This method is applicable to highly dissipative systems that are adequately modeled by iterative maps of a single variable. For our single variable we used the time interval between phase slips. Nonetheless, we found that by a simple sorting of the spatial behavior of the pattern, it is possible to untangle the temporal dynamics of the phase slips so that RPF is applicable. In the absence of control perturbations, the time interval varies between 75 and 140 periods of revolution. The size of the control perturbations is order thousandths of a Hz when the hourglass is rotating at order 3 Hz.
Control is robust and repeatable.