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msm/ShoulderModel_HHT/initilize_contact_model.m
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initilize_contact_model.m
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function CMDATA = initilize_contact_model()
%{
Function for initializing the contact model.
--------------------------------------------------------------------------
Syntax :
[Dir_contact,Rho_contact,F_contact]= contact_model(Rot_H2T,r_HH)
--------------------------------------------------------------------------
Function Description :
This function spans the surface of the humerus to define the points h_i s
on the surface. It also defines the constant values of the contact model.
We define the points h_i here to expedite the execution of the model.
--------------------------------------------------------------------------
%}
% define the position of the hi in the humerus frame {H}:
CMDATA.SpanStepSize = 2*pi/30; % spanning step size
theta = [0:CMDATA.SpanStepSize:2*pi]; % longtitude 0<theta<2pi on the xy from x
phi = [0:CMDATA.SpanStepSize:pi]; % latitude 0<phi<pi from z
CMDATA.r = 30e-3; % radius of the humeral head [m]
CMDATA.r_g = 45e-3; % radius of the glenoid fossa [m]
CMDATA.s = 1.896e7; % aggregate modulus [N/m2]
CMDATA.b = 3.6e-3; % cartilage tickness (glenoid fossa+ humral head) [m]
CMDATA.c = 2e4; % damping coefficient of the cartilage [N.s/m]
CMDATA.r_h = 12e-3; % humerus radius [m] (for illustration only)
CMDATA.alpha = 1.15e6; % elastic parameter [Mpa]
CMDATA.beta = 1.17; % elastic parameter []
CMDATA.eta = 20e6; % viscous parameter [Mpa s]
CMDATA.clearance = 2e-3;
CMDATA.stiffness = 500*10^4.5;
CMDATA.damping = 5e4;
% define the top and bottom points of the sphere (and their associated
% surafce areas)
CMDATA.h{1,1} = CMDATA.r*[cos(theta(1))*sin(phi(1));
cos(phi(1));
sin(theta(1))*sin(phi(1))];
CMDATA.a(1,1) = size(theta,2)*(0.5*CMDATA.r^2*CMDATA.SpanStepSize^2*...
sin(phi(2))*cos(CMDATA.SpanStepSize/2));
CMDATA.h{size(theta,2),size(phi,2)} = CMDATA.r*[cos(theta(1))*sin(phi(size(phi,2)));
cos(phi(size(phi,2)));
sin(theta(1))*sin(phi(size(phi,2)))];
CMDATA.a(size(theta,2),size(phi,2)) = CMDATA.a(1,1);
% span the whole surface of the humeral head and define the center points
% of the mesh grids. And rightafter their associated surace areas.
for i = 1:size(theta,2)-1 % theta = 0 and 2pi result in the same points
for j = 2:size(phi,2)-1 % exclude the top and bottom points
CMDATA.h{i,j} = CMDATA.r*[cos(theta(i))*sin(phi(j));
cos(phi(j));
sin(theta(i))*sin(phi(j))]; % hi in the {H} frame
CMDATA.a(i,j) = CMDATA.r^2*sin(phi(j))*CMDATA.SpanStepSize^2; % surface area of the mesh grid [m^2]
end
end
return;
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