WHITEPAPER – TECHNICAL PROGRESS WITH ULTRASONIC PIEZOMOTORSSteffen Arnold

Technical Progress with Ultrasonic Piezomotors
Precise, Fast, Energy-Saving and Compact

Physik Instrumente (PI) GmbH & Co. KG_Auf der Roemerstrasse 1_76228 Karlsruhe, Germany
Tel. +49 721 4846-0, Fax +49 721 4846-1019 Email info@pi.ws, www.pi.ws

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WHITEPAPER – TECHNICAL PROGRESS WITH ULTRASONIC PIEZOMOTORSSteffen Arnold

Choosing the right drive system can be a decisive

Total stations are the most frequently used surveying

criterion in differentiating oneself from competitors.

instruments for angle and distance measurement in

Numerous factors influence the choice: The installation

geodesy. One of the world’s leading manufacturers ofspace available, the speeds and accelerations required

such precision instruments is Leica Geosystems AG with

as well as the necessary positioning accuracy, theheadquarters in Heerbrugg in Eastern Switzerland andenergy consumption and not least the reliability of theGerman sales offices in Munich, Berlin, Karlsruhe andmotor selected. If the requirements increase, ultrasonic

Düsseldorf. The company has almost 200 years ofpiezomotors can now be used as practical alternatives toexperience

inclassic DC stepper motor combinations. The application

instruments

andcontinues

toimpress

described below provides a typical example of this.

innovations.

Even

today

–

severalUltrasonic piezomotors provide an as yet unrivaled

generations after the introduction of the first high-speed and acceleration for the latest total stations usedprecision WILD T3 theodolite more than 75 years ago –inprecision

geodesy

athighresolution

andlowpower

consumption.

andthefieldreliabilityofgeodetic

arethemostmeasuringwithitsinstrument

importantcharacteristics of the company's products. The Swiss
specialists are also demonstrating this with their mostrecent development, the Leica TS30 total station (Fig. 1),
which sets new standards of precision and reliability inangle and distance measurement.

Geodetic Total Station Belongs to a
New Generation
The angular measuring accuracy of the new Leica TS30
total station is 0.5” (according to ISO 17123-3) and thedistance measuring accuracy is 0.6 mm + 1 ppm(according to ISO 17123-4) for measurements on Leicaroundprisms(GPH1P)and

2 mm+2 ppm

formeasurements on arbitrary, natural surfaces. In addition
to the measuring accuracies, it is the performance of thetotal station with respect to short positioning andmeasuring times which is a decisive criterion for theuser. This is where the motorization of the new Leica
TS30 convinces, with its high accelerations, high speeds
andprecise start-up behaviorofinstrumentandtelescope. It thus combines the most accurate angle anddistance measurements with optimized automation of themeasuring processes. Surveyors all over the worldFig. 1 The new Leica TS30 total station sets new
standards for precision and reliability in angle anddistance measurement. The drive solution also plays its
part here (Image: Leica Geosystems AG, Switzerland)

appreciate this. Such technological progress, however,
could not have been achieved with conventional drive
technology.

Physik Instrumente (PI) GmbH & Co. KG_Auf der Roemerstrasse 1_76228 Karlsruhe, Germany
Tel. +49 721 4846-0, Fax +49 721 4846-1019 Email info@pi.ws, www.pi.ws

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WHITEPAPER – TECHNICAL PROGRESS WITH ULTRASONIC PIEZOMOTORSSteffen Arnold

The installation space available is very limited (Fig. 2),

Moreover, the noise inevitably generated can benevertheless the requirement is for speeds of at least

undesirable in some fields of application, e. g. where the180 degrees per second, four times the previous norm,

instruments operate round the clock for monitoringat high acceleration and short positioning times. These

measurements in residential areas or inner city locations.

requirements in combination with the desired positioning
accuracy and the demands concerning the reliability
when used outside under meteorologically challenging
environmental

conditions

required

future-oriented,

alternative drive solutions.

Magnetic direct drive solutions are available alongsideconventional stepper motor solutions in the surveying
instrument market. Since magnetic drive technology
lacks the natural mechanical stopping force which isnecessary for precision measurements, this friction must

In the application described, the speed reduction gears

be generated electrically, which leads to high energy

required by typical DC or stepper motors can become

consumption and undesirable heat effects in mobile use.

the weak point, because mechanical components
naturally always suffer wear.

Fig. 2 The cross-section through the total station shows the limited installation space available for the drives(Image: Leica Geosystems AG, Switzerland)
Physik Instrumente (PI) GmbH & Co. KG_Auf der Roemerstrasse 1_76228 Karlsruhe, Germany
Tel. +49 721 4846-0, Fax +49 721 4846-1019 Email info@pi.ws, www.pi.ws

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WHITEPAPER – TECHNICAL PROGRESS WITH ULTRASONIC PIEZOMOTORSSteffen Arnold

Piezo Ultrasonic Drives Produce theRotational Movements
Direct drives operating on the piezo principle were
therefore chosen for the vertical and the horizontal
motion of the measuring optics of the total station. They
allow an as yet unrivaled speed (of more than 180°/s)
and high accelerations (up to 360°/s²). The drives are
self-locking, i.e. they generate high holding forces evenwhen no electrical power is applied. They also run
almost noiselessly, are maintenance free and operate atambient temperatures between -20 °C and + 50 °C. The
ultrasonic piezo drives used in the total station havebeen developed by PI (Physik Instrumente), a company
with more than 40 years of experience in the field of
micropositioning and nanopositioning technology which
is now one of the leading companies in the globalmarket.

Fig. 3 The rotations are produced by two ultrasonicmotors which are preloaded tangentially against a friction
ring. The friction ring is pivot mounted (Image: Leica
Geosystems AG/ Physik Instrumente (PI))
In operation, the ceramic piezomotors then oscillate
synchronously

withultrasonicfrequencies.

Theoscillation displaces the friction tip. This in conjunction

The operating principle of the ultrasonic piezo drives

with the preloading produces a feed motion for theused for the vertical and horizontal rotation of thefriction ring. Since no mechanical components, such asmeasuring optics is simple to understand (Fig. 3). Eachgears for the power transmission, are necessary, therotation is generated by two ultrasonic motors, which aredrive operation is almost wear-free and very reliable. In

tangentially preloaded against a friction ring. The friction

addition, the drive solution is easy to integrate. It is justring is pivot mounted. The preloaded force against theas easy and effective to realize linear motions withring clamps the drive when at rest; the positional jitter

ultrasonic piezomotors. The tangential drive principle isthat can be observed in the case of magnetic directthen applied to a linearly-tracked friction bar (Fig. 4).

drives is therefore also absent here.

Fig. 4 It is just as easy and effective to realize linear motions with ultrasonic piezomotors. The tangential drive principle isthen applied to a linearly-tracked friction bar (Image: Physik Instrumente (PI))

Physik Instrumente (PI) GmbH & Co. KG_Auf der Roemerstrasse 1_76228 Karlsruhe, Germany
Tel. +49 721 4846-0, Fax +49 721 4846-1019 Email info@pi.ws, www.pi.ws

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WHITEPAPER – TECHNICAL PROGRESS WITH ULTRASONIC PIEZOMOTORSSteffen Arnold

Applications Galore
Ultrasonic piezomotors are therefore suitable for a large
number of further applications where small size, highspeeds and reliability are also the decisive factors.
Stages for biohandling or microscopy are available, forexample, which excel by having a particularly low-profile
and a design which can easily be integrated (Fig. 5).

Examples of typical industrial applications range from themanufacture of semiconductors and photonics throughgeneral handling tasks to metrology and medicalengineering. As the described application illustrates,
ultrasonic piezomotors continue to expand into newfields of application, one can only guess as to which of
the applications will provide the next contribution toadvancing the technical development even further.

Ultrasonic Piezomotors: Small andFast
In ultrasonic piezo drives, a piezo ceramic oscillating athigh frequency is preloaded against a friction bar, a
traveling wave generating the feed. The drive is simple inits set-up and consists of a piece of ceramic, a spring
and the friction element, which is normally fixed to themoving part, a tracked slider, for example. This results inlightweight, maintenance-free drives which are suitablefor driven speeds up to 0.5 m/s and high accelerations.
They open up many areas of application – mainly
because of their low-profile, compact size – because
Fig. 5 Biodispenser and microscopy XY stage with®
ultraflat PILine ultrasonic piezomotors. Their low heightmeans they are simple to integrate into the existingassembly (Image: Physik Instrumente (PI))

they are often a more practical replacement for classic
motor

leadscrew

combinations.

The

self-locking

ultrasonic motors act directly without intermediate
elements such as leadscrews or gears and are free fromhysteresis errors. Since they are also offered in various
integration stages (Fig. 6), they can be adapted well tothe respective application.

Fig. 6 Piezo ultrasonic drives are offered in various stages of integration. They can thus be adapted well to the respective
application (Image: Physik Instrumente (PI))

Physik Instrumente (PI) GmbH & Co. KG_Auf der Roemerstrasse 1_76228 Karlsruhe, Germany
Tel. +49 721 4846-0, Fax +49 721 4846-1019 Email info@pi.ws, www.pi.ws

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WHITEPAPER – TECHNICAL PROGRESS WITH ULTRASONIC PIEZOMOTORSSteffen Arnold

AuthorSteffen Arnold Head of "Marketing and Products" atPhysik Instrumente (PI) GmbH & Co. KG

About PI (Physik Instrumente)
In the past four decades, PI (Physik Instrumente) with
headquarters in Karlsruhe, Germany has become theleading manufacturer of nanopositioning systems withaccuracies in the nanometer range.
With four company sites in Germany and ten sales andservice offices abroad, the privately managed company
operates globally. Over 700 highly qualified employees
around the world enable the PI Group to meet almost
any requirement in the field of innovative precision
positioningtechnology.

Allkeytechnologies

aredeveloped in-house. This allows the company to control
every step of the process, from design right down toshipment: precision mechanics and electronics as wellas position sensors.
The required piezoceramic elements are manufactured
by our subsidiary PI Ceramic in Lederhose, Germany,
one of the global leaders for piezo actuator and sensor
products. PI miCos GmbH in Eschbach near Freiburg,
Germany, is a specialist for positioning systems forultrahigh vacuum applications as well as parallelkinematic positioning systems with six degrees offreedom and custom-made designs.

Physik Instrumente (PI) GmbH & Co. KG_Auf der Roemerstrasse 1_76228 Karlsruhe, Germany
Tel. +49 721 4846-0, Fax +49 721 4846-1019 Email info@pi.ws, www.pi.ws

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