www.dlr.de Slide 1 MASCOT Asteroid Lander with innovative Mobility Mechanism Dr. Josef Reill German Aerospace Center - DLR Institute of Robotics and Mechatronics Team-Members: Josef Reill Hans-Jürgen Sedlmayr Philipp Neugebauer Maximilian Maier Erich Krämer Roy Lichtenheldt (Firmware, PM) (Electronics) (Electronics) (Electronics) (Mechanics) (Simulation)
www.dlr.de Slide 2 MASCOT Asteroid Lander with Innovative Mobility Mechanism Mission overview and involved institutes MASCOT components and science experiments Mobility subsystem developed by Institute of Robotics and Mechatronics Analysis and simulation by Institute of System Dynamics and Control - Simulation of the mobility principle - Mobility subsystem Summary Mechanics Electronics Health check data
www.dlr.de Slide 3 Hayabusa-II mission overview - Reach asteroid 1999JU3 and observe with remote-sensing instruments - Release landers (goal: find the most interesting spot to take samples) Two from JAXA and one lander is a contribution from DLR - Create an artificial crater on asteroid surface (small-carry-on-impactor) - Touch down and collect samples with the sampler - Earth re-entry vehicle with capsule will be sent back to earth -Image courtesy: JAXA
www.dlr.de Slide 4 Hayabusa-II mission overview MASCOT (Mobile Asteroid Surface Scout): Lander unit is a DLR contribution to Hayabusa-II of JAXA Target: Asteroid 1999JU3 Launch: 03. Dec. 2014 Arrival: ~ July 2018 Return: 2020 10.96 kg with the size of 30 x 30 x 20 cm Target Body 1999 JU3 Properties: C-Type Asteroid (NEA) Spherical with diameter approx. 920 m Gravity approx.: 17 e-6 g Escape speed: 23 cm/sec MASCOT Requirements: Carry four science instruments MASCOT is the scout for JAXA s sample return experiment Relocate on asteroid surface and up-right into nominal position (needed by science instruments)! -Image DLR-RY -Image courtesy: JAXA
www.dlr.de Slide 5 MASCOT involved institutes DLR-RY Institute of Space Systems DLR-PF Institute of Planetary Research DLR-RB DLR Institute of Space Operations and Astronaut Training DLR-FA Institute of Composite Structures and Adaptive Systems CNES Centre national d études spatiales Telespazio VEGA IGEP (TU Braunschweig Germany) IAS Institut d Astrophysique Spatiale JPSEC & ISAS/JAXA DLR-RMC Robotics and Mechatronics Center Management, System, GNC, Harness, AIV&AIT, PA MSC CAM, MARA infrared radiometer Ground Segment, Operations MASCOT Structure Power (PCDU + Battery), Antenna OBC MAG Magnetometer MicroOMEGA near infrared hyperspectral microscope CCOM Mobility
www.dlr.de Slide 6 MASCOT components and science experiments Radiometer CAM Mobility -Images DLR-RY MicrOmega Magnetometer System development time 2010-2014 Compact system with four experiments Battery, E-Box and infrastructure is about the same volume as payload Mobility is one of the first subsystems to be integrated! Very high integration effort!
www.dlr.de Slide 7 Simulation of the Mobility Principle - SR No drive wheels because of asteroid surface uncertainties and µg Based on the reactive force generated by an eccentric arm Asteroid parameters based on current knowledge and will be updated Model verified by parabolic flight campaign as well as reaction force measurements applicable frequency range: 3-25Hz Automated optimization to find suitable trajectories (computation is done offline and trajectories will be updated before descend of MASCOT) Multi-criterial optimization strategy ensures fastest settling and avoidance of reaching the escape velocity Sensitivity analysis and investigations of bouncing after locomotion First results: increase of first impact jumping distance
www.dlr.de Slide 8 Simulation of the Mobility Principle - SR
www.dlr.de Slide 9 Mobility Subsystem Overview
www.dlr.de Slide 10 Mobility Subsystem Redundancy Concept Two cold redundant signal paths on electronics side Mechanics not built redundant due to space & weight limitations Malfunction of one redundancy path may lead to short circuit path! One additional MOSFET to separate the two redundancy paths No unintentionally short circuit between the nominal and redundant side will occur
www.dlr.de Slide 11 Mobility Subsystem MobCon Top-Side of PCB FPGAs in CCGA package with temperature sensor (1) Line-Drivers RS422 (2) 12 bit / 8 channel ADC (3) Current measurement OP-AMPs (4) Motor connectors (5) Size: 95 mm x 105 mm x 18 mm Bottom-Side of the PCB Motor controller (automotive) with temperature sensor (1) Radiation tolerant and ITAR free MOSFETs (European Component initiative ECI) (2) Shunt-resistors and filters (3) 3-phase motor choke (4)
www.dlr.de Slide 12 Mobility Subsystem MobCon -MASCOT FM Mobility without eccentric arm Motor cables are a challenge! (position, length, ) E-Box with partly mounted PCBs (OBC and mobility) Reprogramming of FPGAs is not possible in E-Box! Assembling MASCOT took several weeks (DLR-RY) -MASCOT E-Box, Image DLR- RY
www.dlr.de Slide 13 Mobility Subsystem MobUnit Mobility Subsystem: Electrical drive accelerates and decelerates an eccentric mass Because of resulting reactive force jerk is applied to system => MASCOT hops As much redundant system as possible (up-righting is essential!) Compact subsystem with high power density As small and light as possible! Powerful drivetrain is available at the Institute of Robotics and Mechatronics since there was the ROKVISS and DEXHAND project! ILM25 RoboDrive Motor Ø 25 mm x 10 mm Harmonic Drive HFUC8 Weight 112 g motor + 137 g eccentric arm Output torque 3 Nm 8000 rpm (HD limited) Unit-Size: Ø 31 mm x 64 mm + eccentric arm 85 mm -MobUnit CAD sectional drawing
www.dlr.de Slide 14 Mobility Subsystem MobUnit Motor and eccentric arm mechanics: BLDC Motor with six-step-commutation Harmonic drive gearing 1:30 Eccentric arm with mass Reference magnets to get the absolute position of the eccentric arm via hall sensors Redundant sets of cables (power and signal) - low number of mechanical parts - higher torque output compared to DC motors - No brushes or sliding contacts - High peak torque for short time MLI-Standoff Holder for 2x Ref. Hall Sensors -MobUnit CAD drawing -FM MobUnit
www.dlr.de Slide 15 MASCOT Flight Model in June 2014 (Bremen) Image DLR RY
www.dlr.de Slide 16 Hayabusa-II Launch 03rd Dec 2014 H-IIA F26 with the Asteroid Explorer "Hayabusa-II" onboard launched at 05:22 on Dec 3, 2014 (CEST) from the Tanegashima Space Center
www.dlr.de Slide 17 MASCOT Health Check 16th Dec. 2014 -Recorded data: Go to start position maneuver Data of the flight model before (red signal plot) and after launch (blue signal plot) in direct comparison. Friction is increased due to temperature difference of ~20 degrees and vacuum conditions Motor dynamics limited (MASCOT is actually inside of Hayabusa-II) No launch lock was applied and eccentric arm did not move during launch (Harmonic Drive gearing 1:30) -Recorded data: Start movement maneuver System and mobility subsystem checks were all successful!
www.dlr.de Slide 18 Summary of MASCOT contribution New mobility concept for low gravity planetary body exploration realized Development of simulation environment to prepare offline optimized trajectories Mobility FM and FS assembled and delivered to DLR-RY for integration High power density drive unit & motion controller with redundancy path High reliability due to less mechanical parts (health checks successful) Module may also be used in other applications (Pan-Tilt-Mechanism)