How do I go about plotting points from ODE45 with this?
2 views (last 30 days)
Show older comments
I have been trying to use ODE45 to solve the linearised model, my aim is to plot values of y and x displacement but the code does not seem to churn out any right answers. The attached images are the equations I am given to work around with. Are my ODE45 parameters wrong? Any advice would help a lot!
my function is as follows
function dydx = odefcn(x, y, a, v)
dydx = zeros(2, 1);
dydx(1) = y(2);
dydx(2) = a/v^2;
%========================= MAIN CODE ===========================%
% Get launch angle (theta) from user, then get initial x and y coordinates
% Constants are VELOCITY (v), N, DESIGNATED TIME (Td)
% Variables are x and y
% LOS, a, L are always changing, so need to INCLUDE THEM IN A LOOP
% Output will be x and y, ALSO ALWAYS CHANGING
%======================= Get input from user =============================%
theta0 = input('Please input launch angle in degrees: ');
x0 = input('Please enter initial x coordinates: ');
y0 = input('Please enter initial y coordinates: ');
%=========================== Constants ===================================%
v = 300;
N = 3; % Proportionality constant
Td = 40; % designated impact time
targetx= 50; targety = 50; % set targetcoordinates
Rgo_x = targetx - x0;
Rgo_y = targety - y0;
theta = theta0;
xspan = [x0 targetx];
yspan = [y0 targety];
IC = [0 theta0];
x=x0; y=y0;
while Rgo_y ~= 0 & Rgo_x ~= 0
Rgo = sqrt(Rgo_x^2 + Rgo_y^2);
LOS = -(Rgo_y/(Rgo^2));
Tgo = (1+ (theta-acosd(Rgo_x/Rgo))/10)*(Rgo/v);
a = N*v*LOS - (60*v^5*(Td-Tgo))/(N*v*LOS*(Rgo^3));
theta = a*(Rgo_x)/v^2 + theta;
[x, y] = ode45(@(x, y)odefcn(x, y, a, v), xspan, yspan, IC);
Rgo_x = targetx - x;
Rgo_y = targety - y;
end
%================ Plot x and Y values wrt to angle changes ===============%
figure
grid on
plot(x, y, 'o')
xlabel('x displacement (m)');
ylabel('y displacement (m)');
0 Comments
Answers (1)
J. Alex Lee
on 5 Aug 2020
yes, your odefun looks wrong, it looks like you did not correctly apply matrix algebra to get the separate equations from your matrix form.
And why aren't there 2 a's, aB and aF?
2 Comments
J. Alex Lee
on 5 Aug 2020
Edited: J. Alex Lee
on 5 Aug 2020
i apologize, it must have been early in the morning, your odefcn does look ok.
See Also
Categories
Find more on Ordinary Differential Equations in Help Center and File Exchange
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!