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Chapter 6 FAQ
How does a piezo inertia motor work?
A piezo inertia actuator uses friction and inertia (stick/slip) to rotate a fine mechanical
drive screw. The piezo is driven by a saw tooth voltage waveform. As the voltage is
ramped up, the piezo will extend and turn the screw (stick). When the voltage is
dropped to zero, the piezo returnes to its original length. By using different rates of
voltage rise and fall, the drive screw rotates more in one direction than the other due
to inertia and different frictional coefficients, reulting in residual rotation. This in turn
is tranlated to a linear displacement of the screw which is transferred to the application
via the tip of the screw.
What applications can they be used for?
Any ‘set-and forget’ application, particularly where space is tight. The primary function
of the PIA series actuators is relative position and hold, whereby switching the
controller off will result in the same drift as a 1/4-80 fine drive screw.
The step size is dependant upon drive screw preload, and will differ between
actuators and applications. They are not suitable where repeatable step size is
required.
What is the lifetime of the typical piezo inertial motor?
The piezo stack of the actuator is rated for a service life of over a billion steps. With
proper maintenance (see Section 4.2.) the wear performance of the hard coating on
the drive screw should endure for this life time, however up to a 30% drop in step size
may be experienced.
What driver can I use?
The piezo inertia actuators are designed to be driven by the Thorlabs KIM101 Inertia
Piezo Driver.
What is the maximum length of cable?
The actuators are shipped with 1m (3.3’) of cable. Thorlabs offer 1.5m (PAA101)
extension cables and male adapters (T5026) to extend this length to 2.5m, see
www.thorlabs.com. Due to the capacitance of the cables, do not use cables longer
than 2.5 m in total.
