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

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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!

Accepted Answer

Jyotsna Talluri
Jyotsna Talluri on 25 Apr 2020
Edited: Jyotsna Talluri on 25 Apr 2020
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


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