The stabilization problem of the upright position of the sherical pendulum
is treated in detail. This problem is reduced to the stabilization of the s
table manifold Omega (st) of the upright position of the unforced spherical
pendulum. It is shown that for any smooth feedback control derived by the
speed-gradient algorithm with the objective to stabilize Omega (st) the clo
sed loop system has a limit cycle T, which does not belong to the desired a
ttractor Omega (st). It is shown that Gamma is hyperbolic.