Ahmed Ketfi-Cherif

Implementation of an Energy Management Strategy for Hybrid Electric Vehicles Including Drivability Constraints

The energy management strategy (EMS) of a hybrid electric vehicle is a supervisory control meant to steer power flows among the different energy sources of the powertrain. The EMS is designed for the purpose of reaching the maximum potential of a given powertrain architecture. Fuel consumption is not the only criterion to be considered for evaluating the global performance of an EMS, since the EMS also impacts other features such as drivability, through engine starts/stops and gear shifts. This paper proposes a general approach to include drivability constraints in the EMS of powertrains provided with discrete automated transmissions. As a first step, determinist dynamic programming is used to compute the optimal solution of the resulting optimization problem. This optimal solution is then used to assess the performance of the proposed online strategy, which is based on the equivalent consumption minimization strategy. Finally, simulation results are completed by a discussion of experimental results, as the proposed online strategy has been implemented in a prototype vehicle designed at Renault and tested on a dynamometric bench.

Energy Management of a High Efficiency Hybrid Electric Automatic Transmission

The energy management of a hybrid vehicle defines the vehicle power flow that minimizes fuel consumption and exhaust emissions. In a combined hybrid the complex architecture requires a multi-input control from the energy management. A classic optimal control obtained with dynamic programming shows that thanks to the high efficiency hybrid electric variable transmission, energy losses come mainly from the internal combustion engine. This paper therefore proposes a sub-optimal control based on the maximization of the engine efficiency that avoids multi-input control. This strategy achieves two aims: enhanced performances in terms of fuel economy and a reduction of computational time.

Powertrain Control and Evaluation of Hybrid Powersplit Systems

Abstract This paper focuses on a method to control an hybrid power-split transmission. The main issue is the multivariable aspect of these systems. From a practical point of view, the control needs to track simultaneously a wheel torque, an engine speed and an electric power target. The approach proposed here is based on a two level control strategy. The first one is a so-called energy management which aims at calculating an optimal set of targets minimizing fuel consumption and deciding to stop or start the engine with a sub-optimal but reasonable method. Given these targets, the second control level aims at controlling the transmission, taking into account inertia in a multivariable way in order to achieve some good tracking and decoupling objectives. Each driving mode has to be considered and corresponds to a specific control requirement. To give more realism to previous papers on this topic, we focus here on the fuel cut-off and start modes which are described in details. To this purpose, an observer based state feedback in described. In the last section, we present simulations results for two power-split transmissions on two different driving cycles. The achieved fuel consumption and the control behavior are presented.