'MY_ODE_WITHOUT_TLD returns a vector of length 2688, but the length of initial conditions vector is 2' why this error is showing?

function dydt = my_ode_without_tld(i,y)
% tspan = i;                 %% Time span

%% Initial inputs
m1 = 10;            %% mass of the structure(kg)
k1 = 15;            %% stiffness of the structure(N/m)
c1 = 5;             %% damping of the structure(Ns/m)
A = 0.05;           %% Amplitude of ground displacement(m)
f = 1;            %% Input frequencycy(Hz)
fs = 1.111;             %% Frequency of structure(Hz)
n = 1;              %% Tuning ratio

%% define frequency
w1 = 3.48;                  %% frequency of structure

%% define damping ratio of structure
r1 = 0.01; %c1/(2*m1*w1);

%% define ground acceleration
ugdd = load('timehistory_elcentro.DAT')';

%% Equation to solve
dydt = [y(2) -ugdd-(2*r1*w1*y(2))-((w1)^2*y(1))].';

%% To run mass spring damper system
i = load('timedata_elcentro.dat')';
y = [0 0];

%% Solve using ode45

[tsol,ysol] = ode45('my_ode_without_tld', i, y, [1 0;0 1]);


%% plotting
plot(tsol,ysol(:,1))
xlabel('time(sec)')
ylabel('displacement(m)')
grid on
title('Displacement response of structure')
figure
plot(tsol,ysol(:,2))
xlabel('time(sec)')
ylabel('velocity(m/s)')
grid on
title('Velocity response of structure')

Answer 1

[Torsten]

The array dydt has 2688 elements (most probably because the vector ugdd has 2687 elements).

The ode solver expects dydt of length 2.

Try

function main
  %% To run mass spring damper system
  i = load('timedata_elcentro.dat')';
  ugdd = load('timehistory_elcentro.DAT')';
  y = [0 0];
  %% Solve using ode45
  [tsol,ysol] = ode45(@(t,y)my_ode_without_tld(t,y,i,ugdd), [i(1),i(end)], y);
  %% plotting
  plot(tsol,ysol(:,1))
  xlabel('time(sec)')
  ylabel('displacement(m)')
  grid on
  title('Displacement response of structure')
  figure
  plot(tsol,ysol(:,2))
  xlabel('time(sec)')
  ylabel('velocity(m/s)')
  grid on
  title('Velocity response of structure')
end
function dydt = my_ode_without_tld(t,y,tdata,ydata)
  %% Initial inputs
  m1 = 10;            %% mass of the structure(kg)
  k1 = 15;            %% stiffness of the structure(N/m)
  c1 = 5;             %% damping of the structure(Ns/m)
  A = 0.05;           %% Amplitude of ground displacement(m)
  f = 1;            %% Input frequencycy(Hz)
  fs = 1.111;             %% Frequency of structure(Hz)
  n = 1;              %% Tuning ratio
  %% define frequency
  w1 = 3.48;                  %% frequency of structure
  %% define damping ratio of structure
  r1 = 0.01; %c1/(2*m1*w1);
  %% define ground acceleration
  ugdd = interp1(tdata,ydata,t);
  %% Equation to solve
  dydt = [y(2) -ugdd-(2*r1*w1*y(2))-((w1)^2*y(1))].';
end

[RAJKUMAR SAHA]

Thank you so much....the code is running...