This paper analyzes anti-phase parametric excitation for a resonant MEMS mirror by independently driving two out-of-plane electrostatic comb-drive actuators positioned at the left and right sides of the MEMS mirror, enabling a fast and reliable start-up from zero amplitude. Both the angular derivative of the comb drives’ capacitance and the square wave driving signals are approximated by complex Fourier series, leading to a nonlinear model that describes the slow evolution of the amplitude and the phase of the MEMS mirror. The proposed model is validated through measurements, demonstrating strong agreement with the analytical results. A detailed discussion on injected and dissipated energy provides an intuitive understanding of the response curve for in-phase and anti-phase excitation signals with various duty cycles. Additionally, the initial start-up behavior of conventional in-phase parametrically excited MEMS mirrors is analyzed and compared to that of MEMS mirrors operated with anti-phase excitation, revealing an improvement of the start-up time by a factor between 8 to 50, depending on the operating point and condition.

This paper presents a novel approach for accurate surface reconstruction of uniformly moving rigid samples from multi-shot structured light profilometry (SLP). Conventional triangulation-based multi-shot SLP cannot handle moving objects as motion during the acquisition phase causes errors in the assignment of pixel correspondence between cameras and projector. The proposed method utilizes an optimization-based, iterative strategy that considers the movement of the sample between consecutive captures to reconstruct the surface geometry. The optimization process is designed to minimize an objective function which evaluates the pixel value similarities between reprojected surface points in both the camera and projector images. The surface is reconstructed by iteratively refining the minimum search in the objective function using image filtering methods and gradient-based solvers. The method enables robust surface reconstruction of moving samples with a high measurement accuracy of 17 mu m for various directions and extents of motion, which can compete with static measurement results from conventional, high-accuracy SLP methods while outperforming them by a factor of more than 20 for large sample displacements, making multi-shot SLP accessible for industrial in-line measurement applications.

This paper presents the design and experimental evaluation of a telescope-based scanning light detection and ranging (LiDAR) system for eye-safe long-range localization and tracking of small uncrewed aerial vehicles (UAVs). A prototype with an eye-safe custom-built laser transmitter module, a one-dimensional APD detector array, a telescope, and a telescope mount is implemented to verify the system design. Experiments from a laboratory environment demonstrate robust static and dynamic localization of a DJI Phantom 3 UAV at a range of 300 m. Field tests confirm the system's capabilities, successfully demonstrating distance measurements to a DJI Matrice 30 at ranges up to 50 m, and the feasibility of hybrid target tracking at velocities up to 15 m/s at distances of 300 m, where horizontal tracking is achieved using LiDAR data and applying a spatio-temporal filter with a DBSCAN-based algorithm. In contrast, vertical tracking is performed based on image-based processing.

This article deals with the correction of cross-scan errors in polygon mirror (PM)-based laser scanning systems by active error compensation (AEC) using a fast-steering mirror (FSM). However, AEC is susceptible to sensor noncollocation errors since the FSM is typically controlled via an internal angular sensor. This sensor error can be evaluated by position measurements of the scanning laser, but these measurements are not always feasible due to the inherent duty cycle of PM-based scanning systems. Image-based iterative AEC (II-AEC) is proposed to use partial measurements to address the sensor noncollocation error, thereby improving the precision of PM-based scanning systems. II-AEC consists of a cascade structure where the inner loop employs iterative learning control for the FSM using the internal sensor, and the outer loop iterates the inner loop reference based on the laser positions measured by a complementary metal-oxide-semiconductor (CMOS) sensor. II-AEC has been implemented and evaluated on a PM-based stereolithography apparatus, resulting in a 40-fold printing precision improvement compared to the uncompensated apparatus.

This paper presents the integration and experimental evaluation of a robust pointing recalibration algorithm for improved pointing performance of a portable telescope system to enable high-accuracy tracking of satellites and space debris, despite structural and envi-ronmental changes. A spherical harmonic pointing model is periodically updated throughout the observation period, using a batch opti-mization method, combined with a quadrant-random pointing grid. Instead of deteriorating by a factor of 3 over several hours for conventional operation, the proposed method preserves the accuracy of the initial model. Optical tracking experiments of Low Earth Orbit satellites indicate the proposed pointing recalibration improves the mean tracking error by a factor of up to 7. (c) 2026 The Author(s). Published by Elsevier B.V. on behalf of COSPAR. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/).

This paper presents a systematic analysis of the system dynamics of small telescope systems with an aperture below 0.5m and total weight below 150kg for deployable operation on support structures with limited mass and stiffness. Structural modes, introduced by either foundation or subcomponents, typically limit the achievable bandwidth of telescope systems to the single Hertz range. Identifying performance-limiting factors is crucial for further improving the pointing and tracking performance. This knowledge allows the optimization of the system for high closed-loop bandwidths and, therefore, enables applications with a demand for high dynamics and fast motion, such as uncrewed aerial vehicle (UAV) tracking. In this work, the dynamics of support structures, the telescope mount, and subcomponents are investigated in the frequency domain by a combination of finite element method (FEM) simulations and in situ measurements from motor encoders and accelerometers. A mean absolute percentage error of 20% is achieved between FEM simulations and measurements. Laboratory results are further validated by outdoor experiments, indicating the transferability of dynamic characteristics to deployable field operation. The analysis demonstrates that compliant coupling between support structures and ground mainly influences the system dynamics in the low-frequency range. Passive damping measures are investigated for the improvement of the system dynamics, with the first resonance of the altitude axis observed at 7Hz without damping and 20Hz with damping. Additional investigations cover the impact of different foundations, damping strategies, ground fixation, inertia variation, and load dynamics. Based on identifying resonance modes and weak spots, recommendations for structural enhancement are provided. These findings support the design of deployable telescope systems with improved dynamic performance and higher closed-loop bandwidths, enabling their use in demanding applications that require fast and precise tracking.

The mechanical dynamics of poricidal stamens play a crucial role in buzz pollination, but they have only been studied in a few species showing comparatively less curvature. This paper presents an integrated experimental-computational approach to characterize the dynamic behaviour of the morphologically more complex stamens of Medinilla magnifica. An experimental set-up employing a custom-built shaker and a laser triangulation sensor is developed to measure the stamen motion with high spatial and temporal resolution. The resulting displacement transmissibility reveals three distinct resonances, with the second one falling within the reported frequency range of pollination buzzes. Finite-element and multi-body models are developed and validated against experimental results. The models further reveal how the stamen morphology gives rise to its complex dynamic behaviour. The developed method enables precise parametric modelling of stamens and provides new insight into the mechanical basis of pollen release, thereby offering a framework for studying buzz pollination dynamics across plant taxa.

This work presents a compact tip/tilt fast steering mirror (FSM) based on a linearized hybrid reluctance actuation topology. The actuation principle is analyzed using a magnetic equivalent circuit model and finite-element method simulations. The proposed design achieves a large range of +/- 5/10 deg (mechanical/optical) with an optical aperture of 1 x 1.5 inch, delivering higher torque and linearity compared to the state of the art. To maintain compactness, the system uses magnetically coupled axes while achieving a decoupling of over 30 dB. Independent control loops for each yield position bandwidths of 1.06 kHz and 1.13 kHz, enabling a precision below 1.2 mdeg, and Lissajous scanning up to 110 Hz with 4 deg. Overall, the compact FSM demonstrates the highest range-bandwidth product (+22%) with the largest range of hybrid reluctance actuated systems.

This paper presents a measurement-based framework for deriving generic hand-arm vibration criteria (HAVC) for the dynamic evaluation, modeling, and simulation of hand-held precision devices. An inertial measurement system captures translational and rotational vibrations in all six degrees of freedom across representative postures, instrument masses, and operators. The dataset is analyzed using unified spatial referencing, power spectral densities, statistical descriptors, and cross-spectral relationships to establish population-level vibration characteristics. The measurements indicate that operator-induced vibration is dominated by low-frequency physiological tremor, shows systematic dependencies on posture and mass, and exhibits minimal cross-axis coupling. Parametric spectral envelopes are fitted to the median spectra and expressed as normalized filters, enabling the synthesis of realistic vibration signals from appropriately scaled white noise. This approach provides simulation-ready disturbance inputs for control design, structural sensitivity analysis, and optomechatronic performance assessment. The proposed HAVC extend the vibration criterion concept from environmental excitation to human-instrument interaction, providing quantitative reference envelopes for the predictive design of hand-held precision systems.

This work proposes a methodology to optimize actuator contribution to the overall system for constellations with optical links between satellites and Earth, where multiple laser communication terminals are deployed on a common host platform to maximize link duration and enable data exchange between multiple communication nodes. To satisfy specifications regarding field of regard, bandwidth, and accuracy, a combination of dedicated actuators is employed. The strategy, known as control allocation, is tailored to meet the requirements of optical communication. The procedure considers the dynamics and constraints of each actuator, providing a comprehensive approach. It enables a modular design, including the host satellite platform itself. As a result, the allocation algorithm enables optimizations concerning power consumption, adaptation to dynamic link switching conditions, and tracking robustness compared to a decentralized approach. This is achieved by assigning disturbances to the most suitable actuator while meeting secondary objectives. Bounded non-linear weighted least squares optimization is used to account for coordinate system transformation, and a graphical tool is demonstrated to tune the involved weighting matrices in the developed multi-link scenario.

Regardless of size, the imaging quality of ground-based reflective telescopes is influenced by numerous factors, among which are mechanical deformations in the telescope structure itself. Depending on the telescope’s condition and the surrounding environment, these systems are susceptible to errors due to flexure, ageing, gravitational and thermal influences, which may lead to a considerable degradation of imaging quality. The 1.5 m telescope at the Leopold Figl - Observatory for Astrophysics (LFOA) is Austria’s largest reflective telescope, and after more than 50 years of operation its optical, imaging, and structural properties must be evaluated. This work studies the mechanical integrity of the telescope system by measuring five degrees of freedom (defocus, tip/tilt rotation and x/y lateral displacement) and estimating their effect on imaging quality. An overall expected axial defocus of 36 ± 9 m, tip and tilt rotation of 8 ± 5 arcsec and 4 ± 2 arcsec, x- and y-axis displacement of 73 ± 3 m and 118 ± 16 m were found respectively and the combined effect of these disturbances was estimated to correspond to an average Strehl ratio of S_R = 0.94. A worst-case scenario estimate was also made and corresponds to a Strehl ratio of S_R = 0.77. This analysis has helped create an outlook of possible solutions to improve and maintain the imaging quality of the 1.5 m LFOA, making it a competitive, accessible, and sustainable tool for scientists and enthusiasts alike.

As a result of current trends in miniaturisation and the need for faster electronic circuits, integrated circuit (IC) design has become more complex. Closely packed conductors carrying radiofrequency (RF) signals are subjected to parasitic coupling, complicating the IC design and validation. Prototyping of such devices is supported by contact probes that make an ohmic connection to contact pads. These pads take up valuable space and may interfere with the design. Alternatively, near-field probing techniques, that utilise capacitive and inductive coupling, have been employed for local RF voltage and current characterisation. In this research, such a near-field probe is developed through a multiscale 3D-printing process. It contains a miniaturised conductive loop, enclosing an area of 12.5 & micro;m2, and a conductive tip with an apex radius of 100 nm. A model-based approach, that makes use of the discrepancy between parasitic long-range, and local short-range contributions to the measurement signal, is expanded to conduct both RF voltage and current measurements with increased spatial resolution. With this approach, combined contactless RF-voltage and RF-current measurements were executed demonstrating a measurement bandwidth from 1 to 23 GHz. Capacitively coupled RF-voltage measurements achieved a spatial resolution of 8 & micro;m, while the spatial resolution of inductively coupled current measurements was only simulated. The simulation shows an expected spatial resolution of 3 & micro;m.

This paper presents an integrated modeling and optimization-based tuning framework for a switched-current-amplifier-driven fast steering mirror (FSM) used for beam-stabilization in optical laser communication applications. Based on an integrated system model, a discrete-time linear-quadratic-Gaussian (LQG) controller is tuned via a performance-driven optimization that directly minimizes a composite objective comprising (i) root-mean-square (RMS) pointing precision computed by frequency-domain dynamic error budgeting using representative in-orbit disturbance spectra, (ii) worst-case step-response metrics over a set of perturbed plant models, and (iii) frequency-domain robustness indicators. The approach is experimentally validated on a two-degree-of-freedom FSM test setup, under representative vibrations of optical laser communication terminals. Compared to a conventional cascaded PID/PI control structure tuned for maximum bandwidth, the optimized LQG controller improves RMS pointing precision by a factor of 2, reaching 0.21 mu rad, effectively suppressing internal noise contributions. Finally, tracking of a 100 Hz Lissajous trajectory for communication partner acquisition demonstrates that the tuned LQG controller achieves similar dynamic tracking performance compared to the cascaded PID/PI control structure.

This paper presents a topology for tilting hybrid reluctance actuators (HRAs) that improves linearity while maintaining high torque output. The primary source of non-linear behavior is identified, and design requirements for the new actuator topology are established using a magnetic equivalent circuit model. Finite element method simulations demonstrate that the proposed design achieves greater linearity and a higher torque to current ratio compared to state of the art actuators. For validation, a fast steering mirror, actuated by the proposed HRA topology, with a +/- 1 degrees range is designed and implemented. Experimental results confirm a threefold reduction in the variation of the torque to current ratio and stiffness, along with a 76% increase in the torque to current ratio compared to the state of the art HRAs.

This paper presents a Stewart platform with hybrid reluctance-actuated struts to achieve six-degrees-of-freedom motion capability. Tailored hybrid reluctance actuators (HRAs) are integrated into a novel strut design to achieve axial force transmission to the Stewart platform's end effector via flexure-based joints. Each actuator has a motion range of +/- 1 mm, leading to a platform workspace of +/- 1.34 mm along the vertical z-axis and +/- 1.1 mm in x-and y-direction. The rotational range amounts to +/- 0.66 degrees/0.78 degrees for tip/tilt motion. By implementation of a MIMO decoupling approach using canonical polyadic decomposition (CPD), position control bandwidths of up to 30 Hz are reached in the task space. The platform achieves millimeter stroke with sub-micrometer translational resolution (45 nm RMS), sub-microradian angular resolution (300 nrad RMS) and a bidirectional repeatability (1 sigma) of 0.15-0.32 mu m and 3.5-4.8 mu rad. The overall positioning accuracy (RMSE), quantified against external interferometric measurements, amounts to 1-2.3 mu m in translation and 11-15 mu rad in rotation.

This article presents the design and implementation of a laser speckle-based sensor for real-time measurement of translational in-plane displacements with single-nanometer precision. The system combines a high-speed camera, a laser diode, and an field-programmable gate array (FPGA) for real-time data acquisition and processing. A comprehensive comparison of subpixel in-plane motion estimation algorithms is conducted, identifying the paraboloid curve-fitting approach as an effective compromise between estimation accuracy and FPGA implementation complexity. The optimized paraboloid fitting enables high-resolution motion estimation in both translational degrees of freedom, requiring only 220 ns computation time. Experimental validation on three different optically rough samples demonstrates that the sensor achieves a precision of at least 5 nm across at measurement rates of several kilohertz. Additional measurements at motion frequencies up to 300 Hz show reliable resolution of motion amplitudes down to 10 nm. These results demonstrate the suitability of the in-plane sensor for integration into high-precision tracking applications.

A high-speed and high-resolution polygon mirror (PM)-based industrial stereolithography apparatus (SLA) is designed and integrated with advanced active error compensation (AEC). The designed PM-based scanner provides extremely high laser beam scanning speeds but suffers from wobble errors caused by facet tilts, compromising its print quality. The advanced AEC is proposed to reduce the wobble error, where laser beams are deflected according to a precomputed compensation trajectory using a fast-steering mirror with iterative learning control. By exploiting the repetitiveness of the compensation trajectory, the advanced AEC yields a substantial 27-fold reduction in the wobble error and achieves a printing precision of $5 \,{\upmu}\mathrm{m}$ in standard deviation, enabling the industrial SLA with $22 \,{\upmu}\mathrm{m}$ optical resolution in a $460 \,\mathrm{m}\mathrm{m}$ print range with a print speed of $230 \,\mathrm{m}/\mathrm{s}$. The achieved printing performance is demonstrated by printed samples using photosensitive resin.