ode45 solve and taking current state as input

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WANYI ZHANG 2019-4-24

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https://ww2.mathworks.cn/matlabcentral/answers/458200-ode45-solve-and-taking-current-state-as-input

评论： Jan 2019-4-24

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Can anyone help me how to fix this problem?

my questions are blow:

this is my function to be solved:

function dx = CSmacro_derive(x,fluid_params,dQ,dV,h_in,dm_in,dm_out)
dx=zeros(3,1);
v=x(1)/x(2);
h=fluid_params.h;                                               
P=fluid_params.P;                                               
dx(1)=dV;
dx(2)=dm_in-dm_out;
dx(3)=(1/(x(2)*fluid_params.dudT))*...
        (dQ+((h_in-h)*dm_in)+(P+fluid_params.dudv)*(v*dx(2)-dx(1)));
end

This my main script:

t=linspace(0,10,10);
dV =0.1*sin(t);
dm_in=0.5;
dm_out=0;
% Initial condition
V=0.3326;
m=1;
T=15 + Kel;
x0=[V;m;T];
% Upstream refrigerant
v_in = 0.3326;
T_in = 15 + Kel;
fluid_in = refprop(v_in,T_in,r410a);
h_in=fluid_in.h;
[~,~,dQ] = convecCool(theta_a,x(3),convec_params);
fluid_params = CSmacro_props(x,r410a);
%this is my question.
%how can I take the current x value as my input to these two functions.
for i=length(t)
  dx = @(t,x) CSmacro_derive(x,fluid_params,dQ,dV(i),h_in,dm_in,dm_out);
  opts=odeset('RelTol',1e-6);
  [t,x] = ode45(dx,t,x0,opts);
end