Automated work piece moment of inertia (MOI) identification system and method for same

Patent metadata

Field	Value
Publication number	US-10369702-B2
Application number	US-201715406944-A
Country	US
Kind code	B2
Filing date	Jan 16, 2017
Priority date	Oct 17, 2016
Publication date	Aug 6, 2019
Grant date	Aug 6, 2019

Abstract

A method and system for identifying a moment of inertia (MOI) of a work piece includes coupling the work piece to a manipulator assembly such as a 6-axis robotic arm or 3-axis gimbal. The manipulator assembly includes a force/torque sensor and a motion feedback sensor. The manipulator assembly moves the work piece with three-dimensional motion. Force, torque and movement measurements are made as the work piece moves. The MOI is identified according to the force and torque measurements and rotational accelerations derived from the measured movement. The measurements may be used to identify the products of inertia (POI) and center of mass of the work piece.

First claim

What is claimed is:

1. A method for automatically identifying a moment of inertia (MOI) of a work piece comprising:
coupling a work piece to a manipulator assembly including a manipulator arm having two or more members interconnected with actuators at joints and an effector assembly having a force/torque sensor, wherein:
the effector assembly is interposed between the manipulator arm and the work piece; and
the force/torque sensor of the effector assembly is configured to measure force and torque transmitted from the work piece to the manipulator assembly and a motion feedback sensor is configured to measure motion of the work piece;

moving the work piece and the effector assembly in a three-axis coordinate system with the actuators of the manipulator arm, said motion including at least rotation of the work piece about each of three axes;
measuring with the force/torque sensor at least a first force and at least a first torque for each of the three axes as the work piece is moving;
measuring with the motion sensor the movement of the work piece including at least a first rotation about each of the three axes; and
identifying the MOI in each of the three axes according to at least the measured first torque and first rotation for each of the three axes.

2. The method of claim 1 , wherein the manipulator assembly includes a robotic arm capable of 6-axis motion including three-axis translation and three-axis rotation.

3. The method of claim 2 , wherein coupling the work piece to the manipulator assembly includes the robotic arm autonomously picking up the work piece.

4. The method of claim 3 , wherein moving the work piece in the three-axis coordinate system and measuring at least the first force, at least the first torque and at least the first rotation about each of the three axes is included with moving the work piece between first and second pieces of equipment in one or more of an assembly line or a testing line with the manipulator assembly.

5. The method of claim 2 , further comprising:
moving the work piece in the three-axis coordinate system with the manipulator assembly, said motion including at least rotation about each of three axes offset by 45 degrees from the three axes of the coordinate system;
measuring with the force/torque sensor at least a first force and at least a first torque for each of the three offset axes as the work piece is moving;
measuring with the motion sensor the movement of the work piece including at least a first rotation about each of the three offset axes; and
identifying products of inertia (POI) of the work piece in each of the three offset axes according to at least the measured first torque and at least the first force and movement for each offset axis.

6. The method of claim 2 , further comprising
positioning the work piece in at least two different static orientations relative to a gravity vector with the manipulator assembly, measuring a force and a torque in different static orientations, and identifying the work piece center of mass according to the force and torque measurements.

7. The method of claim 2 , wherein moving the work piece in three-axis coordinate system includes with the robotic arm, moving the work piece to each of three orthogonal orientations, and for each orientation,
rotating the work piece about an axis parallel to a gravity vector and through a center of mass of the work piece;
measuring with the force/torque sensor at least the first torque as the work piece is rotating about the axis;
measuring with the motion sensor at least the first rotation of the work piece about the axis; and
identifying the MOI for the orientation according to at least the measured first torque and first rotation.

8. The method of claim 2 , wherein moving the work piece in the three-axis coordinate system includes with the robotic arm, moving the work piece to each of three orthogonal orientations, and for each orientation,
rotating the work piece about an axis;
measuring with the force/torque sensor at least the first force and at least the first torque as the work piece is rotating about the axis;
measuring with the motion sensor the rotation of the work piece about the axis; and
identifying the MOI for the orientation according to at least the measured first force, first torque and rotation.

9. The method of claim 8 , wherein the axis is at an unknown distance dl from an unknown center of mass for the work piece, further comprising repeating the rotation and measurement for each orientation at a different unknown distance d 1 from the unknown center of mass, and identifying both the MOI and center of mass from the measured first force, first torque and first rotation for the three axis for distances d 1 and d 2 .

10. The method of claim 2 , wherein moving the work piece in the three-axis coordinate system includes with the robotic arm, moving the work piece to simultaneously rotate about all three axes, wherein identifying the MOI includes simultaneously identifying the MOI for all three axes.

11. The method of claim 1 , comprising coupling an effector assembly including the force/torque sensor and the motion feedback sensor with the manipulator assembly.

12. The method of claim 11 , wherein the motion feedback sensor comprises an inertial measurement unit (IMU) that measures velocity and acceleration both in translation along and in rotation about each of the three axes.

13. The method of claim 1 , wherein the motion feedback sensor comprises a plurality of encoders coupled to stage motors that provide the rotation of the manipulator assembly about each of the three axes.

14. A method for automatically identifying a moment of inertia (MOI) of a work piece comprising:
coupling a work piece to an effector assembly, the effector assembly coupled with a robotic arm capable of six-axis motion including three-axis translation and three-axis rotation, the effector assembly includes:
a work piece interface configured to grasp and hold the work piece;
a torque sensor configured to measure torque transmitted from the work piece to the effector assembly; and
a motion feedback sensor configured to measure motion of the work piece about each said axis, the motion feedback sensor is coupled with at least one of the effector assembly or the robotic arm;

determining an MOI for each of three orthogonal orientations of the work piece established by the robotic arm including:
rotating the effector assembly and the work piece about an axis parallel to a gravity vector and through a center of mass of the work piece with the robotic arm;
measuring with the torque sensor at least a first torque as the work piece is rotating about the axis;
measuring with the motion sensor at least a first rotation of the work piece about the axis; and
identifying the MOI for the orientation according to at least the measured first torque and first rotation.

15. A method for automatically identifying a center of mass and a moment of inertia (MOI) of a work piece comprising:
coupling a work piece to an effector assembly having a force/torque sensor, the effector assembly coupled proximate an end of a manipulator assembly, the manipulator assembly includes a motion feedback sensor configured to measure motion of the work piece;
identifying the center of mass of the work piece including:
positioning the effector assembly and the work piece in at least two different static orientations relative to a gravity vector with the manipulator assembly;
measuring a force and a torque in the different static orientations with the force/torque sensor of the effector assembly; and
iden

Assignees

• Raytheon Co

Inventors

• Vulcano Anthony R
• Holyoak Vonn L
• Moosman Bryan R

Classifications

• B25J13/085 Primary

  Force or torque sensors (B25J13/082, B25J13/084 take precedence) · CPC title

• B25J11/00

  Manipulators not otherwise provided for · CPC title

• G01M1/10

  Determining the moment of inertia · CPC title

• G01L5/226

  to manipulators, e.g. the force due to gripping · CPC title

• G01M1/122

  Determining position of centre of gravity · CPC title