Matthew J. Rutherford

A routing scheme for content-based networking

This work proposes a routing scheme for content-based networking. A content-based network is a communication network that features a new advanced communication model where messages are not given explicit destination addresses, and where the destinations of a message are determined by matching the content of the message against selection predicates declared by nodes. Routing in a content-based network amounts to propagating predicates and the necessary topological information in order to maintain loop-free and possibly minimal forwarding paths for messages. The routing scheme we propose uses a combination of a traditional broadcast protocol and a content-based routing protocol. We present the combined scheme and its requirements over the broadcast protocol. We then detail the content-based routing protocol, highlighting a set of optimization heuristics. We also present the results of our evaluation, showing that this routing scheme is effective and scalable.

The impact of Electric Vehicle battery charging on distribution transformers

Electric Vehicles (EV) and Plug-in Hybrid Electric Vehicles (PHEV) have a limited share of the current market. However, it is widely expected that the situation will change in the near future and the penetration of battery-operated vehicles will increase significantly. This paper addresses the impact of the mass operation and electricity consumption of EVs and PHEVs on the distribution utility and more specifically on distribution transformers. The charging effect of various types of EV batteries on the life of distribution transformers is analyzed. A typical annual base-load on the distribution transformer is considered and compared with different battery charging load scenarios. Simulation results show that distributing the load profile of the battery charging helps to decrease the distribution transformer loss of life. In addition, power management of the EV and PHEV battery charging and the interface with the Smart-Grid is explained.

Reconfiguration in the Enterprise JavaBean Component Model

Reconfiguration is the process of applying planned changes to the communication, interconnection, componentization, or functionality of a deployed system. It is a powerful tool for achieving a variety of desirable properties of large-scale, distributed systems, including evolvability, adaptability, survivability, and continuous availability. Current approaches to reconfiguration are inadequate: some allow one to describe a systems range of configurations for a relatively broad class of system architectures, but do not provide a mechanism for actually carrying out a reconfiguration; others provide a mechanism for carrying out certain kinds of limited reconfigurations, but assume a specialized system architecture in order to do so. This paper describes our attempt at devising a reconfiguration mechanism for use with the popular and widely available Enterprise JavaBean (EJB) component container model. We describe extensions to the basic services provided by EJB to support the mechanism, a prototype implementation, and a case study of its application to a representative component-based distributed system.

Radar-based detection and identification for miniature air vehicles

It is claimed that Unmanned Aerial Vehicles (UAVs) used for civilian/public domain applications will be dominant in the near future. Compared to UAVs used by the military, civilian UAVs are often operated by pilots without formal training, and hence they require increased levels of autonomy and intelligence, especially with regard to reducing threats to public safety. UAV integration into the National Air Space will require that the UAVs support multiple, complementary sense-and-avoid mechanisms, including detection and identification of other UAV-sized targets. Currently, the majority of available sensors are based on infrared detectors, focal plane arrays, optical and ultrasonic rangefinders. These sensors are generally not able to detect or identify other UAV-sized targets and, when detection is possible, considerable computational power may be required for successful identification. By contrast, this paper describes the design of a light weight, X-Band (10.5GHz) radar system for use on a small-scale (< 25 kg) rotorcraft. The prototype radar implementation is small enough to be carried by any miniature UAV, and it is capable of differentiating other miniature rotorcraft by their doppler signature. In addition to the overall hardware and software design of the prototype system, a performance analysis of various signature matching algorithms is presented demonstrating the capabilities of the system in a laboratory setting.

Automating experimentation on distributed testbeds

Engineering distributed systems is a challenging activity. This is partly due to the intrinsic complexity of distributed systems, and partly due to the practical obstacles that developers face when evaluating and tuning their design and implementation decisions.This paper addresses the latter aspect, providing techniques for software engineers to automate the experimentation activity. Our approach is founded on a suite of models that characterize the distributed system under experimentation, the testbeds upon which the experiments are to be carried out, and the client behaviors that drive the experiments. The models are used by generative techniques to automate construction of the workloads,as well as construction of the scripts for deploying and executing the experiments on distributed testbeds. The framework is not targeted at a specific system or application model, but rather is a generic, programmable tool. We have validated our approach by performing experiments on a variety of distributed systems. For two of these systems, the experiments were deployed and executed on the PlanetLab wide-area testbed.Our experience shows that this framework can be readily applied to different kinds of distributed system architectures,and that using it for meaningful experimentation,especially in large-scale network environments, is advantageous.

A case for test-code generation in model-driven systems

A primary goal of generative programming and model-driven development is to raise the level of abstraction at which designers and developers interact with the software systems they are building. During initial development, the benefits of abstraction are clear. However, during testing and maintenance, increased distance from the implementation can be a disadvantage. We view test cases and test harnesses as an essential bridge between the high-level specifications and the implementation. As such, the generation of test cases for fully generated components and test harnesses for partially generated components is of fundamental importance to model-driven systems. In this paper we present our experience with test-case and test-harness generation for a family of model-driven, component-based distributed systems. We describe our development tool, MODEST, and motivate our decision to invest the extra effort needed to generate test code. We present our approach to test-case and test-harness generation and describe the benefits to developers and maintainers of generated systems. Furthermore, we quantify the relative cost of generating test code versus application code and find that the artifact templates for producing test code are simpler than those used for application code. Given the described benefits to developers and maintainers and the relatively low cost of test-code development, we argue that test-code generation should be a fundamental feature of model-driven development efforts.

Evaluating Test Suites and Adequacy Criteria Using Simulation-Based Models of Distributed Systems

Test adequacy criteria provide the engineer with guidance on how to populate test suites. While adequacy criteria have long been a focus of research, existing testing methods do not address many of the fundamental characteristics of distributed systems, such as distribution topology, communication failure, and timing. Furthermore, they do not provide the engineer with a means to evaluate the relative effectiveness of different criteria, nor the relative effectiveness of adequate test suites satisfying a given criterion. This paper makes three contributions to the development and use of test adequacy criteria for distributed systems: (1) a testing method based on discrete-event simulations; (2) a fault-based analysis technique for evaluating test suites and adequacy criteria; and (3) a series of case studies that validate the method and technique. The testing method uses a discrete-event simulation as an operational specification of a system, in which the behavioral effects of distribution are explicitly represented. Adequacy criteria and test cases are then defined in terms of this simulation-based specification. The fault-based analysis involves mutation of the simulation-based specification to provide a foil against which test suites and the criteria that formed them can be evaluated. Three distributed systems were used to validate the method and technique, including DNS, the domain name system.

Survey of Unmanned Helicopter Model-Based Navigation and Control Techniques

Unmanned Aircraft Systems(UAS) have seen unprecedented levels of growth during the last two decades. Although many challenges still exist, one of the main UAS focus research areas is in navigation and control. This paper provides a comprehensive overview of helicopter navigation and control, focusing specifically on small-scale traditional main/tail rotor configuration helicopters. Unique to this paper, is the emphasis placed on navigation/control methods, modeling techniques, loop architectures and structures, and implementations. A ‘reference template’ is presented and used to provide a basis for comparative studies and determine the capabilities and limitations of algorithms for unmanned/autonomous flight, as well as for navigation, and control. A detailed listing of related research is provided, which includes model structure, helicopter platform, control method and loop architecture, flight maneuvers and results for each. The results of this study was driven by and has led to the development of a ‘one-fits-all’ comprehensive and modular navigation controller and timing architecture applicable to any rotorcraft platform.

Implementation and Testing of a Backstepping Controller Autopilot for Fixed-wing UAVs

The ability of backstepping controllers to deal with nonlinearities make this technique a suitable candidate for the control of small fixed-wing Unmanned Aerial Vehicles (UAVs). The authors have already proposed a comprehensive approach combining backstepping with PID controllers for simultaneous longitudinal and latero-directional control of fixed-wing UAVs, achieving good performance even with considerable levels of signal noise Sartori et al (2013). In further detail, the ability of the mixed approach to control different size and configuration aircraft in the presence of parametric uncertainties or noise, and when implemented on a microcontroller board was demonstrated. The present paper illustrates integration and testing of the backstepping controller on a real unmanned aircraft. After a summarizing the adopted control design and strategy, initial software and hardware simulations validate the control action for the selected aircraft. The implementation of the microcontroller on the aircraft and the integration with other aircraft systems is also illustrated. Experimental results obtained for ground and flight tests are presented, validating the applicability of the backstepping controller.

ISLANDS: A Self-Leveling landing platform for autonomous miniature UAVs

The Intelligent Self-Leveling and Nodal Docking System (ISLANDS) is a mobile recharging/refueling station designed and built to enhance endurance and range of small-scale, autonomous, unmanned helicopters, which are becoming increasingly popular for a wide range of non-military applications such as, surveillance, reconnaissance, traffic monitoring, emergency response, agricultural spraying, and many other “eye in the sky” missions. The primary function of ISLANDS is to provide a safe, level landing platform for such helicopters. Additionally, in order to provide the maximum benefit in terms of increased range and flight-time, ISLANDS must be strategically located in the work field of the helicopter. In this paper, we discuss both the design of the individual ISLANDS “node,” and the use of ISLANDS within a larger systems context. At the node level, the mechanical subsystems implementing these ISLANDS are described. At the system level, we report on initial results tackling the ISLANDS placement problem with a genetic search algorithm. In combination, these contributions provide a complete solution to enable longer and more complex missions for small autonomous helicopters.