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For simulation and analysis of vehicles there is a need to have a means of generating drive cycles which have properties similar to real world driving. A method is presented which uses measured vehicle speed from a number of vehicles to generate a Markov chain model. This Markov chain model is capable of generating drive cycles which match the statistics of the original data set. This Markov model is then used in an iterative fashion to generate drive cycles which match constraints imposed by the user. These constraints could include factors such number of stops, total distance, average speed, or maximum speed. In this paper, systematic analysis was done for a PHEV fleet which consists of 9 PHEVs that were instrumented using data loggers for a period of approximately two years. Statistical analysis using principal component analysis and a clustering approach was carried out for the real world velocity profiles. After dividing the real velocity profiles into segments, they were clustered into several different clusters based on statistical data. This data set is also used to generate the Markov chain model technique described above which is the central development of this work. The work of this paper is a part of a larger project in which a mass simulation of a neighborhood of PHEVs will be conducted based on statistical representations of key factors such as vehicle usage patterns, vehicle characteristics, and market penetration of PHEVs. This approach can be used as critical input of the large scale simulation model to generate random velocity profiles of various driving patterns

Homogeneous Charge Compression Ignition is a promising concept for achieving low emissions at partload operations. This technique can be successfully applied to traditional Direct Injection Diesel engines with low extra costs and no modification to the DI system by performing the mixture formation in the intake manifold.The present work describes the development of a controloriented model for the study of the combustion process in a HCCI Diesel engine with external mixture formation. The model is based on a first-law thermodynamic analysis of in-cylinder processes in order to identify the influence of the main control parameters on HCCI auto-ignition. The combustion process is modeled through the definition of a gross heat release rate, avoiding a detailed description of the chemical reactions that could increase the complexity and the computation time.The model is then validated against experimental data obtained on a Diesel engine equipped with an external fuel atomizer. The satisfactory agreement obtained and the low calibration effort make the model a useful tool for the development of applications related to HCCI engine control and diagnostics.

Homogeneous charge compression ignition (HCCI) is a promising concept for internal combustion engines that can considerably decrease NOx and soot emissions in part-load operations without penalizing fuel consumption. The HCCI combustion can be implemented in direct injection diesel engines without major modifications by introducing a specialized fuel injector in the intake port. This decouples the homogeneous mixture formation from the traditional in-cylinder injection, thus providing two fueling systems that can be used to optimize exhaust emissions and fuel consumption over the engine operating range. However, understanding and controlling the complex mechanisms and interactions driving the HCCI combustion process is still a difficult task. For this reason, it is essential to identify the most important control parameters and understand their influence on the auto-ignition process. The current work analyzes HCCI combustion with external mixture formation through experimental investigation and the definition of a control-oriented model. An extensive testing activity was performed on a passenger car diesel engine equipped with an external fuel atomizer to operate in HCCI mode. This provided an understanding of the process as well as experimental data to identify a mean value model of the system and its parameters. The model includes a thermodynamic combustion calculation that estimates the heat release, cylinder pressure, and the relevant variables for combustion control. The tool developed was then validated and used for analyzing the system behavior in steady state conditions. Finally, a description of the HCCI system behavior in transient operations is presented.

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