Control device, robot and control method

1. A control device adapted to control a robot including a robot arm provided with a force detector, the control device comprising:

a processor that is configured to execute computer-executable instructions so as to control the robot,

wherein the processor is configured to:

operate the robot arm to move a screw gauge which is disposed on a tip side of the force detector of the robot arm, used for an inspection of a screw hole in a workpiece, and provided with an external thread, to make the external thread have contact with the screw hole;

detect force applied to the screw gauge in an x-axis direction and a y-axis direction using the force detector to perform force control in a direction perpendicular to a direction of an axis of the screw hole based on detection information of the force detector;

operate the robot arm to move the screw gauge in a direction so as to reduce the detected forces in the x-axis direction and the y-axis direction based on the force control to align the screw gauge with the screw hole;

when the screw gauge is aligned with the screw hole, store a z-axis position of a distal end of the screw gauge as an initial position, the initial position being at an entrance to the screw hole and aligned with a plan on a surface of the workpiece;

rotate the screw gauge and move the screw gauge from the initial position in a z-axis direction into the screw hole;

stop rotation of the screw gauge based on detection of a force in the z-axis direction by the force detector;

store the z-axis position of the distal end of the screw gauge as a stop position; and

determine a depth of the screw hole based on a difference between the initial position and the stop position.

2. The control device according to claim 1 , wherein

the processor is configured not to perform the force control in the direction perpendicular to the direction of the axis of the screw hole in at least a part of a zone when inserting the external thread into the screw hole after making the external thread have contact with the screw hole.

3. The control device according to claim 1 , wherein

the processor is configured to perform the force control in the direction perpendicular to the direction of the axis of the screw hole in at least a part of a zone when moving the external thread having been inserted into the screw hole toward an opposite direction to an insertion direction into the screw hole.

4. The control device according to claim 1 , wherein

the processor is configured to make a decision to pass or fail of the screw hole based on at least one of depth information of the screw hole, rotation information of the screw gauge, and detection information of the force detector.

5. The control device according to claim 4 , wherein

in the inspection of a GO aspect of the screw hole, a way of making the decision to pass or fail of the screw hole is different between a case in which the screw hole is a penetrating screw hole and a case in which the screw hole is a non-penetrating screw hole.

6. A robot comprising:

a robot arm provided with a force detector; and

a processor that is configured to execute computer-executable instructions so as to control the robot,

wherein the processor is configured to:

operate the robot arm to move a screw gauge which is disposed on a tip side of the force detector of the robot arm, used for an inspection of a screw hole in a workpiece, and provided with an external thread to make the external thread have contact with the screw hole;

detect force applied to the screw gauge in an x-axis direction and a y-axis direction using the force detector to perform force control in a direction perpendicular to a direction of an axis of the screw hole based on detection information of the force detector;

operate the robot arm to move the screw gauge in a direction so as to reduce the detected forces in the x-axis direction and the y-axis direction based on the force control to align the screw gauge with the screw hole;

when the screw gauge is aligned with the screw hole, store a z-axis position of a distal end of the screw gauge as an initial position, the initial position being at an entrance to the screw hole and aligned with a plane on a surface of the workpiece;

rotate the screw gauge and move the screw gauge from the initial position in a z-axis direction into the screw hole;

stop rotation of the screw gauge based on detection of a force in the z-axis direction by the force detector;

store the z-axis position of the distal end of the screw gauge as a stop position; and

determine a depth of the screw hole based on a difference between the initial position and the stop position.

7. The robot according to claim 6 , wherein

the processor is configured not to perform the force control in the direction perpendicular to the direction of the axis of the screw hole in at least a part of a zone when inserting the external thread into the screw hole after making the external thread have contact with the screw hole.

8. The robot according to claim 6 , wherein

the processor is configured to perform the force control in the direction perpendicular to the direction of the axis of the screw hole in at least a part of a zone when moving the external thread having been inserted into the screw hole toward an opposite direction to an insertion direction into the screw hole.

9. The robot according to claim 6 , wherein

the processor is configured to make a decision to pass or fail of the screw hole based on at least one of depth information of the screw hole, rotation information of the screw gauge, and detection information of the force detector.

10. The robot according to claim 9 , wherein

in the inspection of a GO aspect of the screw hole, a way of making the decision to pass or fail of the screw hole is different between a case in which the screw hole is a penetrating screw hole and a case in which the screw hole is a non-penetrating screw hole.

11. The robot according to claim 6 , wherein

the processor is configured to make the robot arm rotate the screw gauge in a case of rotating the screw gauge around the axis.

12. The robot according to claim 11 , wherein

the robot arm has a plurality of arms, and

the processor is configured to rotate the screw gauge attached to the force detector, the force detector being provided on a distal end of the plurality of arms of the robot arm.

13. The robot according to claim 12 , wherein

the screw gauge is overlapped with a rotational axis of the distal end of the plurality of arms of the robot arm when viewed from an axial direction of the rotational axis.

14. The robot according to claim 6 , wherein

the processor is configured to make a motor provided to the robot arm rotate the screw gauge in a case of rotating the screw gauge around the axis.

15. The robot according to claim 14 , wherein

the robot arm has a plurality of arms, and

the motor is disposed with an offset with respect to the force detector, the force detector being provided on a distal end of the plurality of arms of the robot arm.

16. A method of controlling a robot including a robot arm provided with a force detector, the method comprising:

operating the robot arm to move a screw gauge which is disposed on a tip side of the force detector of the robot arm, used for an inspection of a screw hole in a workpiece, and has an external thread, to make the external thread have contact with the screw hole;

detecting force applied to the screw gauge in an x-axis direction and a y-axis direction using the force detector to perform force control in a direction perpendicular to a direction of an axis of the screw hole based on detection information of the force detector, and operating the robot arm to move the screw gauge in a direction so as to reduce the detected forces in the x-axis direction and the y-axis direction based on the force control to align the screw gauge with the screw hole;

when the screw gauge is aligned with the screw hole, storing a z-axis position of a distal end of the screw gauge as an initial position, the initial position being at an entrance to the screw hole and aligned with a plane on a surface of the workpiece;

rotating the screw gauge and move the screw gauge from the initial position in a z-axis direction into the screw hole;

stopping rotation of the screw gauge based on detection of a force in the z-axis direction by the force detector;

storing the z-axis position of the distal end of the screw gauge as a stop position; and

determining a depth of the screw hole based on a difference between the initial position and the stop position.

17. A method of controlling a robot according claim 16 , comprising:

not performing the force control in the direction perpendicular to the direction of the axis of the screw hole in at least a part of a zone when inserting the external thread into the screw hole after making the external thread have contact with the screw hole.

18. The method of controlling a robot according claim 16 , comprising:

performing the force control in the direction perpendicular to the direction of the axis of the screw hole in at least a part of a zone when moving the external thread having been inserted into the screw hole toward an opposite direction to an insertion direction into the screw hole.

19. The method of controlling a robot according claim 16 , comprising:

making a decision to pass or fail of the screw hole based on at least one of depth information of the screw hole, rotation information of the screw gauge, and detection information of the force detector.

20. The method of controlling a robot according claim 19 , wherein

in the inspection of a GO aspect of the screw hole, a way of making the decision to pass or fail of the screw hole is different between a case in which the screw hole is a penetrating screw hole and a case in which the screw hole is a non-penetrating screw hole.