Collision Checking

During planning, querying whether a given pose or path segment would make the robot hit itself or the environment.

Collision checking is a geometric query used in motion planning: given a set of joint angles (a configuration), forward kinematics first computes where every link is located in space, and then the query determines whether those geometric shapes intersect environmental obstacles or other parts of the robot itself; it can also return the closest distance and contact point. Sampling-based planners like RRT and PRM call it for every sampled point and every connecting edge, so it often accounts for a large share of total planning time. To keep it fast, a coarse pass is usually done first with bounding-volume hierarchies, followed by exact checks between convex shapes using an algorithm such as GJK. The open-source library FCL supports collision, distance, and continuous collision-detection queries; MoveIt checks both self-collision and environment collision, using an 'allowed collision matrix' to ignore link pairs that are always in contact by design. Three related but distinct concepts are worth separating: collision checking happens before execution, on the robot model; collision detection inside a physics engine is used for simulating contact; and collision detection for robot safety notices unexpected impacts during real-robot motion.

ExampleA robot arm needs to place a cup inside a cabinet; RRT samples a set of joint angles and runs collision checking on it: the forearm's capsule shape intersects the cabinet door's box shape, so that sample is discarded; the straight-line connection between two valid samples also has to be checked point by point at small steps.

Also called

Collision Query

Related

Self-Collision Checking · Collision Detection · Flexible Collision Library (FCL) · MoveIt Motion Planning Framework · Sampling-Based Planning · Bounding Volume (AABB / OBB)

Sources

Wikipedia: Motion planning（collision detection 与采样规划） (Chinese)
FCL: The Flexible Collision Library (GitHub)
MoveIt 2 Docs: Planning Scene tutorial（collision checking）