%ROBOTDD Constructor function for differential drive robot object.%   R = ROBOTDD%   Creates a new differential drive robot object with default%   values.%%   R = ROBOTDD(R)%   Copies and returns the differential drive robot object R%%   R = ROBOTDD(NAME,X,C,RL,RR,B,FORMTYPE,T)%   Creates a new differential drive robot object with values%       NAME : name string%          X : 3x1 robot state vector, interpreted as%              [x y theta] in units [m] [m] [rad]%          C : 3x3 state covariance matrix%              [sxx sxy sxt; sxy syy syt; sxt syt stt]%         RL : radius of left wheel in [m]%         RR : radius of right wheel in [m]%          B : wheel base in [m]%   FORMTYPE : form type identifier according to DRAWROBOT%          T : discrete time index or timestamp%%   R = ROBOTDD(PARAMS)%   Creates a new differential drive robot object from the%   fields of the structure PARAMS. PARAMS has the arguments%   from above as fields .NAME,.X,.C,.RL,.RR,.B,...%   If PARAMS does not contain all required fields, an error%   message is returned.%%   The robot reference frame is attached to the center of the%   wheel base such that the x-axis looks forward.%%   The differential drive robot class is a child class of the%   base class robot.%%   Examples:%      r = robotdd('Piggy',[1,2,pi]',eye(3),.2,.2,.5,4,now);%%   See also ENTITY, CLASS, DRAWROBOT.% Copyright (c) 2004, CAS-KTH. See licence file for more info.% v.1.0, Nov. 2003, Kai Arrasfunction r = robotdd(varargin);% Constants: default valuesDEFX  = zeros(3,1);  % default initial robot poseDEFC  = zeros(3);    % default initial robot pose cov.DEFRL = 0.08;        % default radius of left wheel in [m]DEFRR = DEFRL;       % default radius of right wheel in [m]DEFB  = 0.4;         % default wheelbase in [m]DEFT  = 0;           % default initial timestampDEFNAME = '';        % default robot nameDEFFORM = 0;         % default robot form typeswitch nargin,  case 0,    % if no input arguments, create a default object    r.x  = DEFX;    r.C  = DEFC;    r.rl = DEFRL;    r.rr = DEFRR;    r.b  = DEFB;    rb = robot('differential drive robot',DEFNAME,DEFFORM,DEFT);    r  = class(r,'robotdd',rb);        case 1,    if isa(varargin{1},'robotdd'),      % if single argument of class robotdd, return it      r = varargin{1};     elseif isstruct(varargin{1}),      % if structure, get fields, create object      p = varargin{1};      if isfield(p,'name'), rname = p.name;      else rname = DEFNAME; end;      if isfield(p,'x'), r.x = p.x;      else r.x = DEFX; end;      if isfield(p,'c'), r.C = p.c;      elseif isfield(p,'C'), r.C = p.C;      else r.C = DEFC; end;      if isfield(p,'rl'), r.rl = p.rl;      else r.rl = DEFRL; end;      if isfield(p,'rr'), r.rr = p.rr;      else r.rr = DEFRR; end;      if isfield(p,'b'), r.b = p.b;      else r.b = DEFB; end;      if isfield(p,'formtype'), rformtype = p.formtype;      else rformtype = DEFFORM; end;      if isfield(p,'time'), rtime = p.time;      elseif isfield(p,'timestamp'), rtime = p.timestamp;      else rtime = DEFT; end;      rb = robot('differential drive robot',rname,rformtype,rtime);      r  = class(r,'robotdd',rb);          else      error('robotdd: Input argument not a differential drive robot object')    end  case 8,    % create object using specified values    x = varargin{2};    C = varargin{3};    if (prod(size(x)) == 3) & (size(C) == [3,3]),      r.x  = x;      r.C  = C;      r.rl = varargin{4};      r.rr = varargin{5};      r.b  = varargin{6};      rb = robot('differential drive robot',varargin{1},varargin{7},varargin{8});      r  = class(r,'robotdd',rb);    else      error('robotdd: Wrong argument syntax');    end;  otherwise    error('robotdd: Wrong number of input arguments')end