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A control strategy has been designed for a city bus equipped with a pneumatic hybrid propulsion system. The control system design is based on the precise management of energy flows during both energy storage and regeneration. Energy recovered from the braking process is stored in the form of compressed air that is redeployed for engine start and to supplement the engine air supply during vehicle acceleration. Operation modes are changed dynamically and the energy distribution is controlled to realize three principal functions: Stop-Start, Boost and Regenerative Braking. A forward facing simulation model facilitates an analysis of the vehicle dynamic performance, engine transient response, fuel economy and energy usage.

The pursuit of fuel economy is forcing technology change across the range of control and engine management technologies. Improved thermal management has been addressed in order to promote fast warm-up, improved exhaust gas after-treatment performance, and lower variance in combustion through a consistent and high cylinder head temperature. Temperature management of exhaust gas is of increasing interest because of the need to maintain efficiency in after-treatment devices. More effective temperature management places requirements on heat exchange systems, and offers the potential for bottoming and heat recovery cycles that use energy transferred from the exhaust stream. Turbo-compounding is already established in heavy duty engines, where a reduction in exhaust gas temperature is the consequence of an additional stage of expansion through an exhaust turbine. A new project in electric turbo-compounding offers flexibility in the control of energy extracted from the exhaust stream[1].

Many automotive manufacturers have announced their intention to launch fuel cell powered cars in the next few years. This has led to large research budgets aimed at new or emerging technologies. The emergence of a new automotive power and drive system allows a new beginning in designing the components of these systems with environmental impact in mind. That is, the whole car, from the ground up, can be built from “design for the environment” principles with an appreciation of “well to wheels” impact of its fuel. Using this approach, vehicles can be designed for minimum resource and energy use during manufacture and for low cost, low impact disassembly, leading not only to improved environmental performance but also to reduced manufacturing costs.