revolute

A revolute joint, commonly referred to as a hinge, is a mechanical connection between two rigid bodies that permits rotation about a single fixed axis. It constrains five of the six possible relative motions, allowing only one rotational degree of freedom. In three-dimensional space this axis is typically fixed in the world frame or attached to one of the bodies, and the angle of rotation is called the joint angle.

In robotics and mechanism design, revolute joints are fundamental building blocks. They are modeled in kinematics using conventions such as the Denavit–Hartenberg framework, where the joint variable is theta and the joint axis is the common normal between links. The joint allows rotation with characteristics determined by construction, including potentially some backlash, stiffness, and friction. Practical realizations include a pin joint, hinge, or cylindrical joint, which may be lubricated and limited by mechanical stops.

Applications span a range of mechanisms including doors, lids, robotic arms, and leg or gripper joints. In analysis, revolute joints simplify forward and inverse kinematics because the orientation of connected links depends on the sum of the joint angles.

Variants include restricted revolute joints with limited angular range and compliant joints that permit minor translational movement. Related joints include the prismatic joint, which provides translation along an axis, and spherical joints, which allow three rotational axes.