Nonlinear adaptive sliding mode control of a powertrain supplying fuel cell hybrid vehicle

International audienceThis paper presents an adaptive sliding mode based switching scheme for controlling DC-DC hybrid powertrain for propulsion of a Fuel Cell / Supercapacitor hybrid vehicle. After modeling the powertrain, a new approach to determine a nonlinear sliding surface ensuring stability of the DC/DC Boost converter is discussed. This was achieved without introducing the equivalent control aspect after transforming the instantaneous model of the Boost in a suitable form. The presented technique is also applied for trajectories tracking in the entire powertrain, which includes a dc/dc Boost converter associated to Fuel Cell stack and another Bidirectionnel dc/dc converter associated to the supercapacitor bank, which are both working in parallel to provide electricity propelling the vehicle. The control scheme is tested with driving cycle example through simulation

Impulse magnetized magnetic screws

This paper is an investigation in the performance of two types of magnetic screws (MSs). The first is the magnet to magnet and consists of permanent magnet (PM) nut and PM screw and the second is a magnet to reluctance and consists of PM nut and a double-start reluctance screw. It is argued that for cost sensitive and long stoke applications, a magnet-to-reluctance MS may be the preferred option. It is also shown that capacitor discharge magnetization techniques can be employed for imprinting helical magnetization distributions on cylindrical PMs, significantly reducing the complexity and facilitating the practical realization of MS systems

A Predictive power control of Doubly Fed Induction Generator for Wave Energy Converter in Irregular Waves

International audienceIn last decades, renewable energy resources are considered as an alternative energy resource to the world's excessive energy demand. An extremely abundant and promising source of energy exists in oceans. Currently, there are several wave energy converters to harness this energy. Some of them, as in tidal applications, use the Doubly-fed induction generator. This paper deals then with a predictive power control of this generator based Wave Energy Converter under irregular wave climate which is modeled as time series elevation from using Bretschneider spectra. In the proposed control approach, the predicted output power was calculated using a linearized state-space model. The DFIG-based WEC power tracking performances further illustrates the dynamic features of the proposed predictive power control approach

Ocean Wave Converters: State of the Art and Current Status

International audienceSolutions to today energy challenges need to be explored through alternative, renewable and clean energy sources to enable a diverse energy resource plan. An extremely abundant and promising source of energy exists in oceans. Ocean energy exists in many forms. Among these forms, significant opportunities and benefits have been identified in the area of ocean wave energy extraction, i.e., harnessing the wave motions and converting them into electrical energy. Regarding this emerging and promising area of research, this paper presents ocean wave energy fundamentals and then reviews the fundamental concepts and the main projects around the world. It also reports issues regarding electrical generator topologies associated to wave energy converters

Optimal Trajectories for Propellant-Free Rendezvous Missions

The paper provides a new approach to utilizing space environmental forces in time- and energy-optimal, propellant-less spacecraft rendezvous missions. Considering the nonlinear form of the relative dynamic equations, rendezvous missions are posed as optimal control problems subject to input saturation. We conduct a direct optimal control approach to obtain optimal trajectories and control inputs. Initially, we consider the differential drag only and conduct a comprehensive analysis of the effect of altitude on the required control input and achieved cost function. Lorentz forces are then utilized with the differential drag, reducing the time required for time-optimal missions. For energy-optimal missions with combined differential drag and Lorentz forces, a weighting matrix in the cost function is introduced to adjust the relative contributions of these forces

Power Quality Improvement of a Solar Energy Conversion System by a Coordinated Active and LCL Filtering

Power converters play an essential role in Photovoltaic (PV) system to maximize the power transfer to the electrical grid. However, the generated harmonics in the grids due to these power converters and nonlinear loads are considered one of the encountered problems to overcome. This paper presents a decoupled control of PV field real power and reactive power injected to the high voltage network via a PWM inverter by using fuzzy logic controllers. Elsewhere, a procedure based on a coordinated active and LCL filtering is proposed to mitigate the harmonic current introduced by a nonlinear load and the inverter itself in such a way to enhance the power quality injected into the grid. The results obtained in the present study show the good performance of the suggested hybrid filtering approach and demonstrate that almost all harmonics orders of the grid current are well mitigated; the current Total Harmonic Distortion (THD) meets its standard and consequently the power quality is considerably enhanced

Multicomponent reactions under increased pressure: on the reaction of arylhydrazonals, aromatic aldehydes and malononitrile in Q-Tube

A novel multi-component reaction between arylhydrazonals, malononitrile and aromatic aldehydes under high pressure utilizing Q-tube was carried out. The reaction of arylhydrazonal (1j) with malononitrile and aromatic aldehydes afforded the corresponding biphenyl derivatives (4). However, compound 1h reacted with malononitrile and aromatic aldehydes (7) to afford pyridazino[5,4,3-de]1,6-naphthyridine-7-carbonitrile derivatives (8). In contrast, the arylhydrazonal (1k) at the same reaction conditions afforded the corresponding pyridazinoquinazoline derivative (22). A rationalization for the difference in behavior for reaction of compounds 1h-k with malononitrile and aromatic aldehydes was postulated. Based on these findings a mechanism to account for the formation of the reaction products is suggested excluding possible initial dimerization of malononitrile as has been previously reported

UM ESTUDO EDUCACIONAL SOBRE O EFEITO DA ANSIEDADE FUTURA NO PROGRESSO ACADÊMICO DE ESTUDANTES UNIVERSITÁRIOS : (ALUNOS DA UNIVERSIDADE PRÍNCIPE SETAM BIN ABDULAZIZ)

The aim of this study was to An educational study of the effect of future anxiety on the academic progress of university students. Generally, Future anxiety means the score that a student obtains on the Future Anxiety Scale. This study aims at identifying the level of future anxiety among the students of Prince Sattam Bin Abdul-Aziz University. It attempts to highlight the differences between them in light of variable according to gender. It also seeks to underscore the impact of future anxiety on their academic achievement and the reasons for this anxiety and the suggested treatment. To achieve this goal, the researcher uses the descriptive analytical method to collect and analyze the data. The study is conducted on a sample of (60) male and female students in the academic year (2022/2023). The study sample was selected using stratified random sampling.O objetivo deste estudo foi realizar um estudo educacional sobre o efeito da ansiedade futura no progresso acadêmico de estudantes universitários. Geralmente, Ansiedade futura significa a pontuação que um aluno obtém na Escala de Ansiedade Futura. Este estudo tem como objetivo identificar o nível de ansiedade futura entre os alunos da Universidade Príncipe Sattam Bin Abdul-Aziz. Tenta destacar as diferenças entre eles à luz das variáveis de acordo com o gênero. Procura também sublinhar o impacto da ansiedade futura no seu desempenho académico e as razões dessa ansiedade e o tratamento sugerido. Para atingir esse objetivo, o pesquisador utiliza o método analítico descritivo para coletar e analisar os dados. O estudo é realizado numa amostra de (60) estudantes do sexo masculino e feminino no ano letivo (2022/2023). A amostra do estudo foi selecionada por meio de amostragem aleatória estratificada

The effects of circuit exercise training strategy on health-related physical fitness level and biomarkers in elderly people with cardiovascular diseases

This study investigated the effects of a 12-week circuit exercise training intervention on health-related physical fitness and biomarkers in elderly adults with cardiovascular diseases. A total of 69 participants underwent the circuit exercise training program, which included stretching, aerobic activity, and weight training. The results showed that the participants had improved performance in cardiovascular and strength tests, with grip and back muscle strength showing improvement. However, sit-ups were lower than the average, and power, reaction time, and agility needed more effort. The high sensitivity C-reactive protein value reached a medium infection risk level for cardiovascular illnesses. The study concluded that there was a strong association between health-related physical fitness and biomarker index in senior persons with a medium risk cluster of cardiovascular illnesses. The study also found that BMI correlated positively with biomarker index, while cardiovascular fitness, agility, and flexibility correlated negatively with biomarker index

Monte Carlo Grid Dynamic Programming: Almost Sure Convergence and Probability Constraints

Dynamic Programming (DP) suffers from the well-known ``curse of dimensionality'', further exacerbated by the need to compute expectations over process noise in stochastic models. This paper presents a Monte Carlo-based sampling approach for the state space and an interpolation procedure for the resulting value function, dependent on the process noise density, in a "self-approximating" fashion, eliminating the need for ordering or set-membership tests. We provide proof of almost sure convergence for the value iteration (and consequently, policy iteration) procedure. The proposed meshless sampling and interpolation algorithm alleviates the burden of gridding the state space, traditionally required in DP, and avoids constructing a piecewise constant value function over a grid. Moreover, we demonstrate that the proposed interpolation procedure is well-suited for handling probabilistic constraints by sampling both infeasible and feasible regions. While the curse of dimensionality cannot be entirely avoided, this approach offers a practical framework for addressing lower-order stochastic nonlinear systems with probabilistic constraints, where traditional DP methods may be intractable or inefficient. Numerical examples are presented to illustrate the convergence and convenience of the proposed algorithms.Comment: 6 pages, 1 figur