ai-aerospace/ams_data_full_2000-2020 huggingface dataset:
From the design point of view, new generation design tools such as topology optimization software could  lead to interesting results. With their capacity to minimize or control the effects associated with the  thermal history of the parts, the emergence of AM process simulation tools should also contribute to  improve the design of the parts. But all these software tools are only complementary to the understanding  of the designer which needs to be aware of the possibilities and limitations offered by Additive  Manufacturing.  The present study demonstrates how the most critical steps related to Additive Manufacturing of highprecision and compliant mechanisms were addressed, starting from the specific mechanical design,  followed by the definition of the Additive Manufacturing and post-processing strategies and concluded  with the validation strategy. This approach has led to the successful redesign of a space slipring rotor and  will continue with other products.  The near future work is to design and built more demonstrators integrating all the developments achieved  over these last few years, especially in the frame of a development project for the European Space  Agency.   References  1. Merriam, Ezekiel G., Stiffness Reduction Strategies for Additively Manufactured Compliant Mechanisms, All Theses and Dissertations. Paper 5873, 2016. 2. ECSS, Material selection for controlling stress-corrosion cracking, ECSS-Q-ST-70-36C, 2009. 3. The Boeing Company – Vertol Division, Fatigue Properties of 17-4 PH and 15-5 PH Steel in the H-900 and H-1050 Condition, Report D8-1038, 1969. 4. US Department of Defence, Metallic Materials and Elements for Aerospace Vehicle Structures, MILHDBK-5H, 1998. NASA/CP—2018-219887 245
1) Fuse Wire Burnout time (FWBO): This is the time from application of current to fuse wire burnout. This time is primarily dependent on input current – the higher the input current, the faster the fuse wire burn time. 2) Preload Drop time: Time from fuse wire burnout to when the restraining wire uncoils sufficiently to drop the system preload to zero and allow the release rod to start exiting the NEA. Figure 1. Example of Typical NEA Actuation Time Curve  There were two distinct series of testing performed as part of Phase 1 of the NEA Multi-point Separation  Testing. Series I consisted of testing with a 4-point release test plate using a break-link to measure actuation  time. Series II consisted of testing performed with units actuated individually using a load cell to measure  actuation time.  Series I – Four-Point Release Testing  Series I - Test Setup and Plan  Series I testing consisted of two sub-series of tests where preload and firing current were adjusted. Each  sub-series test consists of data from each of the 4 NEA’s actuated during that test, for a total of 28 data  points (see Table 1)  Table 1. Series I Test Plan  This initial series of tests were conducted using an NEA model SSD9102J, an M6-sized HDRM with an  integral 60-degree cup/cone interface and retraction spring. Four NEA’s were affixed to the corners of two  610-mm (24-inch) square aluminum plates; each plate being 19-mm (0.75-inch) thick and weighing NASA/CP—2018-219887 248
approximately 177 N (40 lbf). The aluminum plates were suspended in a frame so that the plates were  parallel to the ground. Application of the actuation current activates the NEA’s and allows the bottom plate  to fall and separate from the top plate with gravity providing the separation force (see Figure 2).  Figure 2. Test Setup  A multi-channel Synergy Data Acquisition System was used to capture Fuse Wire Burnout time and Preload  Drop Time. Because load cells could not be installed directly into the NEA assembly for this configuration,  a “break link” was used to estimate the Preload Drop Time. This break link consists of a piece of lead fixed  in proximity to the release rod exit path – once the preload dropped and the release rod begins to move, it  breaks the “break link” and a signal is shown on the data acquisition system.  Figure 3. Break Link Setup  Series I - Test Results  Figure 4 and Figure 5 shows that overall actuation time is primarily influenced by the input firing current. As  the current increases, the actuation time decreases significantly (Figure 4). It also reveals that preload does  not significantly influence actuation time as shown with the significant overlap in individual actuation time  data points (Figure 5).   Figure 6 shows that the reason input current is the primary influence on Actuation Time is because of its  effect on Fuse Wire Burnout Time – higher input current reduces the magnitude and variation in Fuse Wire  Burnout Time. Figure 6 also shows Preload Drop Time is independent of input current.  Figure 7 summarizes the effects of input current to the Simultaneity Range of each test - the range of  actuation time for each test between the 4 NEA’s was determined and sorted by input current. This data  shows the simultaneity between 4 NEA actuated together improves significantly with increasing input  current, with a max simultaneity range of 5.1 ms.  NASA/CP—2018-219887 249
Figure 4. Actuation Time vs Current  Figure 5. Actuation Time vs Preload  Figure 6. FWBO/Preload Drop vs Current    Figure 7. Simultaneity Range/Test vs Current  Series I testing was an excellent start to better understanding the simultaneous capability of our  mechanism, but the lack of direct preload data and concern that some of the variance could be caused by  the test setup led our team to the next series of testing.   Series II – Individual Release Testing  Series II – Test Setup and Plan  Similar actuation testing parameters were used as in Series I, but the units were tested individually and  with a load cell in-line. This allowed us to understand the true preload drop time of the NEA, compare it to  the break-link data above, and isolate the internal NEA dynamics from the effects of the 4-point test plate  setup. The team also decided to add some additional factors to understand if the units behaved consistently  across different assembly operators and over several build lots. Table 2 summarizes the test plan for   Series II. Figure 8 provides a schematic of the test setup used.  NASA/CP—2018-219887 250
Table 2. Series II Test Plan  Figure 8 - Series II Test Setup Schematic  Series II - Test Results  All testing under Series II used the same input current since the factors affected by the input current were  already understood from Series I testing. Figure 9 shows that the actuation time is still primarily unaffected  by the preload, similar to Series I testing.   Comparing the Series I and Series II data, there are a few key insights to highlight. The first is the difference  between the break-link signal (Series I) and the preload drop time (Series II) – see Figure 10. On average,  the preload drop time was 9.8 ms faster than the break-link signal. This is expected since sufficient  movement of the release rod after preload release is required to fracture the break-link assembly. This extra  movement, and the act of breaking the lead, adds variation which leads to the second key difference in the  data. Firing Current Preload Assembly Technician (A or B) Test II.1 7.0 Amps 11.6 kN (2,600 lbf) A Test II.2 7.0 Amps 17.8 kN (4,000 lbf) A Test II.3 7.0 Amps 17.8 kN (4,000 lbf) A Test II.4 7.0 Amps 17.8 kN (4,000 lbf) B Each test series represents a different build lot 8 actuation data points are collected for each test series above NASA/CP—2018-219887 251
Figure 9. Series II Actuation Time vs Preload  The second significant difference between Series I and II, is the reduction in actuation time variation of  37%, from 5.50 ms to 3.46 ms (Figure 11 shows all data compared at 17.8 kN). This reduction in variation  can be attributed to the elimination of variables in the test setup. The test setup in Series II is much more  simplified, focusing primarily on the NEA capability itself. Now that the NEA variance in actuation time is  understood – which has shown that it can meet a 5-ms simultaneity requirement – the next phase of testing  can be centered around building a more flight-like test setup to validate the system.   Figure 10. Series I (break-link) vs Series II (load cell) Actuation Time  NASA/CP—2018-219887 252
Figure 11. Series I (break-link) vs Series II (load cell) Actuation Time Variation  Conclusions & Lessons Learned  Phase 1 of the NEA Multi-point Separation Testing completed shows the NEA’s actuation time capability  can meet a simultaneity requirement of 5 ms or less, even across different build lots and different assembly  technicians.   Although several lessons were learned during the scope of this testing, the ones of most interest and  importance is the dependence of input current on actuation time simultaneity (higher current improves the  simultaneity behavior because of reduced fuse wire burn-time variation) and conversely, the independence  of preload on simultaneity.  NEA Multi-point Separation Testing Phase 2 has also begun. During this phase, NEA plans to incorporate  a more flight-like setup thru cooperation with potential customers, and create a reliable analytical model  predicting spacecraft trajectory and tip-off using this empirical data. This data will be ready later this year.  NASA/CP—2018-219887 253
Validation of a Novel High Performance Magnetic Gearbox for Space  Ignacio Valiente-Blanco*, Judit Esnoz-Larraya*, Efrén Diez-Jimenez**, Juan Sanchez GarcíaCasarrubios*, Cristian Cristache*, Fernando Rodriguez-Celis* and José Luis Perez-Diaz**  Abstract  In this paper, experimental validation of a novel high-performance magnetic gearbox for space applications,  developed within the ESA ITI program is presented. This lubricant-free gearbox is manufactured using  SmCo magnets, with a well know space heritage [1] and provides an unprecedented torque density for this  sort of device (92.3 kNm/m3, 15.4 Nm/kg). A high efficiency in an extended temperature range (up to 92%  at -40ºC and 500 rpm) has also been demonstrated, showing a potential advantage of the technology for  application in cryogenic environments [2]. Accuracy, zero backlash performance, and magnetic  contamination are also investigated.  Introduction and State of the Art  The working principle of a magnetic gear (MG) is similar to a mechanical gearbox. However, teeth are  replaced by permanent magnets so torque and speed conversion are produced by a modulated magnetic  field [3]. Power is transmitted without contact, therefore, lubrication is not needed; the lack of contact  eliminates wear and debris generation and potentially increases lifetime. They are also able to operate in a  wider temperature range temperature range from -200ºC to 300ºC. Finally there is no backlash, which  represents a potential advantage for accuracy applications [4] [5]. Additionally, MGs provide vibration  isolation between the motor and the payload and its inherent overload protection mechanism prevents  against potential catastrophic failures [6].  Despite all these advantages, up to now the technology has shown a low level of maturity and the developed  demonstrators are frequently heavy, present low torque capability, reduction ratios typically below 6, and  sometimes poor efficiency [7]. Magnetic pollution levels of previous breadboard models are significantly  high and not compliant with ECSS space standards [8]. In addition, MGs are usually manufactured using  NdFe magnets which are known to present several drawbacks for their use in space environments [9].  Figure 1 shows a summary of the state-of-art of this technology dividing between SmCo and NdFe magnetic  gearboxes. Model D57r10 is the gearbox described in this paper.  Figure 1. Summary of the state of the art of Magnetic Gearboxes  *MAG SOAR SL. Valdemoro, Spain ** Universidad de Alcalá, Alcalá de Henares, Spain Proceedings of the 44th Aerospace Mechanisms Symposium, NASA Glenn Research Center, May 16-18, 2018  Number Author 1 Tsurumoto 1987 [10]  2 Fujita 2013 [11]  3 Iwasaki 2016[12]  4 Atallah 2004[13]  5 Penzkofer 2014 [14]  6 Uppalapati 2014[15]  7 Brönn 2010[16]  8 Pérez-Díaz 2013[17]  9 Jorgensen 2008 [18]  10 Kikuchi 1993[19]  NASA/CP—2018-219887 255
The Innovation  In this paper, experimental validation of magnetic gear in a controlled laboratory environment is provided.  The MG is made of SmCo magnets with known space heritage. A high torque capability, a reduction ratio  of 1:10 and low magnetic pollution levels according to ECSS standards were demonstrated. A high  efficiency up to 92% at 500 rpm and -40ºC is one of the strongest points of the technology. The elimination  of contact allows the optimization of power transmission in terms of efficiency. This provides the opportunity  of high weight savings in motor-gear assemblies at low temperatures where the use of solid lubrication  highly limits the efficiency and torque capacity of the systems. The performance demonstrated by this MG  is far superior to the current state of the art of the technology and opens the window for several potential  applications in space.   Model Description  The magnetic gearbox presented in this paper is composed of three main elements: an input rotor (1), an  output rotor (2) and a stator (3) as shown in Figure 2. Input rotor and stator are mainly composed of SmCo  XYG 32 permanent magnets while the output rotor is mainly composed of laminated soft magnetic alloy  teeth. Magnets in the stator are arranged in a Halbach configuration to maximize magnetic flux density  inside the gearbox. 72 magnets are used in the stator, with 18 soft magnetic teeth and 4 input magnets.  According to the reduction ratio calculation formula [20], the reduction ratio of the gearbox presented in this  paper is equal to 10.   Four ball bearings are used to support the radial loads (theoretically spurious) during operation and to allow  relative motion between the moving parts and the stator of the device. The selected bearings were  lubricated with low-temperature grease. Titanium grade 2 alloy has been used as structural material for the  housing, flanges and internal parts of the gearbox to obtain a good structural performance with a reduced  mass penalty. The relatively high electric resistivity of titanium also contributes to an improvement of the  efficiency of the gearbox at high speeds. Standard mechanical interface flanges have been designed. Fig.  2 shows the magnetic gearbox after assembly and the summary of the main physical properties and  performance specifications:  Figure 2. Assembled gearbox and summary characteristics  Test Set Up and Results  A dedicated test bench was set up to accurately characterize the breadboard model under different  temperature conditions from -40ºC to 70ºC, speeds and load conditions from 0 to 100% output load (lock  situation). Functional characterization tests were conducted, including static and dynamic performance,  temperature influence, gear ratio, transmission error, backlash, and efficiency and magnetic field  contamination.   NASA/CP—2018-219887 256
Figure 3. Dedicated test bench and a view of frozen model after -40ºC test  Maximum Output Torque vs. Temperature  To evaluate the maximum output torque capacity of the gearbox, an infinite impedance is set at the output  shaft (braking torque significantly higher than the maximum expected torque in the gearbox). Then, the  input shaft is rotated slowly until slip occurs. The process is repeated 10 times in CW and CCW directions  to have a statistical characterization. The maximum output torque measured at different operational  temperature is depicted in Fig. 4 and compared to magneto-static FEM calculations. Results are in good  agreement with the simulation models.  Figure 4. Maximum output torque vs temperature characterization  Maximum output torque at 25ºC is 17.8±0.1 Nm. It is clear that the maximum output torque increases at  low temperatures. A temperature sensitivity about -0.012 Nm/deg has been calculated. The measured value  of maximum output torque provides an actual torque density of 92.3 kNm/m3 and actual specific torque  15.4 Nm/kg at room temperature. The actual torque density is different from active torque density.  NASA/CP—2018-219887 257
Meanwhile the active torque density considers only the magnetic parts, the actual torque density considers  the whole volume of the device (bearings, shields, etc). Taking into account the material used (SmCo), the  gear ratio and the active torque density obtained, these results provide a significant improvement of the  previous state of the art [21].  Reduction Ratio  Kinematic reduction ratio is evaluated in dynamic conditions for various operational speeds between 50  and 1000 rpm, different load conditions and temperatures. Figure 5 shows a typical speed profile for the  kinematic reduction ratio characterization test.   Figure 5. Test bench and three breadboard models  The overall reduction ratio has been calculated at about 10±0.01 with no significant dependency on the  operational speed, load condition, or temperature.   Transmission Error  Transmission error of a gearbox is defined as:  =  −  where    is the angle measured in the output shaft.   is the angle measured in the input shaft.  r is the theoretical gearbox reduction ratio, r=10.   The transmission error has been calculated at different speeds, load conditions and temperatures. Fig. 6  shows, as an example, the transmission error measured at 5 rpm, zero load condition, and room  temperature. Two main contributions to the transmission error have been found at about 2 and 9.2 output  degrees. Average RMS values of the transmission error under different load and temperature conditions  are calculated at about 290 arcsec. The same value was obtained under different temperatures and  operational conditions. The fact that the contribution to the transmission error can be deterministically  defined opens new opportunities to highly improve the accuracy of the gearbox by motor active control.     NASA/CP—2018-219887 258
Figure 6. Transmission error and FFT amplitude  Backlash  Backlash was also characterized for the magnetic gearbox. Reciprocating quasi-static motion of low  amplitude (from 1 to 10 deg) is induced in the input shaft. Then, the output rotation is observed and backlash  characterized. The experiment was repeated at various temperature conditions and different input relative  positions. The backlash observed was always below the DAQ system resolution (<20 arcsec).   Efficiency  The efficiency of the magnetic gearbox has been characterized at different operational conditions. In this  paper, results at different speeds and temperature for an output load of 50% of the maximum output load  are presented. Fig. 7 shows the efficiency measured at different temperatures and compared with FEM  results. Both values are in relatively good agreement. Efficiency obtained from experimental data presents  error bars up to 10% at low speeds due to test set up limitations. To improve the readability of the data,  error bars were not plotted on graph. Efficiency seems to remain higher than 90% even at low temperature;  this is one of the main strengths of the technology. On the contrary, mechanical gearboxes are highly  affected by cold temperatures, with efficiency of solid lubricated gears rapidly reduced to 10% at -25ºC [22]. Figure 7. Efficiency test results at different temperatures  Magnetic Pollution  A critical parameter for instruments used in space is the magnetic contamination induced in the  surroundings. Frequently, scientific missions and on-board instruments require very low magnetic  contamination to assure that there is no interference with the satellite instruments. Scant attention has been  NASA/CP—2018-219887 259
paid to this critical issue in the past regarding magnetic gearboxes. Space standards establish that an  acceptable limit for magnetic contamination is a value of 0.2 µT at 1-meter distance from the device.  Fig. 8 shows the magnetic field contamination in the most unfavorable direction (radial) from the gearbox  vs. distance to the gearbox. A very good agreement with FEM results is observed. The measured magnetic  flux density at 1-meter distance is extrapolated from the FEM model of the gearbox. The value obtained is  equal to 0.15 µT, below ECSS limits. The equivalent dipolar moment calculated at 1-meter distance is about  1±0.2 A/m2.   Figure 8. Efficiency and magnetic pollution test results  Conclusions and Lessons Learned  A high-performance breadboard model of a magnetic gearbox has been designed for space applications,  manufactured and tested. The breadboard model demonstrated a reduction ratio of 10, with an  unprecedented actual torque density (92 kNm/m3, 15.4 Nm/kg), high efficiency for operation even at low  temperatures (92% at -40ºC and 500 rpm), and magnetic pollution levels compliant with ECSS requirement  specifications. The results obtained showed a significant improvement in term of torque density and gear  ratio compared to previous developments and prove that MGs are competitive against mechanical  gearboxes.   During the project, the lessons learned are:  •High efficiency can be achieved for operation even at low temperatures by common techniques such as soft magnetic material lamination or selection of low conductivity materials. •Efficiency and torque capacity are little affected by the environment temperature •Sources of inaccuracy can be well predicted by FEM models. The deterministic nature of these errors allows multiple strategies to improve the accuracy and reduce the ripple. •Magnetic pollution level is below ECSS standard requirements. Acknowledgements and Previous Publication Record  This project was founded by ESA, under the contract number Nº 4000113972/15/NLCBi/GM ITI activity. A  general view of the three breadboard models developed under this activity was summarized in ESMATS  proceedings 2017 [9]. This paper present original information and tests results never published before NASA/CP—2018-219887 260