mapping and localization for robots the occupancy grid approach
TRANSCRIPT
![Page 1: Mapping and Localization for Robots The Occupancy Grid Approach](https://reader035.vdocuments.mx/reader035/viewer/2022062518/56649e4c5503460f94b40c4f/html5/thumbnails/1.jpg)
Mapping and Localization for Robots
The Occupancy Grid Approach
![Page 2: Mapping and Localization for Robots The Occupancy Grid Approach](https://reader035.vdocuments.mx/reader035/viewer/2022062518/56649e4c5503460f94b40c4f/html5/thumbnails/2.jpg)
Agenda
Introduction Mapping
Occupancy grids Sonar Sensor Model Dynamically Expanding Occupancy Grids
Localization Iconic Feature-based Monte Carlo
![Page 3: Mapping and Localization for Robots The Occupancy Grid Approach](https://reader035.vdocuments.mx/reader035/viewer/2022062518/56649e4c5503460f94b40c4f/html5/thumbnails/3.jpg)
An intelligent robot is a mechanical creature which can function autonomously.
Intelligent – the robot does not do things in a mindless, repetitive way.
Function autonomously – the robot can operate in a self-contained manner, under reasonable conditions, without interference by a human operator.
![Page 4: Mapping and Localization for Robots The Occupancy Grid Approach](https://reader035.vdocuments.mx/reader035/viewer/2022062518/56649e4c5503460f94b40c4f/html5/thumbnails/4.jpg)
Robots in museums
![Page 5: Mapping and Localization for Robots The Occupancy Grid Approach](https://reader035.vdocuments.mx/reader035/viewer/2022062518/56649e4c5503460f94b40c4f/html5/thumbnails/5.jpg)
Personal Robots
![Page 6: Mapping and Localization for Robots The Occupancy Grid Approach](https://reader035.vdocuments.mx/reader035/viewer/2022062518/56649e4c5503460f94b40c4f/html5/thumbnails/6.jpg)
Robots in space
![Page 7: Mapping and Localization for Robots The Occupancy Grid Approach](https://reader035.vdocuments.mx/reader035/viewer/2022062518/56649e4c5503460f94b40c4f/html5/thumbnails/7.jpg)
The problem of Navigation
Where am I going? What’s the best way there? Where have I been? Where am I? How am I going to get there?
![Page 8: Mapping and Localization for Robots The Occupancy Grid Approach](https://reader035.vdocuments.mx/reader035/viewer/2022062518/56649e4c5503460f94b40c4f/html5/thumbnails/8.jpg)
Mapping
Topological Mapping Features and Landmarks Milestones with connections Hard to scale
Metric Mapping Geometric representations Occupancy Grids Larger maps much more computationally intensive
![Page 9: Mapping and Localization for Robots The Occupancy Grid Approach](https://reader035.vdocuments.mx/reader035/viewer/2022062518/56649e4c5503460f94b40c4f/html5/thumbnails/9.jpg)
Map Making
![Page 10: Mapping and Localization for Robots The Occupancy Grid Approach](https://reader035.vdocuments.mx/reader035/viewer/2022062518/56649e4c5503460f94b40c4f/html5/thumbnails/10.jpg)
Demo of Mapping
The Littlejohn Project http://www-2.cs.cmu.edu/afs/cs.cmu.edu/project/mercator/www
/
littlejohn/
![Page 11: Mapping and Localization for Robots The Occupancy Grid Approach](https://reader035.vdocuments.mx/reader035/viewer/2022062518/56649e4c5503460f94b40c4f/html5/thumbnails/11.jpg)
Occupancy Grids
A tool to construct an internal model of static environments based on sensor data.
The environment to be mapped is divided into regions.
Each grid cell is an element and represents an area of the environment.
![Page 12: Mapping and Localization for Robots The Occupancy Grid Approach](https://reader035.vdocuments.mx/reader035/viewer/2022062518/56649e4c5503460f94b40c4f/html5/thumbnails/12.jpg)
Representation of Occupancy Grids
![Page 13: Mapping and Localization for Robots The Occupancy Grid Approach](https://reader035.vdocuments.mx/reader035/viewer/2022062518/56649e4c5503460f94b40c4f/html5/thumbnails/13.jpg)
Sonar Sensor Model
![Page 14: Mapping and Localization for Robots The Occupancy Grid Approach](https://reader035.vdocuments.mx/reader035/viewer/2022062518/56649e4c5503460f94b40c4f/html5/thumbnails/14.jpg)
Methods of Sonar Reading
Probabilistic Methods: Bayesian Dempster-Shafer HIMM (Histogrammic In Motion Mapping)
![Page 15: Mapping and Localization for Robots The Occupancy Grid Approach](https://reader035.vdocuments.mx/reader035/viewer/2022062518/56649e4c5503460f94b40c4f/html5/thumbnails/15.jpg)
Why Probabilistic Mapping?
Noise in commands and sensors Commands are not executed exactly
(eg. Slippage leads to odometry errors) Sonars have several error issues
(eg. cross-talk, foreshortening, specular reflection)
![Page 16: Mapping and Localization for Robots The Occupancy Grid Approach](https://reader035.vdocuments.mx/reader035/viewer/2022062518/56649e4c5503460f94b40c4f/html5/thumbnails/16.jpg)
Occupancy Grids
Pros Simple Accurate
Cons Require fixed-size environment:
difficult to update if size of mapped area changes.
![Page 17: Mapping and Localization for Robots The Occupancy Grid Approach](https://reader035.vdocuments.mx/reader035/viewer/2022062518/56649e4c5503460f94b40c4f/html5/thumbnails/17.jpg)
Dynamically Expanding Occupancy Grids
Variable-sized maps Ability to increase size of map, if new areas
are added to the environment Start mapping at center of nine-block grid As robot explores, new cells are added Global map is stored outside the RAM in a
file or a database
![Page 18: Mapping and Localization for Robots The Occupancy Grid Approach](https://reader035.vdocuments.mx/reader035/viewer/2022062518/56649e4c5503460f94b40c4f/html5/thumbnails/18.jpg)
Representation of DEOGs
![Page 19: Mapping and Localization for Robots The Occupancy Grid Approach](https://reader035.vdocuments.mx/reader035/viewer/2022062518/56649e4c5503460f94b40c4f/html5/thumbnails/19.jpg)
Adding Cells to a DEOG
![Page 20: Mapping and Localization for Robots The Occupancy Grid Approach](https://reader035.vdocuments.mx/reader035/viewer/2022062518/56649e4c5503460f94b40c4f/html5/thumbnails/20.jpg)
![Page 21: Mapping and Localization for Robots The Occupancy Grid Approach](https://reader035.vdocuments.mx/reader035/viewer/2022062518/56649e4c5503460f94b40c4f/html5/thumbnails/21.jpg)
Dynamically Expanding Occupancy Grids
Best (the only?) solution for mapping changing environments.
Saves RAM Other useful information can be stored in the
map More complicated to program than regular
occupancy grids
![Page 22: Mapping and Localization for Robots The Occupancy Grid Approach](https://reader035.vdocuments.mx/reader035/viewer/2022062518/56649e4c5503460f94b40c4f/html5/thumbnails/22.jpg)
Localization
Where am I?
Methods: Iconic Feature-based Monte-Carlo
![Page 23: Mapping and Localization for Robots The Occupancy Grid Approach](https://reader035.vdocuments.mx/reader035/viewer/2022062518/56649e4c5503460f94b40c4f/html5/thumbnails/23.jpg)
Iconic Localization
Use raw sensor data Uses occupancy grids Current map is compared with original map.
If original map has errors, localization is very inaccurate.
Localization errors accumulate over time.
![Page 24: Mapping and Localization for Robots The Occupancy Grid Approach](https://reader035.vdocuments.mx/reader035/viewer/2022062518/56649e4c5503460f94b40c4f/html5/thumbnails/24.jpg)
The Concept
“pose”: (x, y, θ)location, orientation
Compare small local occupancy grid with stored global occupancy grid.
Best fit pose is correct pose.
![Page 25: Mapping and Localization for Robots The Occupancy Grid Approach](https://reader035.vdocuments.mx/reader035/viewer/2022062518/56649e4c5503460f94b40c4f/html5/thumbnails/25.jpg)
Feature-based Localization
Compares currently extracted features with features marked in a map.
Requires presence of easily extractable features in the environment.
If features are not easily distinguishable, may mistake one for the other.
![Page 26: Mapping and Localization for Robots The Occupancy Grid Approach](https://reader035.vdocuments.mx/reader035/viewer/2022062518/56649e4c5503460f94b40c4f/html5/thumbnails/26.jpg)
Monte Carlo Localization
Probabilistic 1. Start with a uniform distribution of possible poses (x, y,
) 2. Compute the probability of each pose given current
sensor data and a map 3. Normalize probabilities
Throw out low probability points Performance
Excellent in mapped environments Need non-symmetric geometries
![Page 27: Mapping and Localization for Robots The Occupancy Grid Approach](https://reader035.vdocuments.mx/reader035/viewer/2022062518/56649e4c5503460f94b40c4f/html5/thumbnails/27.jpg)
References:
Introduction to AI RoboticsDr. Robin Murphy
Dynamically Expanding Occupancy GridsBharani K. Ellore
Multi-agent mapping using dynamic allocation utilizing a storage systemLaura Barnes, Richard Garcia, Todd Quasny, Dr. Larry Pyeatt
Robotic Mapping: A surveySebastian Thrun
Littlejohn Projecthttp://www-2.cs.cmu.edu/afs/cs.cmu.edu/project/mercator/www/littlejohn/
CYE www.prorobotics.com The Honda Asimo http://asimo.honda.com Mars Rover http://marsrovers.jpl.nasa.gov/home/