Stability improvement of nonlinear systems by feedback

This paper is concerned with the property of stabilizing a nonlinear system to a specified equilibrium point arbitrarily fast by appropriate smooth feedback. Two closely related forms of this property are explored. One refers to the asymptotic transfer to the critical point with exponential decay, and it is shown that the systems possessing the above property are precisely those whose corresponding linearization is controllable. The second stabilizability form defined here amounts to driving the system back to an arbitrarily small neighborhood of the given point arbitrarily fast by smooth feedback. A global stabilization result is also included, finding application in Hamiltonian systems. Special emphasis is given to the bilinear case.