Cleaner

1. A cleaner comprising:

a first cleaning module comprising a left spin mop and a right spin mop configured to come into contact with a floor while rotating in a clockwise direction or in a counterclockwise direction when viewed from an upper side;

a second cleaning module configured to come into contact with the floor at a position spaced apart from the left spin mop and the right spin mop in a forward-and-backward direction, and comprising a rolling member configured to rotate about a rotation axis extending in a horizontal direction;

a body supported by the first cleaning module and the second cleaning module;

a water supply module configured to supply water to the first cleaning module and comprising a water tank disposed inside the body; and

a controller configured to control autonomous travel of the cleaner,

wherein the body is configured to move by rotation of at least one of the left spin mop, the right spin mop, or the rolling member without a separate driving wheel,

wherein, in order for the body to move straight forward, the left spin mop and the right spin mop are controlled to rotate to generate a forward-movement frictional force while the rolling member is controlled to rotate in a counterclockwise rotation direction when viewed from the right side to generate a backward-movement frictional force, and

wherein, in order for the body to stay in place, the left spin mop and the right spin mop are controlled to rotate to generate a forward-movement frictional force while the rolling member is controlled to rotate in a counterclockwise rotation direction when viewed from the right side to generate a backward-movement frictional force.

2. The cleaner according to claim 1 , wherein water supplied by the water supply module reaches the first cleaning module before reaching the floor.

3. The cleaner according to claim 1 , wherein a direction in which the rolling member rotates is changeable.

4. The cleaner according to claim 1 , wherein the rolling member rotates about a rotation axis extending in a leftward-and-rightward direction.

5. The cleaner according to claim 4 ,

wherein a contact area between the rolling member and the floor overlaps an entire area of a gap between the rotation center of the left spin mop and the rotation center of the right spin mop when viewed from a front side.

6. The cleaner according to claim 5 , further comprising a battery for supplying power,

wherein the battery is disposed such that a center of gravity of the battery is located closer to a portion of the first cleaning module that contacts the floor than to a portion of the second cleaning module that contacts the floor in the forward-and-backward direction.

7. The cleaner according to claim 1 , wherein the rolling member comprises any one of a mop unit for mopping the floor and a brush for sweeping the floor.

8. The cleaner according to claim 1 , wherein a point on a bottom surface of the left spin mop that receives largest frictional force from the floor is located to a left of a rotation center of the left spin mop, and

wherein a point on a bottom surface of the right spin mop that receives largest frictional force from the floor is located to a right of a rotation center of the right spin mop.

9. The cleaner according to claim 1 , wherein the water supply module supplies water to the first cleaning module without supplying water to the second cleaning module, and

wherein each of the first cleaning module and the second cleaning module is configured to mop the floor.

10. The cleaner according to claim 1 , wherein the water tank is disposed such that a center of gravity of the water tank is located closer to a portion of the first cleaning module that contacts the floor than to a portion of the second cleaning module that contacts the floor in the forward-and-backward direction.

11. The cleaner according to claim 1 , further comprising an ultraviolet (UV) light-emitting diode configured to emit UV rays downwards and disposed between the first cleaning module and the second cleaning module.

12. The cleaner according to claim 1 , further comprising a sterilized-water-generating module configured to generate sterilized water via electrolysis of water inside the water tank.

13. The cleaner according to claim 1 , further comprising a sensing module comprising at least one of a bumper for sensing contact with an external obstacle, an obstacle sensor for sensing an external obstacle that is spaced apart from the cleaner, or a cliff sensor for sensing presence or absence of a cliff on a traveling surface,

wherein the controller is configured to receive a sensing signal from the sensing module and to control the autonomous travel.