Initial Proposal Presentation - Senior Design - University of ...

courageouscellistΤεχνίτη Νοημοσύνη και Ρομποτική

29 Οκτ 2013 (πριν από 3 χρόνια και 7 μήνες)

71 εμφανίσεις

Conventional Localization


Localization is any method used in determining
an
object’s position.



Conventional localization is
implemented through
Global
Position System
(GPS) technology.


How GPS works


Commercial GPS works by having satellites send out
electromagnetic signals with a center frequency of
1575.42
Mhz

to a receiver whose position is unknown.



Electromagnetic waves work in air because the
conductivity of air is very low. Air has a conductivity
varying from 3
×
10
−15

to 8
×
10
−15
Siemens per meter at 20
C
°

so signal degradation is negligible
.

Why GPS isn’t applicable


Fresh water’s
conductivity ranges
from 1
×
10
−2

to 2
×
10

1

Siemens
per
meter.


Due to the higher
conductivity of water
electromagnetic
waves
quickly lose strength
so
they cannot propagate
long distances.

Acoustic signal testing site: Mansfield Hallow lake, CT

Acoustic Signal
Transmission



To circumvent the issues affiliated with
electromagnetic signals in conventional localization,
AUV localization uses acoustic signals instead.



Acoustic signals are advantageous because their signal
strength loss is not related to the conductivity of the
medium that they traverse.


Transducers generate
acoustic signals.

Acoustic
Signal
A
pplication


Commercial localization methods:


Long base line (LBL)


Short base line (SBL)


Ultra short base line (USBL)


GPS intelligent buoys (GIBS)



Research localization methods:


Synchronous localization


Asynchronous
localization

Node 1

Node 3

Node 4

Node 2

AUV

Acoustic signal

Sea Floor

Long Baseline
Schematic

AUV signal

Node response

AUV

Node 1

Node 2

Node 3

Node 4

Signal Time Diagram (LBL)

Time

Long Baseline Localization (LBL)


Advantages of LBL:


Very high Positioning accuracy and stability


Observation Redundancy


Disadvantages of LBL:


Complex system requiring expert operators


Large arrays of expensive equipment

AUV

Acoustic signal

Sea Floor

Short baseline Schematic

AUV signal

Transducer signal

A

B

C

Transducers

Boat



AUV

Transducer A

Transducer B

Transducer C

Pinger

Signal Time Diagram
(SBL)

Time

AUV

Transducer A

Transducer B

Transducer C

Signal Time Diagram (SBL)

Time

Short Baseline Localization (SBL)


Advantages of
SBL:


Low
system
complexity


Ship
-
based
system (no transducers deployed on sea
floor)


Disadvantages
of
SBL:


Larger
baseline needed for accuracy in deep water
(>
30m)


Position
accuracy depends on additional
sensors


AUV

Acoustic signal

Sea Floor

Ultra Short Baseline Schematic

AUV signal

Transducer signal

B

Boat

A

C

Transducer Array

AUV

Transducer A

Transducer B

Transducer C

Signal Time Diagram (USBL)

Time

Ultra Short Baseline (USBL
)


Advantages of
USBL:


Low
system complexity makes USBL and easy tool to
use.


Ship
based system means no need to deploy a
transponder array on the
seafloor.


Disadvantages of USBL:


Position
accuracy may be greatly affected by slight
variations.


Calibration
of the receivers and AUV require that their
clocks be synchronized when using time of arrival
estimates

GPS Intelligence Buoys Schematic

Node 1

Node 3

Node 4

Node 2

AUV

Acoustic signal

Sea Floor

GPS

Surface
Vehicle

Synchronizes
Nodes

Radio signal

Signal Time Diagram (GIBs)

AUV

Node 1

Node 2

Node 3

Node 4

Time

GPS Intelligent Buoys (GIBs
)


Advantages of
GIBs:


No
calibration other than communication with the satellite is
needed


Easy
to deploy and
recover


Disadvantages
of
GIBs:


If
water is too deep, buoys could
drift


Their
position would have to be controlled
to
maintain
array

GPS

AUV
1

AUV
2

AUV
3

Node
1

Node
2

Node
3

Acoustic signal

Synchronous Localization

Schematic

AUV

Node 1

Node 2

Node 3

Node 4

Signal Time Diagram (sync)

Time

Synchronous Localization (sync)


Advantages of synchronous
localization:


Able
to service multiple AUV at
once


Does
not require continuous GPS signal to synchronize
surface
nodes


Disadvantages of synchronous
localization:


Nodes
must be on the surface initially to receive a
GPS
signal
initially.


Any
missed node signal means position can not be
computed if working with the minimum node
schematic.

Node 1

Node 3

Node 4

Node 2

AUV

Asynchronous Localization
Schematic

AUV initiator signal

Node response

AUV

Node 1

Node 2

Node 3

Node 4

Signal Time Diagram (
Asynch
)

Time

Asynchronous Localization


Advantages of Asynchronous
Localization:


Node
clocks do not require synchronization with each
other.


Extra
timing measurements sent from other nodes can
be factored into to calculations to provide better
position accuracy.


Disadvantages of Asynchronous
Localization:


The
initiator signal must send out a delay factor long
enough so no nodes send out signals at the same time.


Never
field tested so actually accuracy improvement is
unknown.


Objective


Design a highly accurate localization system capable of
being used on underwater vehicles.



Conduct joint testing with the AUV senior design
group to implement an effective localization
schematic.

Timeline of Events

January


Hardware
setup of
nodes.


Field testing
of
algorithms .

February


Field testing
of
algorithms.


Algorithm
comparison
analysis.

March


Field testing
of
algorithms.


Algorithm
comparison
analysis.

April


Integration
of
localization
with other
groups.


Algorithm
comparison
analysis.

May


Complete
integration
of
localization.

September



Project
Statement.


Localization
research.

October


Project
specifications.


Additional
localization
research


Coding DSP C

November


Coding DSP C


Finalize
implementation
plans.

December


Hardware setup
of nodes.


Coding DSP C
algorithms.

Questions?