Creation of a map of the surroundings
A map of the surroundings for a motorized domestic appliance is created by transmitting signals and allocating reflections to points. A local distribution of the points is formed. Points are discarded if a correspondence of the distribution to a straight line fails to reach a predefined degree. In a second variant, points whose distance from an average location exceeds a predefined value are discarded. The surroundings may be divided into tiles. A normal distribution transformation for the points of a tile specifies an average location and a variance of the points. The variance has two eigenvectors in two dimensions, each with an eigenvalue describing the variance contained in the eigenvector. A ratio between the larger and smaller eigenvalues describes an equal or unequal distribution of the variances. If, however, the quotient is, say, 10 or more, a large number of points of the tile can lie along a straight line.
1 . A method for creating a map of the surroundings for a mobile household appliance, the method comprising:
transmitting a measurement signal into the surroundings of the household appliance and receiving reflections of the measurement signal;
determining points in the surroundings that are allocated a reflection of the measurement signal;
determining a spatial distribution of the points in the surroundings;
dividing the surroundings into tiles of a predetermined size;
identifying points with a distance to an average location of the points exceeds a predetermined value;
identifying points of a tile of the tiles with a spatial distribution of the points of the tile corresponds less than a predetermined amount to a straight line;
checking whether all the points of a whole tile have been identified and discarding the points of a whole tile, subsequently discarding individually identified points, and retaining remaining points; or discarding individually identified points, and subsequently checking whether all the points of a whole tile have been identified and discarding the points of a whole tile, and retaining remaining points;
creating the map of the surroundings on a basis of the remaining points; and
storing the map of the surroundings in a storage device in the mobile household appliance, and the map being configured to inform a navigation of the mobile household appliance in the surroundings.
2 . The method according to claim 1 , which comprises determining a normal distribution transformation NDT for the points of a tile, the normal distribution transformation indicating an average location of the points and a variance of the points.
3 . The method according to claim 1 , which comprises:
determining each of the points in two dimensions;
with a variance of the points of a tile including two eigenvectors;
determining eigenvalues of the eigenvectors; and
discarding the points of a tile for which a ratio between a larger eigenvalue and a smaller eigenvalue deviates from one by more than a predetermined amount.
4 . The method according to claim 1 , which comprises:
determining each of the points in two dimensions;
with a variance of the points of a tile including two eigenvectors;
determining eigenvalues of the eigenvectors; and
discarding the points of a tile if one of the eigenvalues exceeds a predetermined value or undershoots a predetermined value.
5 . The method according to claim 1 , which comprises:
dividing the surroundings into tiles of a predetermined size; and
discarding a point that is allocated to a tile if a distance of the point to an average location of the points of the tile exceeds the predetermined value.
6 . The method according to claim 5 , which comprises determining a normal distribution transformation NDT for the points of a tile, the normal distribution transformation NDT indicating an average location of the points and a variance of the points.
7 . The method according to claim 6 , which comprises:
determining each of the points in two dimensions;
the variance of the points of a tile including two eigenvectors;
determining eigenvalues of the eigenvectors; and
discarding the points of a tile for which a ratio between a larger eigenvalue and a smaller eigenvalue deviates from one by more than a predetermined amount.
8 . The method according to claim 6 , which comprises:
determining each of the points in two dimensions;
the variance of the points of a tile including two eigenvectors;
determining eigenvalues of the eigenvectors; and
discarding the points of a tile if one of the eigenvalues exceeds a predetermined value or undershoots a predetermined value.
9 . The method according to claim 6 , which comprises determining the distance of a point by determining a Mahalanobis distance of the point to the average location of the points.
10 . An apparatus for determining a map of the surroundings for a mobile household appliance, the apparatus comprising:
a transmitter for transmitting a measurement signal into the surroundings of the household appliance;
a receiver for receiving reflections of the measurement signal; and
a processor connected to said receiver, said processor being configured to:
determine points in the surroundings which are allocated a reflection of the measurement signal;
determine a spatial distribution of the points in the surroundings;
divide the surroundings into tiles of a predetermined size;
identify points with a distance to an average location of the points exceeds a predetermined value;
identify points of a tile of the tiles with a spatial distribution of the points of the tile corresponds less than a predetermined amount to a straight line;
check whether all the points of a whole tile have been identified and discarding the points of a whole tile, and subsequently discarding individually identified points, and retaining remaining points; or discarding individually identified points, and subsequently checking whether all the points of a whole tile have been identified and discarding the points of a whole tile, and retaining remaining points; and
determine the map of the surroundings on a basis of the remaining points, the map being configured to inform a navigation of the mobile household appliance in the surroundings; and
a storage device for storing the map of the surroundings in a storage device in the mobile household appliance.
11 . The apparatus according to claim 10 , which comprises a LiDAR sensor forming said transmitter and said receiver.
12 . A floor cleaning robot, comprising the apparatus according to claim 10 for determining a map of the surroundings of the floor cleaning robot.