Solve Differential Equation with initial conditions and function

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SamuLibero
SamuLibero 2023-3-14
回答： Alan Stevens 2023-3-14
Hello Everyone,
I have this differential equation: I have defined the function M(x) in the following way:
function M = Moment(x)
a = 800; %mm
b = 200; %mm
L = 1000; %mm
F = 1000; %N
if x<a
V = F*b/L;
M = V.*x;
elseif x >= a
M = F*a*(1-(x/L));
end
end
to solve the differential equation I've defined the following ode function based on previous ones:
xspan = 0:0.0002:1000;
y0 = [0 0];
[x,results] = ode45(@func3,xspan,y0);
function [dy] = func3(x,y)
E = 70000; %N/mm2
I = 32000; %mm4
y1 = y(1);
y2 = y(2);
dy1 = y2;
dy2 = -Moment(x)/(E*I);
dy = [dy1; dy2];
end
The main problem I'm trying to solve is that I have the boundary condition for the displacement y(0) = 0 and y(1000) = 0. I'm able to assign the first BD (i think), but i don't know how to assign the second one, since the solver refears to the function "Moment".
Thank you in advance!

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回答（1 个）

Alan Stevens
Alan Stevens 2023-3-14
Try modifying your if statement in Moment. Something like
if x<a
V =...;
M = ...;
elseif x>=a && x<L
M = ...
else
M = 0;
end

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