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Generate Random 3-D Occupancy Map for UAV Motion Planning

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Open Live Script

This example shows how to generate a random 3-D occupancy map by automatically adding the desired number of obstacles of varying dimensions at random positions on the map. You can then use the generated map for UAV motion planning using algorithms like RRT, RRT* and Hybrid A*.

Choose a random number generator and set the seed of the generator using the rng function for repeatability of the result. Change these values to obtain a different 3-D occupancy map. This step is optional. Use the seed and generator given below to reproduce the map generated in this example.

rng(7,"twister");

Create an empty 3-D occupancy map. Specify the maximum width and maximum length of the map as desired. In this example, the map has an area of 200-by-200 square meters.

omap3D =  occupancyMap3D;
mapWidth = 200;
mapLength = 200;

Specify the number of obstacles to be added.

numberOfObstacles = 10;

Add the obstacles one after another using a while loop.

  1. Generate the position and dimensions of the obstacle randomly using the randi function. Make sure the obstacle does not cross the map's boundaries.

  2. Obtain the 3D grid coordinates of the obstacle using the meshgrid function.

  3. Use the checkOccupancy (Navigation Toolbox) function to check if the obstacle intersects any other previously added obstacle. If it does, go to step 1. If it does not, move on to the next step.

  4. Use the setOccupancy (Navigation Toolbox) function to set the occupancy values of the obstacle's location as 1.

obstacleNumber = 1;
while obstacleNumber <= numberOfObstacles
    width = randi([1 50],1);                 % The largest integer in the sample intervals for obtaining width, length and height                                                     
    length = randi([1 50],1);                % can be changed as necessary to create different occupancy maps.
    height = randi([1 150],1);
    xPosition = randi([0 mapWidth-width],1);
    yPosition = randi([0 mapLength-length],1);
    
    [xObstacle,yObstacle,zObstacle] = meshgrid(xPosition:xPosition+width,yPosition:yPosition+length,0:height);
    xyzObstacles = [xObstacle(:) yObstacle(:) zObstacle(:)];
    
    checkIntersection = false;
    for i = 1:size(xyzObstacles,1)
        if checkOccupancy(omap3D,xyzObstacles(i,:)) == 1
            checkIntersection = true;
            break
        end
    end
    if checkIntersection
        continue
    end
    
    setOccupancy(omap3D,xyzObstacles,1)
    
    obstacleNumber = obstacleNumber + 1;
end

Because a UAV must not collide with the ground during the flight, consider the ground also as an obstacle. So, set the occupancy of the ground plane (x-y plane) as 1, indicating that it is an obstacle.

[xGround,yGround,zGround] = meshgrid(0:mapWidth,0:mapLength,0);
xyzGround = [xGround(:) yGround(:) zGround(:)];
setOccupancy(omap3D,xyzGround,1)

Display the final occupancy map.

figure("Name","3D Occupancy Map")
show(omap3D)

Figure 3D Occupancy Map contains an axes object. The axes object with title Occupancy Map, xlabel X [meters], ylabel Y [meters] contains an object of type patch.

For an example on how to use the created occupancy map, see Motion Planning with RRT for Fixed-Wing UAV.

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