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Real-time Interior-point solver for Optimal Torque Control of IPMSMs
No full textInternational audienceThis paper presents a unified convex formulation for optimal torque control (OTC) of interior permanent-magnet synchronous motor (IPMSM). By introducing a change of variables, the originally multi-variable optimization problem is reformulated into a single-variable problem applicable across both maximum torque per ampere (MTPA) and field-weakening (FW) operating points. This approach eliminates the traditional need for case-by-case logic to identify operating regions and optimal current. A key contribution of this work is a formal proof of the convexity of the reformulated optimization problem, which is achieved through sum-of-squares (SoS) programming. This theoretical guarantee enables the use of efficient convex optimization techniques such as interior point method (IPM), and the efficient integration of OTC problems in more complex frameworks. A lightweight solver is developed to minimize joule losses under voltage and current constraints for a given torque demand. Experimental validation on an IPMSM test bench confirms both the computational efficiency and practical viability of the proposed control strategy.</div
Deployment mechanisms of satellite solar arrays using Shape memory alloys: literature review and CubeSat U3 case study
No full textThis research explores the innovative use of Shape Memory Alloys (SMAs) as actuators in the deployment mechanisms of spacecraft solar arrays, specifically focusing on small-size satellites such as the CubeSat U3 model. Traditional deployment systems rely on mechanical components that may be susceptible to failure due to their complexity and the harsh conditions of space. SMAs offer a promising alternative due to their ability to remember and revert to a pre-defined shape when heated above a transformation temperature, thus simplifying the deployment mechanism and reducing potential failure.The research began with the development of an initial force equilibrium model to simulate the behavior of an SMA beam integrated with a copper wire, which acts as a heating element. This model was used to perform preliminary simulations to evaluate the viability of SMAs for deploying solar arrays in space. The research was conducted using a CubeSat U3 as a case study. The results confirmed that SMAs could effectively replace traditional actuators, providing a more reliable and simpler deployment method. SMAs as actuators are not limited to the CubeSat U3 but can be flexibly applied to a wide range of satellites with similar deployment requirements. Therefore, they could open up new possibilities for further research
Antiferroelectric Fluorite for High Energy Storage Applications
No full textInternational audienceOver the past fifteen years, fluorite-structured ferroelectric and antiferroelectric ultrathin films have gained interest for high-density applications. Antiferroelectric ZrO2 shows promise for nanosupercapacitors due to its potential for high energy storage density (ESD) and efficiency (η). This study investigates high-performance Hf1-xZrxO₂ thin films with TiN electrodes exhibiting linear dielectric (LD), ferroelectric (FE), and antiferroelectric (AFE) behavior. AFE ZrO₂ stands out, offering the best trade-off between energy storage density (ESD) and efficiency (η). At 3.5 MV/cm, it achieves 52 J/cm³ with 75% efficiency, reaching 84 J/cm³ at 4.0 MV/cm. Optimization in temperature and thickness leads to a record ESD of 125 J/cm³ for a 10.3 nm-thick ZrO2 thin film. While efficiency and endurance require further improvement, these results confirm AFE ZrO₂ as a promising candidate for high-performance supercapacitors
Galois groups of reductions modulo p of D-finite series
No full textThe aim of this paper is to investigate the algebraicity behavior of reductions of -finite power series modulo prime numbers. For many classes of D-finite functions, such as diagonals of multivariate algebraic series or hypergeometric functions, it is known that their reductions modulo prime numbers, when defined, are algebraic. We formulate a conjecture that uniformizes the Galois groups of these reductions across different prime numbers. We then focus on hypergeometric functions, which serves as a test case for our conjecture. Refining the construction of an annihilating polynomial for the reduction of a hypergeometric function modulo a prime number p, we extract information on the respective Galois groups and show that they behave nicely as p varies
A high voltage, high current transmission-line-pulse testbench for the reliability investigation of deep depletion, metal-insulator-semiconductor trench capacitors
No full textInternational audienceThis paper presents a work-in-progress design of a transmission-line-pulse testbench (TLPTB) for the investigation of the reliability of deep depletion, on-metal insulator semiconductor (MIS) capacitor at wafer level scale. Firstly, we describe the capacitor (DUT) and the targeted application requiring the investigation of reliability: a snubber for wide-band gap (WBG) transistor. Then we explain the capacitor ageing mechanism induced specifically in the snubber application. We need to stress the capacitor repeatedly under high voltage (1000 V) and high current (100 A). The TLPTB is suitable for such stress pattern. The design is based on SPICE simulation prior to a board layout design. The theoretical subsection describes the expected stress sequence. The physical implementation is discussed along with a measurement setup
Truck bond graph model for sizing the power steering system
No full textInternational audienceIn this paper, a bond graph model of a 4 × 2 truck, integrating both multibody and functional approaches is presented. The relevance of the model is assessed by numerical simulation results comparison w.r.t. a reference multibody model. Then, using the inverse-based methodology in the bond graph framework, the sizing of the electric power steering assistance is addressed. Simulation of the inverse model identifies the performance requirements that the electric power assistance system must meet to respect the specifications
Hoeffding decomposition of functions of random dependent variables
No full textInternational audienceHoeffding's functional decomposition is the cornerstone of many post-hoc interpretability methods. It entails decomposing arbitrary functions of mutually independent random variables as a sum of interactions. Many generalizations to dependent covariables have been proposed throughout the years, which rely on finding a set of suitable projectors. This paper characterizes such projectors under hierarchical orthogonality constraints and mild assumptions on the variable's probabilistic structure. Our approach is deeply rooted in Hilbert space theory, giving intuitive insights on defining, identifying, and separating interactions from the effects due to the variables' dependence structure. This new decomposition is then leveraged to define a new functional analysis of variance. Toy cases of functions of bivariate Bernoulli and Gaussian random variables are studied
Principaloid bundles
No full text50 pages, 1 figureWe present a novel generalisation of principal bundles -- principaloid bundles: These are fibre bundles where the typical fibre is the arrow manifold of a Lie groupoid and the structure group is reduced to the latter's group of bisections. Each such bundle canonically comes with a bundle map to another fibre bundle over the base , with typical fibre . Examples of principaloid bundles include ordinary principal -bundles, obtained for , bundles associated to them, obtained for action groupoids , and general fibre bundles if is a pair groupoid. While is far from being a principal -bundle, we prove that is one. Connections on the principaloid bundle are thus required to be -invariant Ehresmann connections. In the three examples mentioned above, this reproduces the usual types of connection for each of them. In a local description over a trivialising cover of , the connection gives rise to Lie algebroid-valued objects living over bundle trivialisations of . Their behaviour under bundle automorphisms, including gauge transformations, is studied in detail. Finally, we construct the Atiyah-Ehresmann groupoid which governs symmetries of , this time mapping distinct -fibres to one another in general. It is a fibre-bundle object in the category of Lie groupoids, with typical fibre and base . We show that those of its bisections which project to bisections of its base are in a one-to-one correspondence with automorphisms of
Eco‐Friendly Deposition of Catalyst‐Free Graphene on Diverse Substrates
No full textInternational audienceThe increasing demand for environmentally friendly and low‐energy consumption fabrication methods has slowed the advancement of graphene technology. In this work, a catalyst‐free method is presented for the deposition of high‐quality graphene on diverse substrates using ethylene. Through the utilization of a low‐pressure plasma‐enhanced chemical vapor deposition (PECVD) technique at ambient temperature, followed by flash annealing, it demonstrates the growth of graphene films on diverse substrates including silicon, silicon dioxide, metal foils, quartz, fluorine doped tin oxide, glass and polyamide, without the reliance on metal catalysts. The approach employs ethylene as a carbon donor free of a reducing agent, hence ensuring minimal environmental impact during the fabrication process. It also allows direct deposition on desired medium without the need for further complex transfer process. Comprehensive characterizations confirm the successful formation of graphene films with uniform thickness of 3–10 layers and with high structural integrity while showcasing a resistivity of 3.52·10 −4 Ω.cm. Thanks to its superhydrophobic nature, the graphene directly deposited onto scanning microwave microscopy tip demonstrates an improved resolution as compared to a graphene‐free tip. The eco‐friendly approach, coupled with its versatility regarding the substrate compatibility, offers promising prospects for sustainable graphene production
Bounding the degree of generic sharp transitivity
No full textWe show that a generically sharply t-transitive permutationgroup of finite Morley rank on a set of rank r satisfies t r+2 providedthe pointwise stabilizer of a generic (t − 1)-tuple is an L-group, whichholds, for example, when this stabilizer is solvable or when r 5. Thismakes progress towards establishing the natural bound on t implied bythe Borovik-Cherlin conjecture that every generically (r + 2)-transitivepermutation group of finite Morley rank on a set of rank r is of the formPGLr+1(F) acting naturally on Pr(F).Our proof is assembled from three key ingredients that are indepen-dent of the main theorem—these address actions of Alt(n) on L-groupsof finite Morley rank, generically 2-transitive actions with abelian pointstabilizers, and simple groups of rank 6