Engineering topics
Publications and source records attributed to Elks, Carl R..
This paper outlines a candidate design and assessment methodology that is targeted for the early to mid-level phases of the design cycle. This method allows alternate architectural configurations to be effectively assessed to evaluate the effects of design changes and to reduce the number of inherent design errors.
This report presents the results of a performance analysis of a quad-redundant Fault-Tolerant Processor (FTP). The FTP is a computing system specifically designed for applications where very high reliability is required. Examples of such applications are flight control systems, nuclear power systems, and spacecraft control systems. The FTP performance was analyzed in a hierarchical manner encompassing the hardware, the operating system, and the application. At the hardware level, the hardware organization and design was assessed in relation to system throughput and response. Analysis at the operating system level revealed that the scheduler took only 3.2 percent of each 40ms frame, while the redundancy management software took 10.4 percent. The application level performance was analyzed via a synthetic workload and a representative flight control model. The estimated throughput for this application was found to be 317.6 KIPS if not exercising the voter. Exercising the voter to ensure fault tolerance will diminish this number linearly as the number of votes is increased. This performance analysis method was proven effective by uncovering undesirable behavior and anomalies in the FTP system.
This paper presents the results of a preliminary experiment to study the effectiveness of a fault-tolerant system's ability to handle transient faults. The primary goal of the experiment was to develop the techniques to measure the parameters needed for a reliability analysis of the SIFT computer system which includes th effects of transient faults. A key aspect of such an analysis is the determination of the effectiveness of the operating system's ability to discriminate between transient and permanent faults. A detailed description of the preliminary transient fault experiment along with the results from 297 transient fault injections are given. Although not enough data was obtained to draw statistically significant conclusions, the foundation has been laid for a large-scale transient fault experiment.
Described are the features, command language, and functional design of the SIFT (Software Implemented Fault Tolerance) fault injection and data acquisition interface software. The document is also intended to assist and guide the SIFT user in defining, developing, and executing SIFT fault injection experiments and the subsequent collection and reduction of that fault injection data. It is also intended to be used in conjunction with the SIFT User's Guide (NASA Technical Memorandum 86289) for reference to SIFT system commands, procedures and functions, and overall guidance in SIFT system programming.