Devices and methods for encoder calibration

Patent metadata

Field	Value
Publication number	US-9427872-B1
Application number	US-201414578446-A
Country	US
Kind code	B1
Filing date	Dec 21, 2014
Priority date	Dec 21, 2014
Publication date	Aug 30, 2016
Grant date	Aug 30, 2016

Abstract

A device is provided that comprises a hardware segment and an actuator to adjust a position of the segment within a range of positions. The device also comprises an encoder to rotate about an encoder axis responsive to the actuator adjusting the position. The device also comprises data storage that includes a dataset indicating offset angles between a reference configuration and a plurality of configurations of the encoder. The device also comprises a controller to cause the actuator to adjust the position to an end of the range of positions, responsively identify a range of encoder positions of the encoder that corresponds to the range of positions of the segment, modify the dataset such that the reference configuration corresponds to an end of the range of encoder positions, and determine a mapping between the offset angles indicated by the modified dataset and the range of positions of the hardware segment.

First claim

What is claimed is:

1. A device comprising:
a hardware segment;
an actuator to adjust a position of the hardware segment within a range of positions;
an encoder to rotate about an encoder axis responsive to the actuator adjusting the position of the hardware segment, wherein the encoder includes a plurality of deformations separated by given offset angles;
data storage that includes a dataset indicating offset angles between a reference configuration and a plurality of configurations of the encoder, wherein the offset angles indicated in the dataset relate to the given offset angles between the plurality of deformations, and wherein the reference configuration is indicative of the encoder being at a given encoder position about the encoder axis; and
a controller to cause the actuator to adjust the position of the hardware segment to an end of the range of positions, and to:
responsively identify a range of encoder positions that corresponds to the range of positions of the hardware segment;
modify the dataset such that the reference configuration is indicative of the encoder being at an end of the range of encoder positions; and
determine a mapping between the offset angles indicated by the modified dataset and the range of positions of the hardware segment.

2. The device of claim 1 , wherein the encoder is coupled, at a given orientation of the encoder, to the hardware segment, and wherein the range of encoder positions are associated with the range of positions of the hardware segment based on the given orientation of the encoder.

3. The device of claim 1 , wherein the controller:
detects at least two index signals and corresponding encoder positions from the encoder responsive to the adjustment of the position of the hardware segment, wherein a given index signal is indicative of the encoder having a given configuration of the plurality of configurations indicated in the dataset;
identifies at least one offset angle indicated by the dataset that is associated with one or more of the at least two index signals; and
associates the range of encoder positions with the plurality of configurations of the encoder based on the identified at least one offset angle and the detected corresponding encoder positions, wherein the controller determines the mapping based on the association.

4. The device of claim 1 , wherein the controller causes the actuator to adjust the position of the hardware segment to a given position within the range of positions based on the mapping.

5. The device of claim 1 , wherein the controller:
receives an input indicative of the hardware segment being at a home position within the range of positions;
responsively identifies a given encoder position that corresponds to the hardware segment being at the home position; and
modifies the mapping such that the offset angles are represented by positive values for first positions of the hardware segment in a first direction relative to the home position, negative values for second positions of the hardware segment in a second direction relative to the home position, and a value of zero for the home position of the hardware segment.

6. The device of claim 5 , wherein the controller:
receives a request to adjust the position of the hardware segment to a particular position relative to the home position; and
causes the actuator to adjust the position of the hardware segment to the particular position based on the modified mapping.

7. The device of claim 1 , wherein the encoder comprises:
a first disk that includes another plurality of deformations, wherein the encoder provides a given encoder value based on detection of a corresponding deformation of the other plurality of deformations; and
a second disk coupled to the first disk, wherein the second disk includes the plurality of deformations separated by the given offset angles, and wherein the encoder provides an index signal in response to detection of a deformation of the plurality of deformations.

8. The device of claim 1 , further comprising:
a camera to provide an image of the hardware segment, wherein the data storage includes a stored image of the hardware segment associated with the hardware segment being at the end of the range of positions, and wherein the controller detects that the hardware segment is at the end of the range of positions based on a comparison between the image and the stored image.

9. The device of claim 1 , further comprising:
a mechanical feature positioned at the end of the range of positions of the hardware segment, wherein the controller detects that the hardware segment is at the end of the range of positions based on detection of the mechanical feature.

10. The device of claim 1 , further comprising:
an inclinometer to provide data indicative of the position of the hardware segment, wherein the controller causes the actuator to adjust the position of the hardware segment based on the data from the inclinometer.

11. The device of claim 1 , wherein the controller:
causes the actuator to adjust the position of the hardware segment to another end of the range of positions; and
identifies the range of encoder positions responsive also to the adjustment of the position of the hardware segment to the other end of the range of positions.

12. A method comprising:
adjusting, by a robotic device that includes one or more processors, a position of a hardware segment of the robotic device to an end of a range of positions of the hardware segment;
responsively identifying a range of encoder positions about an encoder axis of an encoder of the robotic device that corresponds to the range of positions of the hardware segment, wherein the encoder rotates about the encoder axis responsive to adjustment of the position of the hardware segment, and wherein the encoder includes a plurality of deformations separated by given offset angles;
modifying a dataset indicating offset angles between a reference configuration and a plurality of configurations of the encoder such that the reference configuration corresponds to an encoder position outside the range of encoder positions, wherein the offset angles indicated in the dataset relate to the given offset angles between the plurality of deformations; and
determining a mapping between the offset angles indicated by the modified dataset and the range of positions of the hardware segment.

13. The method of claim 12 , further comprising:
detecting at least two index signals and corresponding encoder positions from the encoder responsive to the adjustment of the position, wherein a given index signal is indicative of the encoder having a given configuration of the plurality of configurations indicated in the dataset;
identifying at least one offset angle indicated in the dataset that is associated with one or more of the at least two index signals; and
associating the range of encoder positions with the plurality of configurations of the encoder based on the identified at least one offset angle and the detected corresponding encoder positions, wherein determining the mapping is based on the association.

14. The method of claim 12 , further comprising:
receiving an input indicative of the hardware segment being at a home position within the range of positions;
responsively identifying a given encoder position that corresponds to the hardware segment being at the home position; and
modifying the mapping such that the offset angles are represented by positive values for first positions of the hardware segment in a first direction relative to the home position, negative values for second positions of the hardware segment in a sec

Assignees

• Google Inc

Inventors

• Bingham Jeffrey Thomas
• Wilson Rob
• Jain Advait
• Rivas Miguel
• Magnusson Lee

Classifications

• B25J9/1692 Primary

  Calibration of manipulator · CPC title

• Y10S901/09

  Closed loop, sensor feedback controls arm movement · CPC title

• G01D5/2448 Primary

  Correction of gain, threshold, offset or phase control · CPC title

• Y10S901/47

  Optical · CPC title

• Y10S901/02

  Arm motion controller · CPC title