Abstract:
Embodiments of the invention are directed to a system for recharging a mobile robot as a power source. In one embodiment the system comprises a power transmission link having a first end positioned at a selectively located charging station and a second end connected to the battery carried by the robot, the transmission link being configured to transmit power from its first end to its second end to charge the battery. The system further comprises a first wireless power transmitter coupled to receive power from a specified power source, and a first wireless power receiver, connected to the first end of the transmission link and located at a prespecified distance from the first wireless power transmitter. The first wireless power receiver is configured to receive power transmitted across the prespecified distance from the first wireless power transmitter, and to provide power to the first end of the transmission link, for transmission to charge the battery.

Description:
FIELD OF THE INVENTION 
     The invention disclosed and claimed herein pertains to a system and method for charging a battery used as a power source for a mobile robot or the like. More particularly, the invention pertains to a system and method of the above type that uses wireless power transmission, thus delivers more mobile robot durability, and is minimally destructive to the surrounding environment. 
     BACKGROUND OF THE INVENTION 
     Power charging stations for mobile outdoor service robots, such as robotic lawnmowers, are well known in the art. If a robot vehicle uses an electric battery as a source of power, the robot can be directed to the station whenever it is necessary to charge or recharge the battery. However, charging arrangements of this type, when used outdoors, can have significant drawbacks or deficiencies. 
     As an example, in currently available systems, both the robot vehicle and the charging station have corresponding or complementary conductors or conductive elements. The conductive elements must be mated together, in order to transfer electric power from the station to the robot vehicle. However, these conductive elements are typically exposed to weather conditions and moisture, and over time may become oxidized and mechanically fatigued. Mud and debris can also collect on the conductive elements. As a result, the capability to transfer power to the robot, using these conductive elements, becomes degraded or diminished, and the overall system durability, compromised. 
     Another problem with presently used outdoor charging systems is that an exterior or outdoor electric outlet will generally be required as a power source, but may not be conveniently available. For example, it may be desired to use a robotic lawnmower of the above type to mow a lawn which is adjacent to a house or other building that has no exterior outlet. Alternatively, the only exterior outlets could be on a side of the building that is opposite to the lawn that is to be mowed. In either case, it would be necessary to install an exterior outlet, which could be expensive and also destructive to the building. 
     In addition, outdoor charging systems of the above type generally have only a single charging station. This can result in excessive wear of grass or other yard elements that are adjacent to the station, since the robotic mower must frequently go to and maneuver around this location. It might be possible to alleviate this problem by providing multiple charging stations at different locations. However, it would then be necessary to provide an exterior outlet at each of the multiple locations, which could further aggravate the problem discussed above in regard to the availability of such outlets, as well as increasing overall system cost. 
     SUMMARY 
     Embodiments of the invention are directed to a system for recharging a battery that is carried by a mobile robot or robot vehicle as a power source. The system comprises a power transmission link having a first end positioned at a selectively located charging station, and a second end connected to the battery carried by the robot, the transmission link being configured to transmit power from its first end to its second end to charge the battery. The system further comprises a first wireless power transmitter coupled to receive power from a specified power source, and a first wireless power receiver connected to the first end of the transmission link and located at a prespecified distance from the first wireless power transmitter. The first wireless power receiver is configured to receive power transmitted across the prespecified distance from the first wireless power transmitter, and to provide power to the first end of the transmission link, for transmission to charge the battery. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The novel features believed characteristic of the illustrative embodiments are set forth in the appended claims. The illustrative embodiments, however, as well as a preferred mode of use, further objectives and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment of the present invention when read in conjunction with the accompanying drawings, wherein: 
         FIG. 1  is a schematic diagram showing an embodiment of the invention; 
         FIG. 2  is a schematic overhead view showing a further embodiment of the invention; 
         FIG. 3  is a schematic diagram showing a further embodiment of the invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to  FIG. 1 , there is shown a service robot  102  for performing outdoor tasks of some type, as directed by a conventional control mechanism (not shown) that may be remotely located or carried aboard the robot. Robot  102  may by way of example comprise a robotic lawnmower, but the invention is not limited thereto.  FIG. 1  shows robot  102  provided with a rechargeable electric battery  104 , which provides power for moving and maneuvering robot  102 , and also for performing other functions needed in the operation of robot  102 . 
       FIG. 1  further shows a charging station  106 , which is provided to charge or recharge battery  104  of the service robot  102 , as required. Station  106  is removably placed upon a plate or base plate  124 , described hereinafter in further detail. In accordance with an embodiment of the invention, station  106  is furnished with a wireless power transmitter  108 , which is coupled to a source of power as likewise described hereinafter in further detail. Robot  102  is provided with a complementary wireless power receiver  110 , which is connected to battery  104 . Transmitter  108  and receiver  110  may, for example, be respective components of a system known in the art that transmits power by inductive coupling, rather than through a wire or other conductor. Systems of this type are referred to such as in SAE J1773, a standard for induction powered coupling. As used herein, “power transfer” and “energy transfer” are viewed as interchangeable, recognizing that power is energy per unit time. 
     At present, systems are available that can transfer power on the order of hundreds of watts from a wireless power transmitter to a wireless power receiver, when the transmitter and receiver are separated by a spacing on the order of twelve inches to three feet or more. Thus, in order to charge battery  104 , robot  102  would be maneuvered by its control to position receiver  110  at a distance or spacing from transmitter  108  that is within a pre-specified range. The wireless transmitter  108  is then operated to transmit power P 1  to wireless receiver  110 , and receiver  110  couples the received power to recharge battery  104 . 
     The power transfer efficiency between transmitter and receiver drops as the distance between them grows. At some distance, it is impractical to transfer power between the transmitter and receiver. This defines the effective range of power transfer. 
     It will appreciated that by using transmitter  108  and receiver  110  to transfer power, it is not necessary to mate or join complementary conductive elements together to effect power transfer, unlike certain prior art arrangements. Also, power can be transferred while transmitter  108  and receiver  110  are both kept tightly sealed, and thus protected against moisture, mud and the like. 
     Referring further to  FIG. 1 , there is shown a wall  112  that is proximate or adjacent to charging station  106 , wherein the wall has an exterior side  112   a  and an interior side  112   b . Wall  112  may be an exterior or outside wall of a conventional house, garage or other detached building.  FIG. 1  shows that station  106  is located outdoors, adjacent to the exterior side  112   a  of wall  112 .  FIG. 1  also shows a conventional 110 volt electrical outlet  114 , adjoining the interior side  112   b  of the wall. 
     In accordance with embodiments of the invention, it is intended to use the conventional interior outlet  114  as the power source for wireless transmitter  108 , and thus as the source for charging battery  104 . To accomplish this,  FIG. 1  shows a wireless power transmitter  116  mounted to the interior side  112   b  of wall  112 , proximate to outlet  114 . Transmitter  116  may be similar or identical to wireless transmitter  108 , and is provided with an electric cord  126  that can be plugged into a socket of outlet  114 .  FIG. 1  also shows a wireless power receiver  118 , which may be similar or identical to wireless receiver  110 , and which is mounted to the exterior side  112   a  of wall  112 , in opposing relationship with transmitter  116 . 
     By providing the components  116  and  118  arranged as shown by  FIG. 1 , power can be readily obtained by wireless transmitter  116  from interior outlet  114 . Transmitter  116  can then transfer the power through wall  112 , as power P 2 , to wireless receiver  118 .  FIG. 1  further shows receiver  118  connected to wireless transmitter  108  at station  106  by means of a power cord, or other conductor  120 . Thus, power can travel from receiver  118  to wireless power transmitter  108  through conductor  120 , in order to supply power needed by transmitter  108  and receiver  110  to charge battery  104 . Moreover, while the power is initially obtained from an outlet located inside the building of which wall  112  is part, it is unnecessary to make a hole through or otherwise modify wall  112 , in order to deliver power through wall  112  to charging station  106  and robot  102 . 
     In different embodiments, the space between transmitter and receiver may be a material or structure other than a wall. The opposing sides of the space may be arbitrarily designated interior and exterior. In another embodiment, receiver  118  could be located with the housing of station  106 . 
     In embodiments of the invention, it may be useful to enable charging station  106  to be readily removable from base plate  124 , such as for secure storage when it is not in use. Alternatively, station  106  may need to be periodically relocated, in order to minimize yard wear at any one location. Accordingly, conductor  120  may be detachably connected to receiver  118  such as by means of a plug and socket arrangement  122 . Also, it may be desirable to securely attach station  106  to base plate  124 , whenever the station is placed thereon.  FIG. 1  thus shows locking mechanisms  140  provided to selectively lock station  106  to plate  124 . Mechanisms  140  may be operated or released by means of a key or the like. 
     To ensure that base plate  124  is firmly connected to a location on the ground, anchors  128  are provided. Usefully, each anchor  128  is of a type that may be screwed into the ground by hand, to attach the plate  124 , and may be unscrewed to release the plate. In general, anchor  128  may be any means which makes it difficult for unauthorized movement of charging station  106 . For example, it may be desired to relocate the base plate  124 . Also, to enhance security a tampering sensor  130  is placed in base plate  124 , wherein the sensor  130  is a capacitive sensor that can detect a change in electrical permittivity under the station that is not explainable by soil moisture changes. For example, if a shovel was used by an unauthorized person to dig around the anchors  128 , sensor  130  would detect the presence of a metallic shovel, the absence of dirt or the presence of air. If tampering is detected, an alarm or alerting device  132  would be activated. Device  132  could comprise, for example, a visual, audio, email or cell phone related device. 
       FIG. 1  further shows charging station  106  equipped with an alternate power source comprising a solar cell  134  and a battery  136  or a battery and ultra capacitor. By providing the alternate power source, station  106  can be used far from a building, or in the complete absence of power line supplied electrical service. Other alternate power sources could include, but are not limited to, a fuel cell, a wind generator and a piezo electric generator. 
     Referring to  FIG. 2 , there is shown an overhead view of charging station  106  and wall  112 , to further illustrate embodiments of the invention.  FIG. 2  shows exterior side  112   a  of wall  112  adjacent to a yard, lawn or other area  202  in which work is to be performed by service robot  102  (not shown in  FIG. 2 ). 
       FIG. 2  also shows an interior outlet  204 , which is similar or identical to outlet  114 . Outlet  204  is mounted to interior side  112   b  of wall  112  and spaced apart from outlet  114  by some distance.  FIG. 2  further shows a base plate  124   a , similar or identical to base plate  124 , which is positioned near exterior side  112   a  of wall  112 , in close proximity to outlet  204 . Accordingly, charging station  106  could be moved from base plate  124  to base plate  124   a  if desired, such as to relieve yard wear around plate  124 . Components  116  and  118  could be relocated to the interior side  112   b  and the exterior side  112   a  of wall  112 , respectively, adjacent to outlet  204 . The outlet  204  could then be used to supply power for charging station  106 , in the manner described above in connection with outlet  114 . 
     Referring further to  FIG. 2 , there is shown a wall  206  adjacent to yard  202 , wherein wall  206  comprises an exterior wall section of a garage or other building that is detached from the building of wall  112 . Wall  206  has an exterior side  206   a  and an interior side  206   b , and an electric outlet  208  is mounted to interior side  206   b .  FIG. 2  further shows a base plate  124   b , similar or identical to base plate  124 , positioned near exterior side  206   a  of wall  206 , in close proximity to outlet  208 . Components  116  and  118  could be relocated to the interior side  206   b  and the exterior side  206   a  of wall  206 , respectively, adjacent to outlet  208 . 
       FIG. 2  further shows a base plate  124   c , which is similar or identical to base plate  124 , placed in yard  202  at a location that is not close to any electrical service outlets. If charging station  106  is moved to base plate  124   c , the alternate power source of charging station  106  would be used to supply power for charging robot  102 . In other illustrative embodiments, one or more of the base plates  124 ,  124   a ,  124   b , and  124   c  could simultaneously be attached to instances of charging station  106 . In such an embodiment, the service robot  102  could, for example without limitation, move to the closest charging station when recharging was needed. Similarly, in a worksite with multiple service robots  102 , more than one robot could be simultaneously charging. 
     Referring to  FIG. 3 , there is shown an embodiment of the invention that includes a charging station  302  and a base plate  304 . Charging station  302  is similar to charging station  106  in that it includes a wireless power transmitter  108 , which may be connected to a wireless power receiver  118  as described above, in order to supply power to a wireless power receiver  110  of robot  102 . Charging station  302  may also be provided with a battery  136 , a solar cell  134  and an alarm  132 , as likewise described above. 
     Base plate  304  is similar to base plate  124  in that anchors  128  are used therewith, and a tampering sensor  130  may be placed in the base plate  304 . However, station  302  and plate  304  are permanently and securely joined together, such as by means of a hinge  306 . Hinge  306  is positioned between plate  304  and the lower right corner of station  302 , as viewed in  FIG. 3 .  FIG. 3  also shows a locking mechanism, such as a hasp  308  and padlock  310  or the like, for releasably locking the lower left corner of station  302 , as viewed in  FIG. 3 , to base plate  304 . 
     Referring further to  FIG. 3 , there are shown wells or spaces  312 , which are each formed in plate  304  from the top thereof. Each well  312  is usefully of circular cross section, and is sized to accommodate one of the anchors  128 , there being one well for each anchor. When the locking mechanism is released, station  302  may be pivoted about hinge  306 , in a clockwise direction as viewed in  FIG. 3 . This will provide a user with access to each of the wells  312 . The user would thus be able to screw an anchor in each well into the ground at a selected location, and into engagement with a lower element of the base plate. The plate  304  would thereby be firmly connected to the ground at the selected location. 
     When the anchors are in place, the station  302  would be pivoted back to rest on plate  304 . The locking mechanism would then be engaged, such as by locking padlock  310 , so that station  302  would be retained in its rest position upon base plate  304 .  FIG. 3  shows station  302  provided with a floor  314 , which comprises a solid planar member that has no openings or apertures. The floor  314  is sized to overlay each of the wells  312 , when station  302  is in its rest position on plate  304 , to prevent access to anchors  128 . 
     It is thus seen that a configuration comprising station  302  and base plate  304  can readily be moved from one location to another. At the same time, the configuration provides significant security measures to prevent unauthorized removal. 
     The description of the different advantageous embodiments has been presented for purposes of illustration and description, and is not intended to be exhaustive or limited to the embodiments in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art. Further, different embodiments may provide different advantages as compared to other embodiments. The embodiment or embodiments selected are chosen and described in order to best explain the principles of the invention, the practical application, and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated.