High-precision and large-stroke XY micropositioning stage based on serially arranged compliant mechanisms with flexure hinges. - In: Precision engineering, Bd. 72 (2021), S. 469-479
Compliant mechanisms are state of the art in micropositioning stages due to their many beneficial features. However, their design usually compromises between motion range, motion accuracy and design space, while mechanisms with distributed compliance are mostly applied. The further use of flexure hinges with common notch shapes strongly limits the stroke in existing high-precision motion systems. Therefore, this paper presents a high-precision compliant XY micropositioning stage with flexure hinges capable of realizing a motion range of ± 10 mm along both axes. The stage is based on a novel plane-guidance mechanism, which is optimized to realize a precise rectilinear motion of the coupler link while keeping the rotation angles of all hinges below 5˚. The XY motion is then achieved by coupling two of these mechanisms in a serial arrangement. Next, the synthesis of the monolithic XY stage is realized by replacing all revolute joints of the rigid-body model with flexure hinges using optimized power function notch shapes. Emphasis is also placed on the embodiment design of the stage and the actuator integration to minimize possible error sources. Finally, the quasi-static behavior of the compliant stage is characterized by a simulation with a 3D FEM model and by an experimental investigation of a prototype. According to the results, the developed compliant XY micropositioning stage achieves a maximum positioning deviation of less than 10 [my]m in both axes and a yaw error of less than 100 [my]rad over a working range of 20 mm × 20 mm with a comparably compact design of the compliant mechanism of 224 mm × 254 mm.
https://doi.org/10.1016/j.precisioneng.2021.02.001
Experimental setup for the investigation of reproducibility of novel tool changing systems in nanofabrication machines. - In: Nanomanufacturing and metrology, ISSN 2520-8128, Bd. 4 (2021), 3, S. 181-189
Nanomeasuring machines developed at the Technische Universität Ilmenau enable three-dimensional measurements and manufacturing processes with the lowest uncertainties. Due to the requirements for these processes, a highly reproducible and long-term stable tool changing system is needed. For this purpose, kinematically determined couplings are widely used. The state-of-the-art investigations on those are not sufficient for the highest demands on the reproducibility required for this application. A theoretical determination of the reproducibility based on analytical or numerical methods is possible, however not in the desired nanometer range. Due to this, a measurement setup for the determination of the reproducibility in five degrees of freedom with nanometer uncertainty was developed. First, potential measuring devices are systematically examined and measurement principles were developed out of this. A three-dimensional vector-based uncertainty analysis is performed to prove the feasibility of the measurement principle and provides a basis for further design. As a result, a translatory measurement uncertainty of 10 nm and a rotatory uncertainty of 11 nrad can be reached. Afterwards, the measurement setup is designed, focusing on the metrological frame and the lift-off device. The developed setup exceeds the uncertainties of the measurement setups presented in the state-of-the-art by an order of magnitude, allowing new in-depth investigations of the reproducibility of kinematic couplings.
https://doi.org/10.1007/s41871-021-00103-9
Fundamental investigations in the design of five-axis nanopositioning machines for measurement and fabrication purposes. - In: Nanomanufacturing and metrology, ISSN 2520-8128, Bd. 4 (2021), 3, S. 156-164
The majority of nanopositioning and nanomeasuring machines (NPMMs) are based on three independent linear movements in a Cartesian coordinate system. This in combination with the specific nature of sensors and tools limits the addressable part geometries. An enhancement of an NPMM is introduced by the implementation of rotational movements while keeping the precision in the nanometer range. For this purpose, a parameter-based dynamic evaluation system with quantifiable technological parameters has been set up and employed to identify and assess general solution concepts and adequate substructures. Evaluations taken show high potential for three linear movements of the object in combination with two angular movements of the tool. The influence of the additional rotation systems on the existing structure of NPMMs has been investigated further on. Test series on the repeatability of an NPMM enhanced by a chosen combination of a rotary stage and a goniometer setup are realized. As a result of these test series, the necessity of in situ position determination of the tool became very clear. The tool position is measured in situ in relation to a hemispherical reference mirror by three Fabry-Pérot interferometers. FEA optimization has been used to enhance the overall system structure with regard to reproducibility and long-term stability. Results have been experimentally investigated by use of a retroreflector as a tool and the various laser interferometers of the NPMM. The knowledge gained has been formed into general rules for the verification and optimization of design solutions for multiaxial nanopositioning machines.
https://doi.org/10.1007/s41871-021-00102-w
Design of an electrostatic balance mechanism to measure optical power of 100 kW. - In: IEEE transactions on instrumentation and measurement, ISSN 0018-9456, Bd. 70 (2021), 7002909, insges. 9 S.
https://doi.org/10.1109/TIM.2021.3060575
Measurement uncertainty analysis on a five-axis nano coordinate measuring machine NMM-5D following a vectorial approach :
Messunsicherheitsbetrachtungen an einem fünfachsigen Nano-Koordinatenmessgerät NMM-5D nach einem vektoriellen Ansatz. - In: Technisches Messen, ISSN 2196-7113, Bd. 88 (2021), 2, S. 61-70
Dieser Beitrag zeigt ein Konzept für eine fünfachsige Nano-Koordinatenmessmaschine zur Messung auf stark gekrümmten asphärischen und frei geformten optischen Oberflächen in einem Messvolumen von 25mm × 25mm × 5mm mit einem maximal möglichen Neigungswinkel von bis zu 60˚ zur Hochachse und einer maximalen Rotation von 360˚ um die Hochachse. Dabei wird die Probe translatorisch bewegt und der Sensor in seiner Orientierung verändert. Unter Einhaltung des Abbe-Komparatorprinzips für alle Messachsen wird die Bewegungsabweichung des Sensors bei der Rotation durch ein in-situ-Referenzmesssystem erfasst. Dieses besteht aus drei kartesisch angeordneten Fabry-Pérot-Interferometern mit dem Ursprung im Antastpunktes des Sensors, die den Abstand zu einer hemisphärischen Referenzfläche messen. Die Messunsicherheitsbetrachtung des Gesamtsystems erfolgt nach dem guide to the expression of uncertainty in measurement in einem vektoriellen Ansatz und liefert unter konservativen Annahmen eine Unsicherheit des Antastpunktes von maximal 72 nm (k=1).
https://doi.org/10.1515/teme-2020-0092
A novel approach to generate a static torque in the range from 1 mN&hahog;m to 1 N&hahog;m :
Ein neuartiger Ansatz zur Erzeugung eines statischen Drehmoments im Bereich von 1 mN&hahog;m bis 1 N&hahog;m. - In: Technisches Messen, ISSN 2196-7113, Bd. 88 (2021), 2, S. 103-113
Drehmomentsensoren mit einem kleinen Messbereich bis zu 1 N&hahog;m sind Teil verschiedener Präzisionsgeräte, wie beispielsweise Roboter oder Werkzeuge für medizinische Operationen und Nanofabrikationsgeräte. Die Drehmomentsensoren benötigen häufig eine Kalibrierung, für die eine Rückführbarkeit nachgewiesen werden muss. Gemäß gesetzlichem Auftrag haben die nationalen metrologischen Institute die Aufgabe, die Drehmomenteinheiten zu realisieren und die geforderte Rückführbarkeit zu ermöglichen. Dieser Artikel zeigt, wie nach einem neuen Prinzip statische Drehmomente im Bereich von 1 mN&hahog;m bis 1 N&hahog;m erzeugt werden können. Ziel der laufenden Arbeiten war die Umsetzung dieser neuen Idee der Drehmomenterzeugung zur Schaffung einer neuen, präziseren Drehmoment-Normalmesseinrichtung. Die Leistungsfähigkeit der neuen Methode wurde mit der Erzeugung von statischen Drehmomenten nach dem Stand der Technik (PTB-Drehmoment-Normalmesseinrichtung) verglichen.
https://doi.org/10.1515/teme-2020-0090
A novel planar two-axis leaf-type notch flexure hinge with coincident rotation axes and its application to micropositioning stages. - In: Microactuators, microsensors and micromechanisms, (2021), S. 1-14
Compliant mechanisms with flexure hinges are well-suited for high-precision applications due to their smooth and repeatable motion. However, the synthesis of planar compliant mechanisms based on notch flexure hinges is mostly limited to the use of single-axis hinges due to the lack of certain multiple-axis flexure hinges. This contribution introduces a novel planar leaf-type notch flexure hinge with two coincident rotation axes based on circular pre-curved leaf springs. A generally suitable hinge geometry is determined through a parametric study using the finite element method (FEM). Finally, the two-axis flexure hinge is applied and investigated for the use in two planar micropositioning stages for the rectilinear guidance of an output link with a large centimeter stroke. The presented two-axis flexure hinge turns out to be a suitable approach to monolithically connect three links of a compliant mechanism in a planar and precise way.
https://doi.org/10.1007/978-3-030-61652-6_1
Characterization of thin flexure hinges for precision applications based on first eigenfrequency. - In: Microactuators, microsensors and micromechanisms, (2021), S. 15-24
Flexure hinges with small cross-section heights are state of the art in numerous precision engineering applications due to their capability for smooth and repeatable motion. However, the high sensitivity to manufacturing influences represents a challenge. We propose a characterization method for flexure hinges based on the measurement of the free oscillation, to enable the consideration of manufacturing influences in the early stages of the design process. Three semi-circular flexure hinges with different cross-section heights and highly accurate geometry were investigated experimentally to compare them with three theoretical modeling approaches. The results for the three flexure hinge specimens showed small deviations to the predicted values from the models which is in agreement with the results of dimensional measurements. With each modeling approach, a deviation of the minimal notch height from the nominal value can be calculated. This value, in turn, can be used as manufacturing allowance for subsequent manufacturing of compliant mechanisms using the same manufacturing method. An exemplary compliant parallel-crank mechanism proves the applicability of the concept to compliant mechanisms with multiple flexure hinges.
https://doi.org/10.1007/978-3-030-61652-6_2
Optimization of compliant path-generating mechanisms based on non-linear analytical modeling. - In: Microactuators, microsensors and micromechanisms, (2021), S. 25-35
Monolithic compliant mechanisms are often used in precision engineering applications for path-generating tasks due to their many advantages. They are mostly realized with concentrated compliance in form of notch flexure hinges and achieve their motion due to bending of the hinges. This contribution presents the non-linear analytical modeling of compliant mechanisms with power function-based notch flexure hinges and their efficient optimization of the elasto-kinematic path-generating properties using MATLAB. Different planar mechanisms are analytically characterized with the theory for large deflections of curved rod-like structures. A verification of the analytical model is exemplified by FEM simulations for a four-hinge Watt mechanism as a point guidance mechanism and for a 12-hinge pantograph mechanism as a plane guidance mechanism. Further, the exponents of the power function contours for each hinge are individually optimized on the example of an Evans and a Roberts mechanism. This is achieved with the goal of minimizing the straight-line deviation of their coupler points realizing a stroke of 10 mm.
https://doi.org/10.1007/978-3-030-61652-6_3
Conceptual design of a microscale balance based on force compensation. - In: Microactuators, microsensors and micromechanisms, (2021), S. 103-114
Macroscopic electromagnetic force compensation (EMFC) balances are well established but were not yet demonstrated within microsystems. Hence, in this paper, the concept and the design of a micro fabricated force compensation balance is presented. The implemented concentrated compliance mechanism in form of flexure hinges enables motion with high precision, which is combined with a force compensation mechanism. The concept of force compensation promises a high measurement range, which is expected to be up to 0.5 mN, while still enabling a high resolution of less than 8 nN. The developed dynamic model of the miniaturized balance is used for the design of a PID-controller strategy. Here, continuous and time-discrete controller approaches are compared. The time-discrete controller with realistic delay times, leads to an accuracy of the controller, which is better than the expected accuracy of the integrated capacitive position sensor.
https://doi.org/10.1007/978-3-030-61652-6_9