Institute for Systems Research
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Item Framework for Knowledge-Based Fault Detection and Diagnostics in Multi-Domain Systems: Application to HVAC Systems(2017-11-13) Delgoshaei, Parastoo; Austin, MarkState-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.Item Compositional Behavior Modeling and Formal Validation of Canal System Operations with Finite State Automata(2011-06) Austin, Mark; Johnson, JohnTraditional 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.Item 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, CariThis 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.Item System Modeling and Traceability Applications of the Higraph Formalism(2007-08-31) Fogarty, Kevin; Austin, MarkThis 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.Item Synthesis and Validation of High-Level Behavior Models for Narrow Waterway Management Systems(2005) Kaisar, Evangelos; Austin, Mark; ISR; SEILThis 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.Item Phase Analysis of Actuator Response for Sub-Optimal Bang-Bang and Velocity Cancellation Control of Base Isolated Structures(2005) Austin, Mark; Sebastianelli, Robert; ISR; SEILStarting 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.Item Graph-Based Visualization of System Requirements Organized for Team-Based Design(2005) Mayank, Vimal; Kositsyna, Natalya; Austin, Mark; ISR; SEILWhen 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.Item Energy- and Power-Balance Assessment of Base Isolated Structures Supplemented with Modified Bang-Bang Control(2005) Sebastianelli, Robert; Austin, Mark; ISR; SEILThis 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.'Item Computational Assessment of Suboptimal Bang-Bang Control Strategies for Performance-Based Design of Base Isolated Structures(2005) Sebastianelli, Robert; Austin, Mark; ISR; SEILThis 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.Item 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; ISRThis 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.