4,053 research outputs found

    Uncertainty budget of a large-range nanopositioning platform based on Monte Carlo simulation

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    The objective of precision systems design is to obtain machines with very high and totally predictable work-zone accuracies. In already functional systems, where the errors can be measured, this is achieved by error correction and compensation. The aim of this work is to propose an uncertainty budget methodology to obtain the final measuring uncertainty of precise measuring systems, after error compensation. The case study is a nanopositioning platform, referred as NanoPla, with a confocal sensor integrated as measuring instrument. The NanoPla performs precise positioning in a large range of 50 mm × 50 mm, and its target is surface topography characterization, at a submicrometre scale. After performing the uncertainty budget of the NanoPla, Monte Carlo method is used to obtain the final measuring uncertainty along the whole NanoPla working range, considering all the casuistry. By studying the results, the authors are able to propose solutions to minimize the final measuring uncertainty

    Generalized Parity-Time Symmetry Condition for Enhanced Sensor Telemetry

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    Wireless sensors based on micro-machined tunable resonators are important in a variety of applications, ranging from medical diagnosis to industrial and environmental monitoring.The sensitivity of these devices is, however, often limited by their low quality (Q) factor.Here, we introduce the concept of isospectral party time reciprocal scaling (PTX) symmetry and show that it can be used to build a new family of radiofrequency wireless microsensors exhibiting ultrasensitive responses and ultrahigh resolution, which are well beyond the limitations of conventional passive sensors. We show theoretically, and demonstrate experimentally using microelectromechanical based wireless pressure sensors, that PTXsymmetric electronic systems share the same eigenfrequencies as their parity time (PT)-symmetric counterparts, but crucially have different circuit profiles and eigenmodes. This simplifies the electronic circuit design and enables further enhancements to the extrinsic Q factor of the sensors

    A 2 degree-of-freedom SOI-MEMS translation stage with closed loop positioning

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    This research contains the design, analysis, fabrication, and characterization of a closed loop XY micro positioning stage. The XY micro positioning stage is developed by adapting parallel-kinematic mechanisms, which have been widely used for macro and meso scale positioning systems, to silicon-based micropositioner. Two orthogonal electrostatic comb drives are connected to moving table through 4-bar mechanism and independent hinges which restrict unwanted rotation in 2-degree-of-freedom translational stage. The XY micro positioning stage is fabricated on SOI wafer with three photolithography patterning processes followed by series of DRIE etching and HF etching to remove buried oxide layer to release the end-effector of the device. The fabricated XY micro positioning stage is shown in Fig1 with SEM images. The device provides a motion range of 20 microns in each direction at the driving voltage of 100V. The resonant frequency of the XY stage under ambient conditions is 811 Hz with a high quality factor of 40 achieved from parallel kinematics. The positioning loop is closed using a COTS capacitance-to-voltage conversion IC and a PID controller built in D-space is used to control position with an uncertainty characterized by a standard distribution of 5.24nm and a approximate closed-loop bandwidth of 27Hz. With the positioning loop, the rise time and settling time for closed-loop system are 50ms and 100ms. With sinusoidal input of ω=1Hz, the maximum phase difference of 108nm from reference input is obtained with total motion range of 8μm

    Recent Advances in Printed Capacitive Sensors

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    In this review paper, we summarize the latest advances in the field of capacitive sensors fabricated by printing techniques. We first explain the main technologies used in printed electronics, pointing out their features and uses, and discuss their advantages and drawbacks. Then, we review the main types of capacitive sensors manufactured with different materials and techniques from physical to chemical detection, detailing the main substrates and additives utilized, as well as the measured ranges. The paper concludes with a short notice on status and perspectives in the field.H2020-MSCA-IF-2017-794885-SELFSEN

    Design optimization for the measurement accuracy improvement of a large range nanopositioning stage

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    Both an accurate machine design and an adequate metrology loop definition are critical factors when precision positioning represents a key issue for the final system performance. This article discusses the error budget methodology as an advantageous technique to improve the measurement accuracy of a 2D-long range stage during its design phase. The nanopositioning platform NanoPla is here presented. Its specifications, e.g., XY-travel range of 50 mm ˆ 50 mm and sub-micrometric accuracy; and some novel designed solutions, e.g., a three-layer and two-stage architecture are described. Once defined the prototype, an error analysis is performed to propose improvement design features. Then, the metrology loop of the system is mathematically modelled to define the propagation of the different sources. Several simplifications and design hypothesis are justified and validated, including the assumption of rigid body behavior, which is demonstrated after a finite element analysis verification. The different error sources and their estimated contributions are enumerated in order to conclude with the final error values obtained from the error budget. The measurement deviations obtained demonstrate the important influence of the working environmental conditions, the flatness error of the plane mirror reflectors and the accurate manufacture and assembly of the components forming the metrological loop. Thus, a temperature control of ¿0.1 ¿C results in an acceptable maximum positioning error for the developed NanoPla stage, i.e., 41 nm, 36 nm and 48 nm in X-, Y- and Z-axis, respectively

    Design, Development and Implementation of the Position Estimator Algorithm for Harmonic Motion on the XY Flexural Mechanism for High Precision Positioning

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    This article presents a novel concept of the position estimator algorithm for voice coil actuators used in precision scanning applications. Here, a voice coil motor was used as an actuator and a sensor using the position estimator algorithm, which was derived from an electro-mechanical model of a voice coil motor. According to the proposed algorithm, the position of coil relative to the fixed magnet position depends on the current drawn, voltage across coil and motor constant of the voice coil motor. This eliminates the use of a sensor that is an integral part of all feedback control systems. Proposed position estimator was experimentally validated for the voice coil actuator in integration with electro-mechanical modeling of the flexural mechanism. The experimental setup consisted of the flexural mechanism, voice coil actuator, current and voltage monitoring circuitry and its interfacing with PC via a dSPACE DS1104 R&D microcontroller board. Theoretical and experimental results revealed successful implementation of the proposed novel algorithm in the feedback control system with positioning resolution of less than ±5 microns at the scanning speed of more than 5 mm/s. Further, proportional-integral-derivative (PID) control strategy was implemented along with developed algorithm to minimize the error. The position determined by the position estimator algorithm has an accuracy of 99.4% for single direction motion with the experimentally observed position at those instantaneous states

    Near-Field Focusing Sensor for Characterization of Void Content in Thin Dielectric Layers

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    A sensor concept is developed and analyzed for in situ characterization of a thin dielectric layer. An array of long, planar electrodes is flush-mounted into opposing faces of two substrates on either side of the dielectric layer. The substrates are oriented such that the lengthwise dimensions of the opposing electrodes are orthogonal. Capacitance is measured between single electrode pairs on opposite substrates while all other electrodes are grounded. The electric field between the active electrodes is sharply focused at their crossing point, resulting in high sensitivity to void content in a square detection zone of the dielectric layer. For a fixed interfacial gap size, direct proportionality of the capacitance with void fraction within the detection zone is poor for high electrode-to-electrode spacing on the substrates, but improves dramatically as this spacing is reduced. Three methods of deriving a simulationbased sensitivity response of measured capacitance to any arbitrary two-dimensional void geometry are investigated. The best method requires data from simulations of an empty air gap and a TIM-filled gap, and uses a reduced-order superposition technique to predict the normalized capacitance value obtained for any void geometry to within 10% of that predicted by a high-fidelity direct simulation. The sensing technique is demonstrated using manually introduced voids of 250 μm–2000 μm diameter in a 254 μm thick interface material layer with a dielectric constant of 4.7. The relationship of the capacitance to the void fraction is shown to fall within the predicted bounds

    Capacitive imaging technique for non-destructive evaluation (NDE)

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    This thesis describes the development and characterization of a novel NDE methodthe Capacitive Imaging (CI) technique. The CI technique employs a pair of (or multiple) electrodes to form a co-planar capacitor, and uses the fringing quasi-static electric field established across the electrodes to investigate specimens of interest. In general, the CI probe is sensitive to surface and hidden defects in insulating materials, and surface features on conducting materials. The CI technique is advantageous for its non-contact and non-invasive nature, and the capacitive coupling allows the CI technique to work on a wide variety of material properties. The theoretical background to the CI technique has been developed. It is shown that in the frequency range of operation (10 kHz to 1 MHz), the quasi-static approximation is valid and the Maxwell’s Equations describing the general electromagnetic phenomena can be simplified. The practical implementation of the CI system is based on this analysis, and it is shown that the CI technique has features that can complement techniques such as eddy current methods that are already established in NDE. The design principles of the CI probes that are required for an optimum imaging performance have been determined, by considering the key measures of the performance including the depth of penetration, the measurement sensitivity, the imaging resolution and the signal to noise ratio (SNR). It has been shown that the operation frequency is not an influential factor - the performance of the CI probe is determined primarily by the geometry of the probe (e.g. size/shape of the electrodes, separation between electrodes, guard electrodes etc.). Symmetric CI probes with triangular-shaped electrodes were identified as a good general purpose design. Finite Element (FE) models were constructed both in 2D and 3D in COMSOLTM to predict the electric field distributions from CI probes. Effects of thickness of specimen, liftoff distance and relative permittivity value etc were examined using the 2D models. The sensitivity distributions of different CI probes were obtained from the 3D models and were used to characterize the imaging ability of the given CI probes. The fundamental concepts of the CI technique have been experimentally validated in a series of scans where the defects were successfully imaged in insulating (Perspex) and conducting (e.g. Aluminium, Steel and carbon fibre composite) specimens. The detection of corrosion under insulation (CUI) has also been demonstrated. The imaging abilities were assessed by investigating various standard specimens under different situations. The CI technique was then successfully applied to various practical specimens, including glass fibre laminated composites and sandwich structures, laminated carbon fibre composites, corroded steel plate and pipe, and concrete specimens. Further measurements were also conducted using modified CI probes, to demonstrate the wide range of applications of the CI technique
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