Patent Publication Number: US-2019190301-A1

Title: Mobile body and mobile body system

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present disclosure relates to a mobile body and a mobile body system. 
     2. Description of the Related Art 
     For instance, Japanese Unexamined Patent Application Publication No. 2008-137451 relates to a system that performs non-contact power supply to an automatic guided vehicle. 
     When a mobile body such as an automatic guided vehicle receives power supply in accordance with a non-contact power supply method, the power supply is conducted by transmitting and receiving power between a power transmission resonator provided to a non-contact power supply device on a power transmission side and a power reception resonator provided to the mobile body on a power reception side. Here, when the power is transmitted and received between the power transmission resonator and the power reception resonator, power supply efficiency varies depending on relative positions and orientations between the power transmission resonator and the power reception resonator. Accordingly, depending on the relative positions and orientations between the power transmission resonator and the power reception resonator, that is, depending on the position and the orientation of the mobile body relative to those of the non-contact power supply device, the mobile body may face a difficulty in receiving the power supply efficiently. 
     SUMMARY OF THE INVENTION 
     An exemplary embodiment of the present disclosure provides a mobile body to be driven by power wirelessly transferred from a non-contact power supply device including a power transmission resonator that transmits the power in accordance with a non-contact power supply method. The mobile body includes a power reception resonator that receives the power transmitted from the power transmission resonator; a power storage that stores the power received by the power reception resonator; a motor to be operated by the power stored in the power storage; a controller configured or programmed to control drive of the motor; and at least two wheels to be driven independently of each other by the motor. The wheels include a first movement axis and a second movement axis with an axial orientation being different from an axial orientation of the first movement axis. The wheels move the mobile body along the first movement axis and the second movement axis. The wheels move on a floor surface. When the mobile body is located in a power supply target range, the controller controls the motor based on power reception status information indicating a status of power reception by the power reception resonator, and rotationally moves the mobile body based on a rotation axis being the center of rotational movement with which an angle of opposition of the power transmission resonator to the power reception resonator varies. 
     According to the exemplary embodiment of the present disclosure, a mobile body and a mobile body system, which enable the mobile body to move based on a status of power reception from a power transmission resonator. 
     The above and other elements, features, steps, characteristics and advantages of the present disclosure will become more apparent from the following detailed description of the preferred embodiments with reference to the attached drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram showing an example of a configuration of a mobile body system of an exemplary embodiment of the present disclosure. 
         FIG. 2  is a diagram showing an example of an external configuration of a mobile body of an exemplary embodiment of the present disclosure. 
         FIG. 3  is a diagram showing an example of functional configurations of a non-contact power supply device and a mobile body of an exemplary embodiment of the present disclosure. 
         FIG. 4  is a diagram showing an example of a layout relation between a power transmission resonator and a power reception resonator of an exemplary embodiment of the present disclosure. 
         FIG. 5  is a diagram showing an example of a power supply target range and a power supply range of an exemplary embodiment of the present disclosure. 
         FIG. 6  is a first diagram showing an example of movement control of a mobile body of an exemplary embodiment of the present disclosure. 
         FIG. 7  is a second diagram showing an example of the movement control of a mobile body of an exemplary embodiment of the present disclosure. 
         FIGS. 8A-8D  are a diagrams showing an example of movement control in a case where a mobile body of an exemplary embodiment of the present disclosure moves spirally to the power supply range. 
         FIG. 9  is a diagram showing an example of the movement control in a case where a mobile body of an exemplary embodiment of the present disclosure performs sweeping. 
         FIG. 10  is a diagram showing an example of the movement control in a case where a mobile body of an exemplary embodiment of the present disclosure moves in a receding direction from the power transmission resonator. 
         FIGS. 11A and 11B  are diagrams showing an example of a rotation axis serving as the basis of rotational movement of a mobile body of an exemplary embodiment of the present disclosure. 
         FIGS. 12A and 12B  are diagrams showing an example of a layout of a power reception surface and the rotation axis of a mobile body of an exemplary embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Exemplary embodiments of the present disclosure will be described below with reference to the drawings. First of all, an outline of a mobile body  200  will be described with reference to  FIG. 1 . 
       FIG. 1  is a diagram showing an example of a configuration of a mobile body system  1  of this embodiment. The mobile body system  1  includes mobile bodies  200  and non-contact power supply devices  100 . Each mobile body  200  is an AGV (automatic guided vehicle) that moves in a factory or in a hospital, for example. In this example, each mobile body  200  moves along a guided track RD. Each non-contact power supply device  100  supplies power to one of the mobile bodies  200  in accordance with a non-contact power supply method. In this example, each non-contact power supply device  100  is installed in the vicinity of the guided track RD. Each mobile body  200  moves along the guided track RD and consumes the power as a consequence of the movement. When the mobile body  200  moves to a position where the non-contact power supply device  100  is installed, the mobile body  200  receives power supply from the non-contact power supply device  100 . That is to say, the mobile body  200  is driven by the power wirelessly transmitted from the non-contact power supply device  100 . 
     Control of a start of power supply and a stop of the power supply takes place between the non-contact power supply device  100  and the mobile body  200  by means of communication. Here, the communication is optical communication, for instance. In this example, when the mobile body  200  arrives in a power supply target range OPS, the mobile body  200  transmits a power supply start request to the non-contact power supply device  100 . Upon receipt of the power supply start request from the mobile body  200 , the non-contact power supply device  100  starts wireless power transfer to a power supply range RPS. Meanwhile, when a power supply stop condition is met, such as when an amount of power supply reaches a target value, the mobile body  200  transmits a power supply stop request to the non-contact power supply device  100 . Upon receipt of the power supply stop request from the mobile body  200 , the non-contact power supply device  100  stops the wireless power transfer. 
     Specific configuration examples of the non-contact power supply device  100  and the mobile body  200  are shown in  FIGS. 2 to 4 .  FIG. 2  is a diagram showing an example of an external configuration of the mobile body  200  of this embodiment. The mobile body  200  includes a loading platform  201 , wheels  202 , and a power reception resonator  210 . If the coordinates of the mobile body  200  need to be specified in the following description, the coordinates will be described by using an xyz orthogonal coordinate system. In the xyz orthogonal coordinate system, an xy-plane is parallel to a movement plane (such as a floor surface) of the mobile body  200 . The z-axis indicates the vertical direction. The x-axis indicates a traveling direction of the mobile body  200 . The y-axis direction indicates a direction orthogonal to the traveling direction of the mobile body  200 . In this example, the x-axis is parallel to a direction of a long side of the loading platform  201 . The y-axis is parallel to a direction of a short side of the loading platform  201 . A positive direction on the x-axis is also referred to as a forward movement direction of the mobile body  200 . Meanwhile, a negative direction on the x-axis is also referred to as a backward movement direction of the mobile body  200 . In other words, the x-axis represents the forward and backward movement directions of the mobile body  200 . 
     An item as a target for conveyance by the mobile body  200  is loaded on the loading platform  201 . Examples of such a conveyance target item include a product manufactured in a factory as well as a component, a jig, a tool and the like used for forming such a product. The wheels  202  are driven by a motor  240 . In this example, the wheels  202  include a wheel  202 - 1  and a wheel  202 - 2 . The wheel  202 - 1  and the wheel  202 - 2  are arranged away from each other in the y-axis direction, that is, a right-left direction of the mobile body  200 . The mobile body  200  moves as a consequence of driving the wheel  202 - 1  and the wheel  202 - 2 . Moreover, the mobile body  200  steers its traveling direction by driving the wheel  202 - 1  and the wheel  202 - 2  at different rotational speeds from each other. Furthermore, the mobile body  200  performs rotational movement, that is, turns around the center position of the mobile body  200  serving as the rotational center by driving the wheel  202 - 1  and the wheel  202 - 2  in different rotational directions from each other. In other words, the mobile body  200  includes at least two wheels  202  that are driven independently from each other. Moreover, the wheels  202  have a steering axis in the z-axis direction. Specifically, when the wheels  202  are steered in the x-axis direction, the mobile body  200  can move in the positive and negative directions on the x-axis. Meanwhile, when the wheels  202  are steered in the y-axis direction, the mobile body  200  can move in the positive and negative directions on the y-axis. In the following description, if the wheel  202 - 1  and the wheel  202 - 2  need not be distinguished from each other, then each wheel will be referred to as the wheel  202 . 
       FIG. 3  is a diagram showing an example of functional configurations of the non-contact power supply device  100  and the mobile body  200  of this embodiment. The non-contact power supply device  100  includes a power transmission resonator  110 , an inverter circuit  120 , a power transmission control circuit  140 , and a power transmission communication unit  150 . The inverter circuit  120  outputs power supplied from a DC power source  50  to the power transmission resonator  110  based on the control of the power transmission control circuit  140 . Although this example describes a case where the power source of the non-contact power supply device  100  is the DC power source  50 , the present invention is not limited to this configuration. For instance, the power source of the non-contact power supply device  100  may be an alternating-current source such as a commercial power source. 
     The power transmission resonator  110  transmits the power to the power reception resonator  210  in accordance with the non-contact power supply method. The power transmission communication unit  150  includes an infrared sensor and the like, for instance, and receives communication infrared light emitted from a power reception communication unit  280  of the mobile body  200 . Alternatively, the power transmission communication unit  150  may emit communication infrared light to the power reception communication unit  280  of the mobile body  200 . The power transmission control circuit  140  controls the power supply by the power transmission resonator  110  based on the infrared light received by the power transmission communication unit  150 . 
     The mobile body  200  includes the power reception resonator  210 , a rectifier  220 , a power storage unit  230 , the motor  240 , a DC-DC converter  250 , a controller  260 , and the power reception communication unit  280 . Meanwhile, the controller  260  includes a voltage detector  261  and a power reception control circuit  262 . 
     The power reception resonator  210  receives the power supplied from the power transmission resonator  110 . A relation of layout positions between the power transmission resonator  110  and the power reception resonator  210  will be described with reference to  FIG. 4 . 
       FIG. 4  is a diagram showing an example of a layout relation between the power transmission resonator  110  and the power reception resonator  210  of this embodiment. The power transmission resonator  110  includes a power transmission coil  112 . The power reception resonator  210  includes a power reception coil  212 . 
     If the coordinates of the non-contact power supply device  100  need to be specified in the following description, the coordinates will be described by using the XYZ orthogonal coordinate system. A power transmission surface of the power transmission resonator  110  of the non-contact power supply device  100  is located opposite to a power reception surface of the power reception resonator  210 . The direction to locate the power transmission surface of the power transmission resonator  110  and the direction to locate the power reception surface of the power reception resonator  210  can be selected from various options depending on the form of the non-contact power supply device  100  and the form of the mobile body  200 . For example, the mobile body  200  may be provided with the power reception surface of the power reception resonator  210  on a bottom surface thereof. In this case, the power transmission surface of the power transmission resonator  110  is installed on a surface opposed to the bottom surface of the mobile body  200 , or more specifically, buried in a floor surface, for example. Meanwhile, the mobile body  200  may be provided with the power reception surface of the power reception resonator  210  on a side surface thereof. In this case, the power transmission surface of the power transmission resonator  110  is installed on a surface opposed to the side surface of the mobile body  200 , or more specifically, on a side surface of the non-contact power supply device  100 , for example. The following description will be given of the example in which the power reception surface of the power reception resonator  210  is located on the side surface of the mobile body  200  and the power transmission surface of the power transmission resonator  110  is located on the side surface of the non-contact power supply device  100 . In the case of this example, the XY-plane in the XYZ orthogonal coordinate system is a plane on which the mobile body  200  moves by using the wheels  202 , that is, the plane parallel to the floor surface. On the other hand, the X-axis indicates a direction parallel to the power transmission surface of the power transmission resonator  110 . It is also possible to say that the X-axis indicates a direction of a long side of the power transmission coil  112 . The Y-axis indicates a direction orthogonal to the power transmission surface of the power transmission resonator  110 . The direction orthogonal to the power transmission surface of the power transmission resonator  110  represents a direction of the highest power transmission energy density by the power transmission coil  112 . In other words, the Y-axis represents a principal direction of the power transmission by the power transmission coil  112 . The Z-axis indicates the vertically upward direction. 
     The power transmission coil  112  includes a conductor line (winding) which is wound such that the conductor line becomes relatively long in the X direction and relatively short in the Z direction. Likewise, the power reception coil  212  in the power reception resonator  210  also includes a conductor line (winding), which is wound such that the conductor line becomes long in the x direction and short in the z direction. In this embodiment, the shape and size of the power transmission coil  112  are different from those of the power reception coil  212  as shown in  FIG. 4 . In this embodiment, the size of a region defined by the winding of the power reception coil  212  is smaller than the size of a region redefined by the winding of the power transmission coil  112 . The power transfer takes place in a state where the power transmission coil  112  and the power reception coil  212  are opposed to each other. To be more precise, electric charge takes place in a state where a plane defined by the winding of the power transmission coil  112  and a plane defined by the winding of the power reception coil  212  are opposed to each other. Note that it is possible to perform the electric charge not only in the case where these planes are perfectly parallel to each other but also in the case where the planes are inclined relative to each other. Moreover, since the power transmission coil  112  has such a shape that is elongated in the X direction, the state of the coils being opposed to each other is maintained and the power transfer can be kept at high efficiency even when the mobile body  200  is slightly displaced in the X direction. 
     As shown in  FIG. 3 , the rectifier  220  rectifies the alternating-current power received by the power reception resonator  210 , and supplies the rectified power to the power storage unit  230 . The power storage unit  230  stores the power received by the power reception resonator  210 . Meanwhile, the power storage unit  230  supplies the stored power to the DC-DC converter  250 . 
     The DC-DC converter  250  feeds the power supplied from the power storage unit  230  to the motor  240  based on the control of the controller  260 . Specifically, the DC-DC converter  250  feeds the power supplied from the power storage unit  230  to the motor  240  based on the control of the power reception control circuit  262 . The motor  240  drives the wheels  202  by using the supplied power. The supplied power is the power stored in the power storage unit  230 . In other words, the motor  240  moves the mobile body  200  by using the power stored in the power storage unit  230 . The controller  260  includes the voltage detector  261  and the power reception control circuit  262 . The controller  260  controls the power supply by the DC-DC converter  250 . Specifically, the voltage detector  261  detects a voltage of the power supplied to the motor  240 . Meanwhile, the power reception control circuit  262  controls the power supply by the DC-DC converter  250  based on the voltage detected with the voltage detector  261 . As described above, the controller  260  controls the power which the DC-DC converter  250  supplies to the motor  240 . The controller  260  therefore controls the motor  240 . 
     The power reception communication unit  280  includes a light source to emit the infrared light, and emits the infrared light based on the control of the power reception control circuit  262 . Moreover, the power reception communication unit  280  receives the infrared light emitted from the power transmission communication unit  150 . Meanwhile, the power reception control circuit  262  controls the power reception communication unit  280 . Specifically, the power reception control circuit  262  outputs a power supply start request signal and a power stop request signal to the power reception communication unit  280 . The power reception communication unit  280  sends the non-contact power supply device  100  the power supply start request signal and the power stop request signal outputted from the power reception control circuit  262 . Although the case where the power transmission communication unit  150  receives the power supply start request signal and the power stop request signal from the power reception communication unit  280  has been described above, the present invention is not limited to this configuration. The power transmission communication unit  150  and the power reception communication unit  280  may perform the communication either constantly or at predetermined intervals. The controller  260  may receive from the power transmission communication unit  150  power reception status information R that indicates a state of power reception by the power reception resonator  210 . Alternatively, the controller  260  may be equipped with the power reception communication unit  280 . The mobile body  200  performs horizontal movement or rotational movement based on the power reception status information R received by the power reception communication unit  280 . Specifically, the mobile body  200  moves as a consequence of the controller  260  controlling the motor  240  based on the power reception status information R indicating the state of power reception by the power reception resonator  210 . In the following example, a description will be given of the case in which the power reception communication unit  280  sends the non-contact power supply device  100  the power supply start request signal and the power supply stop request signal outputted from the power reception control circuit  262 . 
     Relative positions among the non-contact power supply device  100 , the mobile body  200 , the power supply target range OPS, and the power supply range RPS will be described below with reference to  FIG. 5 .  FIG. 5  is a diagram showing an example of the power supply target range OPS and the power supply range RPS of the embodiment. The power supply target range OPS is a range in which the mobile body  200  makes a stop in order to receive the power supply from the non-contact power supply device  100 . The power supply range RPS is a range within the power supply target range OPS, in which the mobile body  200  can receive the power supply from the non-contact power supply device  100 . In this example, the non-contact power supply device  100  is installed along the X-axis. Meanwhile, the power transmission resonator  110  of the non-contact power supply device  100  transmits the power while setting the Y-axis as the center axis of the power transmission. 
     Here, the mobile body  200  grasps the position of the power supply target range OPS but does not grasp the position of the power supply range RPS. That is to say, even when the mobile body  200  arrives is the power supply target range OPS, the mobile body  200  cannot determine whether or not the mobile body  200  is located in the power supply range RPS by using position coordinates. As a consequence, even when the mobile body  200  is located in the power supply target range OPS, the mobile body  200  may be unable to receive the power from the non-contact power supply device  100  or may confront lower power supply efficiency than a target value. 
     In the meantime, the efficiency of the power supply to the mobile body  200  varies depending on relative positions and orientations between the power transmission resonator  110  of the non-contact power supply device  100  and the power reception resonator  210  of the mobile body  200 . Nonetheless, the mobile body  200  does not grasp the relative positions and orientations between the power transmission resonator  110  of the non-contact power supply device  100  and the power reception resonator  210 . In other words, even when the mobile body  200  arrives in the power supply target range OPS, the mobile body  200  cannot determine by use of the position coordinates as to whether or not the relative positions and orientations between the power transmission resonator  110  and the power reception resonator  210  meet the positions and orientations that bring about the fine power supply efficiency. 
     Specifically, it may be difficult for the power reception resonator  210  to receive the power supply if the power reception resonator  210  is located close by less than a predetermined distance dt 1  to the power transmission resonator  110 . On the other hand, it may be difficult for the power reception resonator  210  to receive the power supply if the power reception resonator  210  is located away by more than a predetermined distance dt 2  from the power transmission resonator  110 . The power supply range RPS is a range where the power reception resonator  210  is not close by less than the predetermined distance dt 1  to the power transmission resonator  110  and the power reception resonator  210  is not far by more than a predetermined distance dt 2  away from the power transmission resonator  110 . Meanwhile, the power supply target range OPS is a range including the power supply range RPS, which has dimensions of the predetermined distance dt 3  in the X-axis direction away from the center C of the power supply range RPS and a predetermined distance dt 4  in the Y-axis direction away from the center C. Here, the predetermined distance dt 1 , the predetermined distance dt 2 , the predetermined distance dt 3 , and the predetermined distance dt 4  are distances based on a power transmission performance of the power transmission resonator  110 . 
     An example of movement control of the mobile body  200  will be described below with reference to  FIG. 6 .  FIG. 6  is a first diagram showing the example of the movement control of the mobile body  200  of this embodiment. In a case where the power reception status information R indicates that the power reception status is not fine, the mobile body  200  moves away from a current position along a predetermined movement axis. Here, the case where the power reception status information R indicates that the power reception status is not fine is a case where the actual power reception efficiency is lower than the target value of the power reception efficiency of the mobile body  200 . Here, a description will be given of a case where the direction on the x-axis of the mobile body  200  and the direction on the X-axis of the non-contact power supply device  100  coincide with each other, that is, when the power transmission surface of the power transmission resonator  110  of the non-contact power supply device  100  and the power reception surface of the power reception resonator  210  of the mobile body  200  are parallel to each other. In this case, the mobile body  200  moves in a direction dr 1  which is a direction along the x-axis. Moreover, the mobile body  200  moves in a direction dr 2  which is a direction along the y-axis. The axis indicating the direction dr 1  represents an example of a first movement axis. Meanwhile, the axis indicating the direction dr 2  represents an example of a second movement axis. In this example, the mobile body  200  moves along the first movement axis and the second movement axis which have axial directions that are different from each other. Here, if the power transmission surface of the power transmission resonator  110  and the power reception surface of the power reception resonator  210  are parallel to each other, then the direction dr 1  is the direction along the X-axis while the direction dr 2  is the direction along the Y-axis. 
     The mobile body  200  repeats the movement in the direction dr 1  and the movement in the direction dr 2  alternately based on the power reception status information R. The mobile body  200  updates the power reception status information R every time the mobile body  200  changes its position, and searches for a position where the power reception status is fine based on the updated power reception status information R. As a consequence, the mobile body  200  moves to the position where the power reception status is fine, that is, the position in the power supply range RPS. As shown in  FIG. 6 , in this example, the mobile body  200  alternately repeats marking of a movement trail m 11 , a movement trail m 12 , . . . , and a movement trail m 15  in the direction dr 1 , and a movement trail m 21 , a movement trail m 22 , and a movement trail m 24  in the direction dr 2 , thus moving into the power supply range RPS. In other words, when the mobile body  200  makes a stop in the power supply target range OPS, the mobile body  200  moves in the direction of the first movement axis at least once and moves in the direction of the second movement axis at least once. 
     Here, the mobile body  200  possesses inertia that is attributable to its own weight as well as the weight of the conveyance target item, and may therefore not always be able to make a stop at an accurate target position when the mobile body  200  performs control to make a stop in the power supply target range OPS. In other words, even when the mobile body  200  makes a stop in the power supply target range OPS, the mobile body  200  may not be able to make a stop at a position where the power reception status is fine. If the mobile body  200  continues the power reception in the state where the power reception status is not fine, the mobile body  200  may require a long time until an amount of power reception reaches a target value. In this case, efficiency of conveyance by the mobile body  200  may be deteriorated. 
     The mobile body  200  of this embodiment searches for the position where the power reception status is fine in the case where the power reception status is not fine when the mobile body  200  makes a stop in the power supply target range OPS. Accordingly, the mobile body  200  of this embodiment can enhance the power supply efficiency. In addition, the mobile body  200  of this embodiment can move to the position where the power reception status is fine even when the mobile body  200  does not grasp the position of the non-contact power supply device  100 . 
     Another example of the movement control of the mobile body  200  will be described below with reference to  FIG. 7 .  FIG. 7  is a second diagram showing an example of the movement control of the mobile body  200  of this embodiment. In the case where the power reception status information R indicates that the power reception status is not fine, the mobile body  200  moves in a direction which is a combination of the x-axis and the y-axis. That is to say, in the case of this movement example, the mobile body  200  is capable of moving in obliquely forward and backward directions relative to the x-axis or the y-axis. Specifically, the mobile body  200  moves in a direction dr 3  which combines the negative direction on the x-axis with the negative direction on the y-axis and in a direction dr 4  which combines the negative direction on the x-axis with the positive direction on the y-axis. The axis indicating the direction dr 3  represents another example of the first movement axis. Meanwhile, the axis indicating the direction dr 4  represents another example of the second movement axis. The mobile body  200  repeats the movement in the direction dr 3  and the movement in the direction dr 4  based on the power reception status information R, thus moving into the power supply range RPS. As shown in  FIG. 7 , in this example, the mobile body  200  alternately repeats marking of a movement trail m 31 , a movement trail m 32 , and a movement trail m 33  in the direction dr 3 , and a movement trail m 41  and a movement trail m 42  in the direction dr 4 , thus moving into the power supply range RPS. In other words, when the mobile body  200  makes a stop in the power supply target range OPS, the mobile body  200  moves in the direction of the first movement axis at least once and moves in the direction of the second movement axis at least once. 
     The mobile body  200  not only moves in the x-axis direction and the y-axis direction, that is, forward and backward as well as rightward and leftward, but also moves in the directions which combine the x-axis and the y-axis, that is, in the obliquely forward and backward directions. By moving in the obliquely forward and backward directions relative to the x-axis or the y-axis, the mobile body  200  can reduce time for searching for the position with the fine power reception status as compared to the case of moving only forward and backward as well as rightward and leftward. 
     An example of movement control to locate the mobile body  200  in the power supply range RPS based on the power reception status information R will be described with reference to  FIGS. 8A-8D .  FIGS. 8A-8D  are diagrams showing an example of movement control in a case where the mobile body  200  of this embodiment moves spirally to the power supply range RPS. Here, the spiral movement means an action of the mobile body  200  to alternately repeat movement in the direction dr 1  or the opposite direction thereto and movement in the direction dr 2  or the opposite direction thereto. To be more precise, the spiral movement means iteration of movement by the mobile body  200  in the order of the movement in the direction dr 1 , the movement in the direction dr 2 , the movement in the opposite direction to the direction dr 1 , and the movement in the opposite direction to the direction dr 2 . There are two types of the spiral movement, namely, the movement from the inside to the outside of the spiral and the movement from the outside to the inside of the spiral. Here, the movement from the inside to the outside of the spiral is movement in such a direction that a movement distance for each side of the spiral becomes gradually longer as the movement progresses. On the other hand, the movement from the outside to the inside of the spiral is movement in such a direction that a movement distance for each side of the spiral becomes gradually shorter as the movement progresses.  FIGS. 8A and 8B  are diagrams showing an example in which the mobile body  200  spirally moves to the power supply range RPS by alternately repeating the movement in the directions indicated with the direction dr 1  and the direction dr 2  based on the power reception status information R. In the meantime,  FIGS. 8C and 8D  are diagrams showing an example in which the mobile body  200  spirally moves to the power supply range RPS by alternately repeating the movement in the directions indicated with the direction dr 3  and the direction dr 4  based on the power reception status information R. Specifically, the mobile body  200  spirally moves in the direction from the inside to the outside of the power supply target range OPS. 
     In the case of an example shown in  FIGS. 8A and 8C , the mobile body  200  moves in a direction from a current position to the outside of the power supply target range OPS. In this case, the mobile body  200  spirally moves from a range close to the current position gradually to a range far from the current position. For example, there may be a case where a distance is short from the current position of the mobile body  200  to the power supply range RPS. In this case, the mobile body  200  can reduce the time for searching for the position with the fine power reception status by moving in the direction from the current position gradually to the outside. 
     Meanwhile, in the case of an example shown in  FIGS. 8B and 8D , the mobile body  200  moves in a direction from the current position to the inside of the power supply target range OPS. In this case, the mobile body  200  moves for a long distance from the current position along an outside diameter of the spiral and then moves gradually for a shorter distance to the inside of the spiral. For example, there may be a case where the distance is long from the current position of the mobile body  200  to the power supply range RPS. In this case, the mobile body  200  can reduce the time for searching for the position with the fine power reception status by moving for a long distance along the outside diameter of the spiral. 
     Another example of the movement control to locate the mobile body  200  in the power supply range RPS based on the power reception status information R will be described with reference to  FIG. 9 .  FIG. 9  is a diagram showing an example of the movement control in a case where the mobile body  200  of this embodiment performs sweeping. The sweeping means an act of searching for a position in the power supply target range OPS where the power reception status is fine by causing the mobile body  200  to scan in two directions. In this example, the sweeping is an act of searching for the position in the power supply target range OPS where the power reception status is fine by scanning in a certain direction and in a different direction from the certain direction. Here, the “certain direction” is the direction dr 1 , for example. Meanwhile, the “different direction from the certain direction” is the direction dr 2 , for example. That is to say, in this example, the mobile body  200  sweeps in the direction dr 1  that is the direction along the x-axis and in the direction dr 2  that is the direction along the y-axis. 
     Although the description has been given of the case where the certain direction is the direction dr 1  while the different direction from the certain direction is the direction dr 2 , the present invention is not limited to this configuration. For instance, the certain direction may be the direction dr 3  and the different direction from the certain direction may be the direction dr 4 . Here, the certain direction represents an example of a direction along the first movement axis. Meanwhile, the different direction from the certain direction represents an example of a direction along the second movement axis. 
     Moreover, in this example, the power reception status shown in the power reception status information R is indicated by using a three-tier scale. Specifically, the power reception status is indicated in the power reception status information R by using any of three tiers of “high”, “medium”, and “low”. When the power reception status information R shows “high”, the information indicates that the power reception status of the mobile body  200  is fine. When the power reception status information R shows “medium”, the information indicates that the power reception status of the mobile body  200  is somewhere between fine and not fine. When the power reception status information R shows “low”, the information indicates that the power reception status of the mobile body  200  is not fine. In the example shown in  FIG. 9 , the power supply range RPS and a power supply allowable range MPS are included in the power supply target range OPS. Here, the power supply range RPS is a range where the power reception status information R shows “high”. Meanwhile, the power supply allowable range MPS is a range where the power reception status information R shows “medium”. In the meantime, of the power supply target range OPS, a range other than the power supply range RPS and the power supply allowable range MPS is a range where the power reception status information R shows “low”. 
     The mobile body  200  sweeps in the direction dr 1  from a certain position in the power supply target range OPS to an end point where the power reception status information R shows “low”. Moreover, based on a result of scanning the power reception status in the direction dr 1 , the mobile body  200  moves to a position where the power reception status information R shows a tier other than “low”. In the example shown in  FIG. 9 , the mobile body  200  moves to a position in the direction dr 1  where the power reception status information R shows “middle”. The mobile body  200  sweeps in the direction dr 2  from the position where the power reception status information R shows the tier other than “low”. The mobile body  200  sweeps in the direction dr 2  to an end point where the power reception status information R shows “low”. The mobile body  200  moves to a position in the direction dr 2  before moving to the end point where the power reception status information R shows “low”, the position having the fine power reception status. In the example shown in  FIG. 9 , the mobile body  200  moves in the direction dr 2  to a position where the power reception status information R shows “high”. 
     Here, the mobile body  200  sweeps in the direction dr 1 , thereby scanning for a location in the direction dr 1  with the fine power reception status. Moreover, the mobile body  200  scans for a location in the direction dr 2  with the fine power reception status based on the power reception status information R at the time of sweeping in the direction dr 1 . In other words, the mobile body  200  moves in the direction of the second movement axis based on the power reception status information R obtained as a result of the movement in the direction of the first movement axis. That is to say, when the mobile body  200  makes a stop in the power supply target range OPS, the mobile body  200  moves in the direction of the first movement axis at least once and moves in the direction of the second movement axis at least once. In this way, the mobile body  200  can move to the position with the fine power reception status by sweeping along the first movement axis and the second movement axis. 
     Although the description has been given of the case where the power reception status is indicated by using a three-tier scale, the present invention is not limited to this configuration. The power reception status may be indicated with the degree of accuracy that applies three or more tiers. Alternatively, the power reception status may be indicated with a continuous volume. In this case, the power reception status may be segmented by using at least two thresholds and indicated with the degree of accuracy that applies at least three tiers. 
     An example of the movement control by which the mobile body  200  moves in a receding direction edr that is a direction to move away from the power transmission resonator  110  will be described with reference to  FIG. 10 .  FIG. 10  is a diagram showing an example of the movement control in a case where the mobile body  200  of this embodiment moves in the receding direction edr from the power transmission resonator  110 . Each receding direction edr therein is a direction of power transmission from the power transmission resonator  110 . In other words, the receding direction edr is a direction of power reception by a power reception surface rsf of the power reception resonator  210 , which is a surface configured to receive the power. As described previously, in this example, the power transmission resonator  110  provided to the non-contact power supply device  100  transmits the power in the direction of the Y-axis from the position of the power transmission resonator  110 . In this case, the receding direction edr is a direction containing a component in the Y-axis direction. 
     For example, the mobile body  200  may be located at a position in a range close to the power transmission resonator  110 , where the power reception status information R indicates that the power reception status is not fine. In the meantime, as described previously, there may be a case where the power transmission surface of the power transmission resonator  110  of the non-contact power supply device  100  is installed perpendicular to the floor surface, or in other words, to the XY-plane. In this case, the mobile body  200  may collide with the power transmission resonator  110  if the mobile body  200  moves in the direction to approach the power transmission resonator  110 . When the power transmission surface of the power transmission resonator  110  of the non-contact power supply device  100  is installed perpendicular to the floor surface, the mobile body  200  may encounter the case where the power reception status information R indicates that the power reception status it not fine. In this case, the mobile body  200  moves in the receding direction edr to suppress a collision with the power transmission resonator  110 . Thus, it is possible to suppress breakage and failure due to the collision of the mobile body  200  and the non-contact power supply device  100 . 
     Now, the rotational movement of the mobile body  200  will be described below. There may be a case where the mobile body  200  fails to make a stop at a position where the power reception surface of the power reception resonator  210  is parallel to the power transmission surface of the power transmission resonator  110 . This case may be attributable to a difference in friction coefficient between the two wheels of the mobile body  200 , or to the occurrence of a variation in timing to stop between the two wheels. Here, the power reception status indicated by the power reception status information R varies depending on an angle of opposition of the power transmission resonator  110  to the power reception resonator  210 . For example, the power reception status indicated by the power reception status information R is fine when the power reception surface rsf of the power reception resonator  210  is orthogonal to the direction of the power transmission from the power transmission resonator  110 . In other words, the power reception status of the mobile body  200  is fine when the mobile body  200  makes a stop at a position where the power reception surface of the power reception resonator  210  is parallel to the power transmission surface of the power transmission resonator  110 . On the other hand, the power reception status indicated by the power reception status information R is not fine when the power reception surface rsf of the power reception resonator  210  is parallel to the direction of the power transmission from the power transmission resonator  110 . In other words, the power reception status of the mobile body  200  is not fine when the mobile body  200  makes a stop at a position where the power reception surface of the power reception resonator  210  is not parallel to the power transmission surface of the power transmission resonator  110 . As a consequence, in order to efficiently receive the power transmitted from the power transmission resonator  110 , the mobile body  200  may be required to adjust an angle of the power reception surface rsf relative to the power transmission surface of the power transmission resonator  110 . 
     A specific example of the rotation axis serving as the basis of the rotational movement of the mobile body  200  will be described with reference to  FIGS. 11A and 11B .  FIGS. 11A and 11B  are diagrams showing an example of the rotation axis serving as the basis of the rotational movement of the mobile body  200  of this embodiment. Specifically,  FIG. 11A  is a side view showing a layout example of the mobile body  200 . Meanwhile,  FIG. 11B  is a rear view showing the layout example of the mobile body  200 . 
     The mobile body  200  performs the rotational movement based on a certain rotation axis axs. The rotation axis axs is an axis orthogonal to an axle plane pca which is a plane including the axle axl of the wheels  202 . By means of rotation based on the rotation axis axs, the mobile body  200  can be rotated on the plane including the axle axl of the wheels  202 . Moreover, in this example, a height h in the vertical direction from a floor surface FL to the power transmission resonator  110  is equal to a height h in the vertical direction from the floor surface FL to the power reception resonator  210 . Here, if the power reception resonator  210  is located at a height in terms of the height in the vertical direction from the floor surface FL, which corresponds to the height of the power transmission resonator  110 , then the mobile body  200  can change the power reception status by performing the movement or the rotational movement without requiring any movement in the Z-axis direction. 
     Although the description has been given of the case where the wheels  202  have the single axle axl, the present invention is not limited to this configuration. For example, there is a case where the mobile body  200  includes the wheels  202  having different diameters from each other. In this case, the rotation axis axs may be an axis that is orthogonal to the axle plane pca that includes the axle axl of any of the wheels  202  provided to the mobile body  200 , which is the wheel  202  used for the rotation. 
     Meanwhile, although the description has been given of the case where the power transmission resonator  110  transmits the power in the Y-axis direction parallel to the floor surface FL, the present invention is not limited to this configuration. The power transmission resonator  110  may transmit the power in any direction as long as such a direction includes the direction parallel to the floor surface FL. For example, the power transmission resonator  110  may transmit the power in any direction as long as that direction is a direction other than the Z-axis direction being orthogonal to the floor surface FL in which the power transmission resonator  110  is installed. In this case, the mobile body  200  can be rotated in such a way as to change the angle of opposition of the power transmission resonator  110  to the power reception resonator  210 , thereby changing the power reception status. 
     Now, a more specific example of the rotation axis serving as the basis of the rotational movement of the mobile body  200  will be described with reference to  FIGS. 12A and 12B .  FIGS. 12A and 12B  are diagrams showing an example of a layout of the power reception surface rsf and the rotation axis axs of the mobile body  200  of this embodiment. Specifically,  FIG. 12A  shows a rotation axis axsF which is the rotation axis axs located on the non-installed side of the power transmission resonator  110  based on the position of the power reception surface rsf. Meanwhile,  FIG. 12B  shows a rotation axis axsN which is the rotation axis axs located on the installed side of the power transmission resonator  110  based on the position of the power reception surface rsf. 
     In the example shown in  FIG. 12A , the position of the power reception resonator  210  is changed as a consequence of the rotational movement of the mobile body  200  based on the rotation axis axsF. Along with the rotational movement of the mobile body  200  and the movement of the power reception resonator  210 , the angle of opposition of the power transmission resonator  110  to the power reception resonator  210  is changed and the power reception status is changed accordingly. As a consequence, the mobile body  200  can detect a direction of installation of the power transmission resonator  110  by performing the rotational movement based on the power reception status information R in such a direction that can bring about the fine power reception status. 
     In the example shown in  FIG. 12B , the position of the power reception resonator  210  is changed as a consequence of the rotational movement of the mobile body  200  based on the rotation axis axsN. Along with the rotational movement of the mobile body  200  and the movement of the power reception resonator  210 , the angle of opposition of the power transmission resonator  110  to the power reception resonator  210  is changed and the power reception status is changed accordingly. As a consequence, the mobile body  200  can detect a direction of installation of the power transmission resonator  110  by performing the rotational movement based on the power reception status information R in such a direction that can bring about the fine power reception status. 
     Although the description has been given of the case where the mobile body  200  performs the rotational movement based on either the rotation axis axsF or the rotation axis axsN, the present invention is not limited to this configuration. The mobile body  200  may perform the rotational movement based on both the rotation axis axsF and the rotation axis axsN. For example, the mobile body  200  performs the rotational movement based on the rotation axis axsF and detects the direction of installation of the power transmission resonator  110 . Meanwhile, the mobile body  200  may perform the rotational movement based on the rotation axis axsF and then perform the rotational movement based on the rotation axis axsN. The series of the rotational movement enables the mobile body  200  to change the angle of opposition of the power transmission resonator  110  to the power reception resonator  210 . In this way, the mobile body  200  can perform the rotational movement in such a direction to obtain the fine power reception status at the current position. Here, the rotation axis axsF represents an example of a first rotation axis. Meanwhile, the rotation axis axsN represents an example of a second rotation axis. Moreover, in this case, the second rotation axis is a rotation axis to be located at a position away in an opposite direction to the direction indicated with a power-receiving direction from the position of the first rotation axis. 
     Although the description has been given of the case where the power reception resonator  210  is located on the side surface of the mobile body  200 , the present invention is not limited to this configuration. For example, when a side surface of the mobile body  200  has an opening, the power reception resonator  210  may be located inside the opening. 
     Features of the above-described preferred embodiments and the modifications thereof may be combined appropriately as long as no conflict arises. While preferred embodiments of the present disclosure have been described above, it is to be understood that variations and modifications will be apparent to those skilled in the art without departing from the scope and spirit of the present disclosure. The scope of the present disclosure, therefore, is to be determined solely by the following claims.