environment

Environmental inputs for UAV

Since R2018b

Syntax

envStruct = environment(uavGuidanceModel)

Description

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

Simulate A Multirotor Control Command

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,:))

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

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])

Simulate A Fixed-Wing Control Command

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,:))

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

Input Arguments

uavGuidanceModel — UAV guidance model

fixedwing object | multirotor object

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

Output Arguments

envStruct — Environmental input parameters

structure

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™.

Version History

Introduced in R2018b