topological path planning jbnu, division of computer science and engineering parallel computing lab...

Topological Path Planning

JBNU, Division of Computer Science and EngineeringParallel Computing Lab

Jonghwi Kim

Introduction to AI Robots

Chapter 9

Chapter Objectives

• Define the difference between a natural and artificial landmark and give one example of each

• Given a description of an indoor office environment and a set of behaviors, build a relational graph representation labeling the distinctive places and local control strategies using gateways

• Describe in one or two sentences : gateway, image signature, visual homing, viewframe, orientation region

• Given a figure showing landmarks, create a topological map showing landmarks, landmark pair boundaries, and orientation regions

Contents

•Overview• Landmarks and Gateways•Relational Methods•Associative Methods•Case Study of Topological

Navigation with a Hybrid Architecture

•Summary

Overview

Route representations fall into one of two approaches :

•Relational most popular giving the robot an abbreviated, “connect the dots”

graph-style of spatial memory use an explicit representation, support path planning focus on the graph-like representation of spatial

memory

•Associative better for retracing known paths focus on coupling sensing with localization

Landmarks and Gateways

•Landmark one or more perceptually distinctive features of

interest on an object or locale of interest not necessarily a single can be a grouping of objects

McDonald’s stand of aspen trees


•Landmark be either artificial or natural “artificial” and “natural” ≠ “man-made” and

“organic”

• artificial landmark set of features added to an existing object or locale in

order to either support recognition of the landmark or some other perceptual activity


•Landmark• natural landmark

configuration of existing features selected for recognition which were not expressly designed for the perceptual activity


•Landmark must satisfy three criteria

Be readily recognizable Support the task dependent activity Be perceivable from many different viewpoints

• good landmark’s characteristics passive in order to be available despite a power

failure should be perceivable over the entire range where

the robot might need to see it should have distinctive features, and, if possible,

unique feature


•Gateway an opportunity for a robot to change its overall

direction of navigation critical for localization, path planning, and map

making

Relational Methods

•Relational methods represent the world as a graph or network of nodes

and edges

• Nodes gateways, landmarks, or goals

• Edges a navigable path between two nodes can attach additional information

– direction(N,S,E,W), approximate distance, terrain type, the behaviors needed to navigate that path

Relational Methods

• Earliest relational graphs for navigation(Smith and Cheeseman)

Relational Methods

• Relational graphs for navigation(Kuipers and Byun)

Relational Methods

•Distinctive places landmark that the robot could detect from a nearby

region called a neighborhood

Associative Methods

•Associative methods create a behavior which converts sensor

observations into the direction to go to reach a particular landmark

• assumption perceptual stability : that views of the location that are close together

should look similar perceptual distinguishability : that views far away should look different

Associative Methods

•Visual homing work done by Nelson, and later by Engelson• image signature

• created by partitioning an image into sections• possible measurement

• edge density• dominant edge orientation• average intensity• so on…

Associative Methods

•Visual homing

Associative Methods

•QualNav(qualitative navigation) the ideas from Levitt and Lawton for outdoor navigation over large

distances as part of the Defense Advance Research Projects Agency (DARPA) Autonomous Land Vehicle (ALV) project in the late 1980’s

Associative Methods

•QualNav(qualitative navigation)

Case Study of Topological Navigation with a Hybrid Architecture

Case study of topological navigation using the SFX architecture in 1994 AAAI Mobile Robot Competition by a team of undergraduates form the Colorado School of Mines


placed in a random room navigate out of the room and to

another room within 15 minutes be given a topological map

How the topological map was entered the activities of Cartographer

How scripts were used to simplify behavioral management, and the lessons learned


• Path planning a sample topological map

start nodes direction blockages landmark


• Path planning Cartographer

input : a gateway type, start node, goal node output : a list of nodes representing the best path

preprocessing reclassifying (a hall to door connection as Hd) eliminates extraneous gateways

Task Manager select the appropriate abstract navigation

behaviord


• Path planning


• Navigation scripts used to specify and carry out the implied details of the

plan

navigate-door ANB


navigate-hall ANB


navigate-foyer ANB


• Lessons learned critical to build the abstract navigation behaviors

out of robust primitives (biggest problem is quality of the primitive

behaviors)contention for sensing resourcemetric distance problem impact of obstacles

Summary

• Landmarks simplify the ‘Where am I?’ problem

• Gateways special landmarks which reflect a potencial for the robot to

change directions

• navigation methods relational

distinctive places(nodes), local control strategies(lcs)

associative viewframe

topological path planning jbnu, division of computer science and engineering parallel computing lab...

Documents

path slide

gateways landmark

cheeseman slide

localization slide

byun slide

neighborhood slide

perceptual activity

unique feature slide