在使用ode45函数​求解微分方程出错，无​法执行赋值，因为左侧​和右侧的元素数目不同

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clear

global EI Fx Fy

d=2;

I=pi*d^4/64;

E=200e3;

EI=E*I;

L=1000;

n=100;

Fcr=pi^2*EI/L^2;

Fx=0.99*Fcr;

k1=4*EI/L;

k2=3.5*EI/L;

thita1=pi/5;

% thita20=-thita1*k1/k2;

% Fy=-(k1*thita1+k2*thita20)/L;

% x0=[thita1,k1*thita1/EI];

x1(1)=0;

y1(1)=0;

ds=L/n;

m=10;

for j=1:m

err=0.1;

num=1;

x0=[thita1*j/m, k1*thita1*j/m/EI]

Y(1,:)=x0;

x(1)=0;

Fx=0.99*Fcr;

Fy=0;

while err>0.005 && num<100

x01=x0;

for i=2:n+1

x(i)=x(i-1)+ds;

[Ti,Yi] = ode45(@bend_columnB,[x(i-1) x(i)],x01);

T(i)=Ti(end);

Y(i,:)=Yi(end,:);

x01=Y(i,:);

x1(i)=x1(i-1)+ds*cos(Y(i,1));

y1(i)=y1(i-1)+ds*sin(Y(i,1));

end

err=abs(y1(end));

thita2=Y(end,1);

Fx=Fx+y1(end)*0.025/j*Fcr;

Fy=-(k1*thita1*j/m+k2*thita2)/L;

num=num+1;

end

num_T(j)=num;

dl(j)=L-x1(end);

FFx(j)=Fx;

FFy(j)=Fy;

figure(2)

plot(x1,y1);hold on

end

figure(1)

plotyy(x,Y(:,1),x,Y(:,2));

% figure(2)

% plot(x1,y1);

figure(3)

plot(dl,FFx);hold on

function dy=bend_columnB(x,y)

global k dth_ds20%k=(F/EI)^0.5

dy = zeros(2,1); % a column vector

dy(1)=y(2);

%dy(2)=-k^2*y(1);%小挠度理论

dy(2)=-k^2*sin(y(1))+dth_ds20;%大挠度理论

Answer 1

[埃博拉酱]

这种简单问题断点调试一下就行了