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Technical Paper

A New Approach of Generating Travel Demands for Smart Transportation Systems Modeling

The transportation sector is facing three revolutions: shared mobility, electrification, and autonomous driving. To inform decision making and guide smart transportation system development at the city-level, it is critical to model and evaluate how travelers will behave in these systems. Two key components in such models are (1) individual travel demands with high spatial and temporal resolutions, and (2) travelers’ sociodemographic information and trip purposes. These components impact one’s acceptance of autonomous vehicles, adoption of electric vehicles, and participation in shared mobility. Existing methods of travel demand generation either lack travelers’ demographics and trip purposes, or only generate trips at a zonal level. Higher resolution demand and sociodemographic data can enable analysis of trips’ shareability for car sharing and ride pooling and evaluation of electric vehicles’ charging needs.
Journal Article

A Numerical Investigation of Ignition of Ultra-Lean Premixed H2/Air Mixtures by Pre-Chamber Supersonic Hot Jet

Gas engines often utilize a small-volume pre-chamber in which fuel is injected at near stoichiometric condition to produce a hot turbulent jet which then ignites the lean mixture in the main chamber. Hot jet ignition has several advantages over traditional spark ignition, e.g., more reliable ignition of extra-lean mixtures and more surface area for ignition resulting in faster burning and improved combustion burn time. Our previous experimental results show that supersonic jets could extend the lean flammability limit of fuel/air mixtures in the main chamber in comparison to subsonic jets. The present paper investigated the characteristics of supersonic hot jets generated by combustion of stoichiometric H2/air in a pre-chamber to understand the ignition mechanism of ultra-lean mixtures by supersonic hot jets.
Technical Paper

An Automated State Model Generation Algorithm for Simulation/Analysis of Power Systems with Power Electronic Components

In this paper, a recently-developed algorithmic method of deriving the state equations of power systems containing power electronic components is described. Therein the system is described by the pertinent branch parameters and the circuit topology; however, unlike circuit-based algorithms, the difference equations are not implemented at the branch level. Instead, the composite system state equations are established. A demonstration of the computer implementation of this algorithm to model a variable-speed, constant-frequency aircraft generation system is described. Because of the large number of states and complexity of the system, particular attention is placed on the development of a model structure which provides optimal simulation efficiency.
Technical Paper

Analysis and Simulation of a UAV Power System

Models for the components of a long-duration UAV power system are set forth. The models include the solar array, solar array power converter, fuel cell and electrolyzer system and corresponding power converter, and propulsion load. Based on these models, a power management control is derived, which when coupled with the component models, are used to simulate power system performance during start-up, through a day-night cycle, and through a solar eclipse.
Journal Article

Assessment of Large-Eddy Simulations of Turbulent Round Jets Using Low-Order Numerical Schemes

The basic idea behind large-eddy simulation (LES) is to accurately resolve the large energy-containing scales and to use subgrid-scale (SGS) models for the smaller scales. The accuracy of LES can be significantly impacted by the numerical discretization schemes and the choice of the SGS model. This work investigates the accuracy of low-order LES codes in the simulation of a turbulent round jet which is representative of fuel jets in engines. The turbulent jet studied is isothermal with a Reynolds number of 6800. It is simulated using Converge, which is second-order accurate in space and first-order in time, and FLEDS, developed at Purdue University, which is sixth-order accurate in space and fourth-order in time. The high-order code requires the resolution of acoustic time-scales and hence is approximately 10 times more expensive than the low-order code.
Technical Paper

Average Value Modeling of Finite Inertia Power Systems with Harmonic Distortion

Typically, average-value models of power system components neglect harmonic information. Herein, a systematic method of including harmonic information in average-value models based on the theory of multiple reference frames is set forth. Computer simulation results show that when there is significant harmonic distortion of the ac distribution bus the models presented herein are more accurate than traditional average-value models. Furthermore, much of the computational advantage of average-value techniques over detailed modeling techniques is retained.
Technical Paper

Balloon Launched UAV with Nested Wing for Near Space Applications

There has always been, from the very first UAV, a need for providing cost-effective methods of deploying unmanned aircraft systems at high altitudes. Missions for UAVs at high altitudes are used to conduct atmospheric research, perform global mapping missions, collect remote sensing data, and establish long range communications networks. The team of Gevers Aircraft, Technology Management Group, and Purdue University have designed an innovative balloon launched UAV for these near space applications. A UAV (Payload Return Vehicle) with a nested morphing wing was designed in order to meet the challenges of high altitude flight, and long range and endurance without the need for descent rate control with rockets or a feathering mode.
Technical Paper

Bayesian Optimization of Active Materials for Lithium-Ion Batteries

The design of better active materials for lithium-ion batteries (LIBs) is crucial to satisfy the increasing demand of high performance batteries for portable electronics and electric vehicles. Currently, the development of new active materials is driven by physical experimentation and the designer’s intuition and expertise. During the development process, the designer interprets the experimental data to decide the next composition of the active material to be tested. After several trial-and-error iterations of data analysis and testing, promising active materials are discovered but after long development times (months or even years) and the evaluation of a large number of experiments. Bayesian global optimization (BGO) is an appealing alternative for the design of active materials for LIBs. BGO is a gradient-free optimization methodology to solve design problems that involve expensive black-box functions. An example of a black-box function is the prediction of the cycle life of LIBs.
Technical Paper

Case Study of an Electric-Hydraulic Hybrid Propulsion System for a Heavy Duty Electric Vehicle

In order to improve efficiency and increase the operation of electric vehicles, assistive energy regeneration systems can be used. A hydraulic energy recovery system is modeled to be used as a regenerative system for supplementing energy storage for a pure electric articulated passenger bus. In this study a pump/motor machine is modeled to transform kinetic energy into hydraulic energy during braking, to move the hydraulic fluid from the low pressure reservoir to the hydraulic accumulator. The simulation of the proposed system was used to estimate battery savings. It was found that on average, approximately 39% of the battery charge can be saved when using a real bus driving cycle.
Technical Paper

Computer Modeling and Simulation of a Tracked Log Skidder with Different Grapple Configurations

A track-type grapple log skidder was dynamically modeled to allow machine modification by computer to determine the effects of these modifications on the operation of the machine in the forest. The model consisted of an undercarriage, power train, log/drag force, and logging equipment (arch and grapple). This skidder had three types of logging attachments: winch, swinging boom (grapple), and single-function arch (grapple). Each was modeled and simulated under various conditions. The dynamic model of the skidder can be used to analyze its drawbar pull capability and lateral stability with various log weights and soil types on steep slopes. Validation of this model is needed later.
Technical Paper

Concepts of Human Factors Engineering

This paper discusses the necessity for designing farm tractors which have logical, rather than arbitrary, safety features. The paper is directed primarily to those who buy and use industrial equipment and urges this group to exercise their influence on tractor design by purchasing only those vehicles which meet recommended standards for safety and construction.
Technical Paper

Derivation of the Three-Dimensional Installation Ratio for Dual A-Arm Suspensions

Conventional suspension analysis of three-dimensional suspensions typically use two-dimensional analyses. This is done by projecting suspension components onto two-dimensional planes and then performing a two-dimensional analysis in each of these orthogonal planes or neglecting motions in one of the planes entirely. This requires multiple iterations because changes in one plane require a checking of their effects on motion in the other orthogonal planes. In doing so, much of the insight and accuracy gained from a three-dimensional analysis can be lost. A three-dimensional kinematic analysis approach is presented and applied to a dual A-Arm suspension system. All motions are considered instantaneously about a screw axis instead of a point as used by the usual two-dimensional modeling approach. The model predicts deflections of suspension components in response to the three-dimensional forces present at the contact patch.
Technical Paper

Design Optimization of Sandwich Composite Armors for Blast Mitigation Using Bayesian Optimization with Single and Multi-Fidelity Data

The most common and lethal weapons against military vehicles are the improvised explosive devices (IEDs). In an explosion, critical cabin’s penetrations and high accelerations can cause serious injuries and death of military personnel. This investigation uses single and multi-fidelity Bayesian optimization (BO) to design sandwich composite armors for blast mitigation. BO is an efficient methodology to solve optimization problems that involve black-box functions. The black-box function of this work is the finite element (FE) simulation of the armor subjected to blast. The main two components of BO are the surrogate model of the black-box function and the acquisition function that guides the optimization. In this investigation, the surrogate models are Gaussian Process (GP) regression models and the acquisition function is the multi-objective expected improvement (MEI) function. Information from low and high fidelity FE models is used to train the GP surrogates.
Journal Article

Designing for Large-Displacement Stability in Aircraft Power Systems

Due to the instabilities that may occur in power systems with regulated loads such as those used in military aircraft, ships, and terrestrial vehicles, many analysis techniques and design methodologies have been developed to ensure stable operation for expected operating conditions. However, many of these techniques are difficult to apply to complex systems and do not guarantee large-displacement stability following major disturbances such as faults, regenerative operation, large pulsed loads, and/or the loss of generating capacity. In this paper, a design paradigm is set forth guaranteeing large-displacement stability of a power system containing a significant penetration of regulated (constant-power) loads for any value of load power up to and including the steady-state rating of the source. Initial investigations are performed using an idealized model of a dc-source to determine the minimum requirements that ensure large-displacement stability.
Technical Paper

Development of a Torque-Based Control Strategy for a Mode-Switching Hydraulic Hybrid Passenger Vehicle

An increase in the number of vehicles per capita coupled with stricter emission regulations have made the development of newer and better hybrid vehicle architectures indispensable. Although electric hybrids have more visibility and are now commercially available, hydraulic hybrids, with their higher power densities and cheaper components, have been rigorously explored as the alternative. Several architectures have been proposed and implemented for both on and off highway applications. The most commonly used architecture is the series hybrid, which requires an energy conversion from the primary source (engine) to the secondary domain. From he re, the power flows either into the secondary source (high-pressure accumulator) or to the wheels depending upon the state of charge of the accumulator. A mode-switching hydraulic hybrid, which is a combination of a hydrostatic transmission and a series hybrid, was recently developed in the author’s research group.
Technical Paper

Dynamic Simulation Techniques for Steering of Tracked Agricultural and Forestry Vehicles

A procedure for simulating the dynamics of agricultural and forestry machines using mechanical system simulation software is presented. A soil/track interface model including rubber-track and steel-track was introduced as well as equations that can be used to model mechanical and hydraulic power trains commonly found in tracked vehicles. Two rubber-tracked vehicles (agricultural tractors) and two steel-tracked machines (forestry vehicles) were simulated to illustrate the technique, and some analysis results are presented. The examples given in this paper are based on the author’s research over the past several years.
Technical Paper

Education and Outreach Program Designed for NASA Specialized Center of Research and Training in Advance Life Support (ALS/NSCORT)

The NASA Specialized Center of Research and Training in Advanced Life Support (ALS/NSCORT) Education and Outreach Program is designed to engage audiences through concepts and technologies highlighted in the NSCORT research program. The outreach program is composed of three thrust areas. These areas are technical outreach (graduate education, technology transfer, presentations to industry, etc.), educational outreach (professional development, undergraduate, K-12), and public outreach (museums, state fairs, etc.) Program design of the technical and educational outreach began in January 2003. This paper reports anecdotal data on one ALS/NSCORT outreach program and gives a brief description of the other programs in their pilot stages. Technical and educational outreach programs developed to date include: 1) Summer Fellowship Research Program, 2) Distance Learning Course, 3) Key Learning Community Collaborative Project and 4) Mission to Mars.
Technical Paper

Effects of Geometric Parameters on the Sound Transmission Characteristic of Bulb Seals

Sound transmission through door and window sealing systems is one important contributor to vehicle interior noise. The noise generation mechanism involves the vibration of the seal due to the unsteady wall pressures associated with the turbulent flow over the vehicle. For bulb seals, sound transmission through the seal is governed by the resonance of the seal membranes and the air cavity within the bulb (the so-called mass-air-mass resonance). The objective of this study was to develop a finite element (FE) model to predict the sound transmission loss of elastomeric bulb seals. The model was then exercized to perform a parametric study of the influence of seveal seal design parameters. The results suggest that the sound transmission loss increases as the membrane thicknesses and/or the separation distance between the two seal walls are increased. The addition of additional internal “webs” was found to have adverse effects on the sound barrier performance.
Technical Paper

Effects of Window Seal Mechanical Properties on Vehicle Interior Noise

One dominant “wind noise” generating mechanism in road vehicles is the interaction between turbulent flows and flexible structures which include side glass windows. In this study, the effects of seal mechanical properties on the sound generated from flow-induced vibration of side glass windows were investigated. The primary goal was to assess the influence of seal support properties on the noise generated from a plate. Two different models to calculate the optimal support stiffness of the seal that minimizes the velocity response are presented. The results show that both the velocity response and the sound radiation are strongly influenced by dissipation of vibration energy at the edges. It is demonstrate that support tuning can yield significant noise and vibration reduction.
Technical Paper

Equivalent System Mass of Producing Yeast and Flat Breads from Wheat Berries, A Comparison of Mill Type

Wheat is a candidate crop for the Advanced Life Support (ALS) system, and cereal grains and their products will be included on long-term space missions beyond low earth orbit. While the exact supply scenario has yet to be determined, some type of post-processing of these grains must occur if they are shipped as bulk ingredients or grown on site for use in foods. Understanding the requirements for processing grains in space is essential for incorporating the process into the ALS food system. The ESM metric developed by NASA describes and compares individual system impact on a closed system in terms of a single parameter, mass. The objective of this study was to compare the impact of grain mill type on the ESM of producing yeast and flat breads. Hard red spring wheat berries were ground using a Brabender Quadrumat Jr. or the Kitchen-Aid grain mill attachment (both are proposed post-harvest technologies for the ALS system) to produce white and whole wheat flour, respectively.