Rochdi Trigui

Influence of control strategies on battery/supercapacitor hybrid Energy Storage Systems for traction applications

The energy storage is key issue for traction applications like Electric Vehicles (EVs) or Hybrid Electric Vehicles (HEVs). Indeed, it needs a higher power and energy density, a weak bulk and size, a long lifetime and a low cost. A hybrid Energy Storage System (ESS) using batteries and supercapacitors, seems to be a good device to answer to these constraints. The objective of the paper is to study the influence of control strategies for this hybrid ESS. Indeed, according to the used strategy, this association can be more and less interesting compared to an ESS only composed of batteries. Three control strategies are proposed.

Specifications and Design of a PM Electric Variable Transmission for Toyota Prius II

This paper focuses on an analysis of technical requirements for the design of a permanent-magnet-type electric variable transmission (PM-EVT), which is a novel series-parallel hybrid electric vehicle (HEV) powertrain concept. Similar to the planetary gear train used in Toyota Prius II, the EVT also realizes the power-split function. However, it is implemented in an electromagnetic way rather than in a mechanical way, as is the case for Prius II with a planetary gear. In this paper, a procedure to define the technical requirements of an EVT is presented. Since Toyota Prius II is a well-known series-parallel HEV, this vehicle is chosen as a reference. The engine, battery, and other necessary components are kept as input data. A dynamic simulation was performed to take into account different driving cycles. Then, based on an analysis of the simulation results (torque, speed, and power) the technical requirements of the PM-EVT are defined. Finally, the PM-EVT machine is designed. The PM-EVT design results are presented and validated using the finite-element method (FEM).

Switched Causal Modeling of Transmission With Clutch in Hybrid Electric Vehicles

Certain difficulties arise when attempting to model a clutch in a power train transmission due to its nonlinear behavior. Two different states have to be taken into account-the first being when the clutch is locked and the second being when the clutch is slipping. In this paper, a clutch model is developed using the energetic macroscopic representation, which is, in turn, used in the modeling of complete hybrid electric vehicles (HEVs). Two different models are used, and a specific condition defining the commutation between both models with respect to the physical energy flow is proposed. A Petri net is employed to activate one of the models, depending on the clutch state (locked or slipping). This model allows us to implement without difficulty a simulation of the clutch with a relatively short computation time.

Vehicle trajectory optimization for application in ECO-driving

To reduce fuel consumption in the transportation sector research focuses mainly on the development of more efficient drive train technologies and alternative drive train designs. Another and immidiately applicable way found to reduce fuel consumption in road vehicles is to change vehicle operation such that system efficiency is maximized. The concept of Eco-driving refers to the change of driver behavior in a fuel saving way or more generally in an energy saving way. In this paper system efficiency of a vehicle is optimized using a dynamic programming optimization approach. Given a drive cycle a so called ‘eco-drive cycle’ is identified in which a vehicle performs the same distance with the same stops in equivalent time, while consuming less fuel.

PHIL Implementation of Energy Management Optimization for a Parallel HEV on a Predefined Route

Real-time energy management of hybrid electric vehicles (HEVs) is a key point for performing effective fuel economy optimization. Offline methods have been developed for energy management optimization when the drive cycle is known. Online real-time methods can provide good results but can only ensure suboptimal management. In this paper, it is assumed that information about the route is available in advance. Using this knowledge, global optimization methods can be used in real-time control to approach optimal fuel consumption while keeping the state of charge (Soc) of the batteries at a desired level. Such a method is presented in this paper. The developed strategy is implemented in a real-time experiment using the power-hardware-in-the-loop (PHIL) principle. The measured fuel consumption and the obtained battery Soc trajectory demonstrate good performance of the proposed control.

Different energy management strategies of Hybrid Energy Storage System (HESS) using batteries and supercapacitors for vehicular applications

The energy storage is a key issue for traction applications like Electric Vehicles (EVs) or Hybrid Electric Vehicles (HEVs). Indeed, it needs a higher power and energy density, a right size, a long lifetime and a low cost. A Hybrid Energy Storage System (HESS) using batteries and supercapacitors seems to be an appropriate device to fulfill these constraints. The objective of the paper is to propose different energy management strategies of HESS using batteries and supercapacitors. Four elaborated control strategies are proposed. Different strategies are compared on different criteria: electric consumption, sizing, and the expected lifetime of the batteries.

Efficient Allocation of Electric Vehicles Charging Stations: Optimization Model and Application to a Dense Urban Network

The deployment of Electric Vehicles (EVs) needs an optimized and cost-effective implementation of charging stations. As a decision support tool for network design, we define a methodology to allocate charging stations in a real network. This study uses trip OD matrix information from household travel survey coupled with a dynamic vehicle model to evaluate EVs consumption based on realistic trips (urban drive cycles). These trips are computed based on routing tools and supplied with elevation information. This enables an accurate characterization of energy needs in the Lyon Metropolitan Area. All these parameters are used as inputs of an integer linear optimization program for the location of charging stations. The methodology is based on an adaption of the classic fixed charge location model with a p-dispersion constraint. The results indicate that this methodology can help the future implementation of charging stations at an urban scale.

Improvement of an EVT-Based HEV Using Dynamic Programming

Automotive engineers and researchers have proposed different topologies for series-parallel hybrid electric vehicles (SP-HEVs). The Toyota Hybrid System (THS) is the best known SP-HEV-based vehicle, but alternative solutions, such as electric variable transmission (EVT), have been also proposed. An efficient comparison between these different solutions is a key point to estimate the added value of each topology. This paper presents the application of optimal control to two series-parallel hybrid architectures for efficiency assessment purposes. The dynamic programming method is applied to the THS and to a virtual hybrid vehicle with an EVT. The way to take into account the supplementary degree of freedom provided by the decoupling of the wheels and the engine in both topologies is presented. The optimal fuel consumption is then compared on different driving cycles and brings out an overconsumption of the EVT topology. Then, a parametric study shows that inserting an appropriate gear ratio on the internal-combustion-engine (ICE) shaft can improve the EVT efficiency that becomes close to the THS efficiency.

Global modeling of different vehicles using Energetic Macroscopic Representation

A hybrid electric vehicle is a combination of two power sources: one unidirectional power source based on an internal combustion engine (ICE), and the other bidirectional based on batteries or electric energy storage, plus electric machines (EM). Different ways of combination lead to different vehicle architectures. But these hybrid vehicles have the same basically energy flow paths. So from this point of view, one global energetic modeling using Energetic macroscopic representation (EMR) which can be applicable to ICE vehicles, a battery powered electric vehicles, series hybrid vehicles, parallel hybrid Vehicles and series-parallel hybrid vehicles has been established. This causal modeling focuses on the system function not only on the structure of system and presents a global energetic view.

Model simulation, validation and case study of the 2004 THS of Toyota Prius

For hybrid vehicles, it is difficult to obtain realistic component models and actual interaction between subsystems without carrying out experiments. INRETS has performed a coupled approach associating simulation using its in house VEHLIB software together with experimental validation. This paper highlights the evaluation and modelling of the Toyota Hybrid Systems (THS) used in the 2004 Prius vehicle. First, the ICE, battery, boost converter, and strategy evaluation and validation process to obtain a useful model of the vehicle are examined. Then examples of application are presented concerning energy flow in the vehicle and engine operation compared to a conventional car.