can you please help me solve this diffetential equation system?

I need to solve a differential system and I coded in this way . I doesn't seem to work. I want to solve it only for t [0,4]. how can i do that?

syms x1(t) x2(t) x3(t) x4(t) x5(t) x6(t)

b=4.2030*10^5

m=1.0508*10^6

k=3.5025*10^9

A = [-2*b/(3*m) b/(3*m) 0 1/(3*m) -1/(3*m) 0 ;

b/(2*m) -2*b/(2*m) b/(2*m) 0 1/(3*m) -1/(3*m) ;

0 b/m -b/m 0 0 1/m ;

-k 0 0 0 0 0 ;

k -k 0 0 0 0 ;

0 k -k 0 0 0];

B = [-b/(3*m)*(1.8747*log(t)+8.6905);

0;

0;

-k*(1.8747*log(t)+8.6905);

0;

0;];

Y = [x1; x2; x3; x4; x5; x6];

odes = diff(Y) == A*Y + B

C = Y(0) == [0;0;0;0;0;0];

[x1Sol(t), x2Sol(t), x3Sol(t), x4Sol(t), x5Sol(t), x6Sol(t)] = dsolve(odes,C);

x1Sol(t) = simplify(x1Sol(t))

x2Sol(t) = simplify(x2Sol(t))

x3Sol(t) = simplify(x3Sol(t))

x4Sol(t) = simplify(x4Sol(t))

x5Sol(t) = simplify(x5Sol(t))

x6Sol(t) = simplify(x6Sol(t))

Answer 1

[Alan Stevens]

You have log(t) in the definition of B. This causes problems at t = 0.

[SOUGLES STAMATIS]

okey, how can set the t value from 0.1 to 4?

[Alan Stevens]

Like this

x0 = [0;0;0;0;0;0];
tspan = [0.01 4];
[t, x] = ode45(@bc, tspan, x0);

plot(t,x),grid

function xdot = bc(t,x)

    b=4.2030*10^5;
    m=1.0508*10^6;
    k=3.5025*10^9;
    A = [-2*b/(3*m) b/(3*m) 0 1/(3*m) -1/(3*m) 0 ;
         b/(2*m) -2*b/(2*m) b/(2*m) 0 1/(3*m) -1/(3*m) ;
         0 b/m -b/m 0 0 1/m ;
         -k 0 0 0 0 0 ;
         k -k 0 0 0 0 ;
         0 k -k 0 0 0];
    B = [-b/(3*m)*(1.8747*log(t)+8.6905);
        0;
        0;
        -k*(1.8747*log(t)+8.6905);
        0;
        0;];
    
    xdot = A*x + B;

end

You might need to plot the different x's on separate graphs to see them all properly.

Note that the results will be somewhat different depending on your starting value for t.