Device for teaching position and posture for robot to grasp workpiece, robot system, and method

1 . A device configured to teach a position and orientation at which a robot grips a workpiece with a hand in a control coordinate system for controlling the robot, the device comprising a processor configured to:

acquire a plurality of pieces of image data obtained by repeatedly imaging the workpiece by a vision sensor arranged at a known position in the control coordinate system when the robot grips the workpiece with the hand;

respectively acquire a plurality of pieces of workpiece position data, each of which indicates a position and orientation of the workpiece in the control coordinate system when the vision sensor images one of the plurality of pieces of image data, based on the plurality of pieces of image data, when the robot grips the workpiece with the hand;

respectively acquire a plurality of pieces of hand position data, each of which indicates a position and orientation of the hand in the control coordinate system when the vision sensor images the one of the plurality of pieces of image data, when the robot grips the workpiece with the hand;

respectively acquire a plurality of pieces of teaching position data, each of which indicates a positional relationship between the hand and the workpiece in the control coordinate system when the vision sensor images the one of the plurality of pieces of image data, based on the plurality of pieces of workpiece position data and on the plurality of pieces of hand position data, the teaching position data is represented as coordinates of the control coordinate system; and obtain new teaching position data by excluding the coordinates of the teaching position data, which are outside of a predetermined allowable range, among the coordinates of the plurality of pieces of the teachings position data,

wherein the robot is controlled to grip the workpiece based on the acquired teaching position data.

2 . The device of claim 1 , wherein the processor is further configured to operate the robot so as to repeatedly change the orientation of the hand gripping the workpiece,

wherein the processor is configured to acquire a plurality of pieces of the image data imaged by the vision sensor every time the processor changes the orientation of the hand,

wherein the processor is configured to acquire a plurality of pieces of the workpiece position data respectively when each of the plurality of pieces of the image data is imaged, based on each of the plurality of pieces of the image data acquired by the processor,

wherein the processor is configured to acquire a plurality of pieces of the hand position data respectively when each of the plurality of pieces of the image data is imaged, and

wherein the processor is configured to acquire a plurality of pieces of the teaching position data respectively when each of the plurality of pieces of the image data is imaged, based on the respective pieces of the workpiece position data acquired by the processor and on the respective pieces of the hand position data acquired by the processor.

3 . The device of claim 2 , wherein the processor is configured to obtain new teaching position data to be used for an operation to cause the robot to grip the workpiece with the hand, based on the plurality of pieces of the acquired teaching position data.

4 . The device of claim 3 , wherein the teaching position data is represented as coordinates of the control coordinate system, and

wherein the processor is configured to obtain the new teaching position data by:

obtaining an average of the coordinates of the plurality of pieces of the teaching position data.

5 . The device of claim 1 , wherein the processor is further configured to generate an operation program in which the teaching position data is defined.

6 . The device of claim 1 , wherein the processor is configured to acquire, as the workpiece position data, data indicating a position and orientation in the control coordinate system of a workpiece model which models the workpiece when the workpiece model is matched to the workpiece shown in the image data.

7 . The device of claim 1 , wherein the control coordinate system includes:

a robot coordinate system set to the robot;

a workpiece coordinate system set to the workpiece;

a tool coordinate system set to the hand and having a known positional relationship with the robot coordinate system; and

a sensor coordinate system set to the vision sensor and having a known positional relationship with the robot coordinate system,

wherein the vision sensor is arranged at the known position in the robot coordinate system,

wherein the workpiece position acquisition unit is configured to:

acquire first coordinates in the sensor coordinate system of the workpiece coordinate system indicating a position and orientation of the workpiece shown in the image data; and

acquire, as the workpiece position data, second coordinates of the workpiece coordinate system in the robot coordinate system by transforming the first coordinates into the robot coordinate system,

wherein the processor is configured to acquire, as the hand position data, third coordinates in the robot coordinate system of the tool coordinate system indicating a position and orientation of the hand, and

wherein the processor is configured to acquire the teaching position data as coordinates of the workpiece coordinate system in the tool coordinate system or as coordinates of the tool coordinate system in the workpiece coordinate system, based on the second coordinates and the third coordinates.

8 . A robot system comprising:

a robot including a hand configured to grip a workpiece;

a vision sensor configured to image the workpiece; and

a device configured to teach a position and orientation at which the robot grips the workpiece with the hand in a control coordinate system for controlling the robot, the device comprising a processor configured to:

acquire a plurality of pieces of image data obtained by repeatedly imaging the workpiece by a vision sensor arranged at a known position in the control coordinate system when the robot grips the workpiece with the hand;

respectively acquire a plurality of pieces of workpiece position data, each of which indicates a position and orientation of the workpiece in the control coordinate system when the vision sensor images one of the plurality of pieces of image data, based on the plurality of pieces of image data, when the robot grips the workpiece with the hand;

respectively acquire a plurality of pieces of hand position data, each of which indicates a position and orientation of the hand in the control coordinate system when the vision sensor images the one of the plurality of pieces of image data, when the robot grips the workpiece with the hand;

respectively acquire a plurality of pieces of teaching position data, each of which indicates a positional relationship between the hand and the workpiece in the control coordinate system when the vision sensor images the one of the plurality of pieces of image data, based on the plurality of pieces of workpiece position data and on the plurality of pieces of hand position data, the teaching position data is represented as coordinates of the control coordinate system; and

obtain new teaching position data by excluding the coordinates of the teaching position data, which are outside of a predetermined allowable range, among the coordinates of the plurality of pieces of the teaching position data,

wherein the robot is controlled to grip the workpiece based on the acquired teaching position data.

9 . The robot system of claim 8 , comprising a controller configured to control the robot so as to grip the workpiece with the hand, based on second image data of the workpiece imaged by the vision sensor,

wherein the controller is configured to:

acquire, as second workpiece position data, data indicating a position and orientation in the control coordinate system of the workpiece shown in the second image data; and

determine a position and orientation of the hand in the control coordinate system when the hand grips the workpiece imaged by the vision sensor, based on the second workpiece position data and the teaching position data.

10 . A method of teaching a position and orientation at which a robot grips a workpiece with a hand in a control coordinate system for controlling the robot, the method comprising:

acquiring, by a processor, a plurality of pieces of image data obtained by repeatedly imaging the workpiece by a vision sensor arranged at a known position in the control coordinate system when the robot grips the workpiece with the hand;

respectively acquiring, by the processor, a plurality of pieces of workpiece position data, each of which indicates a position and orientation of the workpiece in the control coordinate system when the vision sensor images one of the plurality of pieces of image data, based on the plurality of pieces of image data, when the robot grips the workpiece with the hand;

respectively acquiring, by the processor, a plurality of pieces of hand position data, each of which indicates a position and orientation of the hand in the control coordinate system when the vision sensor images the one of the plurality of pieces of image data, when the robot grips the workpiece with the hand;

respectively acquiring, by the processor, a plurality of pieces of teaching position data, each of which indicates a positional relationship between the hand and the workpiece in the control coordinate system when the vision sensor images the one of the plurality of pieces of image data, based on the plurality of pieces of workpiece position data and on the plurality of pieces of hand position data, the teaching position data is represented as coordinates of the control coordinate system;

obtaining new teaching position data by excluding the coordinates of the teaching position data, which are outside of a predetermined allowable range, among the coordinates of the plurality of pieces of the teaching position data; and

controlling the robot to grip the workpiece based on the acquired teaching position data.