function Jac = calcul_Jac( X,w )

global rs  Xls  Xm  Xlr  rr  J  P  dt  Xrr  Xss  D

F_qs = X(1);   F_ds = X(2);   F_qr = X(4);   F_dr = X(5);   wr = X(7);

j11 = 1 + dt*rs*w*Xrr/(2*D);    j12 = dt*w/2;    j14 = -dt*rs*w*Xm/(2*D);

j21 = -dt*w/2;   j22 = j11;   j25 = j14;

j33 = 1 + dt*rs*w/(2*Xls);

j41 = -dt*rr*w*Xm/(2*D);   j44 = 1 + dt*rr*w*Xm/(2*D);   
j45 = dt*(w-wr)/2;   j47 = -dt*F_dr/2;

j52 = -dt*rr*w*Xm/(2*D);   j54 = -dt*(w-wr)/2;   
j55 = 1 + dt*rr*w*Xss/(2*D);   j57 = dt*F_qr/2;

j66 = 1 + dt*rr*w/(2*Xlr);

j71 = -3*dt*P^2*Xm*F_dr / (16*J*w*D);   j72 = 3*dt*P^2*Xm*F_qr / (16*J*w*D);
j74 = 3*dt*P^2*Xm*F_ds / (16*J*w*D);    j75 = -3*dt*P^2*Xm*F_qs / (16*J*w*D); 


Jac = [ j11   j12    0    j14    0     0     0 
        j21   j22    0     0    j25    0     0 
         0     0    j33    0     0     0     0
        j41    0     0    j44   j45    0    j47
         0    j52    0    j54   j55    0    j57
         0     0     0     0     0    j66    0
        j71   j72    0    j74   j75    0     1  ];
        
return