How to plot phase plane in MATLAB?

Question

Alex 2014-2-19

0
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https://ww2.mathworks.cn/matlabcentral/answers/116782-how-to-plot-phase-plane-in-matlab

回答： Elistin 2022-10-24

采纳的回答： Mischa Kim

Hi I have two equations here, and I wonder that how do you plot them as a phase plane.

du/dt = wu^2 - Bu dw/dt = A - w - wu^2

and A,B both are constants

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Answer 1

Mischa Kim 2014-2-23

12
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https://ww2.mathworks.cn/matlabcentral/answers/116782-how-to-plot-phase-plane-in-matlab#answer_125728

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Alex, assuming that you are talking about a u-w (position-velocity, sort of) phase plot, here you go. Essentially, you only need to solve the differential equations and then plot the result.

function my_phase()
[~,X] = ode45(@EOM,[0 50],[1 1]);
u = X(:,1);
w = X(:,2);
plot(u,w)
xlabel('u')
ylabel('w')
grid
end
function dX = EOM(t, y)
dX = zeros(2,1);
u  = y(1);
w  = y(2);
A  = 1;
B  = 1;
dX = [w*u^2 - B*u;...
      A - w - w*u^2];
end