Targets, Constraints and Rules for Hybrid Management in a Series Hybrid Bus Intended for Commercial Introduction

Most research on hybrid management for hybrid electric vehicles generally does not match the demands of industry and customers. Proposed methods normally have a simplified view of optimisation targets and are besides this also based on advanced but unrealistic optimisation methods. Crucial commercial and technical aspects as well as driving forces for decision-makers and customers are disregarded when the focus is solely on improving fuel economy and tailpipe emissions with advanced control and optimisation techniques. The present work aims to define a framework for a hybrid management strategy that is commercially realistic due to the fact that both customer demands on vehicle performance as well as industrial prerequisites and limitations in the control system and the hybrid powertrain are taken into account. The proposed strategy is defined as a set of rules for the hybrid management control system. A series hybrid city bus intended for commercial introduction with supercapacitors as energy storage is used as an example, but the conclusions apply also to other powertrain designs. The presented rule-based strategy is also used in a test fleet of series hybrid diesel-ethanol buses which will be in operation in Stockholm from the autumn 2008.