System and method for guiding heading of a mobile robotic device

• US 10,386,847 B1
• Filed: 01/19/2017
• Issued: 08/20/2019
• Est. Priority Date: 02/19/2016
• Status: Active Grant

• Current Assignee: Ai Incorprated
• Original Assignee: Ai Incorprated
• Inventors: Ebrahimi Afrouzi, Ali
• Primary Examiner(s): Sample, Jonathan L
• Application Number:
  US15/410,624
• Time in Patent Office: 943 Days
• Field of Search: 700245-264, 31856812, 31856816, 3185682, 901 1, 901 9, 901 46, 901 47
• CPC Class Codes: B25J 5/007 mounted on wheels
• CPC Class Codes: G01S 17/46 Indirect determination of position data
• CPC Class Codes: G05D 1/0234 using optical markers or beacons optical beacons per se G01S1/70
• CPC Class Codes: G05D 1/0246 using a video camera in combination with image processing means
• CPC Class Codes: G05D 1/0248 in combination with a laser lasers per se H01S
• CPC Class Codes: Y10S 901/01 Mobile robot

Abstract

The present invention introduces a method for guiding or directing the heading of a mobile robotic device. A light pattern is projected from a light emitting unit disposed on a robotic device. The angle of the plane of the projection of the light pattern with respect to a heading of the robotic device is preset, but may be any angle as desired by a manufacturer or operator. A camera positioned in a plane parallel to the plane of the light pattern projection captures images of the projected light pattern on surfaces substantially opposite the light emitting unit. Images are processed to check for reflection symmetry about a vertical centerline of the images. Upon detecting an image that does not have reflection symmetry, the robotic device turns to adjust its heading with relation to the surfaces in the environment on which the light pattern is projected. Turning amounts and directions are provided to the controller and may be based on analysis of the last image captured.

Claims

1. A method for maintaining or correcting a heading of a robotic device relative to surfaces in a work environment comprising:

in a first step, projecting a light pattern from a light emitting unit positioned on a robotic device in a plane with a preset relationship to a heading of the robotic device onto surfaces substantially opposite the light emitting unit;

in a second step, capturing an image of the projected light pattern by a camera positioned on the robotic device in a plane parallel to the plane of the light emitting unit;

in a third step, processing the image with a processor provided on the robotic device to virtually divide the image in half vertically and determine whether the image has reflection symmetry about a vertical centerline; and

in a fourth step, if the image does not have reflection symmetry, adjusting the heading of the robotic device and repeating the first through fourth steps until such a time as a captured image is determined to have reflection symmetry.

2. The method of claim 1 wherein the light emitting unit and camera are provided on a housing rotatable with respect to a main body of the robotic device.

3. The method of claim 1 wherein reflection symmetry in images is analyzed by counting a number of columns of pixels found between a centerline of the image and a first column of pixels containing at least one pixel illuminated by the projected light pattern in both leftward and rightward directions from the centerline.

4. The method of claim 1 wherein a turning angle is calculated using the formula:

[F(A)−

F(B)]*g(x)∝

turning angle

where F(A) is a function of the distance from a centerline of the image to a first pixel lighted by the light projection in left direction,

F(B) is a function of the distance from a centerline of the image to a first pixel lighted by the light projection in a right direction,

x is a multidimension array containing one or more parameters of the position of the light projection and the camera in relation to each other, and,

g(x) is a transform function of x,

whereby a positive result corresponds with a clockwise turning direction and a negative result corresponds with a counterclockwise turning direction.

5. The method of claim 1 further comprising:

in a fifth step, identifying a position of a first point of the projected pattern by a first set of coordinates;

in a sixth step, identifying a position of a second point of the projected pattern by a second set of coordinates;

in a seventh step, calculating an amount of asymmetry between the first point and the second point with relation to a centerline of the image by comparing the first and second sets of coordinates;

in an eighth step, acquiring a rotation amount corresponding to the calculated asymmetry amount from a reference table of rotation amounts saved in a memory unit of the robotic device, each rotation amount in the table corresponding to an asymmetry amount and aimed at adjusting the heading of the robotic with respect to opposing surfaces according to a preset desired heading;

in a ninth step, rotating the robotic device the rotation amount corresponding to the calculated asymmetry amount in the table;

in a tenth step, repeating the fifth through seventh steps to find a second asymmetry amount;

in an eleventh step, if the absolute value of the second asymmetry amount is greater than a predetermined threshold, adjusting the reference table rotation figures by a function of the absolute value of the second asymmetry amount; and

iteratively repeating the fifth through eleventh steps at predetermined intervals and continuing to adjust the reference table throughout work.

6. A heading-correcting robotic device comprising:

a chassis including a set of wheels;

a motor to drive the wheels;

a battery to provide power to the robotic device;

a controller in communication with the motor and wheels, the controller including a processor operable to control the motor and wheels to steer movement of the robotic device;

a light emitting unit for projecting a predetermined light pattern onto surfaces substantially opposite the light emitting unit;

a camera for capturing images of the projected light pattern; and

an image processor for processing the captured images to determine whether they have reflection symmetry;

wherein, upon detecting that an image has less than a threshold amount of reflection symmetry, the robotic device adjusts its heading by turning in a left or right direction.

7. The heading-correcting robotic device of claim 6 wherein the turning angle is calculated using the formula:

[F(A)−

F(B)]*g(x)∝

turning angle

where F(A) is a function of the distance from a centerline of an image to a first pixel lighted by the light projection in left direction;

F(B) is a function of the distance from a centerline of the image to a first pixel lighted by the light projection in a right direction;

x is a multidimension array containing one or more parameters of the position of the light projection and the camera in relation to each other; and

g(x) is a transform function of x;

whereby a positive result corresponds with a rightward turning direction and a negative result corresponds with a leftward turning direction.

8. The heading-correcting robotic device of claim 6 wherein the light emitting unit and camera are provided on a housing rotatable with respect to the chassis of the robotic device.

9. The heading-correcting robotic device of claim 6 wherein reflection symmetry in images is assessed by counting a number of columns of pixels found between a centerline of an image and a first column of pixels that is illuminated by the projected light pattern in both left and right directions from the centerline.

10. The heading-correcting robotic device of claim 6 wherein reflection symmetry in images is assessed by:

identifying a position of a first point of the projected pattern by a first set of coordinates;

identifying a position of a second point of the projected pattern by a second set of coordinates; and

calculating an amount of asymmetry between the first point and the second point with relation to a centerline of the image by comparing the first and second sets of coordinates;

and a turning direction and degree for adjusting the heading is determined by;

consulting a reference table saved in a memory unit of the robotic device, the reference table comprised of asymmetry amounts and corresponding rotation amounts, each rotation amount in the table aimed at correcting the heading of the robotic device with respect to opposing surfaces according to a preset desired heading.

11. The heading-correcting robotic device of claim 10 wherein the robotic device is further configured to:

repeat the process for assessing reflection symmetry to find a second asymmetry amount; and

,

if the absolute value of the second asymmetry amount is greater than a predetermined threshold, adjust the reference table rotation amounts by a function of the absolute value of the second asymmetry amount.

12. A method for maintaining or correcting a heading of a robotic device relative to a surface in a work environment comprising:

projecting a light pattern from a light emitting unit disposed on a robotic device, the light pattern being projected in a plane with a preset relationship to a heading of the robotic device onto surfaces substantially opposite the light emitting unit;

capturing an image of the projected light pattern by a camera disposed on the robotic device in a plane parallel to the plane of the light emitting unit;

processing the image with a processor disposed on the robotic device to determine whether the image has reflection symmetry about a vertical centerline of the image; and

if the image has less than a threshold amount of reflection symmetry, adjusting the heading of the robotic device and repeating the process until such a time as a captured image is determined to have at least the threshold amount of reflection symmetry.

13. The method of claim 12 wherein the light emitting unit and camera are provided on a housing rotatable with respect to a main body of the robotic device.

14. The method of claim 12 wherein reflection symmetry in images is analyzed by counting a number of columns of pixels found between a centerline of the image and a first column of pixels that contains at least one pixel illuminated by the projected light pattern in both leftward and rightward directions from the centerline.

15. The method of claim 12 wherein a turning angle for adjusting the heading of the robotic device is calculated using the formula:

[F(A)−

F(B)]*g(x)∝

turning angle

where F(A) is a function of the distance from a centerline of the image to a first pixel lighted by the light projection in left direction,

F(B) is a function of the distance from a centerline of the image to a first pixel lighted by the light projection in a right direction,

x is a multidimension array containing one or more parameters of the position of the light projection and the camera in relation to each other, and,

g(x) is a transform function of x,

whereby a positive result corresponds with a clockwise turning direction and a negative result corresponds with a counterclockwise turning direction.

16. The method of claim 12 further comprising:

identifying a position of a first point of the projected pattern by a first set of coordinates;

identifying a position of a second point of the projected pattern by a second set of coordinates;

calculating an amount of asymmetry between the first point and the second point with relation to a centerline of the image by comparing the first and second sets of coordinates;

acquiring a rotation amount corresponding to the calculated asymmetry amount from a reference table of rotation amounts saved in a memory unit of the robotic device, each rotation amount in the table corresponding to an asymmetry amount and aimed at adjusting the heading of the robotic with respect to opposing surfaces according to a preset desired heading;

rotating the robotic device the rotation amount corresponding to the calculated asymmetry amount in the table;

repeating the steps to find a second asymmetry amount;

if the absolute value of the second asymmetry amount is greater than a predetermined threshold, adjusting the reference table rotation figures by a function of the absolute value of the second asymmetry amount; and

iteratively repeating this process at predetermined intervals and continuing to adjust the reference table throughout work.