Six degrees of freedom (6DoF) refers to motion of a rigid body in three-dimensional space, namely the ability to move forward/backward, up/down, left/right (translation in three perpendicular axes) combined with rotation about three perpendicular axes (pitch, yaw, roll). As the movement along each of the three axes is independent of each other and independent of the rotation about any of these axes, the motion indeed has six degrees of freedom.
Robotics
Robot arms are often categorized by their degrees of freedom (typically achieving more than six degrees of freedom). This number typically refers to the number of single-axis rotational joints in the arm, where a higher number indicates an increased flexibility in positioning a tool. This is a practical metric, in contrast to the abstract definition of degrees of freedom which measures the aggregate positioning capability of a system.[1] Dean Kamen, inventor of the Segway, recently unveiled a prototype robotic arm with 21 degrees of freedom for DARPA. Humanoid robots 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 and neck.[2]
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 are made relevant through software that integrate the data based on the needs and programming of the users.
Ascension Technology Corporation has recently created a 6DoF device small enough to fit in a biopsy needle, allowing physicians to better research at minute levels. The new sensor passively senses pulsed DC magnetic fields generated by either a cubic transmitter or a flat transmitter and is available for integration and manufacturability by medical OEMs.[3]
Other uses
Six degrees of freedom is also a gameplay style wherein there is often no gravity, and players are free to move in any 3-dimensional direction. It is used in games such as Kidou Senshi Z-Gundam: Hot Scramble, Star Cruiser, Descent and its sequels, and to a lesser extent the Homeworld and Zone Of The Enders games.
First-person shooter (FPS) games generally provide four degrees of freedom (five counting jumping/crouching/swimming, or even six counting leaning.) The player can move in any direction along the ground and can alter pitch and yaw, but not roll. However, Futuremark Games Studio's Shattered Horizon, a space combat FPS game in zero gravity, allows the player to use all six degrees of freedom.
The acronym 3DoF, meaning just movement in the three dimensions and not rotation, is sometimes encountered.
The game controller of the PlayStation 3 contains a "Sixaxis" feature, which makes use of the six degrees of freedom. The Sixense TrueMotion is similar but for the PC.
See also
- Degrees of freedom (mechanics)
- Ship motions, an example in a vehicle.
References
- ^ Paul, Richard P., Robot Manipulators: Mathematics, Programming, and Control, MIT Press, 1981.
- ^ Craig, John J., Introduction to Robotics: Mechanics and Control, Addison-Wesley, 1986.
- ^ Medical News Today. Ascension Develops World's Smallest Six Degrees-of-Freedom Sensor For Emerging Medical Procedures. 25 Aug 2008