ai-aerospace/ams_data_full_2000-2020 huggingface dataset:
260 subset images show possible crack formations at x -coordinate X 1–4. Figure 7(b) shows significantly less  activity in the colormap produced by the edge detection algorithm, indicating lower risk of sub- surface  cracks. High friction is usually detrimental to sub- surface cracking. In starved lubrication conditions, the  efficiency improvement of P -SiSO over MAC is likely attributed to surface friction, and therefore it is  reasonable  to assume less sub- surface cracking.  

Figure 7. XMT analysis  indicates potential sub- surface cracking. Driven side dedendum (N ii) is critical  region. (a) MAC  show severe scuffing with large particles adhered at N ii, and evidence of subsurface  cracks in the same region (b) P -SiSO show less overall detected edges, and no evidence of scuffing.  

Conclusions  

• A hydrocarbon mimicking ionic liquid combined with multiply alkylated cyclopentane (P-SiSO) was  evaluated in geared actuators under starved lubrication conditions  in N 2 atmosphere.    • P-SiSO significantly reduced surf ace and sub- surface damage, while increasing gearbox efficiency.   • P-SiSO covered the gear with a thin tribofilm, comparison with model tribotest  indicates silicate.   • Surface roughness was clearly improved by P -SiSO, which likely improves (micro- )EHL conditi ons.   • XMT is well suited for damage analysis of s intered metal gears. T he porous structure is susceptible  to sub- surface cracking, which can be distinguished by XMT over the entire gear volume.  

Acknowledgements  

The "Austrian COMET -Program" in the frame of K2 XTribology (project no. 849109)  and The Taiho Kogyo  Research Foundation (TTRF) through the 2019 First Research Grant  provided funding of this work.  

References   [1] K. S. Novak, Y. Liu, C.- J. Lee, and S. Hendricks, “Mars Science Laboratory Rover Actuator Thermal Design,”  in 40th International Conf erence on Environmental Systems , 2010, pp. 1– 11.  [2] D. Suffern and J. Parker, “Developmental Bearing and Bushing Testing for Mars Gearboxes,” Aerosp. Mech.  Symp. , vol. 44, pp. 529 –541, 2018.   [3] D. J. Carré, “Perfluoropolyalkylether Oil Degradation: Inference of FeF3 Formation on Steel Surfaces under  Boundary Conditions,” ASLE Trans. , vol. 29, no. 2, pp. 121– 125, 1986.   [4] E. Nyberg, C. Y. Respatiningsih, and I. Minami, “Molecular design of advanc ed lubricant base fluids:  hydrocarbon- mimicking ionic liquids,” RSC Adv. , vol. 7, no. 11, pp. 6364– 6373, 2017.   [5] E. Nyberg, J. Mouzon, M. Grahn, and I. Minami, “Formation of Boundary Film from Ionic Liquids Enhanced by  Additives,” Appl. Sci. , vol. 7, no.  5, p. 433, 2017.   [6] J. Hansen, M. Björling, I. Minami, and R. Larsson, “Performance and mechanisms of silicate tribofilm in heavily  loaded rolling/sliding non- conformal contacts,” Tribol. Int., vol. 123, pp. 130 –141, 2018.   [7] ECSS, “Thermal vacuum outgassing test for the screening of space materials (ECSS -Q-ST-70-02C),” 2008.   [8] E. Nyberg, L. Pisarova, N. Dörr, F. Pagano, A. Igartua, and I. Minami, “Silicate- Forming Triboimprovers for  Multiply Alkylated Cyclopentane Base Fluids,” in 22nd International C olloquium Tribology , 2020, p. 1.
261 Development of a Universal and Scalable Mechanism Control Electronics  Configur ed to A pplication Solely  by Parameter  and Software C onfiguration 

Udo Rapp* and Juan Camilo Garcia Hernandez * 

Abstract  

Modern motor-driven high- precision mechanisms require  dedicated control e lectronics in order to achieve  their individual function, e.g. , position, velocity or acceleration control. The development of Mechanism  Control Electronics (MCE) is therefore often driven by  necessary  engineering development or  optimization tasks for this individual function rather than by economic and life- cycle requirements . 

The new concept of a universal Mechanism Control Electronics, co- funded by the German Space Agency  (DLR), breaks up with the e ngineering optimization approach as generally applied to each specific project  and demonstrates that one electronics unit is able to serve numerous mechanism applications at  minimized adaptation need.  

With  the presented development  of a new  control elect ronics , a versatile light-weight, low -power, low - volume and low -cost solution applicable to a large variety of different mechanism control requirements  could be realized.  

Introduction  

In the past decades, several generations of Mechanism Control Electronics have been developed  at  Airbus Defence and Space, including Solar Array Drive Electronics , Antenna Pointing Electronics for  LEO/GEO as well as Mechanism Control Electronics  for various science scanning and pointing   applications . 

Each of these drive electronics  has been a highly integrated unit with strong regard to volume/mass and  power budget and was adapted to the specific mechanisms and system requirements in order to optimize  the equipment function to the dedicated customer needs.  

The new c oncept breaks with the optimization for each single application and transfers all operation  modes, control loops and telecommand/telemetry functions into software  instead. In addition, the  interfaces to spacecraft and to the mechanism are implemented fully  flexible to be universal for different  mechanism/actuator types and for different spacecraft bus interfaces.  

This paper describes the collection of versatility requirements and the development performed on the  different Mechanism Drive Electronic m odules  with the resulting Electronics Demonstrator Model . The  "Application S ummary and Conclusion"  section contains the present status of the Universal Mechanism  Control Electronics and describes its flexibility with respect to the mechanism m otor characteristic s,  command/ telemetry  interface and specific function.     

* Airbus Defence and Space GmbH , Friedrichshafen, Germany   udo.rapp@airbus.com, juancamilo.garciahernandez@airbus.com  

Proceedings of the 45th Aerospace Mechanisms Symposium, NASA Johnson Space Center, 2020
262 Requirements Analysis  

The development work was  started with a requirements analysis to determine the key requirements  enabling a Control Electronics to become a universal  Mechanism Control Electronics. These  requirements include the following major technical key aspects:  

Primary power bus variability : Capability to operate at all standard primary power bus voltages,   i.e., 28V unregulated up to 50V regulated bus .  Power Drive capability:  DC/DC Converter and motor amplifier shall  be scaled to comply with the  majority of s pace mechanisms . An open archite cture for equipment with  higher power demand shall be granted.   Command/Telemetry variability:  The unit shall operate at all typical interface topologies,   i.e., Mil-Std-1553B, RS -422, SpaceWire, ML16/DS16, etc.   Eventual hardware m odifications for in terface- adaptation shall be kept to  an absolute minimum.   Operational Mode Control:  Handling of m echanism operational modes (e.g. , standby, movement,  autonomous functions) shall be completely handled in software.   Current - and Motion- Contr ol Loops:   Transfer of all motor current -, torque- , position- , velocity -control loops into  real-time- operating software.   Bandwidth target above 100 kHz (bandwidth to be distributed to all  control loops)   Mechanism Actuator Interface:  Interface to brushless -DC Motors, brushed- DC motors, Linear Actuators  or Stepper Motor s at only minor  and pre- defined hardware adaptation   Motor Filtering/Damping:  Motor mechanical characteristics differ significantly with respect to motor  type (stepper/BLDC/DC) as well as the motor electrical characteristics. It  is mandatory that the universal MCE either allows proper EMC  filtering /  damping for a high range of motors or, as an alternat ive, facilitate  adaptation to specific motor characteristics.   Position -Sensor Interface:  Interf ace provision to analog and digital, incremental and absolute optical  encoders. Interface to r eference switches, external and motor  internal  Hall Sensors.   Open Architecture:  Clearly defined interfaces to open the universal Mechanism Control  Electronics  to other  or new  mechanism and interface types.   Requirement Summary : One universal Mechanism Control Electronics shall be capable to serve  at least 90% of mechanism targets (major application bandwidth) without   or with minimized non- recurring  effort in hardware adaptation.   The open architecture shall allow the adaptation to the other 10% of  upcoming mechanism applications .
263   Figure 1: Universal MCE in cold redundant configuration 

Figure 2:  Core and Actuator Frame universal MCE  

Overall Architecture  

Housing definition   The MCE housing design is based on  module  frames for each module with  separate box outer walls. Flexibility to  missions with severe radiation  requirements can be achieved by  adding additional shielding thickness to  these box walls  (no change of  electronics parts due to changed  radiation requirements) . The unit  structural analysis shows first  resonance frequencies above 490  Hz in  all axes with sufficient margin to the  expected loads and confirms  the  selected “module frame approach” .   Both main and redundant unit s are  integrated within one enclosure,  separated by an internal aluminium  wall. 

MCE module distribution   Different concepts have been regarded  in order to achieve the distribution of  functions to the differ ent MCE printed  circuit boards. Following the major   requirement for useability in a majority  of applications, the modules have been  separated into   • Core Frame with the mechanism  controller  system and the interface to  primary power   • Interface Board as a plug- in module  to the Core Frame   • Actuator Frame with mot or ampl ifiers  and position sensor acquisition  circuits   The electrical interfaces between these  modules have been standardized to  allow the usage of different Interface   Boards  or Actuator Frames without  design adaptation needed on the Core Frame.  

Core Frame (DC/DC Converter, Controller System  and Software ) 

DC/DC Converter   Typical electronics units on a spacecraft provide dedicated building blocks to realiz e different spacecraft   primary power bus voltages . Associated engineering and design effort are frequently required to adapt  the unit , e.g., from 28V unregulated towards a 38V regulated power bus.
264 In order to avoid this adaptation from program to program, the Core Frame primar y bus interface has to  be able to cope with an enveloping input voltage range from 22V up to 5 2V without the need of any  commissioning or adjustment need. A new converter architectural concept has been established,  which  combines the MCE EMC input filter t ogether with sequenti al converters for a ctuator power and internal  supply. The galvanic isolation is maintained by this converter concept.  

Mechanism Controller System   Field  Programmable Gate  Arrays (FPGA)  with hard- coded firmware (VHDL)  are frequently use d in  Mechanism Control Electronics to combine the specific mechanism control and sensor  acquisition   interfaces with intelligent mechanism mode control and interface handling. In most cases, the motor  current controller or sensor analog acquisition circuits are kept analog and are adjusted for different motor  and sensor  characteristics.  

For a universal Mechanism Control System, it is mandatory to consequently transfer unit operational  functions and parameters into software, together with actuator control loops and motor current controller.  The selected architecture achieving a standardize d controller concept is depicted  in Figure 3. This  complete architecture has been introduced into one FPGA embedded system and completes the Core  Frame together with the DC/DC  Converter  defined above.  

Figure 3: Mechanism Controller System of Universal M CE 

Besides the logic blocks for command/telemetry interfaces and the actuators  and sensor  interfaces , the  major constituent is a dedicated processor system consisting of two processors plus a Floating Point Unit  (FPU).  An ARM -M1 processor is responsible for the mechanism functions and operation, whereas the  NanoProcessor together with the FPU performs all control  loop tasks in vi rtual real -time.  

The overall processing performance is 23 MIPs, 10 MFLOPs (32- bit-float) plus 1.11 MFLOPs  (trigonometric) which allows a control -loop bandwith of >100 kHz that can be distributed to current,  position and velocity control.
265 Software   The universal MCE s oftware has been developed following a software layer model. This allows  introduc tion of  new mechanism operational modes as well as additional real -time control loop tasks  without need of full software re- development. Basic operational modes are available but additional user - defined modes can be added without restrictions.  

Figure 4 shows the functional distribution of software modules and control loops to the two processor  system s and the interface of new modes/control -loop functions and para meters to the MCE software.  The  basic software blocks within the ARM M1 Processor and within the nanoProc remain unchanged for all  MCE appications.  

Memory / FPU / Trigonometric / Timers / Interfaces / Actuators / Sensors / ...ARM M1  ProcessornanoProc -  Interface TMTC -  Mode Control -  S/W Up-/Down-load -  FDIR -  ...All real-time tasks: -  Control Loops -  Hardware Supervision -  Actuator-Control -  Sensor read-out -  ...Mode ParametersControl ParametersNew ModesNew RealtimeTasks0 RUN1 WAIT2 DECEL LERAT E 3 SEEK 4 STOPSTOP CMD Modeswitch <> 5Start position reached End position reached ?STOP CMDModeswitch <> 5 Modeswitch <> 5 STDBYMODE 1..4 MODE 5STDBY CMD Step 1: Determine Modes of Operation  and Control Loop in Simulink Step 2: Transfer into ARM-S/W and realtime Tasks Step 3: Upload to universal MCE, Validation in Equipment

Figure 4: Distribution of Software to the two processors
267  Universal Core -ModuleCollection of Actuator-ModulesSelect Motor-/Sensor-Type

Figure 6: Different Actuator Frames can be connected to the universal Core Module 

Application Summary and Conclusion  

The concept for the Universal Mechanism Control Electronics and its development has been performed at  Airbus Defence and Space GmbH supported by the German Space Agency (DLR). The combination of a  Core Frame provid es a universal primary power interface and sufficient processing power for most  mechanism applications . Together with standardized control/data interfaces and mechanism  characteristics , the goal to serve a high number of different mechanisms with one archite cture has been  sucessfully reached. T he universal MCE provides a platform that can be configured in short term in  software / parameters  and by adaptation of the approriate Actuator Frame.  Figure 7 shows the workflow  for adaptation of the universial MCE to mechanis m types and mechanism characteristics.  

Development Status and First Integration Results  

Two models of the universal MCE have been buil t using the developed technology. One of these models  concentrated on validation of electrical design and performance validation with BLDC and DC motors in  different control loop scenarios.  

The second model already implements the mechanical modular architecture in the final MCE housing, the  environmental analysis for thermal, structural and radiation have bee n performed on this model.  Control  Loops for BLDC and DC  motors in complex motion profiles have been tested successfully and the f irst  demonstration of these models with different mechanism types is planned for the AMS 2020 symposium.
268 Universal Mechanic Control Electronics , configured for specific applicationActuator FrameFlexible SC Power -I/F  22V - 52V Data /Control I /F Type  „standard -1" Software  functions & control loop  parametersData /Control I /F Type  „standard -2" Data /Control I /F Type  „specific“ Stepper Actuator  Type „standard 1"Mechanism 1 Sensor „Hall -Effect“ Stepper Actuator  Type „standard 2"Mechanism 2 Sensor „Potentiometer“ BLDC Actuator  Type „standard 1"Mechanism 3 Sensor „Encoder“ Any Actuator  Type „specific 1"Specific Mechanism Sensor „Any“ select select selectstandard plug -in Core Frame Selection of I/F-Boards Selection of Actuator Frames select select select select SADM , 2-phase / 3-phase SADM BLDC (tracking / low noise ) MWI Instrument Scanning Mechanism MWHS Scanning with complex profile Linear Actuator SystemXAA, Data Downlink Pointing Mechanism Stepper Specific Actuator SystemWide Range of  Mechanical SystemsSelection of I /F-plug -in and Actuator Frame , Adaptation of Software and Control Loop Parameters

Figure 7: Adaptation flow of Universal MCE to m echanism targets
270 When eddy currents f low in a spinning metallic disk, they generate their own magnetic field that counteracts   the external ( source)  magnetic field. At sufficiently high speeds, the resulting total magnetic field   significantly reduces, and, hence,  the eddy current  related torque stays well below  the linear growth  observed at low speeds  [3]. 

Furthermore , a basic model  according to Eq. 1 may assume the disk material to feature a constant electrical   conductivit y. However, as the temperature rises due to Joule heating, the dis k’s electrical conductivity  decreases  (in an approximately linear  fashion, acknowledging the temperature coefficient of resistance) .  For many metals, this coefficient exceeds 0. 004/K , and therefore even small temperature changes   considerably reduce the electrical conductivity. Joule heating reduces the eddy currents in the spinning dis k  (by Ohm’s law). The consequences are mani fold: Lower  eddy currents decrease the resulting Lorentz  forces  and thus the resistive torque. However, they also generate a lower  counter acting magnetic field that  causes the total magnetic field to be higher  again . Hence, assuming constant speed, the spinning disk  system will reach  a steady -state equilibrium governed  by Maxwell’s equations together with the relevant  thermodynamic and mechanical effects and boundary conditions . In the following paragraphs, the analytical  and experimental  study with focus on the evolution of the resistive torque vs. speed is outlined.   

Model ling and Simulation  of a Simplified Case  

In the frame of the study, modelling and s imulation has been performed using the software tools ANSYS   Maxwell® and C OMSOL  Multiphysics®, with controlled modificati on of the parameters under investigation.  The model g eometry has matched the relevant parts of the eddy current test bench described in  the  following paragraph. The size  of the air gap has been parameterized for easy adjustment of the geometry.  Furthermore , the dis k thickness has been varied. Figure 1 shows the meshed geometry in ANSYS Maxwell®  including the materials  used.  

Figure 1 – Model configuration & mesh in ANSYS Maxwell® 

Many transient (time- domain)  simulation  runs have been carried out to study the sensitivity to parameter  changes ( in particular, dis k thickness, dis k material  & air gap dimension ), across the full speed range   (0…4000 rpm). The following model parameters  have been used for the simulation runs :  

● Air gap ( i.e. distance betw een the permanent magnets):  20…80 mm  (in 10 mm steps )  ● Materials  of the sample disks :    alumin um, copper  & stainless steel   ● Thickness  of the sample disks :    2 & 3 mm  

Permanent  Magnets  (NdFe35)   Vacuum   Variable Air Gap  Magnet Assembly  (iron)  Spinning Disk  (alumin um, copper,  stainless steel)
271 Serving as an example, Figure 2 shows  the simulation results in terms  of resistive  torque vs. disk speed. It  represents a case with a 2-mm copper d isk in a 40- mm air gap. As already indicated above, a linear trend  is observed in the low speed range ( here: below approx. 1000 rpm). At higher speeds and up to 3000 rpm,  the torque increases with a lower gradient . After passing a maximum, the torque starts decreasing in the  upper speed range. As suggested by theory, at high  speeds the induced eddy currents give rise to a  secondary magnetic field that opposes the primary one. Whilst at low speeds this effect remains small, the  counteracting magnetic field becomes significant and eventually leads to a drop of the resistive  torque. In  order t o confirm this effect , among others,  a dedicated test bench was  created.  

Figure 2 – Resistive torque vs. speed ( simulation results  for 2-mm copper dis k, 40-mm air gap)   

Eddy Current Test Bench  

The experimental objectives of the Eddy Current Test Bench (ECTB) have been to measure the resistive   torque and Joule heating ( due to eddy current dissipation) as a function of the speed of the rotating dis k  (driven by a brushless DC motor). Measured values have been  correlated with results obtained from two  independent models of the test setup ( in Maxwell  and COMSOL ), as well as a simplified analytical model.  The ECTB has been designed such that the parameters of Equation 1 are easily tweaked (e.g. , air gap  size, dis k thickness and dis k material). When the influence of dis k thickness was to be measured, individual  disks of identical material and geometry (apart from thickness) have been  compared. When the influence  of dis k material was to be measured, dis ks of identical geometry have been  compared. A simplified  geometry has facilitated th e experiments  as it has minimized the effect of unknown and unpredictable  factors that would otherwise have influenced  the test bench results . 

The ECTB has been  designed to provide a constant magnetic field using a variable air gap magnet. The  main components of the ECTB (as shown in Figure 3) are: 

● Rotating dis k (of different materials and thicknesses)   ● Motor drive assembly (brushless DC motor with casing , drive electronics and torque transducer )  ● Variable air gap magnet assembly   ● Translation stages  (for the variable air gap magnet  assembly ), including baseplate   -0.18-0.16-0.14-0.12-0.1-0.08-0.06-0.04-0.020 0 1000 2000 3000 4000Torque [Nm] Speed [rpm]
272   Figure 3 - ECTB experimental test setup  

One of the key results of the investigation has been the measurement of the eddy current related  torque  (see Figure 4) over a speed range sufficiently wide to observe t he predicted torque drop at high speeds.  The orange curve represents directly measured resistive  torque due to eddy current s (by subtracting the  measured non- magnetic los s torque  from the total measured torque). The curves obtained through the  Maxwell  and COMSOL  models are shown in green and blue,  respectively. As explained  below , different  conductivity values have  also been introduced into the models.  

Figure 4 - Correlated results of eddy current related  torque (2- mm copper dis k, 40-mm air gap)  

From a multiphysics point of view , the mechanical, electromagnetic as well as thermodynamic effects are  strongly intertwined in the case studied. Joule heating (eddy currents dissipating in the dis k) has been  shown to directly depend on the torque.  

Figure 5 (left side) presents data for a configuration of the ECTB for which the air gap has been minimized  to 35 mm (reaching motor limits) , in order to maximize the measured  torque and Joule  heating.   0.000.020.040.060.080.100.120.140.160.18 0 1000 2000 3000 4000 5000Torque [Nm] Speed [rpm]EC measurement Maxwell - 100% sigma Maxwell - 86% sigma COMSOL - 100% sigma COMSOL - 86% sigma Linear modelMaximum  Torque Low speed region   (appro x. linear)  Medium speed region   (nonlinear rise to maximum torque)  High speed region   (torque reduction)