Electrothermal battery pack model for automotive application: Design and validation

Thermal modeling of the battery is an important way to understand how the design and operating variables affect the thermal response during its operation. This paper presents a method for modeling the electrical and thermal behavior of a battery pack, starting from the characterization of the single Lithium-ion battery cell up to extend its validity to module and pack level. The model takes into account both the reversible entropic heat generation and the irreversible resistive heat to predict the temperature of the battery. A coupled CFD and thermal analysis on an elementary module is proposed and experimentally tested to validate the results obtained from the proposed model. Furthermore, the experimental test will verify the effectiveness of air cooling

Temperature-Dependent Thévenin Model of a Li-Ion Battery for Automotive Management and Control

This paper focuses on the analysis of Li-ion battery behavior at different temperatures through the Thévenin electrical circuit model. First, evaluations for both steady-state and dynamic battery applications are provided, then an overview of the different battery models to describe their dynamic behavior is analyzed. The focus is dedicated to the double polarization Thévenin-based equivalent circuit model since it represents an optimal trade-off between accuracy and computation effort, which justifies its implementation in a Battery Management System (BMS) for automotive real-time monitoring and control. The model is composed of a voltage source, one series resistor and two series RC blocks. The Hybrid Pulse Power Characterization test (HPPC) is performed inside a climatic chamber to extract the electrical parameters of the model and their dependency from both temperature and State Of Charge (SOC). The load-current effects on the battery performance are not considered for the simplicity and lightness of the presented model. The presented procedure has broader validity and is mostly independent of cell format and Li-ion chemistry, despite a specific cylindrical battery cell is chosen for the study. The results of the test are suitable for the future implementation of a proper algorithm for SOC and State Of Health SOH estimations. Moreover, they provide an effective electrical and thermal characterization of the cell to evaluate the heat generation rate inside the cell

Dynamic Electro-Thermal Li-ion Battery Model for Control Algorithms

This paper presents a fast and effective approach to evaluate the heat generation of a Li-ion battery system. The thermal characterization of Li-ion batteries is a relevant topic for the correct monitoring of the battery pack. In particular, a reduced-order model, that estimates the thermal dynamics of a Li-ion battery cell, is reported. The proposed approach relies on the definition of a boundary-value problem for heat conduction, in the form of a linear partial differential equation with the integration of Equivalent Circuit Model. The model is based on the double polarization Thévenin equivalent circuit model since it represents an optimal trade-off between accuracy and computation effort, which justifies its implementation in a Battery Management System (BMS) for automotive real-time monitoring and control. The resulting model predicts the temperature dynamics at the external surface in relation with the rate of the internal heat generation. In this paper, the model is applied to estimate the temperature of a cylindrical cell during a discharging transient and it uses electrical data acquired from experimental tests and is validated Computational fluid dynamics simulation. The results of the test are suitable for the future implementation of a proper algorithm for State of Charge SOC and State of Health SOH estimations

Non-linear kalman filters for battery state of charge estimation and control

In this paper, two different non-linear Kalman Filters for lithium-ion battery state of charge estimation are presented and compared. Nowadays, lithium-ion batteries are extensively used for hybrid and electric vehicles; in such applications, cells are assembled in module and pack to achieve high performance. At this scope, a Battery Management Systems BMS is required to control each cell and improve the battery pack performance, safety, reliability, and lifecycle. One of the major tasks a BMS must fulfill is an accurate online estimation of the State Of Charge (SOC) of the battery pack. In this paper, the Extended Kalman Filter and Sigma Points Kalman filter are developed and compared. A battery equivalent circuit model has been chosen to have a good compromise between complexity and accuracy and model parameters have been identified from Hybrid Pulse Power Characterization (HPPC) tests carried out at different temperatures and current rates to obtain a model valid for a wide range of operating conditions. The SOC estimation strategies are developed starting from the experimental results and it is validated through different driving cycling simulations. The results show that the Sigma Points Kalman filter produces a better estimate of SOC with respect to the Extended Kalman Filter, due to its better capability to deal with system non-linearities, with comparable computational complexity

Composite Control Arm Design: A Comprehensive Workflow

This paper presents a complete overview of the computational design of an advanced suspension control arm constructed of composite material for light weighting purposes. The proposed methodology presented in detail is split into 3 phases. Phase 1 or Vehicle Performance Simulation, in which basic modelling and a sensibility study is performed to better understand the advantages of unsprung mass reduction (compared to sprung mass reduction) with respect to the vehicle's vertical dynamics. It followed by the development and utilization of a multibody approach to evaluate the full-vehicle response to different dynamic maneuvers, such as harsh road imperfections, sine sweep steering, and double lane change tests. The impact of the improved suspension control arm is highlighted in detail, and the loads to which it is subjected are computed to serve as inputs for the successive phases. Phase 2 or Design and Calculation Phase, where a closer look is given to the structural side of the component, understanding the specific behavior of composite materials and performing modelling of the control arm, followed by fine tuning with Finite Element Method optimization techniques. This phase consists of a topology optimization, followed by composite topography free size, size, and shuffle optimizations to arrive upon the ideal part-layup, and guarantee the desired mechanical characteristics of the component. Lastly, Phase 3 or the Production Preparation closes the design process by generating the production processes, steps, constraints, and tooling for the correct realization of the innovative control arm in a real-world application. The tools presented in this paper were created to allow the design to be completed rapidly, thus defining a blueprint for a full workflow, from engineering request to product delivery, which can be applied to different vehicles and customer requests, representing an essential step forward to the consolidation of the use of composite materials for structural suspension components

City Car Drag Reduction by means of Flow Control Devices

In the past few decades, the automotive industry saw the development of several environment-friendly technologies, as high efficiency engines, lightweight materials, and low-rolling-resistance tires. Car body styling, together with aerodynamics, play an important role in resolving environmental issues by reducing drag force, which results in high fuel efficiency and lower energy requirements. The main objective of this study is the reduction of the aerodynamic resistance of a city-car prototype by means of flow control devices (air blow and air relief) located into the wheel arches. This work starts from the wind tunnel experimental tests of the baseline version of the XAM 2.0 vehicle, then, dedicated ducts are implemented into the model in order to reduce the turbulence of the front wheel well and the air-flow defection at the end of the sides of the car body. A CFD analysis is carried out in order to assess the effects of the introduced modifications: car shape is varied by CAS, for every modification CFD calculations are performed. A correlation between wind tunnel and CFD results is carried out validating the drag optimization, demonstrating the predictive capabilities of CFD analysis and a record-breaking drag coefficient

Validation of a numerical-experimental methodology for structural health monitoring on automotive components

In the recent years, the materials composing the traditional of aircrafts are being progressively replaced with lower density materials, as the Reinforced Plastics. The same trend has been highlighted in the Automotive field to assess the reduction of fuel consumption and CO2 emission. In order to achieve an optimization of maintenance a variety of on-board systems has been applied for on-line SHM based on piezoelectric transducers earned a particularly high interest for continuous monitoring on metallic and composite structures. The application of this system in automotive could enhance passenger safety, through the monitoring of the vehicle composite material structure health status. In this paper, six mathematical models for evaluating the electrical response of piezoelectric sensors have been implemented, with the aim of selecting the most effective model for damage identification. Experimental tests were carried out on three types of simpler specimens of different geometries made of different materials (steel, aluminum and carbon fiber). A correlation study has been carried on in order to support the positioning of sensors. The proposed numerical-experimental methodology is an essential foundation for the introduction of monitoring systems based on piezoelectric transducers in the Automotive sector

Feasibility study on piezoelectric actuated automotive morphing wing

Active aerodynamics is a promising technology to improve vehicle performance and efficiency, but so far in the automotive field the actuation methods suffer with several drawbacks that jeopardize its functioning and broad implementation. Morphing wings represent a technology already studied for aerospace applications that could help overcoming some of those issues. This paper proposes a piezoelectric transducer actuation for a composite material automotive wing and seeks to validate it through virtual models and physical tests. Experimental validation with a 3D-printed simplified wing profile confirms the feasibility of the technology and helps determining the best position for the piezo actuator. Furthermore, a FEM model is presented, where the piezo effect is simulated through a thermal analogy. An optimization of the composite stacking sequence is performed to maximize the trailing edge displacements, and its results are compared with the deflection caused by aerodynamic loads observed in the wing. The displacement of the trailing edge is in the order of tenths of a millimeter, even though further investigations are necessary to improve overall impact of the solution the preliminary results are promising