Computerized Design of Low-noise Face-milled Spiral Bevel Gears

An advanced design methodology is proposed for the face-milled spiral bevel gears with modified tooth surface geometry that provides a reduced level of noise and has a stabilized bearing contact. The approach is based on the local synthesis of the gear drive that provides the 'best' machine-tool settings. The theoretical aspects of the local synthesis approach are based on the application of a predesigned parabolic function for absorption of undesirable transmission errors caused by misalignment and the direct relations between principal curvatures and directions for mating surfaces. The meshing and contact of the gear drive is synthesized and analyzed by a computer program. The generation of gears with the proposed geometry design can be accomplished by application of existing equipment. A numerical example that illustrates the proposed theory is presented

NASA/Army Rotorcraft Transmission Research, a Review of Recent Significant Accomplishments

A joint helicopter transmission research program between NASA Lewis Research Center and the U.S. Army Research Lab has existed since 1970. Research goals are to reduce weight and noise while increasing life, reliability, and safety. These research goals are achieved by the NASA/Army Mechanical Systems Technology Branch through both in-house research and cooperative research projects with university and industry partners. Some recent significant technical accomplishments produced by this cooperative research are reviewed. The following research projects are reviewed: oil-off survivability of tapered roller bearings, design and evaluation of high contact ratio gearing, finite element analysis of spiral bevel gears, computer numerical control grinding of spiral bevel gears, gear dynamics code validation, computer program for life and reliability of helicopter transmissions, planetary gear train efficiency study, and the Advanced Rotorcraft Transmission (ART) program

Summary of drive-train component technology in helicopters

A review of current helicopters was conducted to determine the technology in the drive-train systems. The design features are highlighted including reliability characteristics in transmission systems for the OH-58, UH-1, CH-47, and UH-60 helicopters. In addition, trade-offs involving cost, reliability and life are discussed

Advanced Rotorcraft Transmission (ART) program

Work performed by the McDonnell Douglas Helicopter Company and Lucas Western, Inc. within the U.S. Army/NASA Advanced Rotorcraft Transmission (ART) Program is summarized. The design of a 5000 horsepower transmission for a next generation advanced attack helicopter is described. Government goals for the program were to define technology and detail design the ART to meet, as a minimum, a weight reduction of 25 percent, an internal noise reduction of 10 dB plus a mean-time-between-removal (MTBR) of 5000 hours compared to a state-of-the-art baseline transmission. The split-torque transmission developed using face gears achieved a 40 percent weight reduction, a 9.6 dB noise reduction and a 5270 hour MTBR in meeting or exceeding the above goals. Aircraft mission performance and cost improvements resulting from installation of the ART would include a 17 to 22 percent improvement in loss-exchange ratio during combat, a 22 percent improvement in mean-time-between-failure, a transmission acquisition cost savings of 23 percent of $165K, per unit, and an average transmission direct operating cost savings of 33 percent, or$24K per flight hour. Face gear tests performed successfully at NASA Lewis are summarized. Also, program results of advanced material tooth scoring tests, single tooth bending tests, Charpy impact energy tests, compact tension fracture toughness tests and tensile strength tests are summarized

Investigation of 3D Non-Contact Laser-Based Inspection Techniques for Application in Gear Metrology

Gear shape accuracy, surface quality and, as a consequence, a proper gear inspection needed to guarantee these features, are critical in order to improve drivetrain efficiency as well as to reduce noise in automotive power transmission systems. Contact stylus type measuring methods using contact probes are today’s dominant indus- trial solution for gear metrology. Due to the difficulties of further improving those methods, new non-contact measuring systems have been developed in the past few years. The most promising option that meets the requirements of accuracy, repeatability and high cycle time is the 3D non-contact measurement method based on triangulation laser sensors. These laser scanners have been improved over the last few years both in terms of resolu- tion, optical quality, image processing and data analysis to make them comparable, if not superior, to the traditional contact probe. This thesis provides an evaluation of the surface profilometer Urano HC-N400, using the contact technology currently employed by Omega gear metrology labs as a benchmark. The measurements obtained with the alternative inspection system indicate that the analyzed non-contact solution is not ready yet for in-line and high volume inspection applications, but is well-suited to research and development purposes. Omega is also looking for the possible causes of a particular noise problem which is difficult to detect using current technology. One gear that exhibited this phantom phenomenon, also know as the ghost noise , has been analyzed and compared with another gear identified as the best of best . During the analysis, undulations have been found in both gears. The combination of those waves through the use of the Ripple Analysis software represents the best solution to discover other gears with the same problem in the early stages of inspection

Ekonomicky dostupný aktivní exoskeleton pro dolní končetiny pro paraplegiky

After a broad introduction to the medical and biomechanical background and detailed review of orthotic devices, two newly developed lower limbs exoskeletons for paraplegics are presented in this study. There was found out the main challenges of designing devices for paraplegic walking can be summarized into three groups, stability and comfort, high efficiency or low energy consumption, dimensions and weight. These all attributes have to be moreover considered and maintained during manufacturing of affordable device while setting a reasonable price of the final product. A new economical device for people with paraplegia which tackles all problems of the three groups is introduced in this work. The main idea of this device is based on HALO mechanism. HALO is a compact passive medial hip joint orthosis with contralateral hip and ankle linkage, which keeps the feet always parallel to the ground and assists swinging the leg. The medial hip joint is equipped with one actuator in the new design and the new active exoskeleton is called @halo. Due to this update, we can achieve more stable and smoother walking patterns with decreased energy consumption of the users, yet maintain its compact and lightweight features. It was proven by the results from preliminary experiments with able-bodied subjects during which the same device with and without actuator was evaluated. Waddling and excessive vertical elevation of the centre of gravity were decreased by 40% with significantly smaller standard deviations in case of the powered exoskeleton. There was 52% less energy spent by the user wearing @halo which was calculated from the vertical excursion difference. There was measured 38.5% bigger impulse in crutches while using passive orthosis, which produced bigger loads in upper extremities musculature. The inverse dynamics approach was chosen to calculate and investigate the loads applied to the upper extremities. The result of this calculation has proven that all main muscle groups are engaged more aggressively and indicate more energy consumption during passive walking. The new @halo device is the first powered exoskeleton for lower limbs with just one actuated degree of freedom for users with paraplegia.První část práce je věnována obsáhlému úvodu do zdravotnické a biomechanické terminologie a detailnímu souhrnnému představení ortopedických pomůcek. Následně jsou představeny dva nově vyvinuté exoskelety aplikovatelné na dolní končetiny paraplegiků. Bylo zjištěno, že hlavní úskalí konstrukčního návrhu asistenčních zařízení pro paraplegiky lze shrnout do tří hlavních skupin, jako první je stabilita a komfort, druhá je vysoká účinnost a nízká energetická náročnost uživatele a do třetí lze zahrnout rozměry a hmotnost zařízení. Toto všechno je navíc podmíněno přijatelnou výslednou cenou produktu. Nový ekonomicky dostupný exoskelet pro paraplegiky, který řeší problematiku všech tří zmíněných skupin je představen v této práci. Hlavní myšlenka tohoto zařízení je postavena na mechanismu HALO ortézy. HALO je kompaktní pasivní ortéza s mediálním kyčelním kloubem umístěným uprostřed mezi dolními končetinami. Speciální mediální kyčelní kloub je kontralaterálně propojen s kotníkem soustavou ocelových lanek což zajištuje paralelní polohu chodidla se zemí v každém okamžiku chůze a navíc asistuje zhoupnutí končetiny. Tento mediální kyčelní kloub je redesignován a v novém provedení je vybaven jedním aktuátorem, nové řešení aktivního exoskeletu dostalo název @halo. Díky tomuto vylepšení lze dosáhnout stabilnější a plynulejší chůze s výrazně redukovanou energetickou náročností uživatele přičemž dochází k zachování nízké hmotnosti a kompaktnosti zařízení. Toto bylo dokázáno během předběžných experimentů se zdravými subjekty, během kterých byla testována aktivní chůze se zařízením vybaveným odnímatelnou pohonnou jednotkou a pasivní chůze se stejným zařízením bez této aktivní jednotky. Nadměrné naklánění se během chůze ze strany na stranu a nadměrná výchylka pohybu těžiště těla ve vertikálním směru byly sníženy o necelých 40% s velmi významně menšími standardními odchylkami v případě chůze s pohonem. Z rozdílu výchylky pohybu těžiště těla ve vertikální poloze bylo vypočítáno snížení energetické náročnosti uživatele o 52% při chůzi s aktivní konfiguraci @halo. Při pohybu s pasivní ortézou byl naměřen o 38,5% větší reakční silový impuls v berlích, což znamená nárůst zátěže pro svalový aparát horních končetin. Pro podrobné vyšetření zátěže ramenních kloubů byl aplikován model inverzní dynamiky. Výsledek tohoto výpočtu jednoznačně indikuje agresivnější a hlubší zapojení všech svalových skupin ramenního kloubu a tím vyšší spotřebu energie uživatelem během pasivní chůze. Nové asistenční zařízení @halo je prvním exoskeletem svého druhu pro paraplegiky s jediným poháněným stupněm volnosti.354 - Katedra robotikyvyhově

Special Issue of the Manufacturing Engineering Society (MES)

This book derives from the Special Issue of the Manufacturing Engineering Society (MES) that was launched as a Special Issue of the journal Materials. The 48 contributions, published in this book, explore the evolution of traditional manufacturing models toward the new requirements of the Manufacturing Industry 4.0 and present cutting-edge advances in the field of Manufacturing Engineering focusing on additive manufacturing and 3D printing, advances and innovations in manufacturing processes, sustainable and green manufacturing, manufacturing systems (machines, equipment and tooling), metrology and quality in manufacturing, Industry 4.0, product lifecycle management (PLM) technologies, and production planning and risks

A Summary of NASA Rotary Wing Research: Circa 20082018

The general public may not know that the first A in NASA stands for Aeronautics. If they do know, they will very likely be surprised that in addition to airplanes, the A includes research in helicopters, tiltrotors, and other vehicles adorned with rotors. There is, arguably, no subsonic air vehicle more difficult to accurately analyze than a vehicle with lift-producing rotors. No wonder that NASA has conducted rotary wing research since the days of the NACA and has partnered, since 1965, with the U.S. Army in order to overcome some of the most challenging obstacles to understanding the behavior of these vehicles. Since 2006, NASA rotary wing research has been performed under several different project names [Gorton et al., 2015]: Subsonic Rotary Wing (SRW) (20062012), Rotary Wing (RW) (20122014), and Revolutionary Vertical Lift Technology (RVLT) (2014present). In 2009, the SRW Project published a report that assessed the status of NASA rotorcraft research; in particular, the predictive capability of NASA rotorcraft tools was addressed for a number of technical disciplines. A brief history of NASA rotorcraft research through 2009 was also provided [Yamauchi and Young, 2009]. Gorton et al. [2015] describes the system studies during 20092011 that informed the SRW/RW/RVLT project investment prioritization and organization. The authors also provided the status of research in the RW Project in engines, drive systems, aeromechanics, and impact dynamics as related to structural dynamics of vertical lift vehicles. Since 2009, the focus of research has shifted from large civil VTOL transports, to environmentally clean aircraft, to electrified VTOL aircraft for the urban air mobility (UAM) market. The changing focus of rotorcraft research has been a reflection of the evolving strategic direction of the NASA Aeronautics Research Mission Directorate (ARMD). By 2014, the project had been renamed the Revolutionary Vertical Lift Technology Project. In response to the 2014 NASA Strategic Plan, ARMD developed six Strategic Thrusts. Strategic Thrust 3B was defined as the Ultra-Efficient Commercial VehiclesVertical Lift Aircraft. Hochstetler et al. [2017] uses Thrust 3B as an example for developing metrics usable by ARMD to measure the effectiveness of each of the Strategic Thrusts. The authors provide near-, mid-, and long-term outcomes for Thrust 3B with corresponding benefits and capabilities. The importance of VTOL research, especially with the rapidly expanding UAM market, eventually resulted in a new Strategic Thrust (to begin in 2020): Thrust 4Safe, Quiet, and Affordable Vertical Lift Air Vehicles. The underlying rotary wing analysis tools used by NASA are still applicable to traditional rotorcraft and have been expanded in capability to accommodate the growing number of VTOL configurations designed for UAM. The top-level goal of the RVLT Project remains unchanged since 2006: Develop and validate tools, technologies and concepts to overcome key barriers for vertical lift vehicles. In 2019, NASA rotary wing/VTOL research has never been more important for supporting new aircraft and advancements in technology. 2 A decade is a reasonable interval to pause and take stock of progress and accomplishments. In 10 years, digital technology has propelled progress in computational efficiency by orders of magnitude and expanded capabilities in measurement techniques. The purpose of this report is to provide a compilation of the NASA rotary wing research from ~2008 to ~2018. Brief summaries of publications from NASA, NASA-funded, and NASA-supported research are provided in 12 chapters: Acoustics, Aeromechanics, Computational Fluid Dynamics (External Flow), Experimental Methods, Flight Dynamics and Control, Drive Systems, Engines, Crashworthiness, Icing, Structures and Materials, Conceptual Design and System Analysis, and Mars Helicopter. We hope this report serves as a useful reference for future NASA vertical lift researchers

Industry/University Collaboration at the University of Michigan-Dearborn: A Focus on Relevant Technology

https://deepblue.lib.umich.edu/bitstream/2027.42/154104/1/kampfner1996.pd

NASA Tech Briefs, January 1989

Topics include: Electronic Components & and Circuits. Electronic Systems, A Physical Sciences, Materials, Computer Programs, Mechanics, Machinery, Fabrication Technology, Mathematics and Information Sciences, and Life Sciences