Mass measurement device

• US 9,140,598 B2
• Filed: 09/18/2012
• Issued: 09/22/2015
• 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
• Primary Examiner(s): Williams, Hezron E
• Assistant Examiner(s): ZHONG, XIN Y
• Application Number:
  US14/345,723
• Publication Number:
  US 20140230581A1
• Time in Patent Office: 1,099 Days
• Field of Search: 738/65, 734/95, 73509-510, 735/040.1, 702/141, 702/417, 177/139, 177/145, 177/149
• US Class Current: 1/1
• 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

A mass 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 in motion, the mass measurement device comprising:

a movement mechanism;

a force sensor fixedly attached to a distal end of the movement mechanism for movement therewith;

a holding mechanism fixedly attached to the force sensor, and configured to grab and hold the article and move the article in response to movement operations of the movement mechanism, the force sensor being configured to measure a force acting on the article during movement and output corresponding force measurement data;

an acceleration sensor fixedly attached to the holding mechanism for movement therewith and configured to measure acceleration acting on the article during movement and configured to output acceleration data; and

a control circuit configured to operatively control the holding mechanism and the movement mechanism, and calculate the mass of the article on the basis of the force measurement data and the acceleration data,

the control circuit being configured to conduct a first mass measurement dividing the force measurement data acting on the article acquired during a single movement of the article by the acceleration data acting on the article acquired during the single movement in order to calculate the mass of the article;

the control circuit being configured to conduct a second mass measurement of the article during the single movement at a different time from the first mass measurement, the control circuit including determining a vertical force acting on the article from the force measurement data acquired at the different time and determining gravitational acceleration from the acceleration data at the different time, the second mass measurement including dividing the vertical force acting on the article by the gravitational acceleration while the article is held by the holding mechanism during the single movement in order to calculate the mass of the article; and

the control circuit being configured to determine mass of the object using the second mass measurement when a predetermined condition holds true, the predetermined condition being that the output of the first acceleration measurement must be less than a predetermined value such that a maximum output of the first acceleration measurement is less than a predetermined threshold value.

2. The mass measurement device according to claim 1, wherein, directions of sensitivity of the force sensor and the acceleration sensor include force and acceleration detection in three mutually orthogonal directions including the vertical direction.

3. The mass measurement device according to claim 1, wherein, directions of sensitivity of the force sensor and the acceleration sensor are sloped in a predetermined angle downward with respect to the horizontal plane.

4. The mass measurement device according to claim 1, wherein, the movement mechanism is configured to rotate about two mutually orthogonal axes including the vertical axis, and directions of sensitivity of the force sensor and the acceleration sensor include two mutually orthogonal directions corresponding to the mutually orthogonal axes.

5. A mass measurement device for measuring a mass of an article while the article is in motion, 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 sensor fixedly attached to the holding mechanism and fixedly attached to the movement mechanism for movement therewith and configured to measure a force acting on the article during movement and configured to output corresponding force measurement data;

an acceleration sensor fixedly attached to the force sensor for movement therewith and configured to measure acceleration acting on the article during movement and configured to output acceleration data; and

a control circuit configured to operatively control the holding mechanism and the movement mechanism, the control circuit being connected to the force sensor and the acceleration sensor receiving the force measurement data and acceleration data therefrom, the control circuit being configured determine at least one data point of a plurality of data points in the force measurement data that is an extremum and determine at least one data point of a plurality of data points in the acceleration data that is an extremum, the control circuit being further configured to calculate mass acting on the article on the basis of the force measurement data and the acceleration data during a single movement of the article at a time corresponding to at least one of the extremum of the force measurement data and the extremum of the acceleration data,

the control circuit is further configured to calculate the mass of the article when the extremum of the force measurement data is offset from the extremum of the acceleration data with respect to time, and

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

6. A mass measurement device for measuring a mass of an article while the article is in motion, 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 sensor fixedly attached to the holding mechanism and fixedly attached to the movement mechanism for movement therewith and configured to measure a force acting on the article during movement and configured to output corresponding force measurement data;

an acceleration sensor fixedly attached to the force sensor for movement therewith and configured to measure acceleration acting on the article during movement and configured to output acceleration data; and

a control circuit configured to operatively control the holding mechanism and the movement mechanism, the control circuit being connected to the force sensor and the acceleration sensor receiving the force measurement data and acceleration data therefrom, the control circuit being configured determine at least one data point of a plurality of data points in the force measurement data that is an extremum and determine at least one data point of a plurality of data points in the acceleration data that is an extremum, the control circuit being further configured to calculate mass acting on the article on the basis of the force measurement data and the acceleration data during a single movement of the article at a time corresponding to at least one of the extremum of the force measurement data and the extremum of the acceleration data,

the control circuit being further configured to calculate the mass of the article when the extremum of the force measurement data is offset from the extremum of the acceleration data with respect to time, a value of the acceleration data at a time corresponding to the extremum of the force measurement data 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 a value of the force measurement data at the time corresponding to the extremum of the acceleration data 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.