Autonomous construction of maps

by miniature robotsPaul FitzpatrickColin Flanagan

Move right

Move leftCorner feature

Edgefeature

Robot’s path traces the outline of the

boundary

To follow a boundary :- Move forward

continuously Turn left if boundary

gets further away Turn right if boundary

gets closer

Landmark angle

Landmarkposition

Landmarkposition

Location of corners used to correct robot’s position estimate

Angle between pairs of corners allow corrections to direction estimate

Corner Landmarks

Robot turns more sharply than the curve itself, giving a well-defined landmark.

Concave corner Convex corner

Robot cannot turn an arc with a radius less than the robot itself.

Correction suggested by apparent direction of the edge

d Correction suggested

by apparent edge position

Straight-Edge Landmarks

d

Wall

First pass

Second pass

Path of robotRecent marker

“Marker” representation scheme

Updating markers

Replaced markerPath of Robot

Older markerRecent marker

Replaced markerPath of Robot

Older markerRecent marker

Map = collection of markers

NearNeighbourhoo

d

ImmediateNeighbourhoo

d

LocalNeighbourhoo

d

Markers

Current position of robot

Neighbourhoods

DistantNeighbourhoo

d

In each cycle of the sorting process, one marker from each neighbourhood is examined and moved to another neighbourhood if appropriate.

Immediate

Near Local Distant

Index to marker currently being sortedIndex of next marker to be sorted

Robot caught in cyclic behaviour

Cyclic behaviour

Robot shown trapped by an awkwardly shaped obstacle.

Familiar region expands until escape is possible

Use of familiarity

Robot uses “familiarity” sensor to escape from trap.

Inspiration- background search succeeds

Use of background search

Use of familiarity can be combined with conventional search

A B

Markers placed successively as robot moves can be assumed reachable from each other

Path of robot

ConnectivityMarkers not laid successively cannot be assumed to be reachable from each other, even if they are close

Path of robot

A B

Markers close to each other can be deduced to be connected if a short path between them can be found through other connected markers

D C D

Deducing connectivity

Least reachable

Most reachableDirection of spread

Updating connectivity

Goal 1

1

1

222

2

233

33

33

4

Using connectivity

Autonomous construction of maps

by miniature robotsPaul FitzpatrickColin Flanagan

Effect of not using landmarks

Effect of using landmarks

Conclusions

Maps can be built by an autonomous robot even under very constrained conditions:

Without long-range sensors such as sonar or visionWith limited processing powerWith limited memory

Maps can be suitable for use by “behaviour-based” robots

No shared representation necessaryDon’t require extensive, time-extended computation

Correction suggested by apparent direction of the edge

d Correction suggested

by apparent edge position

Straight-Edge Landmarks

d

Wall

First pass

Second pass