pathmetrics

Information for path metrics

Description

The pathmetrics object holds information for computing path metrics. Use object functions to calculate smoothness, clearance, and path validity based on a set of poses and the associated map environment.

Creation

Description

pathMetricsObj = pathmetrics(path) creates an object based on the input navPath object. The state validator is assumed to be a validatorOccupancyMap object. The path input sets the value of the Path property.

example

pathMetricsObj = pathmetrics(path,validator) creates an object based on the input navPath object and associated state validator for checking the path validity. The validator input sets the value of the StateValidator property.

Properties

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Path data structure, specified as a navPath object is the path whose metric is to be calculated.

Validator for states on path, specified as a validatorOccupancyMap object that validates the states and discretized motions based on the values in a 2-D occupancy map.

Object Functions

clearanceMinimum clearance of path
isPathValidDetermine if planned path is obstacle free
showVisualize path metrics in map environment
smoothnessSmoothness of path

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')

Introduced in R2019b