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A* VI

LabVIEW 2013 Robotics Module Help

Edition Date: June 2013

Part Number: 372983D-01

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Owning Palette: Path Planning VIs

Requires: Robotics Module

Plans a least-cost path through a static map to a goal reference within a map. Use this VI to return a single, optimal path.

This VI uses a best-first algorithm to search paths that are most likely to lead to the goal while minimizing the cost of traversing the path.

Details  Example

map reference in is a reference to the map that represents the robot environment. You can use the Create Directed Graph Map VI or Create Occupancy Grid Map VI to generate this LabVIEW class object.
start reference specifies the current position of the robot within the map. If this VI operates on a directed graph map or occupancy grid map, you can use the Get Node Reference VI or Get Cell Reference VI, respectively, to generate this LabVIEW class object.
goal reference specifies the position to which the robot should navigate within the map. If this VI operates on a directed graph map or occupancy grid map, you can use the Get Node Reference VI or Get Cell Reference VI, respectively, to generate this LabVIEW class object.
error in describes error conditions that occur before this node runs. This input provides standard error in functionality.
path references is an array of references to points on the map along the path this VI calculates. If no valid path exists is TRUE, LabVIEW returns a partial path. Otherwise, path references contains a complete path to the goal node.

You can use a partial path to direct a mobile robot to a point in the map that is nearer to the goal than the current position of the robot.
no valid path exists is TRUE if the path references do not end at the goal node.
error out contains error information. This output provides standard error out functionality.
path cost is the cost of traversing the path references. path cost returns Inf if no possible path exists or the map changes significantly.

A* Details

This VI uses an A* algorithm to plan an optimal path through a static map, which is a time-intensive operation. Use the AD* VI to plan a less-optimal path through a dynamic map more quickly and to replan the path as the map changes.

LabVIEW locks maps while this VI plans paths through them. While a map is locked, LabVIEW queues any updates to the map and applies them when this VI finishes planning a path.

Example

Refer to the Astar on Voronoi.lvproj in the labview\examples\robotics\Path Planning\Astar\Astar on Voronoi Graph directory for an example of using the A* VI.


 

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