A compensation element (317) in a feedforward line in a dual stage control
system for a data storage system compensates for the undesired transient motion
of a first positioning element (i.e., a coarse actuator). The compensation element
is a transfer function that is applied from the first positioning element's control
signal (Uv) to a second positioning elements's (306) (i.e., microactuator's)
input. The transfer function is defined as formula (I) where ^Vnom (z)
is a transfer function model of the nominial portion of the first positioning element,
^Vres (z) is a transfer function model of the resonance portion of the
first positioning element, and ^M(z) is a transfer function model of the dynamics
of the second positioning element. This feedforward transfer function effectively
cancels the resonances of the first positioning element without requiring the inversion
of the resonance transfer function.