Mitigating sensor noise in legged robots

• US 9,789,919 B1
• Filed: 03/22/2016
• Issued: 10/17/2017
• Est. Priority Date: 03/22/2016
• Status: Active Grant

• Current Assignee: Boston Dynamics, Inc. (SoftBank Group Corp.)
• Original Assignee: Google Inc. (Alphabet Inc.)
• Inventors: Blankespoor, Kevin, da Silva, Marco
• Primary Examiner(s): Holloway, Jason
• Application Number:
  US15/077,870
• Time in Patent Office: 574 Days
• CPC Class Codes: B25J 9/1633 compliant, force, torque control, e.g. combined with position control
• CPC Class Codes: B62D 57/02 with ground-engaging propulsion means, e.g. walking members
• 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: G01L 5/0028 Force sensors associated with force applying means G01L5/0052, G01L5/0057, G01L5/0061 take precedence
• CPC Class Codes: G05B 2219/41005 Update servo gain not for each microprocessor cycle, but after a certain displacement
• CPC Class Codes: G05B 2219/41006 Change gain as function of speed and position
• CPC Class Codes: G05B 2219/41021 Variable gain
• CPC Class Codes: G05B 2219/41025 Detect oscillation, unstability of servo and change gain to stabilize again
• CPC Class Codes: G05B 2219/41163 Adapt gain to friction, weight, inertia
• CPC Class Codes: Y10S 901/01 Mobile robot

Abstract

An example implementation involves receiving measurements from an inertial sensor coupled to the robot and detecting an occurrence of a foot of the legged robot making contact with a surface. The implementation also involves reducing a gain value of an amplifier from a nominal value to a reduced value upon detecting the occurrence. The amplifier receives the measurements from the inertial sensor and provides a modulated output based on the gain value. The implementation further involves increasing the gain value from the reduced value to the nominal value over a predetermined duration of time after detecting the occurrence. The gain value is increased according to a profile indicative of a manner in which to increase the gain value of the predetermined duration of time. The implementation also involves controlling at least one actuator of the legged robot based on the modulated output during the predetermined duration of time.

Claims

1. A method comprising:

detecting, by a control system of a legged robot, an occurrence of a foot of the legged robot making contact with a surface, wherein the control system is configured to receive, as a control input, measurements from an inertial sensor coupled to the legged robot, and wherein a given measurement includes a vibration component representative of vibrations caused by the foot of the legged robot making contact with the surface;

upon detecting the occurrence, reducing a gain value of an amplifier of the control system from a nominal value to a reduced value, wherein the amplifier receives the measurements from the inertial sensor and provides a modulated output based on the gain value;

over a predetermined duration of time after detecting the occurrence, increasing the gain value from the reduced value to the nominal value, wherein the gain value is increased according to a profile indicative of a manner in which to increase the gain value over the predetermined duration of time; and

during the predetermined duration of time, controlling at least one actuator of the legged robot based on the modulated output.

2. The method of claim 1, further comprising:

obtaining data indicative of a plurality of measurements from the inertial sensor coupled to the robot, wherein the plurality of measurements includes a corresponding plurality of vibration components, wherein each vibration component has a duration;

determining an average vibration duration based on the durations of the plurality of vibration components; and

determining the profile based on the average vibration duration.

3. The method of claim 2, wherein determining the profile comprises:

providing a set of profile gain values associated with a set of time offsets, wherein a first profile gain value in the set of profile gain values corresponds to a first time offset in the set of time offsets, wherein a second profile gain value in the set of profile gain values corresponds to a second time offset in the set of time offsets, and wherein the second time offset occurs after the first time offset;

assigning the first profile gain value as the reduced value;

assigning the second profile gain value as the nominal value;

assigning each profile gain value associated with respective time offsets between the first time offset and the second time offset a gain value that is between the reduced value and the nominal value; and

determining the profile as a relation defined by the set of profile gain values and the set of time offsets.

4. The method of claim 1, further comprising:

obtaining data indicative of a measurement from an inertial sensor coupled to the robot, wherein the measurement includes a vibration component comprising a set of data values;

determining a vibration attenuation relationship based on an interpolation of the data values of the plurality of vibration components; and

determining the profile based on the vibration attenuation relationship.

5. The method of claim 1, wherein increasing the gain value according to the profile causes the gain value to increase linearly from the reduced level to the nominal level over the period of time.

6. The method of claim 1, wherein increasing the gain value according to the profile causes the gain value to increase exponentially from the reduced level to the nominal level over the period of time.

7. The method of claim 1, further comprising filtering the measurements from the inertial sensor before providing them as the control input to the control system.

8. The method of claim 1, wherein the legged robot is communicatively coupled to a network, and wherein the method further comprises obtaining the profile from a computing device connected to the network.

9. The method of claim 1, further comprising:

determining an amount of force applied by the foot against the surface; and

based on the amount of force, selecting the profile as a particular profile from among a set of predetermined profiles each associated with respective ranges of force.

10. The method of claim 1, wherein increasing the gain value according to the profile causes the amplifier to reduce a magnitude of the vibration component.

11. A non-transitory computer-readable medium having instructions stored thereon that, upon execution by at least one processor, causes a control system of a legged robot to perform operations comprising:

detecting, by the control system of a legged robot, an occurrence of a foot of the legged robot making contact with a surface, wherein the control system is configured to receive, as a control input, measurements from an inertial sensor coupled to the legged robot, and wherein a given measurement includes a vibration component representative of vibrations caused by the foot of the legged robot making contact with the surface;

upon detecting the occurrence, reducing a gain value of an amplifier of the control system from a nominal value to a reduced value, wherein the amplifier receives the measurements from the inertial sensor and provides a modulated output based on the gain value;

over a predetermined duration of time after detecting the occurrence, increasing the gain value from the reduced value to the nominal value, wherein the gain value is increased according to a profile indicative of a manner in which to increase the gain value over the predetermined duration of time; and

during the predetermined duration of time, controlling at least one actuator of the legged robot based on the modulated output.

12. The non-transitory computer readable medium of claim 11, wherein the operations further comprise:

obtaining data indicative of a plurality of measurements from the inertial sensor coupled to the robot, wherein the plurality of measurements includes a corresponding plurality of vibration components, wherein each vibration component has a duration;

determining an average vibration duration based on the durations of the plurality of vibration components; and

determining the profile based on the average vibration duration.

13. The non-transitory computer readable medium of claim 12, wherein the operations further comprise:

providing a set of profile gain values associated with a set of time offsets, wherein a first profile gain value in the set of profile gain values corresponds to a first time offset in the set of time offsets, wherein a second profile gain value in the set of profile gain values corresponds to a second time offset in the set of time offsets, and wherein the second time offset occurs after the first time offset;

assigning the first profile gain value as the reduced value;

assigning the second profile gain value as the nominal value;

assigning each profile gain value associated with respective time offsets between the first time offset and the second time offset a gain value that is between the reduced value and the nominal value; and

determining the profile as a relation defined by the set of profile gain values and the set of time offsets.

14. The non-transitory computer readable medium of claim 11, wherein the operations further comprise:

obtaining data indicative of a measurement from an inertial sensor coupled to the robot, wherein the measurement includes a vibration component comprising a set of data values;

determining a vibration attenuation relationship based on an interpolation of the data values of the plurality of vibration components; and

determining the profile based on the vibration attenuation relationship.

15. A robot comprising:

at least one robotic leg comprising a foot;

at least one actuator;

an inertial sensor coupled to a portion of the legged robot; and

a control system configured to perform operations comprising;

receiving, as a control input, measurements from the inertial sensor, wherein a given measurement includes a vibration component representative of vibrations caused by the foot making contact with the surface;

detecting an occurrence of a foot of the legged robot making contact with a surface;

upon detecting the occurrence, reducing a gain value of an amplifier of the control system from a nominal value to a reduced value, wherein the amplifier receives the measurements from the inertial sensor and provides a modulated output based on the gain value; and

over a predetermined duration of time after detecting the occurrence, increasing the gain value from the reduced value to the nominal value, wherein the gain value is increased according to a profile indicative of a manner in which to increase the gain value over the predetermined duration of time; and

during the predetermined duration of time, controlling the at least one actuator based on the modulated output.

16. The robot of claim 15, wherein the operations further comprise:

obtaining data indicative of a plurality of measurements from the inertial sensor coupled to the robot, wherein the plurality of measurements includes a corresponding plurality of vibration components, wherein each vibration component has a duration;

determining an average vibration duration based on the durations of the plurality of vibration components; and

determining the profile based on the average vibration duration.

17. The robot of claim 16, wherein the operations further comprise:

providing a set of profile gain values associated with a set of time offsets, wherein a first profile gain value in the set of profile gain values corresponds to a first time offset in the set of time offsets, wherein a second profile gain value in the set of profile gain values corresponds to a second time offset in the set of time offsets, and wherein the second time offset occurs after the first time offset;

assigning the first profile gain value as the reduced value;

assigning the second profile gain value as the nominal value;

assigning each profile gain value associated with respective time offsets between the first time offset and the second time offset a gain value that is between the reduced value and the nominal value; and

determining the profile as a relation defined by the set of profile gain values and the set of time offsets.

18. The robot of claim 15, wherein the operations further comprise:

obtaining data indicative of a measurement from an inertial sensor coupled to the robot, wherein the measurement includes a vibration component comprising a set of data values;

determining a vibration attenuation relationship based on an interpolation of the data values of the plurality of vibration components; and

determining the profile based on the vibration attenuation relationship.

19. The robot of claim 15, further comprising a network interface configured to connect to a network, and wherein the method further comprises obtaining the profile from a computing device connected to the network.

20. The robot of claim 15, wherein the operations further comprise:

determining an amount of force applied by the foot against the surface; and

based on the amount of force, selecting the profile as a particular profile from among a set of predetermined profiles each associated with respective ranges of force.