%------------------------------------------------------------------------
%
% Nonlinear dampers model. New version without the inertia matrix.
%
% Author: Jose Paulo V. S. da Cunha
%
% Rio de Janeiro, January 08, 2003.
%
%------------------------------------------------------------------------

function [phi]=dampers(xp)

pi40=40/pi;

v31=xp(3)-xp(1);
phi1=7.5*v31+pi40*atan(v31*10);

v32=xp(3)-xp(2);
phi2=7.5*v32+pi40*atan(v32*10);

phi=[phi1 ; phi2 ; -(phi1+phi2)]*0.025;

return