The synergies of the cyberworld and the physical world are manifest in networked control: the interconnection of sensors, actuators, and controllers enables us to monitor and affect local and remote physical environments. The network adds a new dimension to the feedback-loop abstraction and its applications are far-reaching, including our contributions to industrial automation, distributed instrumentation, remote diagnostics, smart homes, and distributed simulations. Other applications are expected in the areas of surveillance in remote and hazardous areas, space exploration, intelligent vehicles (e.g., UAVs, smart battleships), medical sensors, and surgical simulations. However, current networks introduce unreliable levels of service that adversely influence stability, performance, safety, and security.
Our projects at Case are enabling effective networked control in the current and future technological landscape.
Wireless Sensor Platform for Harsh Environments: Low-power and robust, wireless microsensors are required for applications demanding unobtrusive sensing in harsh operating conditions, e.g. high-temperature and mechanically/chemically active environments. Such conditions are common to automotive, aerospace, and geothermal industries; in-vivo tissue and blood sensing for health monitoring and treatment; and in-situ monitoring of liquids and gasses for contamination control and security. In this work, electronic circuits are being devised to 1) acquire signals from microsensors operating in a harsh environment, and 2) communicate those signals wirelessly to a host computer that operates in a benign environment. The interface circuitry is being implemented as an integrated circuit, approximately 2-mm square, that incorporates a low-noise, transimpedance pre-amplifier; a sigma-delta converter; and a low-power transmitter based on frequency shift keying suitable for maximum distances of about 1 meter. The integrated circuit has been designed and fabricated using silicon-on-insulator technology, which is appropriate for high-temperature (~300°C) and high-radiation environments. In this presentation, the design and recent test results of the first prototype, including the transimpedance amplifier, sigma-delta converter and transmitter circuits, are presented. The amplifier has a transimpedance input stage following by a voltage amplifier stage to provide a gain-bandwidth of about 8 MegOhms by 1.2 MHz, and functions for temperatures > 300°C. The sigma-delta converter provides SNR greater than 40 dB for temperatures for temperatures up to 250°C. The FSK transmitter uses a germanium tunnel diode to provide negative resistance, a planar loop inductor/antenna, and an MOS varactor to modulate the 27-MHz carrier frequency. Room-temperature test results show that the transmitter is functional for temperatures of at least 150°C. Work continues to identify and improve the temperature limit.
Diagnostics and Prognostics: Sensor and Algorithm for Health Monitoring in Industrial Systems: An interdisciplinary research effort involves the development of novel sensing systems in combination with advanced signal processing and estimation algorithms for real-time health monitoring in industrial systems. The major thrust of the work has been for the detection, diagnosis, and prognosis of faults in rotating machinery.
Networked control: Co-design: Feedback control systems wherein the control loops are closed through a real-time network are called networked control systems (NCSs). The insertion of the communication network in the feedback control loop makes the analysis and design of an NCS complex. Driving our research effort into NCSs is the point of view that the design of both the communication protocols and the interacting controlled system should not be treated as separate. In the co-design approach we have pioneered, network issues such as bandwidth, quantization, scalability, survivability, reliability, heterogeneity, and message delay are considered simultaneously with controlled system issues such as stability, performance, fault tolerance, and adaptability. We will summarize our NCS framework and our research in developing co-design tools for NCS stability, NCS scheduling, and co-simulation.
Software Engineering: Middleware and Agents: The development of networked control software presents challenges due to its complexity and real-time constraints. Networked control software can be critically aided by the adoption of real-time protocols and of middleware components for resource discovery and security. Furthermore, agent-based software enabled us to achieve unprecedented levels of flexibility, such as an elegant conceptual framework for evolvability, survivability, and multi-unit cooperation.
Security: Post-deployment Validation: The practice of security necessitates tools for monitoring the health of a system and for recovering from potential vulnerabilities. In particular, operators must remain vigilant for known threats as well as for novel and unanticipated attacks. We are developing tools for capturing and auditing executions of critical networked services. The technical approach involves the online capture of software executions, its offline replay, and the analysis of resulting executions through data mining and statistical visualization techniques in order to guide the manual search for system vulnerabilities.
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