A disc drive actuation system for precisely positioning a read/write head
over a selected track of a rotatable disc. The actuation system comprises
a flexure, a slider, and a read/write head firmly attached to the slider.
A first drive unit is used to pivot the flexure to position the
read/write head approximately over a selected track. A microactuator is
mounted to the flexure and the slider is mounted to the microactuator.
The microactuator comprises an inner inactive region, a first outer
inactive region, a second outer inactive region, a first piezoelectric
section mounted between the first outer inactive region and the inner
inactive region, and a second piezoelectric section mounted between the
second outer inactive region and the inner inactive region. The inner
inactive region is firmly attached to either the flexure or the slider
and both of the outer inactive regions are firmly attached to the other
of the flexure or the slider. Also, there is an electrical circuit for
energizing the first and the second piezoelectric sections to cause them
to expand and contract in order to precisely position the read/write head
over the selected track. The circuit and the piezoelectric sections are
configured such that the first piezoelectric section expands when the
second piezoelectric section contracts and the first piezoelectric
section contracts when the second piezoelectric section expands. Since
the microactuator has to only overcome the inertial mass of the slider
and a portion of its own inertial mass, very precise control at high
frequency is possible.