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Dynamic event-triggered fault-tolerant cooperative resilient tracking control with prescribed performance for UAVs

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Science China(Information Sciences) 2024年第8期67卷 67-84页

作者： Rong YUAN Zhengcai AN Shuyi SHAO Mou CHEN Mihai lungu College of Automation Engineering Nanjing University of Aeronautics and Astronautics Science and Technology on Electro-optic Control Laboratory Faculty of Electrical Engineering University of Craiova Aerospace Engineering Doctoral School University Politehnica of Bucharest

In this paper, a resilient tracking control scheme with cooperative collision avoidance performance is studied for the fixed-wing unmanned aerial vehicle(UAV) leader-follower formation in the presence of actuator failures and external disturbances. Firstly, based on the control objectives of UAV formation tracking and collision avoidance, the transformation tracking errors are obtained using the prescribed performance control technique. Next, a fault detection mechanism is introduced to determine if there is the actuator fault. Subsequently, the event-triggered resilient fault observers are designed based on a dynamic eventtriggered mechanism to estimate actuator faults. Furthermore, the prescribed performance functions and the H∞ performance index are employed to ensure the UAV formation collision-free and mitigate the impact of disturbances. Moreover, the resilient controller is designed to minimize the effect of the perturbations for the control gain and the fault observer gain on the system. The stability of the system is also proven through the Lyapunov stability analysis, and the controller gains are calculated by solving the linear matrix ***, the validity of the proposed control strategy is demonstrated by the simulation analysis.

关键词： cooperative collision avoidance event-triggered fault observer prescribed performance resilient control UAV formation

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Performance, Combustion and Emission Characteristics of Oxygenated Diesel in DI Engines: A Critical Review

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Journal of Power and Energy Engineering 2024年第6期12卷 16-49页

作者： Joseph lungu Lennox Siwale Rudolph Joe Kashinga School of Engineering The Copperbelt University Riverside Campus Kitwe Zambia

The transition from non-renewable to renewable energy sources is a significant challenge of our time. In the fuel industry, oxygenated additives such as butanol are transforming conventional fuels into renewable biofuels. This technology has been utilized in reciprocating engines for decades. This paper reviews the viability of using an n-butanol blend as a short-term replacement for diesel by analyzing its physical and chemical properties, combustion, performance, and emission characteristics in compression ignition (CI) engines under various conditions, including variable load, speed, acceleration, and both stationary and transient cycles. N-Butanol exhibits higher viscosity, better lubricity, higher heating value, improved blend stability, enhanced cold-flow properties, and higher density. These factors influence spray formation, injection timing, atomization, and combustion characteristics. Its higher oxygen content improves the diffusion combustion stage and efficiency. Adding 5% and 10% n-butanol to diesel increases pressure and apparent heat release rate, slightly reduces temperature, and improves thermal efficiency, with mixed effects on CO and THC emissions and a notable decrease in particulate matter emissions. Fuel consumption increases, while the impact on NOx emissions varies. A 10% butanol blend is considered optimal for enhancing performance and reducing particulate emissions without significantly affecting NOx emissions. Blending up to 40% butanol with diesel does not require engine modifications or ECU recalibrations in engines calibrated for pure diesel. Due to its advantageous properties and performance, n-butanol is recommended as a superior alcohol-diesel blend than ethanol for short-term diesel replacement.

关键词： Diesel Engine Alcohol Additives N-Butanol Combustion and Properties

Automatic landing system using neural networks and radio-technical subsystems

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Chinese Journal of Aeronautics 2017年第1期30卷 399-411页

作者： Romulus lungu Mihai lungu University of Craiova Faculty of Electrical Engineering

The paper focuses on the design of a new automatic landing system（ALS） in longitudinal plane; the new ALS controls the aircraft trajectory and longitudinal velocity. Aircraft control is achieved by means of a proportional-integral（PI） controller and the instrumental landing system– the first phase of landing（the glide slope） and a proportional-integral-derivative（PID） controller together with a radio-altimeter – the second phase of landing（the flare）; both controllers modify the reference model associated with aircraft pitch angle. The control of the pitch angle and longitudinal velocity is performed by a neural network adaptive control system, based on the dynamic inversion concept, having the following as components： a linear dynamic compensator, a linear observer, reference models, and a Pseudo control hedging（PCH） block. The theoretical results are software implemented and validated by complex numerical simulations; compared with other ALSs having the same radio-technical subsystems but with conventional or fuzzy controllers for the control of aircraft pitch angle and longitudinal velocity, the architecture designed in this paper is characterized by much smaller overshoots and stationary errors.

关键词： Adaptive control Automatic landing Neural network PID Reference model

CFD-DEM simulation of Small-Scale Challenge Problem 1 with EMMS bubble-based structure-dependent drag coefficient

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Particuology 2021年第2期19卷 48-61页

作者： Musango lungu John Siame Lloyd Mukosha Multiphase Flow Research Group Chemical Engineering DepartmentSchool of Mines and Mineral SciencesCopperbelt UniversityKitwe 10101Zambia

In this study,the energy minimization multi-scale(EMMS)/Bubbling model is coupled with the computational fluid dynamics/discrete element method(CFD-DEM)model via a structure-dependent drag coefficient to simulate the National Energy Technology Laboratory(NETL)small-scale challenge problem using the open-source multiphase flow code *** numerical predictions are compared against particle velocity measurements obtained from high-speed particle image velocimetry(HSPIV)and differential pressure *** drag-reduction effect of the EMMS bubble-based drag coefficient is observed to significantly improve predictions of the horizontal particle velocity and granular temperature when compared to several other drag coefficients tested;however,the vertical particle velocity and pressure fluctuation characteristic predictions are *** drag-reduction effect is characterized by a reduction in the sizes of slugs or voids,as identified through spectral decomposition of the pressure ***,this study shows great promise in employing drag coefficients,developed via multi-scale approaches(such as the EMMS paradigm),in CFD-DEM models.

关键词： CFD-DEM Drag model EMMS/Bubbling model Fluidization Multi-scale

Application of Ordinary Kriging in Mapping Soil Organic Carbon in Zambia

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Pedosphere 2017年第2期27卷 338-343页

作者： Lydia Mumbi CHABALA Augustine MULOLWA Obed lungu Department of Soil Science University of Zambia School of Agricultural Sciences P.O. Box 32379 Lusaka (Zambia) Department of Geomatic Engineering University of Zambia School of Engineering/National Remote Sensing Center P.O. Box 32379 Lusaka (Zambia)

The quantification of the pattern and spatial distribution of soil organic carbon(SOC) is fundamental to understand many ecosystem processes. This study aimed to apply ordinary kriging(OK) to model the spatial distribution of SOC in a selected part of Zambia. A total of 100 soil samples were collected from the study area and analyzed for SOC by determining soil oxidizable carbon using the Walkley-Black method. An automated fitting procedure was followed when modeling the spatial structure of the SOC data with the exponential semivariogram. The results indicated that the short range spatial dependence of SOC was strong with a nugget close to zero. The spatial autocorrelation was high to medium with a nugget to sill ratio of 0.25. The root mean square error of the predictions was 0.64, which represented 58.18% of the mean observed data for SOC. It can be concluded that the generated map could serve as a proxy for SOC in the region where evidence of spatial structure and quantitative estimates of uncertainty are ***, the maps produced can be used as guides for various uses including optimization of soil sampling.

关键词：土壤有机碳普通克里格赞比亚应用制图生态系统过程空间分布空间结构

Assessment of the TFM in predicting the onset of turbulent fluidization

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Chinese Journal of Chemical Engineering 2019年第5期27卷 979-992页

作者： Musango lungu Haotong Wang Jingdai Wang Ronald Ngulube Yongrong Yang Fengqiu Chen John Siame State Key Laboratory of Chemical Engineering College of Chemical and Biological EngineeringZhejiang UniversityHangzhou 31002乙 China Chemical Engineering Department School of Mines and Mineral SciencesCopperbelt University10101 KitweZambia

Accurate prediction of the onset of turbulent fluidization still remains elusive owing to the dependence of the transition velocity on several factors including measurement methods and interpretation of results. In this work, numerical simulations using the two fluid model (TFM) are performed in an attempt to predict the regime change reported by Gopalan etal.(2016) in a small scale pseudo-2D gas-solid fluidized bed containing Geldart D particles. Various time and frequency domain analyses were applied on predicted absolute and differential pressure time series data to reveal the bed dynamics. Numerical predictions of the transition velocity, Uc are in reasonably good agreement with experimental results from the small scale challenge problem. The literature correlations completely fail to predict the transition velocity for the system considered in this work. This work thus provides a different approach for validating the CFD model against experimental measurements.

关键词： CFD Fluidization Regime identification Slugging Turbulent Wavelet analysis

Co-existence thresholds in the dynamics of the plant-herbivore interaction with Allee effect and harvest

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International Journal of Biomathematics 2018年第4期11卷 229-255页

作者： Manalebish Debalike Asfaw Semu Mitiku Kassa Edward M. lungu2 Department of Mathematics Addis Ababa University P.O. Box 1176 Addis Ababa Ethiopia Department of Mathematics and Statistical Sciences Botswana International University of Science andTechnology (BIUST) P/Bag 16 Palapye Botswana

In the interaction between plants and herbivores that live in the same ecosystem, understanding the conditions in which co-existence equilibrium occurs answers a major question in Ecology. In this interaction, plants serve as food for herbivores on the food chain. Then the livelihood of herbivores highly depends on the availability of food, in this case the availability of plants. Moreover, the abundance of the plant density alone does not guarantee the non-extinction of the herbivore population as they are assumed to reproduce sexually. With this motivation, in this paper a predator–prey mathematical model is reformulated such that the death rate of the herbivore population is dependent on the plant density and their emergence is also governed by the Allee effect. Using the mathematical theory of dynamical system, threshold conditions are obtained for the non-extinction of the herbivore population and a trapping region is obtained to ensure co-existence of the population. Moreover, it has been shown that the dynamics of the population is significantly sensitive to the feeding rate and the harvest rate of the herbivore population.

关键词：草食动物相互作用动力学收获率植物共存阈值生态系统

An experimental and theoretical investigation of a small,high aspect-ratio,free-piston,two-stroke engine

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Propulsion and Power Research 2020年第4期9卷 326-343页

作者： Chiluwata E.lungu Mael Disseau Daniel C.Stubbs Jechiel Jagoda David E.Scarborough General Electric Company GreenvilleSouth Carolina29615USA Georgia Institute of Technology AtlantaGeorgia30332USA Truett McConnel University ClevelandGeorgia30528USA Auburn University AuburnAlabama36849USA

This paper presents a design for a novel,palm sized,high-aspect-ratio *** simplify fabrication and keep the device unobtrusive,a design incorporating a two-cycle engine having a flat,rectangular piston with spring return was *** experimental engine based on this concept producing a significant amount of useful work was *** results were encouraging,this geometry raised many issues to be investigated and resolved,including the effects of piston sealing,scavenging,heat losses,and combustion *** to the complex interplay between these effects,experimental investigation was time consuming and simple models were found to be ***,a more complex theoretical model accounting for these effects was developed and used to evaluate the sensitivity of engine performance to each of these *** predictions of this model were used to develop recommendations for improving the experimentally developed engine.

关键词： Micro-combustion Power generation Free-piston engine Internal combustion engine Palm power

Independent and complementary bio-functional effects of CuO andGa_(2)O_(3) incorporated as therapeutic agents in silica-and phosphate-based bioactive glasses

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Journal of Materiomics 2022年第4期8卷 893-905页

作者： T.Tite A.C.Popa B.W.Stuart H.R.Fernandes I.M.Chirica G.A.lungu D.Macovei C.Bartha L.Albulescu C.Tanase S.Nita N.Rusu D.M.Grant J.M.F.Ferreira G.E.Stan National Institute of Materials Physics MagureleRO-077125Romania Advanced Materials Research Group Faculty of EngineeringUniversity of NottinghamNG72RDUK CICECOdAveiro Institute of Materials Department of Materials and Ceramics EngineeringUniversity of Aveiro3810-193AveiroPortugal “Victor Babes”National Institute of Research and Development in Pathology and Biomedical Sciences BucharestRO-050096Romania National Institute for Chemical Pharmaceutical Research and Development BucharestRO-031299Romania

The incorporation of therapeutic-capable ions into bioactive glasses(BGs),either based on silica(SBGs)or phosphate(PBGs),is currently envisaged as a proficient path for facilitating bone *** with this view,the single and complementary structural and bio-functional roles of CuO andGa_(2)O_(3)(in the 2e5 mol%range)were assessed,by deriving a series of SBG and PBG formulations startingfrom the parent glass systems,FastOs®BG e 38.5SiO2d36.1CaOd5.6P2O5d19.2MgOd0.6CaF2,and50.0P2O5d35.0CaOd10.0Na_(2)Od5.0 Fe2O_(3)(mol%),respectively,using the process of *** inter-linked physico-chemistry e biological response of BGs was assessed in search of bio-functional *** light was shed on the structural role e as network former or modifier e ofCu and Ga,immersed in SBG and PBG *** preliminary biological performance was surveyedin vitro by quantification of Cu and Ga ion release under homeostatic conditions,cytocompatibility assays(in fibroblast cell cultures)and antibacterial tests(against Staphylococcus aureus).The similar(Cu)anddissimilar(Ga)structural roles in the SBG and PBG vitreous networks governed their ***,Cuions were leached in similar concentrations(ranging from 10e35 ppm and 50e110 ppm at BG doses of 5and 50 mg/mL,respectively)for both type of BGs,while the release of Ga ions was 1e2 orders ofmagnitude lower in the case of SBGs(i.e.,0.2e6 ppm)compared to PBGs(i.e.,9e135 ppm).This wasattributed to the network modifier role of Cu in both types of BGs,and conversely,to the network former(SBGs)and network modifier(PBGs)roles of *** glasses were cytocompatible at a dose of 5 mg/mL,while at the same concentration the antimicrobial efficiency was found to be accentuated by the coupledrelease of Cu and Ga ions from *** collective assessment,the most prominent candidate material forthe further development of implant coatings and bone graft substitutes was delineated as the38.5SiO2d34.1CaOd5.6P2O5d16.2MgOd

关键词： Bioactive glass Copper Gallium Structure Ion release Antibacterial