dx1/dt = (-p1*km*x1 - p1*x1^2 + km*u1(t) - x1*vm + x1*u1(t)) / (km + x1),
dx2/dt = -p2*x2 + p1*x1,
dx3/dt = p2*x2 - x3*p3,
dx4/dt = x3*p3 - x4*p4,
dx5/dt = -p5*x5 + x4*p4,
dx6/dt = -p6*x6 + p5*x5,
dx7/dt = -p7*x7 + p6*x6,
dx8/dt = p7*x7 - p8*x8,
dx9/dt = -x9*p9 + p8*x8,
dx10/dt = x9*p9 - x10*p10,
dx11/dt = x10*p10 - x11*p11,
dx12/dt = x11*p11 - p12*x12,
dx13/dt = -x13*p13 + p12*x12,
dx14/dt = x13*p13 - p14*x14,
dx15/dt = -p15*x15 + p14*x14,
dx16/dt = p15*x15 - x16*p16,
dx17/dt = -p17*x17 + x16*p16,
dx18/dt = -p18*x18 + p17*x17,
dx19/dt = -x19*p19 + p18*x18,
dx20/dt = -p20*x20 + x19*p19,
y1 = x1,
y2 = x2,
y3 = x3,
y4 = x4,
y5 = x5,
y6 = x6,
y7 = x7,
y8 = x8,
y9 = x9,
y10 = x10,
y11 = x11,
y12 = x12,
y13 = x13,
y14 = x14,
y15 = x15,
y16 = x16,
y17 = x17,
y18 = x18,
y19 = x19,
y20 = x20
