PiezoWalk® Walking Drives

Nanometer Precision with a High Feed Force

PiezoWalk® OEM drives are compact and powerful, from the left, N-331, N-310, N-216 — PiezoWalk^® OEM drives are compact and powerful, from the left, N-331, N-310, N-216

Scalable travel range due to scalable runner length
Resolution to 0.03 nm
Self-locking when at rest, no heat generation
Nonmagnetic and vacuum-compatible operating principle
Three technologies: NEXLINE^®, NEXACT^® and PICMAWalk
Integration levels from an OEM motor to a multi-axis positioning system

PiezoWalk® drives were developed more than 10 years ago for the semiconductor industry, which is a very demanding industry when it comes to reliability, position resolution and long-term stability. PI received the SEMI Technology Innovation Showcase Award for the PiezoWalk® technology in 2005. The drives are continuously developed further, and a large number of variants are now available for different areas of application.

After a run-in phase of over 10 – 15 km, the drive achieves an exceptionally stable step size. The constant step size is a measure for the high load capacity and endurance of the drive.

Piezo walking drives do not require any additional mechanical coupling elements. The piezo drive acts directly on the runner. There are no other moving parts that would limit the precision and reliability. That is an advantage compared to motor-spindle systems, where connectors and gearheads need to be used.

Preloading the piezoelectric actuators against the runner ensures self-locking of the drive when at rest and powered down. As a result, it does not consume any power, does not heat up, and keeps the position mechanically stable. Applications with a low duty cycle that require a high time and temperature stability profit from these characteristics.

The motion of the piezoceramic actuator is based on crystalline effects and is not subject to any wear. Unlike other piezomotor principles, the coupling of the piezo actuators to the runner is not subject to sliding friction effects; the feed is achieved by the physical clamping and lifting of the actuators.

PICMAWalk drives have already proved their endurance over 100 km continuous running under load (standard test environment under normal atmospheric conditions).

Piezomotors from PI are vacuum-compatible in principle and suitable for operation under strong magnetic fields. For these purposes, special versions of the drives are offered. Piezo walking drives can also be used in clean rooms or in environments with a hard ultraviolet radiation.

Characteristics of stepping drives

Constant velocity and smooth driving of a NEXLINE® drive are best achieved in nanostepping mode, but the maximum attainable velocity is higher in full-step mode as a result of the 1 nm open-loop motions of a NEXLINE® drive.

PI Diagram Position/Time NEXLINE® Drive

Sequence of open-loop 1 nm motions of a NEXLINE® drive.

PiezoWalk® walking drives cover a wide range of forces and velocities. This makes it possible to serve a broad spectrum applications

PICMAWalk drives achieve feed forces up to 50 N and holding forces to 60 N. The maximum velocity is 15 mm/s.

PICMAWalk uses the proven PICMA® multilayer piezo actuators. That means lower piezo voltages to 120 V. PICMA® piezo actuators also ensure a long lifetime and the outstanding reliability of the PICMAWalk technology.

PICMAWalk

High-load walking drives combine piezo clamping and shear actuators, in order to move a rod. The drives feature particularly high forces and stiffnesses at feed forces of several 100 N. They are capable of dynamically compensating oscillations in the range of a few micrometers with nanometer resolution, are designed for higher positioning and holding forces of up to 800 N, and work at lower velocities.

NEXLINE®

Precision walking drives convert the walking motion by means of piezo bending elements. These drives are more compact and achieve higher velocities, developing forces in the range from 10 to 20 N.

A suitable selection of the piezo elements optimizes step size, clamping force, velocity, and stiffness for the respective applications.

NEXACT®

As essential components, these piezo walking drives have several piezo actuators that are preloaded against a guided runner.

These piezo actuators perform a walking motion during operation that causes a forward feed of the runner. The piezo actuators can be operated to perform very small walking and feed motion so that a high motion resolution of far below one nanometer is achieved.

Operating principle of PICMAWalk V8 motors

Operating principle and operating modes of NEXLINE® and NEXACT® walking drives

Others

Selection guide for the best solution

Version / Date

POS14E

pdf - 1 MB

English