Design and experimental verification of real-time mechanisms for middleware for networked control

Networked control systems give rise to several new problems which need to be resolved for successful development of such control systems. One of the most important is to develop a software framework with appropriate architecture and mechanisms for rapid, reliable, and evolvable distributed control applications. In particular, timeliness in the interaction among entities which constitute the overall control loop is one of the crucial requirements that must be provided by the platform. We discuss the issues related to the design and implementation of such mechanisms to support timeliness requirements. We describe the design of real-time enhancements to Etherware, a middleware for distributed control systems that has been developed in the Information Technology Convergence Laboratory at the University of Illinois. We further evaluate the performance of the designed middleware through a distributed inverted pendulum control application. We demonstrate the satisfactory performance of the unstable system even under several sophisticated run-time functionalities such as component upgrade and migration. We demonstrate that stability is maintained even under each of these tests as well as a computational stress test.