Robotics
Revolute joint
Definition
A revolute joint permits one link to rotate relative to another about a fixed joint axis. Its single relative degree of freedom is described by an angle.
Also known as: Rotary joint, Revolute joints
Updated
One allowed relative rotation
An ideal revolute joint constrains the other five relative freedoms between two spatial rigid links. Only rotation about the joint axis remains. Modern Robotics uses this joint as the basic building block of a serial robot arm.
A hinge provides a useful physical example. Its axis can move through world space as earlier joints move; “fixed axis” means fixed in the connected-link joint geometry, not necessarily fixed relative to the room.
Joint angle and travel limits
The joint coordinate measures rotation from a chosen zero position. The axis direction determines its positive sign. In a Denavit-Hartenberg model, the variable is the joint angle theta, as shown in the Robotics Toolbox's revolute-link definitions.
A finite angular travel range limits which configurations are available. It does not turn a one-degree-of-freedom joint into a different joint type.
Joint type is not actuator type
“Revolute” describes permitted relative motion. The Toolbox records motor, transmission, friction, and inertia properties separately from this kinematic choice. A prismatic joint instead permits one translation, while a spherical joint permits three relative rotational freedoms.
Sources
Related terms
Prismatic joint
A prismatic joint permits one link to translate relative to another along a fixed joint axis without relative rotation. Its single degree of freedom is described by a linear displacement.
Degrees of freedom
Degrees of freedom are the number of independent coordinates needed locally to describe a system configuration. In robotics, this count depends on the bodies, joints, and independent constraints in the model.
Kinematic chain
A kinematic chain is an arrangement of links connected by joints that constrains their relative motion. Open chains have no closed link loop, while closed chains contain at least one loop.