  The complex time evolution in the X-ray light curves of the peculiar black
hole binary GRS 1915+105 can be obtained as solutions of a non-linear system of
ordinary differential equations derived form the Hindmarsch-Rose model and
modified introducing an input function depending on time. In the first
paper,assuming a constant input with a superposed white noise, we reproduced
light curves of the classes rho, chi, and delta. We use this mathematical model
to reproduce light curves, including some interesting details, of other eight
GRS 1915+105 variability classes either considering a variable input function
or with small changes of the equation parameters. On the basis of this extended
model and its equilibrium states, we can arrange most of the classes in three
main types: i) stable equilibrium patterns: (classes phi, chi, alpha'', theta,
xi, and omega) whose light curve modulation follows the same time scale of the
input function, because changes occur around stable equilibrium points; ii)
unstable equilibrium patterns: characterised by series of spikes (class rho)
originated by a limit cycle around an unstable equilibrium point; iii)
transition pattern: (classes delta, gamma, lambda, kappa and alpha'), in which
random changes of the input function induce transitions from stable to unstable
regions originating either slow changes or spiking, and the occurrence of dips
and red noise. We present a possible physical interpretation of the model based
on the similarity between an equilibrium curve and literature results obtained
by numerical integrations of a slim disc equations.
