Torque Control Strategy for a Parallel-Hybrid Vehicle using Fuzzy Logic

As urban air pollution regulations become more stringent, parallel-hybrid electric vehicles (HEVs) attract more attention as substitutes for diesel-powered transit buses [l]-{4], one of the most important concerns for a parallel HEV serving as a shuttle in an urban area is keeping the battery charge balanced. This extends battery life and provides easy maintenance. If an excessive battery discharge results after service, the external recharge process (time consuming and annoying) at a service station is unavoidable. On the other hand, the fuel efficiency and emission characteristics of parallel HEVs degrade when their batteries are overcharged. Thus, the challenge is to develop a driving strategy that can maintain the battery charge without sacrificing the driving performance of the vehicle and emission characteristics of parallel HEVs.