Route or Flood? Reliable and Efficient Support for Downward Traffic in RPL

International audienc

Compressor valve failure detection and prognostics

Reciprocating compressors are commonly used machinery for industrial applications. Unscheduled downtime and maintenance activity on the compressors causes considerable loss in throughput and efficiency of a plant. Of all the failures that cause unscheduled downtime in reciprocating compressors, valve related causes are predominant. Most of the failures associated with the valves are tracked to the failure of moving elements within the valve. Achieving higher reliability of critical reciprocating systems requires continuously monitoring the system and performing dynamic analysis of the sensory data for valve fault diagnosis. Continuous monitoring will improve the time and cost to repair through keeping a constant vigil for failure events. Though there has been a good amount of work done for condition monitoring of compressors, there has been very little work on detecting and predicting valve failures. The objective of this thesis is to research detection and prediction of valve failures by wavelet analysis, logistic regression and neural network analysis of pressure and temperature signals, which are the most common measurements on a reciprocating compressor system. Valve failures are seeded on a reciprocating compressor testbed that is instrumented with only temperature and pressure sensor order emulate the reciprocating compressor systems used in the industry. The parameters are measured on a continuous basis and baselines are established for normal (or acceptable) behavior and failure (or fault) condition. Deviation of the system from the normal condition and the time for the system to reach the fault mode is quantified with the help of the above mentioned tools. --Abstract, page iii

Dynamics and Control of Spacecraft Rendezvous By Nonlinear Model Predictive Control

This doctoral research investigates the fundamental problems in the dynamics and control of spacecraft rendezvous with a non-cooperative tumbling target. New control schemes based on nonlinear model predictive control method have been developed and validated experimentally by ground-based air-bearing satellite simulators. It is focused on the autonomous rendezvous for a chaser spacecraft to approach the target in the final rendezvous stage. Two challenges have been identified and investigated in this stage: the mathematical modeling of the targets tumbling motion and the constrained control scheme that is solvable in an on-line manner. First, the mathematical description of the tumbling motion of the target spacecraft is proposed for the chaser spacecraft to rendezvous with the target. In the meantime, the practical constraints are formulated to ensure the safety and avoid collision during the final approaching stage. This set of constraints are integrated into the trajectory planning problem as a constrained optimization problem. Second, the nonlinear model predictive control is proposed to generate the feedback control commands by iteratively solving an open-loop discrete-time nonlinear optimal control problem at each sampling instant. The proposed control scheme is validated both theoretically and experimentally by a custom-built spacecraft simulator floating on a high-accuracy granite table. Computer software for electronic hardware for the spacecraft simulator and for the controller is designed and developed in house. The experimental results demonstrate the effectiveness and advantages of the proposed nonlinear model predictive control scheme in a hardware-in-the-loop environment. Furthermore, a preliminary outlook is given for future extension of the spacecraft simulator with consideration of the robotic arms

Advancing automation and robotics technology for the Space Station Freedom and for the US economy

The progress made by levels 1, 2, and 3 of the Office of Space Station in developing and applying advanced automation and robotics technology is described. Emphasis is placed upon the Space Station Freedom Program responses to specific recommendations made in the Advanced Technology Advisory Committee (ATAC) progress report 10, the flight telerobotic servicer, and the Advanced Development Program. Assessments are presented for these and other areas as they apply to the advancement of automation and robotics technology for the Space Station Freedom

Aerospace medicine and biology: A continuing bibliography with indexes (supplement 333)

This bibliography lists 122 reports, articles and other documents introduced into the NASA Scientific and Technical Information System during January, 1990. Subject coverage includes: aerospace medicine and psychology, life support systems and controlled environments, safety equipment, exobiology and extraterrestrial life, and flight crew behavior and performance

Flexible Blue-Light Fiber Amplifiers to Improve Signal Coverage in Advanced Lighting Communication Systems

Visible-light communication (VLC) based on white light-emitting diodes has recently attracted much attention to provide high-bitrate data communication in indoor environments. One of the remaining challenges to be resolved to enable the proliferation of VLC systems is related to channel attenuation and multiple path fading. Here, we introduce an advanced VLC system integrating an optical amplifier as a promising solution to overcome channel impairments, providing high bitrate coverage. The optical amplifier is a flexible fiber based on a poly(fluorene)-based lumophore doped within a di-ureasil organic-inor- ganic hybrid. Optical amplification is demonstrated for pre-amplifier and relay node scenarios, yielding a maximum gain of 5.9 G 0.2 dB and 3.7 G 0.2 dB, respectively, establishing the proposed approach as a promising cost-effective solution for VLCs. Additionally, numerical simulations show, for a realistic envi- ronment, a 207% improvement in the coverage area, using existing lighting infrastructure without extra cost.R.C.E. acknowledges funding from the European Research Council (ERC) under the European Union’s Ho- rizon 2020 research and innovation programme (grant agreement no. 818762 - SPECTRACON)

The 1992 Research/Technology report

The 1992 Research & Technology report is organized so that a broad cross section of the community can readily use it. A short introductory paragraph begins each article and will prove to be an invaluable reference tool for the layperson. The approximately 200 articles summarize the progress made during the year in various technical areas and portray the technical and administrative support associated with Lewis technology programs

Marshall Space Flight Center Research and Technology Report 2019

Today, our calling to explore is greater than ever before, and here at Marshall Space Flight Centerwe make human deep space exploration possible. A key goal for Artemis is demonstrating and perfecting capabilities on the Moon for technologies needed for humans to get to Mars. This years report features 10 of the Agencys 16 Technology Areas, and I am proud of Marshalls role in creating solutions for so many of these daunting technical challenges. Many of these projects will lead to sustainable in-space architecture for human space exploration that will allow us to travel to the Moon, on to Mars, and beyond. Others are developing new scientific instruments capable of providing an unprecedented glimpse into our universe. NASA has led the charge in space exploration for more than six decades, and through the Artemis program we will help build on our work in low Earth orbit and pave the way to the Moon and Mars. At Marshall, we leverage the skills and interest of the international community to conduct scientific research, develop and demonstrate technology, and train international crews to operate further from Earth for longer periods of time than ever before first at the lunar surface, then on to our next giant leap, human exploration of Mars. While each project in this report seeks to advance new technology and challenge conventions, it is important to recognize the diversity of activities and people supporting our mission. This report not only showcases the Centers capabilities and our partnerships, it also highlights the progress our people have achieved in the past year. These scientists, researchers and innovators are why Marshall and NASA will continue to be a leader in innovation, exploration, and discovery for years to come

Analytical screening of low emissions, high performance duct burners for supersonic cruise aircraft engines

An analytical screening study was conducted to identify duct burner concepts capable of providing low emissions and high performance in advanced supersonic engines. Duct burner configurations ranging from current augmenter technology to advanced concepts such as premix-prevaporized burners were defined. Aerothermal and mechanical design studies provided the basis for screening these configurations using the criteria of emissions, performance, engine compatibility, cost, weight and relative risk. Technology levels derived from recently defined experimental low emissions main burners are required to achieve both low emissions and high performance goals. A configuration based on the Vorbix (Vortex burning and mixing) combustor concept was analytically determined to meet the performance goals and is consistent with the fan duct envelope of a variable cycle engine. The duct burner configuration has a moderate risk level compatible with the schedule of anticipated experimental programs