Holding device, robot, and robot system

1. A holding device that holds a workpiece having flexibility,

the holding device comprising:

a first holding mechanism that is movable by a moving mechanism and holds a first end portion of the workpiece in a length direction of the workpiece;

a second holding mechanism that is movable by the moving mechanism and holds the workpiece in cooperation with the first holding mechanism by holding a second end portion of the workpiece in the length direction of the workpiece;

a detector that detects a length of the workpiece in a held state where at least one of the first and second holding mechanisms holds the workpiece;

a storage that prestores a length of the workpiece in a reference state where the workpiece is not in a bent state; and

a controller that controls operations of the first and second holding mechanisms and the moving mechanism, wherein

the controller sets the workpiece to the reference state in such a manner that with the first and second holding mechanisms holding the workpiece, the moving mechanism moves at least one of the first and second holding mechanisms in the length direction based on the length, detected by the detector, of the workpiece in the held state and the length, prestored in the storage, of the workpiece in the reference state.

2. The holding device according to claim 1 , wherein:

the detector detects the length of the workpiece in the held state where the first and second holding mechanisms cooperate to hold the workpiece; and

the controller sets the workpiece to the reference state in such a manner that with the first and second holding mechanisms holding the workpiece, the moving mechanism positions at least one of the first and second holding mechanisms at a supply position of the workpiece and moves the other of the first and second holding mechanisms in the length direction of the workpiece based on the length of the workpiece in the held state and the length of the workpiece in the reference state.

3. The holding device according to claim 2 , further comprising:

a first shaft member including a first thickness-direction side at which the first holding mechanism is disposed;

a first sub-holding mechanism that is disposed at a second thickness-direction side of the first shaft member and holds the workpiece;

a first rotating shaft that rotates the first shaft member such that the first and second thickness-direction sides of the first shaft member are reversed;

a second shaft member including a first thickness-direction side at which the second holding mechanism is disposed;

a second sub-holding mechanism that is disposed at a second thickness-direction side of the second shaft member and holds the workpiece; and

a second rotating shaft that rotates the second shaft member such that the first and second thickness-direction sides of the second shaft member are reversed.

4. The holding device according to claim 1 , further comprising:

a third holding mechanism that is movable integrally with the first holding mechanism by the moving mechanism and holds the workpiece in cooperation with the first holding mechanism by holding the second end portion of the workpiece in the length direction; and

a fourth holding mechanism that is movable integrally with the second holding mechanism by the moving mechanism and holds the workpiece in cooperation with the second holding mechanism by holding the first end portion of the workpiece in the length direction, wherein:

the detector detects the length of the workpiece in the held state where the first and third holding mechanisms cooperate to hold the workpiece;

the controller controls operations of the first to fourth holding mechanisms and the moving mechanism to perform a work of handing over the workpiece, held by the first and third holding mechanisms, to the second and fourth holding mechanisms; and

the controller sets the workpiece to the reference state when performing the handing-over work in such a manner that

the first holding mechanism holding the first end portion of the workpiece in the length direction is opposed to the fourth holding mechanism in a thickness direction of the workpiece,

the third holding mechanism holding the second end portion of the workpiece in the length direction is opposed to the second holding mechanism in the thickness direction of the workpiece,

with the first holding mechanism holding the first end portion of the workpiece in the length direction, the second end portion of the workpiece in the length direction is then released from the third holding mechanism and held by the second holding mechanism,

at least one of the first and second holding mechanisms is then moved in the length direction based on the length of the workpiece in the held state and the length of the workpiece in the reference state, and

with the second holding mechanism holding the second end portion of the workpiece in the length direction, the first end portion of the workpiece in the length direction is then released from the first holding mechanism and held by the fourth holding mechanism.

5. The holding device according to claim 1 , wherein at least one of the first and second holding mechanisms holds the workpiece by sucking a surface of the workpiece with negative pressure.

6. A robot comprising:

the holding device according to claim 1 ;

a first robot arm including a tip at which the first holding mechanism is disposed, the first robot arm being a part of the moving mechanism; and

a second robot arm including a tip at which the second holding mechanism is disposed, the second robot arm being another part of the moving mechanism.

7. The robot according to claim 6 , wherein:

the detector includes

a sensor that detects, at a predetermined position, existence of at least two portions of the workpiece in the held state, the two portions being located away from each other in the length direction and

a deriving device that derives the length of the workpiece in the held state based on a detected value of the sensor; and

the sensor is disposed on at least one of the tips of the first and second robot arms.

8. The robot according to claim 7 , wherein:

a first straight line is defined at the predetermined position;

the deriving device further derives an angle between the workpiece in the held state and the first straight line based on the detected value of the sensor; and

when setting the workpiece to the reference state, the controller adjusts inclination of the workpiece based on the angle derived by the deriving device.

9. A robot system comprising:

the holding device according to claim 1 ; and

a robot at which a part of the holding device is disposed, wherein:

the robot includes

a first robot arm including a tip at which the first holding mechanism is disposed, the first robot arm being a part of the moving mechanism and

a second robot arm including a tip at which the second holding mechanism is disposed, the second robot arm being another part of the moving mechanism; and

at least a part of the detector is disposed separately from the robot.

10. The robot system according to claim 9 , wherein:

the detector includes

a sensor that detects, at a predetermined position, existence of at least two portions of the workpiece in the held state, the two portions being located away from each other in the length direction and

a deriving device that derives the length of the workpiece in the held state based on a detected value of the sensor; and

at least the sensor of the detector is disposed separately from the robot.

11. The robot system according to claim 10 , wherein:

a first straight line is defined at the predetermined position;

the deriving device further derives an angle between the workpiece in the held state and the first straight line based on the detected value of the sensor; and

when setting the workpiece to the reference state, the controller adjusts inclination of the workpiece based on the angle derived by the deriving device.