In man physical problems, equilibrium stabilization is not possible and the
controlled system is in a limit cycle. If the size of the limit cycle depe
nds on some of the control parameters, then a reasonable objective would be
to tune this parameter to minimize the size of the limit cycle. In this pa
per, we propose a method for achieving this. This method is an extension of
our earlier result [13] on extremum seeking for equilibria. We illustrate
the method with a Van der Pol oscillator example and present analysis for i
t using averaging and singular perturbations.