George J. Delagrammatikas

Target cascading in vehicle redesign: a class VI truck study

The analytical target cascading process is applied to the redesign of a U.S. class VI truck. Necessary simulation and analysis models for predicting vehicle dynamics, powertrain, and suspension behaviour are developed. Vehicle design targets that include improved fuel economy, ride quality, driveability, and performance metrics are translated into system design specifications, and a consistent final design is obtained. Trade-offs between conflicting targets are identified. The study illustrates how the analytical target cascading process can reduce vehicle design cycle time while ensuring physical prototype matching, and how costly design iterations late in the development process can be avoided.

Optimization Approach to Hybrid Electric Propulsion System Design

Abstract Environmentally friendly ground vehicles with range and performance capabilities surpassing those of conventional vehicles require a careful balance among competing goals for fuel efficiency, performance, and emissions. The research objective here is to integrate hybrid electric vehicle simulations with high-fidelity engine modules, to increase the accuracy of predictions, and to allow design studies in the concept evaluation stage. This paper describes a methodology for integrating vehicle and engine simulations. The feed-forward model of the engine is modified to allow its linking with the vehicle model, and an engine component scaling routine is added to facilitate system sizing studies. A design optimization framework is then used to find the best overall engine size, battery pack, and motor combination for minimum fuel consumption within proposed US government performance criteria.

Chronic Intermittent Hypoxia Induces NMDA Receptor-Dependent Plasticity and Suppresses Nitric Oxide Signaling in the Mouse Hypothalamic Paraventricular Nucleus

Chronic intermittent hypoxia (CIH) is a concomitant of sleep apnea that produces a slowly developing chemosensory-dependent blood pressure elevation ascribed in part to NMDA receptor-dependent plasticity and reduced nitric oxide (NO) signaling in the carotid body. The hypothalamic paraventricular nucleus (PVN) is responsive to hypoxic stress and also contains neurons that express NMDA receptors and neuronal nitric oxide synthase (nNOS). We tested the hypothesis that extended (35 d) CIH results in a decrease in the surface/synaptic availability of the essential NMDA NR1 subunit in nNOS-containing neurons and NMDA-induced NO production in the PVN of mice. As compared with controls, the 35 d CIH-exposed mice showed a significant increase in blood pressure and an increased density of NR1 immunogold particles located in the cytoplasm of nNOS-containing dendrites. Neither of these between-group differences was seen after 14 d, even though there was already a reduction in the NR1 plasmalemmal density at this time point. Patch-clamp recording of PVN neurons in slices showed a significant reduction in NMDA currents after either 14 or 35 d exposure to CIH compared with sham controls. In contrast, NO production, as measured by the NO-sensitive fluorescent dye 4-amino-5-methylamino-2′,7′-difluorofluorescein, was suppressed only in the 35 d CIH group. We conclude that CIH produces a reduction in the surface/synaptic targeting of NR1 in nNOS neurons and decreases NMDA receptor-mediated currents in the PVN before the emergence of hypertension, the development of which may be enabled by suppression of NO signaling in this brain region.

Simulation-based optimal design of heavy trucks by model-based decomposition: an extensive analytical target cascading case study

We present the findings of an extensive case study for the decomposed, simulation-based, optimal design of an advanced technology heavy truck by means of analytical target cascading. The use of a series hybrid-electric propulsion system, in-hub motors, and variable height suspensions is considered with the intention of improving both commercial and military design attributes according to a dual-use philosophy. Emphasis is given to fuel economy, ride, and mobility characteristics. The latter are predicted by appropriately developed analytical and simulation models. This article builds on previous work and focuses on recent efforts to refine the applied methodologies and draw final conclusions.

Analytical Target Cascading for the Design of an Advanced Technology Heavy Truck

Analytical target cascading (ATC) is a methodology that can be used during the early development phase of large and complex systems for propagating desirable overall product targets to appropriate individual specifications for the various subsystems and components. The ATC process is applied to the design of an advanced technology heavy truck. A series hybrid-electric propulsion system, in-hub motors, and variable height suspensions are introduced with the intention of improving both commercial and military design attributes according to a dual-use design philosophy. Emphasis is given to fuel economy, ride, and mobility characteristics. The latter are predicted by analytical and simulation models developed appropriately. This article is an extension to previous work: the engine is now included at the bottom level, several battery types are considered to study their effect on fuel economy, and a more demanding driving schedule is used to assess regenerative braking benefits and ride quality. Results are presented for target values associated with a 100% improvement on fuel economy while maintaining performance attributes relative to existing designs.

Optimization of Advanced Engine Controls for Conventional Vehicles: A Driving Cycle Perspective

A controls optimization methodology for advanced diesel engines, as they are utilized in a specific driving cycle, is addressed in this work. The technique illustrated here accounts for realistic engine use regimes encountered during the FTP driving schedule and finds the maximum foreseeable fuel economy improvement, with the introduction of advanced technologies, to a baseline engine design. Outputs from the optimization procedure are analyzed from a numerical standpoint, yielding insights into the general topology of the engine’s design domain. Control variable histories through the specified driving cycle are determined and discussed with specific regard to the thermodynamic mechanisms producing the associated fuel economy improvements. Guidelines for the practical design of engine components, along with the assumptions made for these studies, are detailed. These techniques are directly applicable to other types of automotive internal combustion engines, vehicles, and driving patterns.© 2002 ASME