how to solve 3dof point mass equations of motion of flight vehicle

22 views (last 30 days)
i have to solve 6 differential equations of 3dof system of flight vehicle abd plot them. i have run a code but i am not getting appropriate results.
plzz anyone help me how to do that.
clear all;close all;clc;
t = 0:0.1:15;
y0= [0.5 0.5 0.5 0.5 0.5 0.5];
[tsol ysol] = ode45(@threedof, t, y0);
velocity = ysol(:,1);
yaw_angle = ysol(:,2);
pitch_angle = ysol(:,3);
x = ysol(:,4);
y = ysol(:,5);
z = ysol(:,6);
figure();
plot(tsol,velocity,'or',tsol,yaw_angle,'--k',tsol,pitch_angle,'--b',tsol,x,'oy',tsol,y,'ok',tsol,z,'og')
function solveode = threedof(t,y);
T = 2000; m = 200; g = 9.81; gamma = 10*pi/180; V=100; phi = (10*pi/180); %Vvec= [V;0;0];
D = 00; S=00; L = 0000;
fval(1)=((T/m)-(D/m)-(g*sin(gamma)));
fval(2)=((L/m*V)-(g*cos(gamma)/V));
favl(3)=(S/(m*V*cos(gamma)));
fval(4)=V*cos(gamma)*cos(phi);
fval(5)=V*cos(gamma)*sin(phi);
fval(6)=V*sin(gamma);
solveode = [fval(1);fval(2);favl(3);fval(4);fval(5);fval(6)];
end

Answers (2)

Bjorn Gustavsson
Bjorn Gustavsson on 13 Jun 2022
A three-degrees-of-freedom dynamic system in three spatial coordinates doesn't have yaw and pitch degrees of freedom. It is effectively modeling the trajectory of a particle. As such your ODE-function looks dodgy. My standard way of writing equations-of-motion are, something like:
function d2ydt2dydt = threedof(t,y)
T = 2000; % describe units...
m = 200;
g = 9.81;
gamma = 10*pi/180;
phi = (10*pi/180); %Vvec= [V;0;0];
D = 0; % Drag?
S = 0; % Some other parameter?
L = 0; % Lift
V = y(1:3); % I prefer to order the state-vector as [r;v], but this is purely convention
T = T*V/norm(V); % Just setting the thrust parallel to V, adjust to your case.
F_drag = -D/m*V(:);
F_thrust = T(:)/m;
% Calculate the other forces on your particle too
dydt = V; %
d2ydt2 = [F_thrust + F_drag - g*[0 0 1]]; % add the forces together
d2ydt2dydt = [d2ydt2; dydt];
HTH

SUBASH
SUBASH on 4 Apr 2023
is it possible to share the "3dof point mass equations of motion of flight vehicle" in state space format?
Thanks

Categories

Find more on Programming in Help Center and File Exchange

Products


Release

R2020b

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!