Transparent contention buses can improve architectures

Abstract

Advanced avionic architectures are becoming increasingly complex in their needs for internal communications. Larger numbers of computers and other electronic devices are used, each exchanging more data at higher rates. Simultaneously, there are demands to make avionic systems more robust and fault tolerant. All of the electronic systems on aircraft now require interconnection, including mission management, sensor management, flight controls, secure-data, and aircraft utility systems. Each system has unique requirements; yet, for the most efficient system, all of them must communicate to exchange command and status data. These new system demands require modifications in the total system architecture, and particularly in the communications structure. This paper discusses some of the unique architectural aspects of the integration of new systems on aircraft. The paper also describes a data channel approach that meets the diverse and unique requirements of modern avionics. The approach is called Token Passing with Transparent Contention and combines a token passing approach for normal operation with a transparent contention approach to handle power-up and bus reconfiguration. The protocol can be used equally well with coaxial cable, fiber optics, or mixed media systems. It provides true distributed control and easily and rapidly overcomes problems due to lost tokens or newly added terminals. Further, it allows a single bus to be dynamically divided into independently operating subnets and supports their smooth re-integration into a single network. Architecture Requirements Advanced aircraft are required to support increasingly stringent mission demands. Aircraft are required to deliver their weapons more precisely and with shorter reaction times. This precise and timely delivery is required while the aircraft is maneuvering and/or after reduced available time for target recognition, location, and identification. For maximum total force effectiveness, each aircraft is required to maintain coordination with other friendly forces and to take advantage of information that can be gathered from enemy forces. To obtain maximum mission effectiveness, each aircraft must also be highly reliable and provide high capability for mission completion regardless of the failure of equipments. Once on the ground, the aircraft must be easily fixed, requiring a minimum of ground support. All of this must be provided within reasonable costs and with minimum weight and power requirements to allow procurement of large numbers of aircraft that can accomplish long range missions. The increasing mission demands require avionic system architectural changes. Figure 1 graphically illustrates some of the Air Force Wright Aeronautical Laboratories' (AFWAL) programs that are designed to provide these necessary improvements in avionics. As shown, the required changes are pervasive, affecting software, pilot-vehicle interfaces, and hardware throughout the system. The new architectures and technologies involve increasingly high levels of integration in the core system. Functions that will be added include artificial intelligence, reconfiguration managerrent, and self-testlbuilt-in-testlintegrated-maintenance. Further, the new architectures must extend into the front end of the system, addressing high-speed converters and processors, active aperture antennae, generic front-end designs, and adaptive multifunction antennae. These new approaches will require standardization and integrity management in more system elements, including defensive systems, flight control systems, propulsion systems, power systems, and communication systems. PAVE PILLAR: URR, INEWS, IIRA, IRST, 1750, CSP, AAAM, --Next Step in Avionics Evolution A V I O N I C SYSTEM INCLUDING