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environment

Environmental inputs for UAV

Description

example

envStruct = environment(uavGuidanceModel) returns a structure that captures all the relevant environmental variables for the specified UAV guidance model. Use this function to ensure you have the proper fields for your environmental parameters. Use the environmental inputs as an input to the derivative function to get the state time-derivative of the UAV.

Examples

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This example shows how to use the multirotor guidance model to simulate the change in state of a UAV due to a command input.

Create the multirotor guidance model.

model = multirotor;

Create a state structure. Specify the location in world coordinates.

s = state(model);
s(1:3) = [3;2;1];

Specify a control command, u, that specified the roll and thrust of the multirotor.

u = control(model);
u.Roll = pi/12;
u.Thrust = 1;

Create a default environment without wind.

e = environment(model);

Compute the time derivative of the state given the current state, control command, and environment.

sdot = derivative(model,s,u,e);

Simulate the UAV state using ode45 integration. The y field outputs the multirotor UAV states as a 13-by-n matrix.

simOut = ode45(@(~,x)derivative(model,x,u,e), [0 3], s);
size(simOut.y)
ans = 1×2

          13        3536

Plot the change in roll angle based on the simulation output. The roll angle (the X Euler angle) is the 9th row of the simOut.y output.

plot(simOut.y(9,:))

Figure contains an axes object. The axes object contains an object of type line.

Plot the change in the Y and Z positions. With the specified thrust and roll angle, the multirotor should fly over and lose some altitude. A positive value for Z is expected as positive Z is down.

figure
plot(simOut.y(2,:));
hold on
plot(simOut.y(3,:));
legend('Y-position','Z-position')
hold off

Figure contains an axes object. The axes object contains 2 objects of type line. These objects represent Y-position, Z-position.

You can also plot the multirotor trajectory using plotTransforms. Create the translation and rotation vectors from the simulated state. Downsample (every 300th element) and transpose the simOut elements, and convert the Euler angles to quaternions. Specify the mesh as the multirotor.stl file and the positive Z-direction as "down". The displayed view shows the UAV translating in the Y-direction and losing altitude.

translations = simOut.y(1:3,1:300:end)'; % xyz position
rotations = eul2quat(simOut.y(7:9,1:300:end)'); % ZYX Euler
plotTransforms(translations,rotations,...
    'MeshFilePath','multirotor.stl','InertialZDirection',"down")
view([90.00 -0.60])

Figure contains an axes object. The axes object contains 48 objects of type patch, line.

This example shows how to use the fixedwing guidance model to simulate the change in state of a UAV due to a command input.

Create the fixed-wing guidance model.

model = fixedwing;

Set the air speed of the vehicle by modifying the structure from the state function.

s = state(model);
s(4) = 5; % 5 m/s

Specify a control command, u, that maintains the air speed and gives a roll angle of pi/12.

u = control(model);
u.RollAngle = pi/12;
u.AirSpeed = 5;

Create a default environment without wind.

e = environment(model);

Compute the time derivative of the state given the current state, control command, and environment.

sdot = derivative(model,s,u,e);

Simulate the UAV state using ode45 integration. The y field outputs the fixed-wing UAV states based on this simulation.

simOut = ode45(@(~,x)derivative(model,x,u,e), [0 50], s);
size(simOut.y)
ans = 1×2

     8   904

Plot the change in roll angle based on the simulation output. The roll angle is the 7th row of the simOut.y output.

plot(simOut.y(7,:))

Figure contains an axes object. The axes object contains an object of type line.

You can also plot the fixed-wing trajectory using plotTransforms. Create the translation and rotation vectors from the simulated state. Downsample (every 30th element) and transpose the simOut elements, and convert the Euler angles to quaternions. Specify the mesh as the fixedwing.stl file and the positive Z-direction as "down". The displayed view shows the UAV making a constant turn based on the constant roll angle.

downsample = 1:30:size(simOut.y,2);
translations = simOut.y(1:3,downsample)'; % xyz-position
rotations = eul2quat([simOut.y(5,downsample)',simOut.y(6,downsample)',simOut.y(7,downsample)']); % ZYX Euler
plotTransforms(translations,rotations,...
    'MeshFilePath','fixedwing.stl','InertialZDirection',"down")
hold on
plot3(simOut.y(1,:),-simOut.y(2,:),simOut.y(3,:),'--b') % full path
xlim([-10.0 10.0])
ylim([-20.0 5.0])
zlim([-0.5 4.00])
view([-45 90])
hold off

Figure contains an axes object. The axes object contains 125 objects of type patch, line.

Input Arguments

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UAV guidance model, specified as a fixedwing or multirotor object.

Output Arguments

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Environmental input parameters, returned as a structure.

For fixed-wing UAVs, the fields of the structure are WindNorth, WindEast,WindDown, and Gravity. Wind speeds are in meters per second and negative speeds point in the opposite direction. Gravity is in meters per second squared (default 9.81).

For multirotor UAVs, the only element of the structure is Gravity (default 9.81) in meters per second.

Extended Capabilities

C/C++ Code Generation
Generate C and C++ code using MATLAB® Coder™.

Introduced in R2018b