Laplace with Heaviside step function solving with ode45

Question

Tashanda Rayne 2023-11-28

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2052847-laplace-with-heaviside-step-function-solving-with-ode45

评论： Tashanda Rayne 2023-11-28

I dont understand why I keep getting an error, can you please explain to me why and how I can fix this?

syms s t Y
f = heaviside(t-1)- heaviside(t-2);
X = laplace(f);
Sol = X ./(s^2+3*s+2);
sol = symfun(ilaplace(Sol),t);
pretty(sol)
                 / exp(2 - 2 t)                1 \                    / exp(4 - 2 t)                1 \
heaviside(t - 1) | ------------ - exp(1 - t) + - | - heaviside(t - 2) | ------------ - exp(2 - t) + - |
                 \       2                     2 /                    \       2                     2 /
tspan = [0 5];
ic = [0 0];
fn = @(t,Y) [Y(2); (heaviside(t-1)- heaviside(t-2) - 3*Y(2) - 2* Y(1))];   
[t,Y] = ode45(fn,tspan,ic);
Index exceeds the number of array elements. Index must not exceed 1.

Error in indexing (line 968)
            R_tilde = builtin('subsref',L_tilde,Idx);

Error in solution>@(t,y)[Y(2);(u-Y(3)-3*Y(2)-2*Y(1))] (line 12)
fn = @(t,y) [Y(2); (u - Y(3) - 3*Y(2) - 2* Y(1))];   

Error in odearguments (line 92)
f0 = ode(t0,y0,args{:});   % ODE15I sets args{1} to yp0.

Error in ode45 (line 104)
    odearguments(odeIsFuncHandle,odeTreatAsMFile, solver_name, ode, tspan, y0, options, varargin);
hold on
plot(t,y(:,1))
fplot(sol, [0 5])
grid on 
xlabel('x')
ylabel('y')
legend('Ode45' ,'Solved' )
hold off 