How to turn a continuous time-y(t) array into Zero-Order-Hold and Tustin method discrete plot with different Ts

Hi, I've obtained the continuous plant of a cone-shaped-tank on Simulink. I took the data and turned into arrays both for time and y(t). I'd like to discretize both with ZOH and Tustin.

I haven't found any method yet.

Thank you in advance,

Pablo.

[Manikanta Aditya]

You can use MATLAB’s Control System Toolbox to convert your continuous-time model into a discrete-time model using the Zero-Order Hold (ZOH) and Tustin methods.

% Assuming 'sys' is your continuous-time system
Ts = 0.1; % Define your sampling time

% For Zero-Order Hold
sys_zoh = c2d(sys, Ts, 'zoh');

% For Tustin method
sys_tustin = c2d(sys, Ts, 'tustin');

• Continuous-Discrete Conversion Methods - MATLAB & Simulink (mathworks.com)
• Discretizing and Resampling Models - MATLAB & Simulink Example (mathworks.com)

Thanks!

[Pablo Graale]

Hi, unfortunately it's not a transfer function what I have, I tried that but it won't do. I have two arrays of data that I've obtained from my Simulink model, I don't know the transfer function. There's the trouble.

I have two arrays of data,

Time and y(t), I've obtained this data from my simulink via

Time = out.logsout{1}.Values.Time;

y = out.logsout{1}.Values.Data;

Another question to simplify everything would be: How can I turn this information into a transfer function, if I could do that then the problem is solved.

[Manikanta Aditya]

If you have time-series data and you want to estimate a transfer function, you can use the tfest function in MATLAB’s System Identification Toolbox. Here is a simple example:

% Assuming 'time' and 'y' are your arrays
data = iddata(y,[],Ts); % Create an iddata object, Ts is your sampling time
np = 2; % Number of poles
nz = 0; % Number of zeros
sys = tfest(data,np,nz); % Estimate transfer function

Once you have the transfer function, you can then discretize it using the Zero-Order Hold (ZOH) and Tustin methods as mentioned in the previous comments.

% For Zero-Order Hold
sys_zoh = c2d(sys, Ts, 'zoh');
% For Tustin method
sys_tustin = c2d(sys, Ts, 'tustin');

[Pablo Graale]

Mmm it doesn't allow me to use the tfest function with the data obtained with the iddata command. I've obtained something replacing the [] with the time, but I'm not certain the obtained data makes sense.

With the data from my system on Simulink I had the following

What the second plot means, is that the cone-shaped-cone takes about 25 seconds to empty and the dashed line is the linearized system I obtained with the Taylor expansion. The system looks a bit complex, I wish it was just a transfer function