Fuzzy-Based Inference System for Navigation and

Life Detection on Titan

Speaker: Steven ForbesUniversity of Arizona

Autonomy requirements

• Unconstrained, Science-Driven Planetary Reconnaissance requires higher level of on-board automation:

– Autonomous determination of sites with the highest probability of significant scientific findings and/or natural resources

• Solution: Fuzzy Expert System for Titan Hot-air Balloon autonomy

– Collects information at multiple (> 2) using multiple instruments mounted on a mobile, floating platform

– Synergistically connected to AGFA-like smart software– Performs synthesis of spatial and temporal information– Exhibits high degree of flexibility: can be tuned to

autonomously infer presence of life, and/or identify geological processes (e.g. fluvial processes, volcanism etc.)

Hot-Air Balloon for Titan Exploration

Fuzzy Altitude Controller

Pos/Vel LN N Z P LP

LN VL VL L L L

N VL VL L M M

Z VL L M H VH

P L M H H VH

LP H H H VH VH

Fuzzy PD + I

VerticalDynamics

Altitude

Velocity

DesiredVelocity

DesiredAltitude

IntegralControl

Fuzzy PD

Membership Functions

Knowledge-base:“IF delta-h is LP AND delta-V is Z THEN alpha is H”

(Mamdami-type)

0 20 40 60 80

0

0.2

0.4

0.6

0.8

1

alpha (degrees)

Deg

ree o

f m

em

bers

hip

VL M VHL H

-5000 0 5000

0

0.2

0.4

0.6

0.8

1

delta-Z (meters)

Deg

ree o

f m

em

bers

hip

LN N LPZ P

-8 -6 -4 -2 0 2 4 6 8

0

0.2

0.4

0.6

0.8

1

delta-Vz (m/sec)

Deg

ree o

f m

em

bers

hip

LN N LPZ P

U = Kα

Navigation through Fuzzy Logic

0 0.5 1 1.5 2 2.5 3

x 105

0

1000

2000

3000

4000

5000

6000

Horizontal Position (meters)

Ver

tica

l Po

siti

on

(m

eter

s)

Controller Balloon TrajectorySimulated Titan GroundFuzzy Planner Output

WInd DIrection (2 m/sec)

Fuzzy Expert System Architecture

Factors for Life Potential

• Polymaric similarity– Obtained through mass

spectrometry / gas chromatography

• Isotopic abundance– Analysis of C12/C13 ratio

• Chirality skew– Comparison of right handed

to left handed molecule abundance

Rule #Confidence

FactorPolymaric Similarity

Isotopic Abundance

Chirality Skew

Life Potential

1 1 H H H VH2 1 H H M VH3 1 H H L H4 1 H M H VH5 1 H M M H6 1 H M L H7 1 H L H H8 1 H L M M9 1 H L L L10 1 M H H VH11 1 M H M M12 1 M H L M13 1 M M H M14 1 M M M M15 1 M M L L16 1 M L H M17 1 M L M L18 1 M L L VL19 1 L H H H20 1 L H M M21 1 L H L L22 1 L M H L23 1 L M M L24 1 L M L VL25 1 L L H L26 1 L L M VL27 1 L L L VL

Fuzzy Planner: GNC System

WindSpeed

W

Sensors

In1Out1

Hot-air BalloonDynamics

In1 Out1

Fuzzy PlannerFuzzy Logic

Altitude Controller

Fuzzy Expert System

Filter/Estimator

In1Out1

DesiredVelocity

Vd

Actuator(Top Valve)

In1 Out1

AltitudeVertical VelocityGas temperatureHorizontal Position

DFG

SI

DesiredAltitude Valve

Angle

KnowledgeAcquisition

InferenceEngine

ExplanationDatabase

KnowledgeBase

SpaceborneControl System

Expert System Architecture

Planetary Geologist(Expert)

4

14331

1

31

14

21

3313

11

22111

2

21

,

)(

,1

21

aing

aa

g

wind

a

gg

pgg

amtot

Datota

XTXSXXq

XpM

RXmXV

XFX

uXXT

XgmXXq

cmX

XVXCm

XXACXmXVXgX

XX

Preprocessing/Categorization

Fuzzy Expert Architecture

Guidance System

Conclusions and Future Work

• Using fuzzy logic based inference systems is a viable approach to overcome autonomous challenges on future probes

• A fuzzy system capable of controlling the dynamics of hot-air balloons for the autonomous exploration of Titan has been shown

• The system is modular and flexible. It can be modified to incorporate multidisciplinary knowledge

• Further incorporation and testing of potential life detection needs to be carried out

• Future efforts will include more extensive tests of the fuzzy controller on more realistic models