CODEWITHSUNDEEP
matlabfeedback
Chery
Chery

Reputation: 5

MATLAB: why is there an error in the place command?

I am writing a code to find the k in the state feedback, but there's an error

A=[0 0 0 217.28; 0 0 127.33 0; 0 -1 -3.73 0.97; -1 0 0.97 -3.73]; %4*4
B=[0 0 -.38 -1.39; 0 0 -1.18 0.29].'; %4*2
C=[1 0 0 0]; %1st row of C
D=zeros(1, 2);

% Desired pole locations
desired_poles = -1 * ones(1, size(A, rank(B))); % All poles at -1

% Calculate the feedback gain matrix K using pole placement
k = place(A, B, desired_poles)


% Create the closed-loop system
Aclosed = A - B * k;
Bclosed = B;
Cclosed = C;
Dclosed = D;

% Check the poles of the closed-loop system
closed_loop_poles = eig(Aclosed);
disp('Poles of the closed-loop system:');
disp(closed_loop_poles);

I was expecting it to display the k & closed_loop_poles. Instead I get:

Error using [place](matlab:matlab.internal.language.introspective.errorDocCallback('place'))
The "place" command cannot place poles with multiplicity greater than rank(B).

Upvotes: 0

Views: 392

Answers (1)

Munjam Navadeep
Munjam Navadeep

Reputation: 15

I noticed a potential issue in your code. The line size(A, rank(B)) may not return the expected size for desired_poles. The correct size should be the number of columns in matrix B, as you want one pole for each input. Replace this line: desired_poles = -1 * ones(1, size(A, rank(B))); With: desired_poles = -1 * ones(1, size(B, 2));

This ensures that desired_poles has the correct size based on the number of columns in matrix B. After making this change, your code should work as intended for pole placement in state feedback.

Upvotes: 2

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