A geometrical interpretation is proposed of the stability conditions f
or steady solutions of dynamical systems with simple symmetry in the L
yapunov-critical case, i.e. when the matrix of the linearization has o
ne zero eigenvalue and all other eigenvalues have negative real parts.
The change in the nature of the stability of a singular point when th
e parameter is varied is associated with bifurcations, represented by
cusp and butterfly singularities of the manifolds of steady states. An
alytic and numerical constructions are given of the bifurcation sets o
f the two-parameter families of steady states of two-unit systems with
rolling, and the relationship of the system parameters responsible fo
r the unsafe-safe boundary of the stability domain is determined. Copy
right (C) 1996 Elsevier Science Ltd.