Jonathan Sprinkle

Smart Dust: communicating with a cubic-millimeter computer

W hat do Rational Rose, Simulink, and LabVIEW have in common? At first, these tools seem very different. Rational Rose (http://www.rational.com) is a visual modeling tool, Simulink (http:// www.mathworks.com) is a hierarchical block-diagram design and simulation tool, and LabVIEW (http:// www.ni.com) is a graphical programming development environment. Despite the different terminology, these three tools share a common underlying theme: Each is an integrated set of modeling, model analysis, simulation, and code-generation tools that help design and implement computer-based systems (CBSs) in a specific, well-defined engineering field. These tools and other popular domain-specific integrated development environments can help capture specifications in the form of domain models. They also support the design process by automating analysis and simulating essential system behavior. In addition, they can automatically generate, configure, and integrate target application components. These environments translate the verified design—expressed in a domainspecific, primarily graphical modeling formalism—into a variety of artifacts that constitute a CBS implementation. These artifacts can include glue code, database schema, and configuration tables. These tools use domain-specific modeling languages that allow developers to represent essential design views and to both formally express and automatically enforce integrity constraints. These tools also support model composition that is synergistic with the design process in the particular engineering domain. Other benefits include having integrated models as opposed to relying merely on source code. In addition, the common input—that is, the shared design model—guarantees the consistency of different analysis results as long as all of the applied generators are correct. While the industry understands the welldocumented benefits of domain-specific, integrated modeling, analysis, and application-generation environments, their high cost represents a significant block to wide acceptance and application. Consequently, these tools are available only for domains with large markets in which high volume offsets the substantial initial investment cost. For CBSs in smaller, specialized domains, or even for single projects, the industry needs technology that can help rapidly and efficiently compose these environments from reusable components.Domain-specific integrated development environments can help capture specifications in the form of domain models. These tools support the design process by automating analysis and simulating essential system behavior. In addition, they can automatically generate, configure, and integrate target application components. The high cost of developing domain-specific, integrated modeling, analysis, and application-generation environments prevents their penetration into narrower engineering fields that have limited user bases. Model-integrated computing (MIC), an approach to model-based engineering that helps compose domain-specific design environments rapidly and cost effectively, is particularly relevant for specialized computer-based systems domains-perhaps even single projects. The authors describe how MIC provides a way to compose such environments cost effectively and rapidly by using a metalevel architecture to specify the domain-specific modeling language and integrity constraints. They also discuss the toolset that implements MIC and describe a practical application in which using the technology in a tool environment for the process industry led to significant reductions in development and maintenance costs.

A domain-specific visual language for domain model evolution

Abstract Domain-specific visual languages (DSVLs) are concise and useful tools that allow the rapid development of the behavior and/or structure of applications in well-defined domains. These languages are typically developed specifically for a domain, and have a strong cohesion to the domain concepts, which often appear as primitives in the language. The strong cohesion between DSVL language primitives and the domain is a benefit for development by domain experts, but can be a drawback when the domain evolves—even when that evolution appears to be insignificant. This paper presents a domain-specific visual language developed expressly for the evolution of domain-specific visual languages, and uses concepts from graph rewriting to specify and carry out the transformation of the models built using the original DSVL.

Guest Editors' Introduction: What Kinds of Nails Need a Domain-Specific Hammer?

Domain-specific techniques, languages, tools, and models, such as Fortran and Cobol can easily be viewed as domain-specific languages for scientific and business computing, respectively. Their domain is just very wide. What has changed is the technology for creating domain-specific languages (DSLs). Now it is easier to define languages and get tool support for narrower domains. Such focus offers increased abstraction, making development faster and easier. In domain-specific approaches, developers construct solutions from concepts representing things in the problem domain, not concepts of a given general-purpose programming language. Ideally, a DSL follows the domain abstractions and semantics as closely as possible, letting developers perceive themselves as working directly with domain concepts. The created specifications might then represent simultaneously the design, implementation, and documentation of the system, which can be generated directly from them. The mapping from the high-level domain concepts to implementation is possible because of the domain specificity: the language and code generators fit the requirements of a narrowly defined domain.

Information Technology for Assisted Living at Home: building a wireless infrastructure for assisted living

A heterogeneous wireless network to support a home health system is presented. This system integrates a set of smart sensors which are designed to provide health and security to the elder citizen living at home. The system facilitates privacy by performing local computation, it supports heterogeneous devices and it provides a platform and initial architecture for exploring the use of sensors with elderly people in the Information Technology for Assisted Living and Home project. The goal of this project is to provide alerts to care givers in the event of an accident or acute illness, and enable remote monitoring by authorized and authenticated care givers

Encoding aerial pursuit/evasion games with fixed wing aircraft into a nonlinear model predictive tracking controller

Unmanned aerial vehicles (UAVs) have shown themselves to be highly capable in intelligence gathering, as well as a possible future deployment platform for munitions. Currently UAVs are supervised or piloted remotely, meaning that their behavior is not autonomous throughout the flight. For uncontested missions this is a viable method; however, if confronted by an adversary, UAVs may be required to execute maneuvers faster than a remote pilot could perform them in order to evade being targeted. In this paper we give a description of a nonlinear model predictive controller in which evasive maneuvers in three dimensions are encoded for a fixed wing UAV for the purposes of this pursuit/evasion game.

Reachability calculations for automated aerial refueling

This paper describes Hamilton-Jacobi (HJ) reachability calculations for a hybrid systems formalism governing unmanned aerial vehicles (UAVs) interacting with another vehicle in a safety-critical situation. We use this problem to lay the foundations toward the goal of refining or designing protocols for multi-UAV and/or manned vehicle interaction. We describe here what mathematical foundations are necessary to formulate verification problems on reachability and safety of flight maneuvers. We finally show how this formalism can be used in the chosen application to inform UAV decisions on avoiding unsafe scenarios while achieving mission objectives.

Implementing and testing a nonlinear model predictive tracking controller for aerial pursuit/evasion games on a fixed wing aircraft

Flight test and simulation results are presented for a nonlinear model predictive tracking controller (NMPC) used in pursuit and evasion maneuvers in three dimensions on a fixed wing unmanned aerial vehicle (UAV) for the purposes of pursuit/evasion games (PEGs) against a piloted F-15 aircraft. These controllers are shown to be effective for both asymmetric and symmetric PEGs. While the capability of UAVs to perform autonomously has not yet been demonstrated, this is an important step to enable at least limited autonomy in such aircraft to operate with temporary loss of remote control, or when confronted with an adversary or obstacles for which remote control is insufficient. Such capabilities have been under development in the software enabled control (SEC) program and were recently tested in the capstone demonstration of that program.

The new metamodeling generation

Model integrated computing (MIC) is an effective and efficient method for developing, maintaining, and evolving large-scale, domain-specific software applications for computer-based systems (CBSs). On a higher level, it is possible to use MIC to develop, maintain, and evolve the meta-level tools (metamodeling environments) themselves, by modeling the metamodeling environment (meta-metamodeling). This paper documents the evolution of one metamodeling environment into another: specifically the design choices of the newer metamodeling environment with regard to the old one, and the solutions to problems that were introduced with the change.

Switched and Symmetric Pursuit/Evasion Games Using Online Model Predictive Control With Application to Autonomous Aircraft

This paper describes a supervisory controller for pursuit and evasion of two fixed-wing autonomous aircraft. Novel contributions of the work include the real-time use of model-predictive control, specifically nonlinear model predictive tracking control, for predictions of the vehicle under control, as well as predictions for the adversarial aircraft. In addition to this inclusion, the evasive controller is a hybrid system, providing switching criteria to change modes to become a pursuer based on the current and future state of the vehicle under control, and that of the adversarial aircraft. Results of the controller for equally matched platforms in actual flight tests against a US Air Force trained F-15 test pilot are given. Extensive simulation analysis of the symmetric games is provided, including regressive analysis based on initial conditions of height advantage, and relative velocity vectors, and in particular the effect of allowing the evading aircraft to switch modes between “evader” and “pursuer” during the game.

Model-based design: a report from the trenches of the DARPA Urban Challenge

The impact of model-based design on the software engineering community is impressive, and recent research in model transformations, and elegant behavioral specifications of systems has the potential to revolutionize the way in which systems are designed. Such techniques aim to raise the level of abstraction at which systems are specified, to remove the burden of producing application-specific programs with general-purpose programming. For complex real-time systems, however, the impact of model-driven approaches is not nearly so widespread. In this paper, we present a perspective of model-based design researchers who joined with software experts in robotics to enter the DARPA Urban Challenge, and to what extent model-based design techniques were used. Further, we speculate on why, according to our experience and the testimonies of many teams, the full promises of model-based design were not widely realized for the competition. Finally, we present some thoughts for the future of model-based design in complex systems such as these, and what advancements in modeling are needed to motivate small-scale projects to use model-based design in these domains.