%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%%   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);switch nargin,  case 0,    % if no input arguments, create a default object    r.x  = zeros(3,1);    r.C  = zeros(3);    r.rl = 0.08;    r.rr = 0.08;    r.b  = 0.4;    rb = robot('differential drive robot','',0,0);    r  = class(r,'robotdd',rb);        case 1,    % if single argument of class robotdd, return it    if (isa(varargin{1},'robotdd'))      r = varargin{1};     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    % set initial pose and pose covariance    if isfield(params,'xrinit'),      r = set(r,'x',params.xrinit);    end;    if isfield(params,'Crinit'),      r = set(r,'c',params.Crinit);    end;    % set name and formtype    if isfield(params.robot,'name'),      r = set(r,'name',params.robot.name);    end;    if isfield(params.robot,'formtype'),      r = set(r,'formtype',params.robot.formtype);    end;    % set kinematic parameters    r = set(r,'rl',params.robot.rl);    r = set(r,'rr',params.robot.rr);    r = set(r,'b',params.robot.b);