A state-of-the-art review on torque distribution strategies aimed at enhancing energy efficiency for fully electric vehicles with independently actuated drivetrains

© 2019, Levrotto and Bella. All rights reserved. Electric vehicles are the future of private passenger transportation. However, there are still several technological barriers that hinder the large scale adoption of electric vehicles. In particular, their limited autonomy motivates studies on methods for improving the energy efficiency of electric vehicles so as to make them more attractive to the market. This paper provides a concise review on the current state-of-the-art of torque distribution strategies aimed at enhancing energy efficiency for fully electric vehicles with independently actuated drivetrains (FEVIADs). Starting from the operating principles, which include the "control allocation" problem, the peculiarities of each proposed solution are illustrated. All the existing techniques are categorized based on a selection of parameters deemed relevant to provide a comprehensive overview and understanding of the topic. Finally, future concerns and research perspectives for FEVIAD are discussed

Power sources coordination through multivariable LPV/Hinf control with application to multi-source electric vehicles

International audienceIn this paper the problem of multi-source power sharing strategy within electric vehicles is considered. Three different kinds of power sources - fuel cell, battery and supercapacitor - compose the power supply system, where all sources are current-controlled and paralleled together with their associated DC-DC converters on a common DC-link. The DC-link voltage must be regulated regardless of load variations corresponding to the driving cycle. The proposed strategy is a robust control solution using a MIMO LPV/H-inf controller which provides the three current references with respect to source frequency characteristics. The selection of the weighting functions is guided by a genetic algorithm whose optimization criterion expresses the frequency separation requirements. A reduced-order version of the LPV/H-inf controller is also proposed to handle an embedded implementation with limited computational burden. The nonlinear multi-source system is simulated in MATLAB® / Simulink® using two different types of driving cycles: the driving cycle of IFSTTAR (Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux) and a constant load profile used in order to illustrate system steady-state behaviour. Simulation results show good performance in supplying the load at constant DC-link voltage according to user-configured frequency-separation power sharing strategy. When assessed against the classical-PI-based filtering strategy taken as base-line, the proposed strategy offers the possibility of integrating a variety of constraints into a systematic design procedure, whose result guarantees stability and performance robustness

Novel methods for estimating lithium-ion battery state of energy and maximum available energy

© 2016 Elsevier Ltd. The battery state of energy (SOE) allows a direct determination of the ratio between the remaining and maximum available energy of a battery, which is critical for energy optimization and management in energy storage systems. In this paper, the ambient temperature, battery discharge/charge current rate and cell aging level dependencies of battery maximum available energy and SOE are comprehensively analyzed. An explicit quantitative relationship between SOE and state of charge (SOC) for LiMn2O4 battery cells is proposed for SOE estimation, and a moving-window energy-integral technique is incorporated to estimate battery maximum available energy. Experimental results show that the proposed approaches can estimate battery maximum available energy and SOE with high precision. The robustness of the proposed approaches against various operation conditions and cell aging levels is systematically evaluated

Multiphysics Simulation and Model-based System Testing of Automotive E-Powertrains

Programa Oficial de Doutoramento en Enxeñaría Naval e Industrial . 5015V01[Abstract] Model-Based System Testing emerges as a new paradigm for the development cycle that is currently gaining momentum, especially in the automotive industry. This novel approach is focused on combining computer simulation and real experimentation to shift the bulk of problem detection and redesign tasks towards the early stages of the developments. Along these lines, Model-Based System Testing is aimed at decreasing the amount of resources invested in these tasks and enabling the early identification of design flaws and operation problems before a full-vehicle prototype is available. The use of Model-Based System Testing, however, requires to implement some critical technologies, three of which will be discussed in this thesis. The first task addressed in this thesis is the design of a multiplatform framework to assess the description and resolution of the equations of motion of virtual models used in simulation. This framework enables the efficiency evaluation of different modelling and solution methods and implementations. In Model-Based System Testing contexts virtual models interact with physical components, therefore it is mandatory to guarantee their real-time capabilities, regardless of the software or hardware implementations. Second, estimation techniques based on Kalman Filters are of interest in Model- Based System Testing applications to evaluate parameters, inputs or states of a virtual model of a given system. These procedures can be combined with the use of Digital Twins, virtual counterparts of real systems, with which they exchange information in a two-way communication. The available measurements from the sensors located at a physical system can be fused with the results obtained from the simulation of the virtual model. Thus, this avenue improves the knowledge of the magnitudes that cannot be measured directly by these sensors. In turn, the outcomes obtained from the simulation of the virtual model could serve to make decisions and apply corrective actions onto the physical system. Third, co-simulation techniques are necessary when a system is split into several subsystems that are coordinated through the exchange of a reduced set of variables at discrete points in time. This is the case with a majority of Model-Based System Testing applications, in which physical and virtual components are coupled through a discrete-time communication gateway. The resulting cyber-physical applications are essentially an example of real-time co-simulation, in which all the subsystems need to achieve real-time performance. Due to the presence of physical components, which cannot iterate over their integration steps, explicit schemes are often mandatory. These, however, introduce errors associated with the inherent delays of a discrete communication interface. These errors can render co-simulation results inaccurate and even unstable unless they are eliminated. This thesis will address this correction by means of an energy-based procedure that considers the power exchange between subsystems. This research work concludes with an example of a cyber-physical application, in which real components are interfaced to a virtual environment, which requires the application of all the MBST technologies addressed in this thesis.[Resumen] Los ensayos de sistemas basados en modelos emergen como un nuevo paradigma de desarrollo que actualmente está ganando popularidad, especialmente en la industria automotriz. Este nuevo enfoque se centra en combinar la simulación por ordenador con la experimentación para desplazar la mayor parte de la detección de problemas y rediseños hacia las fases tempranas del desarrollo. De esta forma, los ensayos de sistemas basados en modelos se centran en disminuir la cantidad de recursos invertidos en estas tareas y habilitar la identificación temprana de errores de diseño y problemas durante la operación, incluso antes de que los prototipos del vehículo completo estén disponibles. Sin embargo, el uso de esta estrategia requiere implementar algunas tecnologías críticas, tres de las cuales serán tratadas en esta tesis. La primera tarea abordada en esta tesis es el diseño de un entorno multiplataforma para evaluar la descripción y resolución de las ecuaciones de la dinámica de los modelos virtuales usados en las simulaciones. Este marco permite una evaluación eficiente de las diferentes formas de modelar los sistemas y de los métodos de resolución e implementación. En este contexto de ensayos basados en modelos, los sistemas virtuales interactúan con los componentes de los sistemas físicos, por lo tanto es necesario garantizar sus capacidades de ejecución en tiempo real, independientemente de la plataforma de software y hardware utilizada. En segundo lugar, las técnicas de estimación basadas en filtros de Kalman son de gran interés en las aplicaciones que usan ensayos basados en modelos para evaluar los parámetros, entradas o estados de los modelos virtuales de un sistema dado. Estos procedimientos se pueden combinar con el uso de gemelos digitales, homólogos virtuales de un sistema físico, con el cual mantienen un flujo bidireccional de intercambio de información. Las medidas disponibles procedentes de los sensores instalados en un sistema físico se pueden combinar con los resultados obtenidos de la simulación del sistema virtual. De este modo, este enfoque mejora el conocimiento de las magnitudes que no pueden ser medidas directamente por los sensores. A su vez, los resultados de la simulación de los sistemas de los modelos virtuales pueden servir para tomar decisiones y aplicar medidas correctivas al sistema real. En tercer lugar, las técnicas de co-simulación son necesarias cuando un sistema se divide en varios subsistemas, coordinados a través del intercambio de un reducido número de variables en momentos puntuales. Este es el caso de la mayor parte de las aplicaciones que siguen la estrategia de ensayos basados en modelos, en los cuales los componentes físicos y virtuales se acoplan mediante una comunicación en tiempo discreto. Como resultado las aplicaciones ciberfísicas son en esencia un ejemplo de co-simulación en tiempo real, en la que todos los subsistemas necesitan cumplir los requisitos de ejecución en tiempo real. Debido a la presencia de componentes físicos, que no pueden reiterar sus pasos de integración, el uso de esquemas explícitos es frecuentemente necesario. Sin embargo, estos esquemas introducen errores asociados con los retrasos propios de una interfaz de tiempo discreto. Estos errores pueden dar lugar a resultados erróneos e incluso inestabilizar la co-simulación, si no son eliminados. Esta tesis aborda la corrección de la co-simulación a través de métodos energéticos basados en la potencia intercambiada por los subsistemas. Este trabajo de investigación concluye con un ejemplo de aplicación ciberfísica, en la que se conectan componentes reales a una simulación por ordenador. Esta aplicación requiere la aplicación de las tecnologías de ensayos basados en modelos presentadas a lo largo de esta tesis.[Resumo] Os ensaios de sistemas baseados en modelos xorden como un novo paradigma de desenvolvemento que actualmente está gañando popularidade, especialmente na industria automotriz. Este novo enfoque céntrase en combinar a simulación por ordenador coa experimentación para desprazar a maior parte da detección de problemas e redeseños cara as fases iniciais do ciclo de produto. Deste xeito, os ensaios de sistemas baseados en modelos fundaméntanse en diminuír a cantidade de recursos investidos nestas tarefas e habilitar a identificación temperá de erros de deseño e problemas durante a operación, aínda se os prototipos do vehículo completo non están dispoñibeis. Porén, o uso desta estratexia require implementar algunhas tecnoloxías críicas, tres das cales serán tratadas nesta tese. A primeira tarefa tratada nesta tese é o deseño dun entorno multiplataforma para avaliar a descripción e resolución das ecuacións da dinámica dos modelos virtuais empregados nas simulacións. Este entorno permite unha avaluación eficiente dos diferentes xeitos de modelar os sistemas e dos métodos de resolución e implementación. Neste contexto de ensaios baseados en modelos, os sistemas virtuais interactúan cos compoñentes dos sistemas físicos, polo tanto é necesario garantir as súas capacidades de execución en tempo real, independentemente da plataforma de hardware e software escollida. En segundo lugar, as técnicas de estimación baseadas en filtros de Kalman son de grande interese nas aplicacións que usan ensaios baseados en modelos para avaliar os seus parámetros, entradas ou estados dos modelos virtuais dun certo sistema. Estes procedementos pódense combinar co uso de xemelgos dixitais, homólogos virtuais dun sistema físico, co cal manteñen un fluxo bidireccional de intercambio de información. As medidas dispoñíbeis procedentes dos sensores instalados nun sistema físico pódense combinar cos resultados obtidos da simulación do sistema virtual. Deste xeito, este enfoque mellora o coñecemento das magnitudes que non poden ser medidas directamente polos sensores. Á súa vez, os resultados da simulación dos sistemas dos modelos virtuais poden servir para tomar decisións e aplicar medidas correctivas ao sistema real. En terceiro lugar, as técnicas de co-simulación son necesarias cando un sistema é dividido en varios subsistemas, coordinados a través do intercambio dun reducido número de variables en momentos puntuais. Este é o caso da maior parte das aplicacións que seguen a estratexia de ensaios baseados en modelos, nos cales os compoñentes físicos e virtuais se acoplan mediante unha comunicación en tempo discreto. Como resultado as aplicacións ciberfísicas son esencialmente un exemplo de co-simulación en tempo real, na que tódolos subsistemas necesitan cumprir os requisitos de execución en tempo real. Debido á presenza de compoñentes físicos, que non poden reiterar os seus pasos de integración, o uso de esquemas explícitos é polo xeral necesario. Con todo, estes esquemas introducen erros asociados cos atrasos derivados dunha interface de tempo discreto. Estes erros poden provocar resultados incorrectos e incluso inestabilizar a co-simulación, de non seren eliminados. Esta tese aborda a corrección da co-simulación a través de métodos enerxéticos baseados na potencia intercambiada polos subsistemas. Este traballo conclúe cun exemplo de aplicación ciberfísica, na que os compoñentes reais son conectados a un entorno virtual. Isto require o emprego de tódalas tecnoloxías de ensaios baseadas en modelos presentadas ao longo desta tese

Real time adaptive efficient cold start strategy for proton exchange membrane fuel cells

Cold start of proton exchange membrane fuel cells (PEMFCs) at sub-zero temperatures is perceived as one of the obstacles in their commercialization way in automotive application. This paper proposes a novel internal-based adaptive strategy for the cold start of PEMFC to control its operating current in real time in a way to maximize the generated heat flux and electrical power in a short time span. In this respect, firstly, an online parameter identification method is integrated into a semi-empirical model to cope with the PEMFC performances drifts during cold start. Subsequently, an optimization algorithm is launched to find the best operating points from the updated model. Finally, the determined operating point, which is the current corresponding to the maximum power, is applied to PEMFC to achieve a rapid cold start. It should be noted that the utilization of adaptive filters has escaped the attention of previous PEMFC cold start studies. The ultimate results of the proposed strategy are experimentally validated and compared to the most commonly used cold start strategies based on Potentiostatic and Galvanostatic modes. The experimental outcomes of the comparative study indicate the striking superior performance of the proposed strategy in terms of heating time and energy requirement. © 2018 Elsevier Lt

Modelling and Co-simulation of hybrid vehicles: A thermal management perspective

Thermal management plays a vital role in the modern vehicle design and delivery. It enables the thermal analysis and optimisation of energy distribution to improve performance, increase efficiency and reduce emissions. Due to the complexity of the overall vehicle system, it is necessary to use a combination of simulation tools. Therefore, the co-simulation is at the centre of the design and analysis of electric, hybrid vehicles. For a holistic vehicle simulation to be realized, the simulation environment must support many physical domains. In this paper, a wide variety of system designs for modelling vehicle thermal performance are reviewed, providing an overview of necessary considerations for developing a cost-effective tool to evaluate fuel consumption and emissions across dynamic drive-cycles and under a range of weather conditions. The virtual models reviewed in this paper provide tools for component-level, system-level and control design, analysis, and optimisation. This paper concerns the latest techniques for an overall vehicle model development and software integration of multi-domain subsystems from a thermal management view and discusses the challenges presented for future studies

Multiple Heat Exchanger Cooling System for Automotive Applications – Design, Mathematical Modeling, and Experimental Observations

The design of the automotive cooling systems has slowly evolved from engine-driven mechanical to computer-controlled electro-mechanical components. With the addition of computer-controlled variable speed actuators, cooling system architectures have been updated to maximize performance and efficiency. By switching from one large radiator to multiple smaller radiators with individual flow control valves, the heat rejection requirements may be precisely adjusted. The combination of computer regulated thermal management system should reduce power consumption while satisfying temperature control objectives. This research focuses on developing and analyzing a multi-radiator system architecture for implementation in ground transportation applications. The premise is to use a single radiator during low thermal loads and activate the second radiator during high thermal loading scenarios. Ground vehicles frequently use different radiators for each component that needs cooling (e.g., engine blocks, electronics, and motors) since they have different optimal working temperatures. The use of numerous smaller heat exchangers adds more energy-management features and alternative routes for carrying on with operation in the event of a crucial subsystem failure. Moreover, despite cooling systems being designed for maximum thermal loads, most vehicles typically operate at a small fraction of their peak values. To study and examine the planned multi-heat exchanger cooling system concepts, various computer simulations and experimental tests were performed. A nonlinear state space model, featuring input and output heat flow paradigms, was developed using a multi-node resistance-capacitance thermal model. The heat removal rate from the radiator(s) was estimated using the -NTU method as downstream fluid temperatures were not required. The system performance was studied for two driving cycles proposed by the Environmental Protection Agency (EPA) – urban and highway driving schedules. The computer simulation was validated using the laboratory setup in the High Bay Area of Fluor Daniel Engineering Innovation Building. The configuration features computer controlled variable speed electric motor driven coolant pump and independent variable speed fans for each radiator to provide desired fluid flow rates. The pump and fan power consumptions are approximately 0.8-1.2 kW and 0.4-3.2 kW, which corresponds to coolant and air flow rates of 0.2-1.5 kg/s and 0.5-1.75 kg/s, respectively. Two servo motor-controlled gate valves limit the coolant outlet from each radiator. Various thermocouples and a magnetic flow sensor record test data in real time using a dSpace DS1103 data acquisition control system. Designing and analyzing a nonlinear control architecture for the suggested system was the last phase in the study process. A nonlinear controller equipped TMS should offer higher energy efficiency and overall system performance. Three controllers—sliding mode, stateflow, and classical—were designed and implemented in Matlab/Simulink and placed onto the dSpace hardware. The sliding mode controller is recommended for high performance applications since it offers steady temperature tracking, 5oC, an acceptable response time, 120 sec, but suffers from frequent changes in fan speed. The stateflow controller exhibited the fewest fan speed oscillations, the fastest response time, 88 sec, and the smallest temperature offset, 3oC, it is advised for use in common passenger vehicle applications. Both controllers need around six minutes to warm up. The traditional controller, meanwhile, had the quickest warmup, 600 sec, but the slowest response time, 215 sec. Nonlinear cooling systems are essential for maintaining component temperatures which will enable vehicle reliability, and maximize performance given the focus on hybrid and electric vehicles