astra 2015 design and development of an active landing...

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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

13/05/2015 DESIGN AND DEVELOPMENT OF AN ACTIVE LANDING GEAR SYSTEM

© 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.


© GMV, 2015

SYSTEM DESCRIPTION

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


© GMV, 2015

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

13/05/2015


© GMV, 2015

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


© GMV, 2015

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


© GMV, 2015

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


© GMV, 2015

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


© GMV, 2015

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


© GMV, 2015

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


© GMV, 2015

CONTROL SYSTEM (II)


© GMV, 2015

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


© GMV, 2015

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


© GMV, 2015

CONCLUSIONS

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


astra 2015 design and development of an active landing...

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