# Understand in seconds! How gyroscopes work

2023-03-28Archive

A gyroscope, also known as an angular velocity sensor, is an angular motion detection device that uses a momentum-sensitive shell of a high-speed rotating body to rotate about one or two axes orthogonal to rotational axis with respect to inertial space. At same time, it is based on other principles. A device with same function as angular motion detection device is also called a gyroscope.

Origin of name gyroscope

The origin of name gyroscope has a long history. According to research, in 1850, in order to study rotation of Earth, French physicist J. Foucault first discovered that rotor (rotor) during high-speed rotation of Earth, due to its inertia, its axis of rotation always points to a fixed position. Therefore, Foucault called instrument a combination Greek words gyro (rotation) and skopein (vision) as "gyroscopei".

A simple way to make earliest gyroscope is as follows: place a high-speed rotating gyroscope on a universal bracket and calculate angular velocity in direction of gyroscope. A simple circuit is shown in figure below.

Among them, golden rotor in middle is a gyroscope that will not be affected by inertial effect, and three surrounding "steel rings" will change due to change in position of device to detect current state of device, and axes on which these three are located "steel rings", are "three axes" in three-axis gyroscope, namely X-axis, Y-axis and Z-axis. The spatial space surrounded by three axes detects various actions together, and then uses various methods to read direction indicated by shaft, and automatically transmits data signal to control system. So, in beginning, main function of gyroscope is to measure angular velocity.

The main composition of gyroscope

Currently, when analyzing movement of a gyroscope from a mechanical point of view, it can be considered as a rigid body with a universal fulcrum, and gyroscope can rotate around this fulcrum with three degrees of freedom, so movement of gyroscope refers to rotational movement of a rigid body around a fixed point .More precisely, a gyroscope is a rotor-flywheel that rotates at high speed around a symmetrical axis. The gyroscope is mounted on a frame device so that axis of rotation of gyroscope has a degree of freedom of angular rotation, and in general, this device is called a gyroscope.

The main components of a gyroscope are: gyroscope rotor (synchronous motor, hysteresis motor, three-phase AC motor and other drag methods are often used to rotate gyroscope rotor around rotation axis at high speed). , and its speed is approximately constant). Inner and outer frames (or called inner and outer rings, which are structures to allow axis of rotation of gyroscope to obtain required degree of freedom of angular rotation); accessories (meaning torque motors, signal sensors, etc.).

How a gyroscope works

The gyroscope determines angular velocity. The principle of its operation is based on principle of Coriolis force: when an object moves rectilinearly in a coordinate system, assuming that coordinate system rotates, then during rotation object will feel a vertical force and acceleration in vertical direction.

The formation of typhoons is based on this principle. The rotation of Earth causes atmosphere to rotate. If atmosphere is rotated by a tangential force, it is easy to form a typhoon. However, direction of rotation of typhoon in northern hemisphere and southern hemisphere are different. The principle of Coriolis force is explained by a figurative metaphor.

Specifically, a gyroscope is a combination of axis of a circle. In fact, there is no difference between a static gyroscope and a moving gyroscope, if static gyroscope itself is absolutely balanced, then gyroscope can stand without relying on rotation, regardless of external factors. And if size of gyroscope itself is unbalanced, it will cause gyroscope model to tilt and fall when it is stationary. Therefore, an unbalanced gyroscope must rely on rotation to maintain balance.

The gyroscope itself is connected to gravity, due to influence of gravity, an unbalanced gyroscope, heavy end will go down, and light end will go up. In a gravitational field, falling speed of a heavy object takes time. When falling speed of an object is much less than rotational speed of gyroscope itself, it will cause gyroscope to shift and balance gyroscope itself. will constantly change during rotation and form direction of rotation speed upwards. Of course, if gyroscope is too focused, force of interaction between left and right gyroscope itself will not work either.

During rotation, if gyroscope collides with an external force, a certain point of gyroscope wheel will be loaded. The gyroscope will tilt immediately, and if potential energy of gyroscope force point is lower than rotation speed of gyroscope, force point will be tilted due to gyroscope Swipe to top corner. When moving at top angle of inclination, potential energy of power point of gyroscope still flows downward. This has effect that when gyroscope reaches lift, remaining potential energy of force point will push potential energy down when it is on lift.

The other end of diameter, opposite stress point, also has a corresponding potential energy. This potential energy is opposite to direction of movement of point of force. The point of force is downward rather than upward, and this point is called "force connection point". When bond force point rotates 180 degrees from top corner to bottom corner, bond force point will pull gyroscope up. Under action of interaction force between force point and coupling force, gyroscope returns to equilibrium.

The axis of rotation of a high-speed rotating object tends to be vertical with respect to an external force that changes its direction. Moreover, when tilting a rotating object laterally, gravity will act in direction of increasing tilt, and axis will move in vertical direction, which will cause a head bobbing motion (precessional motion). When gyroscopic shaft of gyroscope rotates around horizontal axis, due to rotation of Earth, force of vertical rotation acts on it, and rotating body of gyroscope performs precessional motion in direction of meridian in horizontal plane. . Used when axis is stationary parallel to meridian.

The role of gyroscope

What is difference between a gyroscope and a gravity sensor? There are many differences, but biggest difference is that gravity sensor has less sense of spatial displacement, and it's already very good that it can sense 6 directions, and gyroscope is circular. This is very important, it would not be an exaggeration to say that these are products of different levels.

Perhaps seeing this will still make everyone feel a little confused. Since gyroscope is very powerful, what use is it in mobile phones? Let's take a look.

The first major use is navigation. Since gyroscope was invented, it has been used for navigation. The Germans first applied it to V1 and V2 rockets. Therefore, if it works together with GPS, navigation capabilities of a mobile phone will reach an unprecedented level. In fact, many professional handheld GPS devices are also equipped with gyroscopes, and if appropriate software is installed on a mobile phone, its navigation capabilities are not inferior to navigators used on many ships and aircraft.

The second important use is that it can be used together with a camera on a mobile phone, such as anti-shake, which will greatly improve camera and camera experience of a mobile phone.

The third main application is sensors for various games, such as flying games, sports games, and even some first-person shooting games. The gyroscope fully tracks movement of player's hand to realize various effects of game. . Regarding this point, brothers who used Nintendo WII must have a deep feeling.

The fourth main use can be used as an input deviceYes. The gyroscope is equivalent to a 3D mouse. This function is very similar to game sensor in third main use, and it can even be considered as a type.

The fifth largest app is also app with most promise and scope for future. Let's focus on that. This is something that can help phones implement augmented reality in many ways. Augmented Reality is a concept that has emerged very recently, just like virtual reality, it is an application for computers. The general idea is that thanks to processing power of mobile phones or computers, people can have a deep understanding of some objects in reality. If you do not understand, for example, there is a building in front of you, point your mobile phone camera at it, and you can immediately get relevant parameters of building on screen, such as height, width, and height of building. If you connect to database, you can even get information about owner of building, construction time, current use, number of people it can accommodate, and so on.

This augmented reality technology is not being used to satisfy general curiosity. In real production, it has a wide range of applications. For example, when building a house, you can find out if a wall is crooked by taking a picture with your cell phone. telephone? How crooked? Another example: if you are an Iraqi soldier resisting US military, you usually need to carry this type of mobile phone with you and go to base to see what tanks, armored vehicles or helicopters come out, point and take a picture with your mobile phone and you can immediately judge Displays model, speed and direction of movement of weapon.

Two dynamic characteristics of a gyroscope

The gyroscope is an ancient and vital instrument. More than half a century has passed since first practical gyroscope appeared. Until now, gyroscope is still attracting people to study it. This is determined by its own characteristics. The most important basic characteristics of a gyroscope are its inertia or stiffness and precession, both of which are based on principle of conservation of angular momentum. From ground gyroscopes played by children, it has long been established that a rapidly rotating gyroscope can stand upright without falling down and remain perpendicular to ground, which reflects fixed axis of gyroscope. The theory of studying characteristics of movement of gyroscopes is a section of dynamics of rigid bodies moving around a fixed point, based on inertia of objects to study dynamics of rotating objects.

inertia or rigidity. When gyroscope rotor rotates at high speed, when no external torque acts on gyroscope, orientation of gyroscope rotation axis in inertial space remains stable, i.e. any change in axial direction of rotor is power. This physical phenomenon is called axis orientation or gyroscope stability. Its stability varies with following physical quantities: greater moment of inertia of rotor, better stability, greater angular velocity of rotor, better stability.

Precession. When rotor rotates at high speed, if an external torque acts on axis of outer ring, gyroscope will rotate around axis of inner ring; if an external torque acts on axis of inner ring, gyroscope will rotate around axis of outer ring. The direction of its angular velocity of rotation and direction of external torque are perpendicular to each other. This characteristic is called precession of gyroscope. The direction of precession angular velocity depends on direction of angular momentum H (consistent with direction of rotor angular velocity vector) and direction of external moment M, with angular velocity vector catching up with external moment along shortest path.

MEMS gyroscope

Seven conventional gyroscopes

Depending on inertia or stiffness and precession of gyroscope, various instruments or devices are made. Ordinary gyroscopes mainly include following types:

Gyrocompass. Gyroscope with three degrees of freedom to find and track geographic meridian for navigation and flying objects as a direction reference. The axis of outer ring is vertical, rotor axis is located horizontally in meridian plane, its positive end is directed to north, its center of gravity deviates from support center down or up along vertical axis. When rotor axis deviates from meridian plane, it deviates from horizontal plane at same time to create a force of gravity to make gyroscope enter meridian plane. This kind of gyroscopic compass using gravity is called a pendulum compass. In 21st century, it has evolved into an electronically controlled gyrocompass that uses an automatic control system to replace gravitational pendulum, and created a platform compass that can indicate horizontal plane and meridian plane at same time.

Gyroscope ratings. A gyroscopic device with two degrees of freedom used to directly measure angular velocity of a vehicle. Mount outer ring of balancing gyroscope on vehicle so that axis of inner ring is perpendicular to axis on which angular velocity is measured. When carrier, together with outer ring, precesses around measuring axis with angular velocity, gyroscopic moment will cause inner ring, together with rotor, to precess relative to carrier. The gyroscope has a spring to limit this relative precession, and precession angle of inner ring is proportional to deformation of spring. The gyroscopic momentum and angular velocity of planet carrier can be obtained from precession angle of inner ring at equilibrium. The integrating gyroscope differs from velocity gyroscope only by replacing spring limit with a linear damper. When vehicle rotates at any variable speed, output signal of integrating gyroscope is angle of rotation around measuring axis (ie, integral of angular velocity). The above two gyroscopes are widely used in long-range measurement systems or automatic control and inertial navigation platforms.

Gyrostabilized platform. With a gyroscope as its main component, it is a device that holds a stabilized object in a given position relative to inertial space. The stabilized platform usually uses a torque device on axis of platform frame, consisting of an outer ring and an inner ring, to create a balance between torque and disturbing torque to prevent gyroscope precession Stable platform is called dynamic gyrothem a stabilizer. Gyro-stabilized platforms are divided into single-axis, two-axis and three-axis gyro-stabilized platforms depending on number of rotation axes that an object can maintain stability. Gyro-stabilized platforms can be used to stabilize instruments and equipment that require precise orientation, such as gauges, antennas, etc., and have found wide application in aviation and maritime navigation systems and gimbals for fire control and radar. Various types of gyroscopes are used as components according to different circuit diagrams. Among them, gyroscope torque generated by advancing gyroscope is used to resist disturbing torque, and then output signal is used to control and photograph system.

Gyro sensor. Gyro Sensors are an easy-to-use positioning and control system based on free-space movements and gestures. Move mouse over an imaginary plane and cursor on screen will move with it and can draw circles around links and click buttons. These operations can be easily implemented while you are speaking or away from table. The gyroscope sensor was originally applied to helicopter model and has been widely used in mobile handheld devices such as mobile phones (IPHONE triaxial gyroscope technology).

Fiber optic gyroscope. The fiber optic gyroscope is a sensing element based on a fiber optic coil, and light emitted by laser diode propagates along fiber optic fiber in two directions. Changing path of light propagation determines angular displacement of sensing element. Compared with traditional mechanical gyroscope, fiber optic gyroscope has advantages of solid state, no rotating and rubbing parts, long service life, large dynamic range, instant start, simple structure, small size and light weight. Compared with laser gyroscope, fiber optic gyroscope has no fixation problems and does not require precise processing of optical path in quartz block, so its cost is lower.

Laser gyroscope. The principle of operation of a laser gyroscope is to use optical path difference to measure angular velocity of rotation (the Sagnac effect). In a closed optical path, two beams of light emitted by same light source and transmitted clockwise and counterclockwise interfere with light, and angular velocity of rotation of closed optical path can be measured by detecting phase difference or change in interference fringe.

MEMS gyroscope. MEMS-based gyroscopes are much cheaper than fiber optic or laser gyroscopes, but accuracy of their use is very low, and in order to improve accuracy of use, it is necessary to use a reference sensor to compensate. The MEMS gyroscope uses a variable Coriolis force caused by mutually orthogonal vibration and rotation. The MEMS gyroscope uses Coriolis to convert angular velocity of a rotating object into a DC voltage signal proportional to angular velocity. Its main components pass alloying technology, photolithography technology, corrosion technology, LIGA technology, packaging technology and other mass production.

Application of gyroscope

Application of gyroscope in aerospace industry

The gyroscope was first used for navigation, but with development of science and technology, it has also become widely used in aviation and astronautics.

A gyroscopic device can be used not only as an indicating device, but, more importantly, it can be used as a sensitive element in an automatic control system, that is, a signal sensor. According to needs, gyroscopic instrument can provide accurate signals such as azimuth, level, position, speed and acceleration, so that pilot or use autopilot to control aircraft, ship or space shuttle and other flying objects to fly. like carrier satellites or space exploration rockets, these signals are directly used to control attitude and orbit of aircraft. As a stabilizer, a gyroscope can make a train move along a monorail, it can reduce sway of a ship in wind and waves, it can make a camera mounted on an airplane or satellite stable relative to ground, and so on.

As a tool for precision testing, gyroscopes can provide accurate azimuth fixes for ground objects, mine tunnels, underground railways, drilling and missile pits, etc.

It can be seen that scope of gyroscopic instruments is quite extensive, and they occupy an important place in modern defense and national economic construction.

Innovative application of gyroscope in consumer electronics

The advent of gyroscopes opened up a wide range of applications in consumer electronics. For example, in terms of input methods, after keyboard, mouse and touch screen, gyroscope has brought us gesture input. Due to its high precision, it can even realize electronic signatures, and also makes smartphones smarter. In addition to mobile Internet access and fast data processing, it can also "observe situation" and provide related services.

Navigation. Since gyroscope was invented, it has been used for navigation. The Germans first applied it to V1 and V2 rockets. Therefore, if it works together with GPS, navigation capabilities of a mobile phone will reach an unprecedented level. In fact, many professional handheld GPS devices are also equipped with gyroscopes, and if appropriate software is installed on a mobile phone, its navigation capabilities are not inferior to navigators used on many ships and aircraft.

Camera stabilization. The gyroscope can be used together with camera on mobile phone, such as anti-shake, which will greatly improve camera and mobile phone camera experience.

Improve your gaming experience. Sensors for various mobile games such as flying games, sports games, and even some first-person shooting games. The gyroscope fully tracks movement of player's hand to realize various game effects, such as changing horizontal screen to a vertical screen, cornering racing and more .

As an input device. The gyroscope can also be used as an input device, which is equivalent to a 3D mouse. This function is very similar to game sensor in third main use, and can even be considered a type.

At same time, in addition to familiar smartphones, cars also use a variety of MEMS gyroscopes. High-end vehicles use 25 to 40 MEMS sensors to detect various parts of operating status to provide information to on-board computer, allowing users to better control vehicle.