Engine Downsizing and Electric Hybridization Under Consideration of Cost and Drivability

Automotive manufacturers of hybrid electric vehicles are confronted with the multi-objective non-trivial optimization problem of engine downsizing and electric hybridization under consideration of cost and drivability. Solutions to this sizing problem are typically reached by heuristic design methodologies. However, a design approach formalized in an optimization theoretical setting is necessary in order to obtain globally optimal solutions. In this paper, we present a framework for optimal sizing of hybrid electric drivetrain components. This framework is cast within standard optimization theory. Moreover, it is flexible in order to easily include any number of objectives, such as minimization of fuel consumption, cost of hybridization, emission levels and (or) maximization of acceleration performance. Based on this framework, we demonstrate a number of techniques and tools to analyze, accept, improve, or reject the proposed solutions to the optimal sizing problem.