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Nonlinear models and block diagrams of an inner-loop control system for the ATOPS B-737 Research Aircraft are presented. Continuous time linear model representations of the nonlinear inner-loop control systems are derived. Closed-loop aircraft simulations comparing nonlinear and linear dynamic responses to step inputs are used to verify the inner-loop control system models.
Abstract The Caribbean fruit fly, Anastrepha suspensa (Loew) (Diptera: Tephritidae), is a quarantine pest of Citrus spp. and a production pest of guava and other specialty fruits in Florida. Effective monitoring lures and traps are needed for early pest detection and timely initiation of control measures. As part of a continued effort to identify attractive synthetic lures for the Caribbean fruit fly, we conducted field tests in Homestead, Florida to compare the efficacy and longevity of commercial 2- and 3-component cone lures (2C [ammonium acetate and putrescine], 3C [ammonium acetate, putrescine, and trimethylamine]), the current standards used by regulatory agencies, versus the traditional liquid protein bait consisting of hydrolyzed torula yeast and borax as a positive control. Additional lures were also field-aged and periodically brought into the laboratory to quantify residual chemical contents. Traps baited with the torula yeast-borax mixture captured the highest mean number of A. suspensa, and traps baited with the commercial 2C lures captured more flies than the 3C lures. Traps baited with torula yeast-borax also captured the highest number of nontarget Diptera. Captures with all three treatments were significantly biased toward females. Attractiveness of the 2C lure began to drop after 6–8 wk, and the 3C lure after 5–6 wk. Overall, these data suggest that the 2C cone lure is more attractive to A. suspensa than the 3C cone lure under field conditions in south Florida, and that the 2C lures are attractive for up to 8 wk.
The establishment of a resilient electric grid accompanied by a secure communications network is an ongoing battle as advanced persistent threats continue to exploit existing vulnerabilities in legacy supervisory control and data acquisition system (SCADA) infrastructure. Traditional intrusion detection systems (IDSs) lack consistent performance because of the continuously evolving attack surface of SCADA systems. These shortcomings can be overcome by integrating logical system behavior, protocol-specific knowledge, and data-based learning to develop a comprehensive IDS solution. In this paper, we present a Hybrid Intrusion Detector for Energy Systems by integrating a network-based IDS, state-of-the-art machine learning-based IDS, and model-based IDS to detect unknown and stealthy cyberattacks targeting the SCADA networks. The proposed IDS uses synchrophasor measurements and cyber logs to learn patterns of different scenarios based on spatiotemporal behaviors of power systems. As a proof of concept, we implement and validate the proposed IDS by leveraging resources available at the National Renewable Energy Laboratory's Energy Systems Integration Facility test bed. Experimental results show promising performance in detecting cyberattacks while providing realtime visualization of power system measurements and cyber logs.
The first production DRIRU 2 (NASA standard high performance inertial reference unit) system was launched as a subsystem of the Modular Attitude Control System for the Solar Maximum Mission (SMM) spacecraft in February 1980. This hardware was retrieved during the repair of the SMM during Shuttle Flight 41-C in April 1984 and returned to Teledyne Systems Company (manufacturer) for investigation and performance measurements as directed by Goddard Space Flight Center. A failure of one of the three gyro channels occurred approximately 6.5 months after launch. The built in redundancy functioned properly, the DRIRU 2 continued to provide the required attitude control function without performance degradation. Subsequent failure of other attitude control subsystems made the SMM a candidate for the first demonstration of the shuttle in-orbit repair capabilty. The in-orbit DRIRU 2 II failure scenario and the results of the analyses/tests conducted after retrieval are discussed. Comparison of this data with similar data prior to launch demonstates the excellent stability of performance parameters achieveable with DRIRU 2.
Work continued on a number of projects aimed at the generation of tunable visible, infrared, and ultraviolet light; and on the control of this light by means of novel mode-locking and modulation techniques. Progress is summarized for the following projects: (1) the transient modelocking of the Nd:YAG laser and application of short optical pulses; (2) studies of the sodium-xenon excimer laser; (3) development of techniques for vacuum ultraviolet holography; and (4) studies of multiple photon pumped xenon and argon excimer lasers.
In 1974 ESOC decided to develop a reusable Mission Control System infrastructure for ESA's missions operated under its responsibility. This triggered a long and successful product development line, which started with the Multi Mission Support System (MSSS) which entered in service in 1977 and is still being used today by the MARECS and ECS missions; it was followed in 1989 by a second generation of systems known as SCOS-I, which was/is used by the Hipparcos, ERS-1 and EURECA missions and will continue to support all future ESCO controlled missions until approximately 1995. In the meantime the increasing complexity of future missions together with the emergence of new hardware and software technologies have led ESOC to go for the development of a third generation of control systems, SCOSII, which will support their future missions up to at least the middle of the next decade. The objective of the paper is to present the characteristics of the SCOSII system from the perspective of the mission control team; i.e. it will concentrate on the improvements and advances in the performance, functionality and work efficiency of the system.
U.S. Department of Energy (DOE) contractor CH2M Hill Plateau Remediation Company (CHPRC), a Jacobs owned company, is making significant progress demolishing the Plutonium Finishing Plant (PFP), which has long been known as one of the most hazardous buildings in the DOE Environmental Management Complex (DOE Complex). The facility is located on the Hanford Site and produced plutonium metal during the Cold War. Production was stopped in 1989, the facility was formally shut down in 1996, and material processing was completed in 2004. After approximately 25 years of demolition preparations, open-air demolition of the main portions of the Hazard Category II nuclear facility began in November 2016. To prepare the PFP for demolition, CHPRC employees performed some of the most hazardous work across the DOE Complex. In addition to extensive demolition preparations, including a wide-reaching communication strategy across the Hanford Site, CHPRC implemented robust controls and monitoring during demolition, and when necessary, adjusted demolition practices and sequence to maintain employee safety and project efficiency. Demolition of the main PFP building began in November 2016. The technical complexity, high hazards and radiological concerns have all led to a difficult demolition environment. Following a spread of contamination at the project site beyond the radiological boundaries in December 2017, work was halted and a recovery plan was generated to allow the demolition work to continue. After the implementation of additional controls and concurrence from regulatory agencies and DOE, the demolition was ready to resume work and reinitiated in August 2018. There are a number of lessons learned from the demolition activities and recovery plan process. This paper allows CHPRC and DoE's Richland Operations Office (RL) to share lessons learned and progress to date with other challenging and hazardous projects across the DOE Complex. Understanding the risk acceptance level is critical to execution of any open-air demolition project and is unique to each facility. Four key lessons learned from this project include: 1) plan execution issues, 2) stakeholder communication issues, 3) watching for summit fever and 4) minimizing exposed contaminated surfaces during demolition. (authors)
The behavior of materials in the space environment continues to be a limiting technology for spacecraft and experiments. The thermal control surfaces experiment (TCSE) aboard the Long Duration Exposure Facility (LDEF) is the most comprehensive experiment flown to study the effects of the space environment on thermal control surfaces. Selected thermal control surfaces were exposed to the LDEF orbital environment and the effects of this exposure were measured. The TCSE combined in-space orbital measurements with pre and post-flight analyses of flight materials to determine the effects of long term space exposure. The TCSE experiment objective, method, and measurements are described along with the results of the initial materials analysis. The TCSE flight system and its excellent performance on the LDEF mission is described. A few operational anomalies were encountered and are discussed.
An active flow control experiment was conducted on a 2-ft chord NACA 0036 airfoil in a 3-ft by 4-ft Wind Tunnel at Re = 1 x 10(exp 6). The model was equipped with synthetic jet actuators at x/c = 0.30 and 0.65 that provided 120 Hz periodic excitation at a C(sub mu) 0.86% through 0.06-in wide slots. Three different slot con gurations were tested, including a baseline with no slots. Surface pressure data was collected to compare to previous tests and to combine with turbulence data to aid future CFD modeling efforts. Turbulence data, measured by hot-wire, was compared with and without flow control. Pressure data corroborates previous test data and provides more points for CFD validation. Hot-wire results showed ow control reduced the separated wake size and brought the high Reynolds stress shear layer closer to the airfoil surface. The position of this layer to the surface was altered more significantly than the magnitude of the peak stresses. Flow control was shown to increase turbulent energy in the attached boundary layer downstream of the slot but to have little effect upstream. These results provide further justification to continue assessing the potential of active flow control to reduce drag of helicopter airframe components.
The use of Artificial Intelligence (AI) and the programming language Ada to help a satellite recover from selected failures that could lead to mission failure are described. An unmanned satellite will have a separate AI subsystem running in parallel with the normal satellite subsystems. A satellite monitoring subsystem (SMS), under the control of a blackboard system, will continuously monitor selected satellite subsystems to become alert to any actual or potential problems. In the case of loss of communications with the earth or the home base, the satellite will go into a survival mode to reestablish communications with the earth. The use of an AI subsystem in this manner would have avoided the tragic loss of the two recent Soviet probes that were sent to investigate the planet Mars and its moons. The blackboard system works in conjunction with an SMS and a reconfiguration control subsystem (RCS). It can be shown to be an effective way for one central control subsystem to monitor and coordinate the activities and loads of many interacting subsystems that may or may not contain redundant and/or fault-tolerant elements. The blackboard system will be coded in Ada using tools such as the ABLE development system and the Ada Production system.
Based on a kind of Q-Bézier surfaces with shape parameters, the basic properties of the surfaces and the geometric significance of the shape parameters are analyzed. To resolve the problem of shape control and adjustment of composite surfaces, the continuity conditions for Q-Bézier surfaces of degree (m, n) are investigated. Taking advantage of the terminal properties of generalized Bernstein basis functions, we derive the conditions of G{sup 1} and G{sup 2} continuity between two adjacent Q-Bézier surfaces. In addition, the specific steps of smooth continuity between Q-Bézier surfaces and the shape adjustment function of shape parameters for composite surfaces are discussed. The modeling examples show that the proposed smooth continuity conditions are not only intuitive and easy to implement, but also greatly enhance the shape adjustability, which provide a useful method for constructing complex surfaces in engineering design.
Small quartz-crystal-controlled oscillator swallowed or surgically implanted provides continuous monitoring of patient's internal temperature. Receiver placed near patient measures oscillator frequency, and temperature inferred from previously determined variation of frequency with temperature. Frequency of crystal-controlled oscillator varies with temperature. Circuit made very small and implanted or ingested to measure internal body temperature.
Abstract Biomolecules undergo continuous conformational motions, a subset of which are functionally relevant. Understanding, and ultimately controlling biomolecular function are predicated on the ability to map continuous conformational motions, and identify the functionally relevant conformational trajectories. For equilibrium and near-equilibrium processes, function proceeds along minimum-energy pathways on one or more energy landscapes, because higher-energy conformations are only weakly occupied. With the growing interest in identifying functional trajectories, the need for reliable mapping of energy landscapes has become paramount. In response, various data-analytical tools for determining structural variability are emerging. A key question concerns the veracity with which each data-analytical tool can extract functionally relevant conformational trajectories from a collection of single-particle cryo-EM snapshots. Using synthetic data as an independently known ground truth, we benchmark the ability of four leading algorithms to determine biomolecular energy landscapes and identify the functionally relevant conformational paths on these landscapes. Such benchmarking is essential for systematic progress toward atomic-level movies of continuous biomolecular function.
The research experience of SCOLE developed by the NASA Langley Research Center is reviewed. Particular attention is given to the advances made in control and modeling techniques, the experimental facilities that are now available, and the continuing needs to advance and to validate the technologies in controlling flexible structures.
A structured, disciplined methodology is required to control major cost-influencing metrics of space transportation systems during design and continuing through the test and operations phases. This paper proposes controlling key space system design metrics that specifically influence life cycle costs. These are inclusive of flight and ground operations, test, and manufacturing and infrastructure. The proposed technique builds on today's configuration and mass properties control techniques and takes on all the characteristics of a classical control system. While the paper does not lay out a complete math model, key elements of the proposed methodology are explored and explained with both historical and contemporary examples. Finally, the paper encourages modular design approaches and technology investments compatible with the proposed method.
The crisis of arms control is obvious and broadly discussed among states, within the world’s expert community and to a lesser extent the media. This crisis has at least three building blocks: Russia continues to violate or undermine key arms control treaties and commitments; China rejects to join the existing arms control architecture; and both countries heavily invest in the modernization of their armed forces, including development of the nuclear arsenals. In the current highly competitive environment, arms control is more difficult to achieve and is likely to accomplish less than what was optimistically anticipated a generation ago. The growing pressure to “save arms control at all cost”, often expressed by the Western expert community, further complicates the situation. The excessively aspirational and ideological approach to arms control – in which arms control, disarmament, and non-proliferation (ADN) become a silver bullet solution – is as dangerous as security and defence policies which entirely exclude ADN. As James Cameron rightly points out, “history should teach policy-makers to look beyond formulae for strategic stability to other ways in which arms control can help to contain disruptive challenges to the balance of power and minimize the chances of war”.
The desired response of many man machine control systems can be formulated as a solution to an optimal control synthesis problem where the cost index is given and the resulting optimal trajectories correspond to the desired trajectories of the man machine system. Optimal control synthesis provides the reference criteria and the significance of error information required for performance measurement. The synthesis procedure described provides a continuous performance measure (CPM) which is independent of the mechanism generating the control action. Therefore, the technique provides a meaningful method for online evaluation of man's control capability in terms of total man machine performance.
This report completes Milestone M2.2.2 - ZrH pellet fabricated with controlled hydride loading: ZrH1.5±0.1 single phase pellets fabricated with controlled and thermally stable hydride loading. Hydrogen content to be quantified and single-phase confirmed by X-ray diffraction. In this milestone, we report the successful fabrication of delta-phase zirconium hydride pellets using the ORNL bulk metal hydriding system. The successful deployment of zirconium hydride moderator in advanced reactors requires development of a consistent and affordable production pathway along with implementation of a hydrogen retention solution throughout the reactor life. Fabrication of delta-phase zirconium hydride is challenging since the absorption of a large amount of hydrogen into alpha-zirconium induces significant volume expansion and the present hydrogen concentration gradient results in cracking. A fully programmable hydriding system with continuous hydrogen partial pressure and flow control to facilitate processing of massive metal hydride has been developed at ORNL. In this report, the working principle of the hydriding system will be introduced. Characterization of the produced zirconium hydride includes X-ray powder diffraction to identify the present phases and X-ray Computed Tomography to visualize the internal microstructure (including cracks). The results indicate that single delta-phase zirconium hydride pellets with various sizes have been successfully produced.