Physically Asynchronous Logically Synchronous Architecture

In networked cyber-physical systems, real time global computations require consistent views, consistent actions, and synchronized state transitions across network nodes. However, the convergence of sensing, control, communication and coordination in cyber-physical systems (CPS) such as modern airplanes, power grid, train and medical device networks poses enormous challenges. 

Computer science researchers at the University of Illinois, led by Professors Lui Sha and Jose Meseguer, are developing formal complexity reduction architecture patterns aimed at addressing these challenges. The team has developed the Physically Asynchronous Logically Synchronous (PALS) architecture pattern that supports real time global computation.  The objective of the PALS protocol is to provide the optimal real time logical (virtual) synchronization protocol.

The groups are working in collaboration with industry and research partners Rockwell Collins Inc., Lockheed Martin Corporation, Software Engineering Institute, and the University of Oslo. Researchers and engineers of Rockwell Collins Inc., in cooperation with Illinois computer science researchers, led the study on the implementation of PALS for an Integrated Modular Avionics application.  The results showed that PALS reduced verification time from 35 hours to less than 30 seconds as compared with traditional design in a dual redundant flight guidance system prototype.  This PALS study, authored by Steven P. Miller, Darren D. Cofer, Lui Sha, Jose Meseguer and Abdullah Al-Nayeem, won the David Lubkowski Award for the Advancement Digital Avionics.

AADL is an open standard architecture analysis and description language supported by the avionics community.   Because of this remarkable success in complexity reduction, Illinois researchers, in cooperation with Software Engineering Institute and University of Oslo, are now working on a special AADL Annex called Synchronous AADL to support PALS based designs.  In addition, Illinois researchers, led by Dr. Cheolgi Kim, in cooperation with Lockheed Martin, are developing a production quality implementation of PALS library.