functionfrequencyEvaluate

Evaluate a SISO transfer function defined by Zeros and Poles matrices at a given complex value re + j*im

Extends from Modelica.Icons.Function (Icon for functions).

Information

Syntax

result = ZerosAndPoles.Analysis.evaluate(zp, p, den_min=0)

Description

Function Analysis.evaluate evaluates the ZerosAndPoles transfer function at a given (complex) value of p and returns the value G(p)=N(p)/D(p). The optional argument den_min with default 0 is used to guard against a division by zero.

if |(D(p))| >= den_min then
   G(p) = N(p) / D(p);
elseif D(p).re >= 0.0 then
   G(p) = N(p) / den_min
else
   G(p) = -N(p) / den_min
end if;

Example

  import Modelica.ComplexMath.j;
  ZerosAndPoles p = Modelica_LinearSystems2.ZerosAndPoles.p();
  Modelica_LinearSystems2.ZerosAndPoles zp=(p+1)/(p^2+p+1);

  Complex result;

algorithm
  result := Modelica_LinearSystems2.ZerosAndPoles.Analysis.evaluate(zp, j+1);
//  result = 0.538462 - 0.307692*j

Inputs

Type	Name	Description
Real	gain	Gain of transfer function
Real[:,2]	Zeros	Zeros as Real matrix (first column: real, second column imaginary values)
Real[:,2]	Poles	Poles as Real matrix (first column: real, second column imaginary values)
Real	re	Real value of complex number
Real	im	Imaginary value of complex number

Outputs

Type	Name	Description
Real	A	Amplitude of complex value
Modelica.Units.SI.Angle	phi	Angle of complex value
Integer	info	= 0/1/2 success/infinity(A is a large value)/indefinite (A=0/0; A=0 returned)

Revisions

Date	Author	Comment
2010-05-31	Marcus Baur, DLR-RM	Realization