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error in ss2tf when modelling a DC motor

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Avinash Tallapaneni
Avinash Tallapaneni on 7 Sep 2018
Answered: Xu Da on 26 Apr 2019
hello guys,
i am getting error when i try to run it. it says " The B and D matrices must have the same number of columns."
%motor parameters
Km = 50.2*10^-3; % NM/A
Kb = (1/(190*2*pi/60)); %or V/Wm (wm in rps) volt/rps
Jm =11.6 *10^-7; %kgm^2
Bm = ((50.2*10^-3)*(20*10^-3)/(9080*2*pi/60));
R =10.6; %ohm
L = .82*10^-3;% H(henry)
%state space model
A = [-R/L -Kb/L ;Km/Jm -Bm/Jm ];
B = [1/L 0 ;0 -1/Jm ];
C = [0 1];
D = 0;
%state space
Motor_ss = ss(A,B,C,D);
[num_omega, dem_omega] = ss2tf(A,B,C,D);
can someone identify whats wrong with this code?

  2 Comments

Star Strider
Star Strider on 7 Sep 2018
Please post your original model equations, or a PDF or an image of them.
Avinash Tallapaneni
Avinash Tallapaneni on 7 Sep 2018
i have inserted final model equation...

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Answers (1)

Xu Da
Xu Da on 26 Apr 2019
Hi, Tallapaneni
You have got the error B value. It shoud be like that
B = [1/L ; -1/Jm ]

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