Robot system having a robot for conveying a workpiece

Patent metadata

Field	Value
Publication number	US-9126337-B2
Application number	US-201414255075-A
Country	US
Kind code	B2
Filing date	Apr 17, 2014
Priority date	Apr 18, 2013
Publication date	Sep 8, 2015
Grant date	Sep 8, 2015

Abstract

A robot system includes a three-dimensional measuring device for obtaining positional information of a workpiece, a robot having a tool capable of holding a workpiece, and a control device for controlling the robot. The control device stores association data which associate the positional information of the workpiece with a center-of-gravity position of the workpiece. A center-of-gravity position of the workpiece to be picked out is estimated, based on the positional information obtained by the three-dimensional measuring device and on to the association data. The control device determines at least one of the holding position of the workpiece, the picking-out direction and the position and posture of the tool, based on the estimated center-of-gravity position.

First claim

What is claimed is:

1. A robot system for picking out and conveying a workpiece placed in a three-dimensional space, the robot system comprising:
a three-dimensional measuring device for measuring a surface position on the workpiece to obtain positional information of a plurality of points on a surface of the workpiece in a three-dimensional space;
a robot movable in accordance with a specified position and posture;
a tool attached to a tip portion of the robot and adapted to hold the workpiece;
a force measuring part for measuring a force acting on the tool by the workpiece when the workpiece is held by the tool; and
a control device for controlling the robot,
the control device comprising:
a workpiece identifying part for identifying a workpiece to be picked out and a position and posture of the workpiece, based on the positional information of the plurality of points obtained by the three-dimensional measuring device;
a picking position and posture determining part for determining a holding position of the workpiece, a picking-out direction of the workpiece and a position and posture of the tool, so as to pick out the workpiece identified by the workpiece identifying part;
a center-of-gravity position calculating part for calculating a center-of-gravity position of the workpiece held by the tool, based on force data measured by the force measuring part with a plurality of postures of the robot holding the workpiece;
an associating part for associating the positional information of the workpiece held by the tool, which is obtained by the three-dimensional measuring device with the center-of-gravity position of the workpiece calculated by the center-of-gravity position calculating part;
an association storing part for storing a result of the association made by the associating part; and
a center-of-gravity position estimating part for estimating a center-of-gravity position of the workpiece identified by the workpiece identifying part, based on the result of the association stored by the association storing part,
wherein the picking position and posture determining part is adapted to determine at least one of the holding position of the workpiece identified by the workpiece identifying part at the time of picking out the workpiece, the picking-out direction of the workpiece, the position and posture of the tool, based on the center-of-gravity position of the workpiece estimated by the center-of-gravity position estimating part.

2. The robot system according to claim 1 ,
wherein the picking position and posture determining part is adapted to determine a holding position of the workpiece, based on the center-of-gravity position of the workpiece estimated by the center-of-gravity position estimating part, and
wherein the picking position and posture determining part is adapted to determine an actual holding position of the workpiece at which the workpiece can be held, the actual holding position of the workpiece being a holding position falling within a range defined by a predetermined threshold from the holding position situated at a shortest distance from the center-of-gravity position of the workpiece estimated by the center-of-gravity position estimating part.

3. The robot system according to claim 1 ,
wherein the picking position and posture determining part is adapted to determine a holding position of the workpiece, based on the center-of-gravity position of the workpiece estimated by the center-of-gravity position estimating part, and
wherein the picking position and posture determining part is adapted to determine an actual holding position of the workpiece at which the workpiece can be held, based on the center-of-gravity position of the workpiece and on the picking-out direction of the workpiece or the posture of the tool at the time of picking out the workpiece.

4. The robot system according to claim 1 , wherein the picking position and posture determining part is adapted to determine a position and posture of the tool at the time picking out the workpiece so that a moving direction at the time of picking out the workpiece matches a direction oriented from the center-of-gravity position to the holding position or to a position offset from the holding position by a predetermined distance.

5. The robot system according to claim 1 , wherein the workpiece identifying part is adapted to identify another workpiece as an alternative, in the case where a distance between the center-of-gravity position and the holding position determined by the picking position and posture determining part or a position offset from the holding position exceeds a predetermined threshold.

6. The robot system according to claim 1 , wherein in the case where the workpiece identified by the workpiece identifying part is under another workpiece, and a distance between a position defined in an area where the workpieces are placed on top of another and the holding position of the workpiece determined by the picking position and posture determining part or a position offset from the holding position by a predetermined distance is not greater than a predetermined threshold, the workpiece identifying part is adapted to identify another workpiece as an alternative.

7. The robot system according to claim 1 , further comprising:
a detecting part for detecting an intensity of a force and vibration generated at the time of picking out the workpiece, based on force data at the time of picking out the workpiece; and
a stability determining part for determining stability at the time of picking out the workpiece, based on a result of detection by the detecting part,
wherein the workpiece identifying part is adapted to change a priority order at the time of identifying the workpiece, based on a result of determination by the stability determining part.

8. The robot system according to claim 1 , further comprising:
a detecting part for detecting an intensity of a force and vibration generated at the time of picking out the workpiece, based on force data at the time of picking out the workpiece; and
a stability determining part for determining stability at the time of picking out the workpiece, based on a result of detection by the detecting part,
wherein the picking position and posture determining part is adapted to change a holding position of the workpiece, a picking-out direction of the workpiece or a posture of the tool at the time of picking out the workpiece, based on a result of determination by the stability determining part.

Assignees

• Fanuc Corp

Inventors

• Iwatake Takahiro

Classifications

• B25J9/1697 Primary

  Vision controlled systems · CPC title

• B25J9/1694 Primary

  characterised by use of sensors other than normal servo-feedback from position, speed or acceleration sensors, perception control, multi-sensor controlled systems, sensor fusion · CPC title

• G05B2219/35124

  Calculate center of gravity of object · CPC title

• G05B2219/39504

  Grip object in gravity center · CPC title

• G05B2219/40053

  Pick 3-D object from pile of objects · CPC title