Woong-Chul Choi

In situ calibration for wide-angle, three-dimensional stereoscopic image analysis

Accurate measurement of three-dimensional object coordinates from stereoscopic images is an essential element in various applications that require three-dimensional position information. Conventionally, optical ray tracing has been the measurement method of choice. However, it requires accurate knowledge of geometrical and optical parameters, such as the image distance, camera locations relative to the object field, and size, shape, and refractive index of intervening elements, such as apparatus windows. On the other hand, all these parameters need not be known if an optical transformation method based on an in situ calibration experiment is used. Furthermore, the use of in situ calibration not only increases the effective accuracy of the measured three-dimensional object coordinates but also reduces significantly the computational time compared with conventional optical ray tracing. The computational efficiency of the technique used is essential, especially when the application requires multiple determinations of a large number of three-dimensional coordinates, such as is the case with three-dimensional particle-tracking velocimetry. The basic concept and formulation of an optical transformation method based on an in situ calibration experiment is introduced. The technique is first demonstrated with synthetic data, then case studies with actual in situ calibration data are discussed.

Experimental Investigation to Study Convective Mixing, Spatial Uniformity, and Cycle-to-Cycle Variation During the Intake Stroke in an IC Engine

The work described in this paper focuses on experiments to quantify the initial fuel mixing and gross fuel distribution in the cylinder during the intake stroke and its relationship to the large-scale convective flow field. The experiments were carried out in a water analog engine simulation rig, and, hence, limited to the intake stroke. The same engine head configuration was used for the three-dimensional PTV flow field and the PLIF fuel concentration measurements. High-speed CCD cameras were used to record the time evolution of the dye convection and mixing with a 1/4 deg of crank angle resolution (and were also used for the three-dimensional PTV measurements). The captured sequences of images were digitally processed to correct for background light non-uniformity and other spurious effects. The results are finely resolved evolution of the dye concentration maps in the center tumble plane. The three-dimensional PTV measurements show that the flow is characterized by a strong tumble, as well as pairs of cross-tumble, counter-rotating eddies. The results clearly show the advection of a fuel-rich zone along the wall opposite to the intake valves and later along the piston crown. It also shows that strong out-of-plane motions further contribute to the cross-stream mixing to result in a relatively uniform concentration at BDC, albeit slightly stratified by the lean fluid entering the cylinder later in the intake stroke. In addition to obtaining phase-averaged concentration maps at various crank angles throughout the intake stroke, the same data set is processed for a large number of cycle to extract spatial statistics of the cycle-to-cycle variability and spatial non-uniformity of the concentration maps. The combination of the three-dimensional PTV and PLIF measurements provides a very detailed understanding of the advective mixing properties of the intake-generated flow field.

Sizing Study and Validation of a Hybridized Fuel Cell NEV With Bi-Directional Grid Inter-Connect for Sustainable Local Transportation

Due to sharply increasing oil price, tremendous efforts are being made to reduce the dependencies on the petroleum based fuels in the field of automotive power trains. As one of the promising alternatives, fuel cell hybrid system has been studied for many different vehicle types from SUV to low speed vehicle. To establish systematic ways to achieve the optimized system configuration, in this paper, we introduce a methodology which combines energy analysis over typical drive cycles with a parametric sizing study for the various powertrain components as well as supervisory energy management parameters. For a practical and demonstrative implementation of the suggested methodology with a limited resource available at hand, a Neighborhood Electric Vehicle (NEV) for urban transportation is considered for a detailed analysis, design and optimization. Two major supervisory control strategies, namely, charge-sustaining and charge-depleting are carefully investigated to illustrate the versatility of our proposed methodology. Our study shows that the systems could be modeled and optimized either in a charge sustaining case or in a charge depleting case (plug-in hybrid electric vehicle) to meet vehicle purposes and usages, respectively. Not only because of the usage of the FC power system as a range extender for an EV, but also the possibility of using the plug-in configuration with renewable energy generation systems, as a personal eco-system, the proposed plug-in FC-NEV may be a solution for a local urban transportation system in this demanding era of sustainable mobility.Copyright

DESIGN AND VALIDATION OF LIGHT-DUTY FC HYBRID VEHICLE FOR URBAN TRANSPORTATION

Abstract In the context of rapidly diminishing petroleum supplies, significant changes in both technology and classes of vehicle will need to emerge. It is conceivable to fragment the passenger vehicle market into 3 broad classes: general purpose vehicles as defined today, commuter vehicles with limited range for daily commute and urban-only vehicles restricted to transportation in downtown areas, etc. In this paper, we focus on this last class of vehicles and present a methodology used in the design and optimisation of a light duty FC hybrid Neighbourhood Electric Vehicle. By systematically characterizing and analysing the driving patterns for the vehicle, extensive simulations were used to optimise the powertrain topology and the component sizing. Further optimisation was performed to derive control strategies and control parameters to minimize the fuel consumption, yielding equivalent fuel consumption of the order of 100 MPGGE under urban driving conditions in a 2 passenger vehicle. The simulations and analysis were verified on a laboratory test bench and the complete vehicle architecture was implemented with off-the-shelf technology into a vehicle which has the potential of being commercializable. While this vehicle is only a prototype, this demonstration project shows the great potential for such special purpose vehicles for clean and efficient urban transportation.