How do I go about plotting points from ODE45 with this?
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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!
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/341665/image.png)
![](https://www.mathworks.com/matlabcentral/answers/uploaded_files/341668/image.png)
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)');
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Antworten (1)
J. Alex Lee
am 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 Kommentare
J. Alex Lee
am 5 Aug. 2020
Bearbeitet: J. Alex Lee
am 5 Aug. 2020
i apologize, it must have been early in the morning, your odefcn does look ok.
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