Physik Instrumente PI WP Pi1124 Piezo Linear Drives For Laser Technology

PI_WP_pi1124_Piezo_Linear_Drives_for_Laser_Technology Whitepapers & Success Stories

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WHITEPAPER – Piezo Linear Drives for Laser Technology

Steffen Arnold

Page 1 of 5

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

Piezo Linear Drives for Laser Technology

Automatic Mirror Positioning in Vacuum and in Inaccessible Places

WHITEPAPER – Piezo Linear Drives for Laser Technology

Steffen Arnold

Page 2 of 5

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

Lasers are versatile tools with a wide range of

applications. For example, in material processing they

are nowadays as indispensable as they are in medical

technology or in material and environmental research.

Everywhere the principle is the same: Tip/tilt mirrors

ensure correct guidance of the laser beam.

This makes them important components, which,

however, have to be positioned accurately, in order to

achieve the desired result. Here manual setting is mostly

still the state of the art. But manual adjustment is not

always possible, for example, when tilt/tip mirrors are

used in a vacuum or are mounted in inaccessible places

where they have to be preset before start-up or

readjusted. This is where piezo-based linear drives can

provide a solution: These space-saving and low-cost

microdrives work with a positioning accuracy down to the

nanometer range and – when installed in a mirror mount

– replace the manually actuated micrometer screws.

Fig. 1 Customized mirror mount for large optics.

These mechanical systems can also be automated with

PiezoMike drives (Image: Liop-Tec)

The Liop-Tec GmbH has shown by way of a good

example how the positioning of tip/tilt mirrors,

indispensable for laser technology, can be automated

optimally adapted to the application.

Fig. 2 The mirror mounts are now also being offered

with piezo drives instead of micrometer screws (Image:

Liop-Tec)

The company offers standard and customized mirror

mounts (Fig. 1), which can now optionally also be

equipped with piezo drives instead of manual micrometer

screws (Fig. 2).

"In collaboration with Physik Instrumente (PI), we have

developed piezo-based linear actuators to series-

production level and, in doing so, adjusted the screw and

nut to the requirements of the drive principle.

WHITEPAPER – Piezo Linear Drives for Laser Technology

Steffen Arnold

Page 3 of 5

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

The PiezoMike drives from PI have been integrated

successfully into the mirror mount concept of our Star

series," explains Patrick Incorvaia, Sales Manager at

Liop-Tec (Fig. 3).

Fig. 3 Patrick Incorvaia, Sales Manager at Liop-Tec

(Image: Liop-Tec)

The piezomotors based on the inertia principle are

operated at a frequency of up to 2 kHz. The PiezoMike

linear actuator achieves forces of up to several 10 N, can

be easily integrated into a wide range of applications and

are also suitable for vacuum applications (Fig. 4) "We

are particularly proud of being able to offer mirror mounts

for high- and ultra-vacuum that are adjustable from

outside with extremely high precision," continues Patrick

Incorvaia. "The outstanding collaboration with PI has

brought us a good step forward." The manual positioning

screw is simply exchanged for a PiezoMike.

Fig. 4 PiezoMike linear actuator: Minimum

dimensions, high force and stable positioning under

vacuum conditions (Image: PI)

Operating Principle and Adjustment

Piezo-based inertia drives utilize the stick-slip effect for

fine steps with step sizes of just a few micrometers. In

the first part of the motion cycle, the actuator expands

slowly taking along the moving rod (stick effect).

In the second part of the motion cycle, the actuator

contracts so rapidly that it slides along the moved rod,

which cannot follow this rapid motion due to its inertia,

and thus remains in the same position (slip effect). The

electric control is easy; its output signal is similar to a

saw-tooth voltage. The drives are small, which makes

them suitable for many application areas.

Typical fields of application for this drive principle can be

found not only in laser technology, but also range from

solder tip positioning to shutter and membrane

adjustments in micromanipulation.

Fig. 5 Piezo-based inertia drives utilize the stick-slip

effect for fine steps with step sizes of just a few

micrometers (Image: PI)

The operating principle of the inertia drive has been

adapted to the requirements of the application by the

development partners PI and Liop-Tec (Fig. 5):

In this case, the stick effect does not take along a

moving rod but causes a screw to rotate.

The claw, which grasps around the screw, opens with

the expansion of the actuator and causes the screw to

slightly turn.

WHITEPAPER – Piezo Linear Drives for Laser Technology

Steffen Arnold

Page 4 of 5

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

Once the maximum expansion of the actuator has been

reached, the actuator contracts quickly and the claw

moves back to its initial position, but does not take along

the screw, which due to its inertial mass, remains in its

position (slip effect). This step cycle is repeated, causing

the screw to continue its rotation until the desired

position is reached. The motion sequence works, of

course, also in the opposite direction. "Nevertheless, it

has been a lengthy process to find out the optimum

material parameters for the slip effect, which required a

lot of know-how in the manufacture of the screw and nut.

The implementation also required very stringent

tolerance and surface quality requirements for the

mechanical components," says Patrick Incorvaia.

Thanks to their compact dimensions, the inertia drives

can be integrated in a space-saving manner.In addition,

these drives also have other advantages.

Fig. 6 The E-870 driver (Figure 6), specifically tuned

to the requirements of linear actuators, controls the

actuator. One driver can serially control a unit with up to

four channels, keeping investment costs low (Image: PI)

The piezo solution is not only much smaller than any

motor-driven micrometer screw available on the market,

but the PiezoMike linear actuator also works with a very

high resolution. Step widths of approx. 20 mm can hardly

be achieved using traditional stepper motor drives.

In doing so, the piezo-based linear drive develops a feed

force of 22 N, works at a maximum speed of 3 mm/min

and is designed for travel ranges from 7.5 mm to 26 mm.

Furthermore, their life expectancy of more than one

billion steps is quite impressive. Converted, this would

correspond to a working range of 20 m or to 100 hours of

continuous operation. This is more than sufficient given

the small travel ranges of a few micrometers, the short

control times and the comparably rare motions.

Control and Fine Adjustment

The E-870 driver (Fig. 6), specifically tuned to the

requirements of linear actuators, controls the

actuatorOne driver can serially control a unit with up to

four channels, keeping investment costs low. For fine

adjustment, the piezo linear motors inserted into the

mirror mounts can also be operated in analog mode:

Here, the "stick phase" is more or less stopped in the

last positioning phase and the piezo actuator is operated

within the rising edge of the piezo actuator voltage and

not in full-step mode. In this way, a positioning resolution

of 5 nm can be achieved. The driver behaves then like a

piezo voltage amplifier.

The development of high-precision PiezoMike drives will

be pursued. Patrick Incorvaia is already looking forward

to the continued collaboration with PI: "High-speed,

noiseless direct drives (Fig. 7) and position-regulated

variants currently in preparation should make our mirror

mounts even more flexible in the future."

Fig. 7 Rod drive with piezoelectric stick-slip drive. The

drive principle can be modified, depending on the

application (Image: PI)

WHITEPAPER – Piezo Linear Drives for Laser Technology

Steffen Arnold

Page 5 of 5

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

Author

Steffen Arnold Head of "Marketing and Products" at

Physik Instrumente (PI) GmbH & Co. KG

About Liop-Tec

The LIOP-TEC GmbH with its headquarters in

Radevormwald near Cologne, Germany, was

established in 2012 by Dr. Jürgen Lindener-Roenneke

and Privatdozent Dr. Michael Gutmann. Both can build

on more than two decades of experience in laser

technology. It should not come as a surprise, then, that

the newly established company has an excellent

reputation in the area of innovative laser technology and

optomechanical components. Today the company's

focus is on custom laser applications, especially in the

area of molecular science, material and environmental

science, general science and medical technology.

About PI (Physik Instrumente)

In the past four decades, PI (Physik Instrumente) with

headquarters in Karlsruhe, Germany has become the

leading manufacturer of nanopositioning systems with

accuracies 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, from design right down to

shipment: precision mechanics and electronics as well

as 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 for

ultrahigh vacuum applications as well as parallel-

kinematic 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 and

positioning systems