A gyroscope (from Ancient Greek γῦρος gŷros 'round' and σκοπέω skopéō 'to look') is a device used for measuring or maintaining orientation and angular velocity. It is a spinning wheel or disc in which the axis of rotation (spin axis) is free to assume any orientation by itself. When rotating, the orientation of this axis is unaffected by tilting or rotation of the mounting, due to the conservation of angular momentum.
Gyroscopes based on other operating principles also exist, such as the microchip-packaged MEMS gyroscopes found in electronic devices (sometimes called gyrometers), solid-state ring lasers, fibre optic gyroscopes, and the extremely sensitive quantum gyroscope..
Applications of gyroscopes include inertial navigation systems, such as in the Hubble Space Telescope, or inside the steel hull of a submerged submarine. Due to their precision, gyroscopes are also used in to maintain direction in tunnel mining. Gyroscopes can be used to construct , which complement or replace Magnetic Compass (in ships, aircraft and spacecraft, vehicles in general), to assist in stability (bicycles, motorcycles, and ships) or be used as part of an inertial guidance system.
MEMS gyroscope are popular in some consumer electronics, such as smartphones.
In the case of a gyroscope with two gimbals, the outer gimbal, which is the gyroscope frame, is mounted so as to pivot about an axis in its own plane determined by the support. This outer gimbal possesses one degree of rotational freedom and its axis possesses none. The second (inner) gimbal is mounted in the gyroscope frame (outer gimbal) so as to pivot about an axis in its own plane that is always perpendicular to the pivotal axis of the gyroscope frame (outer gimbal). This inner gimbal has two degrees of rotational freedom.
The axle of the spinning wheel (the rotor) defines the spin axis. The rotor is constrained to spin about an axis, which is always perpendicular to the axis of the inner gimbal. So the rotor possesses three degrees of rotational freedom and its axis possesses two. The rotor responds to a force applied to the input axis by a reaction force to the output axis.
A gyroscope flywheel will roll or resist about the output axis depending upon whether the output gimbals are of a free or fixed configuration. An example of some free-output-gimbal devices is the attitude control gyroscopes used to sense or measure the pitch, roll and yaw attitude angles in a spacecraft or aircraft.
The centre of gravity of the rotor can be in a fixed position. The rotor simultaneously spins about one axis and is capable of oscillating about the two other axes, and it is free to turn in any direction about the fixed point (except for its inherent resistance caused by rotor spin). Some gyroscopes have mechanical equivalents substituted for one or more of the elements. For example, the spinning rotor may be suspended in a fluid, instead of being mounted in gimbals. A control moment gyroscope (CMG) is an example of a fixed-output-gimbal device that is used on spacecraft to hold or maintain a desired attitude angle or pointing direction using the gyroscopic resistance force.
In some special cases, the outer gimbal (or its equivalent) may be omitted so that the rotor has only two degrees of freedom. In other cases, the centre of gravity of the rotor may be offset from the axis of oscillation, and thus the centre of gravity of the rotor and the centre of suspension of the rotor may not coincide.
The first known apparatus similar to a gyroscope (the "Whirling Speculum" or "Serson's Speculum") was invented by John Serson in 1743. It was used as a level, to locate the horizon in foggy or misty conditions.
The first instrument used more like an actual gyroscope was made by Johann Bohnenberger of Germany, who first wrote about it in 1817. At first he called it the "Machine".Johann G. F. Bohnenberger (1817) "Beschreibung einer Maschine zur Erläuterung der Gesetze der Umdrehung der Erde um ihre Axe, und der Veränderung der Lage der letzteren" (Description of a machine for the explanation of the laws of rotation of the Earth around its axis, and of the change of the orientation of the latter), Tübinger Blätter für Naturwissenschaften und Arzneikunde , vol. 3, pages 72–83.The French mathematician Poisson mentions Bohnenberger's machine as early as 1813: Simeon-Denis Poisson (1813) "Mémoire sur un cas particulier du mouvement de rotation des corps pesans" Memoir, Journal de l'École Polytechnique, vol. 9, pages 247–262. Available online at: Ion.org Bohnenberger's machine was based on a rotating massive sphere.A photograph of Bohnenberger's instrument is available on-line here: Ion.org ION Museum: The Machine of Bohnenberger. In 1832, American Walter R. Johnson developed a similar device that was based on a rotating disc.Walter R. Johnson (January 1832). "Description of an apparatus called the rotascope for exhibiting several phenomena and illustrating certain laws of rotary motion" , The American Journal of Science and Art, 1st series, vol. 21, no. 2, pages 265–280.Drawings of Walter R. Johnson's gyroscope ("rotascope") were used to illustrate phenomena in the following lecture: E.S. Snell (1856) "On planetary disturbances," Board of Regents, Tenth Annual Report of the Board of Regents of the Smithsonian Institution.... (Washington, D.C.: Cornelius Wendell, 1856), pages 175–190. The French mathematician Pierre-Simon Laplace, working at the École Polytechnique in Paris, recommended the machine for use as a teaching aid, and thus it came to the attention of Léon Foucault.
It was Foucault who gave the device its modern name, in an experiment to see (Greek skopeein 'to see') the Earth's rotation (Greek gyros 'circle, rotation'), which was visible in the 8 to 10 minutes before friction slowed the spinning rotor.
Circa 1911 the L. T. Hurst Mfg Co of Indianapolis started producing the "Hurst gyroscope" a toy gyroscope with a pull string and pedestal. Manufacture was at some point switched to Chandler Mfg Co (still branded Hurst). The product was later renamed to a "Chandler gyroscope", presumably because Chandler Mfg Co. took over rights to the gyroscope. Chandler continued to produce the toy until the company was purchased by TEDCO Inc. in 1982. The gyroscope is still produced by TEDCO today.
In the first several decades of the 20th century, other inventors attempted (unsuccessfully) to use gyroscopes as the basis for early flight recorder navigational systems by creating a stable platform from which accurate acceleration measurements could be performed (in order to bypass the need for star sightings to calculate position). Similar principles were later employed in the development of inertial navigation systems for ballistic missiles.MacKenzie, Donald. Inventing Accuracy: A Historical Sociology of Nuclear Missile Guidance. Cambridge: MIT Press, 1990. pp. 40–42.
During World War II, the gyroscope became the prime component for aircraft and anti-aircraft gun sights. The Little Top That Aims a Gun by Gold Sanders, Popular Science, July 1945 After the war, the race to miniaturize gyroscopes for guided missiles and weapons navigation systems resulted in the development and manufacturing of so-called midget gyroscopes that weighed less than and had a diameter of approximately . Some of these miniaturized gyroscopes could reach a speed of 24,000 revolutions per minute in less than 10 seconds.
Gyroscopes continue to be an engineering challenge. For example, the axle bearings have to be extremely accurate. A small amount of friction is deliberately introduced to the bearings, since otherwise an accuracy of better than of an inch (2.5 nm) would be required.
Three-axis MEMS-based gyroscopes are also used in portable electronic devices such as tablets, , and . This adds to the 3-axis acceleration sensing ability available on previous generations of devices. Together these sensors provide 6 component motion sensing; accelerometers for X, Y, and Z movement, and gyroscopes for measuring the extent and rate of rotation in space (roll, pitch and yaw). Some devices additionally incorporate a magnetometer to provide absolute angular measurements relative to the Earth's magnetic field. Newer MEMS-based inertial measurement units incorporate up to all nine axes of sensing in a single integrated circuit package, providing inexpensive and widely available motion sensing.
where represents precession, is represented by spin, is the nutation angle, and represents inertia along its respective axis. This relation is only valid with the Moment along the Y and Z axes are equal to 0.
The equation can be further reduced noting that the angular velocity along the z-axis is equal to the sum of the Precession and the Spin: , Where represents the angular velocity along the z axis.
or
Gyroscopic precession is torque induced. It is the rate of change of the angular momentum that is produced by the applied torque. Precession produces counterintuitive dynamic results such as a spinning top not falling over. Precession is used in aerospace applications for sensing changes of attitude and direction.
In modern times, the gyrostat concept is used in the design of attitude control systems for orbiting spacecraft and satellites.Peter C. Hughes (2004). Spacecraft Attitude Dynamics For instance, the Mir space station had three pairs of internally mounted flywheels known as gyrodynes or control moment gyroscopes.D. M. Harland (1997) The MIR Space Station (Wiley); D. M. Harland (2005) The Story of Space Station MIR (Springer).
In physics, there are several systems whose dynamical equations resemble the equations of motion of a gyrostat.C. Tong (2009). American Journal of Physics vol. 77, pages 526–537 Examples include a solid body with a cavity filled with an inviscid, incompressible, homogeneous liquid,N.N. Moiseyev and V.V. Rumyantsev (1968). Dynamic Stability of Bodies Containing Fluid (Springer, New York) the static equilibrium configuration of a stressed elastic rod in elastica theory,Joseph Larmor (1884). Proc. London Math. Soc. vol. 15, pages 170–184 the polarization dynamics of a light pulse propagating through a nonlinear medium,M.V. Tratnik and J.E. Sipe (1987). Physical Review A vol. 35, pages 2965–2975 the Lorenz system in chaos theory,A.B. Gluhovsky (1982). Soviet Physics Doklady vol. 27, pages 823–825 and the motion of an ion in a Penning trap mass spectrometer.S. Eliseev et al. (2011). Physical Review Letters vol. 107, paper 152501
High quality wine-glass resonators are used for precise sensors like HRG.Lynch, D.D.: HRG development at Delco, Litton, and Northrop Grumman. In: Proceedings of Anniversary Workshop on Solid-State Gyroscopy, 19–21 May 2008. Yalta, Ukraine. Kyiv-Kharkiv. ATS of Ukraine, (2009)
When the Boeing 757-200 entered service in 1983, it was equipped with the first suitable ring laser gyroscope. This gyroscope took many years to develop, and the experimental models went through many changes before it was deemed ready for production by the engineers and managers of Honeywell and Boeing. It was an outcome of the competition with mechanical gyroscopes, which kept improving. The reason Honeywell, of all companies, chose to develop the laser gyro was that they were the only one that did not have a successful line of mechanical gyroscopes, so they would not be competing against themselves. The first problem they had to solve was that with laser gyros rotations below a certain minimum could not be detected at all, due to a problem called "lock-in", whereby the two beams act like coupled oscillators and pull each other's frequencies toward convergence and therefore zero output. The solution was to shake the gyro rapidly so that it never settled into lock-in. Paradoxically, too regular of a dithering motion produced an accumulation of short periods of lock-in when the device was at rest at the extremities of its shaking motion. This was cured by applying a random white noise to the vibration. The material of the block was also changed from quartz to a new glass ceramic Cer-Vit, made by Owens Corning, because of helium leaks.Donald MacKenzie, Knowing Machines: Essays in Technical Change, MIT Press, 1996, Chapter 4: From the Luminiferous Ether to the Boeing 757
The GP-B gyro consists of a nearly-perfect spherical rotating mass made of fused quartz, which provides a dielectric support for a thin layer of niobium superconducting material. To eliminate friction found in conventional bearings, the rotor assembly is centered by the electric field from six electrodes. After the initial spin-up by a jet of helium which brings the rotor to 4,000 RPM, the polished gyroscope housing is evacuated to an ultra-high vacuum to further reduce drag on the rotor. Provided the suspension electronics remain powered, the extreme rotational symmetry, lack of friction, and low drag will allow the angular momentum of the rotor to keep it spinning for about 15,000 years.
A sensitive DC SQUID that can discriminate changes as small as one quantum, or about 2 Wb, is used to monitor the gyroscope. A precession, or tilt, in the orientation of the rotor causes the London moment magnetic field to shift relative to the housing. The moving field passes through a superconducting pickup loop fixed to the housing, inducing a small electric current. The current produces a voltage across a shunt resistance, which is resolved to spherical coordinates by a microprocessor. The system is designed to minimize Lorentz torque on the rotor.
Since the gyroscope allows the calculation of orientation and rotation, designers have incorporated them into modern technology. The integration of the gyroscope has allowed for more accurate recognition of movement within a 3D space than the previous lone accelerometer within a number of smartphones. Gyroscopes in consumer electronics are frequently combined with accelerometers for more robust direction- and motion-sensing. Examples of such applications include smartphones such as the Samsung Galaxy Note 4, HTC Titan, Nexus 5, iPhone 5s, Nokia 808 PureView and Sony Xperia, game console peripherals such as the Sixaxis and the Wii Remote, and virtual reality headsets such as the Oculus Rift. Some features of Android phones like PhotoSphere or 360 Camera and to use VR gadget do not work without a gyroscope sensor in the phone.
Nintendo has integrated a gyroscope into the Wii console's Wii Remote controller by an additional piece of hardware called "Wii MotionPlus".Frank Caron (Aug 2008). Of gyroscopes and gaming: the tech behind the Wii MotionPlus
The company has also used gyroscopes in the Nintendo Switch Joy-Con controllers.
, ars technica
It is also included in the 3DS, [[Wii U]] GamePad, and [[Nintendo Switch]] [[Joy-Con]] and Pro controllers, which detect movement when turning and shaking.
Cruise ships use gyroscopes to level motion-sensitive devices such as self-leveling pool tables.
An electric powered flywheel gyroscope inserted in a bicycle wheel is sold as an alternative to training wheels.
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