular motion or angular velocity from the perspective of application. Look, gyroscopes are often used in navigation, positioning and other systems commonly used examples such as mobile phone GPS positioning navigation, satellite three-axis gyroscope positioning, the accuracy of its gyroscope plays a vital role in the whole process, that is, high-precision gyroscope It directly determines the accuracy of the inertial navigation system and the performance quality of the guidance and automatic control system.
As early as the 17th century, in the age of Newton's life, the mechanics of high-speed rotating rigid bodies has been studied intensively, laying a mechanical frame gyroscope The theoretical basis.In 1852, the French physicist Fu Ke made the earliest Foucault gyro in order to verify the rotation of the Earth, and formally proposed the term “gyro”. However, due to the low level of manufacturing process at that time, the gyroscope had a large error and could not observe and verify the rotation of the earth.
By the end of the 19th century and the beginning of the 20th century, the invention of electric motors and ball bearings provided powerful material conditions for the manufacture of high-performance gyroscopes. At the same time, the development of the navigation industry has pushed the gyroscope into a practical stage. In the early 20th century, when the maritime industry flourished, the German explorer Anthus wanted to take a submarine to explore the North Pole. In 1904, he created the world's first nautical gyro compass, which opened up the gyroscope to indicate the position on the moving object. the way. At the same time, the German scientist Schuler created the “Schuler Tuning Theory”, which became the theoretical basis of the gyrocompass and navigation instruments.
China is one of the earliest countries in the world's civilized development. In terms of gyro technology, China also has many inventions and creations.For example, the fast-rotating reel program performed in traditional acrobatic art utilizes the stability of a rigid body that rotates at a high speed. In the application of the gimbal that supports the high-speed rotating rigid body, in the late Western Han Dynasty, some people created the same principle as the current gimbal, "the scented incense burner". This kind of incense burner can “circle around and the furnace body is always flat and can be placed in the middle of the body”. In fact, the incense burner is placed in a hollow ball, and it is framed by two rings. The vertical axis and the quality of the incense burner itself are used. When the ball is arbitrarily rolled, the incense burner is always stable without tilting. sprinkle.
With the development of aviation, in the 1930s, aeronautical pneumatic gyroscopes, direction meters and turning instruments have been manufactured. At the end of the Second World War, gyroscopes were used as sensitive components in missile guidance systems. Especially since the 1960s, with the development of science and technology, in order to meet the new requirements of modern aviation, navigation, especially space navigation, various new types of gyroscopes have appeared. Currently,Gyros are moving toward ultra-high precision, long life, small size and low cost.
So, what exactly is a gyroscope? The traditional gyroscope is defined as: a symmetrically balanced high-speed rotating rigid body (referring to an object that is not deformed by external force), supported by a special suspension device, so that the rotating rigid body can not coincide with the axis of rotation (or not parallel) Another special device that rotates the shaft (or two). Among them, the symmetry axis of the gyroscope is also the rotation axis, which is called the gyro spindle. The theory to study the gyroscopic motion characteristics of this kind is the dynamic theory of the rigid body around the fixed point motion in dynamics.
The definition of a traditional gyroscope includes a large class of gyroscopes, called mechanical rotor gyroscopes.For example, frame gyroscopes, liquid floating gyroscopes, flexible gyroscopes, electrostatic gyroscopes, etc., rely on the high-speed rotation of the rotor to achieve angular velocity information measurement.
With the development of related technologies, a variety of new principles of gyros have been developed, they have new features, making the gyro family's camp continue to expand. We also refer to devices that can measure the angular velocity or angular displacement of an object autonomously, including optical gyroscopes, vibratory gyroscopes, silicon micromachined gyroscopes, and the like.
Since Sperry invented the world's first practical gyroscope, gyro technology has experienced nearly a hundred years of development. The following picture is a brief review of the history of the development of gyro technology over the past 100 years.
Reviewing the 100-year development of gyro technology, they can be roughly divided into the following three stages:
Phase I: Mechanical Rotor Gyro Stage
Started in the 1940s, the representative application at the time was at the end of the Second World War The V-2 missile developed by Germany. Regardless of the mechanical rotor type gyro, its basic working principle is based on Newton's second law (F=ma). The development process of the traditional mechanical rotor type gyro can be said to be supported by the frame. The process of disturbing the torque. After a long period of time, the main problem in improving the performance of the gyro is how to overcome various external disturbance moments acting on the gyro frame axis, thus maintaining the precise orientation of the rotation axis in space. People have successfully developed liquid floating gyro, static pressure air floating gyro, dynamic pressure air floating gyro, three floating gyro and electrostatic gyro, etc. As shown in the following figure, the appearance photos of various mechanical rotor type gyroscopes are listed.
Phase II: Optical Gyro Stage
In the late 1960s and early 1970s, microcomputer technology began to introduce inertia In the navigation system, there is a strapdown inertial navigation system that directly attaches the gyroscope to the motion carrier. The strapdown inertial navigation system uses a mathematical platform to replace the original physical platform. The typical representative of the gyroscope used in the early strapdown inertial navigation system is the power-tuned gyroscope.
The optical gyro is a new solid-state gyro based on the new principle, which was developed according to Einstein's theory of relativity (E=mc2). In the mid-1970s, ring laser gyros were introduced.This is the biggest technological advancement in the history of the gyro; in the mid-1980s, the interferometric fiber optic gyroscope was successfully developed. The successful development of laser gyro and fiber optic gyroscope has opened up a new era of optical gyro navigation. The term optical gyro is derived from a mechanical rotor gyro, which is actually an angular rate sensor. As an inertial sensor with excellent performance, the optical gyro is worthy of the appearance of the strapdown inertial navigation system. On the contrary, it is because of its successful development that the strapdown inertial navigation system is practical.
At present, optical gyros mainly include ring laser gyro and interference fiber gyro (see the following figure), which are ideal components of strapdown inertial navigation system. , has been applied to almost all types of inertial navigation systems.
Phase III: Micromachined Gyro Stage
In the early 1980s, Micro ElectroMechanical Systems (MEMS) has caused people in the compelling cutting-edge technology of micro/nanotechnology (10^-6/10^-9 meters, respectively). Wide attention. Microelectromechanical systems refer to the technology of designing, processing, manufacturing, measuring and controlling micro/nano materials. It can integrate mechanical components, optical systems, drive components and electronic control systems into one micro unit of integral unit.
The MEMS can not only acquire, process and transmit information or instructions, but also act autonomously or according to external instructions in accordance with the acquired information. It uses microelectronics and micromachining techniques (including silicon micromachining, a combination of silicon surface micromachining, LIGA and wafer bonding technologies,Produces a wide range of sensors, actuators, actuators and microsystems with excellent performance, low cost and miniaturization. Microelectromechanical (MEMS) is a new multidisciplinary technology developed in recent years that will revolutionize human life in the future. It involves many disciplines such as mechanics, electronics, chemistry, physics, optics, biology, and materials.
On this basis, in the mid-1980s, micro-mechanical gyros, namely MEMS gyros, also known as silicon microgyros, appeared in micro/nano technology. It is processed on a silicon chip of less than 1 mm square by a microelectronic process similar to semiconductor processing technology. It is fabricated by integrating the mechanical devices and electronic circuits on a tiny silicon chip by using processes such as deposition, etching, and doping in semiconductor manufacturing. Finally, an integrated circuit chip-sized microgyroscope is formed. . After years of hard work, the first micromechanical gyroscope with MEMS technology was introduced in 1989, with a drift rate of 10 degrees per hour. Its emergence is a representative achievement in MEMS technology, and it has brought about a new revolution in the field of inertial technology.Due to the adoption of mature semiconductor processing technology, this gyro took only five or six years from concept to mass production.
Micromechanical gyro (MEMS gyro), like other vibratory gyros, works on the principle of Coriolis effect. All micromechanical gyros are non-rotating devices that achieve angular rate detection by acquiring the Coriolis acceleration effect on a vibrating mechanical component. That is, a proof mass is sinusoidally vibrated in a plane. If the plane is rotated at an angular rate then the Coriolis force causes the mass to sinusoidally vibrate in a direction perpendicular to the plane, the magnitude of which is proportional to. By measuring the motion caused by Coriolis force, the signal of Ω is obtained, which is the basic working principle of the micromachined gyroscope.
The successful development of low-cost micro-mechanical gyroscopes has greatly expanded the application field of inertial navigation systems, and many applications that could not be realized before have become reality. In particular, the process of tactical weapon guidance has been accelerated. Currently the most widely used in car navigation is the MEMS gyroscope.