Yann Guezennec

A-ECMS: An Adaptive Algorithm for Hybrid Electric Vehicle Energy Management

Hybrid Electric Vehicles (HEV) improvements in fuel economy and emissions strongly depend on the energy management strategy. In this paper a new control strategy called Adaptive Equivalent Consumption Minimization Strategy (A-ECMS) is presented. This real-time energy management for HEV is obtained adding to the ECMS framework an on-the-fly algorithm for the estimation of the equivalence factor according to the driving conditions. The main idea is to periodically refresh the control parameter according to the current road load, so that the battery State of Charge (SOC) is maintained within the boundaries and the fuel consumption is minimized. The results obtained with A-ECMS show that the fuel economy that can be achieved is only slightly sub-optimal and the operations are charge-sustaining.

Algorithms for fully automated three-dimensional particle tracking velocimetry

A three-dimensional Particle Tracking Velocimetry (3-D PTV) technique has been developed to provide time-resolved, three-dimensional velocity field measurements throughout a finite volume. This technique offers many advantages for fundamental research in turbulence and applied research in areas such as mixing and combustion. The data acquired in 3-D PTV is a time sequence of stereo images of flow tracer particles suspended in the fluid. In this paper, the implementation of the technique is discussed in detail, as well as the results of an extensive statistical investigation of the performance of the algorithms. The technique has been optimized to allow fully automatic processing of long sequences of image pairs in a computationally efficient manner, hereby providing a viable, practical tool for the study of complex flows.

Proton Exchange Membrane Fuel Cell System Model for Automotive Vehicle Simulation and Control

This paper describes a proton exchange membrane (PEM) fuel cell system model for automotive applications that includes an air compressor, cooling system, and other auxiliaries. The fuel cell system model has been integrated into a vehicle performance simulator that determines fuel economy and allows consideration of control strategies. Significant fuel cell system efficiency improvements may be possible through control of the air compressor and other auxiliaries. Fuel cell system efficiency results are presented for two limiting air compressor cases: ideal control and no control. Extension of the present analysis to hybrid configurations consisting of a fuel cell system and battery is currently under study.

Stochastic estimation of coherent structures in turbulent boundary layers

The stochastic estimation provides a means of estimating conditional averages from unconditional statistics, namely, the two‐point correlation tensor. This technique is applied to three‐dimensional data obtained in a fully turbulent boundary layer. The results of linear and nonlinear estimates are compared to the corresponding conditional averages and the agreement is found to be excellent, with little improvement for nonlinear estimates. Extensions of the technique to space‐time estimates of one‐ and two‐point conditional averages are also presented, the latter providing a means to examine structures associated with a given length scale.

An application of the stochastic estimation to the jet mixing layer

The linear stochastic estimation is a powerful technique that provides a means of estimating conditional eddies given unconditional two‐point correlation data. This procedure was used to reconstruct estimates of multipoint conditional averages of the dominant structures in the jet mixing layer of Glauser and George (Proceedings of the Sixth Symposium on Turbulent Shear Flows, Toulouse, France, 1987). The pseudodynamic evolution of these conditional eddies was systematically compared to the instantaneous velocity fields and the results were quantified in terms of the percentage of the energy captured by the multipoint stochastic estimates. It was found that the single‐point estimates do not yield adequate representations of the instantaneous velocity field, but that two reference points located on opposite sides of the shear layer yield realistic estimates, with little gained by adding more reference points.

On the shape and dynamics of wall structures in turbulent channel flow

Turbulence‐producing events in turbulent channel flow were found to be predominantly associated with asymmetric vortical structures rather than pairs of counter‐rotating structures. An asymmetry‐preserving averaging scheme was devised, allowing a picture of the ‘‘average’’ structure that more closely resembles the instantaneous one to be obtained. In addition, these structures were found to persist for long distances with little change while convecting downstream.

A new life estimation method for lithium-ion batteries in plug-in hybrid electric vehicles applications

This paper presents a new approach to life estimation for lithium-ion batteries used in plug-in hybrid electric vehicles (PHEVs) applications. A new framework for battery life estimation is developed which investigates the effects of two primary factors of battery life reduction in PHEVs applications, namely, depth of discharge (DOD) and temperature (Tbatt), under typical driving conditions, driving habits, and average commute time of typical user over a year. This framework, whose development is built upon a weighted ampere-hour throughput model of the battery, is based on the novel concept of severity factor map which captures and quantifies the battery damage caused by different operating conditions. The proposed methodology can be a suitable tool to estimate battery life in terms of miles/year on-board of the vehicle.

Supervisory control of fuel cell vehicles and its link to overall system efficiency and low-level control requirements

In this paper, we address the benefits of hybridization of fuel cell vehicles. These benefits are not only in efficiency gains but also result in a significant lessening of the dynamic control requirements for automotive fuel cell systems.

On the Control of Engine Start/Stop Dynamics in a Hybrid Electric Vehicle

The starter/alternator technology is considered an easily realizable hybrid electric vehicle (HEV) configuration to achieve significant fuel economy without compromising consumer acceptability. Several examples can be found in production or near-production vehicles, with implementation based on a spark ignition (SI) engine coupled with either a belted starter/alternator (BSA) or an integrated starter/alternator (ISA). One of the many challenges in successfully developing a starter/alternator HEV is to achieve engine start and stop operations with minimum passenger discomfort. This requires control of the electric motor to start and stop the engine quickly and smoothly, without compromising the vehicle noise, vibration, and harshness signature. The issue becomes more critical in the case of diesel hybrids, as the peak compression torque is much larger than in SI engines. This paper documents the results of a research activity focused on the control of the start and stop dynamics of a HEV with a belted starter/alternator. The work was conducted on a production 1.9 l common-rail diesel engine coupled to a 10.6 kW permanent magnet motor. The system is part of a series/parallel HEV powertrain, designed to fit a midsize prototype sport utility vehicle. A preliminary experimental investigation was done to assess the feasibility of the concept and to partially characterize the system. This facilitated the design of a control-oriented nonlinear model of the system dynamics and its validation on the complete HEV hardware. Model-based control techniques were then applied to design a controller for the belted starter/alternator, ensuring quick and smooth engine start operations. The final control design has been implemented on the vehicle. The research outcomes demonstrated that the BSA is effective in starting the diesel engine quickly and with very limited vibration and noise.

Mean Value Modeling and Analysis of HCCI Diesel Engines With External Mixture Formation

Homogeneous charge compression ignition (HCCI) is a promising concept for internal combustion engines that can considerably decrease NO x and soot emissions in part-load operations without penalizing fuel consumption. The HCCI combustion can be implemented in direct injection diesel engines without major modifications by introducing a specialized fuel injector in the intake port. This decouples the homogeneous mixture formation from the traditional in-cylinder injection, thus providing two fueling systems that can be used to optimize exhaust emissions and fuel consumption over the engine operating range. However, understanding and controlling the complex mechanisms and interactions driving the HCCI combustion process is still a difficult task. For this reason, it is essential to identify the most important control parameters and understand their influence on the auto-ignition process. The current work analyzes HCCI combustion with external mixture formation through experimental investigation and the definition of a control-oriented model. An extensive testing activity was performed on a passenger car diesel engine equipped with an external fuel atomizer to operate in HCCI mode. This provided an understanding of the process as well as experimental data to identify a mean value model of the system and its parameters. The model includes a thermodynamic combustion calculation that estimates the heat release, cylinder pressure, and the relevant variables for combustion control. The tool developed was then validated and used for analyzing the system behavior in steady state conditions. Finally, a description of the HCCI system behavior in transient operations is presented.