Patent Publication Number: US-2021161342-A1

Title: Robot cleaner

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority under 35 U.S.C. § 119 to Korean Application No. 10-2019-0156711 filed on Nov. 29, 2019, whose entire disclosure is hereby incorporated by reference. 
    
    
     BACKGROUND 
     1. Field 
     The present disclosure relates to a robot cleaner, and more particularly, to a robot cleaner capable of easily passing over an obstacle. 
     2. Background 
     Generally, a vacuum cleaner is an appliance that sucks air containing a foreign substance from outside by driving an air suction apparatus, which is disposed inside a cleaner main body to generate an air suction force, and separates and collects the foreign substance. The vacuum cleaner performing the above function is classified into a manual vacuum cleaner that is directly manipulated by a user and a robot cleaner that performs cleaning by itself without the user manipulation. A robot cleaner sucks various foreign substances lying on a face to be cleaned while autonomously travelling on the face-to-be cleaned. 
     According to U.S. Patent Application Publication No. US2014/0166375A, a technology in which a member that hits a floor face while a wheel rotates is included to pass over an obstacle is disclosed. However, according to the prior art, because the member only provides a certain trajectory when hitting the floor face, passable obstacles may be limited. Specifically, a robot cleaner according to the prior art may pass over a certain obstacle, but may often fail to pass over another obstacle. 
     The above reference is incorporated by reference herein where appropriate for appropriate teachings of additional or alternative details, features and/or technical background. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The embodiments will be described in detail with reference to the following drawings in which like reference numerals refer to like elements wherein: 
         FIG. 1  is a view illustrating a bottom face of a robot cleaner according to an embodiment of the present disclosure; 
         FIG. 2  is a view specifically illustrating a portion of  FIG. 1 ; 
         FIG. 3  is a control block diagram of an embodiment; 
         FIG. 4  is a view for illustrating main components in an embodiment; 
         FIG. 5  is an exploded perspective view of  FIG. 4 ; 
         FIG. 6  is a view illustrating a state in which a driving member assembly is rotating in a forward direction; and 
         FIG. 7  is a view illustrating a state in which a driving member assembly is rotating in a rearward direction. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, a preferred embodiment of the present disclosure that may specifically realize the above objects will be described with reference to the accompanying drawings. In this process, a size, a shape, or the like of a component shown in the drawings may be exaggerated for clarity and convenience of the description. In addition, terms specifically defined in consideration of a configuration and an operation of the present disclosure may vary depending on a user or an operator&#39;s intention or practice. Definitions of such terms should be made based on the contents throughout this specification. 
       FIG. 1  is a view illustrating a bottom face of a robot cleaner according to an embodiment of the present disclosure. Further,  FIG. 2  is a view specifically illustrating a portion of  FIG. 1 . Hereinafter, a description will be achieved with reference to  FIGS. 1 and 2 . An embodiment of the present disclosure includes a main body  10  for forming an exterior of the robot cleaner, a dust suction portion and dust storage installed in the main body  10 , and main wheels  40  for moving the main body  10 . 
     The dust suction portion may be installed inside the main body  10  to provide a suction force for sucking dust and the like from outside. The dust storage may be installed inside the main body  10  to provide therein a space in which a foreign substance such as the dust and the like sucked through the dust suction portion may be stored. When the foreign substance such as the dust and the like is accumulated in the dust storage, the user may remove the dust storage from the main body  10  to remove the foreign substance in the dust storage. 
     Main wheels  40  may be arranged beneath the main body  10  to move the main body  10  back and forth or to turn the main body  10 . In this connection, as the main wheels  40  are rotated, the main body  10  may change a direction or move forward or rearward. In this connection, the main wheels  40  are arranged on left and right sides of the main body  10  independently of each other. The main wheels  40  on the left and right sides may be driven independently of each other. In one example, the robot cleaner includes a front auxiliary wheel  20  for supporting one side of the main body  10  and assisting the movement of the main body  10  by the main wheels  40 . 
     A suction portion (or suction port)  14  may include an agitator disposed on the main body  10  and being brought into contact with a floor face on which cleaning is performed while rotating, a suction hole defined in the main body  10  and capable of sucking the external foreign substance by the suction force generated inside the main body  10 , and the like. 
     In one example, a rear auxiliary wheel  30  may be disposed rearward of the main wheels  40  to support the other side of the main body  10 . The front auxiliary wheel  20  and the rear auxiliary wheel  30  are arranged to be freely rotatable in a horizontal direction with respect to the main body  10 . In one example, the front auxiliary wheel  20  and the rear auxiliary wheel  30  are arranged to have fixed vertical levels with respect to the main body  10 . 
     In one example, although the main wheels  40  are not rotatable in the horizontal direction with respect to the main body  10 , the main wheels  40  are composed of two wheels on both sides and the wheels on the both sides rotate at different rotational speeds or in different directions, so that the main body  10  may turn left or right. In addition, the main wheels  40  may move in a vertical direction with respect to the main body  10  such that a vertical level of the main body  10  from the floor face varies. When the main wheels  40  descends toward the floor face, the vertical level of the main body  10  from the floor face may be increased. Further, when the main wheels  40  ascends from the floor face, the vertical level of the main body  10  from the floor face may be reduced. 
     In addition, the main wheels  40  are arranged on the both sides of the main body  10 , and vertical levels of the main wheels  40  may become different from each other. When the main body  10  travels on floor faces of a left floor face and a right floor face having different vertical levels or passes over an obstacle, a main wheel on a floor face with a lower vertical level may descend with respect to the main body, but a main wheel on a floor face with a higher vertical level may ascend with respect to the main body. As a result, a horizontal level of the main body  10  may be maintained when the robot cleaner passes the corresponding location. 
     A side brush assembly  100  is disposed on one side of the main body  10 . In the side brush assembly  100 , as a brush rotates, the brush moves an obstacle located away from a bottom of the main body  10  or an obstacle in contact with a wall to be sucked into the suction portion  14 . The side brush assembly  100  may be driven together with the suction portion  14  when the robot cleaner is driven. 
     A recess  60  in which a driving member assembly  200  is accommodated is defined in a bottom face of the main body  10 . The driving member assembly  200  may be exposed downward of the bottom face of the main body  10  while rotating forward or rearward of the main body  10 . In a state in which the driving member assembly  200  is not driven, the driving member assembly  200  is completely accommodated in the recess  60 , so that the driving member assembly  200  is not disposed lower than the bottom face of the main body  10 . Thus, a user is not able to view the driving member assembly  200  when viewing the main body  10  from the side. 
     The recess  60  may extend to have a length greater than that of the driving member assembly  200  such that the driving member assembly  200  may be accommodated in the recess  60  in both of situations where the rotation is stopped in a state in which the driving member assembly  200  is rotated forward and where the rotation is stopped in a state in which the driving member assembly  200  is rotated rearward. 
       FIG. 3  is a control block diagram of an embodiment. Referring to  FIG. 3 , in an embodiment, a sensor  310  for sensing rotation information of the main wheels  40  and a controller  300  for driving the driving member assembly  200  in response to a signal transmitted from the sensor  310  are included. 
     When it is determined that the driving member assembly  200  needs to be driven based on the signal transmitted from the sensor  310 , the controller  300  may drive a motor  210  of the driving member assembly  200 . When the controller  300  operates the motor  210 , the motor  210  may be repeatedly rotated clockwise or counterclockwise. In addition, the motor  210  may be rotated such that each rotation has a rotation angle of 180 degrees. The motor  210  has the rotation angle of 180 degrees when rotated clockwise and also has the rotation angle of 180 degrees when rotated counterclockwise. When it is determined that the driving member assembly  200  does not need to be driven based on the signal transmitted from the sensor  310 , the controller  300  does not drive the motor  210  of the driving member assembly  200 . 
     The controller  300  may drive the driving member assembly  200  when the numbers of rotations of the main wheels  40  arranged on the both sides of the main body  10  received from the sensor  310  are different. For example, when the main body  10  encounters the obstacle and is unable to move to a desired path and unable to escape from a certain location, the numbers of rotations of the two main wheels  40  arranged on the left and right sides may be different. In this connection, the controller  300  may operate the driving member assembly  200  to induce the robot cleaner to escape the obstacle. 
     The controller  300  may drive the driving member assembly  200  when the sensor  310  senses that a slip has occurred on one of the main wheels  40  arranged on the both sides of the main body  10 . Each main wheel  40  receives a rotational force from an individual motor. When a difference between a travel distance of the main body  10  and the number of rotations transmitted from the motor is equal to or greater than a predetermined value, it may be seen that the slip has occurred on the corresponding main wheel. That is, it may be a situation where the wheel does not travel as much as desired on a desired path due to the slip. Such situation may be a situation where the main body  10  has encountered the obstacle and the wheel is caught by the obstacle. In this connection, the controller  300  may operate the driving member assembly  200  to induce the robot cleaner to escape the obstacle. 
       FIG. 4  is a view for illustrating main components in an embodiment. Further,  FIG. 5  is an exploded perspective view of  FIG. 4 . Referring to  FIGS. 4 and 5 , the driving member assembly  200  includes a motor  210  that provides a rotational force for forward and reverse rotation, and a link assembly rotated by the motor  210 . 
     In the motor  210 , the forward and reverse rotations are sequentially performed. Rotation angles of the forward and reverse rotations may be equally approximately 180 degrees. When the motor  210  is terminated after performing the forward rotation immediately before being driven, the motor  210  starts to be driven while performing the reverse rotation. On the other hand, when the motor  210  is terminated after performing the reverse rotation immediately before being driven, the motor  210  starts to be driven while performing the forward rotation. Then, when the motor  210  is driven, after performing the forward rotation by 180 degrees, the reverse rotation is started. In addition, after performing the reverse rotation by 180 degrees, the forward rotation is started. In such a manner, the rotations are alternately performed. 
     A gear  220  is formed on a rotation shaft  212  of the motor  210 . Teeth are formed on the gear  220 . The gear  220  transmits a rotation provided from the rotation shaft  212  of the motor  210  to the link assembly as it is. The link assembly includes a first link  260  and a second link  280  that are engaged with the gear  220  and rotated. The link assembly may be composed of two links rotatable to each other. 
     The first link  260  is equipped with a gear having teeth that are engaged with the teeth of the gear  220  at one end thereof. Thus, when the gear  220  is rotated, the first link  260  is rotated together. In this connection, a radius, a thickness of a tooth, and a spacing between two teeth of the gear  220  are the same as those of the gear of the first link  260  such that a rotation angle of the gear  220  may be transmitted to the first link  260  as it is. That is, when the gear  220  rotates 180 degrees in the forward direction, the first link  260  rotates 180 degrees in the reverse direction. On the other hand, when the gear  220  rotates 180 degrees in the reverse direction, the first link  260  rotates 180 degrees in the forward direction. 
     A through-hole  268  through which a rotation shaft  262  passes is defined in the first link  260  at an opposite side of a portion where the gear is formed. In addition, a through-hole  282  through which the rotation shaft  262  passes is also defined in the second link  280 . One rotation shaft  262  penetrates both the through-hole of the first link  260  and the through-hole of the second link  280 , so that the first link  260  and the second link  280  are rotatable with respect to each other. 
     One end of the first link  260  has an empty space defined at a central portion thereof and includes flanges respectively extending at both sides. The through-hole  268  is defined in the flanges. The second link  280  is inserted between the two flanges, and a portion where the first link  260  and the second link  280  overlap is present. In the corresponding portion, the rotation shaft  262  penetrates the two links. 
     Guide grooves  284  are defined at one end of the second link  280 . The guide grooves  284  are defined to have a size less than a size of a central portion of the second link  280 . The guide grooves  284  are respectively defined in a front face and a rear face of the second link  280 . In this connection, the front face is a face directed in a front direction when the link assembly starts to rotate forward from a state of being folded in the recess  60 . The rear face is a face directed in a rear direction when the link assembly starts to rotate rearward from the state of being folded in the recess  60 . 
     A cover  290  made of a rubber material is disposed on the guide grooves  284 . The cover  290  may be formed in a substantially ‘U’ shape and may be coupled to the guide grooves  284  while being in contact with total three faces of the guide grooves  284 . The cover  290  is disposed to surround the front face and a rear face of one end of the second link  280 , so that the second link  280  may always be in contact with the floor while being rotated forward and rearward. The cover  290  is made of the rubber material, so that the cover  290  may have high friction with respect to the floor face. That is, the cover  290  is made of a material that is easily deformed compared to the first link  260  and the second link  280 , so that damage to the floor face occurring when the driving member assembly hits the floor may be prevented. 
     A stopper (or stopper surface)  274  and a guide (or guide surface)  270  are formed on both sides of the first link  260  around the through-hole  268  into which the rotation shaft  262  is coupled, and a combination of these components may be referred to as a hinge or joint. The stopper  274  limits a direction in which the second link  280  is rotated. The stopper  274  may be of a square shape having a right angle around the rotation shaft  262 . 
     The second link  280  includes a body extending from a portion where the through-hole  282  is defined. The body is a portion with a thickness greater than that of the portion where the through-hole  282  is defined, and extends from a portion where a step  281  is formed. That is, the portion where the through-hole  282  is defined is inserted between the flanges of the first link  260  and coupled to the flanges of the first link  260 . On the other hand, the body includes the step  281 , and thus, is not able to be inserted between the flanges. Thus, the second link  280  may no longer rotate while the step  281  is in contact with the stopper  274 . The stopper  274  may prevent the second link  280  from being folded toward the first link  260  when the second link  280  is rotated forward of the main body. The step  281  is formed perpendicular to a direction in which the first link  260  and the second link  280  are unfolded and coupled to each other. 
     The guide  270  is formed to be curved around the rotation shaft  262  such that the second link  280  is rotated along an outer circumferential face of the guide  270 . When the second link  280  is rotated around the rotation shaft  262 , the first link  260  may be folded toward the second link  280 . The guide  270  may form an arc shape having the same radius around the rotation shaft  262 . Thus, even when the second link  280  is rotated around the rotation shaft  262 , the step  281  is not brought into contact with the guide  270 . Thus, the second link  280  may be folded toward the first link  260 . The guide  270  may induce the second link  280  to be folded toward the first link  260  when the second link  280  is rotated rearward of the main body. 
     A spring  278  for providing a restoring force to return to the second link  280  to a location where the first link  260  and the second link  280  are arranged in parallel when the second link  280  is rotated around the rotation shaft  262  is included. The spring  278  has one end fixed to the first link  260  and the other end fixed to the second link  280 . 
     In a situation in which the second link  280  is folded with respect to the first link  260  when the link assembly is rotated rearward of the main body  10 , the spring  278  guides the second link  280  to be unfolded with respect to the first link  260  when an external force is removed. When the first link  260  and the second link  280  are folded, the spring  278  is compressed. When the second link  280  is not in contact with the floor, the external force applied to the second link  280  is removed. Thus, the first link  260  and the second link  280  may be unfolded by the restoring force of the spring  278 . 
       FIG. 6  is a view illustrating a state in which a driving member assembly is rotating in a forward direction. Further,  FIG. 7  is a view illustrating a state in which a driving member assembly is rotating in a rearward direction. In  FIGS. 6 and 7 , a left direction means a front of the main body  10  and a right direction means a rear of the main body  10 . That is, when the main body  10  is moved forward, the main wheels  40  move the main body in the left direction in  FIGS. 6 and 7 . On the other hand, when the main body  10  is moved rearward, the main wheels  40  move the main body in the right direction in  FIGS. 6 and 7 . 
     There may be a case in which the main body  10  should climb an obstacle at a vertical level higher than that of a floor face previously traveled or pass over an obstacle at a vertical level lower than that of the floor face previously traveled while traveling. In addition, a situation in which the vertical level of the floor face increases and then decreases or decreases and then increases may occur despite a short travel distance when the robot cleaner encounters the obstacle. In a process in which the robot cleaner passes over the obstacle, a situation in which it is difficult for the robot cleaner to sufficiently escape from the obstacle using the rotational force provided from the main wheels  40  may occur. For example, a situation where the main wheel falls into a narrow gap or is stuck in a deep groove and is not sufficiently in contact with the floor may be considered. 
     When the sensor  310  obtains information about such situation using the rotation information of the main wheels  40 , the controller  300  may allow the driving member assembly  200  to be driven. When the motor  210  of the driving member assembly  200  is driven by the controller  300 , the link assembly  260  and  280  may rotate forward or rearward of the main body  10 . When the link assembly is rotated forward as in  FIG. 6 , the link assembly hits the floor in the state in which the first link  260  and the second link  280  are folded because the second link  280  is caught by the stopper  274  and is not able to be rotated. Thus, a radius at which the link assembly hits the floor may be kept constant at a length of the unfolded first link  260  and second link  280 . Even when the cover  290  is brought into contact with the floor face before the link assembly is rotated by 90 degrees with respect to the bottom face of the main body  10 , the second link  280  is rotated in an unfolded state. 
     Even when the rotation of the link assembly is made as shown in  FIG. 6 , when it is determined that the main body has not escaped the obstacle by the information obtained by the sensor  310  from the main wheels  40 , the controller  300  may rotate the link assembly again in an opposite direction. 
     The link assembly is rotated rearward of the main body  10  as shown in  FIG. 7 . In this connection, the link assembly may hit the floor face before the second link  280  is rotated by 90 degrees perpendicular to the bottom face of the main body  10 . In one example, the cover  290  first comes into contact with the floor face. Because there is a load of the main body  10 , the first link  260  and the second link  280  may be folded as the second link  280  is rotated relative to the rotation shaft  262 . In this connection, an angle at which the second link  280  is folded to the first link  260  may be changed based on characteristics of the floor face on which the main body  10  is located or the vertical level of the floor face. 
     That is, in the present embodiment, the driving member assembly  200  has different hitting radii when rotating forward and when rotating rearward. When the link assembly is rotated forward of the main body, the hitting radius is constant in the state in which the first link  260  and the second link  280  are unfolded. On the other hand, when the link assembly is rotated rearward of the main body, the hitting radius may vary because the second link  280  is folded variously with respect to the first link  260 . When the link assembly is rotated forward, the hitting radius may be larger than that when rotated rearward. 
     In the present embodiment, because one driving member assembly may vary the hitting radius when hitting the floor, various types of motions may be generated when the movement of the main body to the obstacle is restricted. While the driving member assembly is rotated alternately forward and rearward, the main body may escape from the obstacle and the main body may move to a desired location. 
     Referring to  FIG. 3 , the recess  60  provides therein the space in which the first link  260  and the second link  280  are able to be accommodated while being unfolded. The recess  60  is extended in the front and rear directions of the main body  10  such that the first link  260  and the second link  280  may be accommodated therein in both of a case in which the driving of the motor  210  is terminated in the state in which the first link  260  and the second link  280  are rotated forward and a case in which the driving of the motor  210  is terminated in the state in which the first link  260  and the second link  280  are rotated rearward. That is, the recess  60  may be extended to have a length about twice the length of the unfolded first link  260  and second link  280 . In addition, a width of the recess  60  is greater than widths of the first link  260  and the second link  280 , so that the first link  260  and the second link  280  may be inserted into the recess  60  without friction. 
     The present disclosure is to provide a robot cleaner capable of stably passing over an obstacle. In addition, the present disclosure is to provide a robot cleaner that may prevent travel thereof from being interrupted resulted from being caught by obstacles of various shapes. 
     A spring applied for a suspension function of main wheels in a general robot cleaner has a linearity for a displacement and a load. In a state in which the main wheels are withdrawn on a floor, a spring restoring force becomes significantly reduced by an extended stroke and does not exert a sufficient ground reaction force (a normal force). Thus, a sufficient frictional force is not able to be provided to the main wheels, which causes the main wheels to idle. In order to solve such problem, the present disclosure provides a technology in which a link assembly having a length larger than a reachable range of the main wheels is disposed to allow the robot cleaner to escape from an obstacle. 
     The present disclosure includes a rotating motor and a link assembly operated by the motor. In this connection, a sensor may be included to determine a time point for driving the motor. The sensor may transmit information about a rotation of the main wheels to a controller, and the controller may determine a rotation time point of the link assembly. 
     The present disclosure includes a main body including a suction portion disposed therein, a main wheel for moving the main body, wherein a vertical level of the main wheel varies in a vertical direction with respect to the main body, an auxiliary wheel disposed at a front portion or a rear portion of the main body, wherein a vertical level of the auxiliary wheel is fixed with respect to the main body, and a driving member assembly disposed in the main body, wherein the driving member assembly varies a vertical level of the main body from a floor face while rotating in forward and rearward directions of the main body. 
     The driving member assembly may include a motor for providing a rotational force and a link assembly rotated by the motor. While the link assembly is not in operation, the link assembly is accommodated in a recess defined in a bottom face of the main body, so that the link assembly is not exposed downward of the bottom face of the main body. Thus, when the main body is moved, the link assembly does not interfere with the movement of the main body. 
     The link assembly is composed of a first link and a second link. The second link is able to rotate in one direction with respect to the first link, but is not able to rotate in the other direction. For example, the second link is able to rotate clockwise with respect to a rotation shaft disposed on the first link, but is not able to rotate counterclockwise. Thus, when the link assembly is rotated with respect to the main body, radii at which the link assembly is able to hit the floor upon in contact with the floor are different when rotating clockwise and counterclockwise. Thus, different forms of operation are possible. Thus, the robot cleaner is able to escape from various obstacles, thereby improving a travel performance of the main body. 
     According to the present disclosure, the robot cleaner may stably pass over the obstacle. According to the present disclosure, cleaning may be performed while the travel of the robot cleaner is not interrupted by the obstacle. In particular, the member that hits the floor in various manners is included in addition to the wheel that moves the robot cleaner, so that the robot cleaner may easily pass over the obstacle while the obstacles of various shapes are placed below the main body. 
     In one example, a robot comprises: a main body; a main wheel that is driven to move the main body; and a link assembly coupled to the main body, wherein the link assembly is configured to raise the main body from a floor by a first height when pivoting in a first direction, and to raise the main body from the floor by second height that differs from the first height when pivoting in a second direction. 
     The robot may further comprise a motor to provide a force to pivot the link assembly in the first direction or the second direction. A recess for accommodating the link assembly therein may be defined in a bottom of the main body. 
     The link assembly may include: a first link pivot by the force of the motor; and a second link rotatably coupled to the first link. The first link may include: a rotation shaft provided to rotate the second link therearound; and a stopper surface provided at one end of the first link, wherein the stopper surface contacts a portion of the second link to limit a rotation of the second link relative to the first link. The stopper surface prevents the second link from being folded toward the first link when the second link is rotated in the first direction toward a front of the main body. 
     The link assembly may include a rotation shaft provided to rotate the second link therearound, the first link may include a guide surface, and the guide surface may be formed to be curved around the rotation shaft such that the second link is rotated along the guide surface. The guide surface may have an arc shape having a consistent radius around the rotation shaft. 
     The link assembly may include a spring that provides a restoring force to return to the second link to a location where the first link and the second link are arranged in parallel when the second link is rotated around the rotation shaft. A first end of the spring may be fixed to the first link and a second end of the spring is fixed to the second link. The link assembly may include a cover made of a rubber material and provided an end of the link assembly. 
     The main wheel may be a first main wheel provided on a first side of the main body, and the robot may further comprise: a second main wheel provided on a second side of the main body; a sensor configured to detect rotation information of the first and second main wheels; and a controller configured to manage the motor to selectively pivot the link assembly based on the rotation information of the first and second main wheels. 
     The controller may be configured to manage the motor to pivot the link assembly when the rotation information indicates that a numbers of rotations of the first main wheel during a time period differs from a numbers of rotations of the second main wheel during the time period. The controller may be configured to manage the motor to pivot the link assembly when the rotation information indicates that a slip has occurred on at least one of the first main wheel or the second main wheel. 
     The robot may be a robot cleaner, and main body may include a suction port. A vertical level of the main wheel may vary with respect to the main body. The robot may further comprise at least one auxiliary wheel provided at a front portion or a rear portion of the main body, wherein a vertical level of the auxiliary wheel may be fixed with respect to the main body 
     In another example, a robot may comprise: a main body; a motor; and a linkage coupled to the main body, the linkage including: a first link coupled to the main body, the first link pivoting in one of a first direction or a second direction based on a force from the motor to extend from a lower surface of the main body; a second link; and a hinge that connects the first and second links and is configured to not bend when the first link is pivoting in the first direction and to bend when the first link is pivoting in the second direction. 
     The robot may further comprise a sensor to detect whether a movement of the main body is obstructed by an obstacle, wherein the motor applies the force to the first link when the sensor detects that the movement of the main body is obstructed by the obstacle. 
     The motor may apply the force to cause the first link to pivot in the first direction when the sensor detects that the movement of the main body is obstructed by the obstacle, and the motor may apply the force to cause the first link to pivot in the second direction when the sensor detects that the movement of the main body continues to be obstructed by the obstacle after the first link pivots in a first direction. 
     It will be understood that when an element or layer is referred to as being “on” another element or layer, the element or layer can be directly on another element or layer or intervening elements or layers. In contrast, when an element is referred to as being “directly on” another element or layer, there are no intervening elements or layers present. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     It will be understood that, although the terms first, second, third, etc., may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another region, layer or section. Thus, a first element, component, region, layer or section could be termed a second element, component, region, layer or section without departing from the teachings of the present invention. 
     Spatially relative terms, such as “lower”, “upper” and the like, may be used herein for ease of description to describe the relationship of one element or feature to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation, in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “lower” relative to other elements or features would then be oriented “upper” relative to the other elements or features. Thus, the exemplary term “lower” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     Embodiments of the disclosure are described herein with reference to cross-section illustrations that are schematic illustrations of idealized embodiments (and intermediate structures) of the disclosure. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, embodiments of the disclosure should not be construed as limited to the particular shapes of regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
     Any reference in this specification to “one embodiment,” “an embodiment,” “example embodiment,” etc., means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with any embodiment, it is submitted that it is within the purview of one skilled in the art to effect such feature, structure, or characteristic in connection with other ones of the embodiments. 
     Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art.