William Emfinger

A software platform for fractionated spacecraft

A fractionated spacecraft is a cluster of independent modules that interact wirelessly to maintain cluster flight and realize the functions usually performed by a monolithic satellite. This spacecraft architecture poses novel software challenges because the hardware platform is inherently distributed, with highly fluctuating connectivity among the modules. It is critical for mission success to support autonomous fault management and to satisfy real-time performance requirements. It is also both critical and challenging to support multiple organizations and users whose diverse software applications have changing demands for computational and communication resources, while operating on different levels and in separate domains of security. The solution proposed in this paper is based on a layered architecture consisting of a novel operating system, a middleware layer, and component-structured applications. The operating system provides primitives for concurrency, synchronization, and secure information flows; it also enforces application separation and resource management policies. The middleware provides higher-level services supporting request/response and publish/subscribe interactions for distributed software. The component model facilitates the creation of software applications from modular and reusable components that are deployed in the distributed system and interact only through well-defined mechanisms. Two cross-cutting aspects - multi-level security and multi-layered fault management - are addressed at all levels of the architecture. The complexity of creating applications and performing system integration is mitigated through the use of a domain-specific model-driven development process that relies on a dedicated modeling language and its accompanying graphical modeling tools, software generators for synthesizing infrastructure code, and the extensive use of model-based analysis for verification and validation.

Distributed Real-Time Managed Systems: A Model-Driven Distributed Secure Information Architecture Platform for Managed Embedded Systems

Architecting software for a cloud computing platform built from mobile embedded devices incurs many challenges that arent present in traditional cloud computing. Both effectively managing constrained resources and isolating applications without adverse performance effects are needed. A practical design- and runtime solution incorporates modern software development practices and technologies along with novel approaches to address these challenges. The patterns and principles manifested in this system can potentially serve as guidelines for current and future practitioners in this field.

Achieving resilience in distributed software systems via self-reconfiguration

We describe resilient operation of cyber-physical application platforms.We describe implicit design-time encoding of the reconfiguration.We describe design-time analysis and validation tools for these systems. Improvements in mobile networking combined with the ubiquitous availability and adoption of low-cost development boards have enabled the vision of mobile platforms of Cyber-Physical Systems (CPS), such as fractionated spacecraft and UAV swarms. Computation and communication resources, sensors, and actuators that are shared among different applications characterize these systems. The cyber-physical nature of these systems means that physical environments can affect both the resource availability and software applications that depend on resource availability. While many application development and management challenges associated with such systems have been described in existing literature, resilient operation and execution have received less attention. This paper describes our work on improving runtime support for resilience in mobile CPS, with a special focus on our runtime infrastructure that provides autonomous resilience via self-reconfiguration. We also describe the interplay between this runtime infrastructure and our design-time tools, as the later is used to statically determine the resilience properties of the former. Finally, we present a use case study to demonstrate and evaluate our design-time resilience analysis and runtime self-reconfiguration infrastructure.

Analysis, verification, and management toolsuite for cyber-physical applications on time-varying networks

Cyber-Physical Systems (CPS) are increasingly utilizing advances in wireless mesh networking among computing nodes to facilitate communication and control for distributed applications. Factors such as interference or node mobility cause such wireless networks to experience changes in both topology and link capacities. These dynamic networks pose a reliability concern for high-criticality or mixed-criticality systems which require strict guarantees about system performance and robustness prior to deployment. To address the design- and run-time verification and reliability concerns created by these dynamic networks, we are developing an integrated modeling, analysis, and run-time toolsuite which provides (1) network profiles that model the dynamics of system network resources and application network requirements over time, (2) design-time verification of application performance on dynamic networks, and (3) management of the CPS network resources during run-time. In this paper we present the foundations for the analysis of dynamic networks and show experimental validations of this analysis. We conclude with a focus on future work and applications to the field.

A testbed to simulate and analyze resilient cyber-physical systems

This paper describes a testbed for development, deployment, testing, and analysis of Cyber-Physical Systems (CPS) applications. The testbed incorporates smart network hardware, allowing high-fidelity emulation of CPS network characteristics, and CPS simulation environments to enable high-frequency sensor reading, actuator control and physical environmental changes. We discuss the architecture of this testbed and present the types of experiments and applications which can be run to study hardware and software fault tolerance, software reconfiguration, and system stability characteristics in distributed real-time embedded systems. We also describe the scalability, limitations, and potential extensions to this testbed.

DREMS ML

Complex sensing, processing and control applications running on distributed platforms are difficult to design, develop, analyze, integrate, deploy and operate, especially if resource constraints, fault tolerance and security issues are to be addressed. While technology exists today for engineering distributed, real-time component-based applications, many problems remain unsolved by existing tools. Model-driven development techniques are powerful, but there are very few existing and complete tool chains that offer an end-to-end solution to developers, from design to deployment. There is a need for an integrated model-driven development environment that addresses all phases of application lifecycle including design, development, verification, analysis, integration, deployment, operation and maintenance, with supporting automation in every phase. Arguably, a centerpiece of such a model-driven environment is the modeling language. To that end, this paper presents a wide-spectrum architecture design language called DREMS ML that itself is an integrated collection of individual domain-specific sub-languages. We claim that the language promotes correct-by-construction software development and integration by supporting each individual phase of the application lifecycle. Using a case study, we demonstrate how the design of DREMS ML impacts the development of embedded systems. We describe an architecture design language for distributed platforms.We describe a software component model for complex, distributed applications.We describe how all implementation and deployment artifacts can be generated.Our language supports design, development, analysis, deployment and maintenance.

Demo Abstract: SURE: An Experimentation and Evaluation Testbed for CPS Security and Resilience

In-depth consideration and evaluation of security and resilience is necessary for developing the scientific foundations and technology of Cyber-Physical Systems (CPS). In this demonstration, we present SURE [1], a CPS experimentation and evaluation testbed for security and resilience focusing on transportation networks. The testbed includes (1) a heterogeneous modeling and simulation integration platform, (2) a Web-based tool for modeling CPS in adversarial environments, and (3) a framework for evaluating resilience using attacker-defender games. Users such as CPS designers and operators can interact with the testbed to evaluate monitoring and control schemes that include sensor placement and traffic signal configuration.

ROSMOD: a toolsuite for modeling, generating, deploying, and managing distributed real-time component-based software using ROS

This paper presents ROSMOD, a model-driven component-based development tool suite for the Robot Operating System (ROS). ROSMOD is well suited for the design, development and deployment of large scale distributed applications on embedded hardware devices. We present the various features of ROSMOD including the modeling language, the graphical user interface, code generators and deployment infrastructure. We describe the utility of this tool with a real-world case study - An Autonomous Ground Support Equipment (AGSE) robot that was designed and prototyped using ROSMOD for the NASA Student Launch competition, 2014-2015.

Demo Abstract: RIAPS — A Resilient Information Architecture Platform for Edge Computing

The emerging CPS/IoT ecosystem platforms such as Beaglebone Black, Raspberry Pi, Intel Edison and other edge devices such as SCALE, Paradrop are providing new capabilities for data collection, analysis and processing at the edge (also referred to as Fog Computing). This allows the dynamic composition of computing and communication networks that can be used to monitor and control the physical phenomena closer to the physical system. However, there are still a number of challenges that exist and must be resolved before we see wider applicability of these platforms for applications in safety-critical application domains such as Smart Grid and Traffic Control.

Modeling Network Medium Access Protocols for Network Quality of Service Analysis

Design-time analysis and verification of distributed real-time embedded systems necessitates the modeling of the time-varying performance of the network and comparing that to application requirements. Earlier work has shown how to build a system network model that abstracted away the networks physical medium and protocols which govern its access and multiplexing. In this work we show how to apply a network medium channel access protocol, such as Time-Division Multiple Access (TDMA), to our network analysis methods and use the results to show that the abstracted model without the explicit model of the protocol is valid.