# Gimbal

### Gimbal

Illustration of a simple two-axis gimbal set; the center ring can be vertically fixed

A gimbal is a pivoted support that allows the rotation of an object about a single axis. A set of three gimbals, one mounted on the other with orthogonal pivot axes, may be used to allow an object mounted on the innermost gimbal to remain independent of the rotation of its support (e.g. vertical in the first animation). For example, on a ship, the gyroscopes, shipboard compasses, stoves, and even drink holders typically use gimbals to keep them upright with respect to the horizon despite the ship's 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) described it in detail. However, Cardano did not invent the gimbal, nor did he claim to. The device has been known since antiquity and may not have a single identifiable inventor.[1][2]

## Contents

• History 1
• Applications 2
• Inertial navigation 2.1
• Rocket engines 2.2
• Photography and imaging 2.3
• Film and video 2.4
• Marine chronometers 2.5
• References 4

## 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]

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

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. ^ Francis C. Moon, The Machines of Leonardo da Vinci and Franz Reuleaux: Kinematics of Machines from the Renaissance to the 20th Century, p.314, Springer, 2007 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. ^ Seherr-Thoss, Hans-Christoph; Schmelz, Friedrich; Aucktor, Erich (2006). Universal Joints and Driveshafts: Analysis, Design, Applications. Springer. p. 1.
6. ^ Krebs, Robert E.; Krebs, Carolyn A. (2003). Groundbreaking Scientific Experiments, Inventions, and Discoveries of the Ancient World. Greenwood Press. p. 216.
7. ^ Needham, Joseph. (1986). Science and Civilization in China: Volume 4, Physics and Physical Technology; Part 2, Mechanical Engineering. Taipei: Caves Books Ltd. p.236.
8. ^ Hill, D. R. (1977). History of Technology. Part II. p. 75.
9. ^ 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
10. ^ 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.
11. ^ Lewis, M. J. T. (2001). Surveying Instruments of Greece and Rome. Cambridge University Press. p. 76 at Fn. 45.
12. ^ Lewis, M. J. T. (1997). Millstone and Hammer: the Origins of Water Power. pp. 26–36.
13. ^ Wilson, Andrew (2002). "Machines, Power and the Ancient Economy". The Journal of Roman Studies 92 (7): 1–32.
14. ^ Athenaeus Mechanicus, "On Machines" ("Peri Mēchanēmatōn"), 32.1-33.3
15. ^ 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.
16. ^ Needham, Joseph. (1986). Science and Civilization in China: Volume 4, Physics and Physical Technology; Part 2, Mechanical Engineering. Taipei: Caves Books Ltd. p.233.
17. ^ 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.
18. ^ Needham, Joseph. (1986). Science and Civilization in China: Volume 4, Physics and Physical Technology; Part 2, Mechanical Engineering. Taipei: Caves Books Ltd. p.234.
19. ^ 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.
20. ^ "GoPro Accessories - Gimbals". HobbyTech.com.au. Hobby Tech. 2014.
21. ^ "Article". Soviet Journal of Optical Technology (Optical Society of America, American Institute of Physics) 43 (3): 119. 1976.
22. ^ Dietsch, Roy (2013). Airborne Gimbal Camera – Interface Guide.

## References

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.

### Marine chronometers

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. Not limited to handheld shooting, 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.

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. Powered by three brushless motors, the 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.

A 3-axis gimbal with a camera attached

### Film and video

Gyrostabilized gimbals which house multiple sensors are also used for airborne surveillance applications including: airborne law enforcement, pipe and power line inspection, mapping, and ISR (intelligence, reconnaissance, and surveillance). Sensors include thermal imaging, daylight, low light cameras as well as laser range finder, and illuminators.[22]

Very large gimbal mounts in the form 2 or 3 axis altitude-altitude mounts[21] are used in satellite photography for tracking purposes.

In portable photography equipment, single-axis gimbal heads are used in order to allow a balanced movement for camera and lenses.[20] This proves useful in wildlife photography as well as in any other case where very long and heavy telephoto lenses are adopted: a gimbal head rotates a lens around its center of gravity, thus allowing for easy and smooth manipulation while tracking moving subjects.

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

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

### Photography and imaging

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.

In spacecraft propulsion, rocket engines are generally mounted on a pair of gimbals to allow a single engine to vector thrust about both the pitch and yaw axes; or sometimes just one axis is provided per engine. To control roll, twin engines with differential pitch or yaw control signals are used to provide torque about the vehicle's roll axis.

### Rocket engines

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.

In inertial navigation, as applied to ships and submarines, a minimum of three gimbals are needed to allow an inertial navigation system (stable table) to remain fixed in inertial space, compensating for changes in the ship's yaw, pitch, and roll. In this application, the Inertial Measurement Unit (IMU) is equipped with three 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.