# How to change model architecture in controlsystemdesigner

2 views (last 30 days)
Nghi on 13 Dec 2023
Commented: Sam Chak on 21 Dec 2023
Hello, I have G rotor transfer function = 1/s^2 , and a PI controller (K rotor), the architecture of the model looks like this:
But in controlsystemdesigner, the architecture is the same, but it doesn't allow me to edit block H as a controller. Only C and F can be controller. How can I change that?
The characteristic equation is the same but I need the 1 zero at 0 only
Thank you
##### 2 CommentsShow NoneHide None
Fangjun Jiang on 13 Dec 2023
Edited: Fangjun Jiang on 21 Dec 2023
"The characteristic equation is the same but I need the 1 zero at 0 only"
???
Sam Chak on 21 Dec 2023
@Nghi, A brief analysis shows that if a PI controller is placed in the feedback loop, the system remains unstable. However, if it is replaced by a PD controller, the compensated system will be stable.
s = tf('s');
%% Rotor dynamics (Plant system)
Gp = 1/s^2
Gp = 1 --- s^2 Continuous-time transfer function.
%% Control gains
Kp = 1;
Ki = 1;
Kd = 2;
%% PI controller
Gc1 = Kp + Ki/s
Gc1 = s + 1 ----- s Continuous-time transfer function.
Gcl = minreal(feedback(Gp, Gc1))
Gcl = s -------------------------- s^3 - 1.11e-16 s^2 + s + 1 Continuous-time transfer function.
step(Gcl, 20), grid on
%% PD controller
Gc2 = Kp + Kd*s
Gc2 = 2 s + 1 Continuous-time transfer function.
Gcl = minreal(feedback(Gp, Gc2))
Gcl = 1 ------------- s^2 + 2 s + 1 Continuous-time transfer function.
step(Gcl, 20), grid on

Aiswarya on 19 Dec 2023
The blocks as such can't be edited but you can have different initial configurations with controlsystemdesigner using the 'sisoinit' function (https://www.mathworks.com/help/control/ref/sisoinit.html). There are a total of 6 configurations where you have different positions for the controllers. You can create a config object and then open the same with controlsystemdesigner:
initconfig = sisoinit(config_num);
controlsystemdesigner(initconfig);
For more information on supported control architectures you may refer to the following resource: https://www.mathworks.com/help/control/ug/feedback-control-architectures.html

### Categories

Find more on Classical Control Design in Help Center and File Exchange

R2022a

### Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!