% Nise, N.S.
% Control Systems Engineering, 6th ed.
% John Wiley & Sons, Hoboken, NJ, 07030
% Control Systems Engineering Toolbox Version 6.0
% Copyright 2011 by John Wiley & Sons, Inc.
% (ch3p5): State-space representations can be converted to transfer functions
% represented by a numerator and a denominator using [num,den] = ss2tf(A,B,C,D,iu),
% where iu is the input number for multiple-input systems. For single-input,
% single-output systems iu = 1. For an LTI state-space system, Tss, the conversion
% can be implemented using Ttf = tf(Tss) to yield the transfer function in polynomial
% form or Tzpk = zpk(Tss) to yield the transfer function in factored form. For example,
% the transfer function represented by the matrices described in (ch3p3)
% can be found as follows:
'(ch3p5)' % Display label.
'Non LTI' % Display label.
A=[0 1 0;0 0 1;-9 -8 -7]; % Represent A.
B=[7;8;9]; % Represent B.
C=[2 3 4]; % Represent C.
D=0; % Represent D.
'Ttf(s)' % Display label.
[num,den]=ss2tf(A,B,C,D,1) % Convert state-space
% representation to a
% transfer function represented as
% a numerator and denominator in
% polynomial form, G(s)=num/den,
% and display num and den.
'LTI' % Display label.
Tss=ss(A,B,C,D) % Form LTI state-space model.
'Polynomial form, Ttf(s)' % Display label.
Ttf=tf(Tss) % Transform from state space to
% transfer function in polynomial
'Factored form, Tzpk(s)' % Display label.
Tzpk=zpk(Tss) % Transform from state space to
% transfer function in factored