Method, system and apparatus for support structure detection

• US 10,731,970 B2
• Filed: 12/13/2018
• Issued: 08/04/2020
• Est. Priority Date: 12/13/2018
• Status: Active Grant

• Current Assignee: Zebra Technologies Corporation
• Original Assignee: Zebra Technologies Corporation
• Inventors: Cao, Feng, Singh, Harsoveet
• Primary Examiner(s): Ahmed, Jamil
• Application Number:
  US16/219,679
• Publication Number:
  US 20200191559A1
• Time in Patent Office: 600 Days
• CPC Class Codes: G01B 11/22 for measuring depth
• CPC Class Codes: G01B 11/245 using a plurality of fixed, simultaneously operating transducers G01B11/2408 - G01B11/2425, G01B11/255 take precedence
• CPC Class Codes: G01B 11/254 Projection of a pattern, viewing through a pattern, e.g. moiré
• CPC Class Codes: G01S 17/89 for mapping or imaging
• CPC Class Codes: G01S 17/894 3D imaging with simultaneous measurement of time-of-flight at a 2D array of receiver pixels, e.g. time-of-flight cameras or flash lidar
• CPC Class Codes: G01S 7/4802 using analysis of echo signal for target characterisation; Target signature; Target cross-section
• CPC Class Codes: G06T 2207/10028 Range image; Depth image; 3D point clouds
• CPC Class Codes: G06T 7/12 Edge-based segmentation
• CPC Class Codes: G06T 7/521 from laser ranging, e.g. using interferometry; from the projection of structured light
• CPC Class Codes: G06V 10/145 Illumination specially adapted for pattern recognition, e.g. using gratings
• CPC Class Codes: G06V 20/10 Terrestrial scenes scenes under surveillance with static cameras G06V20/52; scenes perceived from the exterior of a vehicle G06V20/56; scenes perceived from the interior of a vehicle G06V20/59
• CPC Class Codes: G06V 20/56 exterior to a vehicle by using sensors mounted on the vehicle

Abstract

A method of detecting a support structure in a navigational controller includes: controlling a depth sensor to capture a plurality of depth measurements corresponding to an area containing the support structure on a ground plane; generating, for each of the depth measurements, a projected depth measurement on the ground plane; selecting a boundary set of the projected depth measurements defining a boundary of the projection; selecting, based on angles between adjacent pairs of the boundary set of projected depth measurements, a subset of the projected depth measurements; generating a region of interest based on the subset of the projected depth measurements; retrieving a candidate subset of the depth measurements corresponding to the projected depth measurements in the region of interest; and generating a support structure plane definition based on the candidate subset of depth measurements.

Claims

1. A method of detecting a support structure in a navigational controller, the method comprising:

controlling a depth sensor to capture a plurality of depth measurements corresponding to an area containing the support structure on a ground plane;

generating, for each of the depth measurements, a projected depth measurement on the ground plane;

selecting a boundary set of the projected depth measurements defining a boundary of the projection;

selecting, based on angles between adjacent pairs of the boundary set of projected depth measurements, a subset of the projected depth measurements;

generating a region of interest based on the subset of the projected depth measurements;

retrieving a candidate subset of the depth measurements corresponding to the projected depth measurements in the region of interest; and

generating a support structure plane definition based on the candidate subset of depth measurements.

2. The method of claim 1, further comprising:

prior to generating the projection, selecting a primary subset of the depth measurements based on proximity to the mobile automation apparatus.

3. The method of claim 1, wherein selecting the subset of the projected depth measurements includes:

determining an angle for each of a plurality of adjacent pairs of the projected depth measurements; and

when the angle deviates from a straight angle beyond a threshold, discarding the adjacent pairs of projected depth measurements.

4. The method of claim 1, wherein generating the region of interest comprises fitting a line to the subset of the projected depth measurements.

5. The method of claim 1, wherein generating the support structure plane includes:

executing first and second plane generation operations to generate first and second candidate plane definitions; and

generating the support structure plane based on the first and second candidate plane definitions.

6. The method of claim 5, wherein generating the support structure plane based on the first and second candidate plane definitions comprises:

determining whether an attribute of each the first and second candidate plane definitions differs by an amount greater than a threshold; and

responsive to an affirmative determination, discarding at least one of the first and second candidate plane definitions.

7. The method of claim 5, wherein generating the support structure plane based on the first and second candidate plane definitions comprises generating an average of the first and second candidate plane definitions.

8. The method of claim 5, further comprising:

prior to generating the support structure plane, validating each of the first and second candidate plane definitions.

9. The method of claim 8, wherein validating each of the first and second candidate plane definitions comprises determining whether each of the first and second candidate plane definitions is substantially vertical.

10. The method of claim 5, wherein generating the second candidate plane definition comprises:

selecting a further subset of the depth measurements from the candidate subset; and

generating the second candidate plane definition based on the further subset.

11. A mobile automation apparatus, comprising:

a depth sensor; and

a navigational controller connected to the depth sensor, the navigational controller configured to;

control the depth sensor to capture a plurality of depth measurements corresponding to an area containing the support structure on a ground plane;

generate, for each of the depth measurements, a projected depth measurement on the ground plane;

select a boundary set of the projected depth measurements defining a boundary of the projection;

select, based on angles between adjacent pairs of the boundary set of projected depth measurements, a subset of the projected depth measurements;

generate a region of interest based on the subset of the projected depth measurements;

retrieve a candidate subset of the depth measurements corresponding to the projected depth measurements in the region of interest; and

generate a support structure plane definition based on the candidate subset of depth measurements.

12. The mobile automation apparatus of claim 11, wherein the navigational controller is further configured, prior to generation of the projection, to select a primary subset of the depth measurements based on proximity to the mobile automation apparatus.

13. The mobile automation apparatus of claim 11, wherein the navigational controller is configured, to select the subset of the projected depth measurements, to:

determine an angle for each of a plurality of adjacent pairs of the projected depth measurements; and

when the angle deviates from a straight angle beyond a threshold, discard the adjacent pairs of projected depth measurements.

14. The mobile automation apparatus of claim 11, wherein the navigational controller is configured, to generate the region of interest, to fit a line to the subset of the projected depth measurements.

15. The mobile automation apparatus of claim 11, wherein the navigational controller is configured, to generate the support structure plane, to:

execute first and second plane generation operations to generate first and second candidate plane definitions; and

generate the support structure plane based on the first and second candidate plane definitions.

16. The mobile automation apparatus of claim 15, wherein the navigational controller is configured, to generate the support structure plane based on the first and second candidate plane definitions, to:

determine whether an attribute of each the first and second candidate plane definitions differs by an amount greater than a threshold; and

responsive to an affirmative determination, discard at least one of the first and second candidate plane definitions.

17. The mobile automation apparatus of claim 15, wherein the navigational controller is configured, to generate the support structure plane based on the first and second candidate plane definitions, to generate an average of the first and second candidate plane definitions.

18. The mobile automation apparatus of claim 15, wherein the navigational controller is further configured, prior to generation of the support structure plane, to validate each of the first and second candidate plane definitions.

19. The mobile automation apparatus of claim 18, wherein the navigational controller is configured, to validate each of the first and second candidate plane definitions, to determine whether each of the first and second candidate plane definitions is substantially vertical.

20. The mobile automation apparatus of claim 15, wherein the navigational controller is configured, to generate the second candidate plane definition, to:

select a further subset of the depth measurements from the candidate subset; and

generate the second candidate plane definition based on the further subset.