i want to get the overall transfer function of the parallel conncected transfer functions blocks

num1=[576 288];

den1=[4.8 34.992 73.392 1504.8];

num2=[57.6 230.4 -288];

den2=[249.831 1938.651 1742.688 -8162.8476 -11905.033 -241];

num3=[167.40 837.04];

den3=[57.708 179.307 1921.539 3712.548 1662.54];

>> [num,den]=parallel(num1,den1,num2,den2,num3,den3);

and iam getting this error Error using parallel (line 158)

Wrong number of input arguments for obsolete matrix-based syntax.

Answer 1

[Sam Chak]

Hi @deekshith, Check if this works for you.

%% Transfer function 1
num1=[576 288];
den1=[4.8 34.992 73.392 1504.8];
G1  = tf(num1, den1)

%% Transfer function 2
num2=[57.6 230.4 -288];
den2=[249.831 1938.651 1742.688 -8162.8476 -11905.033 -241];
G2  = tf(num2, den2)

%% Transfer function 3
num3=[167.40 837.04];
den3=[57.708 179.307 1921.539 3712.548 1662.54];
G3  = tf(num3, den3)

%% Transfer functions in parallel 
G   = parallel(parallel(G1, G2), G3)
G   = minreal(G)

[deekshith]

i'm getting error while giving these values for denominator

[1 18.16 158.9 1261 7275 2.884e04 9.946e04 1.535e05 -2.613e05 -1.167e06 -1.288e06 -4.503e05 -8713]

[deekshith]

@Sam Chak thanks for the code it helped me alot but iam trying to enter the values of the denominator in the transfer function block iam getting error like this

please tell me reason and tell me the solution to get rid of this error

[Sam Chak]

I cannot duplicate the error message because I can get the transfer function. I cannot find any hidden or invisible character. Please show the full MATLAB code so that I can look into the real issue.

[deekshith]

%% Transfer function 1

num1=[576 288];

den1=[4.8 34.992 73.392 1504.8];

G1 = tf(num1, den1)

%% Transfer function 2

num2=[57.6 230.4 -288];

den2=[249.831 1938.651 1742.688 -8162.8476 -11905.033 -241];

G2 = tf(num2, den2)

%% Transfer function 3

num3=[167.40 837.04];

den3=[57.708 179.307 1921.539 3712.548 1662.54];

G3 = tf(num3, den3)

%% Transfer functions in parallel

G = parallel(parallel(G1, G2), G3)

G = minreal(G)

by using this code i got the answer but while iam entering the denominator values i'm getting error

[deekshith]

but iam getting error in the transfer block in simlink model while apply the denominator values

Answer 2

[Sam Chak]

@deekshith, Oh I see. Because you left the spaces. Either you ensure no spaces, or place commas (,) between the elements.