s im u la t io n a n d a n a ly s is o f d o c k in g m a

w w w . k a y s e r - t h r e d e . c o m

E a r t h

S p a c e

&

F u t u r e

Von der Erde ins All . Und zurück.

Intelligente Lösungen fürIndustrie und Wissenschaft.

From Earth to Space. And back.

Intelligent solutions for industry and science.

Kayser-Threde GmbH Simulation and Analysis of Docking Maneuvers in GEOSven O. Erb, Kayser-Threde

Rainer Krenn, DLR

October 05, 2006

Space Technology & Applications

Science & Earth Observation

Process Control Systems

Automotive

15/09/20062 Simulation and Analysis of Docking Maneuvers in GEO Space Technology & Applications

Outline of the Presentation

! The Docking Payload of the Orbital Recovery System ORS

! Fundamental Need for Docking Simulation and Analysis Capabilities

! Design Simulation Facility – Docking Modules

! Polygonal Contact Dynamics

! Practical Experience

! Benefits & Outlook


ORS – Orbital Recovery System (formerly CX-OLEV)

! Attitude and orbit control services for several years after rendezvous and docking of the service satellite

! Orbit maneuvers (control and orbital changes, e.g. transfer to the so called graveyard orbit for discarded satellites)

Other robotics heritage of Kayser-Threde:

! ROKVISS,

! TECSAS,

! AROMA,

! etc.

in strong partnership with the DLR Institute of Robotics & Mechatronics.


Kayser-Threde Responsibilities as Docking Payload Prime

! Kayser-Threde is payload prime for the complete docking payload subsystem needed for approach, capturing and locking of the client satellite

! Main docking payload components: Capture Tool, Target Illumination and Stereo Camera System, as well as the Deployment and Client Support Mechanisms


Different Phases of the Docking Maneuver

Previous Phases:! Transfer from GTO to GEO box,! Rendezvous (Far-Approach) to within a few meters distance from the client spacecraft.

Docking:! Near-Approach: From an intermediate position to the envelope of the client spacecraft,! Insertion: The capture tool is deployed and inserted into the AKM nozzle,! Capturing: Capture tool makes first contact with the client and further inserts into the throat

of the AKM nozzle,! Locking: The locking device then ensures a steady connection with the client,! Retraction: The two spacecraft are pulled together for tightening of the connection, ! Coupling: Firm coupling of the two spacecraft in order to reach operational readiness.


Docking Maneuver – Challenging Conditions

! Zero gravity – free floating/flying! Possibly active AOCS on both s/c! S/C masses are in the order of tons! Limited accuracy of s/c relative position and

orientation information! Ground-loop related time delays ! Impulse transfer at contact! Effectiveness of elastic components! Failure scenarios


Docking Maneuver – Key Requirements

Main Objectives:! Prevent the ORS from damaging the client,! Interrupt regular operation of the telecommunications satellite for as short as possible,! Minimize the contact-induced acceleration of the two spacecraft,! Allow safe and reliable operation of the docking mechanism,! Ensure successful capturing under off-nominal conditions, providing sufficient margins

Which means: Find the best possible, feasible docking solution with respect to ! Hardware design,! Operational strategy.

" This calls for advanced analysis!


Design Simulation Facility DSF

Development of the DSF:! Dutch Space (Satellite Bus, Environment)

! Sener (AOCS)

! Kayser-Threde / DLR (Docking Payload Model, Contact Dynamics)


DSF Basic Features

Implemented in Matlab/Simulink:! Orbital dynamics,! Environmental system,! Satellite databasefor the ORS spacecraft and the client spacecraft,

the DSF serves! the design and development of control algorithms for the transfer,! general mission analysis purposes.


Docking Payload & Contact Dynamics Module of the DSF

Orbit Dynamics

AOCS Model

Docking Payload & Contact Dynamics


DSF Docking Payload Models

Contact bodies are represented by polygon meshes (CAD):! Capture tool body,! Client support mechanism,! Client nozzle.

Individual polygon properties:! Polygon size and normal vector,! Stiffness and damping coefficients,! Friction coefficient (Coulomb friction).


Polygonal Contact Dynamics

The contact force vector is composed of:! Normal spring forces as function of the contact surface penetration,! Normal damping forces as function of the relative normal velocity

between the contact surfaces,! Tangential friction forces as function of the relative tangential

velocity between the contact surfaces.

The tasks of the contact model:! Identification of surface polygons which are actually in contact,! Calculation of the relative motion states at the contact surface,! Calculation of the contact forces at the contact surface,! Application of these forces to the corresponding bodies.

Further aspects:! Automatic polygonal mesh refinement,! Compliance with minimum energy objective.


Docking Payload - Deployable Boom Model

Discrete approximation with finite number of segments:! Rigid links,! Flexibility represented by spring/damper suspended 6-DOF joints between the links,! Parameters (bending stiffness, torsion stiffness) are derived from bread-board measurements.Bending, torsion, longitudinal and lateral strain,Shape of deformation subject to minimum energy constraint.


Simulation of Capture Tool Insertion into the AKM Nozzle


Analysis of Limit Switch Force vs. AOCS Trade-Off I/IV

0 1 2 3 4 50

1

2

3

4x 10-3

Time [s]

Boo

m V

el. [

m/s

]

0 1 2 3 4 51.415

1.42

1.425

1.43

Time [s]

Rel

. x-p

os C

T-C

L [m

]

0 1 2 3 4 50

1

2

3

4

Time [s]Li

mit

Sw

itch

Flag

s

0 1 2 3 4 5-1

-0.5

0

0.5

1

Time [s]

CT

Con

tact

For

ce X

[N]

Force free activation; active AOCS

! Four limit switches,

! Force free activation,

! Active AOCS.




! Activation force 2N each,

! Active AOCS.

0 1 2 3 4 50

1

2

3

4x 10-3

Time [s]

Boo

m V

el. [

m/s

]

0 1 2 3 4 51.415

1.42

1.425

1.43

Time [s]

Rel

. x-p

os C

T-C

L [m

]

0 1 2 3 4 50

1

2

3

4

Time [s]Li

mit

Sw

itch

Flag

s

0 1 2 3 4 5-3.5

-3

-2.5

-2

-1.5

-1

-0.5

0

Time [s]

CT

Con

tact

For

ce X

[N]

Force free activation; active AOCSActivation force is 2N each; active AOCS



0 1 2 3 4 50

1

2

3

4x 10-3

Time [s]

Boo

m V

el. [

m/s

]

0 1 2 3 4 51.415

1.42

1.425

1.43

Time [s]

Rel

. x-p

os C

T-C

L [m

]

0 1 2 3 4 50

1

2

3

4

Time [s]Li

mit

Sw

itch

Flag

s

0 1 2 3 4 5-4

-2

0

2

4

6

8

Time [s]

CT

Con

tact

For

ce X

[N]

Force free activation; active AOCSActivation force is 2N each; active AOCSActivation force is 2N each; inactive AOCS



! Inactive AOCS.



0 1 2 3 4 50

1

2

3

4x 10-3

Time [s]

Boo

m V

el. [

m/s

]

0 1 2 3 4 51.415

1.42

1.425

1.43

Time [s]

Rel

. x-p

os C

T-C

L [m

]

0 1 2 3 4 50

1

2

3

4

Time [s]Li

mit

Sw

itch

Flag

s

0 1 2 3 4 5-4

-2

0

2

4

6

8

Time [s]

CT

Con

tact

For

ce X

[N]

Force free activation; active AOCSActivation force is 2N each; active AOCSActivation force is 2N each; inactive AOCSActivation force is 1N each; active AOCS



! Active AOCS.


Benefits of the Docking Simulation Capability

Provision of an environment for end-to-end simulation of the docking maneuver:! Approach, insertion, capturing, retraction, coupling;! Uninterrupted, with a single tool and abundant analysis outlet.

Utilization for the assessment of parameter sensitivities and design trade-offs:! Positioning and characteristic properties of various distance sensors,! Performance requirements of the locking device,! Performance margins of the operational strategy under off-nominal conditions.

Supports the identification of:! Design enhancements (e.g. motorization of the locking device, limit switches), ! Potential failure sources (e.g. contact force effects, deadlock),! Design trade-offs (e.g. design costs versus operations risks).

It enables the testing of docking strategies at a very early stage of design and development, which reduces design and development costs.


Outlook

Kayser-Threde and DLR have developed an expertise in the simulation and analysis of spaceborne docking maneuvers, which is now available for use in succeeding project undertakings.

Verification of Docking Payload functional performance will be conducted in a real-time HIL environment on the basis of EPOS (European Proximity Operations Simulator) in conjunction with EUROSIM.

Physical docking will be performed with EQM grade Docking Payload models.

Cross-verification of the Docking Simulator by comparative analysis of HIL-simulated and software simulated docking maneuvers.


Docking Simulations

- MOVIE -

s im u la t io n a n d a n a ly s is o f d o c k in g m a

Documents