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  • 1
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    A preliminary design for flight testing the FINDS algorithm (1986)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: This report presents a preliminary design for flight testing the FINDS (Fault Inferring Nonlinear Detection System) algorithm on a target flight computer. The FINDS software was ported onto the target flight computer by reducing the code size by 65%. Several modifications were made to the computational algorithms resulting in a near real-time execution speed. Finally, a new failure detection strategy was developed resulting in a significant improvement in the detection time performance. In particular, low level MLS, IMU and IAS sensor failures are detected instantaneously with the new detection strategy, while accelerometer and the rate gyro failures are detected within the minimum time allowed by the information generated in the sensor residuals based on the point mass equations of motion. All of the results have been demonstrated by using five minutes of sensor flight data for the NASA ATOPS B-737 aircraft in a Microwave Landing System (MLS) environment.
    Keywords: AIRCRAFT INSTRUMENTATION
    Type: NASA-CR-178043 , NAS 1.26:178043 , R8602
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    Design considerations for flight test of a fault inferring nonlinear detection system algorithm for avionics sensors (1986)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: This paper summarizes the modifications made to the design of a fault inferring nonlinear detection system (FINDS) algorithm to accommodate flight computer constraints and the resulting impact on the algorithm performance. An overview of the flight data-driven FINDS algorithm is presented. This is followed by a brief analysis of the effects of modifications to the algorithm on program size and execution speed. Significant improvements in estimation performance for the aircraft states and normal operating sensor biases, which have resulted from improved noise design parameters and a new steady-state wind model, are documented. The aircraft state and sensor bias estimation performances of the algorithm's extended Kalman filter are presented as a function of update frequency of the piecewise constant filter gains. The results of a new detection system strategy and failure detection performance, as a function of an update frequency, are also presented.
    Keywords: AIRCRAFT INSTRUMENTATION
    Type: AIAA PAPER 86-2030
    Format: text
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  • 3
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    Systems approach to software fault tolerance (1985)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Computing systems are employed for aerospace applications with high reliability requirements. In order to provide the needed reliability, it was necessary to make use of computing systems with fault-tolerance characteristics. Traditionally, fault tolerance is achieved through the use of hardware redundance. However, fault-tolerant techniques based on suitable software design considerations have also been developed. The present paper is concerned with the major issues arising in the context of an application of fault-tolerant software techniques to dynamic systems. Attention is given to fault-tolerant flight software, software component stability, system stability with fault-tolerant software, the preservation of functional performance, N-version vs. recovery blocks in flight software, systems-based software, static and dynamic models, static and dynamic consistency tests, and recovery block initialization.
    Keywords: COMPUTER PROGRAMMING AND SOFTWARE
    Type: AIAA PAPER 85-6018
    Format: text
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  • 4
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    A Fault Tolerant System for an Integrated Avionics Sensor Configuration (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An aircraft sensor fault tolerant system methodology for the Transport Systems Research Vehicle in a Microwave Landing System (MLS) environment is described. The fault tolerant system provides reliable estimates in the presence of possible failures both in ground-based navigation aids, and in on-board flight control and inertial sensors. Sensor failures are identified by utilizing the analytic relationships between the various sensors arising from the aircraft point mass equations of motion. The estimation and failure detection performance of the software implementation (called FINDS) of the developed system was analyzed on a nonlinear digital simulation of the research aircraft. Simulation results showing the detection performance of FINDS, using a dual redundant sensor compliment, are presented for bias, hardover, null, ramp, increased noise and scale factor failures. In general, the results show that FINDS can distinguish between normal operating sensor errors and failures while providing an excellent detection speed for bias failures in the MLS, indicated airspeed, attitude and radar altimeter sensors.
    Keywords: AIRCRAFT COMMUNICATIONS AND NAVIGATION
    Type: NASA-CR-3834 , NAS 1.26:3834 , BBN-5352
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  • 5
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    Performance analysis of a fault inferring nonlinear detection system algorithm with integrated avionics flight data (1985)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: This paper presents the performance analysis results of a fault inferring nonlinear detection system (FINDS) using integrated avionics sensor flight data for the NASA ATOPS B-737 aircraft in a Microwave Landing System (MLS) environment. First, an overview of the FINDS algorithm structure is given. Then, aircraft state estimate time histories and statistics for the flight data sensors are discussed. This is followed by an explanation of modifications made to the detection and decision functions in FINDS to improve false alarm and failure detection performance. Next, the failure detection and false alarm performance of the FINDS algorithm are analyzed by injecting bias failures into fourteen sensor outputs over six repetitive runs of the five minutes of flight data. Results indicate that the detection speed, failure level estimation, and false alarm performance show a marked improvement over the previously reported simulation runs. In agreement with earlier results, detection speed is faster for filter measurement sensors such as MLS than for filter input sensors such as flight control accelerometers. Finally, the progress in modifications of the FINDS algorithm design to accommodate flight computer constraints is discussed.
    Keywords: COMPUTER PROGRAMMING AND SOFTWARE
    Type: AIAA PAPER 85-6022
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  • 6
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    On the internal target model in a tracking task (1981)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: An optimal control model for predicting operator's dynamic responses and errors in target tracking ability is summarized. The model, which predicts asymmetry in the tracking data, is dependent on target maneuvers and trajectories. Gunners perception, decision making, control, and estimate of target positions and velocity related to crossover intervals are discussed. The model provides estimates for means, standard deviations, and variances for variables investigated and for operator estimates of future target positions and velocities.
    Keywords: MAN/SYSTEM TECHNOLOGY AND LIFE SUPPORT
    Type: JPL Proc. of the 17th Conf. on Manual Control; p 393-397
    Format: application/pdf
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  • 7
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    The effects of multiplicative motor noise on the optimal human operator model (1982)
    In:  Other Sources
    Details
    Publication Date: 2016-06-07
    Description: The effects of a multiplicative motor noise model on the optimal-control human operator model were analyzed. A study of the interaction between multiplicative motor noise variance, plant dynamics, and predicted operator response behavior shows that, in general, an increase in motor noise variance produces a decrease in operator gain and a decrease in high-frequency remnant. An increase in multiplicative motor noise variance is also reflected by an increase in the effective motor time constant; in the absence of a cost penalty on commanded control, the motor time constant equals the motor noise variance.
    Keywords: MAN/SYSTEM TECHNOLOGY AND LIFE SUPPORT
    Type: NASA. Ames Research Center 16th Ann. Conf. on Manual Control; p 106-118
    Format: text
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  • 8
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    Expert systems for real-time monitoring and fault diagnosis (1989)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Methods for building real-time onboard expert systems were investigated, and the use of expert systems technology was demonstrated in improving the performance of current real-time onboard monitoring and fault diagnosis applications. The potential applications of the proposed research include an expert system environment allowing the integration of expert systems into conventional time-critical application solutions, a grammar for describing the discrete event behavior of monitoring and fault diagnosis systems, and their applications to new real-time hardware fault diagnosis and monitoring systems for aircraft.
    Keywords: CYBERNETICS
    Type: NASA-CR-179441 , NAS 1.26:179441 , H-1540
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  • 9
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    User's guide to the Fault Inferring Nonlinear Detection System (FINDS) computer program (1988)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Described are the operation and internal structure of the computer program FINDS (Fault Inferring Nonlinear Detection System). The FINDS algorithm is designed to provide reliable estimates for aircraft position, velocity, attitude, and horizontal winds to be used for guidance and control laws in the presence of possible failures in the avionics sensors. The FINDS algorithm was developed with the use of a digital simulation of a commercial transport aircraft and tested with flight recorded data. The algorithm was then modified to meet the size constraints and real-time execution requirements on a flight computer. For the real-time operation, a multi-rate implementation of the FINDS algorithm has been partitioned to execute on a dual parallel processor configuration: one based on the translational dynamics and the other on the rotational kinematics. The report presents an overview of the FINDS algorithm, the implemented equations, the flow charts for the key subprograms, the input and output files, program variable indexing convention, subprogram descriptions, and the common block descriptions used in the program.
    Keywords: AIRCRAFT COMMUNICATIONS AND NAVIGATION
    Type: NASA-CR-178410 , R8801 , NAS 1.26:178410
    Format: application/pdf
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  • 10
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    Study of fault tolerant software technology for dynamic systems (1985)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The major aim of this study is to investigate the feasibility of using systems-based failure detection isolation and compensation (FDIC) techniques in building fault-tolerant software and extending them, whenever possible, to the domain of software fault tolerance. First, it is shown that systems-based FDIC methods can be extended to develop software error detection techniques by using system models for software modules. In particular, it is demonstrated that systems-based FDIC techniques can yield consistency checks that are easier to implement than acceptance tests based on software specifications. Next, it is shown that systems-based failure compensation techniques can be generalized to the domain of software fault tolerance in developing software error recovery procedures. Finally, the feasibility of using fault-tolerant software in flight software is investigated. In particular, possible system and version instabilities, and functional performance degradation that may occur in N-Version programming applications to flight software are illustrated. Finally, a comparative analysis of N-Version and recovery block techniques in the context of generic blocks in flight software is presented.
    Keywords: COMPUTER PROGRAMMING AND SOFTWARE
    Type: NASA-CR-172618 , NAS 1.26:172618
    Format: application/pdf
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