Articulated Object

An object made of parts connected by joints that can rotate or slide relative to each other.

An articulated object is made of two or more rigid parts connected by joints that let them move relative to each other — a cabinet or refrigerator door swinging on a hinge (a revolute joint), a drawer sliding out on a rail (a prismatic joint), and also things like a laptop, scissors, or a faucet. Much of what a household robot needs to handle falls into this category. Manipulating them is harder than grasping a single rigid body: the robot has to recognize which part can move, where its joint axis is, and how far it can travel, then apply force along the constrained trajectory — pull it off-axis and it jams. In simulation, articulated objects are usually described as a tree of links and joints using formats such as URDF; a common asset library is PartNet-Mobility, released by the SAPIEN team in 2020, with 46 categories and 2,346 object models annotated with joints.

ExampleIn SimplerEnv's Google Robot “open/close drawer” task, the drawer is connected to the cabinet body by a prismatic joint, and the robot has to pull it out or push it back in along the rail direction.

Also called

jointed object

Related

Articulated Object Manipulation · PartNet-Mobility · Revolute Joint · Prismatic Joint · Articulation Estimation · Unified Robot Description Format

Sources

SAPIEN: A SimulAted Part-based Interactive ENvironment (PartNet-Mobility)
simpler-env/SimplerEnv (GitHub)