Q u ick Facts
Actuator Designs
Note Piezomotors are used where evenlonger travel ranges are required.
Piezomotors can be divided into
two main categories: This section gives a brief summaryof the properties of piezoelectric
drives and their applications. Fordetailed information, see “Funda-mentals of Piezoelectricity” begin-
ning on p. 4-13. Stack actuators Piezo tube actuators are the most com-mon and can generate the highest
forces. Units with travel ranges up
to 500 µm are available. To protect
the piezoceramic against destruc-tive external conditions, they areoften provided with a metal casing
and an integrated preload spring to
absorb tensile forces. exploit theradial contraction direction, and
are often used in scanning micro-scopes and
micropumps.
® linear drives (see p. 10-3 Bender and bimorph actuators Shear elements use the inverse-piezo-effect shear component and
achieve long travel and high force. ff. ) offer high positioning andholding forces (up to hundreds of
newtons) with moderate speeds
and resolutions in the subnanome-
ter range.All implementations are self-lock-ing when powered down. achieve travel ranges in the mil-
limeter range (despite their com-
pact size) but with relatively low
force generation (a few newtons). Ultrasonic Motors (Fig. 2a) Piezo-Walk
® Motors (Fig. 2b)The motion of ultrasonic piezomo-tors is based on the friction
between parts oscillating with
microscopic amplitudes. Linear
ultrasonic motors are very compactand can attain high speeds com-
bined with resolutions of 0.1 µm orbetter. Rotary motors feature hightorques even at low rpm. Piezo-Walk ff. For more information, see pp. 4-39 Guided piezo actuators (1 to 6axes) are complex nanopositionerswith integrated piezo drives andsolid-state, friction-free linkages
(flexures). They are used when
requirements like the following
need be met: Extremely straight and flat
motion, or multi-axis motion
with accuracy requirements in the sub-nanometer or sub-micro -radian range Isolation of the actuator from
external forces and torques, pro-
tection from humidity and for-eign particlesSuch systems often also includelever
amplification of up to 20
times the displacement of the piezoelement, resulting in a travel rangeof several hundred µm.
Fig. 1b. Selection of monolithic PICMA ® technology actuators.
Fig. 1a. Selection of classical piezo stack actuators, with adhesive used to join the layers. © PI 1998-2005. Subject to change w/o notice. Cat 118 05/09.17 4-10