Matlab error in simulink for numerator of transfer function 'Unable to use a value of type tf as an index'

I have simulink model contains multiple subsystems and one of the subsystem contains transfer functions which is defined in Matlab script as:

Z_tot = (1/(s*C_MOSFET))*(R_MOSFET + Z_C_Cu_Rcu_Rdielec_Z_ans)/((R_MOSFET + Z_C_Cu_Rcu_Rdielec_Z_ans)+(1/(s*C_MOSFET)));

[num_th,den_th] = tfdata(Z_tot,'v');

And when i simulate my model i have one error related to transfer functions. The full error sstatement is shown as below.

Invalid setting in 'model_1/GoKart/Inverter/T_junction_MOSFET/Transfer Fcn Heat sink 1' for parameter 'Numerator'.

Caused by:

Error evaluating parameter 'Numerator' in 'model_1/GoKart/Inverter/T_junction_MOSFET/Transfer Fcn Heat sink 1'

Unable to use a value of type tf as an index.

Please give me some recomendations to solve the problem.

Thanks in advance!

[Jyotsna Talluri]

Can you attach your simulink model?

[Selam Dagne]

Hi Jyotsna;

Thank you for your replay!

Here is my simulink model with m-files.

Thank you in advance!

Answer 1

[Jyotsna Talluri]

Here variable s represents the transfer function and cannot be used as an index to access the elements of the arrays num_th_Case, den_th_Case.Instead you can specify the whole arrays num_th_Case and den_th_Case in the numerator and denominators of the transfer functions

Answer 2

[siti nurul ain zakaria]

num=[1 23 4 17];
den=[21 5 6 7 3];
g1=tf(num,den);
g2=zpk(g1)

Unable to use a value of type tf as an index.

how i want to fix this for line 4