Aleks Göllü

Hybrid dynamical systems

Several aspects of model consistency are addressed. The discussion is put in the context of a particular hybrid system, the disk controller. This multilayer hybrid dynamical system is extended to include two other layers: a user layer at the top to define more complex tasks, and a sequencer between the supervisor and the servo layer to permit synchronous control.<<ETX>>

SHIFT: A Formalism and a Programming Language for Dynamic Networks of Hybrid Automata

SHIFT is a programming language for the specification and simulation of dynamic networks of hybrid automata. Such systems consist of components which can be created, interconnected and destroyed as the system evolves. Components exhibit hybrid behavior, consisting of continuous-time phases separated by discrete-event transitions. Components may evolve independently, or they may interact through their inputs, outputs and exported events. The interaction network itself may evolve.

The SHIFT programming language for dynamic networks of hybrid automata

SHIFT is a programming language for describing and simulating dynamic networks of hybrid automata. Such systems consist of components which can be created, interconnected, and destroyed as the system evolves. Components exhibit hybrid behavior, e.g. continuous-time phases separated by instantaneous discrete-event transitions. Components may evolve independently, or they may interact through selected state variables and events. The interaction network itself may evolve. The SHIFT model and language were motivated by our need for tools that support dynamically reconfigurable hybrid systems. Our primary application is the specification and analysis of different designs for automatic control of vehicles and highway systems. From our previous experience in modeling, analysis, and implementation, we adopted the hybrid systems approach for modeling the system components. Since spatial relationships between vehicles change as they move, our application is characterized by a dynamically changing network of interactions between system components. SHIFT has also since been used in coordinated autonomous submarines, air traffic control systems, and material handling systems. We examine other work related to the SHIFT approach. In we describe the main features of the SHIFT language-states, inputs, outputs, differential equations, and algebraic definitions, discrete states, and state transitions. We give a simplified version of the SHIFT model. We discuss the models of a type, a component, and the world and give the formal semantics of the model.

Discretization of timed automata

We construct two discretizations of dense time automata which generate the same untimed language as the dense time automata.<<ETX>>

Design and evaluation tools for automated highway systems

In this paper, the authors present a brief description of the California Partners for Advanced Transit and Highways (PATH) hierarchical control architecture for Automated Highway Systems (AHS). They describe the framework for AHS design and evaluation and give a summary of simulation and analysis tool needs. Some of the tools being developed which are based on the hybrid systems approach are also described.

A simulation environment for the coordinated operation of multiple autonomous underwater vehicles

A simulation environment of the coordinated operation of multiple Autonomous Underwater Vehicles (AUVs) is presented. The primary application of this simulation environment is the specification and analysis of an innovative approach to coastal oceanography based on the Generalized Vehicle [GV] concept. A Generalized Vehicle is a group of vehicles whose spatial and logic organization is coordinated in such a way that the group behaves as a single entity. The simulation environment was developed in Shift, a new specification language for describing dynamic networks of hybrid automata. These constitute the most adequate modeling formalism for this problem domain. The expressive power of Shift provides a compact notation for modeling spatial and logical relationships in a dynamic environment and for modeling and analyzing control strategies governing object interactions.

SmartAHS: A simulation framework for automated vehicles and highway systems

SmartAHS is a software framework for the uniform specification, simulation, and objective evaluation of Intelligent Vehicle Highway System (IVHS) alternatives. This paper illustrates the use of the object-oriented paradigm in its design, implementation, and use. Objective comparison of proposed highway automation alternatives is achieved, when all control architectures are specified in SmartAHS. The framework implementation is decomposed into three layers. A core set of entities, called SmartDb, implement the base classes of the framework, the scheduling mechanism, and a special syntax for a state machine formalism. The second layer, SmartAHS customizes these classes and implements entities specific to highway automation. The control and communication engineers are the users of SmartAHS; they further customize it to implement specific simulation applications such as SmartPATH. The users of the applications are system analysts and system planners. We discuss the design and implementation of SmartDb and SmartAHS and give a use-case example of a subset of SmartPATH.

SmartDb: an object-oriented simulation framework for intelligent vehicles and highway systems

SmartDB is a framework for the uniform specification, simulation, optimization, evaluation, and implementation of intelligent vehicle highway system (IVHS) alternatives. The salient concepts in SmartDB are: (1) layered control architecture, (2) coordination of distributed control agents through communication, (3) combined discrete and continuous dynamical systems, known as hybrid systems, and their control and verification, (4) object oriented simulation, and (5) distributed and open architecture. This paper summarizes the first three concepts and describes in detail the simulation constructs and the distributed and open architecture of SmartDB.<<ETX>>

Object-oriented design of automated highway simulations using the SHIFT programming language

SmartAHS is a specification, simulation, and evaluation framework for modeling, control and evaluation of automated highway systems (AHS). SmartAHS is developed using SHIFT, a new programming language with simulation semantics. This paper discusses the requirements that have led to the development of SmartAHS and SHIFT, summarizes the main characteristics of the SHIFT language, and illustrates how the object-oriented features of SHIFT are used in the development of the SmartAHS framework.

Object Management Systems 1

Abstract We describe a new approach for developing large-scale object-oriented software systems, which we call Object Management Systems (OMS). OMS are model-based distributed applications used for managing complex physical environments. The management functions supported by OMS are configuration, fault, performance, accounting, access and security, resource, and planning management. The OMS Tool Set consists of a semantic data and process model called the OMS object model, the SmartDB software platform, customized extensions of SmartDB-SmartNet, SmartPower, and SmartAHS-for specific application domains, and the OMS Software Engineering process. The OMS-based development process consists of three stages: domain customization, system architecture, and application programming. Each stage produces specifications and implementations in software integrated around the OMS Tool Set. This software development life-cycle reduces project risk, budget, and schedule.