# 'Degrees of Freedom' vs 'Functions' of a Robotic Arm

## One of the main things people are interested in when solving a complex robotic manipulator problem is the DoF and Functions. These two distinct pieces of terminology help to shortcut conversations and make sure everyone is talking on the same page!

14 Apr, 2022. 3 min read

### <!--td {border: 1px solid #ccc;}br {mso-data-placement:same-cell;}--><!--td {border: 1px solid #ccc;}br {mso-data-placement:same-cell;}-->What is the Definition of a ‘Degree of Freedom’ (In the context of Robotic Arms)?

A ‘Degree of Freedom’ (DoF) as it relates to robotic arms, is an independent joint that can provide freedom of movement of the manipulator, either in a rotational or translational (linear) sense. For every geometric axis that a joint can rotate around or extend along, this is counted as a Single Degree of Freedom.

In theory, there are quite a few types of joints that provide varying numbers of degrees of freedom in terms of rotation and translation (see the chart below). In practice, however, most robotic arms will be made up of a series of joints that provide one degree of freedom. The two most common joints are:

Revolute Joint: Providing one degree of rotational freedom

Prismatic Joint: Providing one degree of linear freedom

As such, robotic arms are often described in terms of how many total DoF they have. E.g. the Bravo 7 is a 6 Degree of Freedom robotic arm (Why not call it the Bravo 6? See the next section of this article). Of course, there are a variety of different types of robotic arms across different industries, ranging from one degree of freedom (sometimes called an ‘axis’) to over seven.

Chart Credit: Cavacece, Massimo & Vita, L.. (2005). On the Computation of degrees-of-freedom: A Didactic Perspective. 10.1115/DETC2005-84109.

Knowing and defining the Degrees of Freedom (along with other key parameters) allow for modeling the robotic system and implementation of AI algorithms to autonomously control the manipulator arm.