METHOD AND APPARATUS FOR SIMULTANEOUS LOCALIZATION AND MAPPING OF MOBILE ROBOT ENVIRONMENT

• US 20140058610A1
• Filed: 10/30/2013
• Published: 02/27/2014
• Est. Priority Date: 08/31/2009
• Status: Active Grant

• Current Assignee: Vorwerk & Company Interholding Gesellschaft Mit Beschrã¤Nkter Haftung (Vorwerk & Company KG)
• Original Assignee: Neato Robotics, Inc. (Vorwerk & Company KG)
• Inventors: SOFMAN, Boris, ERMAKOV, Vladimir, EMMERICH, Mark, ALEXANDER, Steven, MONSON, Nathaniel David
• Granted Patent: US 8,903,589 B2
• Time in Patent Office: Days
• US Class Current: 701/23
• CPC Class Codes: B25J 11/0085 Cleaning
• CPC Class Codes: B25J 9/0003 Home robots, i.e. small robots for domestic use
• CPC Class Codes: B25J 9/1602 characterised by the control system, structure, architecture
• CPC Class Codes: G05D 1/024 in combination with a laser lasers per se H01S
• CPC Class Codes: G05D 1/0274 using mapping information stored in a memory device navigation using map-matching G01C21/30
• CPC Class Codes: Y10S 901/01 Mobile robot
• CPC Class Codes: Y10S 901/47 Optical

Abstract

Techniques that optimize performance of simultaneous localization and mapping (SLAM) processes for mobile devices, typically a mobile robot. In one embodiment, erroneous particles are introduced to the particle filtering process of localization. Monitoring the weights of the erroneous particles relative to the particles maintained for SLAM provides a verification that the robot is localized and detection that it is no longer localized. In another embodiment, cell-based grid mapping of a mobile robot'"'"'s environment also monitors cells for changes in their probability of occupancy. Cells with a changing occupancy probability are marked as dynamic and updating of such cells to the map is suspended or modified until their individual occupancy probabilities have stabilized. In another embodiment, mapping is suspended when it is determined that the device is acquiring data regarding its physical environment in such a way that use of the data for mapping will incorporate distortions into the map, as for example when the robotic device is tilted.

Claims

1. A system for identifying and marking dynamic areas of a map of a physical environment of a mobile device, the system comprising:

a. a data acquisition system that generates data identifying the mobile device'"'"'s physical environment; and

b. a processing apparatus, responsive to the data acquisition system, to map or model the mobile device'"'"'s physical environment and the data acquisition system'"'"'s location within the mobile device'"'"'s physical environment in a cell-based grid in which cells are assigned probabilities indicating certainty about whether the physical space corresponding to a cell is occupied by an object or contains empty space;

c. wherein the processing apparatus includes apparatus that;

i. assigns and updates probabilities to each cell within the grid map from the data generated by the data acquisition system;

ii. determines if changes in a cell'"'"'s probability of occupancy indicate that a cell currently identified as empty has become occupied or a cell currently identified as occupied has become empty; and

iii. marks such cells so as not to be updated with regard to their probability of containing an obstacle or not while said probability is changing.

2. A system as claimed in claim 1 wherein the marked cells also include a zone, of predetermined size, surrounding the marked cells.

3. A system claimed in claim 1 wherein the mobile device is a robot, the system further comprising a distance-measuring device, said distance-measuring device comprising light-emitting and light-receiving apparatus to emit light to measure distance based on reflected light, said data acquisition system being responsive to said distance-measuring device to generate said data identifying the mobile device'"'"'s physical environment.

4. A system as claimed in claim 3 wherein the distance-measuring device comprises a laser rangefinder.

6. A system as claimed in claim 1 wherein the apparatus that marks cells includes apparatus to suspend updates of those cells in the cell-based grid map until individual occupancy probabilities of those cells have stabilized.

7. A system as claimed in claim 1 wherein the processing apparatus further includes apparatus that monitors sudden changes in consecutive cells to determine whether a tilt event has occurred.

8. A system as claimed in claim 7 wherein the processing apparatus further includes apparatus to compare a physical length represented by consecutive cells and a predefined threshold to determine whether the tilt event has occurred.

5. A method for controlling movement of a robot, the method comprising:

a. generating data identifying the robot'"'"'s physical environment; and

b. mapping or modeling the robot'"'"'s physical environment and location within the robot'"'"'s physical environment in a cell-based grid in which cells are assigned probabilities indicating certainty about whether the physical space corresponding to a cell is occupied by an object or contains empty space;

c. assigning and updating probabilities to each cell within the grid map from the generated data;

d. determining whether changes in a cell'"'"'s probability of occupancy indicate that a cell currently identified as empty has become occupied or a cell currently identified as occupied has become empty;

e. marking such cells so as not to be updated with regard to their probability of containing an obstacle or not while said probability is changing.; and

f. controlling movement of the robot in accordance with (a) to (c).

9. A method as claimed in claim 5, wherein said marking includes suspending updating of such cells until individual occupancy probabilities of those cells have stabilized.

10. A method as claimed in claim 5 further comprising monitoring sudden changes in consecutive cells to determine whether a tilt event has occurred.

11. A method as claimed in claim 10 further comprising comparing a physical length represented by consecutive cells and a predefined threshold to determine whether the tilt event has occurred.