Gimbal

Source: Wikipedia, the free encyclopedia.
This article is about the pivoted support system. For the GIMBAL UFO video, see
USS Theodore Roosevelt UFO incidents
.
Illustration of a simple three-axis gimbal set; the center ring can be vertically fixed

A gimbal is a pivoted support that permits rotation of an object about an axis. A set of three gimbals, one mounted on the other with

pitching and rolling
.

The gimbal suspension used for mounting compasses and the like is sometimes called a Cardan suspension after Italian mathematician and physicist Gerolamo Cardano (1501–1576) who described it in detail. However, Cardano did not invent the gimbal, nor did he claim to. The device has been known since antiquity, first described in the 3rd c. BC by Philo of Byzantium, although some modern authors support the view that it may not have a single identifiable inventor.[1][2]

History

Cardan suspension in Villard de Honnecourt's sketchbook (ca. 1230)
Early modern dry compass suspended by gimbals (1570)

The gimbal was first described by the Greek inventor Philo of Byzantium (280–220 BC).[3][4][5][6] Philo described an eight-sided ink pot with an opening on each side, which can be turned so that while any face is on top, a pen can be dipped and inked — yet the ink never runs out through the holes of the other sides. This was done by the suspension of the inkwell at the center, which was mounted on a series of concentric metal rings so that it remained stationary no matter which way the pot is turned.[3]

In

Ancient China, the Han dynasty (202 BC – 220 AD) inventor and mechanical engineer Ding Huan created a gimbal incense burner around 180 AD.[3][7][8] There is a hint in the writing of the earlier Sima Xiangru (179–117 BC) that the gimbal existed in China since the 2nd century BC.[9] There is mention during the Liang dynasty (502–557) that gimbals were used for hinges of doors and windows, while an artisan once presented a portable warming stove to Empress Wu Zetian (r. 690–705) which employed gimbals.[10] Extant specimens of Chinese gimbals used for incense burners date to the early Tang dynasty (618–907), and were part of the silver-smithing tradition in China.[11]

The authenticity of Philo's description of a cardan suspension has been doubted by some authors on the ground that the part of Philo's Pneumatica which describes the use of the gimbal survived only in an

Hellenistic original,[17] a view recently also shared by the classicist Andrew Wilson (2002).[18]

The

ancient Roman author Athenaeus Mechanicus, writing during the reign of Augustus (30 BC–14 AD), described the military use of a gimbal-like mechanism, calling it "little ape" (pithêkion). When preparing to attack coastal towns from the sea-side, military engineers used to yoke merchant-ships together to take the siege machines up to the walls. But to prevent the shipborne machinery from rolling around the deck in heavy seas, Athenaeus advises that "you must fix the pithêkion on the platform attached to the merchant-ships in the middle, so that the machine stays upright in any angle".[19]

After antiquity, gimbals remained widely known in the Near East. In the Latin West, reference to the device appeared again in the 9th century recipe book called the Little Key of Painting' (mappae clavicula).[20] The French inventor Villard de Honnecourt depicts a set of gimbals in his sketchbook (see right). In the early modern period, dry compasses were suspended in gimbals.

Verb form etymology

The word "gimbal" began as a noun. Most modern dictionaries continue to list it as such. Lacking a convenient term to describe the swinging movement of a rocket engine, engineers began also using the word "gimbal" as a verb. When a thrust chamber is swung by an attached actuator, the movement is referred to as "gimballed" or "gimballing". Official rocket documentation reflects this usage.

Applications

In a set of three gimbals mounted together, each offers a degree of freedom: roll, pitch and yaw

Inertial navigation

In inertial navigation, as applied to ships and submarines, a minimum of three gimbals are needed to allow an

orthogonally mounted gyros to sense rotation about all axes in three-dimensional space. The gyro outputs are kept to a null through drive motors on each gimbal axis, to maintain the orientation of the IMU. To accomplish this, the gyro error signals are passed through "resolvers
" mounted on the three gimbals, roll, pitch and yaw. These resolvers perform an automatic matrix transformation according to each gimbal angle, so that the required torques are delivered to the appropriate gimbal axis. The yaw torques must be resolved by roll and pitch transformations. The gimbal angle is never measured. Similar sensing platforms are used on aircraft.

In inertial navigation systems, gimbal lock may occur when vehicle rotation causes two of the three gimbal rings to align with their pivot axes in a single plane. When this occurs, it is no longer possible to maintain the sensing platform's orientation.[citation needed]

Rocket engines

Main article: Gimbaled thrust

In

roll
axis.

Photography and imaging

A Baker-Nunn satellite-tracking camera on an altitude-altitude-azimuth mount

Gimbals are also used to mount everything from small camera lenses to large photographic telescopes.

In portable photography equipment, single-axis gimbal heads are used in order to allow a balanced movement for camera and lenses.

center of gravity
, thus allowing for easy and smooth manipulation while tracking moving subjects.

Very large gimbal mounts in the form 2 or 3 axis

satellite photography
for tracking purposes.

Gyrostabilized gimbals which house multiple sensors are also used for airborne surveillance applications including airborne law enforcement, pipe and power line inspection,

laser range finder, and illuminators.[23]

Gimbal systems are also used in scientific optics equipment. For example, they are used to rotate a material sample along an axis to study their angular dependence of optical properties.[24]

Film and video

NEWTON S2 gimbal for remote control and 3-axis stabilization of a RED camera, Teradek lens motors and Angeniuex lens.
NEWTON S2 gimbal for remote control and 3-axis stabilization of a RED camera, Teradek lens motors and Angénieux lens

Handheld 3-axis gimbals are used in stabilization systems designed to give the camera operator the independence of handheld shooting without camera vibration or shake. There are two versions of such stabilization systems: mechanical and motorized.

Mechanical gimbals have the sled, which includes the top stage where the camera is attached, the post which in most models can be extended, with the monitor and batteries at the bottom to counterbalance the camera weight. This is how the Steadicam stays upright, by simply making the bottom slightly heavier than the top, pivoting at the gimbal. This leaves the

center of gravity
of the whole rig, however heavy it may be, exactly at the operator's fingertip, allowing deft and finite control of the whole system with the lightest of touches on the gimbal.

Powered by three brushless motors, motorized gimbals have the ability to keep the camera level on all axes as the camera operator moves the camera. An inertial measurement unit (IMU) responds to movement and utilizes its three separate motors to stabilize the camera. With the guidance of algorithms, the stabilizer is able to notice the difference between deliberate movement such as pans and tracking shots from unwanted shake. This allows the camera to seem as if it is floating through the air, an effect achieved by a Steadicam in the past. Gimbals can be mounted to cars and other vehicles such as drones, where vibrations or other unexpected movements would make tripods or other camera mounts unacceptable. An example which is popular in the live TV broadcast industry, is the Newton 3-axis camera gimbal.

Marine chronometers

The rate of a mechanical marine chronometer is sensitive to its orientation. Because of this, chronometers were normally mounted on gimbals, in order to isolate them from the rocking motions of a ship at sea.

Gimbal lock

Main article: Gimbal lock
Gimbal with 3 axes of rotation. When two gimbals rotate around the same axis, the system loses one degree of freedom.

Gimbal lock is the loss of one degree of freedom in a three-dimensional, three-gimbal mechanism that occurs when the axes of two of the three gimbals are driven into a parallel configuration, "locking" the system into rotation in a degenerate two-dimensional space.

The word lock is misleading: no gimbal is restrained. All three gimbals can still rotate freely about their respective axes of suspension. Nevertheless, because of the parallel orientation of two of the gimbals' axes there is no gimbal available to accommodate rotation about one axis.

See also

References

  1. ^ Needham, Joseph. (1986). Science and Civilization in China: Volume 4, Physics and Physical Technology; Part 2, Mechanical Engineering. Taipei: Caves Books Ltd. Page 229.
  2. ISBN 1-4020-5598-6
    .
  3. ^ a b c d Sarton, George (1959). A History of Science: Hellenistic Science and Culture in the Last Three centuries B.C. Cambridge: Harvard University Press. pp. 349–350.
  4. ^ Carter, Ernest Frank (1967). Dictionary of Inventions and Discoveries. Philosophical Library. p. 74.
  5. ISBN 978-3-540-30169-1
    .
  6. ISBN 978-0-313-31342-4
    .
  7. ^ Needham, Joseph. (1986). Science and Civilization in China: Volume 4, Physics and Physical Technology; Part 2, Mechanical Engineering. Taipei: Caves Books Ltd. p.233.
  8. ISBN 978-0520214842
    .
  9. ^ Needham, Joseph. (1986). Science and Civilization in China: Volume 4, Physics and Physical Technology; Part 2, Mechanical Engineering. Taipei: Caves Books Ltd. pp.233–234.
  10. ^ Needham, Joseph. (1986). Science and Civilization in China: Volume 4, Physics and Physical Technology; Part 2, Mechanical Engineering. Taipei: Caves Books Ltd. p.234.
  11. ^ Needham, Joseph. (1986). Science and Civilization in China: Volume 4, Physics and Physical Technology; Part 2, Mechanical Engineering. Taipei: Caves Books Ltd. pp.234–235.
  12. ^ Needham, Joseph. (1986). Science and Civilization in China: Volume 4, Physics and Physical Technology; Part 2, Mechanical Engineering. Taipei: Caves Books Ltd. p.236.
  13. ^ Hill, D. R. (1977). History of Technology. Vol. Part II. p. 75.
  14. ^ Carra de Vaux: "Le livre des appareils pneumatiques et des machines hydrauliques de Philon de Byzance d'après les versions d'Oxford et de Constantinople", Académie des Inscriptions et des Belles Artes: notice et extraits des mss. de la Bibliothèque nationale, Paris 38 (1903), pp.27-235
  15. ^ Sarton, George. (1959). A History of Science: Hellenistic Science and Culture in the Last Three centuries B.C. New York: The Norton Library, Norton & Company Inc. SBN 393005267. pp.343–350.
  16. ISBN 978-0-521-79297-4
    .
  17. ^ Lewis, M. J. T. (1997). Millstone and Hammer: the Origins of Water Power. pp. 26–36.
  18. doi:10.1017/S0075435800032135
    .
  19. ^ Athenaeus Mechanicus, "On Machines" ("Peri Mēchanēmatōn"), 32.1-33.3
  20. ^ Needham, Joseph. (1986). Science and Civilization in China: Volume 4, Physics and Physical Technology; Part 2, Mechanical Engineering. Taipei: Caves Books Ltd. pp.229, 231.
  21. ^ "3-Axis Handheld GoPro Gimbals". gimbalreview.com. GimbalReview. 2017. Retrieved 7 May 2017.
  22. ^ "Article". Soviet Journal of Optical Technology. 43 (3). Optical Society of America, American Institute of Physics: 119. 1976.
  23. ^ Dietsch, Roy (2013). Airborne Gimbal Camera – Interface Guide.
  24. S2CID 115286364
    .

External links

  • Media related to Gimbals at Wikimedia Commons
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