Types of robotic chains

Degree of freedom in opened chains

Example of four degrees of freedom in open chain

In open chains it is easy to calculate how many degrees of freedom. For a robot just by calculating the rotations axes and prismatic axes. In the example up we have four revolute joints that means we have four degrees of freedom

Degree of freedom in closed chains

How to calculate degree of freedom for closed chains?

We need to define how many links, revolute joints and prismatic joints.

Example 1

Closed chain

In the example up we calculate degree of freedom this way:

3(5-1)-2(5)-2(0)= 2 dof

Example 2

Closed chain by a prismatic joint

Example 3

Closed chain

Stewart platform

How to calculate Stewart platform degree of freedom?