This note studies the problem of finite-time output feedback stabilization
for the double integrator system. A class of output feedback controllers th
at fan achieve global finite-time stability for the double integrator syste
m are constructed based on a "finite-time separation principle." Furthermor
e, it is shown that the closed-loop system resulting From our control law c
an maintain its total finite-time stability regardless of some nonlinear pe
rturbations. Thus, our control law actually applies to a large class of non
linear second order systems.