Karim Bencherif

A Reduced Fuel Cell Stack Model for Control and Fault Diagnosis

This paper proposes a reduced fuel cell stack model for control and fault diagnosis which was validated with experimental data. Firstly, the electro-chemical phenomena are modeled based on a mechanism of gas adsorption/desorption on catalysts at the anode and at the cathode of the stack, including activation, diffusion, and carbon monoxide poisoning. The electrical voltage of a stack cell is then modeled by the difference between the two electrode potentials. A simplified thermal model of the fuel cell stack is also developed in order to take into account heat generation from reactions, heat transfers, and evaporation/condensation of water. Finally, the efficiency ratio is computed as a model output. It is used to evaluate the efficiency changes of the entire system, providing an important indicator for fault detection.

Diesel Particulate Filter Thermal Management Using Model-Based Design

Diesel Particulate Filters (DPF) are now considered as efficient solutions to reduce Diesel PM emissions. Concerned by environment, Renault will equip all serial production Diesel vehicles with this technology. The main issue for these devices is the periodical regeneration necessary to eliminate the accumulated soot. The challenging enhancement of the regeneration event can be achieved with a better regeneration temperature control. For this purpose, a controller based on a physical model is proposed to manage the DPF temperature during active regeneration. This paper describes the methodology which has been followed to design this controller. In a first step, a reduced physical model has been developed and validated with experimental data. In a second step, two model-based controllers have been studied: a robust LPV (Linear Parameter Varying) and a gain scheduling PID..Special attention has been paid to the simplification as far as possible of the controller tuning process. Thus, the calibration parameters are only dependent upon some physical parameters and performance requirements of the closed-loop control: bandwidth, maximum overshoot. Performance robustness has been assessed in simulation. The whole modeling, controller design and validation, as well as robustness analysis have been performed using Matlab/Simulink®. Finally, the strategy has been validated on a vehicle using rapid prototyping tools.

Model based mass soot observer of diesel particle filter

Abstract Diesel Particulate Filters (DPF) has now been proven as an efficient solution in order to reduce Diesel PM emissions. Concerned by environment, Renault will equip all serial production Diesel vehicles with this technology. Main issue of such devices is the mandatory periodical regeneration in order to eliminate their soot content. The particulate filter (DPF) is used to store the soot emitted by the combustion engine. When the mass of particles in the filter reaches a certain limit mass, it is regenerated thanks to a temperature rise (Over 600°C). In this paper, we develop a model that describes the impact of the amount of soot in the filter on the Diesel engine performance. This model is used to determine the optimal amount of soot on which the regeneration of the particulate filter shall start. Then we propose a physical model that describes the pressure drop of particulate filter according to the mass of accumulated soot and inlet DFP temperature and flow conditions. Thus, we improve a literature model so that it takes on account the passive regeneration of the filter. Finally, we design an extended kalman filter using the combination of the simplified model and a pressure drop measurement. All the experimental validations are made thanks to different configurations: engine dynamometer, chassis dynamometer and vehicles.

Time-varying MPC-based energy management for HEV including engine stop & start

In this paper, the energy management of hybrid electric vehicles is considered and two problems are addressed: torque split and engine stop-start policies. Model predictive control potential is proven especially for the decision to stop the engine at the proper moment and also to anticipate engine restart. A piecewise linear polynomial with respect to torque is used to approximate the fuel consumption and it will be shown that its partition can be exploited to implicitly consider engine stop decision. The strategy is applied to a dual-clutch transmission hybrid architecture which was simulated on a high-fidelity vehicle model.

Mathematical Modeling and Control of a Reformer Stage for a Fuel Cell Vehicle

Abstract In this paper, we present the development of a reduced model for the control of CO concentration at the reformer outlet. In a first step, mathematical models of reformers (PROX) are detailed, a one space dimensional model, accounting for chemical and thermal effects is presented. The partial differential equation of the model is reduced to an ordinary differential equation using an orthogonal collocation method. Finally, controllers and observers are designed and their performances are illustrated by simulation.

Water and Heat Conservation Modelling for a Reformate Supplied Fuel Cell System

Fuel cell systems are intended to generate electric power. When Proton Exchange Membrane fuel cells are used, they also generate water and waste heat from air and hydrogen or from a gas rich in hydrogen. This paper proposes models for the water and heat balance of a reformate supplied fuel cell. Models are presented for the fuel cell thermal balance, the cooling circuit and the water balance. The models are reduced for control purposes: for thermal management of the fuel cell, and to maintain a positive water balance.

Analytical Reduced Model of Autothermal Reforming Process for the Control

Abstract The subjects discussed in this paper are motivated by problems arising in the computation of chemical equilibrium for an autothermal reforming process applied to a fuel cell. The composition of a chemical system at chemical equilibrium has been computationally determined by solving certain systems of simultaneous equations. We wish, in this paper, to present the development of a reduced model available for each fuel (methane, butane, gasoline...) and satisfying the different reforming modes, namely partial oxidation and steam reforming. There are two common ways to express the chemical equilibrium. One is based on equilibrium constants, while the other one is minimization of the free energy. The Equilibrium State at specified temperature and pressure is determined by minimizing the Gibbs free energy and is subject to the constraints imposed by conservation of atoms (mass balance). It is possible to have a reduced model summarized in a second order polynomial equation. This model can predict the chemical equilibrium composition and the temperature at the outlet of the reformer. Some parameters of reformer can be used as a key for the temperature control.