  The slow passage through a Hopf bifurcation leads to the delayed appearance
of large amplitude oscillations. We construct a smooth scalar feedback control
which suppresses the delay and causes the system to follow a stable equilibrium
branch. This feature can be used to detect in time the loss of stability of an
ageing device. As a by-product, we obtain results on the slow passage through a
bifurcation with double zero eigenvalue, described by a singularly perturbed
cubic Lienard equation.
