WHITEPAPER – HEXAPODS AND THEIR FIELDS OF APPLICATION
Birgit Schulze

From Mechanical Engineering to Particle Accelerators
Hexapods and Their Fields of Application

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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

WHITEPAPER – HEXAPODS AND THEIR FIELDS OF APPLICATION
Birgit Schulze

Today, many automation technology sectors require
highly precise positioning systems.

For multi-axissolutions, parallel-kinematic systems often are theperfect choice. Hexapods are a good example for this,where the travel ranges go from only a few to several
hundred millimeters. Even major loads can be positioned
accurately to the micrometer using Hexapods.
Their advantages compared with serial, i.e. stacked
systems, are that they have much better path accuracy,repeatability and flatness. In addition, the moved mass islow, enabling better dynamic performance, which is thesame for all motion axes. Moreover, cable management
is no longer an issue, because cables are not moved,
and, last but not least, the system features a much morecompact design. These characteristics can be used in a

Integrated in the Automation Line,
with or without PLC
Due to a direct connection to the master control,
Hexapods can be integrated basically in any automatedproduction line in mechanical and plant engineering.
A synchronized clock with other automated components
can easily be achieved, for example, for automatedsupply systems. Consequently, there are numerous
areas of application for Hexapod systems, from metal
cutting to complex alignment processes. Hexapods canbe protected against adverse ambient conditions, forexample by bellows. In this case, they even resist therough ambient conditions in automatic machining units,
where coolants are used for metal cutting processes.

wide range of applications, from mechanical engineeringand robotics to medical technology and research, as we
will show in the applications described in the following.
The product range of PI (Physik Instrumente) includes
powerful six-axis parallel-kinematic systems in numerous
versions. They are suitable for different loads, come withdifferent types of drives and are designed for all kinds ofambient conditions. On request, they can also beordered to communicate directly with a master control
system (Fig. 1).
Fig. 2 Standardized fieldbus interfaces make integrationeasier: Hexapods in automation technology (image: PI)
In such applications, the PLC or CNC can communicate
with the Hexapod system over a standardized real-time
Ethernet interface (Fig. 2). The PLC acts as master anddefines the target position in Cartesian coordinates andthe trajectories; in return, it gets the actual positions also
over the fieldbus interface.
All other calculations required to command the parallelkinematic six-axis system are done by the Hexapod
controller, i.e. transforming the target positions fromFig. 1 Hexapods come in various designs. The modular
design of the Hexapods allows easy adaptation to therequirements of each application (image: PI)

Cartesian coordinates into drive commands for theindividual drives. In this case, the controller acts just likean intelligent drive.

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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

WHITEPAPER – HEXAPODS AND THEIR FIELDS OF APPLICATION
Birgit Schulze

Adaptable and Flexible
Of course, the Hexapod controller can also act as masterfor position control. In this case the PLC only issues aPrecise Positioning with Six
Degrees of Freedom in
Measurement Setups

position command. During the run, the motion cannot be

Quite demanding tasks can be solved with Hexapods: A

synchronized with other drive axes, measuring systems,

good example of this is the following medical researchetc. If there is no parent PLC or if synchronizing withapplication. In this example, an experimental setup isother system components is not required, the Hexapod

used to test how close orthodontic FE models are tocontroller can also control the trajectories based on G-reality and to modify them if necessary.

code according to DIN 66025/ISO 6983 using linear
interpolation. With this method, the Hexapod system canmove the tool smoothly with highest precision during themachining process without causing an oscillation of themechanical structure.

This numerically controlled experimental setup wasdeveloped by scientists of the University of Ulm to findout how the tooth, that is embedded elastically in thejawbone, behaves under stress. The setup can measure
the clinically relevant forces acting on the moving tooth.

Hexapods from PI come in many different designs. A
modular concept allows them to be customized within ashort time. The Hexapod struts are designed so that theirlength can be easily scaled. They include the required
electronics for reference point switch, limit switch,
position sensor and – depending on the motor –electronic commutation. Their standardized joints allow
them to be combined with almost any type of geometry
for base plate and top. To find a suitable solution for acertain task is quite easy, since Hexapods can readily
position and move even major loads of up to several
tons with the high precision that is typical of them.

The biomechanical structure of the simulation system(Fig. 3) is based on a Hexapod with a very compact sizeof only 348 mm in diameter and 328 mm in height. At arepeatability of ±1 µm (Z axis) and ±2 µm (X and Y axes)
and thanks to the high stiffness of the overall system,
this system turns out to be the ideal solution forsimulating the small motions of a tooth in the jawbone. In
addition to that, its pivot point inside and outside thetooth root can be freely defined, a necessary prerequisite
for biomechanical simulation.
The standardized elastic behavior of the periodontal
ligament is simulated by means of a program especiallydeveloped for this purpose. The forces and torques
generated by the orthodontic apparatus to be studied act
on the phantom tooth via the orthodontic bracket andcan be evaluated by scientists.

Sample Manipulation on
Synchrotron Beamlines
Synchrotron

beamlines

arechallenging

potential

applications for Hexapods. In such beamlines, X-ray
diffraction and reflections of the synchrotron radiation
Fig. 3 The force sensor is mounted on the top platform of
the Hexapod. It simulates a real tooth and registers theforces and torques acting there. (image: University ofUlm)

can be used to investigate the structural properties ofthin films as part of modern material research underhigh-vacuum conditions.

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Physik Instrumente (PI) GmbH & Co. KG_Auf der Roemerstrasse 1_76228 Karlsruhe, Germany
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WHITEPAPER – HEXAPODS AND THEIR FIELDS OF APPLICATION
Birgit Schulze

For the direct use of such a beamline, the company

consequence give information on material aging andSURFACE, leading manufacturer of Pulsed Laser

expectable useful life and lifetime.

Deposition systems, has developed an all-in-one systemthat can be used for different types of tests.

Here effects can be proven down to the level of domainor crystal structures. With its high load capacity of up toone ton, the Hexapod carries the entire setup including
the structure where mechanical forces are applied. Herethe Hexapod positions heavy loads, such as cylinder
block, turbine parts, sintering furnaces or cryogenic
chambers as well as welding apparatuses or othermachining tools, over travel ranges of 400 mm with an±1 µm accuracy.
With these examples of application, Hexapods prove

Fig. 4 The Hexapod, designed by PI for use in highvacuum, positions the sample, relative to the incident Xrays. The sample manipulator allows a wide angle rangeof the X-rays due to its small size even at low substrateheights (image: SURFACE)

their versatility, and there are many more fields ofapplication where these precise positioning systems will
display

theirpotential,

rangingfromautomation

technology and robotics to space telescopes or theparticle accelerators described.

For this purpose, the sample manipulator (Fig. 4) holds
the 10 × 10 mm² substrates. The Hexapod, designed by
PI for use in high vacuum, positions the sample, relative
to the incident X-rays. This allows the sample to be tilted
by ±5° around the X and Y axes at a resolution of 0.001°.
Inaddition,

tocompensate

fordifferentlayer

thicknesses, it can be moved in the direction of the Z
axis, i.e., vertically to the sample surface, by up to 3 mm.
Motions of ±6 mm in the X and Y directions allow scansat different positions of the sample surface. The compact
Hexapod, that measures 130 mm in diameter and
115 mm in height, is mounted to a rotary stage and canperform positioning tasks if required.

Heavy Duty Hexapods in MaterialResearchFig. 5 A heavy duty Hexapod is implemented in abeamline for material research. As the "heart" of theexperimental setup, the Hexapod measures materialproperties (image: Physik Instrumente (PI), HelmholtzZentrum Geesthacht (Centre for Materials and CoastalResearch) at DESY, N. Schell)

AuthorIn synchrotron beamlines, also much larger Hexapods
are in use, for example at the DESY research center(German Electron Synchrotron) in the city of Hamburg,
Germany.

Thisheavy-dutyHexapod(Fig.

5)

isimplemented in a beamline for material research.
As the “heart” of the experimental setup, the Hexapod
allows for the measurement of material characteristics,
that occur e.g. during material modelling and inDipl.-Phys. Birgit Schulze, Marketing & Products at PI(Physik Instrumente)
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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

WHITEPAPER – HEXAPODS AND THEIR FIELDS OF APPLICATION
Birgit Schulze

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 and service 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 positioning technology.
All key technologies are developed in-house. This allows
the company to control every step of the process, fromdesign right down to shipment: precision mechanics andelectronics as well as position sensors. The required
piezoceramicelements

aremanufactured

byoursubsidiary 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 of
freedom and custom-made designs.

PI headquarters in Karlsruhe, Germany: More than 350
employees work on high-resolution drive systems andpositioning systems

Page 5 of 5Physik 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