Laboratory experimental validation of autonomous spacecraft proximity maneuvers

Prof. Marcello Romano

Mechanical & Astronautical Engineering DepartmentU.S. Naval Postgraduate School, Monterey, California, USA

mromano@nps.edu

IEEE ICRA, April 2007

Spacecraft RoboticsLABORATORY

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1. Tasks and motivation 2. The Spacecraft Proximity Operations Facility3. The 1st-generation spacecraft simulators 4. The 2nd-generation spacecraft simulators5. Conclusions

Outline

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Design and build a Hardware-In-the-Loop test-bed to validate GN&C algorithms for the proximity operations of small spacecraft, including autonomous docking and multi-spacecraft assembly

Task and rationale of the on-going Researches

1960- Russian missions1997-99 Japan ETS-VII2001 China-UK Snap 12003/05 AFRL XSS-10/112005 Nasa DART 2007 DARPA Orbital Express2007 ATV to ISS2010-… NASA Project Constellation

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4.9 m by 4.3 m Epoxy SurfaceS/C simulators float via air-padsDynamics + Kinematics simulator

1. Recreates weightlessness and frictionless condition in 2D 2. Angular/linear momentum conservation respected3. Enables validation of Dynamics model and GNC algorithms, while they

interact with real actuators/sensors/internal body motion dynamics4. Complementary to 3D analytical-numerical simulations &

kinematics-only simulation facility

(Residual Gravity: ~10-3 g)

Proximity Operations Facility @ Spacecraft Robotics Lab

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1st-generation Spacecraft Simulators (AUDASS)

Camera

Batteries

Reaction Wheel

Docking I/F(Active portion)

IMU

Thruster (1 of 8)

Docking I/F(Passive portion)

I/R LEDs

Chaser Spacecraft Simulator

Target Spacecraft Simulator

Tank

Control PC

Vision PC

Epoxy Floor

1 mstick

Camera

Batteries

Reaction Wheel

Docking I/F(Active portion)

IMU

Thruster (1 of 8)

Docking I/F(Passive portion)

I/R LEDs

Chaser Spacecraft Simulator

Target Spacecraft Simulator

Tank

Control PC

Vision PC

Epoxy Floor

1 mstick

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CMOS Camera

Image Processing

Distortion Compensation

R components and θ

Camera intrinsic parameters and distortion coefficients estimated

through off-line calibration

Thruster Pair IV

Chaser vehicle

Target θ

R

CoMtg

CoMch Xch

Zch

Ych

XtgZtg

Ytg

//Xch

LED 1

LED 2

LED 3

Z’tg

Thruster Pair III

Thruster Pair IDocking I/F

X’tg

CameraReactionWheel

D

Ond

1st-generation simulator: Vision Based Navigation

Resulting accuracy in position = ~1 mm, in angle = ~0.1 degResulting overall sample frequency = ~5 Hz

Pinhole Camera Model

3-Points Based Navigation

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[ ] , T

k k k k kθ γ θ= =x u

[ ] [ ] [ ][ ]( ) ( ) ( )[1 0], k delay k k delay k cam k delay kH vθ− − −= =v

Ttg tg tg tg

k ch k ch k x k ch k ch k z kx x z zβ β= ⎡ ⎤⎣ ⎦x

[ ]T

k k kx z=u

[ ]

[ ] [ ] [ ][ ]

( )

( ) x ( ) z ( )

1 0 0 0 0 0,

0 0 0 1 0 0

.

k delay k

k delay k cam k delay k cam k delay k

H

v v

−

− − −

=

=

⎡ ⎤⎢ ⎥⎣ ⎦

v

Attitude

Translation

Discrete Kalman Filters implementation for the relative navigation, fusing vision and IMU data

1st-generation simulator: Fusing Vision Sensor and IMU Data

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PD

ChaserSpacecraftSimulator

Vision/InertialNavigation

Reaction Wheel

Reference Signals

Schmitt Trigger PD

PD

ThrusterMapping

Thruster Pairs I/II(along Xch)

PWM

Schmitt Trigger

yTSTxI

STzI( )tgchzΔ

( )tgchxΔ

Thruster Pairs III/IV(along Zch)

PWM

θΔ

1st-generation simulator: Chaser Spacecraft Control

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1st-generation simulator: Test 1: Trajectory Tracking

0 A 50 100 150 200 250

−10

−5

0

5

10

time [s]

θ [d

eg]

Relative attitude of Target w.r. to Chaser

ReferenceActual

−101

Jets’ thrust along Xch

[0.9⋅N]

−101

Jets’ thrust along Zch

[0.9⋅N]

0A 50 100 150 200 250−0.02

00.02

RW Torque about Ych

[N⋅m]

time [s]

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1st-gen. simulator: Test 2: Autonomous Docking Maneuver

MOVIE

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1st-gen. simulator: Test 2: Auto. Docking Maneuver (details)

0 A B 50 C 100 150 D E

0

0.1

0.2

0.3

time [s]

tg x

’ ch [

m]

Chaser CoM position

ReferenceActual

0 A B 50 C 100 150 D E−15

−10

−5

0

time [s]

θ [d

eg]

Relative attitude of Target w.r. to Chaser

ReferenceActual

−0.4

−0.2

0

Accelerometers’ data [m⋅s−2]

Alo

ng X

ch

0 A B 50 C 100 150 D E

−0.10

0.1

time [s]

Alo

ng Z

ch

Raw OutputEstmtd. Bias

0 A B 50 C 100 150 D E−1.5

−1

−0.5

0

time [s]tg

z’ ch

[m

]

Chaser CoM position

ReferenceActual

−101

Jets’ thrust along Xch

[0.9⋅N]

−101

Jets’ thrust along Zch

[0.9⋅N]

0 A B 50 C 100 150 D E−0.02

0.020.06

RW Torque about Ych

[N⋅m]

time [s]0 A B 50 C 100 150 D E

−5

0

5

time [s]

Alo

ng Y

ch

Gyro’s data [deg⋅s−1]

Raw OutputEstmtd. Bias

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2nd-generation Spacecraft Simulator

LIDAR

iGPS sensor

3000 psiAir Cylinders

4 Air Pads

3 Li IonBatteries

Router

Dual PC104

Dual MSGCMG

DualVectorableThrusters

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2nd-generation Spacecraft Simulator [ctnd]

Mini Control Moment Gyroscopes One of the two rotating thrusters

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2nd-generation simulator: attitude dynamics

Equation of motion for a rigid spacecraft with a CMG

H vector takes into account both main vehicle and CMG angular momentum

The torque from the CMG is

The CMGs’ steering law is

s s ext+ × =H ω H T

s = +H Jω h[ ]T0,cos ,sinwh δ δ=h

ZZ Z CMG Z Z= = − =J ω T h u

Z ZcosWh δδ= = −h u

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2nd-generation simulator: rotational dynamics

State Variables

Control Parameters

Dynamic Equations

, , x y θ

1 2 1 2, , , , MSGCMGF F Tα α

X

θ

F

CMGT

Y1F

α

2 Fα

T

x1

2

y

( ) ( )( ) ( )

( ) ( )

1 1 2 2

1 1 2 2

1 1 1 2 2 2

cos cos

sin sin

sin sinCMG

X F F

Y F F

T F d F d

α θ α θ

α θ α θ

θ α α

= − + + +

= − + + +

= − −

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2nd-generation simulator: Preliminary experiment

0 5 10 15 20 25 30 35-20

0

20

40

60

80

100

t (seconds)

Θ (d

egre

es)

0 5 10 15 20 25 30 35-6

-4

-2

0

2

4

6

8

10

12

t (seconds)

Ω (d

egre

es/s

econ

d)

0 5 10 15 20 25 30 35-40

-20

0

20

40

60

80

100

t (seconds)

Θgi

mba

l (deg

) | Ω

gim

bal (d

eg/s

)

Gimbal PositionGimbal Rate

0 5 10 15 20 25 30 35-0.05

-0.04

-0.03

-0.02

-0.01

0

0.01

0.02

0.03

0.04

0.05

t (seconds)

T MSG

CM

G (Nm

)

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A ProxOps Simulation facility and two kinds of Robotic Spacecraft Simulators have been developedExperiments of autonomous tracking and docking maneuvers were performed The research has a critical educational valueFuture development: multi-spacecraft assembly & reconfiguration

For more information:

Conclusions

M.Romano, D.A. Friedman, T.J. Shay, Laboratory Experimentation of Autonomous Spacecraft Approach and Docking to a Collaborative Target. Accepted for publication. To Appear. AIAA Journal of Spacecraft and Rockets.

J. Hall, M. Romano, A Novel Robotic Spacecraft Simulator with Mini-Control Moment Gyroscopes and Rotating Thrusters. Submitted toe IEEE AIM 2007.

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MS and Doctoral StudentsSponsors: AFRL, NPS-RO

Acknowledgment