Robotic Manipulation · Lecture 1

Robot Joint Types

Each joint type constrains motion differently — and therefore contributes a different number of degrees of freedom. Click any joint to explore.

Type 01
Revolute
1 DOF — rotation only
rotation axis ↑
Rotates around a single fixed axis. The most common joint in robot arms.
elbow shoulder pan wrist flex SO-101 ×6
Type 02
Prismatic
1 DOF — translation only
linear axis ↕
Slides linearly along a single axis. No rotation — pure translation.
linear actuator CNC Z-axis telescoping arm
Type 03
Ball & Socket
3 DOF — full rotation
pitch · yaw · roll
Allows rotation around all three axes simultaneously. Maximum rotational freedom.
human shoulder hip joint camera mount
Type 04
Helical (Screw)
1 DOF — coupled rotation + translation
rotate → translate
Rotation and translation are coupled — like a bolt through a nut. Turning produces advancing.
lead screw bolt & nut drill press
Type 05
Planar
3 DOF — translation in plane + rotation
X Y x · y · θ in plane
Moves freely within a plane — x, y translation plus rotation around the vertical axis.
SCARA robot 2D gantry flatbed plotter
Type 06
Cylindrical
2 DOF — rotation + independent translation
rotate + slide (independent)
Combines rotation around and translation along the same axis, independently controlled.
cylindrical robot turret lift pick & place
SO-101

All 6 joints in the SO-101 are revolute — each contributes exactly 1 DOF through rotation around a single axis. Chaining 5 revolute joints gives the arm its 5 positioning DOF, with the 6th motor actuating the gripper. This is typical of most modern robot arms: simple 1-DOF joints, stacked to produce complex workspace coverage.