Coupling device

1. A coupling device comprising:

a first connector that has a first connecting position rotatably supported by a first vertical shaft of a work vehicle that comprises an automatic drive controller;

a second connector that has a second connecting position rotatably supported by a second vertical shaft of a work device;

an actuator that changes at least one of the first and second connecting positions; and

a control device that:

estimates, with a position estimation model, a positional relationship between a travel line of the work vehicle and at least one of the first and second connecting positions, and

during an automatic drive control, controls the actuator independently of the automatic drive controller to change at least one of the first and second connecting positions based on the positional relationship.

2. The coupling device according to claim 1 , wherein the control device controls the actuator to change at least one of the first and second connecting positions to match the travel line.

3. The coupling device according to claim 1 , wherein the control device controls the actuator to change at least one of the first and second connecting positions based on a work-vehicle position of the work vehicle and the travel line.

4. The coupling device according to claim 3 , wherein when a deviation between the work-vehicle position and the travel line becomes equal to or larger than a threshold, the control device controls the actuator to change at least one of the first and second connecting positions in a direction of eliminating the deviation.

5. The coupling device according to claim 1 , wherein when a change of a posture of the work device becomes equal to or larger than a threshold during travel of the work vehicle, the control device controls the actuator to change at least one of the first and second connecting positions such that the posture falls within the threshold.

6. The coupling device according to claim 1 , wherein the control device controls the actuator to change at least one of the first and second connecting positions based on a travel history that includes a work-vehicle position of the work vehicle and a device position of the work device.

7. The coupling device according to claim 6 , wherein the control device:

calculates a trajectory of the device position based on the travel history,

controls the actuator to change at least one of the first and second connecting positions at a time of travel of the work vehicle such that at least one of the first and second connecting positions match the trajectory when determining that the trajectory is appropriate for a field, and

controls the actuator to change at least one of the first and second connecting positions at the time of travel of the work vehicle such that at least one of the first and second connecting positions differ from the trajectory when determining that the trajectory is inappropriate for the field.

8. The coupling device according to claim 1 , wherein the control device controls the actuator to change at least one of the first and second connecting positions based on an environment surrounding the work vehicle or the work device.

9. The coupling device according to claim 1 , wherein the control device estimates a work-vehicle position of the work vehicle based on the first connecting position.

10. The coupling device according to claim 1 , wherein the control device estimates a device position of the work device based on the second connecting position.

11. The coupling device according to claim 1 , further comprising:

a positioning device that positions at least one of the first and second connecting positions by a global positioning system.

12. A work vehicle comprising:

the coupling device according to claim 1 .

13. The work vehicle according to claim 12 , wherein

the work vehicle is a tractor, and

the coupling device couples to the work vehicle, as the work device, at least one of a trailer, a tilling device, a fertilizer spreading device, a transplanting device, a watering device, an agrochemical spreading device, a sowing spreading device, a reaping device, a dispersing device, a grass collecting device, a shaping device, and a composite device.