"Error using vertcat Dimensions of arrays being concatenated are not consistent." why this error showing?

function M = mass(t,q)

% Mass matrix function
M = zeros(4,4);
M(1,1) = 1;
M(2,2) = 1;
M(3,3) = 1;
M(4,2) = 1;
M(4,4) = 1;
end  
function dqdt = my_ode(t,q)
%% Conversion to first order parameters
% y = q(1);                  %% displacement of damper
% ydot = q(2);               %% velocity of damper
% yddot = q(2)dot;           %% acceleration of damper
% z = q(3);                  %% displacement of structure
% zdot = q(4);               %% velocity of structure
% zddot = q(4)dot;           %% acceleration of structure
% q = [q(1) q(2) q(3) q(4)]; %% Output parameters
% tspan = i;                 %% Time span

%% Initial inputs
m1 = 200;            %% mass of the structure(kg)
k1 = 15;             %% stiffness of the structure(N/m)
c1 = 5;              %% damping of the structure(Ns/m)
k2 = 150;            %% stiffness of the damper(N/m) 
R = 0.5;             %% Radius of the tank(m)
h = 0.05;            %% Height of liquid in tank(m)
g = 9.81;            %% Acceleration due to gravity(m/s^2)
A = 0.05;            %% Amplitude of ground displacement(m)
f = 1;               %% Input frequencycy(Hz)
rho = 1000;          %% Density of fluid(Kg/m^3)
xi = 1.841;          %% First derivative of the Bessel function for first mode
fs = 1.111;          %% Frequency of structure(Hz)
n = 1;               %% Tuning ratio
nu = 10^-6;          %% Kinematic viscosity of water(m^2/s)
t = 0:0.1:20;        %%Time span

%% Mass of the damper
m2 = ((pi*rho*R^3)/2.2)*tanh(xi*h/R);

%% Damping coefficient of damper
c2 = ((5.78*sqrt(m2*k2))/pi)*sqrt(nu/((R)^1.5*(g)^0.5))*(1+((0.318/sinh(xi*h/R))*(1+((1-h/R)/cosh(xi*h/R)))));

%% structure frequency
w1 = 3.48;                

%% damper frequency
w2 = sqrt(xi*g*tanh(xi*(h/R))/R);                            

%% define damping factor of damper
r2 = c2/(2*m2*w2);          

%% define damping factor of structure
r1 = 0.01;

%% define mass ratio
barm = (((R^3*pi*rho)/(2.2))*tanh(xi*(h/R)))/(m1);

%% define ground acceleration
ugdd = A*sin(2*pi*f*t);

%% Equation to solve
dqdt = [q(2)
    (-2*r1*w1*q(2))-((w1)^2*q(1))+(2*r2*w2*barm*q(4))+(barm*(w2)^2*q(3))-ugdd
    q(4)
    -ugdd-(2*r2*w2*q(4))-((w2)^2*q(3))];

clc;
clear all;
%% To run mass spring damper system
tspan = 0:0.1:20;
q = [0 0 0 0];

opts = odeset('Mass',@(t,q) mass(t,q));

%% Solve using ode45

[tsol,qsol] = ode45(@(t,q)my_ode(t,q),tspan,q,opts);


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

Answer 1

[Torsten]

function "my_ode" lacks an "end" statement.

[RAJKUMAR SAHA]

after entering END Still it showing error

[Torsten]

Delete the line

t = 0:0.1:20

in my_ode.

You are only allowed to work with the scalar t given in the list of input parameters (t and q).

[RAJKUMAR SAHA]

But 'ugdd' depends on t=0:0.1:20

so, what to do?

[Torsten]

Yes, it's the t from the inputs

function dqdt = my_ode(t,q)

with which the equation

ugdd = A*sin(2*pi*f*t);

is evaluated.

It's the actual time the ode solver has reached during integration.

Is this incorrect ?

[RAJKUMAR SAHA]

if i delete the line t = 0:0.1:20, then ugdd is taken as zero only.

[Torsten]

No.

ugdd = A*sin(2*pi*f*t);

with t taken from

function dqdt = my_ode(t,q)

and this t runs from 0 to 20.