Systems and Control · Cross-listed from cs.LG
On the Sample Complexity of Discounted Reinforcement Learning with Optimized Certainty Equivalents
Oliver Mortensen and Mohammad Sadegh Talebi
We study risk-sensitive reinforcement learning in finite discounted MDPs, where a generative model of the MDP is assumed to be available. We consider a family or risk measures called the optimized certainty equivalent (OCE), which includes important risk measures such as entropic risk, CVaR, and mean-variance. Our focus is on the sample complexities of learning the optimal state-action value function (value learning) and an optimal policy (policy learning) under recursive OCE. We provide an exact characterization of utility functions $u$ for which the corresponding OCE defines an objective that is PAC-learnable. We analyze a simple model-based approach and derive PAC sample complexity bounds. We establish that whenever $u$ does not have full domain $\text{dom}(u)\neq \mathbb{R}$, the corresponding problem is not PAC-learnable. Finally, we establish corresponding lower bounds for both value and policy learning, demonstrating tightness in the size $SA$ of state-action space, and for a more restricted class of utilities, we derive lower bounds that makes the dependence on the effective horizon $\frac{1}{1-\gamma}$ explicit. Specifically, for $\text{CVaR}_\tau$ we show that the correct dependence on $\tau$ is $\frac{1}{\tau^2}$, thus improving by a factor of $\frac{1}{\tau}$ over state-of-the-art although our bound has a suboptimal dependence on $\frac{1}{1-\gamma}$.
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Signal Processing
Rethinking Passive RIS: Finite Blocklength Reliability Analysis Under Thermal Noise
Farjam Karim, Deepak Kumar, Prathapasinghe Dharmawansa et al. (+3 more)
Short-packet communication alters the fundamental performance limits of reconfigurable intelligent surface (RIS)-assisted systems, making conventional analyses based on the infinite blocklength regime insufficient. This work investigates RIS-assisted transmission in the finite blocklength (FBL) regime while explicitly incorporating thermal noise generated by passive RIS elements, an effect commonly neglected in existing models. A unified analytical framework is developed to characterize the block-error rate (BLER), its asymptotic behavior, and the resulting goodput under both uniform and non-uniform RIS reflection coefficients. Our results show that ignoring RIS thermal noise leads to a pronounced overestimation of reliability with the mismatch increasing as the number of reflecting elements grows. Furthermore, increasing the RIS size does not always improve performance, particularly in the low transmit power regime where accumulated noise becomes dominant. Overall, the results highlight fundamental limitations of idealized RIS models and demonstrate the need for incorporating thermal noise for accurate system evaluation.
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All authors Farjam Karim, Deepak Kumar, Prathapasinghe Dharmawansa, Nurul Huda Mahmood, Arthur Sousa de Sena, Matti Latva-aho
Signal Processing
Rate-Splitting–Inspired Bistatic OFDM-ISAC
Bruno F. Costa, Anup Mishra, Israel Leyva-Mayorga et al. (+2 more)
Achieving effective uplink bistatic
ISAC over an OFDM waveform gives rise to challenging interference structures. These are mostly due to unequal direct- and echo-path contributions and Doppler-induced ICI, rendering orthogonal resource separation and fixed SIC strategies inadequate. To address this problem, we propose a RS-inspired framework where the transmitter splits each communication message into a robust and a supplementary stream, which are jointly superposed over a sensing signal. Furthermore, we present the design of a staged sensing-communication receiver. Based on this framework, we derive tractable per-subcarrier SINR expressions and establish the relation between sensing accuracy and communication reliability based on the Fisher information. Building on these, we formulate a joint power-allocation problem for SE maximization under sensing-performance and power constraints. The resulting non-convex formulation is solved using convex surrogates and fractional programming. Numerical results demonstrate that, compared to NOMA-inspired baselines, the proposed framework provides more effective IFI management and improved robustness to Doppler-induced ICI.
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All authors Bruno F. Costa, Anup Mishra, Israel Leyva-Mayorga, Taufik Abrão, Petar Popovski
Systems and Control · Cross-listed from cs.RO
Learning Altruistic Collaboration in Heterogeneous Multi-Team Systems
Riwa Karam, Ruoyu Lin, Brooks A. Butler et al. (+1 more)
This paper studies heterogeneous multi-team collaboration through dynamic
robot allocation, where the
robots themselves are treated as transferable resources. Leveraging Hamilton's rule from ecology as an altruistic decision-making mechanism, we propose a multi-team collaborative resource allocation framework with heterogeneous capabilities, transfer costs, and capability-dependent contributions. The resulting general heterogeneous resource assignment problem is combinatorial and is shown to be NP-hard. To address scalability, we develop a graph neural network policy under centralized training and decentralized execution that approximates the altruistic allocations based on Hamilton's rule. The model operates over the team interaction graph and predicts
robot-level transfer decisions and subsequent
robot-to-team assignments. The proposed approach is evaluated in a fire-fighting scenario against exact optimization and multi-step simulations, quantifying allocation quality, decision computation, and fire suppression. Five paired physical testbed trials with 15
robots compare learned reallocation with fixed team membership; the GNN reaches the modeled fire stopping threshold in all five trials, compared with two for static allocation.
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All authors Riwa Karam, Ruoyu Lin, Brooks A. Butler, Magnus Egerstedt
Systems and Control · Cross-listed from cs.RO
Mind the Gaps: Multi-Robot Feedback-Driven Ergodic Coverage in Unknown Environments
Thales Costa Silva and Nora Ayanian
In this work, we address the problem of multi-
robot adaptive coverage, where teams of
robots perform dynamic sampling by continuously adjusting their positions to collect data in an environment. This task can be challenging, particularly when
robots must be efficiently allocated to new sampling locations over time. Ergodic search methods optimize
robot trajectories by ensuring that the
robots' time-averaged spatial distribution aligns with the spatial distribution of environmental information. While these methods promote effective exploration provided a target distribution, they often fail to account for unknown prior distributions of the environment. To overcome this limitation, we propose an adaptive coverage strategy that utilizes real-time feedback from an environmental model to adjust
robot sampling behavior in response to unknown conditions. Our approach enhances traditional ergodic trajectory optimization by constructing a target spatial information distribution based on parametric models of the environment, which are updated online. This strategy assumes that the environment is either static or changes slowly compared to the
robot's motion. Our framework allows
robots to dynamically prioritize regions of high interest, improving coverage efficiency, synthesizing effective control policies for individual
agents, and optimizing resource use in settings with unknown prior distributions. We validate our approach through simulations, demonstrating its effectiveness in enhancing coverage and resource allocation.
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Systems and Control
Disturbance Rejection Control under Nested Signal Temporal Logic Specifications: A Recursive Design Approach
Yuzhang Peng, Jiaqi Yan, Kurui Ze et al. (+2 more)
For the control synthesis problem under signal temporal logic (STL) specifications, control barrier functions (CBFs) serve as an effective method. However, traditional CBF approaches are severely restricted in expressiveness, particularly failing to encode nested formulas containing multiple temporal operators. While recent methods based on reachability analysis attempt to address this, they incur a heavy computational burden and rely strictly on known system dynamics. To overcome this challenge, this paper investigates a CBF-based recursive control scheme for nested STL specifications under uncertain disturbances. Within this scheme, we introduce a novel recursive CBF design procedure guided by a modified STL tree (sTLT) to yield explicit, parameterized CBFs without heavy computational demands. To render the proposed recursive CBF design applicable to systems subject to uncertain disturbances, we further integrate a novel reconstructed CBF-based quadratic programming (QP) controller. This controller requires no prior knowledge of the disturbances while relaxing initial safety assumptions. The proposed recursive control synthesis framework is proven to effectively encode nested STL specifications while ensuring that the system satisfies the specifications under unknown disturbances, as supported by simulation results.
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All authors Yuzhang Peng, Jiaqi Yan, Kurui Ze, Wei Wang, Yu Pan
Systems and Control · Cross-listed from cs.RO
Gait-Level Motion Design and Evaluation Framework for Grasp-Based Dynamic Locomotion in Microgravity
Chaerim Moon, Joohyung Kim and Justin K. Yim
Locomotion in microgravity often relies on sparsely and irregularly arranged anchors, motivating grasp-based mobility with multiple limbs. In this setting, dynamic traversal requires consecutive anchored interactions under coupled dynamic and kinematic constraints, yet the effects of gait-level motion design on locomotion feasibility and performance remain insufficiently understood. This paper formulates the feasibility and performance objectives for grasp-based dynamic locomotion and develops a gait-level parameter-metric framework that relates motion parameters to corresponding evaluation metrics. A physics-based simulation study instantiates the framework across two quadruped morphologies in randomized three-dimensional anchor environments. Controlled variations in gait-level parameters reveal broadly consistent effects on contact support, motion-induced loading, kinematic feasibility, actuation demand, and traversal time across the two
robot realizations. These findings suggest that the investigated gait-level parameters provide an interpretable basis for analyzing feasibility and performance trade-offs.
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Systems and Control
DAE-Embedded Neural Control Verification for Shipboard Microgrids under Transient Shocks
Fei Feng, Lizhi Wang and Ziqian Liu
Neural control offers strong potential for handling highly nonlinear dynamics in shipboard microgrids (SMGs), yet its black-box nature can trigger abrupt control spikes and actuator saturation during initial transient shocks. This letter devises a formal verification method for SMG neural controller to assess its shock responses. Our contributions include: 1) a set-based SMG differential-algebraic equation(DAE) model compatible with set propagation; 2) a DAE-embedded bound propagation approach to compute tight envelopes of all possible neural control output. Extensive case studies demonstrate the effectiveness of the devised method in formally certifying SMG control performance under uncertain disturbances.
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Systems and Control
Resilient Energy-Based Control for DC Data Centers under Grid and Load Disturbances
Lizhi Wang, Fei Feng, Ella Chou et al. (+1 more)
This paper presents a passivity-based control framework for AC-DC converters supplying non-passive Information Technology rack loads in DC data centers. Unlike conventional cascaded proportional-integral controllers that ensure stability only near nominal operating points, the proposed method is derived from the system total energy balance using the Port-
Hamiltonian formulation. By shaping the stored energy and injecting virtual damping through a lossless interconnection with a PH controller, the converter behaves as a passive system even when interfaced with non-passive loads or under grid disturbances. The closed-loop system guarantees asymptotic voltage regulation and strict energy dissipation without assuming constant grid voltage or frequency. Simulation studies under realistic load and fault scenarios validate that the proposed controller achieves smaller voltage deviations, faster recovery, and superior robustness, demonstrating its suitability for future high-efficiency DC data-center architectures.
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All authors Lizhi Wang, Fei Feng, Ella Chou, Yashen Lin
Systems and Control · Cross-listed from cs.RO
Closed-Loop Sim-to-Real Reinforcement Learning for Deformable Microfiber Shape Control
Alessandro Amici, Houari Bettahar, Veeti Jaakkola et al. (+1 more)
Autonomous contact-based micromanipulation is challenging because surface and interfacial interactions at the microscale are difficult to model accurately, limiting the use of conventional model-based control and sim-to-real learning. We present a closed-loop sim-to-real reinforcement learning (RL) approach for microfiber shape control on a surface. The central idea is to train
geometric shape regulation in a simplified frictionless simulator and rely on real-time visual feedback during deployment to iteratively correct the observed effects of unmodeled surface interactions. An RL policy trained entirely in simulation is transferred directly to a physical dual-gripper micromanipulation system operating at 40 Hz, without retraining or domain adaptation. Using silk microfibers as a testbed, the policy achieves a mean point-wise shape error of 270 $\pm$ 80 $\mu$m across twenty-four diverse initial configurations. Across nine specimens covering all combinations of three fiber diameters (50, 80, and 120 $\mu$m) and three manipulated lengths (10 mm, 15mm, and 20 mm), the same policy achieves sub-millimeter final shape error without any retraining or retuning. These results show that a policy learned in a simplified simulator can achieve repeatable real-world microfiber shape regulation under surface contact, provided that the task-relevant effects of the sim-to-real mismatch remain observable and correctable within the closed feedback loop.
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All authors Alessandro Amici, Houari Bettahar, Veeti Jaakkola, Quan Zhou
Signal Processing
Rapid Adaptive Matched Filter for Detecting Radar Targets with Unknown Velocity
Anatolii A. Kononov
This paper introduces a Doppler domain localized (DDL) implementation of the adaptive matched filter (AMF) for radar target detection in severely heterogeneous clutter environments with limited training data. The proposed detector uses the concept of a region of possible target detection (RPTD), a small set of Doppler bins that capture most of the target signal power. This RPTD-based DDL-AMF detector outperforms an earlier suggested DDL implementation of the generalized likelihood ratio (GLR) test, which employs the region of detection improvement (RODI) concept. Unlike the RODI-based DDL-GLR detector, the proposed DDL-AMF detector requires no information on clutter spectrum parameters and no measurements to determine the number and locations of RODIs. Moreover, the performance of the RODI-based DDL-GLR detector falls far below the optimum when the target Doppler frequency is unknown. In contrast, the RPTD-based DDL-AMF detector ensures rapid adaptive detection with near-optimum performance under unknown target Doppler frequency and
multimodal clutter spectra.
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Image and Video Processing
HyperBench: Standardizing and Scaling Synthetic Evaluation for Hyperspectral Super-Resolution
Ritik Shah and Marco F. Duarte
Hyperspectral super-resolution (HSR) reconstructs a high-spatial-resolution hyperspectral image by fusing a low-resolution hyperspectral image (LR-HSI) with a high-resolution multispectral image (HR-MSI). In the absence of real-world paired data, HSR methods are evaluated almost exclusively on synthetic experiments derived from hyperspectral
datasets through Wald's protocol. Despite the protocol's widespread adoption, its practical implementation varies markedly across research works, typically relying on a single (usually Gaussian) or very few point spread functions (PSFs), one or two spectral response functions (SRFs), and a couple of spatial downsampling factors. As a result, reported performance figures are difficult to compare across the literature, in addition to being often difficult to reproduce; furthermore, they may not generalize across realistic sensing conditions. We introduce HyperBench, a unified and extensible framework that standardizes synthetic experimentation for HSR. HyperBench supports diverse degradation configurations spanning ten PSFs, four SRFs derived from operational multispectral sensors, configurable spatial downsampling factors, and matched additive white Gaussian noise; its goal is to automate large-scale evaluation and structured logging. By decoupling model development from experimental design, the framework enables reproducible, apples-to-apples cross-method comparison with minimal friction. We use HyperBench to evaluate six recently proposed HSR methods across a 70-configuration sweep on four widely used hyperspectral scenes and observe that the inter-method PSNR spread widens from approximately 5 dB on the easiest PSF to over 13 dB on the hardest - a fragility that is structurally invisible to the prevailing single-configuration evaluation protocol. HyperBench code is available at https://github.com/ritikgshah/HyperBench .
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Image and Video Processing
VRXU-net: A Deep Learning Approach for Brain Ischemic Stroke Lesion Detection and Segmentation in T1W MRI
Sayed Amir Mousavi Mobarakeh
When the blood supply to the
brain is obstructed by a clot, oxygen delivery to
brain tissues becomes insufficient, leading to cellular necrosis. In healthcare settings, accurately identifying and delineating ischemic lesion boundaries is essential for treatment and
surgical planning. However, ischemic stroke lesions vary widely in shape, size, and location, and in grayscale MRI modalities such as T1W they may resemble surrounding
brain structures. This makes lesion detection and
segmentation a challenging task for clinicians. This study introduces a novel VRU-Net architecture, derived from visual features, residual connections, and a U-shaped network, for detecting and segmenting ischemic stroke lesions in 3D
magnetic resonance imaging scans. The proposed method first uses a modified VGG model to identify ischemic stroke in separate 2D slices. Then, a U-shaped
segmentation model with residual blocks segments the lesion in each slice. This procedure is applied independently to the axial, sagittal, and coronal planes, and the final output is generated by aggregating the three
segmentation results. To improve both performance and processing speed, a high-performance classifier is applied before the
segmentation model in a sequential framework. This strategy reduces unnecessary
segmentation of non-lesion slices and improves overall accuracy. In addition, decomposing 3D images into 2D slices reduces model complexity while allowing information from three anatomical planes to support more accurate lesion localization. The proposed model is trained on the Anatomical Tracings of Lesions After Stroke
dataset and outperforms state-of-the-art models in terms of accuracy and Dice coefficient. Moreover, the
segmentation output provides feedback that helps the classification model reduce false-positive predictions.
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Image and Video Processing
Fast PSF Synthesis with Defocused and Spherical Aberration
Nicholas Ganino and Qi Guo
Accurately estimating the point spread function (PSF) of an optical system requires solving free-space wave propagation, which entails evaluating a diffraction integral. This integral is traditionally computed numerically using Fast
Fourier Transform (FFT) or Hankel Transform, as it lacks a closed-form solution. We show that, under defocus and spherical aberration, the diffraction integral admits an approximate closed-form solution by combining a piecewise Bessel approximation with Gaussian-type integrals. Based on this result, we develop a fast wave-based PSF simulator with linear complexity in the radial resolution. The proposed, un-optimized simulator achieves up to a 2x speedup over Hankel-based integration and a 4x speedup over FFT while closely matching wave-optical PSFs, enabling efficient large-scale depth-of-field synthesis.
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Image and Video Processing
Fractal triangular search: a metaheuristic for image content search
Erick O. Rodrigues, Panos Liatsis, Luiz Satoru et al. (+1 more)
This work proposes a variable neighbourhood search (FTS) that uses a fractal-based local search primarily designed for images. Searching for specific content in images is posed as an optimisation problem, where evidence elements are expected to be present. Evidence elements improve the odds of finding the desired content and are closely associated to it in terms of spatial location. The proposed local search
algorithm follows the fashion of a chain of triangles that engulf each other and grow indefinitely in a fractal fashion, while their orientation varies in each iteration. The authors carried out an extensive set of experiments, which confirmed that FTS outperforms state-of-the-art metaheuristics. On average, FTS was able to locate content faster, visiting less incorrect image locations. In the first group of experiments, FTS was faster in seven out of nine cases, being >8% faster on average, when compared to the second best search method. In the second group, FTS was faster in six out of seven cases, and it was >22% faster on average when compared to the approach ranked second best. FTS tends to outperform other metaheuristics substantially as the size of the image increases.
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All authors Erick O. Rodrigues, Panos Liatsis, Luiz Satoru, Aura Conci
Image and Video Processing · Cross-listed from cs.LG
TONIC: Token-Centric Semantic Communication for Task-Oriented Wireless Systems
Sige Liu and Kezhi Wang
Tokens are becoming the basic units through which foundation models represent and process information for understanding and inference. However, traditional wireless communication, centered on bit-level fidelity, faces a mismatch between what is transmitted reliably and what downstream models actually consume. This mismatch calls for a communication design that directly accounts for
token-level task relevance and downstream model requirements, rather than treating all transmitted bits as equally important. In this paper, we propose TONIC, a
token-centric semantic communication framework for task-oriented wireless systems. The transmitter converts each source sample into a sequence of
tokens, estimates
token-level task relevance, and allocates protection through utility-aware unequal error protection under a fixed channel-use budget. At the receiver,
token-level confidence is used to gate unreliable decisions, turning harmful substitutions into recoverable erasures before a
Transformer-based completion model restores the masked
tokens for final task inference. Our framework combines transmitter-side semantic-aware protection with receiver-side confidence-aware gating in a modular and interpretable architecture, rather than relying solely on fully black-box end-to-end learning. We further establish a utility-aware Bayes-risk interpretation for the receiver-side gating rule and study its interaction with unequal protection and completion. Experimental results on image classification show that TONIC consistently outperforms separation-based schemes, the pixel-domain DeepJSCC baseline, and
token-domain baselines under matched communication budgets over AWGN, Rayleigh, and Rician channels.
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Signal Processing · Cross-listed from cs.LG
Tabular foundation models for robust calibration of near-infrared chemical sensing data
Robin Reiter, Denis Cornet, Fabien Michel et al. (+2 more)
Near-infrared spectroscopy is increasingly used as a rapid, non-destructive chemical sensing technology for the analysis of food, pharmaceutical, biological, and environmental samples. However, the practical deployment of NIR sensors still depends on calibration models able to handle high-dimensional, collinear spectra, limited sample sizes, preprocessing dependence, spectral outliers, and extrapolation beyond the calibration domain. Here, we evaluate whether tabular foundation models can provide a new calibration strategy for NIR chemical sensing. We
benchmark TabPFN on 66 NIR
datasets covering 54 regression and 12 classification tasks, and compare direct inference on raw spectra with preprocessing-optimized inference against PLS/PLS-DA, Ridge, Catboost, and one-dimensional convolutional neural networks. The study uses a unified validation framework in which preprocessing and model selection are performed exclusively on calibration data before external test evaluation. In regression, preprocessing-optimized TabPFN achieves the best overall average rank and significantly outperforms PLS, CatBoost, TabPFN on raw spectra, and CNN-1D, while remaining statistically comparable to Ridge. In classification, TabPFN applied directly to raw spectra provides the best average rank, with performance close to the optimized variant. Robustness analyses show that TabPFN provides strong average predictive performance but that its advantage decreases on spectral outliers and extrapolated samples, where classical chemometric models remain competitive. These results suggest that tabular foundation models can complement established chemometric workflows for NIR chemical sensing, especially in small- to medium-sized calibration settings, while highlighting the need for spectroscopy-specific priors and uncertainty-aware deployment strategies.
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All authors Robin Reiter, Denis Cornet, Fabien Michel, Lauriane Rouan, Gregory Beurier
Systems and Control
Fully Actuated Manifold Constraint Based Output Feedback Control for Input-Constrained Uncertain Nonlinear Systems
Dianrui Mu, Changchun Hua, Yafeng Li et al. (+2 more)
This paper presents a low-complexity, model-free, output-feedback controller for a class of unknown time-varying nonlinear systems with unknown input constraints. The controller achieves the preset control accuracy when the actuator is not saturated and maintains flexible control accuracy after actuator saturation. This result extends existing constraint control methods for linear
manifolds to a more general form, including the construction of nonlinear
manifolds and various types of constraints, thereby achieving preset control accuracy within finite or fixed time. Additionally, flexible control under unknown saturation is achieved through the construction of an error-driven flexible constraint. Finally, second-order and higher-order control examples and simulations are provided.
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All authors Dianrui Mu, Changchun Hua, Yafeng Li, Jiannan Chen, Rao Wei
Systems and Control
Output Feedback Control of Linear Time-Invariant Systems with Operational Constraints
Marcel Menner, Heather Hussain and Eugene Lavretsky
This paper introduces a systematic method for designing robust linear controllers using output feedback in the presence of operational constraints. The design uses Nagumo's
Theorem and the Comparison Lemma to guarantee constraint satisfaction, while incorporating min-norm optimal control principles inspired by Control Barrier Functions. The resulting controller is a continuous piecewise-linear output feedback policy that preserves the closed-loop system's analyzability using linear systems theory. Due to the linear control design, multi-input multi-output (
MIMO) robustness margins can be derived with and without active operational constraints. This paper shows that operational constraints on the system's state can be satisfied using an observer-based output feedback control design. Through flight control trade studies, we demonstrate the practical relevance of the framework in safety-critical aircraft control applications.
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Systems and Control
A Physics Informed Learning Augmented Framework for Grid-Aware P2P Energy Trading
Devangi, Ankit Singhal and Yashasvi Bansal
Distribution networks are transitioning from passive to active systems, driven by the large-scale proliferation of distributed energy resources (DERs) at the grid edge. Peer-to-Peer (P2P) energy trading has emerged as a transformative paradigm that enables energy transactions among prosumers, aggregated here as microgrids (MG). Ensuring that these transactions remain physically feasible within the distribution network is a fundamental prerequisite for any credible P2P framework. This is typically handled by distribution system operators (DSO) through bilevel coordination in distributed P2P architectures, wherein MGs optimize trades independently of network constraints, and the DSO subsequently corrects the infeasible outcomes. However, such sequential coordination prevents MGs from anticipating network feasibility during P2P
market clearing, potentially leading to substantial post
market corrections, altered trading outcomes, and repeated MG DSO interactions. To this end, this paper proposes a physics informed learning augmented P2P DSO framework in which a
transformer-based model is trained to predict the DSOs response to proposed P2P trades, with network feasibility embedded directly in the training objective.
Embedding this model within P2P
market clearing
algorithm allows MGs to anticipate the DSOs response and refine their trading decisions during trading, before submission. The proposed framework is validated on the modified IEEE 69 bus distribution system with interconnected MGs. Relative to conventional bilevel DSO correction, case studies show that the proposed framework recovers 40.90% of P2P
market utilization and 22.00% of economic transactions, while empirically eliminating network constraint violations over a full year of operation and substantially reducing computational and communication overhead.
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Signal Processing
Advancements in Non-Invasive Neuroimaging: Exploring the Potential of Radar Technology for Brain Imaging and Tumour Detection
Keniel Peart, Indu Bodala and Shelly Vishwakarma
This study investigates radar technology for non-invasive
brain imaging and tumour detection, offering an alternative to MRI and CT scans. Using Ansys HFSS to simulate electromagnetic interactions in
brain tissues, we evaluate the penetration, signal strength, and safety of Patch and Vivaldi
antennas. Results show Patch
antennas are optimal for tumour localization, while Vivaldi
antennas suit broader scanning applications. Although promising for safer, more accessible imaging, especially in resource-limited environments, further research with diverse models and actual patient data is essential to advance this technology in non-invasive medical diagnostics.
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Systems and Control · Cross-listed from math.OC
Beyond Nonlinear Small-Gain Design: DADS with Partial-State Feedback
Iasson Karafyllis and Miroslav Krstic
Eduardo Sontag and coauthors studied Input-to-Output Stability (IOS) and the output asymptotic gain property. These notions changed control theory and recently had an impact on robust adaptive control through the Deadzone-Adapted Disturbance Suppression (DADS) control scheme. Moreover, recently the notion of IOS was extended to systems described by Partial Differential Equations (PDEs). In this work, we celebrate Eduardo Sontag by combining DADS and IOS for PDEs: we study the partial-state regulation problem for a scalar Ordinary Differential Equation (ODE) which is interconnected with a possibly infinite-dimensional system. In such a case the DADS control scheme can allow an escape from the requirements of the small-gain
theorem that is mainly used for partial-state feedback. We show the design procedure of partial-state DADS controllers and we prove robust regulation even in the presence of external inputs (disturbances) without assuming knowledge of any disturbance/parameter bounds. The DADS controller is applied to three different cases of the interconnection of an ODE with an almost completely unknown: (a) heat PDE, (b) transport PDE, and (c) wave PDE with viscous damping. We show that the same DADS controller can achieve robust regulation in all three cases.
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Audio and Speech Processing
Speech Quality Embeddings for Improved Detection and Classification of Degradations in Speech Signals
Michael Kuhlmann, Tobias Cord-Landwehr and Reinhold Haeb-Umbach
Automatic subjective
speech quality assessment (SSQA) traditionally estimates
speech quality on an utterance or system level. While this resolution was adequate for older transmission or synthesis systems that produced
speech signals of mediocre quality, modern systems generate high-quality
speech with degradations that may occur only locally. With suitable model architectures and regularization losses, SSQA models trained with utterance-level targets can also yield useful local predictions of
speech quality. In this work, we extend such models to produce frame-level
embeddings that cluster by degradation type. Specifically, we employ a partial mix-up strategy on a parallel corpus of clean and degraded utterances and apply a contrastive loss to distinguish between degradation types. Through experiments on both in- and out-of-domain data, we demonstrate that our approach improves degradation detection and enables the identification of degradation types by analyzing
embedding clusters.
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Signal Processing
Optimal Time Window and Frequency Bandwidth Parameter Combination for Subject-Specific Motor Imagery EEG Classification
Matthew A. McCartney, Liisa A. Kivioja, Sonal S. Baberwal et al. (+1 more)
Motor-imagery (MI)
EEG can be classified using supervised machine learning techniques such as Linear Discriminant Analysis applied to features extracted by Common Spatial Patterns. Performance of these models varies widely, possibly due to MI studies commonly utilising differing post-cue time windows and frequency bands to one another. This study aims to assess how the simultaneous optimisation of both these parameters impact MI classification performance. This is done by iteratively training and testing a series of subject-specific models on different combinations of frequency bandwidth and time window options across 109 subjects. This is followed by a statistical analysis using repeated measures ANOVA to uncover significant differences between different bandwidths and time windows in terms of accuracy across the patient cohort. The resulting visualisations and statistical tests show that there are, indeed, significant differences between both specific time windows and specific bandwidths in terms of accuracy. While the comparison of classification accuracies across 23 frequency bandwidths during five different time windows demonstrates an optimal temporal and spectral scale combination of (0, 4) s at the range of (4, 12) Hz across all subjects, the subjects demonstrate similar accuracies for other parameter combinations. These findings highlight the efficacy of personalised models to detect optimal temporal and spectral parameter combinations to best classify MI
EEG signals that inherently vary across subjects.
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All authors Matthew A. McCartney, Liisa A. Kivioja, Sonal S. Baberwal, Shirley Coyle
Image and Video Processing
Local-sensitive connectivity filter (ls-cf): A post-processing unsupervised improvement of the frangi, hessian and vesselness filters for multimodal vessel segmentation
Erick O Rodrigues, Lucas O Rodrigues, João HP Machado et al. (+5 more)
A retinal vessel analysis is a procedure that can be used as an assessment of risks to the eye. This work proposes an unsupervised
multimodal approach that improves the response of the Frangi filter, enabling automatic vessel
segmentation. We propose a filter that computes pixel-level vessel continuity while introducing a local tolerance heuristic to fill in vessel discontinuities produced by the Frangi response. This proposal, called the local-sensitive connectivity filter (LS-CF), is compared against a naive connectivity filter to the baseline thresholded Frangi filter response and to the naive connectivity filter response in combination with the morphological closing and to the current approaches in the literature. The proposal was able to achieve competitive results in a variety of
multimodal datasets. It was robust enough to outperform all the state-of-the-art approaches in the literature for the OSIRIX angiographic
dataset in terms of accuracy and 4 out of 5 works in the case of the IOSTAR
dataset while also outperforming several works in the case of the DRIVE and STARE
datasets and 6 out of 10 in the CHASE-DB
dataset. For the CHASE-DB, it also outperformed all the state-of-the-art unsupervised methods.
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All authors Erick O Rodrigues, Lucas O Rodrigues, João HP Machado, Dalcimar Casanova, Marcelo Teixeira, Jeferson T Oliva, Giovani Bernardes, Panos Liatsis
Signal Processing · Cross-listed from physics.optics
Artificial Intelligence Reshapes Microwave Photonics
Peng Li, Xihua Zou, Jia Ye et al. (+2 more)
As a rapidly emerging interdisciplinary field that intrinsically integrates microwave and photonics, microwave photonics (MWP) provides disruptive solutions to overcome the fundamental bandwidth of conventional electronic systems. By exploiting the inherently ultra-wide bandwidth and low-loss characteristics of photonic technologies, MWP enables the generation, transmission, processing, and detection of microwave, millimeter-wave, and terahertz signals. Representative breakthroughs include fully photonic microwave radar systems, photonic analog-to-digital converters with bandwidth up to 320 GHz, and photonic wireless communication systems achieving data rate as high as 616 Gbit/s. Meanwhile, the rapid growth of artificial intelligence (AI) is reshaping scientific research, engineering, and daily life in unprecedented ways, such as AI for science/engineering and AI co-scientist/assistant. Correspondingly, AI is profoundly reshaping MWP in all aspects, ranging from signal generation, transmission to signal processing and detection. AI has revolutionized the design, simulation, fabrication, testing, deployment, and maintenance of MWP systems, delivering autonomous operation and exceptional efficiency beyond traditional systems. Motivated by these developments, this Review Paper provides the first comprehensive overview of AI-enabled MWP, systematically summarizing the state-of-the-art advances and presenting insights for both the academic community and the broader public.
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All authors Peng Li, Xihua Zou, Jia Ye, Wei Pan, Lianshan Yan
Systems and Control
Reinforcement Learning-based Control via Y-wise Affine Neural Networks: Comparative Case Studies for Chemical Processes
Austin Braniff and Yuhe Tian
In this work we present an efficient and practically implementable approach for the application of reinforcement learning (RL)-based control in chemical process systems. This is an area that has yet to widely adopt RL-based control largely due to inherent challenges in trusting RL
algorithms and the time-consuming process of training reliable
agents. To address these challenges, we leverage a class of RL
algorithms termed Y-wise Affine Neural Network (YANN)- RL, which we have developed in our prior work (Braniff and Tian, 2025a). By strategically initializing actor and critic networks YANN-RL
algorithms provide confident and interpretable starting points within control schemes. We apply this RL-based control approach to three different process engineering case studies publicly available on the PC-Gym library (Bloor et al., 2026): (i) a continuous stirred tank reactor (CSTR), (ii) a four-tank system, and (iii) a multistage extraction column. Our approach is compared to several popular RL
algorithms (PPO, SAC, DDPG, and TD3) and is benchmarked against nonlinear model predictive control (NMPC). These case studies demonstrate that YANN-RL can greatly reduce the training time and data needed, can be deployed with confidence for chemical process systems, and can approach the performance of NMPC without the knowledge of a full nonlinear model.
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Systems and Control
Collaborative Optimization Framework of Battery Charging / Swapping Stations for eVTOLs Based on Closed-Loop Supply Chain and Space-Time Network
Pengfeng Lin, Miao Zhu, Jiahui Sun et al. (+3 more)
Electric vertical take-off and landing (eVTOL) aircraft, by virtue of their advantages such as high efficiency, environmental friendliness, and low noise, are regarded as an effective means of alleviating urban traffic congestion. Although eVTOLs have policy support, industrial foundations, and
market prospects globally, their commercialization process still faces obstacles. Purely electric eVTOLs confront constraints including limited battery energy density, high operational power requirements, and challenges associated with rapid energy replenishment, which collectively restrict their flight endurance and application scenarios. To tackle these issues, following an investigation into battery energy replenishment strategies, a closed-loop supply chain-based optimization framework for eVTOL battery charging and swapping is proposed. First, a time-space network technique is employed to solve the modeling challenge of an efficient and flexible battery transportation system between charging stations and swapping stations. Subsequently, aiming to maximize the operational revenue of the model, optimized management of battery swapping, transportation, and charging processes is implemented, facilitating coordinated operation among eVTOLs, swapping stations, and charging stations. On this basis, the model is solved by Gurobi, verifying its feasibility. Finally, the results of sensitivity analysis show that the model performs excellently in several aspects, including battery swap service quality, system sustainability, and operational resilience.
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All authors Pengfeng Lin, Miao Zhu, Jiahui Sun, Haoyang Cui, Chuanlin Zhang, Yunda Yan
Signal Processing · Cross-listed from cs.IT
On the Identifiability of Semi-Blind Estimation in Cell-Free Massive MIMO Networks
Christian Forsch and Laura Cottatellucci
Semi-blind joint channel estimation and data detection (JCD) is a promising approach to mitigate pilot contamination in
cell-free massive multiple-input multiple-output (CF-MaMIMO) networks. The effectiveness of such methods fundamentally depends on identifiability, i.e., the ability to unambiguously recover the unknown channel coefficients and transmitted data signals from the received uplink observations. In this work, we investigate the identifiability of semi-blind JCD from a large-scale system design perspective. We consider a CF-MaMIMO network in which access points (APs) and user equipments (UEs) are spatially distributed according to Poisson point processes (PPPs). The resulting network
topology is modeled as bipartite random
geometric graph (BRGG) that captures local connectivity induced by wireless propagation. To enable a tractable analysis, the spatially dependent graph model is approximated by a surrogate independent-edge random graph with matched degree distributions. Building on this model, we develop a recursive probabilistic analysis that characterizes the conditions under which semi-blind recovery succeeds with high probability. The proposed analysis reveals an identifiability region as a function of key system parameters, including AP and UE densities and the connectivity radius beyond which channel coefficients are assumed negligible. Monte Carlo simulations validate the predicted identifiability region and assess the accuracy of the proposed graph approximation. The proposed framework provides system level insights into how network density and connectivity affect identifiability in large-scale CF-MaMIMO systems and offers guidelines for selecting deployment parameters and pilot sequence lengths that enable reliable semi-blind recovery.
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Systems and Control
Coordinated Optimal Power Quality Management in Distribution Systems Using The Residual Capacity of Community IBRs
Tiantian Ji, Pengfeng Lin, Miao Zhu et al. (+3 more)
This letter proposes a network-wide coordinated optimization model to mitigate voltage unbalance (VU) by unleashing the remaining capacity of community inverter-based resources (IBRs). Existing single-sequence strategies ignore coupled capacity constraints and cause idle headroom. Meanwhile, they fail to harness the collective governance capabilities of community IBRs. To solve this discrepancy and exploit the unused potential, we developed a sequence-domain network model in dual commonly shared synchronous reference frames. Strict phase current and apparent power limits are formulated and convexified via polyhedral approximations. A quadratic objective function flexibly balances sequence capacity allocation. Simulation and experimental results validate the effectiveness of the proposed strategy.
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All authors Tiantian Ji, Pengfeng Lin, Miao Zhu, Stephan M. Goetz, Ahmed Abu-Siada, Syed Islam