This work deals with various investigations into the accuracy of a newly developed planar nanopositioning machine. This machine, called Nanofabrication Machine 100 (NFM-100), has a positioning range of 100 mm in diameter. To determine the precision, various movement scenarios are performed with the machine table, and the trajectory deviation from the set trajectory is determined. In particular, the focus is on high velocities of up to 20 mm/s. Even at high speeds in the range of several millimetres per second, this machine can impress with its performance and only has a deviation in the nanometre range.
High technology applications for example in the semiconductor or the optical industry require positioning systems providing repeatability and uncertainty in the range of nanometers together with x-, y-travel ranges of several hundreds of millimeters. We contribute in this research by investigating the applicability of integrated planar direct drives for the realization of nanopositioning- and nanomeasuring machines (NPM/NMM). The paper introduces the concept of planar integrated direct drives and explains the engineering design of the realized system for a 100 mm circular travel range in x and y. It presents the drive system parameters and the arrangement and interaction of the main components. The results of the initial operation are presented with a special focus on the question how the closed loop system can be taken into operation with a free floating slider. The evaluation of the positioning performance leads to the result that a 2D servo error of less than exy = 1.3 nm is achieved at arbitrary positions within the travel range. As a result of repeated step response tests, the positioning resolution is 0.5 nm. The measurement of the coincidental z-movement of the aerostatically supported slider yields a z-vibration with a standard deviation of σz = 0.45 nm. Regarding the drive system these results represent the limit of what can be reached with this setup as the measured error motions are in the range of the noise of the fixed environment setup. By measuring the characteristics of the aerostatic slider support at the fully assembled system the present air bearing stiffness is determined and based on a FEM-simulation of the slider eigenfrequencies the influence on the force transfer behavior is expected to be only marginal.
Zusammenfassung: In der vorliegenden Arbeit werden zwei Nanopositioniersysteme in Bezug auf ihre Positioniergenauigkeit während der Bewegung verglichen. Beide Systeme besitzen einen planaren Bewegungsbereich von ≥ 100 mm, werden durch Linearmotoren angetrieben und die Position wird durch Laserinterferometer gemessen. Groẞe Unterschiede existieren jedoch im mechanischen Aufbau. Das erste Positioniersystem ist ein zweiachsiger Demonstrator dessen zwei Läufer auf Wälzkörpern gelagert sind. Dies führt zu dem Problem der besonders im Nanometerbereich stark nichtlinearen Reibung. Bei dem zweiten Positioniersystem kommen Luftlager zum Einsatz und darüber hinaus handelt es sich nur um einen Läufer, welcher drei Freiheitsgrade besitzt. Es wird gezeigt, dass durch regelungstechnische Methoden der Reibkraftkompensation die Positioniergenauigkeit beider Systeme bis zu einer Geschwindigkeit von ca. 1 mm/s vergleichbar ist. Schlüsselwörter: Nanopositionierung, Reibungsmodellierung, Positioniergenauigkeit.Abstract: This work compares two fine positioning stages in relation to positioning accuracy during motion. Both systems have a working range of ≥ 100 mm, are driven by linear motors and the position is measured by laser interferometers. However the mechanical setting is quite different. The first system is a two axis fine positioning stage which is supported by ball bearing guides. This leads especially in nanometer range to problems caused by the highly nonlinear friction. In the second system air bearings are used. It can be shown, that by dint of model based control design the position accuracy is comparable until a velocity of 1 mm/s.
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