Control apparatus, control method, and computer-readable storage medium storing a control program

1. A control apparatus for controlling a motion of a robot device, the robot device comprising a suction head to pick up a workpiece using compressed air and a pressure sensor to detect pressure of the compressed air, the control apparatus comprising a processor configured with a program to perform operations comprising:

operation as a movement controller configured to cause the robot device to move the suction head to a predetermined position at which the workpiece is fed;

operation as a suction controller configured to cause the robot device to attempt to pick up the workpiece with the suction head at the predetermined position;

operation as a determiner configured to determine whether the suction head has picked up the workpiece in the attempt based on a detection result of the pressure of the compressed air from the pressure sensor;

operation as a searcher configured to cause, in response to determination that the suction head has yet to pick up the workpiece, the robot device to rotationally move the suction head spirally in a horizontal direction while causing the suction head to perform a suction operation for the workpiece using the compressed air; and

operation as an estimator configured to estimate a direction in which the workpiece is located with respect to the predetermined position based on a change in the pressure of the compressed air detected by the pressure sensor during the rotational movement of the suction head,

wherein the processor is configured with the program to perform operations such that

in response to the determination that the suction head has yet to pick up the workpiece, operation as the movement controller comprises causing the robot device to further move the suction head in the estimated direction, and

after the suction head is further moved in the estimated direction, operation as the suction controller comprises causing the robot device to reattempt to pick up the workpiece with the suction head.

2. The control apparatus according to claim 1 , wherein

the processor is configured with the program to perform operations such that

operation as the estimator further comprises estimating a distance between the predetermined position and a position of the workpiece based on a change in the pressure of the compressed air detected by the pressure sensor during the rotational movement of the suction head,

in response to the determination that the suction head has yet to pick up the workpiece, operation as the movement controller further comprises causing the robot device to further move the suction head in the estimated direction by the estimated distance, and

after the suction head is further moved in the estimated direction by the estimated distance, operation as the suction controller further comprises causing the robot device to reattempt to pick up the workpiece with the suction head.

3. The control apparatus according to claim 1 , wherein

the processor is configured with the program to perform operations such that operation as the estimator configured to estimate the direction in which the workpiece is located further comprises:

dividing a trajectory of the rotational movement into a plurality of sections about an axis of the rotational movement,

identifying, of the plurality of sections, a section with a highest pressure of the compressed air detected by the pressure sensor, and

using a direction in which the identified section is located with respect to the predetermined position as the direction in which the workpiece is located.

4. The control apparatus according to claim 3 , wherein

the processor is configured with the program to perform operations as the estimator such that identifying the section with the highest pressure of the compressed air comprises identifying a section comprising a detection point with a highest pressure of the compressed air detected by the pressure sensor.

5. The control apparatus according to claim 3 , wherein

the processor is configured with the program to perform operations as the estimator such that identifying the section with the highest pressure of the compressed air comprises

calculating an average of pressure values of the compressed air detected by the pressure sensor for each of the plurality of sections, and

identifying, of the plurality of sections, a section with a greatest calculated average of the pressure.

6. The control apparatus according to claim 3 , wherein

the spiral rotational movement comprises a plurality of turns each with a different diameter, and

the processor is configured with the program to perform operations such that

operation as the estimator further comprises estimating a distance between the predetermined position and a position of the workpiece based on comparison between pressure values of the compressed air detected by the pressure sensor in different turns of the plurality of turns in the identified section,

in response to the determination that the suction head has yet to pick up the workpiece, operation as the movement controller comprises causing the robot device to further move the suction head in the estimated direction by the estimated distance, and

after the suction head is further moved in the estimated direction by the estimated distance, operation as the suction controller comprises causing the robot device to reattempt to pick up the workpiece with the suction head.

7. The control apparatus according to claim 6 , wherein the processor is configured with the program to perform operations such that operation as the estimator comprising estimating the distance between the predetermined position and the position of the workpiece based on the comparison between the pressure values of the compressed air detected by the pressure sensor in the different turns of the plurality of turns in the identified section comprises

identifying, of the plurality of turns, a turn with a highest pressure of the compressed air detected by the pressure sensor in the identified section, and

estimating the distance between the predetermined position and the position of the workpiece based on the diameter of the identified turn.

8. The control apparatus according to claim 1 , wherein

the processor is configured with the program to perform operations such that operation as the estimator configured to estimate the direction in which the workpiece is located further comprises:

identifying a detection point with a highest pressure of the compressed air detected by the pressure sensor, and

using a direction in which the identified detection point is located with respect to the predetermined position as the direction in which the workpiece is located.

9. The control apparatus according to claim 8 , wherein

the spiral rotational movement comprises a plurality of turns each with a different diameter, and

the processor is configured with the program to perform operations such that

operation as the estimator further comprises estimating a distance between the predetermined position and a position of the workpiece based on a distance between the predetermined position and the identified detection point,

in response to the determination that the suction head has yet to pick up the workpiece, operation as the movement controller comprises causing the robot device to further move the suction head in the estimated direction by the estimated distance, and

after the suction head is further moved in the estimated direction by the estimated distance, operation as the suction controller comprises causing the robot device to reattempt to pick up the workpiece with the suction head.

10. The control apparatus according to claim 1 , wherein

the processor is configured with the program to perform operations further comprising operation as a calibrator configured to calibrate the detection result of the pressure of the compressed air from the pressure sensor, and

the processor is configured with the program such that

operation as the searcher comprises causing the robot device to further displace the suction head vertically while causing the suction head to rotationally move spirally in the horizontal direction,

operation as a calibrator configured to calibrate the detection result comprises eliminating a difference between variations in pressure of the compressed air detected by the pressure sensor during the vertical displacement of the suction head and variations in pressure of the compressed air expected based on the vertical displacement of the suction head, and

operation as the estimator comprises using a calibrated result to estimate the direction in which the workpiece is located with respect to the predetermined position.

11. The control apparatus according to claim 1 , wherein

the workpiece comprises a screw, and

the robot device further comprises a screwdriver to rotate the screw sucked to the suction head about an axis of the screw.

12. The control apparatus according to claim 4 , wherein

the spiral rotational movement comprises a plurality of turns each with a different diameter, and

the processor is configured with the program to perform operations such that

operation as the estimator further comprises estimating a distance between the predetermined position and a position of the workpiece based on comparison between pressure values of the compressed air detected by the pressure sensor in different turns of the plurality of turns in the identified section,

in response to the determination that the suction head has yet to pick up the workpiece, operation as the movement controller comprises causing the robot device to further move the suction head in the estimated direction by the estimated distance, and

after the suction head is further moved in the estimated direction by the estimated distance, operation as the suction controller comprises causing the robot device to reattempt to pick up the workpiece with the suction head.

13. The control apparatus according to claim 5 , wherein

the spiral rotational movement comprises a plurality of turns each with a different diameter, and

the processor is configured with the program to perform operations such that

operation as the estimator further comprises estimating a distance between the predetermined position and a position of the workpiece based on comparison between pressure values of the compressed air detected by the pressure sensor in different turns of the plurality of turns in the identified section,

in response to the determination that the suction head has yet to pick up the workpiece, operation as the movement controller comprises causing the robot device to further move the suction head in the estimated direction by the estimated distance, and

after the suction head is further moved in the estimated direction by the estimated distance, operation as the suction controller comprises causing the robot device to reattempt to pick up the workpiece with the suction head.

14. The control apparatus according to claim 2 , wherein the processor is configured with the program to perform operations further comprising operation as a calibrator configured to calibrate the detection result of the pressure of the compressed air from the pressure sensor, and

the processor is configured with the program such that

operation as the searcher comprises causing the robot device to further displace the suction head vertically while causing the suction head to rotationally move spirally in the horizontal direction,

operation as a calibrator configured to calibrate the detection result comprises eliminating a difference between variations in pressure of the compressed air detected by the pressure sensor during the vertical displacement of the suction head and variations in pressure of the compressed air expected based on the vertical displacement of the suction head, and

operation as the estimator comprises using a calibrated result to estimate the direction in which the workpiece is located with respect to the predetermined position.

15. The control apparatus according to claim 3 , wherein the processor is configured with the program to perform operations further comprising operation as a calibrator configured to calibrate the detection result of the pressure of the compressed air from the pressure sensor, and

the processor is configured with the program such that

operation as the searcher comprises causing the robot device to further displace the suction head vertically while causing the suction head to rotationally move spirally in the horizontal direction,

operation as a calibrator configured to calibrate the detection result comprises eliminating a difference between variations in pressure of the compressed air detected by the pressure sensor during the vertical displacement of the suction head and variations in pressure of the compressed air expected based on the vertical displacement of the suction head, and

operation as the estimator comprises using a calibrated result to estimate the direction in which the workpiece is located with respect to the predetermined position.

16. The control apparatus according to claim 4 , wherein the processor is configured with the program to perform operations further comprising operation as a calibrator configured to calibrate the detection result of the pressure of the compressed air from the pressure sensor, and

the processor is configured with the program such that

operation as the searcher comprises causing the robot device to further displace the suction head vertically while causing the suction head to rotationally move spirally in the horizontal direction,

operation as a calibrator configured to calibrate the detection result comprises eliminating a difference between variations in pressure of the compressed air detected by the pressure sensor during the vertical displacement of the suction head and variations in pressure of the compressed air expected based on the vertical displacement of the suction head, and

operation as the estimator comprises using a calibrated result to estimate the direction in which the workpiece is located with respect to the predetermined position.

17. The control apparatus according to claim 5 , wherein the processor is configured with the program to perform operations further comprising operation as a calibrator configured to calibrate the detection result of the pressure of the compressed air from the pressure sensor, and

the processor is configured with the program such that

operation as the searcher comprises causing the robot device to further displace the suction head vertically while causing the suction head to rotationally move spirally in the horizontal direction,

operation as a calibrator configured to calibrate the detection result comprises eliminating a difference between variations in pressure of the compressed air detected by the pressure sensor during the vertical displacement of the suction head and variations in pressure of the compressed air expected based on the vertical displacement of the suction head, and

operation as the estimator comprises using a calibrated result to estimate the direction in which the workpiece is located with respect to the predetermined position.

18. The control apparatus according to claim 6 , wherein the processor is configured with the program to perform operations further comprising operation as a calibrator configured to calibrate the detection result of the pressure of the compressed air from the pressure sensor, and

the processor is configured with the program such that

operation as the searcher comprises causing the robot device to further displace the suction head vertically while causing the suction head to rotationally move spirally in the horizontal direction,

operation as a calibrator configured to calibrate the detection result comprises eliminating a difference between variations in pressure of the compressed air detected by the pressure sensor during the vertical displacement of the suction head and variations in pressure of the compressed air expected based on the vertical displacement of the suction head, and

operation as the estimator comprises using a calibrated result to estimate the direction in which the workpiece is located with respect to the predetermined position.

19. A method for controlling a motion of a robot device, the robot device comprising a suction head to pick up a workpiece using compressed air and a pressure sensor to detect pressure of the compressed air, the method being implementable by a computer, the method comprising:

causing the robot device to move the suction head to a predetermined position at which the workpiece is fed;

causing the robot device to attempt to pick up the workpiece with the suction head at the predetermined position;

determining whether the suction head has picked up the workpiece in the attempt based on a detection result of the pressure of the compressed air from the pressure sensor;

in response to determination that the suction head has yet to pick up the workpiece,

causing the robot device to rotationally move the suction head spirally in a horizontal direction while causing the suction head to perform a suction operation for the workpiece using the compressed air;

estimating a direction in which the workpiece is located with respect to the predetermined position based on a change in the pressure of the compressed air detected by the pressure sensor during the rotational movement of the suction head;

causing the robot device to further move the suction head in the estimated direction; and

causing, after further moving the suction head in the estimated direction, the robot device to reattempt to pick up the workpiece with the suction head.

20. A non-transitory computer-readable storage medium storing a control program for controlling a motion of a robot device, the robot device comprising a suction head to pick up a workpiece using compressed air and a pressure sensor to detect pressure of the compressed air, the control program, when read and executed, causing a computer to perform operations comprising:

causing the robot device to move the suction head to a predetermined position at which the workpiece is fed;

causing the robot device to attempt to pick up the workpiece with the suction head at the predetermined position;

determining whether the suction head has picked up the workpiece in the attempt based on a detection result of the pressure of the compressed air from the pressure sensor;

in response to determination that the suction head has yet to pick up the workpiece,

causing the robot device to rotationally move the suction head spirally in a horizontal direction while causing the suction head to perform a suction operation for the workpiece using the compressed air;

estimating a direction in which the workpiece is located with respect to the predetermined position based on a change in the pressure of the compressed air detected by the pressure sensor during the rotational movement of the suction head;

causing the robot device to further move the suction head in the estimated direction; and

causing, after further moving the suction head in the estimated direction, the robot device to reattempt to pick up the workpiece with the suction head.