bilin.m

剑桥大学用于线性和双线性动力学系统辨识的工具箱

function model = bilin(A,B,C,D,N,X0,Ts)
%BILIN   Create a discrete-time, bilinear state-space model.
%
%   M = bilin(A,B,C,D,N) 
%   M = bilin(A,B,C,D,N,X0) 
%   M = bilin(A,B,C,D,N,X0,Ts)
%  
%   The output M is an object describing the discrete-time, bilinear
%   state-space model
%
%      x(t+Ts) = A x(t) + N kron(u(t),x(t)) + B u(t);   x(0) = X0
%         y(t) = C x(t) + D u(t),
%
%   where A is n-by-n, B is n-by-m, C is p-by-n, D is p-by-m and N is
%   n-by-(m*n). N := [N1 N2 ... Nm], where each Ni is n-by-n.
%
%   X0 is the initial state (default is X0 = 0) and Ts is the sample time
%   in seconds (default is Ts = 1).
%
%   See also BILINID, BILIN/SIM, BILIN/COMPARE, BILIN/ISSTABLE, BILIN/SIM,
%            BILIN/PE, KRON.
%
% CUED System Identification Toolbox.
% Cambridge University Engineering Department.
% Copyright (C) 1998-2002. All Rights Reserved.

% Version 1.00, Date: 01/06/2002
% Created by H. Chen and E.C. Kerrigan.

if nargin == 0

  model.A = [];
  model.B = [];
  model.C = [];
  model.D = [];
  model.N = [];
  model.X0 = [];
  model.Ts = 1;

  model = class(model,'bilin');

elseif nargin == 1

  % Should actually go into a converter method
  SYS = A;
  if isa(SYS,'ss') | isa(SYS,'idss')
	
	[n,m] = size(SYS.B);
	
	model.A = SYS.A;
	model.B = SYS.B;
	model.C = SYS.C;
	model.D = SYS.D;
	model.N = zeros(n,n*m);

	if isa(SYS,'idss')
	  model.X0 = SYS.X0;
	else
	  model.X0 = zeros(n,1);
	end
	
	if SYS.Ts > 0
	  model.Ts = SYS.Ts;
	else
	  error('SYS has to be a discrete-time model.')
	end

	model = class(model,'bilin');
	
  elseif isa(SYS,'bilin')
	model = SYS;
  else
	error('SYS has to be an SS, IDSS or BILIN object.')
  end
  
else
    
  if nargin < 5
	error('Please specify A,B,C,D and N.')
  end
  
  if nargin > 7
	error('Too many input arguments.')
  end
  
  if isempty(A) | isempty(B) |  isempty(C) |  isempty(D) |  isempty(N)
	error('Please specify A,B,C,D and N explicitly.')
  end

  [rA,cA] = size(A);
  [n,m] = size(B);
  [l,cC] = size(C);
  [rD,cD] = size(D);
  [rN,cN] = size(N);
  
  if ~(rA == n & cA == n & cC == n & l == rD & m == cD & rN == n & cN == m*n)
	error('The dimensions of A,B,C,D and N are incompatible.')
  end
  
  model.A = A;
  model.B = B;
  model.C = C;
  model.D = D;
  model.N = N;
  
  if nargin >= 6
	if isempty(X0)
	  model.X0 = zeros(n,1);
	else
	  if size(X0,1) == n & size(X0,2) == 1
		model.X0 = X0;
	  else
		error('X0 must be an n-dimensional column vector.')
	  end
	end
  else
	model.X0 = zeros(n,1);
  end
  
  if nargin >= 7
	if isempty(Ts)
	  model.Ts = 1;
	else
	  if Ts > 0
		model.Ts = Ts;
	  else
		error('Sample time Ts has to be greater than 0.')
	  end
	end
  else
	model.Ts = 1;
  end
  
  model = class(model,'bilin');
end

% *** last line of bilin.m ***