Ground plane compensation for legged robots

Patent metadata

Field	Value
Publication number	US-9908240-B1
Application number	US-201615386830-A
Country	US
Kind code	B1
Filing date	Dec 21, 2016
Priority date	May 15, 2015
Publication date	Mar 6, 2018
Grant date	Mar 6, 2018

Abstract

An example implementation includes (i) receiving sensor data that indicates topographical features of an environment in which a robotic device is operating, (ii) determining, for a particular topographical feature of the environment in a direction of travel of the robotic device, a height of the particular topographical feature and a distance between the robotic device and the particular topographical feature, (iii) estimating a ground plane extending from the robotic device in the direction of travel toward the particular topographical feature, the ground plane fitting to the determined distance and height, (iv) determining a grade of the estimated ground plane, and (v) directing the robotic device to adjust pitch in proportion to the determined grade.

First claim

We claim:

1. A control system of a robot comprising:
a processor in communication with at least one sensor; and
a non-transitory computer readable medium in communication with the processor, the non-transitory computer readable medium storing program instructions that when executed on the processor cause the processor to perform operations comprising:
determining, using sensor data obtained from the at least one sensor, a height of a particular topographical feature in a direction of travel of the robot and a distance between the robot and the particular topographical feature;
estimating a plane extending from the robot in the direction of travel toward the particular topographical feature, the estimated plane having a slope based on the height of the particular topographical feature and the distance between the robot and the particular topographical feature;
determining whether the slope of the estimated plane comprises a positive slope or a negative slope; and
when the slope of the estimated plane comprises the positive slope, controlling actuators of the robot to cause the robot to pitch a torso of the robot in the direction of travel of the robot.

2. The control system of claim 1 , wherein the operations further comprise controlling the actuators of the robot to cause the robot to pitch the torso to match the slope of the estimated plane.

3. The control system of claim 1 , wherein the robot is a biped.

4. The control system of claim 1 , wherein the operations further comprise, when the slope of the estimated plane comprises the negative slope, controlling the actuators of the robot to cause the robot to pitch the torso away from the direction of travel.

5. The control system of claim 1 , wherein the operations further comprise controlling the actuators of the robot to cause the robot to pitch the torso by a degree that is a portion of a grade of the estimated plane.

6. The control system of claim 1 , wherein the robot has a leg, and wherein the operations further comprise:
for a step of the leg, determining a smooth spline swing trajectory in which the leg is lifted upward in a direction that is opposite of gravity, stepped forward in a direction that is parallel to a grade of the estimated ground plane, and lowered downward in the direction of gravity; and
controlling the actuators of the robot to cause the robot to move the leg based on the determined swing trajectory.

7. The control system of claim 1 , wherein the operations further comprise controlling the actuators of the robot to cause the robot to adjust a pitch of the torso approximately one stride in advance of the particular topographical feature.

8. The control system of claim 1 , wherein the operations further comprise controlling the actuators of the robot to cause the robot to adjust a pitch of the torso between one and two strides in advance of the particular topographical feature.

9. The control system of claim 1 , wherein the robot has legs, and wherein the operations further comprise:
detecting, using the sensor data from the at least one sensor, a topographical feature in the direction of travel that forms ground roll;
determining a magnitude of the ground roll formed by the topographical feature;
controlling the actuators of the robot to cause the robot to reduce its height in proportion to the determined magnitude of the ground roll by bending one or more respective joints of the legs; and
while the robot is traversing the detected topographical feature, controlling the actuators of the robot to cause the robot to conduct a gait with the legs while maintaining the reduced height.

10. The control system of claim 1 , wherein the robot has legs, and wherein the operations further comprise controlling the actuators of the robot to cause the robot to reduce its height in proportion to a grade of the estimated plane by bending one or more respective joints of the legs.

11. The control system of claim 1 , wherein the operations further comprise:
determining that a difference between a grade of the estimated plane and a grade of a currently traversed ground plane exceeds a threshold difference in grade; and
controlling the actuators of the robot to cause the robot to reduce speed in advance of the particular topographical feature.

12. A robot comprising:
a sensor;
actuators; and
a control system configured to:
determine, using sensor data obtained from the sensor, a height of a particular topographical feature in a direction of travel of the robot and a distance between the robot and the particular topographical feature;
estimate a plane extending from the robot in the direction of travel toward the particular topographical feature, the estimated plane having a slope based on the height of the particular topographical feature and the distance between the robot and the particular topographical feature;
determine whether the slope of the estimated plane comprises a positive slope or a negative slope; and
when the slope of the estimated plane comprises the positive slope, control the actuators to cause the robot to pitch a torso of the robot in the direction of travel of the robot.

13. The robot of claim 12 , wherein the control system is further configured to control the actuators to cause the robot to pitch the torso to match the slope of the estimated plane.

14. The robot of claim 12 , further comprising two legs.

15. The robot of claim 12 , wherein the control system is further configured to control the actuators to cause the robot to pitch the torso away from the direction of travel when the slope of the estimated plane comprises the negative slope.

16. A method comprising:
determining, using sensor data obtained from at least one sensor of a robot, a height of a particular topographical feature in a direction of travel of the robot and a distance between the robot and the particular topographical feature;
estimating a plane extending from the robot in the direction of travel toward the particular topographical feature, the estimated plane having a slope based on the height of the particular topographical feature and the distance between the robot and the particular topographical feature;
determining whether the slope of the estimated plane comprises a positive slope or a negative slope; and
when the slope of the estimated plane comprises the positive slope, controlling actuators of the robot to cause the robot to pitch a torso of the robot in the direction of travel of the robot.

17. The method of claim 16 , further comprising controlling the actuators of the robot to cause the robot to pitch the torso to match the slope of the estimated plane.

18. The method of claim 16 , wherein the robot is a biped.

19. The method of claim 16 , further comprising, when the slope of the estimated plane comprises the negative slope, controlling the actuators to cause the robot to pitch the torso away from the direction of travel.

20. The method of claim 16 , further comprising controlling the actuators of the robot to cause the robot to pitch the torso by a degree that is a portion of a grade of the estimated plane.

Assignees

• Google Inc
• Boston Dynamics Inc

Inventors

• Da Silva Marco
• Blankespoor Kevin
• Nelson Gabriel

Classifications

• B25J5/00 Primary

  Manipulators mounted on wheels or on carriages (B25J1/00 takes precedence; programme-controlled manipulators B25J9/00 {; vehicle aspects B60, B62, e.g. remote-controlled steering for motor vehicles B62D1/24; control of position of vehicles G05D1/00}) · CPC title

• B25J9/1664

  characterised by motion, path, trajectory planning · CPC title

• B25J9/1694 Primary

  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 title

• G01C9/00

  Measuring inclination, e.g. by clinometers, by levels · CPC title

• Y10S901/01

  Mobile robot · CPC title