DRUM :: Browsing by Author "Austin, Mark"

Browsing by Author "Austin, Mark"

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ALADDIN: A Computational Toolkit for Interactive Engineering Matrix and Finite Element Analysis
(1995) Austin, Mark; Chen, Xiaoguang; Lin, Wane-Jang; ISR
This report describes Version 1.0 of ALADDIN, an interaction computational toolkit for the matrix and finite element analysis of engineering systems. The ALADDIN package is designed around a language specification that includes quantities with physical units, branching constructs and looping constructs. The basic language functionality is enhanced with external libraries of matrix and finite element functions.
Almost Poisson Integration of Rigid Body Systems
(1991) Austin, Mark; Krishnaprasad, Perinkulam S.; Wang, L.S.; ISR
In this paper we discuss the numerical integration of Lie-Poisson Systems using the mid-point rule. Since such systems result from the reduction of hamiltonian systems with symmetry by Lie Group actions, we also present examples of reconstruction rules for the full dynamics. A primary motivation is to preserve in the integration process, various conserved quantities of the original dynamics. A main result of this paper is a third order error estimate for the Lie-Poisson structure where h is the integration step-size. We note that Lie-Poisson systems appear naturally in many areas of physical science and engineering, including theoretical mechanics of fluids and plasmas, satellite dynamics, and polarization dynamics. In the present paper we consider a series of progressively complicated examples related to rigid body systems. We also consider a dissipative example associated to a Lie-Poisson system. The behavior of the mid-point rule and an associated reconstruction rule is numerically explored.
Compositional Behavior Modeling and Formal Validation of Canal System Operations with Finite State Automata
(2011-06) Austin, Mark; Johnson, John
Traditional approaches to the formal analysis of canal system operations focus on performance. However, now that canal system operations are moving toward increased use of automation in their day-to-day operations, there is a strong need for formal analysis of system functionality with respect to correctness of operations. This report describes a compositional approach to the multi-level behavior modeling and formal validation of canal system operations with hierarchies and networks of finite state automata. Models and specifications of behavior are formally designed as labeled transition systems. To avoid the well-known state explosion problem, we develop a new procedure for viewpoint-action-process traceability, thereby allowing parts of a problem not relevant to a specific decision to be removed from consideration. Key features of the methodology are illustrated through development of behavior models and validation procedures for lockset- and system-level concerns in the Panama Canal System.
Computational Assessment of Suboptimal Bang-Bang Control Strategies for Performance-Based Design of Base Isolated Structures
(2005) Sebastianelli, Robert; Austin, Mark; ISR; SEIL
This report explores the symbolic solution of the Lyapunov matrix equation as it applies to modified bang-bang control of base isolated structures. We present the Modified Bang-Bang Control strategy for active control of structures. Based on energy concepts, we formulate a rational choice of the ``${ f Q}$" matrix that partitions the amount of potential energy in a base isolated system into two parts: (1) potential energy directed to the main structural system, and (2) potential energy directed to the isolation devices. This symbolic analysis of a 2-DOF system leads to investigating a choice of the ${ f Q}$ matrix that minimizes the entire potential and/or kinetic energy of a emph{n}-DOF structure during an earthquake ground event. Using symbolic analyis procedures, We show that when the entire potential and/or kinetic energy of a emph{n}-DOF structure with uniform mass is minimized, solutions to the Lyapunov matrix equation assume a greatly simplified form. Moreover, this solution to the modified bang-bang control problem is easily calculated without needing to solve the Lyapunov matrix equation. Modified bang-bang control can be easily incorporated into the second-order differential equation of motion for the structure giving intuitive insight as to the effect of active control on the response of the structure. We show that this control strategy is insensititive to localized, nonlinear stiffness changes in the base isolators and therefore is well-suited for this problem area.
Energy- and Power-Balance Assessment of Base Isolated Structures Supplemented with Modified Bang-Bang Control
(2005) Sebastianelli, Robert; Austin, Mark; ISR; SEIL
This report is the second in series investigating the feasibility of supplementing base isolation with active bang-bang control mechanisms. We formulate discrete approximations to energy- and power-balance equations for a base isolated structure supplemented with constant stiffness bang-bang (CKBB) control. Numerical experiments are conducted to: (1) Identify situations when constant stiffness bang-bang control is most likely to ``add value' to system responses due to base isolation alone, and (2) Quantitatively determine the work done and power required by the actuators. A key observation from the numerical experiments is that ``overall performance' of the actuators is coupled to ``input energy per unit time.'
Framework for Knowledge-Based Fault Detection and Diagnostics in Multi-Domain Systems: Application to HVAC Systems
(2017-11-13) Delgoshaei, Parastoo; Austin, Mark
State-of-the-art fault detection methods are equipment and domain specific and non-comprehensive. As a result, the applicability of these methods in different domains is very limited and they can achieve significant levels of performance by having knowledge of the domain and the ability to mimic human thinking in identifying the source of a fault with a comprehensive knowledge of the system and its surroundings. This technical report presents a comprehensive semantic framework for fault detection and diagnostics (FDD) in systems simulation and control. Our proposed methodology entails of implementation of the knowledge bases for FDD purposes through the utilization of ontologies and offers improved functionalities of such system through inference-based reasoning to derive knowledge about the irregularities in the operation. We exercise the proposed approach by working step by step through the setup and solution of a fault detection and diagnostics problem for a small-scale heating, ventilating and air-conditioning (HVAC) system.
Graph-Based Visualization of System Requirements Organized for Team-Based Design
(2005) Mayank, Vimal; Kositsyna, Natalya; Austin, Mark; ISR; SEIL
When requirements are organized into levels for team development, graph structures are needed to describe the comply and define relationships among requirements. Yet, a number of present-day requirements engineering tools employ a tree-based model to display relationships among requirements. While this strategy of development simplifies the details of implementation, it unfortunately also causes gaps to appear between the visual representation and the underlying graph-based data structures. Systems engineers currently use manual procedures to identify and close these gaps. To mitigate the limitations of this slow and error prone process, this report describes the formulation of algorithms and development of a Java-based requirements visualization tool called called PaladinRM. PaladinRM can read a tree representation of requirements exported from a database, and construct and visualize the block diagram representation with all duplicate nodes removed.
High Order Integration of Smooth Dynamical Systems: Theory and Numerical Experiments
(1991) Austin, Mark; ISR
This paper describes a new class of algorithms for integrating linear second order equations, and those containing smooth nonlinearities. The algorithms are based on a combination of ideas from standard Newmark integration methods, and extrapolation techniques. For the algorithm to work, the underlying Newmark method must be stable, second order accurate, and produce asymptotic error expansions for response quantities containing only even ordered terms. It is proved that setting the Newmark parameter t to 1/2 gives a desirable asymptotic expansion, irrespective of the setting for ݮ Numerical experiments are conducted for two linear and two nonlinear applications.
Methodology and System for Ontology-Enabled Traceability: Pilot Application to Design and Management of the Washington D.C. Metro System
(2010-12-20) Austin, Mark; Wojcik, Cari
This report describes a new methodology and system for satisfying requirements, and an architectural framework for linking discipline-specific dependencies through interaction relationships at the meta-model (or ontology) level. In state-of-the-art traceability mechanisms, requirements are connected directly to design objects. Here, in contrast, we ask the question: What design concept (or family of design concepts) should be applied to satisfy this requirement? Solutions to this question establish links between requirements and design concepts. Then, it is the implementation of these concepts that leads to the design itself. These ideas are prototyped through a Washington DC Metro System requirements-to-design model mockup. The proposed methodology offers several benefits not possible with state-of-the-art procedures. First, procedures for design rule checking may be embedded into design concept nodes, thereby creating a pathway for system validation and verification processes that can be executed early in the systems lifecycle where errors are cheapest and easiest to fix. Second, the proposed model provides a much better big-picture view of relevant design concepts and how they fit together, than is possible with linking of domains at the model level. And finally, the proposed procedures are automatically reusable across families of projects where the ontologies are applicable.
Model-Based Design and Formal Verification Processes for Automated Waterway System Operations
(MDPI, 2016-06-07) Petnga, Leonard; Austin, Mark
Waterway and canal systems are particularly cost effective in the transport of bulk and containerized goods to support global trade. Yet, despite these benefits, they are among the most under-appreciated forms of transportation engineering systems. Looking ahead, the long-term view is not rosy. Failures, delays, incidents and accidents in aging waterway systems are doing little to attract the technical and economic assistance required for modernization and sustainability. In a step toward overcoming these challenges, this paper argues that programs for waterway and canal modernization and sustainability can benefit significantly from system thinking, supported by systems engineering techniques. We propose a multi-level multi-stage methodology for the model-based design, simulation and formal verification of automated waterway system operations. At the front-end of development, semi-formal modeling techniques are employed for the representation of project goals and scenarios, requirements and high-level models of behavior and structure. To assure the accuracy of engineering predictions and the correctness of operations, formal modeling techniques are used for the performance assessment and the formal verification of the correctness of functionality. The essential features of this methodology are highlighted in a case study examination of ship and lock-system behaviors in a two-stage lock system.
Phase Analysis of Actuator Response for Sub-Optimal Bang-Bang and Velocity Cancellation Control of Base Isolated Structures
(2005) Austin, Mark; Sebastianelli, Robert; ISR; SEIL
Starting with simplified models of displacement response for a base isolated structure supplemented with sub-optimal bang-bang control, we formulate models of phase analysis of actuator force direction in relation to system displacements and velocities. For the case of steady state displacement response, we prove that the direction of actuator application can neither be perfectly in phase with displacements, nor perfectly in phase with velocities. In practice, however, the actuator force direction is ``almost in phase' with velocities and ``almost orthogonal' to sign changes in displacements. This observation suggests that a very simple velocity cancellation control might be effective in adding value to base isolation system responses. Numerical experiments are conducted to assess improvements in performance due to sub-optimal bang-bang control and velocity cancellation control, and to validate the extent to which the phase analysis predictions hold in linearly elastic and nonlinear time-domain settings.
Pre-Processor for Finite Element Analysis of Highway Bridges
(1990) Creighton, Steven L.; Austin, Mark; Albrecht, Pedro; ISR
Historically, the lack of interactive pre-processors to setup tedious finite element problem descriptions has hindered the use of the finite element method for bridge analysis. The work performed in the present study mitigates this problem via the use of highspeed engineering workstations. This report presents an interactive, graphically based pre-processor for the analysis of highway bridges with the finite element method. With the pre- processor, bridge design engineers can use both keyboard and mouse styles of interaction to describe bridge geometries. The UNIX tool YACC has been used to create a command language for describing and manipulating of structural geometries, material types, loads, and boundary conditions. The pre-processor was successfully used to create input files in a format acceptable to the finite element analysis program ANSYS. In fact, less than 20 minutes was needed to create a finite element model of the prototype bridge tested at the Turner-Fairbanks Laboratory in Langley, Virginia, in a joint FHWA-AISI project. This report describes the development of the pre-processor in words that can hopefully be understood by civil engineers and computer scientists alike.
Requirements Engineering and the Semantic Web
(2003) Selberg, Scott A.; Austin, Mark; ISR
This report establishes a connection between the field of requirementsengineering and the Semantic Web. The basis of the connection comes fromidentifying both environments as Systems of Systems. The connectionbrings an ability to apply design strategies and solutions from theSemantic Web to current day requirements engineering problems. Thishas immediate and long term advantages over current industry tools.
Requirements Engineering and the Semantic Web, Part II. Representaion, Management, and Validation of Requirements and System-Level Architectures
(2004) Mayank, Vimal; Kositsyna, Natalya; Austin, Mark; ISR
This report is the second in a series on "Requirements Engineering and the Semantic Web." The objectives are to study the application of RDF, ontologies and logic for the representation and management of requirements and system-level architectures.
Solid Modeling of Reinforced Concrete Beams, Part I: Data Structures and Algorithms, Part II: Computational Environment
(1991) Austin, Mark; Preston, J.L.; ISR
This 2-part paper describes a solid modeling methodology for the interactive design and analysis of reinforced concrete (RC) beam structures. Part I covers the data structure and algorithms for steel reinforcing bar trajectories, and a three dimensional boundary representation of the concrete beam solid. Algorithms are given for slicing the beam, extracting cross sections, and computing the ultimate strength. Part 2 of this series discuss the design and implementation of an interactive design environment called Beam Tool.
Structural Matrix Computations with Units: Data Structures, Algorithms, and Scripting Language Design
(1999) Austin, Mark; Lin, Wane-Jang; Chen, Xiaoguang; ISR
Despite the well-known benefits of physical units, matrices,and matrix algebra in engineering computations,most engineering analysis packages are essentially dimensionless.They simply hold the engineer responsible for selecting a set ofengineering units and making sure their use is consistent.While this practice may be satisfactory for the solution ofself-contained and well-established problem-solving procedures,where the structure of the output is well known and understood,identifying and correcting unintentional errors in the solution ofnew and innovative computations can be significantly easierwhen units are an integral part of the computation procedure.
This report begins with a description of thedata structures and algorithms needed torepresent and manipulate physical quantity variables,and matrices of physical quantities.
The second half of this report focuses on the implementation of Aladdin,a new computational environment for matrix and finite element calculations.Aladdin employs a novel combination of system programming languages,scripting language concepts, and stack machine technology.The result is a high-level scripting language that offers enhancedtype checking for expressions and assignments,problem-oriented scaling of variables, automatic conversion of systems of units, and program control structures for the solution of engineering problems.
Functionality of the Aladdin stack machine is illustratedby working step by step through the parsing and execution ofa simple statement involving units.The capabilities of Aladdin are demonstrated through thedeflection analysis of a cantilever beam.
Structural Optimization in a Distributed Computing Environment
(1991) Voon, B.K.; Austin, Mark; ISR
This report presents the formulation and testing of a Feasible Sequential Quadratic Programming (FSQP-DIS) optimization algorithm customized to a Distributed Numerical Computing environment (DNC). DNC utilizes networking technology and an ensemble of loosely coupled processors to compute structural analyses concurrently. Each iterate of the FSQP-DIS is partitioned for concurrent computations in the direction calculation, and the steplength calculation. The prototype environment is tested on three applications; a mathematical programming problem, the design of a two-story planar steel frame, and finally, the optimal design of a two-story three- dimensional steel frame.
Synthesis and Validation of High-Level Behavior Models for Narrow Waterway Management Systems
(2005) Kaisar, Evangelos; Austin, Mark; ISR; SEIL
This report formulates a new methodology for the incremental transformation of informal operations concepts for a waterway management system into system-level designs, the latter being formal enough to support automated validation of anticipated component- and system-level behaviors. Scenario specifications and models of behavior are formally modeled as labeled transition systems (LTSs). Each object is the management system is assumed to have behavior that can be defined by a finite state machine; thus, the waterway management system architecture is modeled as a network of communicating finite state machines. Architecture-level behaviors are validated using the Labeled Transition System Analyzer (LTSA). We exercise the methodology by working step by step through the synthesis and validation of a high-level behavior model for a ship passing through a waterway network.
System Modeling and Traceability Applications of the Higraph Formalism
(2007-08-31) Fogarty, Kevin; Austin, Mark
This report examines the use of higraphs as a means of representing dependencies and relationships among multiple aspects of system development models (e.g., requirements, hardware, software, testing concerns). We show how some well-known diagram types in UML have counterpart higraph representations, how these models incorporate hierarchy and orthogonality, and how each model can be connected to the others in a useful (and formal) manner. Present-day visual modeling languages such as UML and SysML do not readily support: (1) The traceability mechanisms required for the tracking of requirements changes, and (2) Builtin support for systems validation. Higraphs also deviate from UML and SysML in their ability to model requirements, rules, and domain knowledge relevant to the development of models for system behavior and system structure. To accommodate these demands, an extension to the basic mathematical definition of higraphs is proposed. Capabilities of the extended higraph model are examined through model development for an office network computing system.
A Systems Approach to Nonlinear Finite Element Analysis of Shell Structures
(1995) Chen, Xiaoguang; Austin, Mark; ISR
This report describes a systems approach to the nonlinear finite element analysis of shell structures. The research objective is to understand the structure a small language and computational environment should take so that matrix and nonlinear finite element computations can interact in a seamless manner.
One four-node-thick shell finite element and one eight-node-thick shell finite element is formulated and implemented in ALADDIN [1]. The finite elements are based on a three-dimensional continuum formulation, and are simplified by assuming a flat element geometry. Numerical experiments are presented for in- plane displacements of a flat plate, and out-of-plane bending of a cantilever structure. In each case, material nonlinearities are modeled with bi-linear and Ramberg-Osgood stress-strain curves. The report concludes with recommendations for further work in the areas of nonlinear finite element solution procedures and enhancements to ALADDIN's problem-solving infrastructure.

Browsing by Author "Austin, Mark"

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