Hardware Reference
In-Depth Information
Figure 5.8: HSTW experimental setup.
In a typical multidisk servo track writer, a high speed active air bearing
spindleisusedwhereapackof10to20diskscanbeeasilymountedandre-
moved. Since this setup is built to demonstrate the working principle and it
is not meant for commercial use, a fl uid bearing spindle motor is used instead
of air bearing spindle for the simplicity of realization. It can carry up to fi ve
2 2
is used to rotate the actuator.
Each arm of the actuator is embedded with a low voltage monolithic multi-
layer piezo actuator chip PL033 § of dimension 3mm× 3mm× 2mm,asshown
in Figure 5.9, so that these arms can be de fl ected and hence the head moved
using the piezoelectric effect. With a driving voltage of 100 V, the PL033
PZT chip can generate 0.5 µm displacement. However, the mechanical ampli-
fi cation provided by the arm results in larger de fl ection of the slider. In the
system developed at DSI, the displacement produced at the read/write head
is about ±3µm for an input driving voltage of 30V, indicating a factor of 20
mechanical ampli fi cation. After tuning and optimization of the design, such as
using balanced arm design having the actuator arm's center of gravity aligned
to the center of its rotation, the fi rst minor and the fi rst major resonances of
the system are observed at 5.8 kHz and 7 kHz, respectively. These resonances
limit the achievable servo bandwidth to about 2 kHz.
We note hat the con fi guration in Figure 5.9 is effectively a PZT “actuated
arm” driving a commercial suspension that has a higher mass compared with
that of the actuated suspension or slider discussed in section 3.6. To achieve
higher servo bandwidth and better positioning accuracy, actuated suspension
inch disks. A MicroE micro positioner
See webpage at http://www.microesys.com/
Product of Physik Instrumente (PI) GmbH & Co. KG, Karlsruhe/Palmbach, Germany,
http://www.physikinstrumente.de/products/prdetail.php?secid=1-14
§
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