navPath

Planned path

Description

The navPath object stores paths that are typically created by geometric path planners. Path points are stored as states in an associated state space.

Creation

Syntax

path = navPath

path = navPath(space)

path = navPath(space,states)

Description

path = navPath creates a path object, path, using the SE(2) state space with default settings.

path = navPath(space) creates a path object with state space specified by space. The space input also sets the value of the StateSpace property.

path = navPath(space,states) allows you to initialize the path with state samples given by states. Specify states as a matrix of state samples. States that are outside of the StateBounds of the state space object are reduced to the bounds. The states input also sets the value of the States property.

Properties

StateSpace — State space for path

stateSpaceSE2 (default) | state space object

State space for the path, specified as a state space object. Each state in the path is a sample from the specified state space. You can use objects such as stateSpaceSE2, stateSpaceDubins, stateSpaceReedsShepp, or stateSpaceSE3 as a state space object. You can also customize a state space object using the nav.StateSpace object.

States — States of path

zeros(0,StateSpace.NumStateVariables) (default) | real-valued M-by-N matrix

States of the path, specified as a real-valued M-by-N matrix. M is the number of states in the path, and N is the dimension of each state. You can only set this property during object creation or using the append function.

Example: [0 0 0; 1 1 0; 2 2 0]

Example: [0 0 0 1 0 0 0; 1 1 1 1 0 0 0; 2 2 1 1 0 0 0]

Data Types: double

NumStates — Number of state samples in path

0 (default) | nonnegative integer

This property is read-only.

Number of state samples in the path, specified as a nonnegative integer. The number is the same as the number of rows of the state matrix specified in the States property.

Data Types: double

Object Functions

append	Add states to end of path
copy	Create copy of path object
interpolate	Interpolate points along path
pathLength	Length of path

Examples

Create navPath Based on Multiple Waypoints

Create a navPath object based on multiple waypoints in a Dubins space.

dubinsSpace = stateSpaceDubins([0 25; 0 25; -pi pi])

dubinsSpace = 
  stateSpaceDubins with properties:

   SE2 Properties
                 Name: 'SE2 Dubins'
          StateBounds: [3x2 double]
    NumStateVariables: 3

   Dubins Vehicle Properties
     MinTurningRadius: 1

pathobj = navPath(dubinsSpace)

pathobj = 
  navPath with properties:

    StateSpace: [1x1 stateSpaceDubins]
        States: [0x3 double]
     NumStates: 0

waypoints = [8 10 pi/2;
             7 14 pi/4;
             10 17 pi/2;
             10 10 -pi];
append(pathobj,waypoints)

Interpolate that path so that it contains exactly 250 points.

interpolate(pathobj,250)

Visualize the interpolated path and the original waypoints.

figure
grid on
axis equal
hold on
plot(pathobj.States(:,1),pathobj.States(:,2),".b")
plot(waypoints(:,1),waypoints(:,2),"*r","MarkerSize",10)

Calculate length of path.

len = pathLength(pathobj);
disp("Path length = " + num2str(len))

Path length = 19.4722

Create navPath Based on Multiple Waypoints in SE(3) State Space

Load a 3-D occupancy map of a city block into the workspace. Specify the threshold to consider cells 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([0 220;0 220;0 100;inf inf;inf inf;inf inf;inf inf]);

Create a navPath object based on multiple waypoints in an SE(3) state space.

path = navPath(ss);
waypoints = [40 180 15 0.7 0.2 0 0.1;
             55 120 20 0.6 0.2 0 0.1;
             100 100 25 0.5 0.2 0 0.1;
             130 90 30 0.4 0 0.1 0.6;
             150 33 35 0.3 0 0.1 0.6];
append(path,waypoints)

Interpolate that path so that it contains exactly 250 points.

interpolate(path,250)

Visualize the interpolated path and the original waypoints.

show(omap)
axis equal
view([-10 55])
hold on
% Start state
scatter3(waypoints(1,1),waypoints(1,2),waypoints(1,3),"g","filled")
% Goal state
scatter3(waypoints(end,1),waypoints(end,2),waypoints(end,3),"r","filled")
% Intermediate waypoints
scatter3(waypoints(2:end-1,1),waypoints(2:end-1,2), ...
         waypoints(2:end-1,3),"y","filled")
% Path
plot3(path.States(:,1),path.States(:,2),path.States(:,3), ...
      "r-",LineWidth=2)

Calculate length of path.

len = pathLength(path);
disp("Path length = " + num2str(len))

Path length = 204.1797

Version History

Introduced in R2019b