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Non-holonomic mobile manipulator NMPC for occlusion avoidance based on elliptic cone FOV representation
No full textInternational audienceIn recent years, robots have been deployed outside factories, in unstructured environments such as agricultural fields. This challenge requires the robot to operate in complex environments with people nearby. This paper studies a mobile manipulator equipped with a camera, working in vine fields alongside an agricultural worker. To perform the task, the robot must move through a cluttered environment while keeping the worker in its field of view. To this end, this paper proposes a nonlinear model predictive control (NMPC) allowing the mobile manipulator to avoid obstacles while preserving the person in the field of view. The proposed method relies on modelling the field of view of the camera as well as the obstacles in the 3D space. Several simulations of increasing difficulty are presented in which the entire system must follow the trajectory while avoiding obstacles. The results showed that the proposed approach is capable of keeping the worker in view and performing the task, even in critical cases with multiple obstacles and a moving worker
A Modular Execution Architecture for Robust Multi-Robot Planning and Acting in Trans-Media Environments
No full textIn complex missions involving heterogeneous multi-robot teams, especially in transmedia systems that operate across environments such as air and water, robust execution frameworks must ensure both temporal coherence and resilience to uncertainty. These challenges stem from the need to manage dynamic mode transitions, closely linked inter-agent tasks, and execution-time failures. This paper introduces the Adaptive and Modular Architecture (AMA) Execution and Planning components. AMA-EXEC is a distributed execution framework designed to enable coherent, fault-tolerant mission execution in such conditions. AMA-EXEC uses the plans produced by AMA-PLAN, a PDDL-based planning framework. AMA-EXEC incorporates Simple Temporal Networks (STNs) to facilitate temporal reasoning; modular BTs to enable distributed execution; and runtime monitoring mechanisms to categorize failures, propagate delays, and execute partial replanning. In contrast to centralized, monolithic systems, AMA-EXEC organizes execution around collaborative robot teams and leverages real-time feedback to maintain synchronization and temporal alignment under disturbances. The framework's validation process involves the execution of simulated trans-media missions, encompassing concurrent tasks and a range of failure scenarios. The findings indicate enhanced execution continuity, extended complex cases application, and robust failure recovery in comparison to baseline methodologies. The AMA-EXEC system's modularity and generalizability render it suitable for a wide range of applications, including environmental monitoring, distributed exploration, and search-and-rescue operations
An extension of the mean value theorem
No full textTo appear in "The Mathematical Intelligencer"Let (Ω, µ) be a measure space with Ω ⊂ R d and µ a finite measure on Ω. We provide an extension of the Mean Value Theorem (MVT) in the formIt is valid for non compact sets Ω and f is only required to be integrable with respect to µ. It also contains as a special case the MVT in the form f dµ = µ(Ω)f (x 0 ) for some x 0 ∈ Ω, valid for compact connected set Ω and continuous f . It is a direct consequence of Richter's theorem which in turn is a non trivial (overlooked) generalization of Tchakaloff's theorem, and even published earlier.</p
In-situ-monitored Chemical Vapor Deposition of silicon oxynitride layers
No full textInternational audienceAn in-situ monitoring system based on reflectometry and optical emission spectroscopy has been designed and installed on a PECVD equipment and it has been shown to provide real-time information that will facilitate the fabrication of single and multilayer thin films of controlled thickness and composition
Insights into Oxygen Vacancy Effects on Ferroelectric Behavior of Hafnium Oxide: A Review
No full textInternational audienceFerroelectricity in hafnium oxide thin films has become a scalable and silicon‐compatible solution for nonvolatile memory and logic applications. The orthorhombic ferroelectric phase, while metastable, becomes accessible through oxygen vacancies, which play a complex role in enabling and degrading device performance. Controlled vacancy incorporation can stabilize polarization and enhance endurance, while uncontrolled migration under an electric field leads to wake‐up effects, fatigue, imprint, and leakage. This review examines how oxygen vacancies influence ferroelectric phase formation, switching behavior, and reliability in hafnium oxide systems. First‐principles simulations reveal that vacancy charge states modulate phase energetics and dipole formation. Experimental methods—including X‐ray photoelectron spectroscopy, electron paramagnetic resonance, and electron energy loss spectroscopy—offer insight into vacancy distributions at the atomic scale. Vacancy behavior is linked to remnant polarization stability and switching degradation at the device level. Process strategies such as dopant engineering, thermal annealing, and interface design are shown to be critical for vacancy control. A deeper understanding of vacancy dynamics, combined with in situ characterization and predictive modeling, is essential for advancing hafnium oxide‐based ferroelectric memories and neuromorphic architectures
Merging bioelectrochemical transducer and antenna functions for continuous monitoring in biological tissues: an innovative volume-saving strategy
No full textInternational audienceThe continuous monitoring of physiological parameters can provide crucial information to better understand and treat health disorders more efficiently. However, because the size of implantable sensors remains generally too large, numerous parts of the body can still not be accessed. We propose here to combine in a synergistic way the two most volumetric functions of a typical sensing device, i.e. the energy supply and the communication unit, to reduce the overall device footprint. The electrode of a biofuel cell (BFC), whose role is to deliver DC current, is merged with the antenna electrode, whose function is to provide radiofrequency alternating current, transforming de facto the BFC electrode into an antenna. This first proof-of-concept BFC, acting at the same time as an energy source and an antenna, enables wireless communication of glucose concentration over macroscopic distances. A novel dielectric screening strategy is also proposed as a trade-off between the analyte diffusion (BFC function), and electric field preservation (wireless communication function) to optimize the overall efficiency. Finally, we demonstrate that the integrity of the proposed device can be maintained after subcutaneous implantation in rats. These results pave the way for wireless miniaturized implantable devices for continuous monitoring in biological tissues.</div
Spatial confinement and life under pressure from physiology to pathology
No full textInternational audienceTree roots sprouting into the ground or tumors proliferating within an organ are a few examples ofproliferation under spatial confinement, which leads to growth-induced pressure. This compressivemechanical stress can impact a plethora of processes in all organisms. In this review, I will discuss thephysiological and pathological consequences of spatial confinement in plants, microbes and animalcells, and will discuss in more depth the case of solid tumors
Safety Factories -a Manifesto
No full textInternational audienceModern cyber-physical systems are operated by complex software that increasingly takes over safety-critical functions. Software enables rapid iterations and continuous delivery of new functionality that meets the ever-changing expectations of users. As high-speed development requires discipline, rigor, and automation, software factories are used. These entail methods and tools used for software development, such as build systems and pipelines. To keep up with the rapid evolution of software, we need to bridge the disconnect in methods and tools between software development and safety engineering today. We need to invest more in formality upfront -capturing safety work products in semantically rich models that are machine-processable, defining automatic consistency checks, and automating the generation of documentation -to benefit later. Transferring best practices from software to safety engineering is worth exploring. We advocate for safety factories, which integrate safety tooling and methods into software development pipelines
Positively not SOS: pseudo-moments and extreme rays in exact arithmetic
No full textA polynomial that is a sum of squares (SOS) of other polynomials is evidently positive. The converse is not true, there are positive polynomials which are not SOS. This note focuses on the problem of certifying, in exact arithmetic, that a given positive polynomial is not SOS. Using convex duality, this can be achieved by constructing a separating linear functional called a pseudo-moment certificate. We present constructive procedures to compute such certificates with rational coefficients for several famous forms (homogeneous polynomials) that are known to be positive but not SOS. Our method leverages polynomial symmetries to reduce the problem size and provides explicit integer-based formulas for generating these rational certificates. As a by-product, we can also generate extreme rays of the pseudomoment cone in exact arithmetic
Understanding the Impact of Value Selection Heuristics in Scheduling Problems
No full textInternational audienceIt has been observed that value selection heuristics have less impact than other heuristic choices when solving hard combinatorial optimization (CO) problems. It is often thought that this is because more time is spent on unsatisfiable sub-problems where the value ordering is irrelevant. In this paper we investigate this belief in the scheduling domain and come up with a more detailed explanation. We find that, even though there are less relevant choices to be made on hard instances, each mistake tends to have a bigger impact, to a point where the potential gain from a value heuristic predominates. Moreover, we observe two interesting and relatively surprising phenomena when solving scheduling problems. First, the accuracy of a given value selection heuristic decreases with the optimality gap. Second, the computational penalty of a mistake increases with the accuracy of the heuristic. For the first observation, we argue that on hard problems, constraint propagation removes a large portion of choices that align with the intuition behind the heuristic. This means that the heuristic faces mostly difficult choices. For the second observation, we argue that simple heuristics tend to make more mistakes on intuitive choice points, and the computational cost for refuting these mistakes is smaller than for those made by a more accurate heuristic