2DOF question and other things...help me...

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alsgud qor 2020-4-16

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/518418-2dof-question-and-other-things-help-me

评论： Ameer Hamza 2020-4-19

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Ameer Hamza 2020-4-16

This is a homework question. Show us what you have already tried. Also read this: https://www.mathworks.com/matlabcentral/answers/6200-tutorial-how-to-ask-a-question-on-answers-and-get-a-fast-answer

alsgud qor 2020-4-19

编辑：alsgud qor 2020-4-19

sorry this is what i ve done. I dunno how to put X, Y simultaneously...and there is error that

'HW5'function isn't defined like this...

======================================

function Homework5 =HW5(t,X)

m=10;

c=1000;

k=100000;

e=0.001;

w=100;

R=0.5;

X=R*cos(w*t);

Y=R*sin(w*t);

F1=m*e*w^2*cos(w*t);

F2=m*e*w^2*sin(w*t);

Homework5=[X(2); -c/m*X(2)-k/m*X(1)+F1/m];

==========================================

t=0:0.1:20;

>> X0=[0,0];

>> [t,X]=ode45(@HW5,t,X0);

and the error was 'Index exceeds array boundaries'

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Answer 1

Ameer Hamza 2020-4-19

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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/518418-2dof-question-and-other-things-help-me#answer_426873

在 MATLAB Online 中打开

Since you haven't posted the equation in mathematical form, so I can only guess. The following code will not give any error, but I am not sure if it is what you want?

t=0:0.1:20;
X0=[0,0];
[t,X]=ode45(@HW5,t,X0);
function Homework5 =HW5(t, X)
m=10;
c=1000;
k=100000;
e=0.001;
w=100;
R=0.5;
F1=m*e*w^2*cos(w*t);
Homework5=[X(2); -c/m*X(2)-k/m*X(1)+F1/m];
end

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alsgud qor 2020-4-19

在 MATLAB Online 中打开

mx''+cx'+kx=mew^2coswt

my''+cy'+ky=mew^2sinwt

and this is my current progress...plz check this is right or not...

=============================

function Xdot =HW5(t,X)
m=10;
c=1000;
k=100000;
e=0.001;
w_rpm = 100; % 100, 1000, 2000 
w=w_rpm*2*pi/60;
Fh=m*e*w^2*cos(w*t); % horizontal
Fv=m*e*w^2*sin(w*t); % vertical
% m x'' + c x' + k x = Fh (horizontal)
% x'' = -c/m x' -k/m x + Fh/m
% x1' = x2
% x2' = -c/m x2 -k/m x1 + Fh/m
% m y'' + c y' + k y = Fv (vertical)
% y'' = -c/m y' -k/m y + Fh/m
% y1' = y2
% y2' = -c/m y2 -k/m y1 + Fh/m
% X = [x1 ; x2 ; y1 ; y2] 
Xdot=[X(2);
-c/m*X(2)-k/m*X(1)+Fh/m;
X(4);
-c/m*X(4)-k/m*X(3)+Fv/m];
end
======================
figure, plot(X(:,1)*1e3,X(:,3)*1e3)
grid on
xlabel('x, mm')
ylabel('y, mm')
pbaspect([1 1 1])
legend('2000 rpm')

Ameer Hamza 2020-4-19

Considering the ODEs you wrote, the function appears to be correct. However, the ODEs seems to be independent of each other? One would expect that for such a system, the system of ODEs should be coupled.

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