ai-aerospace/ams_data_full_2000-2020 huggingface dataset:
A point of interest is also the small spikes recorded at the end of each ON time (end of command pulses).  This reflects a transient motion of the rotor, moving between two different quasi-static equilibrium positions:  /g120During ON time and after completion of the rotor motion, the rotor position is the balance between  detent, electromagnetic and external torque /g120During OFF time, the rotor position is the balance between only the detent and the external  torque.  These locations are not identical and is one origin of the “CF” factor applied in the SMR formula Summary of the Predictions versus Measurements Figure 11. SN#61 Predictions vs Measurements /g11/g38/g82/g88/g85/g87/g72/g86/g92/g3/g82/g73/g3/g36/g86/g87/g85/g76/g88/g80/g12/g3 Figure 12. SN#54 Predictions vs Measurements /g11/g38/g82/g88/g85/g87/g72/g86/g92/g3/g82/g73/g3/g36/g86/g87/g85/g76/g88/g80/g12 Similar pendulum (gravity) tests are currently being conducted at MDA, the results of which will be  presented during the symposium 363
Conclusions The above examples are presented in an attempt to show that having the same motorization ratio  requirement across the board, regardless of several factors like available power vs. size, complexity, design maturity, heritage, knowledge of the system by the designers etc. is neither necessary nor the  most effective. In fact, requiring large motorization ratios for well characterized mechanisms might even  be detrimental as it could eliminate simpler, higher reliability mechanisms from future designs. The work presented relies on desig n heritage gained by MOOG and MDA, together with knowledge  acquired during various complementary test campaigns at MOOG, MDA and Astrium premises. It is  possible to highlight the following lessons learned: 1- Do not blindly apply generic requirements to your designs. Use judgment. The required  Motorization Ratio should depend on the design’s maturity, complexity and heritage. 2- Testing showed that during the powered portion of a pulse, whether the pulse is at 100% or at  any reduced duty cycle, the maximum torque will be identical.   3- These results indicate that the actuator torque during any powered portion of any reduced duty  cycle (as long as it is long enough (> 35 msec) for the rotor to step) pulse will be equal or greater  to the heritage actuator torque measured at 100% duty cycle.  4- For actuators driven with duty cycles lower than 100%, motorization margin computation methods  are proposed, sorting out carefully the two driving phases: during active part of the pulse (DMR  formula) and during the off part of the pulse (SMR  formula). These formulas aim at reflecting  accurately the physical behavior and properties of the actuator.   5- Based on test data conducted on several actuators at environmental extreme temperatures, Moog recommends using a 75% correction factor (CF in SMR formula) for worst-case prediction  of "static" torque using minimum motor detent torque. 6- Test results indicate that the minimum torque at reduced duty cycle, where the 0.75 CF applies, is  for operation at hot temperatures.  7- Finally, the proposed Motorization Ratio calculation aims at ensuring both a safe utilization of the  mechanisms and avoiding too much conservatism. Application of more conservatism could  jeopardize the ut ilization of effici ent solution (wrt to mass & heritage)  in particular for applications  requiring high torque capabilities. 364
Classification of Magnetic Gears Magnetic gears can be designed in configurations similar to conventional gears [8], mainly spur gears,  planetary gears and “harmonic drives”. Spur gears and planetary gears Direct spur gears consist of a pinion & wheel set with permanent magnets alternating their poles able to  magnetically engage. These poles are equivalent to the teeth in conventional gears. The characteristics of this sort of gears are greatly dependent on size, shape, materials and geometry. As in conventional  spur gears only moderate ratios can be achieved. Although useful for some applications, spur gears are  more useful when combined in planetary configurations to achieve high ratios with relatively low mass  and volume. Figure 1.  Model for a 1:2 Magnetic Spur Gear. Calculated Maximum torque: 24.2 N-m. Figure 2.  Model for a 1:5  Magnetic Planetary Gear. Calculated Maximum torque 32.0 N-m. 366
Table 1 shows a comparison of a magnetic planetary gear and a mechanical planetary gear. The data  shown for the planetary gear correspond to a general configuration not yet optimized. An optimization of parameters with a defined objective can typically improve greatly any of the characteristics.  Table 1.  Comparison of performan ces of a magnetic planetary gear vs.  a mechanical planetary gear.  Specification Magnetic Planetary Gear (not optimized)Mechanical planetary gear from  HD company Size 14 Reduction ratio (i) 4 5 Max output torque (N-m) 26 23 Torque Density (kN-m/m3)2 4 8 1 Max input speed (rpm) 1500 4000 Max Efficiency  (%) 95 - Mass (kg) 3 1.2 Envelope: Outer Diameter x Length (mm x mm)166 x 52 60 x 95 Max Operational Temp. (°C) 80 40 Min Operational Temp. (°C) - 40 0 Magdrives Another kind of magnetic gears can be obtained following a “Vernier motor” criteria similar to that of the  conventional “Harmonic drives”. We will call them “Magdrive” class. In fact the “harmonic drive” configuration was proposed by Chubb [9] for a magnetic gear some years before the invention of the “Harmonic drive”. Magdrives use a magnetic field wave whilst Harmonic drives use a mechanical  deformation wave.   Figure 3.  Model for 1:42 Magdrive. Magdrives are provided with a permanent magnet fixed to the input axle that generates a magnetic field  wave. This magnetic field induces a magnetization in a set of soft magnetic teeth which tend to align with an outer set of permanent magnets (or outer teeth). If the outer teeth are earthed, then the soft magnetic intermediate teeth are fixed to the output axle although other kinematic inversions are possible as well. This configuration can presumably provide ratios up to 1:200. 367
Figure 4.  1:21 Magdrive room temperature prototype and test bench. Max. torque 12 N-m    Figure 5.  1:21 Magdrive Cryogenic prototype with superconducting bearin g and test bench. A  perfectly cryogenic non-contact Magdrive. Max. torque 4 N-m, max speed 1500 rpm at 50-90 K.  Weight 7.5 kg. Envelope 130-mm diameter. Length 600 mm. Magdrives are suitable for cryogenic conditions. Particularly, a cryogenic Magdrive prototype, supported  on non-contact superconducting bearings has been developed. Table 2 summarizes experimental results for this (column 2) and other Magdrive prototypes comparing to some conventional Harmonic drives.  368
Table 2.  Comparison of experimental tests on Magdrive prototypes vs.  Harmonic drives data obtained from manufacturer. Specification MAGDRIVE Harmonic Drive Room  Temp. PrototypeCryogenic PrototypeMAG  SOARMD-50HFUC Size 17:  Only component without bearingsPMG Size 14:  including box Reduction ratio (i) 21 21 51 80 88 Max output torque (N-m) 15 4 45 43 12.7 Torque Density (kN-m/m3) 10.7 2.5 70 470 100 Max input speed (rpm) 500 1500 1500 1500 3000 Max Efficiency  (%) 95 - - Temperature  dependent.Temperature  dependent. Mass (kg) 5 8 2 0.3 0.5 Envelope: Outer Diameter x Length (mm x mm)120 x 110 120 x 400 100 x 80 60 x 32 50 x 80 Max. Operational Temp.(°C) 80 -180 +120 40 40 Min Operational Temp. (°C) -40 -260 -196 0 0 Torque limiters Other magnetomechanical devices that can be used for power transmission are magnetic torque limiters. They behave as 1:1 transmissions whenever the torque is under a limit. If the applied torque exceeds this limit they present an anti-jamming clutching effect that protects the output structure. Specific and  optimized designs make these devices quite compact and competitive. Figure 6. MAGSOAR TL-45  Magnetic Torque Limiter. Max. torque 45 N-m  Additionally, magnetic torque limiters provide a certain degree of torsional elasticity that can be used to  reduce the transmission of torsional vibrations. These magnetic torque limiters do not emit any kind of  magnetic field around them. They do not dissipate any kind of power while engaging (applied torque below limit). While not engaging (applied torque over limit) a reduced dragging torque and heat release can be customized. A main and unique feature of magnetic torque limiters is that they do not suffer wear or fatigue  independently of the times they act limiting the torque.   Table 3 shows a comparison between experimental data of a magnetic torque limiter and data from the  manufacturer of a mechanical torque limiter.  369
Table 3. Comparison of a Magnetic torque limiter  TL-45 manufactured by MAG SOAR SL and a  KTR 01 2TFmechanical torque limiter manufactured by Ruflex. Specification MAGSOAR  TL-45Ruflex  KTR 01 2TF Reduction ratio (i) 1 1 Max output torque (N-m) 45 10-70 Torque Density (kN-m/m3) 100 52-300 Max input speed (rpm) 15000 6000 Max Efficiency  (%) 95 - Mass (kg) 2 - Envelope: Outer Diameter x Length (mm x mm)135 x 40 68 x 52 Max Operational Temp. (°C) 80 80 Min Operational Temp. (°C) -40 -20 Torque and Torsional Stiffness in Magnetic Gears The most outstanding properties of magnetic gears are derived from the torque/torsion behavior. It is  radically different from that of the conventional gears. If we block the output axle of a gear and increase the torque in the input axle to try to move it we will make evident the difference between magnetic and  mechanical gears.  Magnetic gears will admit a shift angle in the input axle that increases linearly with the applied torque.  Figure 7 shows experimental data of torque vs. shift angle for a 1:21 Magdrive (black dots). If we decrease the torque and change the sign of it, the angle will follow the torque without any significant hysteresis. In this sense magnetic gears do have zero backlash. If we increase the torque up to its maximum value, a non-linear dependence appears. If we try to increase the torque and pass the limit,  then the axle simply turns. For the magnetic gears nothing breaks down. The case is quite different in conventional gears (blue line in Fig. 7). A backlash is present due to the  clearances needed for the movement. Therefore, if the movement is reversed there is a small but not  negligible backlash around the origin. Once the gears are engaging, then the input axle presents a rigid  behavior with stiffness on the order of magnitude of the flexural stiffness of the teeth. Once the maximum  applied torque is reached, a plastic deformation and fracture appears with permanent damage of the conventional gear. The radically different behavior of magnetic and mechanical gears makes the meaning of “maximum  applied torque” to be quite distinct. For mechanical gears it means “if you exceed that value you break the  device”. For magnetic gears it means “it will transmit the movement up to that value of the torque, but if you try to exceed it, it will slide and nothing breaks down”. Non-contact and elasticity of magnetic gears make magnetic gears natural isolators for vibrations.  Figure 8 shows axial vibrations measured on a bearing supporting the input axle of a 1:21 Magdrive and the corresponding vibrations measured on the bearing supporting the output axle. Damping is evident. 370
Figure 7.  Experimental Torque vs. angle shift in MAGDRIVE Room Temperature Prototype (black  dots) compared to a perfect mechanical gear (b lue line). Magnetic gears do not present backlash  but a linear dependence around the cero point. Magnetic gears, unlike mechanical ones, do not  present damage if the torque overpasses the maximum.  Figure 8. a) Transversal Acceleration on a bearing supporting the input axle of a 1:21 Magdrive when vibrations are induced on it. b) Transv ersal Acceleration on the bearing supporting the  output axle of the same system.  371
Conclusions  Magnetic gears are becoming competitive alternatives to conventional gears. They present no contact  and no wear. They do not produce debris and they do not require lubricant, being able to be operated at a broad range of temperature ranging from -270ºC up to 350ºC. They present intrinsic anti-jamming  properties and there is a clutching effect if the applied torque exceeds a limit therefore protecting the  output from overloads. This effect is completely reversible without any damage or wear. The TRL of this  technology is currently increasing making it available for consideration for aerospace uses.  The radically different behavior against torque overloads, the isolation of vibrations, the absence of  maintenance, the compatibility with sand or dust, broad temperature range and the through wall capability are some properties that make these devices attractive for aerospace. Table 4 summarizes the state of the art of magnetic gears and torque limiters with a qualitative  comparison of magnetic torque limiters, magnetic planetary gears and magdrives with respect to their  best available mechanical equivalents. For the elaboration of Table 4, the authors have developed  original software able to interpolate current-state data of magnetic gears. The user can select the ratio, speed and some other parameters. The software provides maximum torque, size, weight and even an  estimation of the cost of the magnets for a magnetic spur gear, a magnetic planetary gear and a Magdrive.  372
References 1.  C. Cristache, I. Valiente-Blanco, E. Diez-Jimenez, M.A. Alvarez Valenzuela, N. Pato and J.L. PerezDiaz; “Mechanical characterization of journal superconducting magnetic bearings: stiffness,hysteresis and force relaxation”, Journal of Physics: Conference Series EUCAS, (2013). IEEE  Council on Superconductivity Best contributed EUCAS 2013 Award: Mechanical characterization of  journal superconducting magnetic bearings: stiffness, hysteresis and force relaxation.  2.  I.Valiente-Blanco, E. Díez-Jiménez, Cristian Cristache, Marco A. Álvarez-Valenzuela and J.L. PérezDíaz, “Characterization and Improvement of Axial and Radial Stiffness of Contactless Thrust  Superconducting Magnetic Bearings”, Tribology Letters, (2013). 3.  J.L. Pérez-Díaz, I. Valiente-Blanco, E. Díez-Jiménez, and J. Sanchez García-Casarrubios,  “Superconducting Noncontact Device for Precision Positioning in Cryogenic Environments,” IEEE/ASME Transaction on Mechatronics, (2013). 4.  Pérez-Diaz, J.L.; Valiente-Blanco,I., et al., “Contactless Superconducting Magnetic Instrument for  Precise Positioning in Cryogenic Environments”, Proceedings of ASME International Mechanical  Engineering Congress & Exposition, San Diego, E.E.U.U, (2013).  5. Perez-Diaz, J.L.; Diez-Jimenez, E., Valiente-Blanco, I. et al., “Magnetic Non-Contact Harmonic Drive”,  Proceedings of ASME International Mechanical Engineering Congress & Exposition, San Diego, USA, (2013).  6. Valiente-Blanco I., Cristache C., Diez-Jimenez, E., Alvarez-Valenzuela M.A., Sanchez-GarciaCasarrubios J. and Perez-Diaz, J. L (2013) Characterization and improvement of axial and radial  stiffness of contactless thrust superconducting magnetic bearings, 5th World Tribology Congress, Torino, Italia, (2013).  7. Cristache C., Diez-Jimenez, E., Valiente-Blanco I., Alvarez-Valenzuela M.A, Sanchez-GarciaCasarrubios J. and Perez-Diaz, J. L.; Levitation force relaxation and hysteresis in a frictionless  superconducting magnetic bearing, VII Iberian Conference on Tribology, Porto, Portugal, (2013).  8. X. Li, K.-T Chau, M. Cheng and W. Hua ; « Comparison of Magnetic-Geared permanent-magnet  machines », Prog. In Elec. Res., 133, 177-198 (2013) 9.    L.W. Chubb,  "Vernier Motor", US Patent 1894979, (1933). 374
Primer – Stepper Motor Nomenclatu re, Definition, Performance and  Recommended Test Methods Scott Starin*and Cutter Shea* Abstract There has been an unfortunate lack of standardization of the terms and components of stepper motor  performance, requirements definition, application of torque margin and implementation of test methods.  This paper will address these inconsistencies and discuss in detail the implications of performance parameters, affects of load inertia, control electronics, operational resonances and recommended test  methods. Additionally, this paper will recommend parameters for defining and specifying stepper motor  actuators. A useful description of terms as well as consolidated equations and recommended requirements is included.  Introduction Stepper Motor Actuators are desired in space mechanisms because of their precise incremental control, yet they are inherently under-damped and susceptible to inertial mismatch. These issues will be  addressed in detail. While linear straight-line approximation of Stepper Motor performance may be  simulated with simple relationships and equations, actual performance in a system with inertia, friction, and compliance may result in dramatically different performance compared to simulations. Often, performance requirements in specifications do not fully reflect the actual requirements, including torque margin. More importantly, an inadequately designed test set-up or incomplete testing could erroneously  hide a latent performance issue that may not be identified until the actuator is integrated at a higher assembly. Linear Performance Approximation There are many factors that contribute to the actual dynamic performance of a stepper motor actuator. Simple linear extrapolation, however, yields conservative results that works for the vast majority of applications. The linear approximation may be obtained by determining key motor parameters, which are included in most motor manufacturers’ catalogs. For our example, Table 1 delineates the key parameters and values used in our example.  Table 1. Key Motor Parameters  Parameter Units Symbol Value Motor Constant (NonRedundant) mN-/g80/g18/g165/g3/g58/g68/g87/g87 K M 34 Motor Inertia kg-m2JM 7.06E-07 Step Angle at Motor Degrees/step /g507/g537 M 30 Simplex No Load Response  Rate Constant /g53/g51/g48/g18/g165/g58/g68/g87/g87 K RR 325 Motor Bearing Friction (-20º C) mN-m f BM 1.0 Magnetic Coulomb Torque mN-m f CM 5.0 *Avior Control Technologies, Inc., Longmont, CO /g51/g85/g82/g70/g72/g72/g71/g76/g81/g74/g86/g3/g82/g73/g3/g87/g75/g72/g3/g23/g21/g81/g71/g3/g36/g72/g85/g82/g86/g83/g68/g70/g72/g3/g48/g72/g70/g75/g68/g81/g76/g86/g80/g86/g3/g54/g92/g80/g83/g82/g86/g76/g88/g80/g15/g3/g49/g36/g54/g36/g3/g42/g82/g71/g71/g68/g85 /g71/g3/g54/g83/g68/g70/g72/g3/g41/g79/g76/g74/g75/g87/g3/g38/g72/g81/g87/g72/g85/g15/g3/g48/g68/g92/g3/g20/g23/g16/g20/g25/g15/g3/g21/g19/g20/g23/g3 375
Figure 1, graphs a linear simulation of a geared Stepper Motor Actuator at room temperature and at  +50º C. The figure points out key performance parameters and introduces some nomenclature that will be  used throughout the paper.   Figure 1.  Linear Simulation of Geared Stepper Motor  The designated operating point “ATP Requirement” refers to the required Torque margin requirements, as  defined in GSFC-STD-7000 (GEVS) [2]. This will be discussed in detail later in the paper.  Inertia Factor Calculations Perhaps one of the most important parameters in the utilization of Stepper Motor Actuators is determining  the /g44/g81/g72/g85/g87/g76/g68/g3/g41/g68/g70/g87/g82/g85/g3/g11/g45 /g41/g12. This parameter is the sum of the load inertia reflected to the motor (J LM), and the  motor inertia (J M), all divided by the motor inertia:  /g1836/g3007=/g3011/g3261/g3262/g2878/g3011/g3262 /g3011/g3262……………………………………..…………………(1)  Where J LMis the load inertia (J L), divided by the entire gear ratio (N), squared.  /g1836/g3013/g3014= /g3011/g3261 /g3015/g3118………………………………..…………………………(2)  Many times, the gear ratio is determined by the step resolution required at the system level, but the  driving factor may also be reducing the Inertia Factor. There are several schools of thought on what is an  acceptable Inertia Factor. Some engineers insist on an Inertia Factor less than or equal to 2.0 (That is J LM /g4150 JM). While a /g45/g41less than 2.0 is conservative, there are times this may be impractical. A maximum  376
/g2007 /g2870/g2873= /g2870/g1669 /g3023/g3118 /g3017/g3257/g3118/g3121 ……………………………………………(6) Where “V” is the supply voltage. In our example, this yields a nominal motor resistance of 48.3 ohms per  phase. Use Equation 7 to calculate the DC resistance at temperatures other than 25º C (t 2). /g2007/g1872/g2870= /g2007 /g2870/g2873  [1 + .004 (/g1872/g2870/g33982 5 )] ……………………………….(7) Knowing the change in resistance at any temperature allows the change in current and power to be  calculated. Thus allowing the Torque at Low Pulse Rate and Inertia factored Response Rate to be determined at temperature. Calculations are detailed in Appendix A. Equation 7 works while analyzing the system is increasing or decreasing temperatures, within limited  temperature ranges. Exercise caution when going down in temperature. Colder temperatures could yield  higher viscosity in a wet lubrication system and will affect available torque calculations. Avior has modeled multiple wet lubrication options and introduced a functional component of bearing friction (f BM) that accounts for the increased viscosity at colder temperatures. This method is recommended for accurate performance models. Additionally, the relationship of Equation 7 does not work down to cryogenic temperatures where the purity of the copper must be factored.   Actual Dynamic Performance (What Really Happens) As mentioned, the linear approximation provides a conservative estimate for most applications. Figure 2  shows an empirical test of the Pull-In Torque of the geared stepper motor for the example. It is extremely important to realize that the characteristic oscillations of the dynamic performance will be unique to the test set-up and drive electronics. If high stiffness couplings were replaced with more compliant couplings,  the characteristics could dramatically change. The portions of dynamic torque that increase and decrease  will be exaggerated with lower compliance, reduced damping, or increased load inertia.   378