Scalable and Efficient Associative Processor Solution to Guarantee Real-Time Requirements for Air Traffic Control Systems

https://kent-islandora.s3.us-east-2.amazonaws.com/node/17407/87333-thumbnail.jpgThis paper proposes a solution to air traffic control (ATC) using an enhanced SIMD machine model called an Associative Processor (AP). Our solution differs from previous ATC systems that are designed for MIMD computers and have a great deal of difficulty meeting the predictability requirements for ATC, which are critical for meeting the strict certification standards required for safety critical software components. The proposed AP solution supports accurate predictions of worst case execution times and guarantees all deadlines are met. Furthermore, the software developed based on the AP model is much simpler and smaller in size than the current corresponding ATC software. As the associative processor is built from SIMD hardware, it is considerably cheaper and simpler than the MIMD hardware currently used to support ATC. We have designed a prototype for eight ATC real-time tasks on ClearSpeed CSX600 accelerator that is used to emulate AP. Performance is evaluated in terms of execution time and predictability and is compared to the fastest host-only version implemented using OpenMP on an 8core multiprocessor (MIMD). Our extensive experiments show that the AP implementation meets all deadlines that can be statically scheduled. To the contrary, some tasks miss their deadlines when implemented on MIMD. It is shown that the proposed AP solution will support accurate and meaningful predictions of worst case execution times and will guarantee that all deadlines are met.</p

Parallel processing and expert systems

Whether it be monitoring the thermal subsystem of Space Station Freedom, or controlling the navigation of the autonomous rover on Mars, NASA missions in the 1990s cannot enjoy an increased level of autonomy without the efficient implementation of expert systems. Merely increasing the computational speed of uniprocessors may not be able to guarantee that real-time demands are met for larger systems. Speedup via parallel processing must be pursued alongside the optimization of sequential implementations. Prototypes of parallel expert systems have been built at universities and industrial laboratories in the U.S. and Japan. The state-of-the-art research in progress related to parallel execution of expert systems is surveyed. The survey discusses multiprocessors for expert systems, parallel languages for symbolic computations, and mapping expert systems to multiprocessors. Results to date indicate that the parallelism achieved for these systems is small. The main reasons are (1) the body of knowledge applicable in any given situation and the amount of computation executed by each rule firing are small, (2) dividing the problem solving process into relatively independent partitions is difficult, and (3) implementation decisions that enable expert systems to be incrementally refined hamper compile-time optimization. In order to obtain greater speedups, data parallelism and application parallelism must be exploited

Optimizing construction of scheduled data flow graph for on-line testability

The objective of this work is to develop a new methodology for behavioural synthesis using a flow of synthesis, better suited to the scheduling of independent calculations and non-concurrent online testing. The traditional behavioural synthesis process can be defined as the compilation of an algorithmic specification into an architecture composed of a data path and a controller. This stream of synthesis generally involves scheduling, resource allocation, generation of the data path and controller synthesis. Experiments showed that optimization started at the high level synthesis improves the performance of the result, yet the current tools do not offer synthesis optimizations that from the RTL level. This justifies the development of an optimization methodology which takes effect from the behavioural specification and accompanying the synthesis process in its various stages. In this paper we propose the use of algebraic properties (commutativity, associativity and distributivity) to transform readable mathematical formulas of algorithmic specifications into mathematical formulas evaluated efficiently. This will effectively reduce the execution time of scheduling calculations and increase the possibilities of testability

Advanced flight control system study

The architecture, requirements, and system elements of an ultrareliable, advanced flight control system are described. The basic criteria are functional reliability of 10 to the minus 10 power/hour of flight and only 6 month scheduled maintenance. A distributed system architecture is described, including a multiplexed communication system, reliable bus controller, the use of skewed sensor arrays, and actuator interfaces. Test bed and flight evaluation program are proposed

Advantages and challenges of unmanned aerial vehicle autonomy in the Postheroic age

Over the past decade, unmanned aerial vehicles (UAVs) have revolutionized how the U.S. engages elusive militants in low-intensity conflicts by allowing the U.S. to project continuous military power without risking combat casualties. While UAV usage promises additional tactical advantages in future conflicts, little agreement exists regarding a strategic vision for UAV research and development, necessary for the U.S. to allocate limited resources among UAV development programs that address national security objectives. The present research makes the case for a future UAV technology evolutionary path leading to fully autonomous intelligence, surveillance, and reconnaissance (ISR)/strike UAV systems for the United States Air Force that are capable of sensing their environments through multiple modalities, recognizing patterns, and executing appropriate actions in response to their real-time analyses. The thesis addresses enabling technology inroads stemming from major improvements in our understanding of human neural circuitry that promise to enable innovations in the artificial intelligence needed to achieve autonomous system function. Arguments are based on projected military and economic benefits of autonomous systems and extend the historical model established by the CIA\u27s successful UAV program to unconventional warfare (UW) conflicts that the U.S. Air Force finds itself ill-equipped to handle. Counter-arguments are addressed relating to uncontrolled lethal technology, conflict initiation thresholds, and the vulnerability of overreliance on high-technology systems. In making the case for fully automated UAV technology, research provides a strategic future vision for autonomous UAV usage by highlighting the important interaction of artificial intelligence, “smart” wide-area sensors, and cooperative micro UAVs

NASA patent abstracts bibliography: A continuing bibliography. Section 1: Abstracts (supplement 39)

Abstracts are provided for 154 patents and patent applications entered into the NASA scientific and technical information systems during the period Jan. 1991 through Jun. 1991. Each entry consists of a citation, an abstract, and in most cases, a key illustration selected from the patent or patent application

A distributed agent architecture for real-time knowledge-based systems: Real-time expert systems project, phase 1

We propose a distributed agent architecture (DAA) that can support a variety of paradigms based on both traditional real-time computing and artificial intelligence. DAA consists of distributed agents that are classified into two categories: reactive and cognitive. Reactive agents can be implemented directly in Ada to meet hard real-time requirements and be deployed on on-board embedded processors. A traditional real-time computing methodology under consideration is the rate monotonic theory that can guarantee schedulability based on analytical methods. AI techniques under consideration for reactive agents are approximate or anytime reasoning that can be implemented using Bayesian belief networks as in Guardian. Cognitive agents are traditional expert systems that can be implemented in ART-Ada to meet soft real-time requirements. During the initial design of cognitive agents, it is critical to consider the migration path that would allow initial deployment on ground-based workstations with eventual deployment on on-board processors. ART-Ada technology enables this migration while Lisp-based technologies make it difficult if not impossible. In addition to reactive and cognitive agents, a meta-level agent would be needed to coordinate multiple agents and to provide meta-level control

A HEURISTIC CASCADING FUZZY LOGIC APPROACH TO REACTIVE NAVIGATION FOR UAV

ABSTRACT: The capability of navigating Unmanned Aerial Vehicles (UAVs) safely in unknown terrain offers huge potential for wider applications in non-segregated airspace. Flying in non-segregated airspace present a risk of collision with static obstacles (e.g., towers, power lines) and moving obstacles (e.g., aircraft, balloons). In this work, we propose a heuristic cascading fuzzy logic control strategy to solve for the Conflict Detection and Resolution (CD&R) problem, in which the control strategy is comprised of two cascading modules. The first one is Obstacle Avoidance control and the latter is Path Tracking control. Simulation results show that the proposed architecture effectively resolves the conflicts and achieve rapid movement towards the target waypoint. ABSTRAK: Keupayaan mengemudi Kenderaan Udara Tanpa Pemandu (UAV) dengan selamat di kawasan yang tidak diketahui menawarkan potensi yang besar untuk aplikasi yang lebih luas dalam ruang udara yang tidak terasing. Terbang di ruang udara yang tidak terasing menimbulkan risiko perlanggaran dengan halangan statik (contohnya, menara, talian kuasa) dan halangan bergerak (contohnya, pesawat udara, belon). Dalam kajian ini, kami mencadangkan satu strategi heuristik kawalan logik kabur yang melata untuk menyelesaikan masalah Pengesanan Konflik dan Penyelesaian (CD&R), di mana strategi kawalan yang terdiri daripada dua modul melata. Hasil simulasi menunjukkan bahawa seni bina yang dicadangkan berjaya menyelesaikan konflik dan mencapai penerbangan pesat ke arah titik laluan sasaran. KEYWORDS: fuzzy logic; motion planning; obstacle avoidance; path tracking; reactive navigation; UA

NASA patent abstracts bibliography: A continuing bibliography. Section 1: Abstracts (supplement 40)

Abstracts are provided for 181 patents and patent applications entered into the NASA scientific and technical information system during the period July 1991 through December 1991. Each entry consists of a citation, an abstract, and in most cases, a key illustration selected from the patent or patent application

Aerospace Medicine and Biology: A continuing bibliography with indexes (supplement 246)

This bibliography lists 219 reports, articles and other documents introduced into the NASA scientific and technical information system in May 1983