configuration space
In plain wordsAn imaginary space in which a robot's whole body position is a single point, which turns 'move this many-jointed robot without hitting things' into 'find a path for a dot'.
The space of all possible configurations of a robot, each a complete specification of where every point of its body is, with dimension equal to the robot's degrees of freedomdegrees of freedom, n.: The number of independent ways something can move. A robot arm with six motorized joints has six; a free-floating object can slide three ways and turn three ways.. For an arm with n revolute joints it is the n-dimensional space of joint angles (topologically a torus, since angles wrap around); for a car moving on a plane it is position plus heading. Obstacles in the physical workspace map to configuration-space obstacles, the sets of configurations in which the robot would collide; their complement is the free space. Motion planningmotion planning, n.: Working out how a robot should move from where it is to where it needs to be, without hitting anything and within the limits of what its body can do. then reduces to finding a continuous path for a point through free space, which treats robots of very different shapes in one framework. Configuration-space obstacles are impractical to compute explicitly in high dimensions, which is why sampling-based planners such as probabilistic roadmapsprobabilistic roadmap, n.: A planning method that scatters many random safe robot poses through a space and links nearby ones into a road network, so routes can later be looked up quickly, as on a map. and rapidly exploring random treesrapidly exploring random tree, n.: A planning method that grows a branching tree of random moves outward from the robot's starting position, spreading quickly into open space until a branch reaches the goal. probe free space with a collision checker instead.
In configuration space the arm's whole motion is one curve threading between two obstacle regions.
Origin
The term comes from analytical mechanics, where it denotes the space of a system's generalized coordinates. Tomás Lozano-Pérez brought it into robotics in work with Michael Wesley (1979) and in 'Spatial Planning: A Configuration Space Approach' (IEEE Transactions on Computers, 1983); Shriram Udupa's 1977 Caltech thesis anticipated the idea of 'growing' obstacles.
Usage note
Distinct from the workspace (or task space), the region physically reachable by the end effector, and from a dynamical system's state space, which adds velocities.
Related
- motion planningmotion planning, n.: Working out how a robot should move from where it is to where it needs to be, without hitting anything and within the limits of what its body can do.
- degrees of freedomdegrees of freedom, n.: The number of independent ways something can move. A robot arm with six motorized joints has six; a free-floating object can slide three ways and turn three ways.
- probabilistic roadmapprobabilistic roadmap, n.: A planning method that scatters many random safe robot poses through a space and links nearby ones into a road network, so routes can later be looked up quickly, as on a map.
- rapidly exploring random treerapidly exploring random tree, n.: A planning method that grows a branching tree of random moves outward from the robot's starting position, spreading quickly into open space until a branch reaches the goal.
- forward kinematicsforward kinematics, n.: The math that works out where a robot's hand or tool ends up, given the angles of all its joints, by chaining together the movement each joint adds.
- path planningpath planning, n.: Finding a route for a robot or vehicle from a start to a goal that avoids obstacles, usually the shortest or safest one, much as a navigation app finds a route on a map.
Sources
- Lozano-Pérez, T. (1983). Spatial planning: A configuration space approach. IEEE Transactions on Computers C-32(2), 108–120.
- LaValle, S. M. (2006). Planning Algorithms. Cambridge University Press.
Mentioned in
degrees of freedomdegrees of freedom, n.: The number of independent ways something can move. A robot arm with six motorized joints has six; a free-floating object can slide three ways and turn three ways., motion planningmotion planning, n.: Working out how a robot should move from where it is to where it needs to be, without hitting anything and within the limits of what its body can do., forward kinematicsforward kinematics, n.: The math that works out where a robot's hand or tool ends up, given the angles of all its joints, by chaining together the movement each joint adds., probabilistic roadmapprobabilistic roadmap, n.: A planning method that scatters many random safe robot poses through a space and links nearby ones into a road network, so routes can later be looked up quickly, as on a map., rapidly exploring random treerapidly exploring random tree, n.: A planning method that grows a branching tree of random moves outward from the robot's starting position, spreading quickly into open space until a branch reaches the goal.