astra 2015 design and development of an active landing...
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© GMV, 2015 Property of GMV
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DESIGN AND DEVELOPMENT OF AN ACTIVE LANDING GEAR SYSTEM
ASTRA 2015
© GMV, 2015
The work presented here is part of the REST project Ongoing project funded under ESA MREP program
– Preliminary design level (6 months in the activity)
Objective of the project: – Designing an actively compliant landing gear for low gravity
environments (Phobos) and developing and testing a scaled prototype of it
– Aplication to ESA Phootprint mission
GMV, AVS-UK and CBK-PAN are working together on actively compliant landing gear for Phootprint – Active compliant electro-mechanical design – Control system – Simulation & testing
REST PROJECT
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© GMV, 2015
REST international consortium
GMV Romania – Prime contractor – Requirements – FES development and simulations – HW procurement – Results corellation
CBK – Dynamic analysis – Control system responsible – Testbed development and testing
AVS-UK – Concept selection and trade-off – Preliminary and detalied sytem design – AIT&AIV
PROJECT TEAM
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PHOOTPRINT MISSION DESCRIPTION
Candidate mission of the Mars Robotic Exploration Preparation (MREP) Program
Main objective is acquiring and returning a sample from Mars moon Phobos
One of the first steps is the characterization phase of the moon and of the landing site
Complex Mission Schematic.
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SYSTEM DESCRIPTION
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Phootprint Pre-Phase A System Study – Airbus DS UK
– Compact Spacecraft Composite, made of 3 main modules – Lander Module – Earth Return Vehicle – Earth Re-Entry Capsule
Phootprint Pre-Phase A Study –
TAS-I – An additional module for the transfer phase from Earth to Phobos: Propulsion Module – Lander Module – Earth Return Vehicle – Earth Re-Entry Capsule
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GOAL FUNCTIONS
Impedance controlled absorption of the impact/settling forces: No crash at landing
– Low center of gravity – Maximize distance between landing feet – 0.1m (TBC) soil penetration as starting point – Avoid obstacles (max boulders 50cm)
No tip-over at landing No rebound after landing
– Avoid restitution of damped energy – find means to transform/ disipate/store the energy pasively through shock alleviation techniques or activelly through controlled actuators
Rejection of vibration induced by sampling devices Releveling of the lander Deployment of landing legs (stowed during launch & flight)
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MAIN REQUIREMENTS
Safely land and remain on Phobos (one landing) Velocities: 0.6-1m/s vertical; 0.2m/s horizontal Angular rate: max 5 deg/s on all axes Total energy to be absorbed aprox. 1000J, peak during 1st sec 2000N impact force (peak); 800Nm impact torque
Always maintain a positive or zero velocity towards Phobos surface Provide 50 cm clearance to ground for Surface Platform Absorb forces and torques generated during sampling operations and
maintain contact with Phobos surface Drilling: 15N, 10Nm Robotic arm: aprox 10kg (400 g at the end effector), 1.5 m workspace Robotic arm speed: 0.7 deg/s Hold-down thrust of 20N Sloshing due to ERV & remaining fuel in Lander
System to be compatible with Ariane 5 and Falcon 9 40 kg, TBD power, no critical allowable volume restrictions Operational for minimum 120min (continuous) 3 day/night cycles
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DESIGN AND DEVELOPMENT OF AN ACTIVE LANDING GEAR SYSTEM
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SOIL/ENVIRONMENT CHARACTERISTICS
Parameter Value
Surface temperature - Minimal - Maximal - Mean
130K (-143°C) 300K (+27°C) 215K (-58°C)
Temperature amplitude - Diurnal - Seasonal
180°-200°C 20°C
Regolith density - 1st type regolith - 2nd type regolith - 3rd type regolith
1.1 g/cm3 1.6 g/cm3
1.35 g/cm3
Regolith grain size 35-85μm
Thermal conductivity - Minimal - Maximal - Mean
1.8x10-6 cal/cm-s-grad 5.55x10-5 cal/cm-s-grad 1.65x8x10-5 cal/cm-s-grad
Soil property Value Value
Loose material vs. solidified surface Applicable is loose material
Compressive strength
Applicable to individual pebbles 0.3 up to 30 Mpa
Special case (I) pebbles larger than sampling tool
Cut (0.3 to 30 MPa) or move particles
Special case (II) solid surface
Optional, as an asset, mechanism needs to break through surface (0.3 – 30 MPa)
Bulk density (sample material). Derived parameter from: a) bulk composition b) bulk porosity of whole body c) bulk porosity of an individual lithology d) surface regolith properties.
1 – 2.2 g/cm3
Sampled grain size μm to 3 cm
shape Any (eg. Rounded, tabular, elongated)
Intra particle cohesion 0.1 – 5 kPa
Angle of friction 20º – 40º
Surface temperature range 0 to -120 ºC
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STATE OF THE ART REVIEW
Proposed concepts & preliminary trade-off Option A: Legs with 3 translational DoF Option B: legs with 2 rotational DoF Option C: Legs with 1 rotational DoF + 1 translational DoF
Option A Option B Option C
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CONCEPTS TRADE-OFF
The selected configuration consists of – A main active strut – Two secondary passive struts linked to the lander structure by means of one each spherical joint
Connection between the main and secondary struts by spherical
joints Spherical joint with the foot pad and primary structure Active translational DoF in the axial direction of the main struts
– The main strut absorbs the impact/settling forces and compensates of residual elasticity – The secondary passive struts damp the lateral loads acting on their respective legs.
After landing, all translational actuators can be used to level the landing platform and they also serve as active dampers for rejection of vibration induced by sampling devices and fuel sloshing
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SYSTEM DESIGN & BREADBOARDING
Active landing systems review
Active Shock Absorber
The ALISE landing mechanism and its anchoring system
Soft-landing dynamics of four-legged lunar lander
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PROPOSED SOLUTION
Mechanical proposed solutions & preliminary design Rotational actuator to achieve linear displacement Direct Linear actuator concept
DYNAMIC PART (AXIAL MOVEMENT)
STATIC PART
Slide units Linear motor magnets (dynamic part)
Linear motor coiling (static part)
Rotating nut
Angular contact ball bearings
Motor stator (yellow)
Motor rotor (black)
Transmission shaft
Ballscrew
STATIC PART
DYNAMIC PART (AXIAL MOVEMENT)
ROTATING PART (NO AXIAL MOVEMENT)
Preloading nut
Optical encoder
Bushings
The complete active landing system would consist of four main struts or legs equipped with a linear actuator
The main leg will also include one force sensor for the impedance control closed loop implementation
Deployment function and releveling will be studied during the activity
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CONTROL SYSTEM (I)
Noninear PD / Impedance control Sensors: actuator encoders, base acceleration/velocity, force
sensor (foot) Nonlinear coupling control for ground form adaptation
Actuators: reference motor currents
Nonlinear impedance control – state feedback State: actuator configurational displacement (4 variables) and its velocity (4 variables) First iteration algorithm: Nonlinear PD simulating elasticity with coulomb and viscous friction
Measured signals Leg actuator position, foot contact, lander accleleration
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CONTROL SYSTEM (II)
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SIMULATION - REST FES
Simulator for multi-body analyses: Interaction between sampling tool-soil Forces and torques transmited to the
S/C from sampling tool AOCS capability to stabilize the system Interaction REST system-soil Monte-Carlo capability (GNCDE)
REST high fidelity simulator includes the following elements:
Phobos models: gravity, specific soil interaction models, Lander dynamics: main spacecraft dynamics including fuel sloshing, forces
from thrusters and from sampling tool; reuse of GMV Simulink libraries REST mechanism: multibody simulation of the 4 legs and all the composing
elements, including the control of the active actuators.
The REST FES will be tuned in during the system design and developement and after experimental test
Use of in-house available SpaceLab libraries
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TESTBENCH DESIGN Ground Mockup
REST prototype
Granite table
Launcher
1
2
3
5
Cart 4
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PROTOTYPE DESIGN
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REST DESIGN VERIFICATION AND VALIDATION
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Preliminary design – Finalizing concept trade-off: configuration, actuator type – Verifying selected concept in FES
Detailed design
– Perform multiple simulations (including Monte Carlo) – Adapt system design to prototype & perform scaling down
Prototype manufacturing and AIV/AIT
Testing & corellation of results
– Validate FES and system design against requirements – Technology roadmap – way forward
FUTURE WORK
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CONCLUSIONS
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Preliminary dynamic analyses show good performance of the cantilever configuration
Actuator selection depends on maximum impact energy and required efficiency
Preliminary design of the landing gear mechanical structure and actuators shall be parameterized by means of geometry, mass and elasticity distribution, and actuators parameters
Toppling analyses for the worst case scenario influence the configuration selection – Preliminary results indicate an increase in footprint may be needed – Preliminary baseline is 4 legged configuration
Validation of concept through FES – Soil contact model critical – Simulation and testing of sampling/sloshing vibrations important aspect in
validation & raising the system TRL Result correlation need to account for scaling down – scaling up of the
test prototype – Sloshing and vibration effects + residual elasticity in the structure
13/05/2015
DESIGN AND DEVELOPMENT OF AN ACTIVE LANDING GEAR SYSTEM
© GMV, 2015 Property of GMV
All rights reserved
Thank you Cristian Chitu (GMV) Karol Seweryn (CBK) Cristina Ortega (AVS-UK) For more information: [email protected]