Michael D. Watson

Data-driven neural network methodology to remaining life predictions for aircraft actuator components

Actuators are complex electro-hydraulic or mechanical mechanisms utilized in aircraft to drive flight control surfaces, landing gear, cargo doors, and weapon systems. Impact has developed a prognostic and health management (PHM) methodology for these critical systems that includes signal processing and neural network tracking techniques, along with automated reasoning, classification, knowledge fusion, and probabilistic failure mode progression algorithms. The processing utilizes the command/response signal and hydraulic pressure data from the actuators and provides a real-time assessment of the current/future actuator health state. This methodology was applied to F/A-18 stabilator electro-hydraulic servo valves (EHSVs) using test stand data provided by Boeing Phantom works. The automated module demonstrated excellent health state classification results. The prognosis was also successfully performed however no data was available to validate the prediction. These algorithms were developed with consideration to sensor/processing limitations for potential onboard implementation. Many of the PHM elements presented here could also be adapted for other actuator types and applications.

A framework for integration of IVHM technologies for intelligent integration for vehicle management

As a part of the overall goal of developing Integrated Vehicle Health Management (IVHM) systems for aerospace vehicles, the NASA Faculty Fellowship Program (NFFP) at Marshall Space Flight Center has performed a pilot study on IVHM principles which integrates researched IVHM technologies in support of integrated intelligent vehicle management (IIVM). IVHM is the process of assessing, preserving, and restoring system functionality across flight and ground systems. The framework presented in this paper integrates advanced computational techniques with sensor and communication technologies for spacecraft that can generate responses through detection, diagnosis, reasoning, and adapt to system faults in support of IIVM. These real-time responses allow the IIVM to modify the affected vehicle subsystem(s) prior to a catastrophic event. Furthermore, the objective of this pilot program is to develop and integrate technologies which can provide a continuous, intelligent, and adaptive health state of a vehicle and use this information to improve safety and reduce costs of operations. Recent investments in avionics, health management, and controls have been directed towards IIVM. As this concept has matured, it has become clear that IIVM requires the same sensors and processing capabilities as the real-time avionics functions to support diagnosis of subsystem problems. New sensors have been proposed, in addition to augment the avionics sensors to support better system monitoring and diagnostics. As the designs have been considered, a synergy has been realized where the real-time avionics can utilize sensors proposed for diagnostics and prognostics to make better real-time decisions in response to detected failures. IIVM provides for a single system allowing modularity of functions and hardware across the vehicle. The framework that supports IIVM consists of 11 major on-board functions necessary to fully manage a space vehicle maintaining crew safety and mission objectives. These systems include the following: guidance and navigation; communications and tracking; vehicle monitoring; information transport and integration; vehicle diagnostics; vehicle prognostics; vehicle mission planning; automated repair and replacement; vehicle control; human computer interface; and onboard verification and validation. Furthermore, the presented framework provides complete vehicle management which not only allows for increased crew safety and mission success through new intelligence capabilities, but also yields a mechanism for more efficient vehicle operations. The representative IVHM technologies for IIVM includes: 1) enhanced communications and telemetry, 2) sensors for radiation materials, 3) vehicle controls and dynamics, 4) flight mechanics and control, 4) embedded sensors for structural integrity of tanking systems, 5) evolutionary concepts for embedded sensor placement in tank systems, 6) real time operating systems, and 7) computer architectures for distributed processing for IVHM. This paper presents the IIVM framework and the IVHM technologies developed under NASAs NFFP pilot project

A Theory of Vehicle Management Systems

With the increasing capability of computers, engineers have designed vehicles to perform ever more complex tasks. Whether fully automated, as with robotic space probes, or partially automated in conjunction with a crew, vehicles have become both more complex and more capable. To manage this complexity, designers have developed increasingly sophisticated vehicle management systems (VMS) to manage vehicle internal states, and to operate in its external environment. While often effective, design of VMSs has often been on an ad hoc basis. Using insights from information theory, complexity theory, and artificial intelligence, this paper develops a theoretical framework in which to understand the nature of VMSs. The theory defines the interaction of VMS functions and provides a mathematical formulation to assess the complexity of different VMS configurations.

Modeling wave propagation and scattering from impact damage for structural health monitoring of composite sandwich plates

Results of modeling of the wave propagation, impact, and damage detection in a sandwich honeycomb plate using piezoelectric actuator/sensor scheme are reported. A finite element model of honeycomb sandwich panel that reproduces accurately experimental setup and takes into account main characteristic features of the real composite panel, impactor, lead zirconate titanate actuator, and sensors is developed. The impact is simulated to obtain damage with parameters close to those observed in the experiment. Both in simulations and in experiment, the voltage signal of a given shape is applied to the lead zirconate titanate actuators to excite acoustic wave, and the electrical signals collected from the lead zirconate titanate sensors mounted to the panel are used to study wave propagation in the sandwich panel. The results of simulation are shown to be in good agreement with the experimental results both before and after the impact. Properties of acoustic wave propagating in composite sandwich honeycomb panels are discussed.

Dynamical Model of Rocket Propellant Loading with Liquid Hydrogen

Viatcheslav V. Osipov MCT, Inc., Moffett Field, California 94035 Matthew J. Daigle University of California, Santa Cruz, Moffett Field, California 94035 Cyrill B. Muratov New Jersey Institute of Technology, Newark, New Jersey 07102 Michael Foygel SGT, Inc., Newark, New Jersey 07102 Vadim N. Smelyanskiy NASA Ames Research Center, Moffett Field, California 94035 and Michael D. Watson NASA Marshall Space Flight Center, Huntsville, Alabama 35805

Fault diagnostics and prognostics for large segmented SRMs

We report progress in development of the fault diagnostic and prognostic (FD&P) system for large segmented solid rocket motors (SRMs). The model includes the following main components: (i) 1D dynamical model of internal ballistics of SRMs; (ii) surface regression model for the propellant taking into account erosive burning; (iii) model of the propellant geometry; (iv) model of the nozzle ablation; (v) model of a hole burning through in the SRM steel case. The model is verified by comparison of the spatially resolved time traces of the flow parameters obtained in simulations with the results of the simulations obtained using high-fidelity 2D FLUENT model (developed by the third party). To develop FD&P system of a case breach fault for a large segmented rocket we notice [1] that the stationary zero-dimensional approximation for the nozzle stagnation pressure is surprisingly accurate even when stagnation pressure varies significantly in time during burning tail-off. This was also found to be true for the case breach fault [2]. These results allow us to use the FD&P developed in our earlier research [3]-[6] by substituting head stagnation pressure with nozzle stagnation pressure. The axial corrections to the value of the side thrust due to the mass addition are taken into account by solving a system of ODEs in spatial dimension.

Modeling of optical waveguide poling and thermally stimulated discharge (TSD) charge and current densities for guest/host electro-optic polymers

A charge density and current density model of a waveguide system has been developed to explore the effects of electric field electrode poling. An optical waveguide is modeled during poling by considering the dielectric charge distribution, polarization charge distribution, and conduction charge generated by the poling field. The charge distributions are the source of poling current densities. The model shows that boundary charge current density and polarization current density are the major source of currents measured during poling and thermally stimulated discharge measurements. Charge distributions provide insight into the poling mechanisms and are directly related to E/sub A/ and /spl alpha//sub r/. Initial comparisons with experimental data show excellent correlation to the model results.

An Abort Failure Detection, Notification, & Response System: Overview of an ISHM Development Process

Timely detection and response to catastrophic events during the launch and ascent phase of a launch system is of paramount importance to crew safety. This requires an abort system capable of detecting and confirming conditions that may lead to catastrophic failure, notifying the crew of the problem, and responding in time to allow the crew to escape safely. The development process for an Abort Failure Detection, Notification, and Response System is described. The process follows an iterative approach that first analyzes the vehicle design and identifies potential abort conditions. Those conditions are then characterized through modeling and simulation, with the results being used to identify required sensors and develop algorithms capable of detecting and responding to abort anomalies that could jeopardize the crew and mission. This process can be applied in the development of future crewed vehicles and other complex vehicle systems.

Space application requirements for organic avionics

The NASA Marshall Space Flight Center is currently evaluating polymer based components for application in launch vehicle and propulsion system avionics systems. Organic polymers offer great advantages over inorganic corollaries. Unlike inorganics with crystalline structures defining their sensing characteristics, organic polymers can be engineered to provide varying degrees of sensitivity for various parameters including electro-optic response, second harmonic generation, and piezoelectric response. While great advantages in performance can be achieved with organic polymers, survivability in the operational environment is a key aspect for their practical application. The space environment in particular offers challenges that must be considered in the application of polymer based devices. These challenges include: long term thermal stability for long duration missions, extreme thermal cycling, space radiation tolerance, vacuum operation, low power operation, high operational reliability. Requirements for application of polymer based devices in space avionics systems will be presented and discussed in light of current polymer materials.

Modeling of electrooptic polymer electrical characteristics in a three-layer optical waveguide modulator

The electrical characteristics of electrooptic polymer waveguide modulators are often described by the bulk reactance of the individual layers. However, the resistance and capacitance between the layers can significantly alter the electrical performance of a waveguide modulator. These interface characteristics are related to the boundary charge density and are strongly affected by the adhesion of the layers in the waveguide stack. An electrical reactance model has been derived to investigate this phenomenon at low frequencies. The model shows the waveguide stack frequency response has no limiting effects below the microwave range and that a true dc response requires a stable voltage for over 1000 h. Thus, reactance of the layers is the key characteristic of optimizing the voltage across the core layer, even at very low frequencies (>10/sup -6/ Hz). The results of the model are compared with experimental data for two polymer systems and show quite good correlation.