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Six degrees of freedom (6DOF) refers to the six mechanical degrees of freedom of movement of a
rigid body In physics, a rigid body (also known as a rigid object) is a solid body in which deformation is zero or so small it can be neglected. The distance between any two given points on a rigid body remains constant in time regardless of external fo ...
in
three-dimensional space Three-dimensional space (also: 3D space, 3-space or, rarely, tri-dimensional space) is a geometric setting in which three values (called ''parameters'') are required to determine the position of an element (i.e., point). This is the informal ...
. Specifically, the body is free to change
position Position often refers to: * Position (geometry), the spatial location (rather than orientation) of an entity * Position, a job or occupation Position may also refer to: Games and recreation * Position (poker), location relative to the dealer * ...
as forward/backward (surge), up/down (heave), left/right (sway)
translation Translation is the communication of the Meaning (linguistic), meaning of a #Source and target languages, source-language text by means of an Dynamic and formal equivalence, equivalent #Source and target languages, target-language text. The ...
in three
perpendicular In elementary geometry, two geometric objects are perpendicular if they intersect at a right angle (90 degrees or π/2 radians). The condition of perpendicularity may be represented graphically using the ''perpendicular symbol'', ⟂. It can ...
axes, combined with changes in orientation through
rotation Rotation, or spin, is the circular movement of an object around a '' central axis''. A two-dimensional rotating object has only one possible central axis and can rotate in either a clockwise or counterclockwise direction. A three-dimensional ...
about three perpendicular axes, often termed yaw (normal axis), pitch (transverse axis), and roll (longitudinal axis). Three degrees of freedom (3DOF), a term often used in the context of
virtual reality Virtual reality (VR) is a simulated experience that employs pose tracking and 3D near-eye displays to give the user an immersive feel of a virtual world. Applications of virtual reality include entertainment (particularly video games), e ...
, typically refers to tracking of rotational motion only: pitch, yaw, and roll.


Robotics

Serial and parallel manipulator systems are generally designed to position an end-effector with six
degrees of freedom Degrees of freedom (often abbreviated df or DOF) refers to the number of independent variables or parameters of a thermodynamic system. In various scientific fields, the word "freedom" is used to describe the limits to which physical movement or ...
, consisting of three in translation and three in orientation. This provides a direct relationship between actuator positions and the configuration of the manipulator defined by its forward and inverse kinematics.
Robot A robot is a machine—especially one programmable by a computer—capable of carrying out a complex series of actions automatically. A robot can be guided by an external control device, or the control may be embedded within. Robots may be ...
arms are described by their
degrees of freedom Degrees of freedom (often abbreviated df or DOF) refers to the number of independent variables or parameters of a thermodynamic system. In various scientific fields, the word "freedom" is used to describe the limits to which physical movement or ...
. This is a practical metric, in contrast to the abstract definition of degrees of freedom which measures the aggregate positioning capability of a system. In 2007, Dean Kamen, inventor of the Segway, unveiled a prototype robotic arm with 14 degrees of freedom for
DARPA The Defense Advanced Research Projects Agency (DARPA) is a research and development agency of the United States Department of Defense responsible for the development of emerging technologies for use by the military. Originally known as the Ad ...
.
Humanoid robot A humanoid robot is a robot resembling the human body in shape. The design may be for functional purposes, such as interacting with human tools and environments, for experimental purposes, such as the study of bipedal locomotion, or for other p ...
s typically have 30 or more degrees of freedom, with six degrees of freedom per arm, five or six in each leg, and several more in
torso The torso or trunk is an anatomical term for the central part, or the core, of the body of many animals (including humans), from which the head, neck The neck is the part of the body on many vertebrates that connects the head with the tors ...
and
neck The neck is the part of the body on many vertebrates that connects the head with the torso. The neck supports the weight of the head and protects the nerves that carry sensory and motor information from the brain down to the rest of the body. In ...
.


Engineering

The term is important in mechanical systems, especially biomechanical systems, for analyzing and measuring properties of these types of systems that need to account for all six degrees of freedom. Measurement of the six degrees of freedom is accomplished today through both AC and DC magnetic or electromagnetic fields in sensors that transmit positional and angular data to a processing unit. The data is made relevant through software that integrates the data based on the needs and programming of the users. The six degrees of freedom of a mobile unit are divided in two motional classes as described below. Translational envelopes: #Moving forward and backward on the X-axis. (Surge) #Moving left and right on the Y-axis. (Sway) #Moving up and down on the Z-axis. (Heave) Rotational envelopes: #Tilting side to side on the X-axis. ( Roll) #Tilting forward and backward on the Y-axis. ( Pitch) #Turning left and right on the Z-axis. ( Yaw) In terms of a headset, such as the kind used for
virtual reality Virtual reality (VR) is a simulated experience that employs pose tracking and 3D near-eye displays to give the user an immersive feel of a virtual world. Applications of virtual reality include entertainment (particularly video games), e ...
, rotational envelopes can also be thought of in the following terms: *Pitch: Nodding "yes" *Yaw: Shaking "no" *Roll: Bobbling from side to side


Operational envelope types

There are three types of operational envelope in the Six degrees of freedom. These types are ''Direct'', ''Semi-direct'' (conditional) and ''Non-direct,'' all regardless of the time remaining for the execution of the maneuver, the energy remaining to execute the maneuver and finally, if the motion is commanded via a biological entity (e.g. human), a robotical entity (e.g. computer) or both. #''Direct type'': Involved a degree can be commanded directly without particularly conditions and described as a normal operation. (An
aileron An aileron (French for "little wing" or "fin") is a hinged flight control surface usually forming part of the trailing edge of each wing of a fixed-wing aircraft. Ailerons are used in pairs to control the aircraft in roll (or movement arou ...
on a basic airplane) #''Semi-direct type'': Involved a degree can be commanded when some specific conditions are met. ( Reverse thrust on an aircraft) #''Non-direct type'': Involved a degree when is achieved via the interaction with its environment and cannot be commanded. (Pitching motion of a vessel at sea) Transitional type also exists in some vehicles. For example, when the
Space Shuttle The Space Shuttle is a retired, partially reusable low Earth orbital spacecraft system operated from 1981 to 2011 by the U.S. National Aeronautics and Space Administration (NASA) as part of the Space Shuttle program. Its official program na ...
operates in space, the craft is described as fully-direct-six because its six degrees can be commanded. However, when the Space Shuttle is in the earth's atmosphere for its return, the fully-direct-six degrees are no longer applicable for many technical reasons.


Game controllers

''Six degrees of freedom'' also refers to movement in video game-play.
First-person shooter First-person shooter (FPS) is a sub-genre of shooter video games centered on gun and other weapon-based combat in a first-person perspective, with the player experiencing the action through the eyes of the protagonist and controlling the pl ...
(FPS) games generally provide five degrees of freedom: forwards/backwards, slide left/right, up/down (jump/crouch/lie), yaw (turn left/right), and pitch (look up/down). If the game allows leaning control, then some consider it a sixth DOF; however, this may not be completely accurate, as a lean is a limited partial rotation. The term ''6DOF'' has sometimes been used to describe games which allow freedom of movement, but do not necessarily meet the full 6DOF criteria. For example, '' Dead Space 2'', and to a lesser extent, '' Homeworld'' and '' Zone Of The Enders'' allow freedom of movement. Some examples of true 6DOF games, which allow independent control of all three movement axes and all three rotational axes, include '' Elite Dangerous'', '' Shattered Horizon'', the '' Descent'' franchise, ''
Retrovirus A retrovirus is a type of virus that inserts a DNA copy of its RNA genome into the DNA of a host cell that it invades, thus changing the genome of that cell. Once inside the host cell's cytoplasm, the virus uses its own reverse transcriptase ...
'', '' Miner Wars'', '' Space Engineers'', '' Forsaken'' and '' Overload'' (from the same creators of ''Descent''). The space MMO '' Vendetta Online'' also features 6 degrees of freedom. Motion tracking hardware devices such as TrackIR and software-based apps lik
Eyeware Beam
are used for 6DOF head tracking. This device often finds its places in flight simulators and other vehicle simulators that require looking around the cockpit to locate enemies or simply avoiding accidents in-game. The acronym 3DOF, meaning movement in the three dimensions but not rotation, is sometimes encountered. The Razer Hydra, a motion controller for PC, tracks position and rotation of two wired
nunchuck is a traditional Okinawan martial arts weapon consisting of two sticks (traditionally made of wood), connected to each other at their ends by a short metal chain or a rope. It is approximately 30 cm (sticks) and 1 inch (rope). A person wh ...
s, providing six degrees of freedom on each hand. The
SpaceOrb 360 The SpaceOrb 360 is a 6DOF computer input device that is designed to be operated with two hands. Each of the 6 axes have 10-bit precision each when measuring the amount of force or torque applied. It has two right-index-finger buttons and four rig ...
is a 6DOF computer input device released in 1996 originally manufactured and sold by the SpaceTec IMC company (first bought by
Labtec Labtec Inc. was a manufacturer of computer accessories, founded in Vancouver, Washington, United States in 1982. They were best known for their budget range of peripherals such as keyboards, mice, microphones, speakers and webcams. Originall ...
, which itself was later bought by
Logitech Logitech International S.A. ( ; often shortened to Logi) is a Swiss multinational manufacturer of computer peripherals and software, with headquarters in Lausanne, Switzerland, and Newark, California. The company has offices throughout Europe ...
). The controllers sold with HTC VIVE provide 6DOF information by the lighthouse, which adopts Time of Flight (TOF) technology to determine the position of controllers.


See also

* * * * * *


References

{{DEFAULTSORT:Six Degrees Of Freedom Mechanics Biomedical engineering Video game gameplay Robot kinematics