Can I trust this closed loop response and include it as a final result in my Thesis?

have obtained the open loop response of my real plant and then I identified the transfer function from that response which is shown as: The image shows a blue line of my identified plant transfer.

Now I have designed the controller for my plant, and took closed loop response using Simulink:

Does it seem to be the correct closed-loop response of my plant? I took the above response as follows,

Answer 1

[Sam Chak]

Hi @Ayesha,

You can actually verify the result (from Check Bode Characteristics block) with the Bode plot of the Closed-loop System obtained in MATLAB.

%% Plant
Gp  = tf(1, [1 1 1])

Gp =
 
       1
  -----------
  s^2 + s + 1
 
Continuous-time transfer function.

%% PID Controller
Gc  = pidtune(Gp, 'PIDF')

Gc =
 
             1            s    
  Kp + Ki * --- + Kd * --------
             s          Tf*s+1 

  with Kp = 2.09, Ki = 1.19, Kd = 0.91, Tf = 0.00549
 
Continuous-time PIDF controller in parallel form.

%% Closed-loop system
Gcl = feedback(Gc*Gp, 1)

Gcl =
 
           167.8 s^2 + 381.4 s + 216.7
  ---------------------------------------------
  s^4 + 183.1 s^3 + 350.9 s^2 + 563.5 s + 216.7
 
Continuous-time transfer function.

%% Bode plot of the frequency response of Gcl
bode(Gcl), grid oo

Bode plot obtained in Simulink:

[Muhammad]

@Sam Chak

please check out my question and give me some solution

https://www.mathworks.com/matlabcentral/answers/2086943-why-does-my-closed-loop-response-with-mpc-look-like-this

[Ayesha]

Thank you Sam

[Ayesha]

@Sam Chak do you have answer for this issue?

https://www.reddit.com/r/ControlTheory/comments/1bb9p93/why_does_adding_a_feedforward_controller_decrease/?utm_source=share&utm_medium=web3x&utm_name=web3xcss&utm_term=1&utm_content=share_button

[Sam Chak]

Hi @Ayesha,

Unfortunately, I don't have a satisfactory answer. Could you please provide the theoretical proof to demonstrate that adding a feedforward MPC controller will increase the closed-loop bandwidth? This would allow individuals skilled in mathematics to investigate what might have deviated from your expectations.

Alternatively, it might be wise to post your problem on the MATLAB Answers forum, including the MATLAB code and Simulink model. This way, someone with expertise in MPC might be able to provide an answer.