Tuesday, June 19, 2012

Two-stage multi-scale search for sparse targets

Abstract: We consider the problem of energy constrained and noise-limited search for targets that are sparsely distributed over a large area. We propose a multi-scale search algorithm that significantly reduces the search time of the adaptive resource allocation policy (ARAP) introduced in [Bashan et all, 2008]. Similarly to ARAP, the proposed approach scans a Q-cell partition of the search area in two stages: first the entire domain is scanned and second a subset of the domain, suspected of containing targets, is re-scanned. The search strategy of the proposed algorithm is driven by maximization of a modified version of the previously introduced ARAP objective function, which is a surrogate for energy constrained target detection performance. We analyze the performance of the proposed multistage ARAP approach and show that it can reduce mean search time with respect to ARAP for equivalent energy constrained detection performance. To illustrate the potential gains of MARAP, we simulate a moving target indicator (MTI) radar system and show that M-ARAP achieves an estimation performance gain of 7 dB and a 85% reduction in scan time as compared to an exhaustive search. This comes within 1 dB of the previously introduced ARAP algorithm at a fraction of its required scan time.

Impact: This work provides a policy for mulit-scale search for sparse targets under total resource constraints, such as available scan time and/or computational resources. The proposed policy enhance previous work by considering the case where the number of measurements are constrained as well.

Journal: IEEE Transactions on Signal Processing, May 2011. DOI: 10.1109/TSP.2011.2112353. Full text available here.

Submitted by Gregory Newstadt, Graduate Student Research Assistant, Electrical Engineering and Computer Science, College of Engineering. newstage@umich.edu

Thursday, June 14, 2012

Distributed Supervisory Controller Design for Battery Swapping Modularity in Plug-In Hybrid Electric vehicles

Abstract: A distributed supervisory controller is proposed to achieve battery component swapping modularity (CSM) for a plug-in hybrid electric vehicle (PHEV). The CSM permits the designer to distribute a part of the supervisory controller to the battery module such that the PHEV can use a range of batteries while providing corresponding optimal fuel economy. A novel feedback-based controller for the charge sustaining mode is proposed to facilitate distributed controller design for battery CSM. The method based on sensitivity analysis of the control signals with respect to the battery hardware parameter is introduced to define the controller distribution architecture. The distributed controller gains are obtained by solving a bilevel optimization problem using the collaborative optimization and the augmented Lagrangian decomposition methods. The simulation results demonstrate that the proposed distributed controller can achieve battery CSM without compromising fuel economy compared to the centralized control case.

Impact: The battery module (including battery controller) can be swapped (e.g., upgraded or used to handle product variants) without having to redesign and retune the supervisory controller for the PHEV power management.

Journal: ASME Journal of Dynamic Systems, Measurement and Control, July 2012. DOI: 10.1115/1.4006214.

Submitted by A. Galip Ulsoy, the C D Mote, Jr Distinguished University Professor of Mechanical Engineering and Professor of Mechanical Engineering, College of Engineering. ulsoy@umich.edu

Automotive Control Systems

Summary: This engineering textbook is designed to introduce advanced control systems for vehicles, including advanced automotive concepts and the next generation of vehicles for ITS. For each automotive control problem considered, the authors emphasize the physics and underlying principles behind the control system concept and design. This is an exciting and rapidly developing field for which many articles and reports exist but no modern unifying text. An extensive list of references is provided at the end of each chapter for all the topics covered. It is currently the only textbook, including problems and examples, that that covers and integrates the topics of automotive powertrain control, vehicle control, and intelligent transportation systems. The emphasis is on fundamental concepts and methods for automotive control systems, rather than the rapidly changing specific technologies. Many of the text examples, as well as the end-of-chapter problems, require the use of MATLAB and/or SIMULINK.

Impact: It is currently the only textbook, including problems and examples, that that covers and integrates the topics of automotive powertrain control, vehicle control, and intelligent transportation systems.

Publisher: Cambridge University Press, June 2012. ISBN:9781107010116.

Submitted by A. Galip Ulsoy, the C D Mote, Jr Distinguished University Professor of Mechanical Engineering and Professor of Mechanical Engineering, College of Engineering. ulsoy@umich.edu

Wednesday, June 13, 2012

Large particles in modern diesel engine exhaust

Summary: During research on diesel engine EGR cooler fouling a test stand giving visual access to the building deposit layer has been developed. Initial experiments reveal the presence of large particles in the exhaust. While conventional wisdom is that diesel particulates typically have log-normal size distributions ranging approximately 10-200 nm, the tests reported here observe small numbers of particles with sizes on the order of tens of micron. Such particles are not generally reported in the literature because exhaust particle sizing instruments typically have inertial separators to remove particles larger than ~1 micron in order to avoid fouling of the nanoparticle measurement system.

In order to study these particles further, an exhaust sample was passed over a fiberglass filter, and the resulting filtered particles were analyzed. Samples were taken at the engine EGR passage, and also in the test stand tubing just before the visualization fixture. The resulting images indicate that the particles are not artifacts of the test system, but rather are present in engine exhaust.

MATLAB routines were developed to analyze the filter images taken on the microscope camera. Particles were identified, counted, and sized by the software.

It is not possible to take isokinetic samples and give quantitative measurement of the number and size distribution of the particles because the particles are large enough that inertial and gravitational effects will cause them to at least partially settle out of the flows. Nonetheless, the presence of particles tens of μm is documented.

Such particles are probably the result of in-cylinder and exhaust pipe deposits flaking. While these larger particles would be captured by the diesel particulate filter (DPF), they can affect intake and exhaust valve seating, EGR cooler fouling, EGR valve sealing, and other factors.

Impact: The existence of large particles in diesel exhaust is previously unreported, and can have effects on engine components.

Conference: Presented at the ASME 2012 Internal Combustion Engine Division Spring Technical Conference on May 6, 2012. ASME proceedings ICES2012-81232.

Submitted by John Hoard, Associate Research Scientist, Mechanical Engineering, College of Engineering. hoardjw@umich.edu

A Visualization Test Setup for Investigation of Water-Deposit Interaction in a Surrogate Rectangular Cooler Exposed to Diesel Exhaust Flow

Summary: Exhaust gas recirculation (EGR) coolers are commonly used in diesel engines to reduce the temperature of recirculated exhaust gases in order to reduce NOx emissions. The presence of a cool surface in the hot exhaust causes particulate soot deposition as well as hydrocarbon and water condensation. Fouling experienced through deposition of particulate matter and hydrocarbons results in degraded cooler effectiveness and increased pressure drop. In this study, a visualization test setup is designed and constructed so that the effect of water condensation on the deposit formation and growth at various coolant temperatures can be studied. A water-cooled surrogate rectangular channel is employed to represent the EGR cooler. One side of the channel is made of glass for visualization purposes. A medium duty diesel engine is used to generate the exhaust stream. An automated system controls all critical parameters including gas inlet temperature and pressure, coolant temperature, and the exhaust flow rate to correlate laminar, transition, and turbulent flow regimes in the channel. A digital microscope is also utilized to record the deposit formation and water-deposit interaction process. This study leads us towards hypothesis for prevention or mitigation of the deposit formation in EGR coolers.

Impact: Improved durability and function of heat exchangers in fouling conditions can lead to fuel economy improvement and emission reduction.

Conference: Presented at the Society of Automotive Engineers 2012 World Congress & Exhibition, April 16th, 2012. DOI: 10.4271/2012-01-0364.

Submitted by John Hoard, Associate Research Scientist, Mechanical Engineering, College of Engineering. hoardjw@umich.edu

Tuesday, June 12, 2012

Single Particle Characterization of Aβ Oligomers in Solution

Abstract: Determining the pathological role of amyloids in amyloid-associated diseases such as Alzheimer's disease will require a method for determining the dynamic distributions in size and shape of amyloid oligomers with high resolution. Here, we explored the potential of resistive-pulse sensing through lipid bilayer-coated nanopores to measure the size of individual amyloid-β oligomers directly in solution and without chemical modification. This method classified individual amyloid-β aggregates as spherical oligomers, protofibrils, or mature fibers and made it possible to account for the large heterogeneity of amyloid-β aggregate sizes. The approach revealed the distribution of protofibrillar lengths as well as the average cross-sectional area of protofibrils and fibers.

Impact: We show that nanopore-based resistive pulse recordings made it possible to characterize the size and shape of unlabeled aggregates of Alzheimer's disease-relevant amyloids in solution. The particular strength of nanopore sensing lies in its ability to characterize a large number of individual aggregates. This capability for single particle analysis is required to characterize Aβ aggregates with a wide-ranging, dynamic heterogeneity in size and shape as well as to correlate cytotoxicity and pathogenic mechanisms with aggregate sizes and shapes.

Journal: Paper accepted to ACS Nano, DOI: 10.1021/nn300542q

Submitted by Michael Mayer, Associate Professor of Biomedical Engineering and Associate Professor of Chemical Engineering, College of Engineering.

Hello, world

Welcome to Raw Engineering. If you’re looking to stay on top of what Michigan Engineering researchers are up to, you’ve come to the right place. Here you will soon be able to read abstracts and summaries of recent and upcoming papers from U-M engineers. These posts will be written by members of the research teams, so you can get your news straight from the source.