Robot having workpiece mass measurement function

• US 9,459,136 B2
• Filed: 05/06/2014
• Issued: 10/04/2016
• Est. Priority Date: 09/09/2011
• Status: Active Grant

• Current Assignee: Fanuc Corporation
• Original Assignee: Fanuc Corporation
• Inventors: Sato, Takashi
• Primary Examiner(s): Lyons, Michael A
• Assistant Examiner(s): Singer, David L
• Application Number:
  US14/271,033
• Publication Number:
  US 20140238157A1
• Time in Patent Office: 882 Days
• Field of Search: 738/65, 734/95, 735/09, 735/10, 735/140.1, 738/625.41, 901/46, 702/141, 702/41, 702174-175, 702/199, 177/139, 177/145, 177/148, 177/149
• US Class Current: 1/1
• CPC Class Codes: B25J 13/085 Force or torque sensors B25J13/082, B25J13/084 take precedence
• CPC Class Codes: B25J 19/02 Sensing devices
• CPC Class Codes: B25J 9/1633 compliant, force, torque control, e.g. combined with position control
• CPC Class Codes: G01G 19/086 wherein the vehicle mass is dynamically estimated
• CPC Class Codes: G01G 21/00 Details of weighing apparatus
• CPC Class Codes: G01G 9/00 Methods of, or apparatus for, the determination of weight, not provided for in groups G01G1/00 - G01G7/00
• CPC Class Codes: G01L 5/009 Force sensors associated with material gripping devices
• CPC Class Codes: G01L 5/16 for measuring several components of force
• CPC Class Codes: G05B 2219/37357 Force, pressure, weight or deflection
• CPC Class Codes: G05B 2219/40549 Acceleration of end effector
• CPC Class Codes: G05B 2219/40606 Force, torque sensor in finger
• CPC Class Codes: Y10S 901/46 Sensing device

Abstract

A robot (1) having a workpiece mass measurement function for measuring the mass of a workpiece that is held, includes a force measurement unit (5) that measures the force that is applied to the tip part (2) of the mechanism part of the robot (1), and a mass estimation unit (11) that estimates the mass of the workpiece that is held by the robot (1), based on information about the force acquired by the force measurement unit (5) while the robot (1) is moving.

Claims

1. A robot having a workpiece mass measurement function for measuring a mass of a workpiece held by the robot, the robot comprising:

a force measurement unit configured to measure a force applied to a tip part of a mechanism part of the robot; and

a mass estimation unit configured to estimate the mass of the workpiece held by the robot, based on the force measured by the force measurement unit while the robot is moving;

wherein

the mass estimation unit comprises an acceleration acquiring unit configured to acquire, by measuring or estimating, an acceleration applied to the tip part of the mechanism part of the robot;

the mass estimation unit is configured to estimate the mass of the workpiece held by the robot, based on an equation between the force measured by the force measurement unit while the robot is moving, the acceleration acquired by the acceleration acquiring unit and the mass of the workpiece held by the robot;

the force measurement unit is configured to measure the force in a plurality of directions;

the acceleration acquiring unit is configured to acquire the acceleration in the plurality of directions;

the mass estimation unit is configured to estimate the mass with respect to the plurality of directions, so that the mass corresponding to a direction where an absolute value of the acceleration is greatest, among the plurality of directions, is made a mass estimation value of the mass of the workpiece, and

at a given time,

the force measurement unit is configured to measure force values of the force in the plurality of directions,

the acceleration acquiring unit is configured to acquire acceleration values of the acceleration in the plurality of directions,

the mass estimation unit is configured to determine the greatest absolute value, among the acquired acceleration values, as corresponding to one direction among the plurality of directions, and

the mass estimation unit is configured to use the force value and the acceleration value in said one direction to estimate the mass of the workpiece.

2. The robot as defined in claim 1, wherein the force measurement unit is configured to estimate the mass of the workpiece based on

a force measurement value of the force measured by the force measurement unit when the workpiece is held by the robot, and

a force measurement value of the force measured by the force measurement unit when the workpiece is not held by the robot.

3. The robot as defined in claim 1, wherein a posture of the tip part of the mechanism part is not changed while the robot is moving.

4. The robot as defined in claim 1, wherein an average value of a plurality of masses of the workpiece estimated by the mass estimation unit at a plurality of times while the robot is moving, is made a mass estimation value of the mass of the workpiece.

5. The robot as defined in claim 1, wherein the acceleration acquiring unit is configured to calculate the acceleration by a dynamics equation.

6. The robot as defined in claim 1, wherein the acceleration acquiring unit is configured to acquire the acceleration measured by an acceleration sensor attached to the robot.

7. The robot as defined in claim 1, wherein the mass estimation unit is configured to estimate the mass of the workpiece held by the robot, based on the force measured by the force measurement unit while the tip part of the mechanism part is moving on a plane perpendicular to a direction of a gravitational force applied to the tip part of the mechanism part of the robot without changing the posture of the tip part.

8. The robot as defined in claim 1, wherein the mass estimation unit is configured to estimate the mass of the workpiece held by the robot, based on the force measured by the force measurement unit while the tip part of the mechanism part of the robot is moving on a linear path at constant speed.

9. The robot as defined in claim 7, further comprising:

a posture acquiring unit configured to acquire a posture of the tip part of the mechanism part of the robot,

wherein the mass estimation unit is configured to estimate the mass of the workpiece held by the robot, based on the forces measured by the force measurement unit in the plurality of directions and the posture acquired by the posture acquiring unit.

10. The robot as defined in claim 8, further comprising:

a posture acquiring unit configured to acquire a posture of the tip part of the mechanism part of the robot,

wherein the mass estimation unit is configured to estimate the mass of the workpiece held by the robot, based on the forces measured by the force measurement unit in the plurality of directions and the posture acquired by the posture acquiring unit.