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The energy management of a hybrid vehicle defines the vehicle power flow that minimizes fuel consumption and exhaust emissions. In a combined hybrid the complex architecture requires a multi-input control from the energy management. A classic optimal control obtained with dynamic programming shows that thanks to the high efficiency hybrid electric variable transmission, energy losses come mainly from the internal combustion engine. This paper therefore proposes a sub-optimal control based on the maximization of the engine efficiency that avoids multi-input control. This strategy achieves two aims: enhanced performances in terms of fuel economy and a reduction of computational time.

Compressed Natural Gas (CNG) engines have become a promising alternative to classical IC engines because of low pollutant and carbon dioxide emissions. This paper will first briefly summarize these advantages and then concentrate on the modeling and the control of CNG engines. In the modeling part, it will be shown which effects are similar to those observed in gasoline SI engines and what new sub-models are necessary. In the control part, the problem of sudden A/F ratio changes (for instance during the regeneration of NOx trap catalysts) will be considered. In order to avoid excessive NOx engine-out emission in these transients it is important to switch from lean to rich conditions within very few combustion cycles while keeping the engine torque constant (for comfort reasons). The paper presents a model of the most important phenomena associated with those transients and a feedforward control that meets the mentioned requirements.

This paper compares the fuel consumption of a lightweight passenger car for three different SI engine concepts, all with rated power of about 40 kW: a classical SI engine with moderate maximum speed, a low-displacement but high-speed engine that exploits the maximum allowed mean-piston speed and a low-displacement but highly supercharged engine with moderate maximum speed. All engines are simulated with a thermodynamic process simulator, the results of the supercharged version are validated with experiments. For each engine, a CVT and an automated gearbox is considered. Fuel consumption is estimated with a quasi-static driving cycle simulator which is based on engine fuel consumption maps and physical models of the vehicle with all its relevant subsystems. The simulations are performed for constant vehicle speed as well as for US and European driving cycles.

The paper presents experimental results of a fuel cell powered electric vehicle equipped with supercapacitors. This hybrid vehicle is part of an ongoing collaboration between the Paul Scherrer Institute (PSI, Switzerland), the Swiss Federal Institute of Technology (ETHZ), and several industrial partners. It is equipped with a fuel cell system with a nominal power of 48 kW and with supercapacitors that have a storage capacity of 360 Wh. Extensive tests have been performed on a dynamometer and on the road to investigate the operating ability. The highlights of these tests were the successful trial runs across the Simplon Pass in the Swiss Alps in January 2002. The fuel cell system consists of an array of six stacks with 125 cells each and an active area of 200 cm2. The stacks are electrically connected as two parallel strings of three stacks each in series in order to match the voltage requirement of the powertrain.

Pneumatic hybridization of internal combustion engines may prove to be a viable and cost-efficient alternative to electric hybridization. This paper evaluates the effects of pneumatic hybridization of various engine concepts using the criteria of fuel efficiency, driveability, emissions, and cost efficiency. The most promising engine concept is found to be the pneumatic hybridization combined with downsizing and supercharging spark-ignited engines. With this concept, a fuel consumption reduction of over 30% compared to a standard engine with the same rated power can be achieved. The poor driveability usually associated with heavily downsized and supercharged engines is completely overcome by injecting additional air during transients. The most important design issues for this new concept are discussed and several possible solutions are presented. Following these considerations, the first fully functional hybrid pneumatic engine was realized.