Systems and methods for ground plane estimation

• US 9,804,600 B1
• Filed: 01/06/2016
• Issued: 10/31/2017
• Est. Priority Date: 07/24/2014
• Status: Active Grant

• Current Assignee: Boston Dynamics, Inc. (SoftBank Group Corp.)
• Original Assignee: Google Inc. (Alphabet Inc.)
• Inventors: Blankespoor, Kevin, Nelson, Gabriel, Neville, Neil
• Primary Examiner(s): Trivedi, Atul
• Application Number:
  US14/988,913
• Time in Patent Office: 664 Days
• Field of Search: 701 26
• CPC Class Codes: B25J 9/0006 Exoskeletons, i.e. resembling a human figure
• CPC Class Codes: B25J 9/1615 characterised by special kind of manipulator, e.g. planar, scara, gantry, cantilever, space, closed chain, passive/active joints and tendon driven manipulators
• CPC Class Codes: B25J 9/1694 characterised by use of sensors other than normal servo-feedback from position, speed or acceleration sensors, perception control, multi-sensor controlled systems, sensor fusion
• CPC Class Codes: B25J 9/1697 Vision controlled systems
• CPC Class Codes: B62D 57/032 with alternately or sequentially lifted supporting base and legs; with alternately or sequentially lifted feet or skid B62D57/024 takes precedence
• CPC Class Codes: G05D 1/0088 characterized by the autonomous decision making process, e.g. artificial intelligence, predefined behaviours using knowledge based models G06N5/00
• CPC Class Codes: G05D 1/0891 specially adapted for land vehicles
• CPC Class Codes: G05D 1/228 Command input arrangements located on-board unmanned vehicles
• CPC Class Codes: G05D 1/69 Coordinated control of the position or course of two or more vehicles
• CPC Class Codes: Y10S 901/01 Mobile robot

Abstract

Example systems and methods for estimating a ground plane are provided. An example method may include determining an orientation of a body of a robotic device with respect to a gravity aligned reference frame. The method may also include determining the location of one or more contact points between the robotic device and a ground surface. The method may also include determining a ground plane estimation of the ground surface based on the determined orientation of the robotic device with respect to the gravity aligned reference frame and the determined locations of the one or more contact points. The method may also include determining a distance between the body of the robotic device and the determined ground plane estimation. The method may also include providing instructions to adjust a position and/or orientation of the robotic device based on the determined distance and the determined ground plane estimation.

Claims

1. A method operable by a computing device, the method comprising:

determining an orientation of a body of a robotic device with respect to a gravity aligned reference frame;

determining a location of one or more contact points between the robotic device and a ground surface;

determining, by one or more processors of the computing device, a ground plane estimation of the ground surface based on the determined orientation of the robotic device with respect to the gravity aligned reference frame and the determined locations of the one or more contact points between the robotic device and the ground surface, wherein the ground plane estimation includes an approximation of a shape of the ground surface,

determining a distance between the body of the robotic device and the determined ground plane estimation; and

providing instructions, by the one or more processors, to adjust a position of the robotic device based on the determined distance and the determined ground plane estimation.

2. The method of claim 1, wherein the robotic device includes an inertial measurement unit (IMU) including an accelerometer and a gyroscope, and wherein the IMU outputs data for determining the orientation of the robotic device with respect to the gravity aligned reference frame.

3. The method of claim 1, wherein the location of one or more contact points between the robotic device and the ground surface are determined based on one or more sensors positioned on one or more legs of the robotic device.

4. The method of claim 3, wherein providing instructions to adjust the position of the robotic device based on the determined ground plane estimation comprises providing instructions to position the one or more legs of the robotic device such that a center of mass of the robotic device is located within a polygon defined by the one or more legs of the robotic device.

5. The method of claim 1, wherein the location of one or more contact points between the robotic device and the ground surface are determined based on one or more sensors positioned on one or more feet of the robotic device.

6. The method of claim 5, wherein providing instructions to adjust the position of the robotic device based on the determined distance and the determined ground plane estimation comprises providing instructions to swing one or more feet of the robotic device substantially parallel to the determined ground plane estimation to provide consistent ground clearance.

7. The method of claim 1, wherein providing instructions to adjust the position of the robotic device based on the determined distance and the determined ground plane estimation comprises providing instructions to orient one or more features of the body of the robotic device substantially parallel to the determined ground plane estimation, or at some orientation relative to the determined ground plane.

8. The method of claim 1, further comprising:

determining one or more virtual contact points in the vicinity of the robotic device, wherein the one or more virtual contact points represent an estimation of a future, current, or past contact point based on a current position and a current velocity of the robotic device, wherein the virtual contact points are determined via a non-contact sensor system, and wherein the determined ground plane estimation of the ground surface is further based on the determined one or more virtual contact points.

9. The method of claim 8, wherein the non-contact sensor system comprises a vision system.

10. The method of claim 8, wherein the non-contact sensor system comprises a laser range finder.

11. The method of claim 1, wherein two contact points are determined between the robotic device and the ground surface, and wherein determining the ground plane estimation of the ground surface comprises:

determining a normal vector of a previously determined ground plane estimation; and

projecting the normal vector of the previously determined ground plane estimation to be perpendicular to a line connecting the two contact points, such that the projected normal vector is perpendicular to the determined ground plane estimation.

12. The method of claim 1, wherein three contact points are determined between the robotic device and the ground surface, and wherein determining the ground plane estimation of the ground surface comprises:

determining a plane including the three contact points.

13. The method of claim 1, wherein four or more contact points are determined between the robotic device and the ground surface, and wherein determining the ground plane estimation of the ground surface comprises:

determining a ground plane that minimizes the square distance between the four or more contact points and the determined ground plane.

14. The method of claim 1, wherein determining a distance between the body of the robotic device and the determined ground plane estimation comprises:

determining a first distance between the body of the robotic device and a first point on the determined ground plane estimation;

determining a second distance between the body of the robotic device and a second point on the determined ground plane estimation; and

averaging the first distance and the second distance.

15. The method of claim 1, further comprising:

determining an orientation difference between the body of the robotic device and the determined ground plane estimation; and

providing instructions, by the one or more processors, to adjust the position of the robotic device based on the determined distance, the determined orientation difference, and the determined ground plane estimation.

16. A robotic device including:

a body;

two or more legs extending from the body;

at least one processor; and

non-transitory data storage comprising program logic executable by the at least one processor to cause the robotic device to perform functions comprising;

determining an orientation of the body of the robotic device with respect a gravity aligned reference frame;

determining a location of one or more contact points between the robotic device and a ground surface;

determining a ground plane estimation of the ground surface based on the determined orientation of the robotic device with respect to the gravity aligned reference frame and the determined locations of the one or more contact points between the robotic device and the ground surface, wherein the ground plane estimation includes an approximation of a shape of the ground surface;

determining a distance between the body of the robotic device and the determined ground plane estimation; and

providing instructions to adjust a position of the robotic device based on the determined distance and the determined ground plane estimation.

17. The robotic device of claim 16, wherein the robotic device includes an inertial measurement unit (IMU) including an accelerometer and a gyroscope, and wherein the IMU outputs data for determining the orientation of the robotic device with respect to the gravity aligned reference frame.

18. The robotic device of claim 16, wherein the one or more contact points between the robotic device and the ground surface comprise a location of one or more sensors positioned on two or more legs of the robotic device.

19. The robotic device of claim 16, further comprising two or more feet coupled to the two or more legs, wherein the one or more contact points between the robotic device and the ground surface, the position of which are determined by one or more sensors on the robotic device.

20. A non-transitory computer-readable storage medium having stored thereon instructions, that when executed by a computing device, cause the computing device to carry out functions comprising:

determining an orientation of a body of a robotic device with respect to a gravity aligned reference frame;

determining a location of one or more contact points between the robotic device and a ground surface;

determining a ground plane estimation of the ground surface based on the determined orientation of the robotic device with respect to the gravity aligned reference frame and the determined locations of the one or more contact points between the robotic device and the ground surface, wherein the ground plane estimation includes an approximation of a shape of the ground surface;

determining a distance between the body of the robotic device and the determined ground plane estimation, and

providing instructions to adjust a position of the robotic device based on the determined distance and the determined ground plane estimation.

21. The non-transitory computer-readable storage medium of claim 20, wherein the functions further comprise:

determining one or more virtual contact points in the vicinity of the robotic device, wherein the one or more virtual contact points represent an estimation of a future, current, or past contact point based on a current position and a current velocity of the robotic device, wherein the virtual contact points are determined via a non-contact sensor system, and wherein the ground plane estimation of the ground surface is further based on the determined one or more virtual contact points.

22. The non-transitory computer-readable storage medium of claim 20, wherein providing instructions to adjust the position of the robotic device based on the determined distance and the determined ground plane estimation comprises providing instructions to position a bottom surface of the body of the robotic device substantially parallel to the determined ground plane estimation.