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

Hi, this error is occurred.

Error using DynamicSystem/lsim

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 in untitleds (line 321)

[Responset_q_equi] = lsim(sysansq_equi , INPUT_equi , tempo);

I thought of solving by considering INPUT_equi as a 5-row vector, since the state space matrix B has 5 columns, and 1 column using function repmat but it doesn't work :( even considering the number of lines equal to that of the elements of the time vector does not work

This is the script (sysansq_equi is already defined in the previous part of the script that is not reported here)

%DEFINIZIONE ingressi nel tempo

%load(['Published/','accDX_equi_QUARTER_CAR.dat'])

INPUT_DX_equi_QUARTER_CAR = accDX_equi_QUARTER_CAR(:,2);

tempo = accDX_equi_QUARTER_CAR(:,1); % è uguale per ogni caso avendo ip. per ogni caso v = 4 m/s

% cioè 14.4 km/h

dt=mean(diff(tempo)); %calcola la media degli incrementi tra tempo(i) e tempo(i+1) per ogni i

Fmax=1/(2*dt); % Nyquist -- Fmax = Fc/2

%load(['Published/','accSX_equi_QUARTER_CAR.dat'])

%INPUT_SX_equi_QUARTER_CAR = accSX_equi_QUARTER_CAR(:,2);

max(accDX_equi_QUARTER_CAR(:,2))

%max(accSX_equi_QUARTER_CAR(:,2))

INPUT_equi = INPUT_DX_equi_QUARTER_CAR;

[Responset_q_equi] = lsim(sysansq_equi , INPUT_equi , tempo);

figure (9)

plot(tempo,Responset_q_equi)

xlabel('Tempo [s]')

ylabel('q')

grid on

legend('q1','q2','q3','q4','q5','q6','q7','q8','q9','q10')

title('Coordinate normali caso equiripartito')

p.s. sysansq_equi doesn't contain errors

Answer 1

[Paul]

Hi Federico,

If sysansq_equi.B has five columns then INPUT_equi must also have five columns. Also, the number of rows of INPUT_equi must be the same as numel(tempo). What are the outputs of the following commands:

size(sysansq_equi.B,2)
numel(tempo)
size(INPUT_equi)

[Federico Paolucci]

In the command window, I obtain these values

size(sysansq_equi.B,2) 5

numel(tempo) 4001

size(INPUT_equi) 4001 1

[Federico Paolucci]

the problem is that INPUT_equi has one column

[Federico Paolucci]

Can I solve this problem?

[Paul]

Yes, INPUT_equi must have five columns. If you only want to see the output of the system in repsonse to the first input, then do

[Responset_q_equi] = lsim(sysansq_equi , [INPUT_equi zeros(numel(tempo),4)] , tempo);

[Federico Paolucci]

perfect! thank you!