The purpose of this thesis is to study and develop intelligent agents for the forthcoming Space S... more The purpose of this thesis is to study and develop intelligent agents for the forthcoming Space Station Freedom. Relevant intelligent capabilities, which are necessary in a semi-autonomous laboratory environment, are assumed to be built into a robot. An intelligent controller based on the DEVS formalism and the event-based approach is considered for an experiment. We shall discuss multiple model representations, where each model is tailored toward a specific purpose. Considering the necessity of diagnostic capabilities, we shall discuss the possibility of hierarchical diagnostic units for the Space Station. A high-level diagnostic unit is implemented on the basis of an artificial intelligence scheme and a hierarchy of diagnosers. This thesis also discusses the need for real-time diagnostic units and real-time data acquisition. We shall consider a constraint driven diagnostic unit which utilizes the time/cost (i.e., the actual associated cost or time in inquiring information necessary for a diagnosis process) criterion in an attempt to locate the cause(s) of failures
Performance analysis and verification of Cyber-Physical Systems (CPS) is of utmost importance due... more Performance analysis and verification of Cyber-Physical Systems (CPS) is of utmost importance due to the cruciality of the decision making in such systems. Therefore, modeling can be beneficial especially for issues related to the tight coupling between computational and physical parts. In this work, we utilize the extensive research on the simulation and model-checking for designing computational-physical interactions in the context of CPS. We also propose an action-level model-driven activity modeling approach based on DEVS. We employ time intervals (TIs) to govern communication between computational and physical components at the level of actions. We extend the activities metamodel to instantiate activities suitable for time-critical cyber-physical systems. We create a DEVS-Suite generic library to simulate these models conforming to the parallel DEVS formalism. We demonstrate with a traffic vehicle intersection model and discuss some verification capabilities.
Creation of DEVS models has been advanced through Model Driven Architecture and its frameworks. T... more Creation of DEVS models has been advanced through Model Driven Architecture and its frameworks. The overarching role of the frameworks has been to help develop model specifications in a disciplined fashion. Frameworks can provide intermediary layers between the higher level mathematical models and their corresponding software specifications from both structural and behavioral aspects. Unlike structural modeling, developing models to specify behavior of systems is known to be harder and more complex, particularly when operations with non-trivial control schemes are required. In this paper, we propose specifying activity-based behavior modeling of parallel DEVS atomic models. We consider UML activities and actions as fundamental units of behavior modeling, especially in the presence of recent advances in the UML 2.5 specifications. We describe in detail how to approach activity modeling with a set of elemental behavioral constructs for atomic DEVS model. We show how Activity models correspond to the atomic DEVS model using an exemplar. We also highlight the complementary roles of Activity and Statecharts models.
Abstractions are necessary to facilitate grounding and managing model development and simulation ... more Abstractions are necessary to facilitate grounding and managing model development and simulation experiments. Understanding the specific roles of different artifacts in abstractions is important to enrich the model development process. Actions and states reveal certain unique aspects about system behavior within and among component models. However, behavior specifications are not explicit and adequately supported in state-based formalisms. In this paper, we examine the role of actions in model specification in accordance with the notion of state in the modular and hierarchical parallel DEVS formalism. The resulting approach relies on the profoundness of DEVS while having a more intuitive abstraction around it via hierarchical activity metamodeling. Together the activity and DEVS modeling help simplify and strengthen specifying complex system behaviors as composition of atomic and coupled models. We show the importance of hierarchical DEVS activity modeling approach with a coordinator model as a part of a dual-server model.
Properties represent the state of a system at any instance of time or for a period of time. We co... more Properties represent the state of a system at any instance of time or for a period of time. We consider properties as a common concept for Experimental Frame (EF) that can be used for simulation and modeling checking. This affords to define experimental frames that can evaluate the dynamics of models of systems purposed for both validation and verification. We show this approach through simulation of Parallel DEVS models as well as model checking of Constrained-DEVS models. We develop experiments for simulating and model checking a prototypical Network-on-Chip (NoC) system. The models and experiments are developed and executed using the DEVS-Suite tool. New capabilities of this tool include support for defining experimental frames that stimulate and monitor executions of models. The proposed approach with the developed execution engine affords both simulation validation and model checking verification.
Joint Anti-submarine Systems (JAS) is a complex system employed in Anti-Submarine Warfare (ASW). ... more Joint Anti-submarine Systems (JAS) is a complex system employed in Anti-Submarine Warfare (ASW). Current research in this domain, however, mainly focuses on pure theoretical analysis or unable to support efficient simulations. Consequently these works cannot be effectively applied to develop simulations that can represent and evaluate requirements and tactical designs. This paper discusses a WESS (Weapon Effectiveness Simulation Systems)-based method for JAS simulation through designing routes for helicopters. Firstly, we specified the hierarchical structure of JAS complexity from two perspectives. One is the 'part of' hierarchy which specifies parts of systems as component diagrams. While the other is the 'is a' hierarchy specifying inheritance relationships among parts of systems as class diagrams. After that, in order to lock the adversary submarine in a closed area, through a circle calculation the circle search pattern is introduced to display a tactical way to design waypoints for helicopters. Upon the WESS framework we developed an exemplar simulation scenario integrated with script-based decision scripts to process simulation and demonstratively presented the two-dimensional screenshot of the circle pattern. It is shown that the proposed method can improve the efficiency of simulation application development to meet those requirements mentioned above.
It is essential to use modeling methods for specifying real-time and safety-critical specificatio... more It is essential to use modeling methods for specifying real-time and safety-critical specifications and executions as a set of computational and physical components. Thus, frameworks supporting modular, hierarchical specifications at multiple levels of abstraction for software-intensive systems are needed. Models for the structures, behaviors, and relationships benefit from separating and combining external properties and internal operations of components. Together, the Architecture Analysis and Design Language (AADL) and Discrete-Event System Specification (DEVS) provide an integrated framework where the structure and behavior designs can be systematically developed and evaluated. Needs including latency and safety analyses are supported by AADL whereas behavioral verification and validation can be supported with DEVS simulation. To create the proposed AADL-DEVS framework, a DEVS behavioral annex targeted for the DEVS-Suite simulator is developed and introduced to OSATE which supports AADL. The DEVS Annex language is detailed and exemplified using an infant incubator known as the Isolette system.
Speeding up the simulation of discrete-event wafer fab models is essential because optimizing the... more Speeding up the simulation of discrete-event wafer fab models is essential because optimizing the scheduling and dispatching policies under various circumstances requires repeated evaluation of the decision candidates during parameter-space exploration. In this paper, we present a runtime abstraction-level conversion approach for discrete-event wafer-fabrication (wafer-fab) models to gain simulation speedup. During the simulation, if a machine group of the wafer fab models reaches a steady state, then the proposed approach attempts to substitute this group model with a mean-delay model (MDM) as a high abstraction level model. The MDM abstracts the detailed operations of the group's sub-component models into an average delay based on the queueing modeling, which can guarantee acceptable accuracy under steady state. The proposed abstraction-level converter (ALC) observes the queueing parameters of low-level groups to identify the convergence of each group's work-in-progress (WIP) level through a statistical test. When a group's WIP level is converged, the output-to-input couplings between the models are revised to change a wafer-lot process flow from the low-level group to a mean-delay model. When the ALC detects a divergence caused by a re-entrant flow or a machine-down, the high-level model is switched back to its corresponding low-level group model. The ALC then generates dummy wafer-lot events to synchronize the busyness of high-level steady state. The proposed method was applied to case studies of wafer-fab systems and achieves simulation speedup from 6.1 to 11.8 times with corresponding 2.5 to 5.9% degradation inaccuracy.
In previous work, we proposed modeling and simulation of UML activities in Parallel DEVS. With re... more In previous work, we proposed modeling and simulation of UML activities in Parallel DEVS. With respect to parallelism, either one of the following statements holds true about the semantics of activities in order to attain a valid execution. A time base, regardless of its granularity, shall be explicitly defined in order to account for parallelism in a simulation environment with sequential execution. Or, the environment shall be physically parallel in multiple processes. We examine the former by dissecting into some of its properties that are related to control constructs within activity modeling in the viewpoint of Parallel DEVS formalism.
The purpose of this thesis is to study and develop intelligent agents for the forthcoming Space S... more The purpose of this thesis is to study and develop intelligent agents for the forthcoming Space Station Freedom. Relevant intelligent capabilities, which are necessary in a semi-autonomous laboratory environment, are assumed to be built into a robot. An intelligent controller based on the DEVS formalism and the event-based approach is considered for an experiment. We shall discuss multiple model representations, where each model is tailored toward a specific purpose. Considering the necessity of diagnostic capabilities, we shall discuss the possibility of hierarchical diagnostic units for the Space Station. A high-level diagnostic unit is implemented on the basis of an artificial intelligence scheme and a hierarchy of diagnosers. This thesis also discusses the need for real-time diagnostic units and real-time data acquisition. We shall consider a constraint driven diagnostic unit which utilizes the time/cost (i.e., the actual associated cost or time in inquiring information necessary for a diagnosis process) criterion in an attempt to locate the cause(s) of failures
Performance analysis and verification of Cyber-Physical Systems (CPS) is of utmost importance due... more Performance analysis and verification of Cyber-Physical Systems (CPS) is of utmost importance due to the cruciality of the decision making in such systems. Therefore, modeling can be beneficial especially for issues related to the tight coupling between computational and physical parts. In this work, we utilize the extensive research on the simulation and model-checking for designing computational-physical interactions in the context of CPS. We also propose an action-level model-driven activity modeling approach based on DEVS. We employ time intervals (TIs) to govern communication between computational and physical components at the level of actions. We extend the activities metamodel to instantiate activities suitable for time-critical cyber-physical systems. We create a DEVS-Suite generic library to simulate these models conforming to the parallel DEVS formalism. We demonstrate with a traffic vehicle intersection model and discuss some verification capabilities.
Creation of DEVS models has been advanced through Model Driven Architecture and its frameworks. T... more Creation of DEVS models has been advanced through Model Driven Architecture and its frameworks. The overarching role of the frameworks has been to help develop model specifications in a disciplined fashion. Frameworks can provide intermediary layers between the higher level mathematical models and their corresponding software specifications from both structural and behavioral aspects. Unlike structural modeling, developing models to specify behavior of systems is known to be harder and more complex, particularly when operations with non-trivial control schemes are required. In this paper, we propose specifying activity-based behavior modeling of parallel DEVS atomic models. We consider UML activities and actions as fundamental units of behavior modeling, especially in the presence of recent advances in the UML 2.5 specifications. We describe in detail how to approach activity modeling with a set of elemental behavioral constructs for atomic DEVS model. We show how Activity models correspond to the atomic DEVS model using an exemplar. We also highlight the complementary roles of Activity and Statecharts models.
Abstractions are necessary to facilitate grounding and managing model development and simulation ... more Abstractions are necessary to facilitate grounding and managing model development and simulation experiments. Understanding the specific roles of different artifacts in abstractions is important to enrich the model development process. Actions and states reveal certain unique aspects about system behavior within and among component models. However, behavior specifications are not explicit and adequately supported in state-based formalisms. In this paper, we examine the role of actions in model specification in accordance with the notion of state in the modular and hierarchical parallel DEVS formalism. The resulting approach relies on the profoundness of DEVS while having a more intuitive abstraction around it via hierarchical activity metamodeling. Together the activity and DEVS modeling help simplify and strengthen specifying complex system behaviors as composition of atomic and coupled models. We show the importance of hierarchical DEVS activity modeling approach with a coordinator model as a part of a dual-server model.
Properties represent the state of a system at any instance of time or for a period of time. We co... more Properties represent the state of a system at any instance of time or for a period of time. We consider properties as a common concept for Experimental Frame (EF) that can be used for simulation and modeling checking. This affords to define experimental frames that can evaluate the dynamics of models of systems purposed for both validation and verification. We show this approach through simulation of Parallel DEVS models as well as model checking of Constrained-DEVS models. We develop experiments for simulating and model checking a prototypical Network-on-Chip (NoC) system. The models and experiments are developed and executed using the DEVS-Suite tool. New capabilities of this tool include support for defining experimental frames that stimulate and monitor executions of models. The proposed approach with the developed execution engine affords both simulation validation and model checking verification.
Joint Anti-submarine Systems (JAS) is a complex system employed in Anti-Submarine Warfare (ASW). ... more Joint Anti-submarine Systems (JAS) is a complex system employed in Anti-Submarine Warfare (ASW). Current research in this domain, however, mainly focuses on pure theoretical analysis or unable to support efficient simulations. Consequently these works cannot be effectively applied to develop simulations that can represent and evaluate requirements and tactical designs. This paper discusses a WESS (Weapon Effectiveness Simulation Systems)-based method for JAS simulation through designing routes for helicopters. Firstly, we specified the hierarchical structure of JAS complexity from two perspectives. One is the 'part of' hierarchy which specifies parts of systems as component diagrams. While the other is the 'is a' hierarchy specifying inheritance relationships among parts of systems as class diagrams. After that, in order to lock the adversary submarine in a closed area, through a circle calculation the circle search pattern is introduced to display a tactical way to design waypoints for helicopters. Upon the WESS framework we developed an exemplar simulation scenario integrated with script-based decision scripts to process simulation and demonstratively presented the two-dimensional screenshot of the circle pattern. It is shown that the proposed method can improve the efficiency of simulation application development to meet those requirements mentioned above.
It is essential to use modeling methods for specifying real-time and safety-critical specificatio... more It is essential to use modeling methods for specifying real-time and safety-critical specifications and executions as a set of computational and physical components. Thus, frameworks supporting modular, hierarchical specifications at multiple levels of abstraction for software-intensive systems are needed. Models for the structures, behaviors, and relationships benefit from separating and combining external properties and internal operations of components. Together, the Architecture Analysis and Design Language (AADL) and Discrete-Event System Specification (DEVS) provide an integrated framework where the structure and behavior designs can be systematically developed and evaluated. Needs including latency and safety analyses are supported by AADL whereas behavioral verification and validation can be supported with DEVS simulation. To create the proposed AADL-DEVS framework, a DEVS behavioral annex targeted for the DEVS-Suite simulator is developed and introduced to OSATE which supports AADL. The DEVS Annex language is detailed and exemplified using an infant incubator known as the Isolette system.
Speeding up the simulation of discrete-event wafer fab models is essential because optimizing the... more Speeding up the simulation of discrete-event wafer fab models is essential because optimizing the scheduling and dispatching policies under various circumstances requires repeated evaluation of the decision candidates during parameter-space exploration. In this paper, we present a runtime abstraction-level conversion approach for discrete-event wafer-fabrication (wafer-fab) models to gain simulation speedup. During the simulation, if a machine group of the wafer fab models reaches a steady state, then the proposed approach attempts to substitute this group model with a mean-delay model (MDM) as a high abstraction level model. The MDM abstracts the detailed operations of the group's sub-component models into an average delay based on the queueing modeling, which can guarantee acceptable accuracy under steady state. The proposed abstraction-level converter (ALC) observes the queueing parameters of low-level groups to identify the convergence of each group's work-in-progress (WIP) level through a statistical test. When a group's WIP level is converged, the output-to-input couplings between the models are revised to change a wafer-lot process flow from the low-level group to a mean-delay model. When the ALC detects a divergence caused by a re-entrant flow or a machine-down, the high-level model is switched back to its corresponding low-level group model. The ALC then generates dummy wafer-lot events to synchronize the busyness of high-level steady state. The proposed method was applied to case studies of wafer-fab systems and achieves simulation speedup from 6.1 to 11.8 times with corresponding 2.5 to 5.9% degradation inaccuracy.
In previous work, we proposed modeling and simulation of UML activities in Parallel DEVS. With re... more In previous work, we proposed modeling and simulation of UML activities in Parallel DEVS. With respect to parallelism, either one of the following statements holds true about the semantics of activities in order to attain a valid execution. A time base, regardless of its granularity, shall be explicitly defined in order to account for parallelism in a simulation environment with sequential execution. Or, the environment shall be physically parallel in multiple processes. We examine the former by dissecting into some of its properties that are related to control constructs within activity modeling in the viewpoint of Parallel DEVS formalism.
Hajj is one of the largest mass gatherings where Muslims from all over the world gather in Makah ... more Hajj is one of the largest mass gatherings where Muslims from all over the world gather in Makah each year for pilgrimage. A mass assembly of such scale bears a huge risk of disaster either natural or man-made. In the past few years, thousands of casualties have occurred while performing different Hajj rituals, especially during the Circumambulation of Kaba (Tawaf) due to stampede or chaos. During such calamitous situations, an appropriate evacuation strategy can help resolve the problem and mitigate further risk of causalities. It is however a daunting research problem to identify an optimal course of action based on several constraints. Modeling and analyzing such a problem of real-time and spatially explicit complexity requires a microscale crowd simulation and analysis framework. Which not only allows the modeler to express the spatial dimensions and features of the environment in real scale, but also provides modalities to capture complex crowd behaviors. In this paper, we propose an Agent-based Crowd Simulation & Analysis framework that incorporates the use of Anylogic Pedestrian library and integrates/interoperate Anylogic Simulation environment with the external modules for optimization and analysis. Hence provides a runtime environment for analyzing complex situations, e.g., emergency evacuation strategies. The key features of the proposed framework include: (i) Ability to model large crowd in a spatially explicit environment at real-scale; (ii) Simulation of complex crowd behavior such as emergency evacuation; (iii) Interoperability of optimization and analysis modules with simulation runtime for evaluating evacuation strategies. We present a case study of Hajj scenario as a proof of concept and a test bed for identifying and evaluating optimal strategies for crowd evacuation CCS Concepts • Computing methodologies ➝ Modeling and simulation ➝Simulation types and techniques ➝ Agent / discrete models. • Computing methodologies ➝ Modeling and simulation ➝ Simulation support systems ➝ Simulation tools. • Computing methodologies ➝ Machine learning ➝ Machine learning approaches ➝ Bio-inspired approaches ➝ Genetic algorithms. • Computing methodologies ➝ Modeling and simulation ➝ Model development and analysis ➝ Modeling methodologies.
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