Robot localisation

1 Robot localisation (UG and PG)

Robot localization is the process of determining where a mobile robot is located con- cerning its environment. Robot localization provides an answer to the question: Where is the robot now? A reliable solution to the localization is one of the most fundamental competencies required by an autonomous robot as the knowledge of the robot’s own location is an essential precursor to making decisions about future actions.

In a typical robot localization scenario, a map of the environment is available and the robot is equipped with sensors that observe the environment as well as monitor its own motion. The localization problem then becomes one of estimating the robot’s position within the map using information gathered from these sensors. The following shows an example of a 2D map drawn using ASCII characters:

0000X0000X

XX00X0XX0X

X000X0XX00

00X000X000

The character ‘X’ denotes an obstacle (the path cannot be traversed), while the character ‘0’ (Zero) represents a traversable positions. Any position within the map is indicated by the coordinates (k, j), where k is the row number (ordered top to bottom) and j is the column number (ordered left to right), starting from 1. For example, the top left position is (1, 1) and the bottom right is (4, 10).

A robot moves in the map and gathers information along the way. In this version, the robot has a single non-deterministic Move action and its sensors reports perfectly whether or not obstacles lay immediately to the north, south, east, and west. A sequence of sensor readings observed is the set of possible blocked directions. The following shows the example of the observed sensor readings at each time step; which means e.g., at time 1, the north (N), south (S) and west (W) of the robot have obstables: