# I need to learn how to use this code. I'm trying to implement it in MATLAB. I'm having trouble getting the plane to assume a higher altitude.

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DJ V on 31 May 2024
I'm having trouble getting the plane to assume a higher altitude. Can anyone please look for the comment in the top section that is associated with assigning a variable a value, remove the comment, and see what the software does? Thank you. I have never dealt with "handles" before, and I need a quick course on the subject.
pn=0;
pe=0;
pd=0;
phi=0;
theta=0;
psi=0;
handle=[];
%Simulation parameters
dpn=0.5; %Change in position.
dpsi=0.01; %Change in yaw angle.
simlength=150;%Number of Sim Steps
%Draw and update the plane's position.
for k = 1:simlength
pn = pn+dpn;
pe = pe+dpn;
%THE CODE THAT PRODUCES A PROBLEM IS BELOW
%pd = pd +.1;
psi = psi+dpsi;
%Draw or update the plane.
handle = drawPlaneBody(pn,pe,pd,phi,theta,psi,handle);
pause(0.1); %Pause to visualize the movement
end
function handle = drawPlaneBody(pn,pe,pd,phi,theta,psi,handle)
%define points on plane in local NED coordintates
NED = airplanepoints;
%rotate plane by (phi; theta; psi)
NED = rotate(NED, phi, theta, psi);
%translate plane to [pn; pe; pd]
NED = translate(NED, pn, pe, pd);
%transform vertices from NED to XYZ
R = [...
0, 1, 0;...
1, 0 , 0;...
0, 0, -1;...
];
XYZ = R* NED';
%plot plane
if isempty(handle)
handle = plot3(XYZ(1,:),XYZ(2,:),XYZ(3,:),'b');
xlim([-100 100]);
ylim([-100 100]);
zlim([0 100]);
grid on;%show grid
xlabel('X');ylabel('Y');zlabel('Z');%label axes
else
set(handle, 'XData', XYZ(1,:), 'YData',XYZ(2,:), 'ZData',XYZ(3,:));
drawnow
end
end
function XYZ = airplanepoints
%define points on the aircraft in local NED
XYZ = [...
0 0 0;%point1
-2 1 1;%point2
-2 1 -1;%point3
0 0 0;%point1
-2 -1 1;%point4
-2 -1 -1;%point5
0 0 0;%point1
-2 1 1;%point2
-2 -1 1;%point4
0 0 0;%point1
-2 1 -1;%point3
-2 -1 -1;%point5
0 0 0;%point1
-2 1 1;%point2
-18 0 0;%point6
-2 1 -1;%point3
-18 0 0;%point6
-2 -1 -1;%point5
-18 0 0;%point6
-2 -1 1;%point4
-18 0 0;%point6
-2 1 1;%point2
0 0 0;%point1
-5 0 0;%point7
-5 -10 0;%point8
-8 -10 0;%point9
-8 10 0;%point10
-5 10 0;%point11
-5 0 0;%point7
-15.5 0 0;%point12
-15.5 2 0;%point13
-17.5 2 0;%point14
-17.5 -2 0;%point15
-15.5 -2 0;%point16
-15.5 0 0;%point12
-18 0 0;%point6
-18 0 -3;%point17
-15.5 0 0;%point15
-18 0 0;%point16
];
end
function XYZ=rotate(XYZ,phi,theta,psi)
%define rotation matrix
R_roll = [
1, 0, 0;
0, cos(phi), -sin(phi);
0, sin(phi), cos(phi)];
R_pitch = [
cos(theta), 0, sin(theta);
0, 1, 0;
-sin(theta), 0, cos(theta)];
R_yaw = [
cos(psi), -sin(psi), 0;
sin(psi), cos(psi), 0;
0, 0, 1];
R = R_roll*R_pitch*R_yaw;
%rotate vertices
XYZ =R*XYZ';
XYZ = XYZ';
end
function XYZ = translate(XYZ, pn, pe, pd)
XYZ = XYZ' + repmat([pn;pe;pd],1,size(XYZ,1));
XYZ=XYZ';
end

Manikanta Aditya on 1 Jun 2024
The issue you’re facing is due to the commented line of code that changes the altitude (pd) of the plane. If you uncomment the line pd = pd +.1;, the plane will start to change its altitude.
Here’s the code:
pn=0;
pe=0;
pd=0;
phi=0;
theta=0;
psi=0;
handle=[];
%Simulation parameters
dpn=0.5; %Change in position.
dpsi=0.01; %Change in yaw angle.
simlength=150;%Number of Sim Steps
%Draw and update the plane's position.
for k = 1:simlength
pn = pn+dpn;
pe = pe+dpn;
pd = pd +.1; %Uncommented this line
psi = psi+dpsi;
%Draw or update the plane.
handle = drawPlaneBody(pn,pe,pd,phi,theta,psi,handle);
pause(0.1); %Pause to visualize the movement
end
% Rest of the code remains the same
As for the “handles”, in MATLAB, a handle is a variable that you can use to access graphics objects (like plots, lines, surfaces, etc.). In your code, handle is used to store the handle of the plot created by plot3 function.
This handle is then used to update the plot in subsequent iterations of the loop. If handle is empty (i.e., the plot has not been created yet), a new plot is created. Otherwise, the existing plot is updated with new data. This is done using the set function.
Hope this helps.
##### 3 CommentsShow 1 older commentHide 1 older comment
DJ V on 1 Jun 2024
Moved: Stephen23 on 1 Jun 2024
The new code that works.
pn=0;
pe=0;
pd=0;
phi=0;
theta=0;
psi=0;
handle=[];
%Simulation parameters
dpn=0.5; %Change in position.
dpsi=0.01; %Change in yaw angle.
simlength=150;%Number of Sim Steps
%Draw and update the plane's position.
for k = 1:simlength
pn = pn+dpn;
pe = pe+dpn;
%THE CODE THAT PRODUCES A PROBLEM IS BELOW
pd = pd -1;
psi = psi+dpsi;
%Draw or update the plane.
handle = drawPlaneBody(pn,pe,pd,phi,theta,psi,handle);
pause(0.1); %Pause to visualize the movement
end
Manikanta Aditya on 1 Jun 2024
Thanks for sharing @DJ V!

R2019b

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