ai-aerospace/ams_data_full_2000-2020 huggingface dataset:
Figure 2. Empirical Dynamic Performance versus Linear Simulation  Why This Happens The inherent kinematics of a stepper motor mirrors an under-damped step function of a servo system. As  the stepper motor moves to each stable step point, there is overshoot of position. Also note that as the  motor crosses each step point, the angular velocity, and therefore the kinetic energy, is at a maximum. Even when stepper motors are driven at low pulse rates, the instantaneous angular velocity can beextremely high at these crossover points. The cardinal oscillatory frequencies of these overshoots will result in an increase in torque at some step rates (Cardinal-Maxima), and a reduction of torque at other  step rates (Cardinal-Minima). As the Inertia Factor increases, the variation of the torque peaks and  valleys will be exaggerated. When the Inertia Factor is greater than 5.0, it is recommended that additional  margin be applied from the linear performance assumption before a system prototype has been tested.   There are several important aspects to take into account, considering these phenomena. The  characteristic cardinal torque step rates will vary with test set inertia, drive electronics and coupling compliance. This is why it is recommend the drive electronics and test set configuration simulate the actual system parameters as closely as practical. Additionally, performance at multiple step rates shouldbe conducted to verify that dynamic torque performance is not conditionally marginal. In other words, during a test, the system may be at a cardinal torque increase point. If you test multiple step rates around the system operating step rate, you may better characterize the performance. It is important to realize thatmore torque is not necessarily better. Torque margin is desirable, but increasing torque may actually  increase kinematic overshoot and further exaggerate the dynamic cardinal torque variations.   Determining the damping ratio of a Stepper Motor system can be an excellent indicator for susceptibility  of a system to extreme cardinal exaggerations. From actual test data, Figures 3 and 4 show the same system with two actuators with different drive methods and /g71/g68/g80/g83/g76/g81/g74/g3/g85/g68/g87/g76/g82/g86/g3/g11/g535/g12/g17/g3The total inertia, inertia  379
/g1839/g1867/g1845 =  /g3021/g3265/g3265/g3268_/g3250 /g3021/g3265/g3265/g3268_/g3262/g3284/g3289/g33981………………………………………(11)  Properly Specifying a Stepper Motor Actuator Perhaps the most important aspect of selecting and integrating a geared stepper motor actuator into a  system is properly defining and testing the product. This may sound obvious, but many specifications for  these products fall short of the goal. A properly specified actuator should specify the components of loading and electro-magnetically generated torque components for the load (system) side as well as the  actuator side. Using the example, Tables 4 and 5 delineate the components, values and tolerances.   Table 4. System Level Parameters (+25º C Unless Specified) Parameter Units Symbol Value Tolerance Margin  Type Load Inertia kg-m2JL 5.7E-04 Nominal Kc Load Friction N-m F L 0.294 Nominal Kv Dynamic Velocity at Load Degrees/sec /g550 L 90 Nominal - Maximum System Temperature ºC t max +50º Max - Minimum System Temperature ºC t min -20º Min - Maximum Supply Voltage VDC V max 34 Max - Minimum Supply Voltage VDC V min 24 Min - System Step ResolutionDegrees/Step /g507/g537 A 1.5 Min - Radians/Step /g507/g537 A 0.02618 Min - Unpowered Holding Torque N-m T BD 0.08 Min - Of course there are many other requirements that contribute to an aerospace quality component, but  presenting the nominal system characteristics are the first step in deriving the requirements for the actuator that will drive that system. From the System Level Parameters, defined in Table 4, simulation is  used to determine the requirements for the actuator, using the Torque Margin Requirements and methods discussed above. It is important to communicate the NOMINAL values for the torque contributing parameters because otherwise, margin will be applied on top of margin. When calculating worst-case conditions, an application may be over-powering the actuator unnecessarily, or forcing a larger actuator frame size than need be.  Table 5 delineates the derived Actuator parameters, broken down to the components and composite  assembly level. As with the System Level Parameters, the contributing components of torque and  applicable type of margin is utilized for those factors. Additionally, verification method using conventional  (A) Analysis, (D) Demonstration, (I) Inspection, (S) Similarity and (T) Test is provided. Table 5. Actuator Level Paramete rs (+25º C Unless Specified) Parameter Units Symbol Value Tolerance Margin  TypeVerification  Method Motor Performance Motor Inertia kg-m2JM 7.06E-07 Nominal - A Bearing Friction Torque (at -20ºC)mN-m f BM 1.0 Max Kv D, S Magnetic Coulomb Torque mN-m f CM 5.0 Max Kc D, S Composite Motor Friction  Torques ( See Note 1 )mN-m f TM 6.0 Max - T Rated Pulse RatePulses  per sec PPS 60 Nominal - A 383
Table 5. Actuator Level Paramete rs (+25º C Unless Specified) Parameter Units Symbol Value Tolerance Margin  TypeVerification  Method DC Resistance Per Phase Ohms /g525 25 50 ±10% - T Motor Inductance Per Phase Henries L 0.025 ±10% - T Torque Constant Per PhasemNm/AmpKT 240 Min - T Back emf Constant Per  PhaseV/Rad/sec K B 0.24 Nominal - T Rated Minimum Current Per  Phase (See Note 3)ADC Imin 0.436 Ref - A Holding torque at Rated ADC  Per PhasemN-m T H25 0.135 Min - T No Load Response RatePPS RR M 275 Min - T Deg/Sec RR M 8250 Min - T Motor Winding (Simplex or  Redundant)-- Simplex -- A ,  I Gearbox Performance Gearbox Ratio - N 20 Nominal - A, D Fore-driving Friction mN-m F BG 2.0 Max Kv T Gearbox Dynamic Efficiency % n G 90 Min Kc D, S Gearbox Torsional Stiffness N-m/Rad K G 1000 Reference - D, S Gearbox Backlash Degrees /g537 BL 0.10 Max - I Output Shaft Axial Play mm/kg /g537 BA 0.05 Max I Output Shaft Radial Play  (measured at shaft end)mm/kg /g537 BR 0.05 Max I Composite Actuator Performance (Performance at Minimum Supply Voltage)  No Load Response RatePPS RR A 275 Min - T Deg/sec RR A 412 Min - T Rated Load Inertia for  Dynamic Testingkg-m2JL 5.7E-04 Nominal - A Response Rate with Rated  Load InertiaPPS RR JFA 185 Min - T Deg/sec RR JFA 277 Min T Resonant Frequency For  Dynamic Testing  (See Note  4)Hz Fn 90 Min - A Torque to Accelerate at  Rated PPS (See Note 2 /  Equation 8)N-m T /g302/g47 0.139 Reference Kc A Velocity at Rated Pulse Rate Deg/sec /g550 A 90 Nominal - D Pull-In Torque at Rated Pulse Rate (See Equation 10)N-m T PPS_A 1.30 Min - T Unpowered Back-driving  Torque (See Note 5)N-m T BD 0.09 /  0.18Min / Max - T Step Angle at Actuator  OutputDegrees /g507/g537 A 1.5 Nominal - I 384
Notes on Table 5:  1. The Composite Motor Friction Torque is the only parameter that is testable in the final motor  configuration. Bearing Friction Torque may be characterized with a preloaded set of bearings on a shaft with no magnets. Magnetic Coulomb Torque may be determined from subtracting the measured f BMform the measured f TM. 2. The Torque to accelerate the motor and load inertia at the required pulse rates was presented in  Equation 8, above. This is provided as a reference value.  3. To calculate the Rated minimum current per phase divide the maximum Resistance at 25º C  /g11/g52525_Max ) by the minimum Supply Voltage (V Min). It is recommended to test the Holding Torque  (TH25) at this value.   4. It is highly recommended that the Test Set Resonant Frequency be calculated to be greater than the operational Pulse Rate ( Rated PPS). See Equation 12. 5. Unpowered Back-driving Torque should be specified as a minimum when the actuator detent  torque is used to maintain position during launch. A maximum value should be specified in all cases, to identify a potential high-spot that may impede performance or create a latent issue.  6. Any test verification with (S) Similarity, should be characterized on a representative unit. Customer determination if Similarity verification must be conducted on Flight Production unit.  Properly Testing a Stepper Motor Actuator Since the performance of the actuator starts with the performance of the motor, testing the components of  the actuator at each modular level, as indicated in Table 5, is highly recommended. These tests are intuitive and self-explanatory and not discussed in detail here. However, dynamic testing of the actuator  assembly is vital. It is imperative to simulate the system load conditions as much as /g83/g85/g68/g70/g87/g76/g70/g68/g79 ly possible. It  is also desirable to measure performance at the integrated system but measuring performance at the  actuator level can avoid issues that may arise at a higher-level assembly. Some actuator suppliers  believe that as long as back emf is tested, the actuator has been characterized. This is an over-simplified  and potentially dangerous approach. Too many factors contribute to the dynamic performance of geared  stepper motor actuation and the “test-as-you-fly” mantra flows down to the actuator level. Figure 5 shows a typical geared actuator test set with simulated load inertia and performance torque  transducer. A vari ant of this test configuration is advant ageous. Rather th an utilizing a l oading magnetic  particle brake, replace that component with a geared velocity control motor to back-drive the actuator.  Employing torque transducers with integral position information is useful for position versus torque (or Torque-Theta) testing.  385
Figure 5. Example Stepper Motor Actuator Test Set-up As stated in Table 5 and following notes, determining the resonant frequency of the test set-up is  recommended. The Resonant Frequency (Fn), in Hz, of the test set-up is presented in Equation 12. /g1832/g1866 =  /g2869 /g2870/g3095/g3495/g3012/g3290(/g3011/g3261/g2878/g3011/g3262/g942/g3015/g3118) /g3011/g3261/g942/g3011/g3262/g942/g3015/g3118……………………………………………(12) Where K Ois the overall system stiffness, which may be calculated by the taking the inverse of the sum of  all the compliances in series: /g2869 /g3012/g3264= /g2869 /g3012/g3256+/g2869 /g3012/g3255/g3252/g3117+/g2869 /g3012/g3273+/g2869 /g3012/g3255/g3252/g3118+/g2869 /g3012/g3262/g3265/g3251   ……………..…………………(13) Where K Gis the gearbox torsional stiffness, and K FC1is the stiffness of Flexible Coupling 1, K xis the  stiffness of the Torque Transducer, K FC2is the stiffness of Flexible Coupling 2, and K MPBis the stiffness of  the Magnetic Particle Brake, all in N-m/rad. To achieve our desired load inertia of 5.4E-04 kg-m2it is  necessary to hard couple a flywheel on the rear end of the magnetic particle brake. By connecting the simulated load inertia here, the compliance of the magnetic particle brake must be added into the  equation. When stiffness components and inertia are factored into Equations 12 and 13, we obtain a  resonant frequency (Fn) of over 220 Hz, well above the desired goal of 90 Hz. Minimum. Therefore it is known that resonances in the test set will not affect the dynamic test results at rated operational velocity.  Once the Unit Under Test (UUT) is fixtured to the test set, static and dynamic runout measurements  should be made to assure alignments are proper. Also, there must not be any improper loading on the  UUT or the test fixturing. It is recommended that No Load and Inertia Factored Response Rates be  measured first. If there are any anomalous features of the UUT or the test set, these tests will highlight an issue quickly.   To check the Pull-In Torque, it is advised to set the magnetic particle brake to the minimum required  dynamic torque value, or T PPS_Min , and start the actuator from random rest position to verify the unit pullsin at the specified pulse rate at minimum voltage. This is a Pass / Fail method that does not verify the actual magnitude of the pull-in torque, but rather that the minimum required value is achieved. To test the  386
Appendix A Stepper Motor Performance Equations (Two Phase Motor) Parameter Symbol Units Equation Step Angle at Actuator  Output/g507/g537A Degrees /g959/g2016/g3002= /g959/g2016/g3014 /g1840 Velocity at Actuator  Output/g550A/g1830/g1857/g1859 /g1845/g1857/g1855/g2033/g3002 =/g543/g547 /g3014/g1499  /g1842/g1842/g1845 /g1840 Load Inertia Reflected to  MotorJLM kg-m2/g1836/g3013/g3014= /g1836/g3013 /g1840/g2870 Inertia Factor JF - /g1836/g3007=/g1836/g3013/g3014+/g1836 /g3014 /g1836/g3014 Total Power Input at  Holding (at +25º C) PH25 Watts /g1842/g3009/g2870/g2873 =/g3428/g1846/g3009/g2870/g2873 /g1837/g3014/g3432/g2870 Motor Constant (at +25º  C)KM/g1840/g1865 /g958/g1849/g1853/g1872/g1872/g1837/g3014= /g1846/g3009/g2870/g2873 /g958P/g3009/g2870/g2873 Motor Constant  (alternate equation)KM/g1840/g1865 /g958/g1849/g1853/g1872/g1872/g1837/g3014= /g1837/g3021 /g958/g563 /g2870/g2873 DC Resistance (at +25º  C) /g52525 Ohms /g2007 /g2870/g2873= 2/g1669  /g1848/g2870 /g1842/g3009/g2870/g2873 DC Resistance at other  Temperature (t 2)/g525t2 Ohms /g2007/g3047/g2870= /g2007 /g2870/g2873  [1 + .004 (/g1872/g2870/g33982 5 )] DC Current at Holding  /g1835/g2870/g2873Amps  Per  Phase/g1835/g2870/g2873= /g1848 /g563/g2870/g2873 DC Current at Holding at  other Temperature (t 2) /g1835/g3047/g2870Amps  Per  Phase/g1835/g3047/g2870= /g1848 /g563/g3047/g2870 Total Power Input at  Holding, at other Temperature (t 2)PHt2 Watts /g1842/g3009/g3047/g2870= 2/g1848/g2870 /g563/g3047/g2870 Torque Constant  KT/g1840/g1865 /g1827/g1865/g1868/g1837/g3021= /g1846/g3009/g2870/g2873 1.414 /g942 /g1835 /g2870/g2873 Torque Constant  (alternate equation)KT/g1840/g1865 /g1827/g1865/g1868/g1837/g3021= /g1837 /g3014/g942/g958/g56325 Holding Torque at +25º  CTH25 N-m /g1846/g3009/g2870/g2873 = /g3435 /g1840/g942/g2015/g1833/g3439/g942/g1837/g3014/g2870/g2873 /g942/g3493/g1842/g3009/g2870/g2873 Holding Torque at +25º  C (alternate equation)TH25 N-m /g1846/g3009/g2870/g2873 = /g3435 /g1840/g942/g2015/g1833/g3439/g942 /g1837/g3021/g942/g1835/g2870/g2873/g942 1.414 Holding Torque at other  Temperature (t 2)THt2 N-m /g1846/g3009/g3047/g2870= /g3435 /g1840/g942/g2015/g1833/g3439/g942 /g1837/g3021/g942/g1835/g3047/g2870/g942 1.414 Torque at Low Pulse  Rate at +25ºCTPPS-0 N-m /g1846/g3017/g3017/g3020_/g2868 =  (/g1846/g3009/g2870/g2873/g942 0.707 ) /g3398 /g1840 ( /g1858 /g3003/g3014+/g1858 /g3004/g3014+/g1858 /g3003/g3008) No Load Response Rate  at Actuator Output (at +25º C)RR/g1830/g1857/g1859 /g1845/g1857/g1855/g1844/g1844 =  /g1837/g3019/g3019 /g9426/g942  /g3493/g1842/g3009/g2870/g2873  /g1840  388
Appendix A Stepper Motor Performance Equations (Two Phase Motor) Parameter Symbol Units Equation Inertia Factored  Response Rate at Motor(at +25º C)RR JF/g1830/g1857/g1859 /g1845/g1857/g1855/g1844/g1844 /g3011/g3007= /g1837/g3019/g3019/g9426/g942  /g3493/g1842/g3009/g2870/g2873 /g1840/g1499  /g3493/g1836/g3007  Acceleration Torques,  Reflected to Load Note- /g507/g537 Amust be in  radians for this  equation/g1846/g3080/g3013 N-m /g1846/g3080/g3013= /g1836/g3014/g942/g1837 /g1855/g942/g1840/g2870/g942/g1986 /g2016 /g3002 /g1986/g1872/g2870+ /g1836/g3013/g942 /g1837 /g1855/g942/g1986 /g2016 /g3002 /g1986/g1872/g2870/g942/g2015/g3008 /g36/g89/g68/g76/g79/g68/g69/g79/g72 Pull In Torque  at Required Pulse Rate  at Actuator OutputTPPSA N-m /g1846/g3017/g3017/g3020 /g3250 = (/g1844/g1844 /g3011/g3007/g3398/g2033 /g3002) (/g1846 /g3017/g3017/g3020_/g2868 )  /g1844/g1844 /g3011/g3007 /g53/g72/g84/g88/g76/g85/g72/g71 Pull In Torque  at Required Pulse Rate  at Actuator Output(Interpreted from GSFCSTD-2000)/g1846 /g3017/g3017/g3020_/g3014/g3036/g3041 N-m /g1846/g3017/g3017/g3020_/g3014/g3036/g3041 =(/g1832/g3013 /g942/g1837/g3023)+( /g1832 /g3013(1/g3398/g2015 /g3008)(/g1837/g3023/g33981 ) )+/g1846 /g3080/g3013 +(/g1840 (/g1837 /g3023/g33981)(/g1832/g3003/g3014+/g1832 /g3003/g3008)) + (/g1840(/g1837 /g3004 /g33981 ) /g1832 /g3004/g3014) Margin of Safety (must  be >0 for adequate torque margin)MoS -  /g1839/g1867/g1845 =  /g1846/g3017/g3017/g3020_/g3002 /g1846/g3017/g3017/g3020_/g3014/g3036/g3041/g33981 Natural Circular  Resonant FrequencyFn Hertz /g1832/g1866 =  1 2/g2024/g3496/g1837/g3042(/g1836/g3013+/g1836 /g3014/g942/g1840/g2870) /g1836/g3013/g942/g1836/g3014/g942/g1840/g2870 389
Appendix A  Variable Definition Symbol Units Definition / Comment /g507/g537M Degrees/step Step Angle at Motor. Supplier provided value.  PPSSteps Per  SecondApplication Dynamic Pulse Rate (Pulses Per Second)  N - Gearbox Ratio. Supplier provided value. JL kg-m2 Load Inertia JM kg-m2 Motor Inertia. Supplier provided value. KRR/g1844/g1842/g1839 /g958/g1849/g1853/g1872/g1872Motor Response Rate Constant – Supplier provided value. Value will  change for drive method and whether unit is simplex or redundant.  /g536G % Gearbox Efficiency. Supplier provided value. fBM N-m Motor Bearing Rolling Friction. Supplier provided value. fCM N-m Motor Coulomb or Detent Torque. Supplier provided value. fBG N-m Gearbox fore-driving bearing friction. Supplier provided value. KC - Torque Margin Factor for Known (Stable) Source. Value changes at  maturity stage of the program. See Table 3.  KV - Torque Margin Factor for Variable (Potentially Changing) Source. Value  changes at maturity stage of the program. See Table 3. FL N-m Friction at the Load  KO N-m/Radian System Overall Torsional Stiffness.  V Volts, DC Supply Voltage (should be de-rated for electronics headroom)  /g507/g87 Seconds Seconds per step or 1/PPS 390
design, significance of secondary effects, material selection, and processing, to name a few, were  identified to aid in future design iterations. Figure 1. MPCV EFT-1 CM-SM Umbilical  in its Stowed Configuration    Hardware Description and Development The CM-SM umbilical spring strut consists of multiple piece parts assembled with sliding contact  interfaces. A detailed image of the assembly with piece parts identified can be found in Figure 2. The  titanium actuator spring is compressed when configured to the strut flight length (780 mm (30.7 in) between end fitting spherical bearings). The compression force is applied to the aft cap, located on the  SM side, and piston located internal to the actuator housing. The piston transfers the load to the secondary piston through a contact constraint normal to the strut axis. The contact surface between the piston and secondary piston is permitted to rotate relative to one another and is only opposed by friction.When the strut is permitted to actuate, after release of the umbilical interface at the CM, the compressed spring forces the piston forward sliding through the actuator housing and driving the secondary piston forward. Dual spring-loaded latches slide over the piston as it moves through the actuator housing. Once  the piston traveled past the latches, the latches are forced into the actuator housing cavity prohibiting the  piston from returning to its pre-actuation position. During the actuation, the driven secondary piston will  move until it contacts the aluminum honeycomb damper dissipating the energy of the forward stroke. Spring Struts  392
Figure 2. MPCV CM-SM Umbilical Spring Strut Detail Cross Section The forward lug interfaces with the umbilical side of the CM-SM umbilical mechanism while the aft cap  interfaces with the SM side. A spherical bearing in both end fittings is pinned in a clevis and permits some misalignment when installed in the flight vehicle or test fixtures. The umbilical side test interface consisted  of a test fixture and the SM side interface a flight-like actuator bracket. The forward lug and aft cap have  threaded aluminum 7050 interfaces to their adjoining parts, the secondary piston and actuator housing, respectively. The threads for these parts were cut and have an applied polyester locking patch and single  braided lockwire between the elements to serve as secondary locking features. As-designed, aluminum 7050 parts with sliding contact interfaces, the secondary piston, forward cap,  actuator housing, and piston, have a General Magnaplate proprietary Tufram L-4 surface treatment. This treatment is a polymer (i.e., polytetrafluoroethylene (PTFE)) impregnated Type III hard anodize to minimize stick/slip. During NESC fabrication, a Type III hard anodize was mistakenly applied instead of the as-designed surface treatment. The test hardware surface treatment was considered to provide a  conservative wear condition at the sliding surfaces and deemed acceptable by the joint NESC and LM  team for the development test program.  After compressing the strut to the stowed flight length, a retention tool (shown in Figure 3) was applied to  sustain the compressed state of the strut. The retention tool interfaces with two through tooling holes  located in the secondary piston and the body of the actuator housing. The tool was applied after initial  assembly, after pre- and post-random vibration performance testing, and during reconfiguration between random vibration test axes.  Figure 3. CM-SM Umbilical Spring Strut with Retention Tool 393
Development Testing Random vibration testing was performed after initial performance testing (described below) to assess the  umbilical spring struts capability to meet applicable functional requirements following exposure to qualification levels of random vibration environments. This process included acceptance testing intended  to screen production units for latent manufacturing, material, and workmanship defects.   Two random vibration environments in each axis were provided by LM for the umbilical and SM side  inputs. Several options were initially evaluated for the random vibration test configuration before reaching  an agreement to utilize two T-2000 Unholtz-Dickie 80068 N (18000 lb f) shakers with two shaker control  systems and two random vibration environments applied simultaneously and uncorrelated. By using two shakers, the umbilical strut was exposed to the required environments and was the closest to qualification of a “flight-like” configuration. The dual shaker configuration can be found in Figure 4.  Strain gages (four total) were initially installed only on the aft housing due to channel number limits. After  Z-axis testing, three strain gages were added to the secondary piston and used in place of three of the aft  housing gages. The control 3-axis accelerometers for test control, channels 1-12, were placed on the test fixtures (two on each end). Figure 4. Dual Shaker Configuration (Z-axis) The test proceeded with the Z-axis first followed by the X-axis and finally the Y-axis. Each testing axis  followed a similar pattern: minimum workmanship screening (MWS) and acceptance level loads were  applied for 60 seconds, followed by the qualification levels for 3 minutes, and finally another MWS for comparison to the first MWS to assess changes in stiffness. Figure 5 illustrates discrepancies in  responses that were seen upon comparison of the pre- and post-qualification level MWS runs in the Zaxis. The difference was found to be loosening of the aft cap during the qualification level testing. The aft  cap was re-torqued and additional lockwire at a larger gauge was applied for follow-on testing. Figure 5  shows the minimal difference in the X-axis pre- and post-qualification level MWS runs. Additionally, the  assessment team noted debris was observed exiting the spring strut when qualification levels were  394