Patent Publication Number: US-9414734-B2

Title: Side brush assembly, robot cleaner and control method of robot cleaner

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the priority benefit of Korean Patent Application Nos. 10-2012-0095367 and 10-2012-0131379, filed on Aug. 30, 2012 and Nov. 20, 2012, respectively, in the Korean Intellectual Property Office, the disclosures of which are incorporated herein by reference. 
     BACKGROUND 
     1. Field 
     Embodiments relate to a side brush assembly including a side arm capable of being exposed outside a main body and returning inside the main body and a side brush unit mounted to the side arm, a robot cleaner and a control method of the robot cleaner. 
     2. Description of the Related Art 
     A robot cleaner is an appliance that moves by itself by virtue of an automatic travel function to clean a room or the like by sucking up foreign materials, such as dust, from a floor of the room without user intervention. The robot cleaner detects a distance up to an obstacle, such as furniture, office supplies, walls or the like, present in a zone to be cleaned using a distance sensor, and changes a traveling direction by selectively driving a left-wheel motor and a right-wheel motor to perform cleaning of the zone to be cleaned. 
     The robot cleaner includes a brush unit to sweep and collect dust. In order to increase a cleaning area, the robot cleaner further includes a side brush assembly. 
     SUMMARY 
     In an aspect of one or more embodiments, there is provided a side brush assembly equipped with a side arm configured to be exposed outside a main body and return inside the main body and a side brush unit mounted to the side arm, and capable of preventing the side brush unit from being damaged by obstacles. 
     In an aspect of one or more embodiments, there is provided a robot cleaner capable of sweeping dust gathering in corners using the side brush unit exposed outside the main body and reliably returning the side arm inside the main body, and a control method of the robot cleaner. 
     In an aspect of one or more embodiments, there is provided a robot cleaner which includes a main body a main body to remove dust from a floor while traveling on the floor, and at least one side brush assembly provided at the main body in order to increase a dust-removing area on the floor. The side brush assembly includes a side brush body defining an appearance of the side brush assembly, a side arm mounted to a bottom surface of the side brush body and configured to be exposed outside the main body, a side brush unit rotatably mounted to the side arm, a lever connected to the side arm and configured to rotate together with the side arm, a cam configured to rotate by receiving driving force from a driving motor, and an elastic member connecting the lever and the cam in order to rotate the lever by elastic force thereof. 
     The side brush body may be formed with a through-hole, through which a shaft is inserted. The shaft inserted through the through-hole may pass through the side brush body and the lever to connect the same. 
     The side brush body may be formed with a slit near the through-hole. 
     The lever may be provided with a guide pin, and the guide pin may move along the slit as the lever rotates. 
     When the cam rotates by the driving motor, the guide pin may move along the slit in a first direction by elastic force of the elastic member, and the side arm may be exposed outside the main body. 
     If external force is applied in a direction of returning the side arm inside the main body in a state of being exposed outside the main body, the guide pin may move along the slit in a second direction opposite to the first direction. If the external force is removed, the guide pin may move along the slit in the first direction by elastic force of the elastic member, and the side arm may be restored to the state of being exposed outside the main body. 
     If external force is applied in a direction of exposing the side arm outside the main body in a state of being held inside the main body, the guide pin may move along the slit in a first direction. If the external force is removed, the guide pin may move along the slit in a second direction opposite to the first direction by elastic force of the elastic member, and the side arm may be restored to the state of being held inside the main body. 
     The lever may be provided with a locking part which is configured as a protrusion extending outward from the lever. 
     The locking part may be configured to interfere with the cam in a state that the side arm is held inside the main body. Although external force is applied in a direction of exposing the side arm outside the main body, the lever may be prevented from rotating by interference of the locking part with the cam. 
     The guide pin may be integrally formed with the lever. 
     The side brush assembly may be removably mounted to a bottom surface of the main body. 
     The side brush body may be formed with a coupling hole, and the side brush body may be coupled to the main body by a coupling member which is inserted through the coupling hole and the bottom surface of the main body. 
     The side arm may be provided with a driving shaft which is mounted to the side brush unit, and a side brush driving motor to supply driving force to the driving shaft to rotate the same. 
     In an aspect of one or more embodiments, there is provided a side brush assembly which includes a side brush body formed with an accommodating part, a driving motor accommodated in the accommodating part, a cam configured to rotate by receiving driving force from the driving motor, a lever rotatably provided at the side brush body, an elastic member connecting the cam and the lever and configured to rotate the lever by being stretched by rotation of the cam or external force, a side arm configured to integrally rotate with the lever, and a side brush unit rotatably mounted to the side arm. 
     The side arm and the lever may be respectively fixed to both ends of a shaft which is inserted through the side brush body. 
     If external force is applied, the side arm may rotate in a first direction. If the external force is removed, the side arm may rotate in a second direction opposite to the first direction and may return to an original position. 
     The lever may be provided with a locking part which is configured as a protrusion extending from the lever. 
     If the driving motor is inactivated and the cam does not rotate, rotation of the lever and the side arm may be prevented due to interference of the locking part with the cam. 
     The side brush body may be formed with a slit, and the lever may be provided with a guide pin which is configured to be guided by the slit. 
     The side arm may be limited in rotation in at least one direction by a length of the slit. 
     In an aspect of one or more embodiments, there is provided a robot cleaner which includes a main body to remove dust from a floor while traveling on the floor, a side brush body provided in the main body and having an accommodating part, a driving motor accommodated in the accommodating part, a cam configured to rotate by receiving driving force from the driving motor, a pressing part mounted to the cam and configured to integrally move with the cam, a side arm configured to be exposed outside the main body or return inside the main body by rotation of the cam, a control unit to control operation of the driving motor, and a sensor mounted to the side brush body and configured to detect whether the side arm completely returns inside the main body. 
     The sensor may include a switch, and when the side arm completely returns inside the main body, the pressing part may press the switch. 
     If the pressing part presses the switch, the sensor may transmit information that the side arm completely returns inside the main body to the control unit. 
     The control unit may store the preset number of steps of the driving motor which operates to expose or return the side arm. 
     When the side arm returns inside the main body, if the switch is not pressed after the driving motor rotates the preset number of steps, the control unit may determine that the side arm interferes with obstacles. 
     In an aspect of one or more embodiments, there is provided a control method of a robot cleaner which includes driving a driving motor to rotate a side arm so that the side arm returns inside a main body, determining whether the driving motor is driven the preset number of steps, determining whether a switch is pressed by the side arm, determining whether a waiting time is over in an inactivated state of the driving motor, driving the driving motor to rotate the side arm so that the side arm returns inside the main body, and determining whether the switch is pressed. 
     The determining whether the switch is pressed by the side arm may include determining that the side arm completely returns inside the main body upon determining that the switch is pressed by the side arm, and terminating return operation of the side arm. 
     The determining whether the waiting time is over in an inactivated state of the driving motor may include removing obstacles interfering with the side arm by rotational or linear movement of the robot cleaner within the waiting time. 
     The driving the driving motor to rotate the side arm so that the side arm returns inside the main body and the determining whether the switch is pressed may be repeated upon determining that the switch is not pressed. 
     In an aspect of one or more embodiments, there is provided a control method of a robot cleaner which includes driving a driving motor to rotate a side arm so that the side arm is exposed outside a main body, determining whether the driving motor is driven the preset number of steps, and stopping driving of the driving motor. 
     As described above, since the side arm equipped with the side brush unit may be exposed outside the main body, a cleaning area may be widened. In addition, the side brush unit may be prevented from being damaged due to interference with external obstacles and being forcibly and unexpectedly exposed by external obstacles in the state of being held inside the main body. Further, the performance of detecting whether the side arm completely returns inside the main body may prevent an operational error that the return operation of the side arm is stopped before the side arm completely returns inside the main body. 
     In an aspect of one or more embodiments, there is provided a control method of a robot cleaner which includes driving a driving motor to rotate a motor shaft to rotate a side arm so that the side arm is returned inside a main body of the robot cleaner; determining whether the driving motor is driven a present number of steps in a direction of returning the side arm inside the main body of the robot cleaner; stopping driving of the driving motor after the driving motor is driven the preset number of steps; determining whether a switch is pressed; when the switch is not pressed, determining whether a wait time has expired; when the switch is not pressed and the wait time has expired, driving the driving motor to rotate the motor shaft by a preset unit angle in a direction of the returning side arm; and stopping the rotation of the motor shaft upon detection of the pressed switch. 
     In an aspect of one or more embodiments, there is provided a control method of a robot cleaner which includes driving a driving motor to rotate a side arm so that the side arm returns inside a main body; determining whether the driving motor is driven a preset number of steps; determining whether a switch is pressed by the side arm after the driving motor is driven the present number of steps; determining whether a waiting time is over in an inactivated state of the driving motor; driving the driving motor to rotate the side arm so that the side arm returns inside the main body when the switch is not pressed and the wait time has expired; and stopping the rotation of the side arm upon detection of the pressed switch. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and/or other aspects of embodiments will become apparent and more readily appreciated from the following description of embodiments, taken in conjunction with the accompanying drawings of which: 
         FIGS. 1 a  and 1 b    are perspective views illustrating a robot cleaner according to an embodiment; 
         FIGS. 2 a  and 2 b    are bottom views illustrating the robot cleaner according to an embodiment; 
         FIG. 3  is a view illustrating a side brush assembly of the robot cleaner according to an embodiment; 
         FIG. 4  is a perspective view illustrating a side brush assembly according to an embodiment; 
         FIG. 5  is an exploded perspective view of the side brush assembly according an embodiment; 
         FIG. 6  is a view illustrating the side brush assembly with a cover removed according to an embodiment; 
         FIGS. 7 through 10  are views illustrating operation of the side brush assembly according to an embodiment; 
         FIG. 11  is an exploded perspective view of a side brush assembly according an embodiment; 
         FIG. 12  is a view illustrating the side brush assembly with a cover removed according to an embodiment; 
         FIGS. 13 through 15  are views illustrating operation of the side brush assembly according to an embodiment; 
         FIG. 16  is a view illustrating a locked state of the side brush assembly according an embodiment; 
         FIG. 17  is a view illustrating the side brush assembly with a side arm exposed outside a main body according to an embodiment; 
         FIG. 18  is a view illustrating the side brush assembly with the side arm held inside the main body according to an embodiment; 
         FIG. 19  is a flowchart illustrating control of operation of exposing the side arm according to an embodiment; and 
         FIG. 20  is a flowchart illustrating control of operation of returning the side arm according to an embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. 
       FIGS. 1 a  and 1 b    are perspective views illustrating a robot cleaner according to an embodiment,  FIGS. 2 a  and 2 b    are bottom views illustrating the robot cleaner according to an embodiment, and  FIG. 3  is a view illustrating a side brush assembly of the robot cleaner according to an embodiment. 
     As shown in  FIGS. 1 a    through  3 , a robot cleaner  1  according to an embodiment includes a main body  2 , a power unit  3 , a driving wheel assembly  4 , a caster  5 , a main brush unit  6 , and a side brush assembly  10 . 
     The power unit  3  supplies driving power to drive the main body  2 . The power unit  3  includes a battery electrically connected to driving devices in order to supply driving power to the same to drive the main body  2  and components installed to the main body  2 . The battery may be configured as a secondary or rechargeable battery. If the main body  2  is connected to a docking station (not shown) after cleaning, the battery may be recharged at the docking station. 
     The driving wheel assembly  4  may be provided in a pair of assemblies which are disposed at a bottom surface of the main body  2  and are symmetrically arranged at a left middle area and a right middle area near an edge of the main body  2 . The driving wheel assembly  4  includes a driving wheel  40  enabling the main body  2  to move forward and backward and rotate during cleaning operation. The driving wheel assembly  4  may be modularized so as to be removably mounted to the bottom surface of the main body  2 . Therefore, if the driving wheel  40  needs repair or replacement due to breakdown or the like, only the driving wheel assembly  4  may be removed from the bottom surface of the main body  2  for repair or replacement without disassembling the main body  2 . The driving wheel assembly  4  may be mounted to the bottom surface of the main body  2  using hook engagement, screw engagement, tight-fitting engagement or the like. 
     On the basis of a traveling direction, the caster  5  is mounted to a front area near the edge of the bottom surface of the main body  2 . The caster  5  enables the main body  2  to maintain a stable posture. The caster  5  may be provided integrally with the driving wheel assembly  4  in a unitary assembly. 
     The main brush unit  6  is mounted to a suction port  62  formed at the bottom surface of the main body  2 . The main brush unit  6  includes a main brush  60  and a roller  61 . The main brush  60  is provided at an outer surface of the roller  61 . As the roller  61  rotates, the main brush  60  sweeps dust on a floor and guides the same toward the suction port  62 . The roller  61  may be configured as a rigid body, however, it is not limited to this configuration. The main brush  60  may be made of various materials having elasticity. 
     Although not illustrated in the drawings, a suction device is provided in the suction port  62  to generate suction force. Dust sucked into the suction port  62  moves toward a dust collecting device (not shown). 
     Sensors  20  and  21  may be mounted to the main body  2 . The sensors  20  and  21  may include a proximity sensor  20  and a vision sensor  21 . If the robot cleaner  1  arbitrarily travels without a preset traveling path under a cleaning system without a map, the robot cleaner  1  may travel on a zone to be cleaned using the proximity sensor  20 . If the robot cleaner  1  travels along a preset traveling path under a cleaning system with a map, the vision sensor  21  may receive position information of the robot cleaner  1  and generate a map. The vision sensor  21  is an exemplary embodiment of a position sensing system, and the position sensing system may be embodied by various other types of sensors. 
     A display unit  22  may be provided at a portion of the main body  2 . The display unit  22  may display states of the robot cleaner  1 , such as whether the battery is fully recharged or not, whether the dust collecting device is filled with dust or not, whether the robot cleaner  1  is in a cleaning mode or a sleep mode, and the like. 
     The side brush assembly  10  may be modularized so as to be removably mounted to the bottom surface of the main body  2 . Therefore, if the side brush assembly  10  needs repair or replacement due to breakdown or the like, only the side brush assembly  10  may be removed from the main body  2  for repair or replacement without disassembling the main body  2 . The side brush assembly  10  may be mounted to the bottom surface of the main body  2  using hook engagement, screw engagement, tight-fitting engagement or the like. The side brush assembly  10  may be provided in two or more separate assemblies which are disposed apart with a certain gap therebetween at the bottom surface of the main body  2 . 
     The side brush assembly  10  includes a side arm  13  and a side brush unit  14 . The side brush unit  14  may be mounted to the side arm  13 . The side arm  13  may be configured to be exposed outside the main body  2  and return inside the main body  2 . The side brush unit  14  includes a rotating shaft  140  and a side brush  141 . The side brush  141  rotates about the rotating shaft  140 , and sweeps dust on a floor, on which the robot cleaner  1  travels, toward the suction port  62 . 
     Constitution of the side brush assembly  10  will now be explained. 
       FIG. 4  is a perspective view illustrating a side brush assembly according to an embodiment,  FIG. 5  is an exploded perspective view of the side brush assembly according to an embodiment, and  FIG. 6  is a view illustrating the side brush assembly with a cover removed according to an embodiment. 
     Referring to  FIGS. 4 through 6 , a side brush assembly  10  according to an embodiment includes a side brush body  11 , a cover  12 , a side arm  13  and a side brush unit  14 . The side brush body  11  has an opened portion at an upper surface thereof, which may be shielded by the cover  12 . The side arm  13  may be mounted to the side brush body  11 , and the side brush unit  14  may be mounted to the side arm  13 . 
     The side brush body  11  is formed with an accommodating part  110 , which accommodates a side arm driving motor  180  therein. A cam  15 , a lever  16  and an elastic member  17  are mounted to the side brush body  11 . The cam  15 , the lever  16  and the elastic member  17  may be accommodated in the accommodating part  110  of the side brush body  11 . 
     The cam  15  is coupled to the side arm driving motor  180 . The side arm driving motor  180  may transmit driving force to the cam  15 , and the cam  15  may rotate clockwise or counterclockwise. 
     The lever  16  is mounted to the side brush body  11 , and is formed with a hole  160  through which a shaft  19  is inserted. The side brush body  11  is formed with a through-hole  113  corresponding to the hole  160  of the lever  16 . By the shaft  19  being inserted through the hole  160  and the through-hole  113 , the lever  16  may be rotatably mounted to the side brush body  11 . 
     The lever  16  may be provided with a guide pin  162 . The lever  16  may be formed with a guide pin insertion hole  161  through which the guide pin  162  is inserted. The guide pin  162  inserted through the guide pin insertion hole  161  extends downward from a bottom surface of the lever  16 . The guide pin  162  may be formed integrally with the lever  16 . 
     The side brush body  11  may be formed with a slit  111 . The guide pin  162  is inserted through the slit  111 , and moves along the slit  111 . The slit  111  is located near the through-hole  113  so that the guide pin  162  inserted through the slit  111  may move along the slit  111  when the lever  16  rotates about the shaft  19 . A radius of rotation of the side arm  13  may be set in accordance with a length of the slit  111 . That is, the side arm  13  may be limited in rotation in at least one direction by the length of the slit  111 . 
     A coupling hole  112  is formed at a portion of the side brush body  11 . The side brush body  11  may be coupled to the main body  2  by a coupling member (not shown) which is inserted through the coupling hole  112  and the main body  2 . In detail, a coupling part provided with a thread, through which the coupling member is engaged, is formed at the bottom surface of the main body  2 . The coupling member is engaged through both the coupling hole  112  of the side brush body  11  and the coupling part of the main body  2 , to thereby couple the side brush assembly  10  to the bottom surface of the main body  2 . The coupling between the side brush body  11  and the main body  2  is not limited to this configuration, and may be achieved by various other methods, such as hook engagement or the like. The side brush assembly  10  may be separated from the main body  2  only by releasing the coupling member coupling the side brush body  11  to the main body  2  or releasing the hook engagement of the side brush body  11 , without disassembling the main body  2 . 
     The side arm  13  is mounted to a bottom surface of the side brush body  11 . The side arm  13  includes a side arm body  130  and a side arm cover  131 . The side brush unit  14  is mounted to a bottom surface of the side arm body  130 . 
     The side arm body  130  and the side arm cover  131  are formed with holes  132  and  133 , respectively, which are located corresponding to each other. The shaft  19  may be inserted through the hole  132  of the side arm body  130  and the hole  133  of the side arm cover  131 . Accordingly, the shaft  19  may pass through the holes  132  and  133  of the side arm  13 , the through-hole  113  of the side brush body  11 , and the hole  160  of the lever  16 . The shaft  19  may be fixed to the side arm  13  and the lever  16  so that the side arm  13  and the lever  16  may integrally move. For example, the shaft  19  may be provided with a thread at an outer side surface thereof, and the holes  132  and  133  of the side arm  13  or the hole  160  of the lever  16  may be provided with a thread at an inner side surface thereof, with which the thread of the shaft  19  may be engaged. Alternatively, both ends of the shaft  19  may be fixed by a coupling member. As a result, the lever  16  and the side arm  13  may integrally move. 
     The elastic member  17  connects the cam  15  and the lever  16 . An end of the elastic member  17  is coupled to a portion of the cam  15 , and the other end of the elastic member  17  is coupled to a portion of the lever  16 . According to movement of the cam  15  and the side arm  13 , the elastic member  17  transmits elastic force to the lever  16 . The elastic member  17  may be stretched by rotation of the cam  15  or rotation of the side arm  13  by external force exerted on the side arm  13 . If external force exerted on the side arm  13  is removed, the side arm  13  may return to an original position thereof by elastic restoring force of the elastic member  17 . Detailed explanation related to this operation will be described later. On the basis of the position of the hole  160  of the lever  16 , the elastic member  17  is coupled to one side portion of the lever  16 , and the guide pin  162  is coupled to the opposite side of the lever  16 . 
     The side brush unit  14  includes a side brush mounting part  140  and a side brush  141 . The side brush  141  may be provided in plural separate brushes which are mounted to the side brush mounting part  140 . The side brush mounting part  140  is formed with a driving shaft insertion hole  142 . 
     The side arm body  130  is formed with a hole  134  corresponding to the driving shaft insertion hole  142  of the side brush mounting part  140 . A driving shaft  143  is inserted through the hole  134  of the side arm body  130  and the driving shaft insertion hole  142  of the side brush mounting part  140 . The driving shaft  143  is provided with a thread at a lower outer circumferential surface thereof, and the driving shaft insertion hole  142  is provided with a thread at an inner side surface thereof so that the thread of the driving shaft  143  may be tooth-engaged with the thread of the driving shaft insertion hole  142 . 
     A gear part may be provided at an upper portion of the driving shaft  143 . A side brush driving motor  181  may be accommodated in the side arm body  130 . The gear part provided at the driving shaft  143  may be engaged with the side brush driving motor  181 . The driving shaft  143  may rotate by being driven by the side brush driving motor  181 . Accordingly, the side brush unit  14  may rotate by the side brush driving motor  181 . 
     Hereinafter, operation of the side brush assembly  10  according to an embodiment will be described. 
       FIGS. 7 through 10  are views illustrating operation of the side brush assembly according to an embodiment. 
       FIG. 7  is a view illustrating the side brush assembly  10  in an initial state, in which the driving motor  180  is inactivated and the side arm  13  is free from external force. If the driving motor  180  is driven and the cam  15  rotates clockwise (in a direction A), a distance between the portion of the lever  16  and the portion of the cam  15 , to which both ends of the elastic member  17  are respectively coupled, increases, and thus the elastic member  17  is stretched. Due to elastic restoring force of the elastic member  17 , as shown in  FIG. 8 , the opposite portion of the lever  16  to the elastic member  17  rotates clockwise (in a direction B) about the shaft  19 . The guide pin  162  provided at the opposite portion of the lever  16  moves along the slit  111  of the side brush body  11 . As the lever  16  rotates clockwise, the side arm  13  coupled to the lever  16  also rotates clockwise (in the direction B) and is exposed outside the main body  2 . When the guide pin  162  arrives at one end of the slit  111 , rotation of the side arm  13  stops and the elastic member  17  is restored to the initial state. 
     Accordingly, the side arm  13  may be exposed outside the main body  2  by the driving motor  180 . In such an exposed state of the side arm  13 , the side brush unit  14  rotates and sweeps dust around the main body  2  or dust gathering in the corners of the floor toward the suction port  62 . 
     As shown in  FIG. 9 , if external force due to contact with obstacles is applied to the side arm  13  in a direction C while the side arm  13  is in an exposed state by the driving motor  180 , the side arm  13  rotates counterclockwise (in a direction D) and returns inside the main body  2 . As the side arm  13  rotates counterclockwise (in the direction D), the lever  16  also rotates counterclockwise (in the direction D) about the shaft  19 . If the side arm  13  completely returns inside the main body  2 , the guide pin  162  may be positioned at the other end of the slit  111 . At this time, the distance between the portion of the lever  16  and the portion of the cam  15 , to which both ends of the elastic member  17  are respectively coupled, increases, and thus the elastic member  17  is stretched. If external force due to contact with obstacles is removed, the lever  16  rotates clockwise (in the direction B) by elastic restoring force of the elastic member  17 . As the lever  16  rotates clockwise (in the direction B), the side arm  13  also rotates clockwise (in the direction B), and is restored to the original state and exposed outside the main body  2  again. 
     In the initial state depicted in  FIG. 7 , if external force is applied to the side arm  13  in a direction E by which the side arm  13  is unexpectedly exposed outside the main body  2 , the side arm  13  rotates clockwise (in the direction B). As the side arm  13  rotates clockwise (in the direction B), the lever  16  also rotates clockwise (in the direction B). The guide pin  162  provided at the lever  16  may move to one end of the slit  111  along the same. At this time, the distance between the portion of the lever  16  and the portion of the cam  15 , to which both ends of the elastic member  17  are respectively coupled, increases, and thus the elastic member  17  is stretched. If external force in the direction E is removed, the lever  16  rotates counterclockwise (in the direction D) by elastic restoring force of the elastic member  17 . As the lever  16  rotates counterclockwise (in the direction D), the side arm  13  also rotates counterclockwise (in the direction D), and returns inside the main body  2 . As a result, the side arm  13  may be restored to the initial state. 
     As described above, although interference with obstacles occurs, the side arm  13  may return to an original position thereof by elastic force of the elastic member  17  immediately when external force is removed. 
       FIG. 11  is an exploded perspective view of a side brush assembly according to an embodiment, and  FIG. 12  is a view illustrating the side brush assembly with a cover removed according to an embodiment. 
     Referring to  FIGS. 11 and 12 , a side brush assembly  10  according to an embodiment includes a side brush body  11 , a cover  12 , a side arm  13  and a side brush unit  14 . The side brush body  11  has an opened portion at an upper surface thereof, which may be shielded by the cover  12 . The side arm  13  may be mounted to the side brush body  11 , and the side brush unit  14  may be mounted to the side arm  13 . 
     The side brush body  11  is formed with an accommodating part  110 , which accommodates a side arm driving motor  180  therein. A cam  15 , a lever  16  and an elastic member  17  are mounted to the side brush body  11 . The cam  15 , the lever  16  and the elastic member  17  may be accommodated in the accommodating part  110  of the side brush body  11 . 
     Constitution of the side brush body  11 , the cover  12 , the side arm  13  and the side brush unit  14  may be the same as that in the side brush assembly  10  according to an embodiment. Hereinafter, constitution of the lever  16  of the side brush assembly  10  according to an embodiment will be explained in detail. 
     The lever  16  according to an embodiment may be provided integrally with a guide pin  162 . The guide pin  162  may protrude from a bottom surface of the lever  16 . Similarly to the first embodiment, the guide pin  162  may be separately provided and coupled to the lever  16 . 
     The lever  16  may be provided with a locking part  163 . The locking part  163  may be configured as a protrusion extending outward from the lever  16 . While the side arm  13  is held inside the main body  2 , the locking part  163  may interfere with a portion of the cam  15 . So long as the driving motor  180  is inactivated and the cam  15  does not rotate in the initial state, the locking part  163  interferes with the cam  15 . Since the locking part  163  interferes with a portion of the cam  15  in the initial state in which the side arm  13  is held inside the main body  2 , the lever  16  may not rotate in spite of external force. Accordingly, the side arm  13  is kept in the initial state without being exposed outside the main body  2 . 
     Hereinafter, operation of the side brush assembly  10  according to an embodiment will be described. 
       FIGS. 13 through 15  are views illustrating operation of the side brush assembly according to an embodiment, and  FIG. 16  is a view illustrating a locked state of the side brush assembly according to an embodiment. 
       FIG. 13  is a view illustrating the side brush assembly  10  in the initial state, in which the driving motor  180  is inactivated and the side arm  13  is free from external force. In this embodiment, a state in which the guide pin  162  is located at the other end of the slit is defined as the initial state. 
     If the driving motor  180  is driven and the cam  15  rotates counterclockwise (in a direction F), the distance between the portion of the lever  16  and the portion of the cam  15 , to which both ends of the elastic member  17  are respectively coupled, increases, and thus the elastic member  17  is stretched. Due to elastic restoring force of the elastic member  17 , as shown in  FIG. 14 , the opposite portion of the lever  16  to the elastic member  17  rotates clockwise (in a direction B) about the shaft  19 . The guide pin  162  provided at the lever  16  moves along the slit  111  of the side brush body  11 . As the lever  16  rotates clockwise, the side arm  13  coupled to the lever  16  also rotates clockwise (in the direction B) and is exposed outside the main body  2 . When the guide pin  162  arrives at one end of the slit  111 , rotation of the side arm  13  stops. At this time, the distance between the portion of the lever  16  and the portion of the cam  15 , to which both ends of the elastic member  17  are respectively coupled, decreases to the distance of the initial state, and the elastic member  17  is restored to the initial state. 
     Accordingly, the side arm  13  may be exposed outside the main body  2  by the driving motor  180 . In such a state, the side brush unit  14  rotates and sweeps dust around the main body  2  or dust gathering in the corners of the floor toward the suction port  62 . 
     As shown in  FIG. 14 , if external force due to contact with obstacles is applied to the side arm  13  in a direction G while the side arm  13  is in an exposed state by the driving motor  180 , the side arm  13  rotates counterclockwise (in a direction D) and returns inside the main body  2 . As the side arm  13  rotates counterclockwise (in the direction D), the lever  16  also rotates counterclockwise (in the direction D) about the shaft  19 . When the side arm  13  completely returns inside the main body  2 , the guide pin  162  may be positioned at the other end of the slit  111 . At this time, the distance between the portion of the lever  16  and the portion of the cam  15 , to which both ends of the elastic member  17  are respectively coupled, increases, and thus the elastic member  17  is stretched. If external force in the direction G due to obstacles is removed, the lever  16  rotates clockwise (in the direction B) by elastic restoring force of the elastic member  17 . As the lever  16  rotates clockwise (in the direction B), the side arm  13  also rotates clockwise (in the direction B), and is restored to the original state and exposed outside the main body  2  again. 
     As shown in  FIGS. 13 and 16 , although external force is applied to the side arm  13  in the direction F in the initial state in which the side arm  13  is held inside the main body  2 , the lever  16  is locked and does not rotate. Accordingly, the side arm  13  is prevented from being exposed outside the main body  2  by external force in the direction F. 
     In detail, in the initial state, the locking part  163  protruding from the lever  16  interferes with a portion of the cam  15 . As long as the driving motor  180  is inactivated and the cam  15  does not rotate, the cam  15  maintains interference with the locking part  163 . The cam  15  maintains contact with an inner surface of the locking part  163 , in order to prevent the lever  16  from rotating clockwise (in the direction B) by movement of the guide pin  162  to one end of the slit  111  from the other end of the slit  111 . Accordingly, in the initial state, the side arm  13  may not be exposed outside the main body  2  in spite of external force in the direction F. 
     As described above, the side brush assembly according to one or more embodiments and the robot cleaner having the same may be capable of exposing the side arm equipped with the side brush unit outside and therefore increasing a cleaning area. In addition, the side arm may be protected from damage by obstacles. In addition, in the initial state in which the side arm is held inside the main body, the side arm may be prevented from being unexpectedly exposed outside the main body although external force is applied to the side arm. Further, since the side brush assembly is modularized, if the side brush unit or the side arm needs repair or replacement due to breakdown, only the side brush assembly may be removed from the main body for repair or replacement without disassembling the main body. 
       FIG. 17  is a view illustrating the side brush assembly with the side arm exposed outside the main body, and  FIG. 18  is a view illustrating the side brush assembly with the side arm held inside the main body. 
     Referring to  FIGS. 17 and 18 , the side brush assembly  10  may be provided with a pressing part  150  which may rotate together with the cam  15 . If the cam  15  rotates by the driving motor  180 , the pressing part  150  may rotate integrally with the cam  15 . For example, the pressing part  150  may be fixed to the cam  15  or may be formed integrally with the cam  15  by injection molding. Accordingly, when the cam  15  rotates by the driving motor  180 , the cam  15  and the pressing part  150  may rotate together. If the cam  15  rotates in the direction A by the driving motor  180 , the side arm  13  may return inside the main body  2 . At this time, the pressing part  150  also rotates with the cam  15  in the direction A. 
     The side brush assembly  10  may further include a sensor  183  equipped with a switch  182  which is configured to be pressed by the pressing part  150 . If the cam  15  and the pressing part  150  rotate together and the side arm  13  completely returns inside the main body  2 , the pressing part  150  may press the switch  182 . That is, in the initial state in which the driving motor  180  is inactivated and the side arm  13  is free from external force, the pressing part  150  keeps pressing the switch  182 . 
     If the pressing part  150  presses the switch  182 , electric current flows through the sensor  183 . If electric current flows through the sensor  183 , the sensor  183  may detect that the side arm  13  completely returns inside the main body  2 . That is, if the pressing part  150  presses the switch  182 , the sensor  183  may detect that the side arm  13  completely returns inside the main body  2 . The sensor  183  transmits the detected information that the side arm  13  completely returns inside the main body  2  to a control unit (not shown). 
     When the side arm  13  rotates by the driving motor  180  and is exposed outside the main body  2 , the pressing part  150  is separated from the switch  182 . If the cam  15  rotates in the direction A by the driving motor  180  and the side arm  13  completely returns inside the main body  2 , the pressing part  150  presses the switch  182 . If the switch  182  is pressed, electric current flows through the sensor  183 , and the sensor  183  transmits the detected information that the side arm  13  completely returns inside the main body  2  to the control unit (not shown). 
     Hereinafter, control of operation of exposing and returning the side arm  13  will be explained. 
       FIG. 19  is a flowchart illustrating control of operation of exposing the side arm according to an embodiment. 
     Referring to  FIG. 19 , in order to rotate the side arm  13  and expose the same outside the main body  2 , the control unit (not shown) drives the driving motor  180  at operation S 1 . The control unit drives the driving motor  180  to rotate the cam  15  in the direction A. By the cam  15  rotating in the direction A, the side arm  13  rotates to be exposed outside the main body  2 . 
     If the side arm  13  rotates to be exposed outside the main body  2 , the control unit determines whether the driving motor  180  is driven the preset number of steps at operation S 2 . Accordingly, the control unit may determine whether the side arm  13  rotates by a preset target angle. 
     The target angle may be an angle between a line connecting the shaft  19  and an end of the side arm  13  which is distal from the shaft  19  in the initial state of the side arm  13  and a line connecting the shaft  19  and an end of the side arm  13  which is distal from the shaft  19  when the side arm  13  rotates to be completely exposed outside the main body  2 . Depending on the shape of the main body  2 , the shape of the side brush assembly  10  or the shape of the side arm  13 , the target angle at which the side arm  13  is fully exposed may be preset. 
     The driving motor  180  may be configured as a step motor, a motor shaft of which uniformly rotates by a unit angle per step. The rotational unit angle per step may be changed depending on the number of pulses transmitted to the driving motor  180 . In the case of a step motor capable of rotating once every 200 pulses, a shaft of the driving motor  180  rotates by a unit angle of 1.8 degrees per step (360 degrees/200 pulses). Therefore, the rotation angle of the driving motor  180  may be controlled by the number of pulses transmitted to the same. 
     In order to rotate the side arm  13  by the target angle, the preset number of steps for rotation of a shaft of the driving motor  180  may be stored in the control unit. For example, the preset target angle of 100 degrees by which the side arm  13  rotates to be fully exposed and the preset number of steps for a 100-degree rotation of the side arm  13  may be stored in the control unit. In order to expose the side arm  13 , the control unit rotates the motor shaft of the driving motor  180  by the number of steps stored therein. If the driving motor  180  rotates the stored number of steps, the side arm  13  rotates by the target angle and is exposed outside the main body  2 . The cam  15  may rotate corresponding to rotation of the motor shaft. 
     When rotation of the driving motor  180  for each step is completed, it is determined whether the motor shaft of the driving motor  180  rotates the preset number of steps. That is, whenever the driving motor  180  rotates by each unit angle, the control unit determines whether the driving motor  180  is driven the preset number of steps. 
     If the motor shaft of the driving motor  180  rotates the preset number of steps and the side arm  13  rotates by the preset target angle, the control unit stops rotation of the side arm  13  at operation S 3 . That is, if the driving motor  180  rotates the preset number of steps so as to rotate the side arm  13  by the target angle, the control unit stops rotation of the side arm  13  by stopping rotation of the driving motor  180 . As a result, the side arm  13  is exposed outside the main body  2 . 
       FIG. 20  is a flowchart illustrating control of operation of returning the side arm according to an embodiment. 
     Referring to  FIG. 20 , in order to rotate the side arm  13  and return the same inside the main body  2 , the control unit (not shown) rotates the motor shaft of the driving motor  180  at operation S 10 . The control unit drives the driving motor  180  to rotate the cam  15  in the direction B. By the cam  15  rotating in the direction B, the side arm  13  rotates to return inside the main body  2 . 
     The control unit determines whether the motor shaft of the driving motor  180  rotates the preset number of steps at operation S 20 . Since the motor shaft of the driving motor  180  has rotated the preset number of steps when the side arm  13  is exposed outside the main body  2 , the motor shaft rotates the identical number of steps also when the side arm  13  returns inside the main body  2 . When the side arm  13  returns inside the main body  2 , the motor shaft rotates in an opposite direction to the rotating direction when the side arm  13  is exposed outside the main body  2 . Whenever the motor shaft rotates by each unit angle, the control unit determines whether the motor shaft of the driving motor  180  rotates the preset number of steps. 
     If it is determined that the motor shaft of the driving motor  180  has not rotated the preset number of steps, the control unit keeps driving the driving motor  180 . That is, if it is determined that the motor shaft of the driving motor  180  has not rotated the preset number of steps, the control unit further rotates the driving motor  180  by another unit angle, and determines again whether the motor shaft of the driving motor  180  rotates the preset number of steps. If it is determined that the motor shaft of the driving motor  180  has rotated the preset number of steps, the control unit stops activation of the driving motor  180  to stop rotation of the motor shaft at operation S 30 . 
     If rotation of the motor shaft stops, the control unit determines whether the switch  182  is pressed at operation S 40 . If the switch  182  is pressed, the sensor  183  detects that the side arm  13  completely returns inside the main body  2 . The sensor  183  transmits the detected information that the side arm  13  completely returns inside the main body  2  to the control unit. If the control unit receives the information that the switch  182  is pressed, the control unit stops rotation of the motor shaft and terminates the operation of returning the side arm  13 . 
     If it is determined that the switch  182  is not pressed, it may be determined that the side arm  13  does not completely return inside the main body  2 . That is, it may be determined that the side arm  13  does not completely return inside the main body  2  due to interference with external obstacles. 
     The control unit determines whether a waiting time is over in the inactivated state of the driving motor  180  at operation S 50 . Here, the waiting time is defined as a time necessary to remove external obstacles interfering with the side arm  13 . The waiting time may be preset and stored in the control unit. For example, the waiting time may be preset to 30 seconds. If it is determined that the switch  182  is not pressed, the control unit determines whether the waiting time of 30 seconds is over. A user may remove obstacles interfering with the side arm  13  within the waiting time. A robot cleaner  1  may also remove obstacles blocking return of the side arm  13  within the waiting time by specific operation. For example, when the side arm  13  cannot completely return inside the main body  2 , the robot cleaner  1  may perform rotational movement or linear movement during the waiting time, to thereby remove obstacles blocking return of the side arm  13 . 
     In the inactivated state of the driving motor  180 , if the waiting time is over, the control unit drives the driving motor  180  and rotates the motor shaft by the preset unit angle in the direction of returning the side arm  13  at operation S 60 . If the motor shaft rotates by the unit angle, the control unit determines whether the switch  182  is pressed at operation S 70 . If it is determined that the switch  182  is not pressed, the control unit drives the driving motor  180  and further rotates the motor shaft by another unit angle. If it is determined that the switch  182  is pressed, the sensor  183  transmits the information that the side arm  13  completely returns inside the main body  2  and the switch  182  is pressed to the control unit, and the control unit terminates the operation of returning the side arm  13 . 
     After the waiting time is over, if the switch  182  is not pressed although the driving motor  180  has rotated the preset number of steps, additional waiting time may be provided. If a user removes obstacles or the robot cleaner  1  removes obstacles by specific operation within the waiting time, the control unit may drive the driving motor  180  until the switch  182  is pressed. 
     As is apparent from the above description, the side arm  13  equipped with the side brush unit  14  is exposed outside the main body  2 , and cleans corners and spaces between obstacles. The side brush unit is prevented from being damaged due to interference with external obstacles and being forcibly and unexpectedly exposed by external obstacles in the state of being held inside the main body  2 . Also, the side arm  13  may return inside the main body  2 , and it may be detected whether the side arm  13  completely returns depending on whether the switch  182  is pressed or not. When the side arm  13  cannot completely return inside the main body  2  due to interference with obstacles, a user may remove the obstacles or the robot cleaner  1  may remove the obstacles blocking return of the side arm  13  by rotational or linear movement within the waiting time. As a result, the side arm  13  may completely return inside the main body  2  with reliability. 
     Although a few embodiments have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the disclosure, the scope of which is defined in the claims and their equivalents.