Middleware and control of cyber-physical systems: temporal guarantees and hybrid system analysis

摘要

A cyber-physical system is a system which encompasses computing, communication, and physical entities with emphasis on their interactions. In this work, we study two different aspects of cyber-physical systems: mechanisms as well as policy. At the mechanism end we study how to provide a platform for developing cyber-physical systems, and at the policy end we study how to analyze the performance of the overall control system.For the purpose of verification of certain high-level properties, a cyber-physical system can be viewed as a hybrid system. It is indeed useful to do so since properties such as safety can then be studied through a reachable set computation. Towards this end, we propose a theory for an over-approximation of the reachable set for a special class of hybrid systems, over a finite time interval, under a certain deterministic and transversal discrete transition condition. A prototype software tool based on the proposed theory is also implemented and used to demonstrate the computation of such an over-approximate reachable set.At the mechanism end, we address the issue of the design and implementation of real-time mechanisms in Etherware, a middleware developed in the Information Technology Convergence Laboratory at the University of Illinois, so that it can be more suitable for networked control applications. Cyber-physical systems are often safety critical, and so it is important that their performance be predictable. Of particular interest is temporal predictability of interactions, which it is the goal of the middleware to ensure. Also of importance for developing complex control systems is that the middleware be flexible. We address the problem of enhancing these two attributes, and demonstrate the flexibility and temporal predictability of the enhanced Etherware through a networked inverted pendulum application.