function yprime = flywheel(t,y,flag,alpha,r1,r2)
%FLYWHEEL peptide coordinated motion Equation
r12 = r1*r2;
sa = sin(alpha); ca = cos(alpha);
c1 = cos(y(1)); s1 = sin(y(1));
c2 = cos(y(2)); s2 = sin(y(2));
s1c2 = s1*c2; c1s2 = c1*s2;
F1 = -r1*sa*c1 - r12*(s1c2 - c1s2*ca);
F2 =  r2*sa*c2 - r12*(c1s2 - s1c2*ca);
Mu = (F1^2 + F2^2)^(1/2);
yprime =[-F2; 
          F1]/Mu;
