
Re: Help with a function for plotting zeros and poles
Posted:
Mar 19, 2014 4:23 AM


Clear[zeroPole]
zeroPole[tf_TransferFunctionModel] := {Re[#], Im[#]} & /@ Flatten[ Through@ {TransferFunctionZeros, TransferFunctionPoles}@ tf];
tf1 = TransferFunctionModel[ (3 (13/8 + s))/(2 (3/2 (13/8 + s) + s (1 + s) (2 + s) (5 + s))), s];
tf2 = TransferFunctionModel[ (199 + 344 s)/(16 (s (1 + s) (2 + s) (5 + s) + 1/16 (199 + 344 s))), s];
N@zeroPole[tf1]
{{1.625, 0.}, {0.5, 0.}, {0.5, 0.}, {5.08114, 0.}, {1.91886, 0.}}
N@zeroPole[tf2]
{{0.578488, 0.}, {0.5, 0.}, {5.97986, 0.}, {0.760068, 1.89264}, {0.760068, 1.89264}}
Bob Hanlon
On Sat, Mar 15, 2014 at 3:46 AM, Eduardo M. A. M. Mendes < emammendes@gmail.com> wrote:
> Hello > > Sometime ago I found a couple of functions that are used for plotting the > poles and zeros of a transfer function. Here they are: > > > xyPoints[values_]:=Module[{xy},xy=Flatten[Replace[values,{Complex[x_,y_]:>{x,y},x_?NumericQ:>{x,0}},{3}],1];Cases[xy,{_?NumericQ,_?NumericQ},{2}] > ]; > > zeroPole[tf_]:=Module[{zp,zp0},zp0=Through@ > {TransferFunctionZeros,TransferFunctionPoles}@tf; > zp=FixedPoint[ReplaceAll[#,{}>{100}]&,zp0]; > xyPoints/@zp]; > > zeroPole is a modification of the actual plot function (I have only > removed the plot command). > > Here are two examples of using the functions > > tf1=TransferFunctionModel[(3 (13/8+s))/(2 (3/2 (13/8+s)+s (1+s) (2+s) > (5+s))),s] > tf2=TransferFunctionModel[(199+344 s)/(16 (s (1+s) (2+s) (5+s)+1/16 > (199+344 s))),s] > > N@zeroPole[tf1] > {{{1.625,0.}},{{0.5,0.},{0.5,0.},{5.08114,0.},{1.91886,0.}}} > > N@zeroPole[tf2] > {{{0.578488,0.}},{{0.5,0.},{5.97986,0.},{0.7600681.89264 > I,0.},{0.760068+1.89264 I,0.}}} > > The functions does what I expected for the first example, but not for the > second example (the real and imaginary parts of the complex poles are not > dealt with). > > Can someone tell me what is wrong? And how to modify xyPoints (Although > I understand what the functions does I am not sure what to do)? > > Many many thanks > > Ed > > >

