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isMotionValid

Check if path between states is valid

Description

example

[isValid,lastValid] = isMotionValid(validator,state1,state2) checks if the path between two states is valid by interpolating between states. The function also returns the last valid state along the path.

Examples

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This example shows how to validate paths through an evironment.

Load example maps. Use the simple map to create a binary occupancy map.

load exampleMaps.mat
map = occupancyMap(simpleMap);
show(map)

Figure contains an axes object. The axes object with title Occupancy Grid contains an object of type image.

Specify a coarse path through the map.

path = [2 2 pi/2; 10 15 0; 17 8 -pi/2];
hold on
plot(path(:,1),path(:,2),"--o")

Figure contains an axes object. The axes object with title Occupancy Grid contains 2 objects of type image, line.

Create a state validator using the stateSpaceSE2 definition. Specify the map and the distance for interpolating and validating path segments.

validator = validatorOccupancyMap(stateSpaceSE2);
validator.Map = map;
validator.ValidationDistance = 0.1;

Check the points of the path are valid states. All three points are in free space, so are considered valid.

isValid = isStateValid(validator,path)
isValid = 3x1 logical array

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Check the motion between each sequential path states. The isMotionValid function interpolates along the path between states. If a path segment is invalid, plot the last valid point along the path.

startStates = [path(1,:);path(2,:)];
endStates = [path(2,:);path(3,:)];
    for i = 1:2
        [isPathValid, lastValid] = isMotionValid(validator,startStates(i,:),endStates(i,:));
        if ~isPathValid
            plot(lastValid(1),lastValid(2),'or')
        end
    end
hold off

Figure contains an axes object. The axes object with title Occupancy Grid contains 3 objects of type image, line.

This example shows how to validate paths through an evironment.

Load example maps. Use the simple map to create a vehicle cost map. Specify an inflation raidus of 1 meter.

load exampleMaps.mat
map = vehicleCostmap(double(simpleMap));
map.CollisionChecker = inflationCollisionChecker("InflationRadius",1);
plot(map)

Figure contains an axes object. The axes object contains 2 objects of type image, patch. This object represents Inflated Areas.

Specify a coarse path through the map.

path = [3 3 pi/2; 8 15 0; 17 8 -pi/2];
hold on
plot(path(:,1),path(:,2),"--o")

Figure contains an axes object. The axes object contains 3 objects of type image, patch, line. This object represents Inflated Areas.

Create a state validator using the stateSpaceSE2 definition. Specify the map and the distance for interpolating and validating path segments.

validator = validatorVehicleCostmap(stateSpaceSE2);
validator.Map = map;
validator.ValidationDistance = 0.1;

Check the points of the path are valid states. All three points are in free space, so are considered valid.

isValid = isStateValid(validator,path)
isValid = 3x1 logical array

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   1

Check the motion between each sequential path states. The isMotionValid function interpolates along the path between states. If a path segment is invalid, plot the last valid point along the path.

startStates = [path(1,:);path(2,:)];
endStates = [path(2,:);path(3,:)];
    for i = 1:2
        [isPathValid, lastValid] = isMotionValid(validator,startStates(i,:),endStates(i,:));
        if ~isPathValid
            plot(lastValid(1),lastValid(2),'or')
        end
    end
hold off

Figure contains an axes object. The axes object contains 4 objects of type image, patch, line. This object represents Inflated Areas.

Create a 3-D occupancy map and associated state validator. Plan, validate, and visualize a path through the occupancy map.

Load and Assign Map to State Validator

Load a 3-D occupancy map of a city block into the workspace. Specify a threshold for which cells to consider as obstacle-free.

mapData = load('dMapCityBlock.mat');
omap = mapData.omap;
omap.FreeThreshold = 0.5;

Inflate the occupancy map to add a buffer zone for safe operation around the obstacles.

inflate(omap,1)

Create an SE(3) state space object with bounds for state variables.

ss = stateSpaceSE3([-20 220;
    -20 220;
    -10 100;
    inf inf;
    inf inf;
    inf inf;
    inf inf]);

Create a 3-D occupancy map state validator using the created state space.

sv = validatorOccupancyMap3D(ss);

Assign the occupancy map to the state validator object. Specify the sampling distance interval.

sv.Map = omap;
sv.ValidationDistance = 0.1;

Plan and Visualize Path

Create a path planner with increased maximum connection distance. Reduce the maximum number of iterations.

planner = plannerRRT(ss,sv);
planner.MaxConnectionDistance = 50;
planner.MaxIterations = 1000;

Create a user-defined evaluation function for determining whether the path reaches the goal. Specify the probability of choosing the goal state during sampling.

planner.GoalReachedFcn = @(~,x,y)(norm(x(1:3)-y(1:3))<5);
planner.GoalBias = 0.1;

Set the start and goal states.

start = [40 180 25 0.7 0.2 0 0.1];
goal = [150 33 35 0.3 0 0.1 0.6];

Plan a path using the specified start, goal, and planner.

[pthObj,solnInfo] = plan(planner,start,goal);

Check that the points of the path are valid states.

isValid = isStateValid(sv,pthObj.States)
isValid = 7x1 logical array

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Check that the motion between each sequential path state is valid.

isPathValid = zeros(size(pthObj.States,1)-1,1,'logical');
for i = 1:size(pthObj.States,1)-1
    [isPathValid(i),~] = isMotionValid(sv,pthObj.States(i,:),...
        pthObj.States(i+1,:));
end
isPathValid
isPathValid = 6x1 logical array

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Visualize the results.

show(omap)
hold on
scatter3(start(1,1),start(1,2),start(1,3),'g','filled') % draw start state
scatter3(goal(1,1),goal(1,2),goal(1,3),'r','filled')    % draw goal state
plot3(pthObj.States(:,1),pthObj.States(:,2),pthObj.States(:,3),...
    'r-','LineWidth',2) % draw path

Figure contains an axes object. The axes object with title Occupancy Map contains 4 objects of type patch, scatter, line.

Input Arguments

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State validator object, specified as an object of subclass of nav.StateValidator. These are the predefined state validator objects:

Initial state positions, specified as an n-element row vector or m-by-n matrix. n is the dimension of the state space specified in validator. m is the number of states to validate.

Data Types: single | double

Final state positions, specified as an n-element row vector or m-by-n matrix. n is the dimension of the state space specified in validator. m is the number of states to validate.

Data Types: single | double

Output Arguments

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Valid states, returned as an m-element logical column vector.

Data Types: logical

Final valid state along each path, returned as an n-element row vector or m-by-n matrix. n is the dimension of the state space specified in the state space property in validator. m is the number of paths validated. Each row contains the final valid state along the associated path.

Data Types: single | double

Introduced in R2019b