clearance

Minimum clearance of path

Description

example

clearance(pathMetricsObj) returns the minimum clearance of the path. Clearance is measured as the minimum distance between poses on the path and obstacles in the specified map environment.

clearance(pathMetricsObj,'Type','states') returns the set of minimum distances for each state of the path, in the form of an (n-1)-element vector, where n is the number of poses.

Examples

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Compute smoothness, clearance, and validity of a planned path based on a set of poses and the associated map environment.

Load and Assign Map to State Validator

Create an occupancy map from an example map and set the map resolution.

load exampleMaps.mat; % simpleMap
mapResolution = 1; % cells/meter
map = occupancyMap(simpleMap,mapResolution);

Create a Dubins state space.

statespace = stateSpaceDubins;

Create a state validator based on occupancy map to store the parameters and states in the Dubins state space.

statevalidator = validatorOccupancyMap(statespace);

Assign the map to the validator.

statevalidator.Map = map;

Set the validation distance for the validator.

statevalidator.ValidationDistance = 0.01;

Update the state space bounds to be the same as the map limits.

statespace.StateBounds = [map.XWorldLimits;map.YWorldLimits;[-pi pi]];

Plan Path

Create an RRT* path planner and allow further optimization.

planner = plannerRRTStar(statespace,statevalidator);
planner.ContinueAfterGoalReached = true;

Reduce the maximum number of iterations and increase the maximum connection distance.

planner.MaxIterations = 2500;
planner.MaxConnectionDistance = 0.3;

Define start and goal states for the path planner as [x, y, theta] vectors. x and y are the Cartesian coordinates, and theta is the orientation angle.

start = [2.5, 2.5, 0]; % [meters, meters, radians]
goal = [22.5, 8.75, 0];

Plan a path from the start state to the goal state. The plan function returns a navPath object.

rng(100,'twister') % repeatable result
[path,solutionInfo] = plan(planner,start,goal);

Compute and Visualize Path Metrics

Create a path metrics object.

pathMetricsObj = pathmetrics(path,statevalidator);

Check path validity. The result is 1 (true) if the planned path is obstacle free. 0 (false) indicates an invalid path.

isPathValid(pathMetricsObj)
ans = logical

   1

Calculate the minimum clearance of the path.

clearance(pathMetricsObj)
ans = 
          0.21

Evaluate the smoothness of the path. Values close to 0 indicate a smoother path. Straight-line paths return a value of 0.

smoothness(pathMetricsObj)
ans = 
          2.21

Visualize the minimum clearance of the path.

show(pathMetricsObj)
legend('Planned Path','Minimum Clearance')

Input Arguments

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Information for path metrics, specified as a pathmetrics object.

See Also

Objects

Functions

Introduced in R2019b