Glossary · Robotics
Degrees of freedom
Also known as: DOF, DoF
German: Freiheitsgrade
In robotics and mechanics, degrees of freedom are the number of independent coordinates needed to describe the position of a body or mechanism. A rigid body in space has six (three translations, three rotations); a robot's degrees of freedom usually equal its number of independent joints.
- Robotics
In one sentence
Degrees of freedom count the independent motions of a body or mechanism; a rigid body in space has six, a typical industrial robot six axes.
Example
A four-axis SCARA robot has four degrees of freedom, so it can position a part in X, Y and Z and rotate it about the vertical axis, but not tilt it.
How it applies
- Engineering: A task needs as many degrees of freedom as independent motions of the tool. Six are enough for any pose in space; a seventh (redundant) axis lets the robot avoid obstacles or singularities while holding the same tool pose.
- Operation: Positioners, linear tracks and turntables add external axes and extend the degrees of freedom of the whole cell.
- Documentation: Distinguish degrees of freedom of the arm from the number of axes of the complete system including external axes. The documentation team should state both in the technical data and use the abbreviation DOF only after introducing it.
Degrees of freedom vs. axes
For serial robots, each Joint axis adds one degree of freedom, so the terms are often used interchangeably. For parallel robots such as a Delta robot, several drives together produce fewer degrees of freedom at the tool, so the counts differ.