MASS MEASUREMENT DEVICE

• US 20140230581A1
• Filed: 09/18/2012
• Published: 08/21/2014
• Est. Priority Date: 09/20/2011
• Status: Active Grant

• Current Assignee: Ishida Company Limited
• Original Assignee: Ishida Company Limited
• Inventors: Nakatani, Makoto, Suzuki, Akihito, Konishi, Satoshi
• Granted Patent: US 9,140,598 B2
• Time in Patent Office: Days
• US Class Current: 73/865
• CPC Class Codes: B25J 13/082 Grasping-force detectors in general G01L5/16, G01L5/22
• CPC Class Codes: B25J 13/085 Force or torque sensors B25J13/082, B25J13/084 take precedence
• CPC Class Codes: B25J 13/088 with position, velocity or acceleration sensors
• CPC Class Codes: B25J 19/02 Sensing devices
• CPC Class Codes: G01G 19/00 Weighing apparatus or methods adapted for special purposes not provided for in the preceding groups electric measuring arrangements involving comparison with a reference value G01R17/00
• CPC Class Codes: G01G 3/14 measuring variations of electrical resistance G01G3/13 takes precedence
• 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: G05B 2219/37261 Encoder and potentiometer to detect fault measurement
• CPC Class Codes: G05B 2219/37357 Force, pressure, weight or deflection
• CPC Class Codes: G05B 2219/40549 Acceleration of end effector

Abstract

Amass measurement device measures the mass of an article, even when the article is being moved. A mass measurement device includes a robot hand, a robot arm, a force sensor, an acceleration sensor, and a control unit. The robot hand holds an article (Q). The robot arm moves the robot hand. The force sensor is provided between the robot hand and the robot arm and measures force acting on the article (Q) during movement. The acceleration sensor measures acceleration acting on the article (Q) during the movement. The control unit runs and controls the robot hand and the robot arm, and calculates the mass of the article (Q) on the basis of the force and acceleration acting on the article (Q) during the movement.

Claims

1. A mass measurement device for measuring a mass of an article while the article is being moved, the mass measurement device comprising:

a holding mechanism configured to hold the article;

a movement mechanism coupled to the holding mechanism and configured to move the holding mechanism;

a force measurement unit fixedly coupled between the holding mechanism and the movement mechanism and configured to measure a force acting on the article during movement and configured to output corresponding force measurement data;

an acceleration measurement unit configured to measure acceleration acting on the article during movement and configured to output acceleration data; and

a control unit configured to operatively control the holding mechanism and the movement mechanism, and calculate the mass of the article on the basis of the force and the acceleration acting on the article during movement.

2. The mass measurement device according to claim 1, wherein the control unit divides the force acting on the article during movement by the acceleration acting on the article during movement to calculate the mass of the article.

3. The mass measurement device according to claim 1, wherein a direction in which the force measurement unit detects and a direction in which the acceleration measurement unit detects are directions in which gravity does not act, and are the same.

4. The mass measurement device according to claim 1, wherein the direction in which the force measurement unit detects and a direction in which the acceleration measurement unit detects are directions in which gravity acts, and are the same.

5. The mass measurement device according to claim 1, wherein at least two sets of the force measurement unit and the acceleration measurement unit are provided, directions in which the force measurement unit and the acceleration measurement unit detect are the same in each set, and detection directions for each set intersect each other.

6. The mass measurement device according to claim 1, wherein the acceleration measurement unit measures acceleration that acts on the article on the basis of a run command outputted from the control unit to the movement mechanism.

7. The mass measurement device according to claim 1, further comprising an external monitoring device secured in a non-moving position and used for monitoring the article, or the operation of the holding mechanism or the movement mechanism,

wherein the acceleration measurement unit measures acceleration that acts on the article on the basis of data obtained from the external monitoring device.

8. The mass measurement device according to claim 7, wherein the external monitoring device is a laser displacement gauge.

9. The mass measurement device according to claim 7, wherein the external monitoring device is a camera.

10. The mass measurement device according to claim 1, further comprising a camera attached to the holding mechanism, wherein

the acceleration measurement unit measures acceleration that acts on the article on the basis of a predetermined reference point externally set and image data obtained from the camera.

11. The mass measurement device according to claim 1, wherein at least one of an extremum of the force measurement data showing the result of the measurement made by the force measurement unit and an extremum of the acceleration data showing the result of the measurement made by the acceleration measurement unit is used in the calculation of the mass of the article.

12. The mass measurement device according to claim 11, wherein a time at which the force measurement data takes on the extremum is offset from a time at which the acceleration data takes on the extremum, and

both the extremum of the force measurement data and the extremum of the acceleration data are used in the calculation of the mass of the article.

13. The mass measurement device according to claim 11, wherein the time at which the force measurement data takes on the extremum is offset from the time at which the acceleration data takes on the extremum,

the value of the acceleration data at the time that the force measurement data takes on the extremum is furthermore used for calculating the mass of the article when the extremum of the force measurement data is used for calculating the mass of the article, and

the value of the force measurement data at the time that the acceleration data takes on the extremum is furthermore used for calculating the mass of the article when the extremum of the acceleration data is used for calculating the mass of the article.

14. The mass measurement device according to claim 11, wherein

the control unit

extracts first data of the force measurement data, the first data corresponding to inclusion in a first predetermined range that includes the extremum of the data,

extracts second data of the acceleration data, the second data corresponding to inclusion in a second predetermined range that includes the extremum of the data, and

calculates a weighted average for the first data and the second data thus extracted, and uses the results to calculate the mass of the article.

15. The mass measurement device according to claim 1, wherein

the control unit calculates the mass of the article using the difference between the force measurement data at two points obtained by the force measurement unit, and the difference between the acceleration measurement data at two points obtained by the acceleration measurement unit in coordination with the force measurement unit.

16. The mass measurement device according to claim 15, wherein

the two points obtained by the force measurement unit are two points having a low rate of change with respect to time.

17. The mass measurement device according to claim 16, wherein

the points at which a differential value of the output obtained by the force measurement unit is near zero are preferentially selected as the two points having the low rate of change.

18. The mass measurement device according to claim 16, wherein

the points at which the absolute value of the output obtained by the force measurement unit is large and a differential value is small are preferentially selected as the two points having the low rate of change.

19. The mass measurement device according to claim 15, wherein the two points obtained by the force measurement unit are both extremum points.

20. The mass measurement device according to claim 15, wherein the two points obtained by the force measurement unit are a maximum point and a minimum point.

21. The mass measurement device according to claim 15, wherein the difference between the force measurement values at two points obtained by the force measurement unit is a predetermined value or greater.

22. The mass measurement device according to claim 1, wherein

the control unit

calculates the mass of the article using the difference between the acceleration measurement values at two points obtained by the acceleration measurement unit, and

the difference between the force measurement values at two points obtained by the force measurement unit in coordination with the acceleration measurement unit.

23. The mass measurement device according to claim 22, wherein the two points obtained by the acceleration measurement unit are two points in which the rate of change with respect to time is small.

24. The mass measurement device according to claim 1, comprising:

a first mass measurement unit for moving the article and dividing the force acting on the article during movement by the acceleration acting on the article during movement to calculate the mass of the article, the first mass measurement unit having the holding mechanism, the movement mechanism, the force measurement unit, and the acceleration measurement unit;

a second mass measurement unit for dividing, by gravitational acceleration, the vertical force acting on the article while the article is held in the first mass measurement unit to calculate the mass of the article; and

a control unit for controlling the first mass measurement unit and the second mass measurement unit,

the control unit preferentially measuring mass using the second mass measurement unit when a predetermined condition holds true.

25. The mass measurement device according to claim 1, comprising:

a first mass measurement unit for moving the article and dividing the force acting on the article during movement by the acceleration acting on the article during movement to calculate the mass of the article, the first mass measurement unit having the holding mechanism, the movement mechanism, the force measurement unit, and the acceleration measurement unit;

a second mass measurement unit for dividing the vertical force acting on the article by gravitational acceleration to calculate the mass of the article, in coordination with the first mass measurement unit; and

a control unit for controlling the first mass measurement unit and the second mass measurement unit,

the control unit using a measurement value of the second mass measurement unit more preferentially than a measurement value of the first mass measurement unit when a predetermined condition holds true.

26. The mass measurement device according to claim 24, wherein, in the first mass measurement unit, the directions of sensitivity of the force measurement unit and the acceleration measurement unit are three mutually orthogonal directions including the vertical direction.

27. The mass measurement device according to claim 24, wherein, in the first mass measurement unit, the directions of sensitivity of the force measurement unit and the acceleration measurement unit are sloped in a predetermined angle downward with respect to the horizontal plane.

28. The mass measurement device according to claim 24, wherein, in the first mass measurement unit, the movement mechanism rotates about two mutually orthogonal axes including the vertical axis, and the directions of sensitivity of the force measurement unit and the acceleration measurement unit are any desired directions.

29. The mass measurement device according to claim 24, wherein the predetermined condition is that the output of the acceleration measurement unit of the first mass measurement unit be less than a predetermined value.