It's common in controller design to assume that the controller reads the sensors and writes to the actuators at the same time instant. This assumption is often violated in practice because the controller executes its code sequentially on a microprocessor. If the microprocessor is "fast enough," often the controller will still work. However, if the sensing and control are done by two different devices that must communicate across a network, the resulting timing uncertainty due to network delays and clock offsets will often destabilize the controller.
This poster presents the Pulsar platform, which can achieve better than 5 nanosecond clock synchronization in an indoor environment combining wireless ultra-wideband communication with a chip-scale atomic clock. We discuss the various challenges in synchronization at nanosecond scales then propose and evaluate a proof-of-concept protocol for the same.
FORCES is designed to help protect the nation's critical infrastructure from attack and to ensure its robust, secure and efficient operation. Specifically, FORCES aims to increase the resilience of large-scale networked cyber-physical systems (CPS) in the key areas of energy delivery, transportation, and energy management in buildings.
The main goal of this project is to lay down the foundations of a novel approach based on opportunistic statetriggered aperiodic control for networked cyberphysical systems that leverages their cooperative nature. Most networked controllers are not implementable over embedded digital computer systems because they rely on continuous time or synchronous executions that are costly to enforce.
Automotive applications require an exceptionally high level of confidence. For instance, the faulty ignition switches in General Motors vehicles have resulted in 52 crashes and at least 2.6 million vehicles with these switches have been recalled. If each vehicle spent only 1,000 hours on the road, there has been less than 1 crash every 5 x 107 hours of operation. Test tracks and simulations are unable to reliably detect failures that occur this infrequently.
Commodity operating systems manage time in a best effort fashion, where clock synchronization is performed independently of both application demand and resource constraints. The vision of the RoseLine project is to develop a Quality of Time (QoT) stack for Linux that enables developers to write distributed applications that perform computation with a common sense of time.
Existing platforms are built with a static network connecting microprocessor, radio, clock system, and other components. This static configuration prevents researchers from experimentally validating the trade-offs between the way that clocks are conditioned and distributed, and the performance of the embedded system. In particular, such design decisions have major impact on time synchronization.
