Piezoelectric Ceramic Transducers as Time-Varying Displacement Sensors in Nanopositioners

We present a direct measurement of stage displacement in piezo- driven nanopositioners via piezoelectric (PZT) ceramics. In addition to compactness and affordability, our study shows that within the sensing bandwidth, the sensor is able to track time-varying large signal profiles of stage displacement accurately without utilizing signal conditioning devices. Also, the sensor can be used to capture cross coupling effect in orthogonal axes of motion. For the full-scale range, accuracy of the suggested sensor is less than 27 nm in the sensing bandwidths when the sensor is calibrated with a constant scaling factor. The 3s-resolution of the sensor is 1.9 nm

Use of triple beam resonant gauges in torque measurement transfer standard

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.A new torque transfer standard using metallic TBTF resonant sensor was developed to overcome the overload capability problem which occurs with conventional metallic resistance strain gauges. Previous research work, however, has shown that the first prototype of the metallic TBTF resonant sensor was not suitable for use in a torque transfer standard due to its size and subsequent sensitivity to parasitic lateral forces. To maximize the benefits from this sensor, particularly overload capability and long-term stability, in the high accuracy torque measurement application area, there is a need to develop significantly smaller devices. The aim of this thesis is to research through FEA modelling and experimental characterisation the key performance parameters required to produce a miniaturised metallic TBTF resonant sensor that provides better performance when applied in a torque measurement system. For high accuracy any torque transducer using these sensors ought to have low sensitivity to parasitic influences such as bending moments and lateral forces, which can only be achieved with reduced size. The problems with the existing design, key design issues, possible configuration and packaging solutions of the metallic TBTF resonant sensor that could be used for achieving a higher accuracy torque transfer standard are considered. Two designs of miniaturised metallic TBTF resonant sensors, SL20 and SL12, are considered and experimentally investigated. The lateral forces are reduced by 52% for SL20 design and by 80% for SL12 design when compared to the original SL40 design. A torque transducer using the SL20 design was calibrated falling into the Torque Transfer Standard class of accuracy 1 category, uncertainty 0.8%. A torque transducer using the SL12 design was made and calibration showed a class of accuracy 0.5 category, uncertainty 0.2%. The results from this research indicate that the SL12 design is suitable for use in a torque transfer standard. The SL12 design is optimal and the smallest size possible based on the overload capability design criteria requiring the tine cross sectional area to remain constant

Mechanics of electrified interfaces in diluted electrolytes

This work describes an experimental investigation of the interface between a solid metal and a fluid electrolyte. The question to be answered was: How does the surface stress vary with the surface charge density and how does the electrode potential vary with the elastic strain of the metal? The two variations are linked by the thermodynamic Maxwell relation that is well known but has not been tested in experiment. The aims of the thesis were twofold: First, to conduct careful experimental determination of the surface stress at electrode surfaces in aqueous electrolytes chosen to minimize the specific adsorption and thus to highlight selectively the role of capacitive processes. Second, to design and execute an experiment that allows for the first time to measure the variation of the electrode potential with the elastic strain. In the first approach, an in situ cantilever bending experiment was set up. The experiment shows that surface stress, f, varies linearly with the surface charge, q, with a response parameter ς = df/dq = —2.0 V. This value is larger, by the factor of two, than some previously reported experimental results. In the second approach, a new experimental approach was implemented, where the electrode is a metal film deposited on a polymer substrate and cyclic elastic strain of the electrode is imposed by straining the substrate via a piezoelectric actuator. This experiment supplies quantitative results for the potential — strain coupling. The value, ς = —1.83 V, is in good agreement with the cantilever bending experiment and the ab initio work. Therefore, for the first time, the important thermodynamic Maxwell relation was experimentally verified.In dieser Arbeit wird die experimentelle Untersuchung der Grenzflächen zwischen einem festen Metall und einem flüssigen Elektrolyt beschrieben. Die zu beantwortende Frage war inwiefern sich die elastische Flächenspannung mit der Oberflächenladungsdichte verändert und wie das Elektrodenpotential mit der elastischen Dehnung des Elektrodenmetalls zusammenhängt. Diese beiden Beziehungen hängen über die thermodynamische Maxwell-Relation, die zwar in der Literatur wohlbekannt aber noch nie experimentell nachgewiesen wurde, zusammen. Demzufolge ergaben sich zwei Ziele dieser Arbeit: Erstens die sorgfältige Ausführung einer experimentellen Bestimmung der elastischen Flächenspannung an Elektrodenoberflächen in wäßrigen Elektrolyten, welche so ausgesucht sind, daß sie die spezifische Adsorption minimieren und somit die Rolle der kapazitiven Prozesse isolieren. Zweitens ein Experiment aufzubauen und durchzuführen, welches erstmalig die Messung der Veränderung des Elektrodenpotentials als Funktion der elastischen Dehnung ermöglicht. In einem ersten Ansatz wurde ein in-situ Balkenbiegeexperiment aufgebaut. Dieses Experiment hatte zum Ergebnis, daß die elastische Flächenspannung f linear von der Oberflächenladung q abhängt; die Steigung, hier auch "Response-Parameter" genannt, betrug ς=df/dq= —2.0 V. Dieser Wert ist um einen Faktor 2 höher als Werte, die in früheren Experimenten ermittelt wurden. In einem zweiten Ansatz wurde ein neuer experimenteller Zugang implementiert, in welchem die Elektrode ein Metallfilm ist, der auf einem Polymersubstrat deponiert wurde, und anschließend zyklischen elastischen Dehnungen ausgesetzt wurde, indem das Polymersubstrat mittels eines piezoelektrischen Stellantriebs verformt wurde. Der ermittelt Wert ς= —1.83 V ist in guter Übereinstimmung mit dem Balkenbiegeexperiment und den ab-initio Rechnungen. Dieses Experiment liefert quantitative Ergebnisse für die Kopplung zwischen Potential und Dehnung. Demzufolge wurde hier die wichtige thermodynamische Maxwell-Relation erstmalig experimentell verifiziert

DAFI: a single mode optical fibre interferometer for astronomy

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Use of triple beam resonant gauges in torque measurement transfer standard

A new torque transfer standard using metallic TBTF resonant sensor was developed to overcome the overload capability problem which occurs with conventional metallic resistance strain gauges. Previous research work, however, has shown that the first prototype of the metallic TBTF resonant sensor was not suitable for use in a torque transfer standard due to its size and subsequent sensitivity to parasitic lateral forces. To maximize the benefits from this sensor, particularly overload capability and long-term stability, in the high accuracy torque measurement application area, there is a need to develop significantly smaller devices. The aim of this thesis is to research through FEA modelling and experimental characterisation the key performance parameters required to produce a miniaturised metallic TBTF resonant sensor that provides better performance when applied in a torque measurement system. For high accuracy any torque transducer using these sensors ought to have low sensitivity to parasitic influences such as bending moments and lateral forces, which can only be achieved with reduced size. The problems with the existing design, key design issues, possible configuration and packaging solutions of the metallic TBTF resonant sensor that could be used for achieving a higher accuracy torque transfer standard are considered. Two designs of miniaturised metallic TBTF resonant sensors, SL20 and SL12, are considered and experimentally investigated. The lateral forces are reduced by 52% for SL20 design and by 80% for SL12 design when compared to the original SL40 design. A torque transducer using the SL20 design was calibrated falling into the Torque Transfer Standard class of accuracy 1 category, uncertainty 0.8%. A torque transducer using the SL12 design was made and calibration showed a class of accuracy 0.5 category, uncertainty 0.2%. The results from this research indicate that the SL12 design is suitable for use in a torque transfer standard. The SL12 design is optimal and the smallest size possible based on the overload capability design criteria requiring the tine cross sectional area to remain constant.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Nanopositionnement 3D à base de mesure à courant tunnel et piezo-actionnement

The objective of this thesis was to elaborate high performance control strategies and their real-time validation on a tunneling current-based 3D nanopositioning system developed in GIPSA-lab. The thesis lies in the domain of micro-/nano mechatronic systems (MEMS) focused on applications of fast and precise positioning and scanning tunneling microscopy (STM). More precisely, the aim is to position the metallic tunneling tip (like in STM) over the metallic surface using piezoelectric actuators in X, Y and Z directions and actuated micro-cantilever (like in Atomic Force Microscope AFM), electrostatically driven in Z direction, with high precision, over possibly high bandwidth. However, the presence of different adverse effects appearing at such small scale (e.g. measurement noise, nonlinearities of different nature, cross-couplings, vibrations) strongly affect the overall performance of the 3D system. Therefore a high performance control is needed. To that end, a novel 3D model of the system has been developed and appropriate control methods for such a system have been elaborated. First the focus is on horizontal X and Y directions. The nonlinear hysteresis and creep effects exhibited by piezoelectric actuators have been compensated and a comparison between different compensation methods is provided. Modern SISO and MIMO robust control methods are next used to reduce high frequency effects of piezo vibration and cross-couplings between X and Y axes. Next, the horizontal motion is combined with the vertical one (Z axis) with tunneling current and micro-cantilever control. Illustrative experimental results for 3D nanopositioning of tunneling tip, as well as simulation results for surface topography reconstruction and multi-mode cantilever positioning, are finally given.L'objectif de la thèse est l'élaboration de lois de commande de haute performance et leur validation en temps réel sur une plateforme expérimentale 3D de nano-positionnement à base de courant à effet tunnel, développée au laboratoire GIPSA-lab. Elle s'inscrit donc dans le cadre des systèmes micro-/nano-mécatronique (MEMS), et de la commande. Plus précisément, le principal enjeu considéré est de positionner la pointe métallique à effet tunnel (comme en microscopie à effet tunnel STM) contre la surface métallique en utilisant des actionneurs piézoélectriques en X, Y et Z et un micro-levier (comme en microscopie à force atomique AFM) actionné électrostatiquement en Z avec une grande précision et une bande passante élevée. Cependant, la présence de différents effets indésirables apparaissant à cette petite échelle (comme le bruit de mesure, des non-linéarités de natures différentes, les couplages, les vibrations) affectent fortement la performance globale du système 3D. En conséquence, une commande de haute performance est nécessaire. Pour cela, un nouveau modèle 3D du système a été développé et des méthodes de contrôle appropriées pour un tel système ont été élaborées. Tout d'abord l'accent est mis sur de positionnement selon les axes X et Y. Les effets d'hystérésis et de fluage non linéaires présents dans les actionneurs piézoélectriques ont été compensés et une comparaison entre les différentes méthodes de compensation est effectuée. Des techniques modernes de commande robuste SISO et MIMO sont ensuite utilisées pour réduire les effets des vibrations piézoélectriques et des couplages entre les axes X et Y. Le mouvement horizontal est alors combiné avec le mouvement vertical (Axe Z) et une commande du courant tunnel et du micro-levier. Des résultats expérimentaux illustrent le nano positionnement 3D de la pointe, et des résultats de simulation pour la reconstruction de la topographie de la surface ainsi que le positionnement du micro-levier à base d'un modèle multi-modes

Design and realization of a microassembly workstation

With the miniaturization of products to the levels of micrometers and the recent developments in microsystem fabrication technologies, there is a great need for an assembly process for the formation of complex hybrid microsystems. Integration of microcomponents made up of different materials and manufactured using different micro fabrication techniques is still a primary challenge since some of the fundamental problems originating from the small size of parts to be manipulated, high precision necessity and specific problems of the microworld in that field are still not fully investigated. In this thesis, design and development of an open-architecture and reconfigurable microassembly workstation for efficient and reliable assembly of micromachined parts is presented. The workstation is designed to be used as a research tool for investigation of the problems in microassembly. The development of such a workstation includes the design of: (i) a manipulation system consisting of motion stages providing necessary travel range and precision for the realization of assembly tasks, (ii) a vision system to visualize the microworld and the determination of the position and orientation of micro components to be assembled, (iii) a robust control system and necessary fixtures for the end effectors that allow easy change of manipulation tools and make the system ready for the desired task. In addition tele-operated and semi-automated assembly concepts are implemented. The design is verified by implementing tasks in various ranges for micro-parts manipulation. The versatility of the workstation is demonstrated and high accuracy of positioning is shown

Optimising the NAOMI adaptive optics real-time control system

This thesis describes the author's research in the field of Real-Time Control (RTC) for Adaptive Optics (AO) instrumentation. The research encompasses experiences and knowledge gained working in the area of RTC on astronomical instrumentation projects whilst at the Optical Science Laboratories (OSL), University College London (UCL), the Isaac Newton Groups of Telescopes (ING) and the Centre for Advanced Instrumentation (СfAI), Durham University. It begins by providing an extensive introduction to the field of Astronomical Adaptive Optics covering Image Correction Theory, Atmospheric Theory, Control Theory and Adaptive Optics Component Theory. The following chapter contains a review of the current state of world wide AO instruments and facilities. The Nasmyth Adaptive Optics Multi-purpose Instrument (NAOMI), the common user AO facility at the 4.2 William Herschel Telescope (WHT), is subsequently described. Results of NAOMI component characterisation experiments are detailed to provide a system understanding of the improvement optimisation could offer. The final chapter investigates how upgrading the RTCS could increase NAOMI'S spatial and temporal performance and examines the RTCS in the context of Extremely Large Telescope (ELT) class telescopes