Links and Joints

The rigid elements, like the base bolted to the floor or the individual sections, are referred to as links, and they can move relative to each other via joints. A robotic arm will habitually have revolute joints, think of simple hinges that articulate the different sections and allow them to rotate in different directions. The most common configuration includes 6 joints to allow for 6 degrees of freedom: 3 to translate, and 3 to rotate in all directions, allowing for total freedom of movement. Each joint is motorised and can be precisely controlled by setting a desired angle. Together, the links and joints define the reach and payload of the robot, how far it is able to go in space, and how much weight it is able to carry. By controlling each motor we can position the whole robot and move it around its workspace, the volume of space that is physically reachable. The first 3 joints are referred to as the major axes, responsible for translating in space, while the last 3 minor axes, are responsible for orienting in space. When looking at a robotic arm, we can also draw parallels to the human body, and it is often referred to axes 1-2 as shoulder, axis 3 as elbow, and axes 4-5-6 as the wrist.