How can we represent this transfer function into state space representation in MATLAB?

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Hind Aljallaf
Hind Aljallaf 2023-5-1
回答： Sam Chak 2023-5-11
How can we represent this transfer function into state space representation in MATLAB? What are the commands that are regarding state space?

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回答（2 个）

Sachin
Sachin 2023-5-11
Hi
I understand that you want to find a state space representation of the transfer function.
For this, I suggest you to use MathWorks Control System Toolbox.
Follow these steps for a workaround:
  1. First, find the state space form on the transfer function using the “tf2ss” function. This output will be in the form of [A, B, C, D].
  2. After finding the state space form use the “canon” function to find the state space form.
[A_c, B_c, C_c, D_c] = canon(A, B, C, D, 'companion') %transform linear model into the canonical realization
Refer the below MATLAB documentation for state space Realizations:
https://in.mathworks.com/help/control/ug/canonical-state-space-realizations.html
You can refer to the following MATLAB documentation page for more information about “tf2ss”
https://in.mathworks.com/help/signal/ref/tf2ss.html
Refer to this MATLAB page for the “canon” function
https://in.mathworks.com/help/control/ref/dynamicsystem.canon.html
Sam Chak
Sam Chak 2023-5-11
Ran in:
Hi @Hind Aljallaf
As far as I know, there is no MATLAB command in the Control System Toolbox for directly computing the controllable canonical form. The canon() command only convert the identified state-space model to either the modal or companion canonical form.
G = tf([1 3], [1 3 2])
G = s + 3 ------------- s^2 + 3 s + 2 Continuous-time transfer function.
sys = ss(G); % convert from TF to random SS (non-unique)
You need to write a code to get the Observable Canonical form first and then transform it to Controllable Canonical form
obsys = ss(Aa, Bb, Cc, Dd) % Observable Canonical form
obsys = A = x1 x2 x1 0 -2 x2 1 -3 B = u1 x1 3 x2 1 C = x1 x2 y1 0 1 D = u1 y1 0 Continuous-time state-space model.
%% State-space in Conventional Controllable Canonical form
A = Aa';
B = Cc';
C = Bb';
D = Dd;
ctsys = ss(A, B, C, D) % Controllable Canonical form
ctsys = A = x1 x2 x1 0 1 x2 -2 -3 B = u1 x1 0 x2 1 C = x1 x2 y1 3 1 D = u1 y1 0 Continuous-time state-space model.
cttf = tf(ctsys)
cttf = s + 3 ------------- s^2 + 3 s + 2 Continuous-time transfer function.

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