function model = beam_model_demo(q, voltage, Delta_t);

%
% function model = beam_model_demo(q, voltage, Delta_t);
%
% Runs the beam model for the voltage excited rod in the CRSC lab,
% and returns the model response at the point where the sensor
% is located.  The inputs are optional, that is the function may 
% be called as
%    model = beam_model_demo;
%    model = beam_model_demo(q);
%    model = beam_model_demo(q, voltage, Delta_t);
% In the first case, the default data set is loaded from the file
% input.mat, and default parameters are used.  In the second case,
% the default data is loaded, but the user supplied parameters are
% used in place of the defaults.  In the third case, user supplied
% parameters and data are used.
%
% Input Arguments (optional, see above):
%   q -- vector of parameters, in the following order.  The values 
%        given next to the parameter names are their default values,
%        which are used when a value is not given.
%     YI_beam -- the young's modulus time moment of inertia for the beam
%     CI_beam -- the internal damping parameter for the beam.
%     gamma -- coefficient of air damping
%     Kp -- coefficient for the voltage input
%     rho_patch -- linear density for the patch
%     YI_patch -- Young's modulus times moment of inertia for the patch
%     CI_patch -- the internal damping parameter for the patch
%  
% Output Argument
%   model -- model response for the given parameters and voltage input.
%
% NOTES:
%   No rho_beam parameter is present in q.  Analysis shows that one of the 
%     parameters is redundant.  Thus, any one parameter may be fixed with no
%     loss in generality.  rho_beam was chosen, since it is easy to estimate
%     from known material properties, which helps the other parameters be more
%     reasonable.
%   The effects of the patch can be ignored by only giving a four element vector
%     for q.  The patch components will be initialized to 0, which ignores their
%     contributition.  
%   All units for the parameters are assumed to be base metric, that is
%     meters, kilograms, Netwons, etc.
%
% Tom Braun
% North Carolina State University
% Department of Mathematics/Center for Research in Scientific Computing
% May 2005
%

if nargin < 1
    q = [];
end
if nargin < 3
    load input.mat;
end

% disallow bad parameters, and fill in missing ones
q(q < 0) = 0;
if length(q) < 1
    q(1) = 0.2; % YI_beam
elseif q(1)  < 1e-8
    q(1) = 1e-8;
end
if length(q) < 2
    q(2) = 7e-6; % CI_beam
end
if length(q) < 3
    q(3) = 1e-3; % gamma
end
if length(q) < 4
    q(4) = 2e-4; % Kp
end
if length(q) < 7
    q(length(q)+1:7) = 0;
end

rho = [0.072184; q(5); 0];
YI = [q(1); q(6); 0];
CI = [q(2); q(7); 0];
gamma = q(3);
Kp = q(4);
beamlen = 0.393;
patch_loc = [0.041, 0.092];
observe = 0.128;
N = 16;

model = beam_model(beamlen, rho, YI, CI, gamma, Kp, patch_loc, N, Delta_t, observe, voltage);