Guest Editorial

Hybrid electric vehicles (HEV´s) are beginning to demonstrate their capabilities to match these design criteria while still allowing emission-reduced (or even emission-free) vehicle operation and a considerably improved fuel economy during many driving patterns. The PNGV demonstrator vehicles, the Toyota Prius, the Honda Insight, and many more demonstrators from European automakers are clear signs of this trend. The fact that HEV??s can meet various requirements makes them viable options to substitute conventional vehicles in the short- and medium-term perspectives. It must, however, be remarked that the design of hybrid vehicles, much like that of conventional vehicles, is characterized by tradeoffs between fuel economy and emissions objectives and performance and driveability objectives. Hybrid vehicle analysis and design is concerned with the storage and conversion of energy in (or among) three domains - chemical, mechanical, and electrical. Some of the conversions are bidirectional (e.g., motor??generator action), and some are not (e.g., fuel chemical-to-mechanical energy conversion via a combustion process). Each domain is characterized by energy storage devices (e.g., fuels, batteries, supercapacitors, and flywheels), while energy conversion devices form links between energy domains. The papers included in this special section illustrate a cross section of the engineering problems and solutions associated with the design and analysis of hybrid vehicles. The papers contained in this special section represent two important areas: analysis and simulation of HEV´s and the design of special hybrid electric drive subsystems.