Six degrees of freedom
Six degrees of freedom (6DOF), or sometimes six degrees of movement, refers to the six
Three degrees of freedom (3DOF), a term often used in the context of virtual reality, typically refers to tracking of rotational motion only: pitch, yaw, and roll.[1][2]
Robotics
Serial and parallel manipulator systems are generally designed to position an end-effector with six degrees of freedom, 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 arms are described by their degrees of freedom. This is a practical metric, in contrast to the abstract definition of degrees of freedom which measures the aggregate positioning capability of a system.[3]
In 2007,
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, rotational envelopes can also be thought of in the following terms:
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 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
Game controllers
Six degrees of freedom also refers to movement in video game-play.
First-person shooter (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,
Some examples of true 6DOF games, which allow independent control of all three movement axes and all three rotational axes, include
Motion tracking hardware devices such as
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 nunchucks, providing six degrees of freedom on each hand.
The
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
- Degrees of freedom (mechanics) – Number of independent parameters needed to define the state of a mechanical system
- Degrees of freedom problem – Multiple ways for multi-joint objects to realize a movement
- Euler angles – Description of the orientation of a rigid body
- Geometric terms of location – Directions or positions relative to the shape and position of an object
- Ship motions – Terms connected to the six degrees of freedom of motion
- Aircraft principal axes – Principal directions in aviation
References
- Road to VR. Retrieved 20 October 2019.
- ^ "Degrees of Freedom | Google VR |". Google Developers. September 2018. Retrieved 20 October 2019.
- OCLC 318374953.
- ted.com. March 2007. Archived from the originalon October 31, 2016. Retrieved 2017-02-26.
- OCLC 1025367636.