dr. josef reill german aerospace center - dlr institute of robotics and...

Dr. Josef Reill German Aerospace Center - DLR Institute of Robotics and Mechatronics

Team-Members:

Josef Reill (Firmware, PM) Hans-Jürgen Sedlmayr (Electronics) Philipp Neugebauer (Electronics) Maximilian Maier (Electronics) Erich Krämer (Mechanics) Roy Lichtenheldt (Simulation)

MASCOT Asteroid Lander with innovative Mobility Mechanism

www.DLR.de • Slide 1 > 11.05.2015 > MASCOT – Asteroid Lander with innovative Mobility Mechanism > [email protected]

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

Mechanics

Electronics

Health check data

• Summary

> 11.05.2015 > MASCOT – Asteroid Lander with innovative Mobility Mechanism > [email protected]

- 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


Hayabusa-II mission overview

-Image courtesy: JAXA



Hayabusa-II mission overview

-Image courtesy: JAXA


-Image DLR-RY

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)!


MASCOT involved institutes

DLR-RY Institute of Space Systems Management, System, GNC, Harness, AIV&AIT, PA

DLR-PF Institute of Planetary Research MSC CAM, MARA infrared radiometer

DLR-RB DLR Institute of Space Operations and Astronaut Training Ground Segment , Operations

DLR-FA Institute of Composite Structures and Adaptive Systems MASCOT Structure

CNES Centre national d’études spatiales Power (PCDU + Battery), Antenna

Telespazio VEGA OBC

IGEP (TU Braunschweig Germany) MAG Magnetometer

IAS Institut d’Astrophysique Spatiale MicroOMEGA near infrared hyperspectral microscope

JPSEC & ISAS/JAXA CCOM

DLR-RMC Robotics and Mechatronics Center Mobility



MASCOT components and science experiments

• 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!

-Images DLR-RY


Mobility

Magnetometer

CAM

MicrOmega

Radiometer


• 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

Simulation of the Mobility Principle - SR

Simulation of the Mobility Principle - SR


Mobility Subsystem – Overview



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

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


Mobility Subsystem – MobCon


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)


Mobility Subsystem – MobCon

• 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

-MASCOT FM Mobility without eccentric arm


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

- low number of mechanical parts - higher torque output compared to DC motors - No brushes or sliding contacts - High peak torque for short time

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)


Mobility Subsystem – MobUnit


-MobUnit CAD drawing

-FM MobUnit

Holder for 2x Ref. Hall Sensors

MLI-Standoff


MASCOT Flight Model in June 2014 (Bremen)

Image DLR RY


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

MASCOT – Health Check 16th Dec. 2014


-Recorded data: Go to start position maneuver

-Recorded data: Start movement 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)

System and mobility subsystem checks

were all successful !


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)

dr. josef reill german aerospace center - dlr institute of robotics and...

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