bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Unified Lyapunov Setting for Continuous and Discrete Time Sliding Mode Control
Authors: DeCarlo R. A. , Drakunov S. 
Published: January 2022

Abstract
This paper sets forth general conditions on the existence, boundedness, and proper gains of a control for stabilizing a nonlinear plant state trajectory to an equilibrium manifold S contained in the state space using a smooth quadratic Lyapunov function, V. To state such conditions we define a time-varying (possibly discontinuous in t) state-dependent decision manifold by considering the time-derivative of the quadratic Lyapunov function. The decision manifold disconnects the control space. At each instant of time, stability is achieved by choosing a control in an appropriate half space defined by the decision manifold so that the derivative of the Lyapunov function is negative definite. If the decision manifold moves continuously, then there is no need for a discontinuous (classical VSC) controller. If the decision manifold is discontinuous, then the need for a discontinuous control is clear. The formulation unifies the various VSC control strategies found in the literature under a single umbrella and suggests new structures. The formulation also provides a simple geometric understanding of the effect of matched and norm bounded disturbances and parameter variations on the control gains. These results are extended to arbitrary normed linear spaces which allow the results to be adapted to discrete-time and discrete-event systems. Several examples are given.
Role of the Crank-Slider Structural Deformations in the Prediction of the Instantaneous Engine Friction Torque
Authors: Chalhoub Nabil G. , Nehme Hassan , Henein Naeim , Bryzik Walter 
Published: January 2022

Abstract
The focus of the current study is to assess the effects of structural deformations of the crankshaft/connecting-rod/piston mechanism on the computation of the instantaneous engine friction torque. This study has to be performed in a fully controlled environment in order to isolate the effects of structural deformations from those of measurement errors or noise interference. Therefore, a detailed model, accounting for the rigid and flexible motions of the crank-slider mechanism and including Rezeka and Henein’s (1984) engine component friction formulations, is considered in this study. The model is used as a test bed to generate the engine friction torque, Tfa, and to predict the rigid and flexible motions of the system in response to the cylinder gas pressure.
The torsional vibrations and the angular velocity of the crankshaft, as predicted by the detailed model of the crank-slider mechanism, are used along with the cylinder gas pressure in the (P-ω) method to estimate the engine friction torque, Tfe. This method is well suited for the purpose of this study because its formulation is based on the rigid body model of the crank-slider mechanism.
The digital simulation results demonstrate that the exclusion of the structural deformations from the formulation of the (P-ω) method leads to an overestimation of the friction torque near the top-dead-center (TDC) position of the piston under firing conditions. Moreover, for the remainder of the engine cycle, the estimated friction torque exhibits large oscillations and takes on positive numerical values as if it is inducing energy into the system.
Dynamic Modeling of Multi-Unit Heavy Vehicles
Authors: Tai Meihua , Tomizuka Masayoshi 
Published: January 2022

Abstract
In this paper, a unique method of deriving two kinds of models: simulation model and simplified control model for an arbitrary configuration of heavy vehicle (HV) system is proposed for the Automated Highway Systems (AHS). In the simulation model, each unit of a heavy vehicle system is considered as a free body with 6 degree of freedom unless constrained by the hitching mechanisms. The roll and pitch coupling due to constraints between connected units is investigated from the geometric point of view, and the dynamics of the hitching mechanisms are incorporated. A simplifed control model is obtained independent from the simulation model. By the proper application of Newtonian and Lagrangian mechanics to the different parts of the simplified model equations, the holonomic constraint forces are eliminated from the dynamic equations of motion. The control model is given in a closed form. As a special case, an open-loop simulation of tractor-semitrailer simulation model is presented.
Design and Experimental Implementation of Control for a Platoon of Automated Vehicles
Authors: Rajamani Rajesh , Choi Seibum B. , Hedrick J. Karl , Law Boon , Prohaska Robert , Kretz Paul 
Published: January 2022

Abstract
This paper presents the design and experimental implementation of a longitudinal control system for the operation of automated vehicles in platoons. The control system on each vehicle is designed to have a hierarchical structure consisting of an upper level controller and a lower level controller. The upper controller determines the desired acceleration for each vehicle in the platoon so as to maintain constant accurate spacing between vehicles and ensure string stability in the platoon. The lower controller determines the throttle and/or brake commands required to track the desired acceleration. The design of the lower level controller for low speed operation is made difficult by the fact that the torque converter remains unlocked and the engine speed is not directly proportional to vehicle speed. In addition, the drive torque drops to zero for a brief time interval during each gear shift. Solutions to overcome these low speed problems are described. The design of safe intra-platoon maneuvers so as to allow any car in the platoon to exit by making a lane change are presented. Design of the co-ordination between vehicles for these maneuvers is described. The paper presents extensive experimental results from the public NAHSC demonstration of automated highways conducted in August 1997 at San Diego, California. The demonstration included an eight-car platoon operating continuously over several weeks with passenger rides being given to visitors. The maneuvers demonstrated included starting the automated vehicles from complete rest, accelerating to cruising speed, allowing any vehicle to exit from the platoon, allowing new vehicles to join the platoon and bringing the platoon to a complete stop at the end of the highway.
Emergency Vehicle Maneuvers and Control Laws for Automated Highway Systems
Authors: Toy Charmaine , Leung Kevin , Alvarez Luis , Horowitz Roberto 
Published: January 2022

Abstract
In this paper the operation and transit of emergency vehicles on an Automated Highway System (AHS) designed under the control architecture proposed in the California PATH program is described. The term emergency vehicles is used in a general sense to describe vehicles, such as police cars, ambulances and tow trucks, that may service faults inside or outside the AHS. The transit of emergency vehicles requires intensive participation of the Coordination layer, which directs the interactions of neighboring vehicles, and the Link layer, which regulates traffic flow along stretches of highway. In this paper, we describe various strategies for these two hierarchical layers that are needed to assign high priority transit to emergency vehicles on the AHS. These Coordination and Link layer maneuvers circulate vehicles around the emergency vehicle in both free flowing and stopped traffic.
A New Methodology for Engine Diagnostics and Control Utilizing “Synthetic” Engine Variables: Theoretical and Experimental Results
Authors: Moskwa John J. , Wang Wenbo , Bucheger Duane J. 
Published: January 2022

Abstract
This paper describes new engine diagnostic methodologies and algorithms that simplify and improve combustion quality monitoring and closed loop engine control in order to meet stringent emission standards. The “synthetic” variables these algorithms produce can be used to indicate the work produced by each cylinder combustion event at all engine speeds, and can be effectively used for on-board combustion quality measurements, engine diagnostics, and closed-loop control. The algorithms are very simple in form, and these methodologies can be applied to compression ignition or spark ignition, 2-stroke or 4-stroke engines.
Both simulation and experimental results will be given for a two-stroke, two cylinder in-line engine. The rotational dynamics and firing sequence of this configuration of engine is very similar to a four-stroke, four cylinder in-line engine, and nearly identical results will be seen with these two designs. Even more dramatic improvements can be seen with engines of fewer cylinders because of greater variations in their inertial forces. The algorithms can be successfully applied to many other engine configurations as well. Therefore, benefits can be derived from the application of these algorithms and their “synthetic” variables to control strategies for almost all modern small and medium size automotive and marine engines, as well as utility engines used for lawn care, snow removal, and other similar applications.
A Control Design for a Flexible Two-Link System
Authors: Mutti James , Du Hongliu , Nair Satish S. 
Published: January 2022

Abstract
This paper investigates a particular control strategy for a flexible two-link system. The objective is to control the tip position of the flexible link to track a desired trajectory in the presence of system uncertainties. A nominal ARX model is developed for an experimental two-link setup. A neural network is used to model some of the uncertainties, and the network is then used in a particular control configuration. Preliminary results from the study are presented.
Fast Control of Linear Systems Subject to Input Constraints
Authors: Larsson P. Tomas , Ulsoy A. Galip 
Published: January 2022

Abstract
Efficient design of high performance automatic control systems is extremely important for complex high technology systems and their cost-effective development. To get the best cost-to-performance ratio one would like to be able to design a controller that takes full advantage of actuator capabilities, but this can lead to non-linear behavior due to actuator saturation. The saturation nonlinearities in the system may have severe effects on the system performance due, for example, to integrator-windup.
In this paper we present a new design method, based on Lyapunov stability theory, that incorporates the actuator constraints directly in the design of a state feedback controller with integral action. By incorporating the actuator constraints directly in the design method we can ensure better utilization of the available control effort in achieving the desired system behavior.
Model Identification of the JPL Microgyroscope
Authors: M’Closkey Robert T. , Gibson Steve , Hui Jason K. 
Published: January 2022

Abstract
This paper reports the experimental model identification of the Jet Propulsion Laboratory micromachined vibratory rate gyroscope. An adaptive lattice filter is used to identify a two-input/two-output transfer function of high order in a series of experiments at different gyro temperatures (the gyro dynamics are temperature dependent). The experiments indicate that the lattice filter algorithm is suitable for real-time adaptive sensor calibration by using test inputs of short duration (one second) to excite the sensor dynamics.
Environment, Safety and Health Considerations for Disposition of Department of Energy Facilites
Authors: Pyatt D. W. , Niyogi P. K. , Eng C. C. 
Published: January 2022

Abstract
Following the end of the Cold War, the Department of Energy’s (DOE) mission has been in transition from designing, testing, and building nuclear weapons to a cleanup mode of environmental restoration and surplus facility disposition. The Office of Environment Safety and Health (EH) has led the development of a standard that addresses health and safety concerns for this new mission. This standard utilizes the numerous regulatory documents developed over many years addressing design, construction and operation of these several thousand facilities. It utilizes the framework of an “integrated safety management” approach.
Foot Control Activation: Reciprocating vs. Pivoting
Authors: Barnett Ralph L. , Barroso Peter 
Published: January 2022

Abstract
Discriminating between the two most widely used foot control concepts, open-sided and side-shielded, requires, among other things, an understanding of reciprocating and pivoting foot motions. In single cycle machine operations, it was found that the hands are steadier when foot controls are activated by pivoting about the heel as opposed to reciprocating. Furthermore, the study reveals the counterintuitive result that the reciprocating motion delivers slightly more activations per unit time than the pivoting action. If safety is not a consideration, stroke rate, operator comfort and hand steadiness are maximized when foot controls are actuated by “riding the pedal” or “hold down/release.”
Product Enhancement Through Ceramic Shell Casting
Authors: Duncan Scott R. , Kramer Michelle A. 
Published: January 2022

Abstract
For the past thirty years, foundries have been experimenting with the use of polystyrene patterns to produce high quality castings. It is only in recent years that the ceramic shell (CS) casting process has been successfully implemented for the commercial production of steel castings. This paper describes the ceramic shell (CS) casting process and highlights how its unique characteristics facilitated the optimization of railroad center plate designs.
Improving Lateral Ride Quality of Freight Cars Using Hydraulic Yaw Dampers
Authors: Jeambey Jon R. 
Published: January 2022

Abstract
Lateral deck accelerations are an important measure of ride quality, particularly for rail shipment of finished automobiles and for intermodal rail cars. Automobiles are sensitive to cyclic lateral inputs, which may lead to resonance and vehicle damage. Intermodal loads are generally less sensitive to lateral accelerations. However, this equipment operates at high speed for long periods and has the greatest exposure to truck instability. Improving the stability of rail cars not only benefits ride quality but also reduces wear of the car and truck components.
This report details the reduction in lateral deck accelerations of autoracks and all-purpose spine cars when equipped with hydraulic yaw dampers. High speed stability measurements were recorded at the AAR Transportation Technology Center, Inc. (TTCI) near Pueblo, Colorado.
Crack Linkup at Multiple Site Damage
Authors: Ma L. , Kobayashi A. S. , Atluri S. N. , Tan P. W. 
Published: January 2022

Abstract
A commonly used design criterion for predicting the onset of crack link up at a multiple site damage (MSD) is when the sum of the plastic zones of two adjacent cracks is equal to the remaining ligament (Swift 1985, Broek et al 1994). The collapse load predicted by this criterion, however, will differ with the analytical plastic zone and in general, will yield a nonconservative load. Recently, Pyo et al (1997) have shown that the T* integral, which was designed for elastic-plastic fracture mechanics, can predict the extent of stable crack growth and the subsequent collapse load of wide-panel MSD experiments (deWit et al, 1994). The purpose of this paper is to present experimental/numerical results on stable crack growth and linkup of idealized MSD based on the T* integral.
Moiré interferometry was used to determine the orthogonal displacement fields surrounding stably growing cracks in 0.8 mm thick 2024-T3 aluminum specimens with two or three cracks. Fatigue precracked cracks extended toward each other from two circular holes, which were 25.4 mm apart to simulate fastener holes in airplane fuselage, close to the outside edges of the specimens. A longer center crack from a center hole in the wider, three-crack specimens with three holes spaced 25.4 mm apart, provided information on the lead crack effect. T*ε integral, where ε is the distance of an elongating integration contour from the stably growing crack, was evaluated from the Moiré data using the procedure established by Okada et al (1996). ε in all studies was equated to the specimen thickness. An elastic-plastic finite element (FE) model of the fracture specimens were executed in its generation mode (Kobayashi, 1979) by inputting the measured Moiré displacement data along the width, 20 mm away from the crackline, of the specimen. T*ε integral was evaluated using an equivalent domain integral (Nikishkov et al, 1987).
The experimentally and the FE determined T*ε’s were in excellent agreement with each other. Moreover, the T*ε variation with stable crack growth closely followed the stable crack growth results generated previously using standard fracture specimens (Omori et al, 1998). Thus stable crack growth data generated by standard fracture specimens can be used to predict crack growth of MSD cracks. Collapsed load was reached when the remaining ligament exceeded the tensile strength of the 2024-T3 sheet and the two cracks rapidly propagated toward each other in the two-crack specimens. For the three-crack specimen, the lead crack propagated toward the smaller two MSD cracks.
Energy Released by Interfacial Decohesion in a Two-Phase Composite System
Authors: Srinivas Mullahalli V. , Dvorak George J. 
Published: January 2022

Abstract
Under service loads or during fabrication and processing, certain fibrous composite plies may experience extensive decohesion, such as debonding and sliding at fiber-matrix interfaces. The effect of some of these damage processes on overall stiffness and on internal stress redistribution is analyzed here with the Transformation Field Analysis method (Dvorak and Benveniste, 1992, Proc. R. Soc., London, Vol. A437, p. 291), which simulates creation of new internal surfaces by equivalent eigenstrains applied to an undamaged elastic system. Simple expressions for change in potential energy of the damaged ply are also obtained using the Colonetti’s theorem. The analytical results are shown to be in good agreement with selected finite element solutions for unit cells. Applications indicate that the energy released by fiber debonding depends linearly on fiber radius.
Comparison of Stress Concentrations in Plain and 8-Harness Satin Weave Composites
Authors: Whitcomb John , Tang Xiaodong , Chapman Clinton 
Published: January 2022

Abstract
Stress distributions in plain and satin weave composites were calculated using three-dimensional finite element analysis. Comparisons of the distributions showed that some of the satin weave behavior is predictable from the far simpler plain weave model. However, some aspects of the behavior require more geometric information than is provided by a plain weave model.
Micromechanics-Based Modeling of Uniaxially and Biaxially Compressed Graphite/Epoxy Laminates
Authors: Hauert Serge , Potter Daniel S. , Gupta Vijay 
Published: January 2022

Abstract
Uniaxial and in-plane biaxial testing were conducted on cross-ply graphite/epoxy laminates with different orientations. Results from these investigations are presented here only for the [±45]12s samples under different stress states. The stress-strain behavior is related to microscopic events through micromechanics-based modeling. It is shown that crack nucleation starts in the matrix when the local shear stress exceeds the shear strength of the epoxy. Depending on the stress state in the plies, two types of cracks form: (i) transverse cracks and (ii) angled out-of-plane cracks. While transverse cracks slide and allow the sample to accommodate large strains, angled cracks lead to massive delamination and an overall brittle behavior.
A Local/Global Sandwich Homogenization Procedure for Finite Element Simulation
Authors: Tabiei Ala , Tanov Romil R. 
Published: January 2022

Abstract
A new finite element approach to sandwich shells is proposed. It uses existing shell finite elements formulated for homogeneous shells. The “sandwich” nature of the problem is hidden from the main finite element program. Based on several assumptions the proposed homogenization procedure calculates stress increments in a homogeneous fictitious material, called “equivalent”, which correspond to the strain increments in the equivalent material points. The stresses in the equivalent material are calculated based on the stress and strain fields in the sandwich layers, which are determined from the incoming strain field for the equivalent material. This procedure is most suitable for including strain softening and other material nonlinear behavior. The approach can be combined with shell elements formulated for homogeneous materials, based on Reissner-Mindlin shell theory or with elements based on a higher order shell theory. It avoids the necessity of formulating special shell elements for sandwich constructions, which in most cases, due to their large number of degrees of freedom, significantly decrease the computational efficiency of the finite element analysis. The sandwich homogenization procedure is combined with a composite micromechanics-based model for woven composites to analyze sandwich shells with woven fabric faces.
Advanced Composite Turbine Engine Experience
Authors: Fecke Theodore G. 
Published: January 2022

Abstract
The United States has a coordinated government/ industry turbine engine technology program in place to double propulsion capability by the year 2003. The Integrated High Performance Turbine Engine Technology (IHPTET) program is slightly more than half complete, with specific goals identified for engine thrust to weight, compressor exit temperature, acquisition and maintenance cost. The IHPTET program represents a significant improvement in turbine engine technology. The program plan is to achieve the goals in three steps Phases I-III each resulting in 30% improvement. The achievement of these goals is project through the use of advance aerodynamics, materials and design concepts. The successful demonstration of the IHPTET goals depends on the technical success of composite structures. All types of composites: OMC (Organic Matrix Composite), MMC (Metal Matrix Composites), CMC (Ceramic Matrix Composite) as well as C/C (Carbon-Carbon), have been aggressively works since the program began in 1988. The composite experiences before the IHPTET program will be included in the form of lesson learn.
The IHPTET program has worked all aspects of composite development design, failure mode behavior and fabrication. The thrust in OMC’s has been primarily focus on Life prediction, low cost fabrication techniques and High temperature (&gt;700F). The thrust in MMC’s has been mainly focus on fiber-reinforced titanium for high performance rotating engine hardware. The technology development includes design; failure mode behavior and testing of multiply engine components as well as Life prediction and low cost fabrication techniques, have been investigated. The thrust in high temperature composites CMC and C/C has been mainly focus on CMC’s. The technology development span both man-rate and non man-rate engine (cruise missile) applications, in the areas of design, failure mode behavior and testing of both rotating and nonrotating applications.
The payoffs to the aircraft derived from the IHPTET are enormous. Many radical new mission capabilities are made viable through the IHPTET program. The high Mach multi-role fighters as an example are only possible with a variable cycle design, which requires extensive use of composite structures. These new capabilities will provide truly affordable ways to carry out the military’s mission by allowing aircraft resources to effectively operate from fewer worldwide locations as well as more affordable and environmentally friendly.