ai-aerospace/ams_data_full_2000-2020 huggingface dataset:
Acknowledgements  Special thanks are extended to Erik Wilkinson, Charlie Hamp, Kiley Jones, Scott Miller, Richard Maxwell,  Randall Whitaker, and the whole Mechanism, Electronics and Reliability teams at BATC that supported  the testing, evaluation, review and solution process. Additional thanks and recognition go to CDA  InterCorp for their responsive service and capabilities.  References  1. Starin, Scott, and Crosno, Fred, “System Characterization and Motor Step Verification through Rotary  Acceleration Signals,” 36th Aerospace Mechanisms Symposium, May 2002.  2. Starin, Scott and Neumeister, Jeff, “Eddy Current Damper Simulation and Modeling”, Proc. 9th European Space Mechanism and Tribology Symposium, Liege 21 Sept. 2001, ESA SP-480,  September 2001.  3. CDA InterCorp, “Stepper Motor Engineering Reference Data”, © 2000  4. Ramakant Gayakwad and Leonard Sokoloff, “Analog and Digital Control Systems”, Prentice Hall,  Engelwood Cliffs, NJ  07632, © 1988.  5. Starin, Scott and Rodriguez, Tony, “Soft Stepping and Disturbance Compensation Through Rotary  Acceleration Signal Processing”, Proc. 10 th European Space Mechanism and Tribology Symposium,  San Sebastian, Spain, 24-26 September, 2003, ESA SP-524, September 2003.  44
Following the proposed plan, hardware for the magnetostrictive valve design (designed using ER funds  prior to this effort), shown in Figure 1, was built within the first year of the effort. However, the valve could  not be reasonably modified as an actuator, so a new design was developed. The newly designed  actuator, shown in Figure 2, used lessons learned and some concepts from the original valve design.   Figure 1. Original Valve Design  Early testing revealed that Terfenol –D does  not hold up well to high frequency responses.  The material is very brittle and susceptible to cracking and fracture if improperly side  loaded. Results of testing are shown in Figure  3. Also, the small motions in the actuator require machining to close tolerances, precise  shimming to achieve correct preloads to obtain  proper strain (elongation), and large magnetic  biasing to maintain the proper pre-load on the  material to prevent hysteresis. Figure 4 shows  that the Terfenol D material hysteresis decreases and strain increases with preload.  The design allowed for these adjustments in  the preload using shims under the pre-load  springs.   Figure 1. New Valve /Actuator Design  Figure 2. Terfenol-D Is Very Brittle. The material was loaned to a local contractor to  perform tests to verify the respon se of the material  to preload. The contractor presented data, shown in Figure 5 that differed from the theoretical data  supplied by the material vendo r, shown in Figure  4. This data was incorporated into the new design. The contractor derived curve, Figure 5, shows the  hysteresis in the material measured as a load is  applied to the end of a bar of Terfenol D. This is a plot of magnetic field line angles from the normal  (axial) direction. The angle is directly related to the  inverse relationship of magnetic input for a force output. 46
After incorporating preliminary test results into the design, the fabricated hardware was assembled, as  shown in Figure 6, and tested. During testing, several issues were discovered. The stroke of the valve  was measured as 0.14 mm on the arm (multiplied) versus the expected stroke of 0.38 mm. Figure 7  shows the displacement measurement recorded during test. Investigation revealed that the magnetic field suggested by the vendor for magnetic biasing of the material was too high and caused the crystalline  structure to begin to exhibit strain (elongation) before the electric field was applied. The magnets were  eliminated and the valve coil repositioned resulting in a stroke of 0.22 mm, just over half the predicted stroke. Perhaps, using we aker magnets for the biasing would increase the stroke of the material, but time  did not allow for this to be done.  Figure 4. Material Hysteresis vs. Preload  Figure 5. Measured Hysteresis  47
Figure 6. Final Valve Assembly  Figure 7. Original Displacement  Per design, the length of the coil was approximately half the length of the magnetostrictive material. The  concept was to use the end effects of the shorter coil to provide strain to the material out side the coil, so  the coil was centered on the material. This concept was not ideal and a new coil was ordered, but time  did not allow testing with the new coil. During a review of the magnetic flux path design with a local vendor, it was suggested that the design may not accommodate an ideal path and the valve was “leaking”  magnetic field strength. A possible solution to this issue is to replace the aluminum-bronze shield  surrounding the coils with a new shield made of a magnetic material. These three changes, weaker  magnets, a longer coil and a different shield material, could be easily incorporated into the design if time  and budget allowed.   Planned Future Work:   No current program has expressed interest in the technology. CLV is working to a  low risk, existing technology approach. Future programs, such as LSAM, have inquired, but no technical risks have been identified where this technology would be useful. A Space Act Agreement with Orion will  continue and ER33 plans to apply for some Inno vative Partnerships Program funds to expand this  development.  48
Publications and Patent Applications:   ER33 has submitted a patent application for the magnetostrictive  valve. The local company that performed the load testing on the materials has entered into a Space Act  Agreement with MSFC to develop this into a marketable reg ulator for space craft application. Being  proportional, fast, and small, this valve has the potential to be an electrical regulator and could provide a regulator system that has little or no change in regulation regardless of the required flow demand. This  would improve pressure feed reaction control system performance, better control purges, allow active  pressure control in propellant tanks, and a number of other advantages.  Conclusions  The data obtained during this effort ha s proven that the concept actuator design has merit, shown the  valve design must be carefully controlled, and that the preload, coil design and flux path issues are critical  to obtain the required stroke and repeatability. The valve met all design requirements except stroke. This  problem has been evaluated and solutions developed, but not proven. The design could be modified to  incorporate these improvements and regain the lost stroke.   Therefore, the concept has been shown to work, th e multiplying lever system worked perfectly and the  valve concept shows potential.  Additionally, newer materials are available that have larger strokes (Terfenol-D has 1200 PPM, newer  materials have 5000 PPM potential). The design provided has proven that the use of magnetostrictive materials in valves is a viable concept. More time and better magnetic flux path design is needed to fully  utilize the capabilities of this material.  49
Design and Development of a Miniaturized Double Latching Solenoid Valve for  the Sample Analysis at Mars Instrument Suite  James T. Smith* Abstract  The development of the in-house Miniaturized Double Latching Solenoid Valve, or Microvalve, for the Gas  Processing System (GPS) of the Sample Analysis at Mars (SAM) instrument suite is described. The  Microvalve is a double latching solenoid valve that actuates a pintle shaft axially to hermetically seal an  orifice. The key requirements and the design innovations implemented to meet them are described.  Introduction  This paper outlines requirements, design and development activities of the SAM Microvalves. The SAM  instrument suite will be an integral part of the Mars Science Laboratory rover, and the Microvalves will control the gas flow within the SAM instrument suite.  There are 44 in-house Microvalves in SAM, as well as several Microvalves supplied by the sole outside  provider of this technology. The decision to develop and build in-house Microvalves was primarily based  on past delivery performance of the outside vendor coupled with the high number of valves needed for  this mission. Additionally, improvements in mass and reliability were goals of this design effort.  Background  NASA’s Goddard Space Flight Center has used Microvalves on several missions in the past (e.g. Galileo,  Cassini/Huygens), but never in the quantity required for SAM. Over the past several decades, only one  vendor has been able to meet the difficult requirements for the Microvalve, but this vendor has had difficulties meeting delivery schedules. Due to the large number of valves required for SAM, the decision  was made to develop an in-house design.  The effort began as an Internal Research and Development project in 2004, and is currently in the flight  qualification phase.  Driving Requirements  The primary requirement for the Microvalve is the leak rate. The valve is required to have a helium leak  rate across the valve seat and through the outer case of less than 1x10 -10 atm.cc/sec. This drove the  design of the pintletip as well as the use of bellows to isolate the gas flow. Also, the materials for the  components in the gas flow must be chemically inert so they do not influence the scientific  measurements.  Another key requirement was that the valves must be able to survive the qualification temperature range  of -60°C to +225°C, and be capable of operation from -40°C to +195°C. This requirement further limited  material selection.  In order to reduce mass over current technology, the valves were designed to be welded into their  respective manifolds as opposed to a bolted configuration. This requirement drove the design of the  “floating” pintletip, as well as the use of an explosion welded Inconel to Titanium bellows housings.  * NASA/Goddard Space Flight Center, Greenbelt, MD  Proceedings of the 39th Aerospace Mechanisms Symposium, NASA Marshall Space Flight  Center, May 7-9, 2008 51
Since there are a several Microvalves su pplied by an outside vendor us ed on SAM, there was a  requirement that the in-house Microvalve operate of the same drive circuitry. This requirement drove the  design of the solenoid, as well as the position sensor.  Microvalve Design Overview  A Microvalve is a double latching solenoid valve that actuates a pintle axially to hermetically seal an  orifice to control gas flow. A permanent magnet latches the valve in either the open position or closed  position with the power off, and a solenoid is energize to change the state of the valve.  In order to achieve the required lea k rate, a diamond turned Vespel pintletip is  pressed into a lapped and  polished titanium valveseat when the valve is closed. The load is applied to the pintletip via a pintle shaft.  The load on the pintle shaft is generated by a stack of disc springs that are compressed by an armature.  The armature compresses the disc springs when it is magnetically latched in the closed position by a  permanent magnet. The amount the disc springs are compressed is controlled by adjusting the gap under the armature that is present at the moment the pintletip first contacts the valveseat. This gap will be  closed by the magnetic force of the permanent magnet. The adjustability is discussed in a later section.  A bellows is used to isolate the sample gases and obtain the outer case of leak rate of less than   1x10 -10 atm.cc/sec. The bellows are made of SS321 and are electron beam welded at each end to  Inconel 718. The bellows were designed to have a low spring rate because the force generated by the  bellows when the valve is in the open state acts against the magnetic latching force that holds the valve  open. To control the magnetic flux path (see Figure 4), alternating rings of Inconel and Hiperco are brazed  together and then machined on a lathe to allow for a sliding fit with the armature. The brazing compound  used was selected to be below the annealing temperature of Hiperco so the brazing process would not  degrade the performance of the assembly.  To reduce friction, both the brazed assembly a nd the armature are co ated with Dicronite, a modified  tungsten disulfide dry lubricant. Additionally, the armature and the pintle shaft are nickel coated to prevent  similar metals from having a slidin g contact surface.  Specifics of the pintletip design, the solenoid design, and the adjustability feature are discussed in more  detail in later sections.  Valve Specifications Mass: 20 grams  Height: 35.5 mm (26.5 mm above manifold surface)  Diameter: 14.73 mm  Power: 18 volts (Since the valve operates on a pulse from a capacitor, voltage is the constraint) Helium Leak Rate (valveseat): < 1x10 -10 atm.cc/sec (instantaneous), 2x10-9 atm.cc/sec (steady state)  Helium Leak Rate (case): < 1x10-11 atm.cc/sec  Operational Temperature Range: -6 0°C to +220°C  All materials in gas flow are chemically inert  Valve Orifice (diameter): 1.778 mm  Pintle Travel: 0.762 mm Actuation Time: < 1 millisecond  52
Figure 1 - Microvalve Cross Section  Pin receptacle Electrical Cap  Armature Magnet Coils  Explosion welded   inconel-titanium   joint Feed-thru pin  Solenoid Housing Tophat Position indicator  Weld clips  Disc spring stack Armature Housing  Assembly (brazed)  Bellows  Pintle Floating pintletip  Floating Pintletip  The pintletip for the Microvalve is made from Vespel 22 due to the inert nature of the material, as well as  the high operational temperature of Vespel. The part is fabricated on a lathe to the rough dimensions, and then finished on a diamond turning machine to impart a curved surfaced upon the 60-degree cone as  shown in Figure 2 (the outside line represents the rough cut part, with the inside line representing the  finished, diamond turned part). By creating a curved surface, the pintle tip will “self seat” when pressed  into the cone shaped valveseat like a ball in a cone.  Through experimentation it was determined that a radius of curvature of  0.381 cm (0.15 in) was ideal.  After the pintletip is diamond turned, it is hand polished with an extremely fine polishing cloth. Each  pintletip is screened to ensure the required leak rate can be achieved. It should be noted that the leak  rate of less than 1x10 -10 atm.cc/sec is the instantaneous leak rate, and that the Vespel will permeate  helium at a leak rate of about 2x10-9 atm.cc/sec when subjected to helium for an extended period of time  (between 5 to 30 minutes).  53
In order to facilitate the “self seating” action, the pintletip is free to rotate about all three axis, and free to  translate in two directions, with the only constraint being the movement along the axis of travel (the Z-axis  as shown in Figure 3). The pintletip “floats” in the pintle collar, which is welded to the pintle shaft. The  backer plate applies the load from the pintle shaft when the valve is closed, and the plate itself has a curved surface to allow for rotation as the pintle seats itself into the valveseat. The “floating” feature also  allows for some misalignment between the axis of the pintle shaft and the axis of the conical valveseat.  This is critical since the valveseat is part of the manifold, and the valve is welded into the manifold, which limits alignment capabilities.   Figure 2 - Pintletip Profile  Titanium Valveseat SS304 Backer plate  Vespel pintletip  YZInconel pintle shaft  Inconel pintle collar  Figure 3 - Floating Pintletip Cross Section  54
Figure 4 - Sample Pintle Tips  Solenoid Design  The solenoid consists of two coils wound with H-APTZ magnet wire, a radially magnetized Samarium  Cobalt magnet, and a Hiperco 50A housing (see Figure  5). The flux path shown in Figure 4 is for the  valve in the closed position. The magnet allows for the valve to remain either open or closed with no  power supplied to the solenoid. The solenoid is energized by the discharge of a capacitor, and the valve  changes state in less than 1 millisecond.  One of the key features of the in-house design is that the solenoid is removable. The ability to replace a  solenoid without replacing the whole valve allows for increased reliability in the welded design. If a  solenoid were to fail during acceptance testing or any pre-launch operations, the faulty solenoid could be easily swapped out for a new one without machining the valve out of the manifold.  To increase the durability of the coils in the solenoid they are encapsulated with Duralco 4460.   The bobbins that the coils are wound around are ultrasonically machined out of Magnesia partially  stabilized Zirconia. This process allows for tolerance control within 0.0254 mm (.001 in) since the ceramic material is machined in the hardened, not green state. The material is very strong, has an extremely high  dielectric strength, and has a compatible CTE for the required temperature range.  The wires for each coil are terminated at copper pins by laser welding. The pins are supplied bonded into  glass barrels with Kovar sleeves, and these assemblies are bonded into the towers on the ceramic top  bobbin.  Another feature of the solenoid design is that the coils can be run either in parallel for redundancy, or in  series to reduce the require size of the capacitor to change the valve state. The only change necessary to  switch the mode of operation is a change in the wiring of the electrical cap that interfaces with the wiring  harness to the drive circuitry. For SAM, the coils are run in series.  55
Sm-Co Magnet  Figure 5 - Solenoid Cross Section  Adjustability for Tolerance Stack-up   Since the components of the Microvalve are small, the tolerances of standard machining become more  obvious as a percentage of overall dimensions. For example, on the pintle backer plate shown in Figure 3, the shaft that aligns the part to the pintle tip is on ly 0.4064 mm (0.016 in) in  diameter. The standard  tolerance of ±0.127 mm (0.005 in) would be over 50% of the overall dimension! While tolerances in the  range of 0.00254 mm to 0.0127 mm (0.0001 in to 0.0005 in) are achievable, they come at a cost. In order to achieve meet the design intent and keep cost relatively low, most tolerances were set to 0.0254 mm to  0.0508 mm (0.001 in to 0.002 in).  The downside is that those tolerances still result in variation from valve to valve during assembly. For the  disc springs to apply the correct load to the pintle sh aft when the valve is closed the amount the disc  springs are compressed must be controlled to within 0.0254 mm (0.001 in). Therefore there has to be  adjustability to control the amount of compression. Figure 5 sho ws how adjustment shims are used to  increase or decrease the gap. Each stack of disc springs is calibrated so that the amount of compression required for a desired force is known within 0.0127 mm (0.0005 in).  The measurements shown below are taken during assembly, and the adjustments are made for each  valve. After the adjustments are made, weld clips (not shown in Figure 6) are tack welded into place, and  the valve is actuated and leak checked to verify the performance. Once verify, the weld clips are  permanently welded into place and the tophat is welded onto the valve.  Position Sensor  The Microvalve is designed to have a resistance based position sensor (shown in Figure 1). A flexure  contacts a pin when the valve is in the open state and creates a path to ground though the valve case.  This design was selected because of the requirement that the valve use the same electronics as current technology. That meant that there was only one wire to use, and that position sensing circuit was based  on a resistance measurement. NSHiperco 50 Inconel 718 Coils  Flux path For illustrative  purposes, not current design  56
Adjustment shims Figure 6 - Disc Spring Compression Adjustability  However, a recent failure with several of the flexures themselves has caused this feature to be removed  from the current design used on SAM. The project was not depending on position knowledge for any of  the command sequences, and would only use the knowledge for diagnostics. Therefore, due to the  extremely tight schedule for SAM, the decision to remove the flexure was reached easily.  It is known that the flexures yielded during actuation, but the exact cause is not yet known. The flexures  are designed to see 0.0762 mm (0.003 in) of deflection when the valve is open. Life tests were performed on the flexures where they were deflected 0.127 mm (.005 in) for 10,000 cycles followed by an additional  1,250 cycles at 0.1778 mm (0.007 in) of deflection with no yielding or decrease in reactionary load   (~.22 N @ .1778 mm deflection).  One possible cause could be an overshoot of the pintle shaft during the opening of the valve where the  flexure would see excessive deflection before settling to the static position. However, preliminary testing  indicated there is less than 0.0254 mm (0.001 in) of overshoot, which would not explain the yielding.  Another issue to be investigated is that the valve actuates in less than 1 millisecond, and the shock event  may be affecting the flexure. The rate of deflection during the life test performed was so slow it could be  considered quasi-static.  Due to the schedule for SAM, this means that there will be no position indicator. However, alternate  methods for determining position with just one wire are currently being investigated for future use. One method would be to measure the change in inductance of the top coil that would result from the  movement of the armature. Another method would look at the back EMF present when the valve is  commanded to close and see if it differs depending on the current state of the valve. For example, is the back EMF higher when you command a valve closed that is already closed than it is if was open?  Testing The first batch of four (4) Qualification Valves has successfully completed both the vibration and thermal  vacuum portion of the qualification test program. • hgap controls the  amount the disc springs compress  • By measuring h arm, dcavity, and d arm you  can determine h gap • hgap can be controlled  by moving the shims (SS304) from on top  to below the armature  and vice versa darm dcavit yharm hgap For illustrative  purposes, not current design  57