  Many transitional wall-bounded shear flows are characterised by the
coexistence in state-space of laminar and turbulent regimes. Probing the edge
boundary between the two attractors has led in the last decade to the numerical
discovery of new (unstable) solutions to the incompressible Navier-Stokes
equations. However, the iterative bisection method used to achieve this can
become prohibitively costly for large systems. Here we suggest a simple
feedback control strategy to stabilise edge states, hence accelerating their
numerical identification by several orders of magnitude. The method is
illustrated for several configurations of cylindrical pipe flow. Travelling
waves solutions are identified as edge states, and can be isolated rapidly in
only one short numerical run. A new branch of solutions is also identified.
When the edge state is a periodic orbit or chaotic state, the feedback control
does not converge precisely to solutions of the uncontrolled system, but
nevertheless brings the dynamics very close to the original edge manifold in a
single run. We discuss the opportunities offered by the speed and simplicity of
this new method to probe the structure of both state space and parameter space.
