Getting a "When simulating the response to a specific input signal, the input data U must be a matrix with as many rows as samples in the time vector T, and as many columns as input channels" error

I have a state space representation of a dynamical system. It 1 input and 3 outputs. I get the following error when I run my code: "When simulating the response to a specific input signal, the input data U must be a matrix with as many rows as samples in the time vector T, and as many columns as input channels." What am I doing wrong? Thank you.

clc
clear all
close all

t = 0:0.05:10;

m0 = 0.25; m1 = 0.1; m2= 0.08; %[kg]
L1 = 0.25; L2 = 0.2; %[m]
g = 9.81; %[m/s^2]
u = sin(size(t)); %[N]

A = [0 1 0 0 0 0;
     0 0 0 0 0 0;
     0 0 0 1 0 0;
     0 0 (3*(m1+2*m2))/(2*L1*(m1+3*m2)) 0 0 0;
     0 0 0 0 0 1;
     0 0 0 0 3*g/2*L2 0];
 
 B = [1/(m0+m1+m2);0;0;0;0;0];
 
 C = [1 0 0 0 0 0
      0 0 1 0 0 0
      0 0 0 0 1 0];
 
 D = [0;
      0;
      0];
states = {'x' 'x_dot' 'theta1' 'theta1_dot' 'theta2' 'theta2_dot'};
inputs = {'u'};
outputs = {'x'; 'theta1'; 'theta2'};
sys_ss = ss(A,B,C,D,'statename',states,'inputname',inputs,'outputname',outputs);
set(sys_ss,'InputName',inputs)
set(sys_ss,'OutputName',outputs)
[y,t] = lsim(sys_ss,u,t);
plot(t,y)

Answer 1

[Walter Roberson]

t = 0:0.05:10;

That has 201 entries. When you pass that vector of 201 entries into the time slot of lsim() then your state table, u, needs to have 201 rows.

u = sin(size(t))

size(t) is [1 201], so you are taking the sine of 1 radian and 201 radians, producing a 1 x 2 output.

Perhaps what you wanted was

u = sin(t);

but that would give you a 1 x 201 array, which would have one row instead of length(t) rows. So you would need

u = sin(t(:));