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Robust Safety Filtering for Input-Constrained Underactuated Linear Systems
Authors:
Muhamad Rausyan Fikri
Abstract:
We present a robust safety-filtering framework for input-constrained underactuated linear systems subject to unknown disturbances. A baseline H-$\infty$ input is derived from a zero-sum differential game, while a disturbance observer supplies an estimate and a transient error bound. The baseline input is adjusted using the disturbance estimate, while the estimate and its error bound are used to de…
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We present a robust safety-filtering framework for input-constrained underactuated linear systems subject to unknown disturbances. A baseline H-$\infty$ input is derived from a zero-sum differential game, while a disturbance observer supplies an estimate and a transient error bound. The baseline input is adjusted using the disturbance estimate, while the estimate and its error bound are used to define robust high-order control barrier function constraints; forward invariance holds as long as the admissible-input set remains nonempty. For scalar-input systems, pointwise feasibility is determined from an exact input interval, and the interval width defines the feasibility margin. A finite-horizon H-$\infty$ performance balance accounts for the accumulated deviation of the applied input from the baseline H-$\infty$ policy. Simulations on a linearized two-wheeled balancing robot show how position and body-pitch constraints compete for the same bounded wheel-torque input.
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Submitted 11 August, 2026;
originally announced August 2026.
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Effect of reaction temperature on nascent carbonaceous particles from toluene shock-tube pyrolysis: Insights from FTIR and Raman spectroscopy
Authors:
Meysam K. Rezaeian,
Can Shao,
Jürgen Herzler,
Mustapha Fikri,
Greg J. Smallwood,
Christof Schulz
Abstract:
The transition from gaseous precursors to nascent solid particles and their subsequent structural maturation were investigated in single-pulse shock-tube experiments using ex situ Fourier-transform infrared (FTIR) and Raman spectroscopy of sampled products. A mixture of 2% toluene in argon was pyrolyzed at around 2.0 bar with temperature plateau times of 2.0 ms over the 1450-1800 K reaction temper…
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The transition from gaseous precursors to nascent solid particles and their subsequent structural maturation were investigated in single-pulse shock-tube experiments using ex situ Fourier-transform infrared (FTIR) and Raman spectroscopy of sampled products. A mixture of 2% toluene in argon was pyrolyzed at around 2.0 bar with temperature plateau times of 2.0 ms over the 1450-1800 K reaction temperature range. In situ laser extinction measurements indicate the onset of particle formation at 1570 K. At this temperature, Raman spectra exhibit emerging D and G bands, and transmission electron microscopy (TEM) reveals the disappearance of poorly defined structures, identifying 1570 K as the phase-transition reaction temperature. Approaching this reaction temperature, Raman spectra show a rapid disappearance of sp hybridized triple carbon bonds. At 1670 K reaction temperature, a maximum in primary particle diameter and a decrease in structural disorder inferred from Raman spectroscopy are observed, defining the ordering threshold. Deconvolution of the FTIR spectra enables separation of in ring double carbon bond stretching vibrations from isolated and ring-conjugated side-chain double carbon bond modes. The in-ring double carbon band is used to normalize aliphatic and aromatic C-H vibrations. FTIR analysis reveals ring-edge structures associated with electron-localization sites, including bay regions, five-membered ring defects, and benzylic positions, indicating a radical-rich environment below the phase-transition temperature. Between the phase-transition and ordering-threshold temperatures, K-regions and armchair structures associated with electron delocalization and thermal stability increase. The emergence of these electronic and structural characteristics highlights the critical role of radicals in soot inception and early structural ordering.
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Submitted 29 April, 2026;
originally announced April 2026.
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A review of Implementation and Challenges of Unmanned Aerial Vehicles for Spraying Applications and Crop Monitoring in Indonesia
Authors:
Muhamad Rausyan Fikri,
Taufiq Candra,
Kushendarsyah Saptaji,
Ajeng Nindi Noviarini,
Dilla Ayu Wardani
Abstract:
The rapid development of technology has brought unmanned aerial vehicles (UAVs) to become widely known in the current era. The market of UAVs is also predicted to continue growing with related technologies in the future. UAVs have been used in various sectors, including livestock, forestry, and agriculture. In agricultural applications, UAVs are highly capable of increasing the productivity of the…
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The rapid development of technology has brought unmanned aerial vehicles (UAVs) to become widely known in the current era. The market of UAVs is also predicted to continue growing with related technologies in the future. UAVs have been used in various sectors, including livestock, forestry, and agriculture. In agricultural applications, UAVs are highly capable of increasing the productivity of the farm and reducing farmers' workload. This paper discusses the application of UAVs in agriculture, particularly in spraying and crop monitoring. This study examines the urgency of UAV implementation in the agriculture sector. A short history of UAVs is provided in this paper to portray the development of UAVs from time to time. The classification of UAVs is also discussed to differentiate various types of UAVs. The application of UAVs in spraying and crop monitoring is based on the previous studies that have been done by many scientific groups and researchers who are working closely to propose solutions for agriculture-related issues. Furthermore, the limitations of UAV applications are also identified. The challenges in implementing agricultural UAVs in Indonesia are also presented.
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Submitted 1 January, 2023;
originally announced January 2023.