ai-aerospace/ams_data_full_2000-2020 huggingface dataset:
ratio and a fixed mass for the flywheels. While this design is simple, it only allows for the inertia to be  tuned to one combination of exercise subject mass, exercise subject deceleration, and free weight mass.  The ARED flywheels do not account for the changes in the exerciser subject’s mass. They do, however,  adjust to the exercise subject’s deceleration and free weight load. The flywheels add more load into the  system at higher load settings, because the piston moves further per stroke, in the same amount of time.  Also, a faster deceleration of the exercise subject causes the flywheel to decelerate faster as well. This  increases the inertial load felt at the lift bar. In the beginning of the project, the flywheels were tuned to a  227-kgf (500-lbf) squat setting on ARED with a 2 second period and 76.2-cm (30-in) stroke. After ARED is  on-orbit for a significant amount of time, the flywheels could be tuned to a more optimal load setting and  stroke. This would need to be determined from statistical analysis of the exercise frequency, load, and  stroke data from on-orbit use. A chart showing the calculated variation from the true 1 -G inertia is below  (Figure 13).  The assembly contains one spur gear and two helical gears. The spur gear has a 38-mm (1.5-in) pitch  diameter, the large helical gear has a 127-mm (5.0-in) pitch diameter, and the small helical gear has a 38-  mm (1 5in) pitch diameter. The spur gear is made out of 17-4 PH SS and the teeth are also ion nitrided  to provide a longer life of the gear teeth and to prevent pitting. The helical gears experience lower loads  and are not ion nitrided. The initial prototype of the flywheel assembly used two lubrication methods to  determine which would perform better. One gear set employed standard lubrication (Rheolube 2000)  while the other had a ceramic dry-film lubrication called Vitro-lube. Our initial life-cycle test showed that  standard lubrication was more reliable. Early in our life-cycle test, the Vitro-lube began to flake off  significantly. As a result, the team opted to go with standard lubrication.  Spur Gear-  Figure 12. Flywheel assembly with front cover removed and close up of gears and flywheels.  The spur gear is not visible. A cross-section view through the spur gear teeth is also shown for clarity.  325
The track is curved to minimize force non-linearity as a function of load adjustment. The slider moves up  and down inside the housing, which is attached to the ball screw, as the slider follows the tracks (Figure  17).  The life cycle design requirement for ARED is 15 years. A preliminary test was run on an engineering unit  of the arm base and cylinders at various load settings. During this test, at a 181-kgf (400-lbf) load setting,  the slider housing broke into 2 pieces (Figure 15) at 31 8,000 total cycles. After close evaluation, it was  determined that the stress analysis overlooked a critical load case. There was more moment on the  housing than first calculated and a fatigue analysis had not been done. As a result of the improved  analysis, the slider housing was thickened and strengthened with closeout plates. The original housing  was made of 7075 AI with a Tufram surface coating to increase surface hardness, extend wear, and  reduce friction. During the test, the slider did not slide very well along the Tufram surface. As a result,  rollers were also added to the slider design to reduce friction and to implement a zero clearance fit  between the slider and housing. With the new rollers added to the slider, steel wear plates had to be  added to the inside of the slider housing (Figure 16), to increase the life of the assembly.  I'  I i  II i  Figure 14. Old SliderRlousing Design for Arm Base  Figure 15. Old Slider/Housing design during life cycle test showing broken Housing  327
Slider w/ Rollers  '1  Figure 16. New Slider/Housing Design showir,, Glider w/ rollers and Hnfilcirlg wear plates  a  L 4f ., I  \  ~  . Curved Track -a .. - h  . Closeout Plates  Figure 17. New Slider/Housing design attached to ball screw showing closeout plates  The team also performed an engineering life cycle test on the arm base/load adjustment components.  This test rotated the ball screw and drove the rod ends back and forth along the length of the arm base.  The purpose of this test was to prove the critical components in the arm base assembly. This test was a  success and cycled the ball screw for 33,000 m (1.3 million in) of travel, before failure. Assuming a six  person ISS crew and various uncertainty factors, this would be enough ballscrew life to last for -1 4 years  328
Conclusion  The most important lesson that the team has learned in the course of the ARED project is that prototyping  and development testing is paramount and indispensable for developing a robust, reliable, complex  mechanical system. Good initial designs are important as well, but nothing can replace developmental  testing as a means to flush out design, manufacturing, assembly, and human-machine issues. Although  not popular, a prototype-centric development phase, in advance of flight production, will result in fewer  design problems, fewer modifications, fewer design iterations and, in the long run, decreases cost and  schedule. As a result of AREDs extensive prototyping and testing, both in the developmental phase and  the certification phase, the team is extremely confident that ARED will perform well on the International  Space Station and provide years of effective resistive exercise for the crew. Furthermore, as NASA  prepares to implement the President’s Exploration Initiatives, ARED’s technology will be mature and  proven in time to support long-duration expedition to the Moon and Mars.  330
Radarsat Range Adjustment Mechanism Design  Xilin Zhang* and Sylvain Riendeau*  Abstract  RADARSAT (Figure 1) is a series of sophisticated earth observation satellites developed by Canada to  monitor environmental changes and the planet’s natural resources. RADARSAT also provides useful  information to both commercial and scientific users in the fields of agriculture, cartography, hydrology,  forestry, oceanography, ice studies, and coastal monitoring.  At the heart of each RADARSAT satellite, there is an advanced Synthetic Aperture Radar (SAR) payload.  The SAR antenna is a 15-meter-long microwave instrument that sends pulsed signals to Earth and  processes the received reflected pulses. Its on-ground test fixture has high-resolution alignment  requirements. It is a challenge to any mechanical designer. The Radarsat-1 test fixture included an 18-  meter-long near field range scanner, an offloaded 6 degrees-of-freedom fine adjustment system to handle  and maneuver the 15-meter-long SAR antenna, an automatic closed-loop motor-driven adjustment  system, and a 15-meter-long coarse adjustment table. A large R & D effort was required throughout the  design, fabrication and final calibration of the equipment to ensure final success. Lessons learned from  the RADARSAT-1 range alignment fixture paved the road for the RADARSAT-2 system. This type of 6  degrees-of-freedom adjustment mechanism could be very useful to all kinds of large space structures for  on-ground alignment and test like solar arrays, antenna panels, etc. This paper covers the 6 degrees-of-  freedom mechanism design, development, fabrication and off loading calibration method. The lessons  learned during design, fabrication as well as integration and calibration are extremely useful to avoid future  problems for all mechanism designers.  _” 1  Figure 1. RADARSAT-2  Radarsat Mission Introduction boiar  Array  =-  * MDA Space, Inc., Ste-Anne-De-Bellevue, Canada  Proceedings of the 3dh Aerospace Mechanisms Symposium, Langley Research Center, May 17- 19,2006  331
Figure 2. Radarsat 2 Capabilities  1. The front radiating surface flatness of SAR 15-meter-long 1.5-meter-wide panel shall be within  0.7 mm (0.028 in) to meet the fine resolution RF requirement.  2. The front surface flatness of SAR shall be adjustable in 6 degrees-of-freedom. lt12.7 mm (0.5 in)  translation in all X, Y, Z directions. 0.35" of rotation around X, Y, Z axes to optimize the RF  performance.  3. After RF optimization, the SAR panel's positions are defined. The positions shall be able to be  locked in position to allow ESS installation.  4. A heavy-duty working platform is required to locate SAR at the center of the scanner plan to allow  a 1.5-meter over-scan all around the SAR.  5. SAR shall be able to move 700 mm in and out from the range scanner probe to enable the RF  engineer to optimize the test distance.  6. Range Adjustment Mechanism shall allow full access for ESS, Spacecraft Y panel assembly and  dummy sidewall installation after RF performance to be optimized.  7. Range platform shall be able to allow a minimum of 10 operators to be on the platform and to  work at the same time.  The range test setup design (Figure 3) includes the following major MGSE assemblies to meet the above  requirements:  1. 18 m x 6 m near field scanner to perform all required RF tests.  2. A range platform with 700-mm travel in and out from the scanner probe. It enables RF test  engineers to optimize the SAR panels to probe distance.  3. Four support trusses and a steel structure foundation are made to support the SAR panels' test  setup at the center of the scanner.  4. Dummy spacecraft sidewalls for ESS integration as well as a Y panel support to bring all  necessary payload electronics up for the range test.  333
5. A 6 degrees-of-freedom adjustment mechanism to allow SAR panels to be located according to  their designed positions on range and to optimize the RF performance.  I  -1 INNER>  SAR PANEL  RANGE PLAT F OHM RANGE AOJ!ISTMENT  SPACECRAFT Y- PANEL  DUMMY SIDE WALL 1  r-  Figure 3. Complete SAR Panel’s Range Test Setup  This paper will concentrate on the 6 degrees-of-freedom mechanism design, development, fabrication and  offloading calibration method.  During the design, the fabrication, the final integration and the calibration phase, many problems occurred.  The lessons learned are extremely useful to any mechanism and MGSE designer to avoid future  problems.  SAR Range Adjustment Mechanism Design  The SAR antenna is made of four SAR panels (+X inner and outer panels and -X inner and outer panels).  Four separate panels are required to stow the antenna in the launch configuration. The extendible support  structure will deploy the SAR Panels and hold them in position in orbit. During the range test, the antenna  was held in position in the deployed configuration by four sets of identical/mirror-imaged mechanisms.  Those mechanisms are used to adjust each panel in the required position and then hold them in place.  The mechanism working principles were sketched out during the preliminary design phase. Eight different  design proposals were studied, each one coming from a different design approach. A trade off analysis  was performed and the Preliminary Design Review approved the principle shown in Figure 4 and detailed  334
below. Each set of the adjustment mechanisms has an X-direction mechanism, a Y-direction mechanism  and a 2-direction mechanism. The Z mechanisms are installed directly on the range platform. The X  mechanisms are seated on two Thomson linear slides. A Thomson linear shaft connects each X  mechanism to a 2 mechanism through two ball joints. The Y mechanism consists of two Thomson linear  bearings. The Y-direction linear shaft is press fitted into the X-mechanism beam. The linear  motorshicrometers are installed on the mechanisms in every direction.  & LINEAR BEARING  LEGEND OF FIGURE  Figure 4 SAR Range Adjustment Mechanism Design Principle  The panel linear translations in X, Y, 2 directions are very simple. The two linear motorshnicrometers in  the same axis need to be driven in a synchronized fashion. The rotations are achieved by driving the two  motors/microrneters on the same axis for a different distance or direction. For a simple example, when the  linear motors/micrometers M2 and M3 are driven in a different direction, the panel will rotate around the 2  axis. If both a translation in the Y direction and a rotation around the Z axis are required, the linear  actuators M2 and M3 can be driven in the same direction but for a different distance. The panel will move  up or down and rotate around the 2 axis.  During all the adjustment operations, the SAR panel is connected to the adjustment mechanism by three  corners; the fourth corner (upper left in Figure 4) will be a safety-locking device. During the adjustment  process, it has to be completely loose to give the panel the 6 degrees-of- freedom. Once the panel is in  the required position, the fourth corner is locked in place with the safety-locking device.  Once the design principles are clear, many fine details have to be carefully looked at. For example, the  safety issues for the operators working around the Range Fixture, the flight hardware protection, etc. The  335
MGSE requirements 3 through 7 mentioned earlier are addressed by other generic mechanisms. Their  interaction with the 6 degrees-of-freedom adjustment mechanism needs to be carefully looked at during  the detailed design phase. The final design of the 6 degrees-of-freedom adjustment mechanism is shown  in Figure 5.  Single SAR  L palell  \ -' '  Figure 5. Single SAR Panel Range Adjustment Mechanism  Figure 5, extracted from the CAD model, only shows the +X outer panel range adjustment mechanism.  The -X inner panel mechanism is a duplicate of this design and the other two sets of mechanisms (-X  outer panel and +X inner panel) are mirror images.  SAR Range Adjustment Mechanism Motor-Driven Software  For Radarsat-1 , the linear motors, with 8.2-kg (18-lb) maximum capacity and their control system are  selected early in the program. Each SAR antenna panel adjustment mechanism is driven by 6 linear  motors M1 - M6. The motor execution program controls the mechanism motors and give the 6-degrees-  of-freedom adjustment to the antenna panels.  336
-t  Motor Displacement Calculation  CAD Graphic Exec File  Motor Format Conversion  CAD Graphic Display  Adjustment Exec File  Encoder Linear Actuator  Figure 6. Panel Adjustment Software Block Diagram  This system is used to align the panel in the plan parallel to the scanner plan or to adjust the panels to any  pre-defined test position. Also, the discrete manual input to the motion control program can drive the panel  during RF testing to the optimum RF locations for each panel. This special software was developed for  this specific application. The panel adjustment software block diagram is shown in Figure 6 [l] and is  followed by a detailed description of the main modules.  Data input: Panel surface points, panel four corners points and pre-defined set up position.  Optimization: Determine the best-fit antenna plane.  Adjustment sequence and actuator displacement calculation: Calculate each of the required motor  displacements from the adjustment sequence.  CAD output: Display the adjustment sequence on CAD screen.  Linear motors format conversion: Convert the required distance travel to the appropriate linear  actuators format in number of encoder counts. Assign the appropriate speed to the synchronized motion.  Motor/micrometer movement to achieve translation in X, Y, Z axes direction and rotation around XI Y, Z  axes are listed in Table 1. For Radarsat-1, once the SAR panel is installed on the range, the first set of  panel position data was taken and the data inputted in-to the program. The software calculates the  movement distance of each motor required to drive the panel in the designed position.  337
Table 1. Six Degrees-Of-Freedom Linear MotorNicrometer Adjustment  , Micromew-  rranslation X I  l rranslation Y  lrranslation Z  Rotation ex  Rotation By + or - 1 F or -  + or -  + or - Mt5  *l. Small adjustment might be required, but it is not the same distance as the others.  System Calibration and Verification  Most large MGSE designers typically specify a pre-calibration activity to verify the system design and  manufacturing before using it with flight hardware. Nobody wants to see expensive flight hardware  hanging in the air waiting to be installed on a MGSE that doesn’t work. To avoid surprises during the flight  hardware final installation phase, a mass dummy with flight mass, CG and flight representative interfaces  is designed and fabricated specifically for the calibration and verification.  The Radarsat-1 range fixture calibration went through many troubleshooting exercises; some of the  problems will be discussed in the lessons-learned section. All encountered problems were resolved during  the Radarsat-1 calibration and made the final integration a clean and problem free operation. These  experiences paved the road for the Radarsat-2 range fixture design and calibration.  For Radarsat-2, a new mass dummy was designed. It can be calibrated to represent all four Radarsat 2  panels. Weight location and calibration hoisting points are designed to be adjustable to meet all 4 different  panels’ CG and mass. All linear motor/micrometer loadings are finally balanced to less than 5.5 kg (1 2 Ib).  The Radarsat-2 mass dummy calibration is shown in Figure 7.  During the calibration, each panel location was positioned relative to the others using the NFR 3-axes  scanner in order to meet the design requirements. To calibrate the position of each panel, an X, Y, Z  mechanical block was installed at the center of the platform as the original point. The travel of the scanner  is used with a dial gage, which is installed on the near field scanner probe to precisely measure the  position of each measurement point. The final calibration got the dummy panels within 0.38 mm (0.01 5 in)  of their as-designed position. This simplifies the final SAR panel range set up installation and alignment  processes.  338
1  Figure 7. Using Mass Dummy to Pre-Calibrate the Design Setup  SAR Panel Final Range Alignment Result [2]  The four flight SAR panels were installed on the near field range adjustment mechanism. They were  positioned relative to each other and relative to the scanning plane using the NFR 3-axes. In order to  facilitate the positioning of the 4 SAR panels in a later stage of integration, 16 alignment-aid interface  points per SAR panel were machined on their back face. Laser tracker measurement equipment was used  to determine the position of these points relative to a reference coordinate system.  339
*  Large Scale Measurement Device >  */ Pane's  Base  # ,/- Frame  d . Base  (41 Frame  Laser Tracker  + Laser Tracker Targets  Figure 8. SAR Panel Location Measurement Setup  The line of sight to these points in the test range is limited due to mechanisms and guardrails in the back  of the panels. Different set-ups were required. Figure 8 shows a typical set-up schematic.  The measured point positions were finally given in the mechanical build (mb) coordinate system that was  predefined. Repeatability of the measurement was verified and the error from nominal position was  calculated. The final Laser tracker measurement results of the three-dimensional positional errors are  listed in Table 2. The error is defined as the difference between nominal and measured positions. The  maximum error calculated is 0.61 mm (0.024 inch) in the X direction. The compound error is attributed to  the tolerance of machining and assembly, the relative position of each panel to the reference frame and  the measurement set-up accuracy.  340
Table 2. Panel Measurement Point Location Error (in thousandths)  12 -2 -10  13 4 -9  18 8 -8  44-8 -Xim  &*a  18 5 -2  10 4 8  15 3 2  18 -9 3  22 2 17  18 -5 13  22 9 16  12 3 5  10 -1 -1  17 -5 0  213 2 3  27 -3 8  29 -14 -13  22 4 -17 +Xim  -2 0 4  -2 3 4  4 4 -1  -5 12 3  -9 2 3  8 8 -1  -15 2 0  -1 1 3 -6  -13 -2 -7  -15 a0 4  -a 10 -7  -22 4 -9  -21 10 -8 -1 -16 a -24 5 -9  -17 -15  -24 -7  -17 -10  -12 -8  -23 -19  -21 -5  -17 -11  -14 -10  -10 6 3  4  -3  4  18  -1  8  0  6  -19 -12 -19  -19 -17 -14  -18 -17 -7  Lessons Learned  Lessons Learned 1  Linear motors with a computer software auto-adjustment system offer a nice system to have if there are  several hundred panels to be adjusted, aligned and tested. They can significantly reduce the labor costs  (on mass production). For single SAR requirements, it is not cost effective. For Radarsat-1, the problems  with the motors, driving system and software, as well as all related troubleshooting. It became the major  cost for the overall Range Fixture.  For RADARSAT-2, MDA decided to replace the system with a set of 6 (total 24) high-resolution manual  micrometers, a dial gage O,O,O reading system and somebody on the floor with a good calculator. Good  results were achieved at a fraction of the price.  Lessons Learned 2  Offloading point selection is critical to get ideal 0 g and linear sliding bearing moment free conditions. The  RADARSAT-1 range fixture offloading point was first designed to be at the center of the X-direction slides  with a constant-force spring offloading system. It completely failed. The 8.2-kg (1 8-lb) loading capacity  motor can not drive the panel to move up and down at all because of the internal friction of the constant  force spring and the large moment generated by the panel weight. The offloading point was finally moved  as close as possible to the panel CG and a balanced-weight system was used. The moment on the sliding  bearing was then removed. Before the motor installation, the moving force required to drive the panels up  and down were calibrated to between 5.5 kg and 7.5 kg. The analysis shown in Figure 9 gives suggestions  for offloading point selection.  34 1
CONSTANT F1  FORCE SPRING  Y DIRECTION MOTOR  M2 Br M3 lBkg MAX.  CAP AC I TY . L  L- L2  M=Fl*Ll +F2*L2 BALANCE  ,WE I GHT  SAR SINGLE PANEL  WEIGHT F2=250kg  Figure 9. Off loading Point Selection and Incorrect Offloading Point.  From above Figure 9, one can see that with balanced panel conditions:  The moment M on the Y bearing shall be: C M=O  M = F1 * L1 + F2 * L2  The Radarsat-1 constant force offloading line went through Y bearing  L1 =o  M= F2*L2  342