Patent Publication Number: US-2023150597-A1

Title: Mobile robot having a removable wheel-drive assembly

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation-in-part of U.S. Design patent application Ser. No. 29/815,871, filed Nov. 17, 2021, which is incorporated herein by reference in its entirety. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a mobile robot having a removable wheel-drive assembly and more particularly to such a removable wheel-drive assembly which is readily field replaceable and well-sealed to increase safety and to protect against entry of dust and contaminants. 
     BACKGROUND ART 
     Autonomous mobile robots (AMRs) incorporate motor drive assemblies consisting of a motor, gearbox, axle and wheel. Replacement of such drive assemblies requires significant time, skill, and a variety of tools. Typical motor drive replacement requires removal of an external cover of the mobile robot base, disconnection of wiring, removal of the wheel assembly from a shaft, removal of the wheel well, and removal of the motor-gearbox from the robot frame. This sequence is reversed for installation of the motor new drive. 
     Given the complexity of the process and the time required, motor drive assemblies are not typically replaced in the field, i.e. at the facility in which the AMR is deployed. The AMR must typically be returned to the manufacturer for motor drive replacement resulting in significant downtime for the AMR, loss of productivity, and cost. 
     Motor drive failures may be caused by typical wear and tear over the drive&#39;s expected lifetime. Failures may also happen prematurely due to defective components or due to excessive contamination getting into the drive components. Facilities in which the AMRs operate may be subject to a significant amount of dust and other contaminates which can get into the motor drive components and cause premature motor drive failures. These kind of failures are particularly common as the components of typical motor drive units are not well sealed to protect against penetration of such dust and particulate matter. 
     An additional issue can result from the components of motor drive units not being well sealed from the environment. That is, when the components are not well covered, injuries can result, such as finger entrapment between the wheel and the wheel well. 
     Therefore, there is a need for a motor drive assembly, which is field replaceable and which is well-sealed to protect against entry of dust and contaminants and to increase safety. 
     SUMMARY OF THE EMBODIMENTS 
     In accordance with one embodiment of the disclosure there is a mobile robot having a removable wheel-drive assembly. The mobile robot includes a mobile base having a chassis and a first wheel well member including a flange. The removable wheel drive assembly includes a mounting bracket configured to be removably connected to the chassis of the mobile robot proximate the first wheel well member. There is a motor drive unit disposed on the mounting bracket and a wheel connected to the motor drive unit via an axle. The wheel has a tire disposed thereon. There is a second wheel well member disposed on the mounting bracket and positioned between the motor drive unit and the wheel. The second wheel well member includes a central section having an aperture through which the axle passes and a top surface. The top surface of the central section of the second wheel well member engages with the flange of the first wheel well member of the mobile base when the removable wheel drive assembly is mounted on the mobile base. 
     In one or more embodiments the following features may be included. The flange of the first wheel well member may be arched and the top surface of the central section of the second wheel well member may be arched and have a curvature that conforms with a curvature of the arched flange of the first wheel well member. The second wheel well member may include a first side section extending in a first direction from the central section and a second side section extending in a second direction from the central section, wherein the second direction is opposite the first direction. The second wheel well member may include a first curved fender extending outwardly from a face of the first side section and positioned proximate a tread surface of the tire. The first curved fender may be conformed with a curve of the tread surface of the tire and the second wheel well member may include a second curved fender extending outwardly from a face of the second side section and positioned proximate the tread surface of the tire. The second curved fender may be conformed with the curve of the tread surface of the tire. The second wheel well member may further include a first wheel well cover having a curved edge affixed to an edge of the first curved fender and extending in the first direction away from the first curved fender. There may be a second wheel well cover having a curved edge affixed to an edge of the second curved fender and extending in the second direction away from the second curved fender. 
     In other embodiments the following additional features may be included. The arched flange of the first wheel well member and the arched top surface of the central section of the second wheel well member may each have a curvature which conforms with the curvature of the wheel. When the arched flange of the first wheel well member and the arched top surface of the central section are mated they may form a wheel well surface. The second wheel well member may include a base portion connected to the mounting bracket and the mounting bracket may be connected to the chassis of the mobile robot with a plurality of fasteners. The motor drive unit may be a right-hand drive unit including a motor and a gearbox. The wheel well surface may be spaced less than 2 mm from the tire. The first curved fender may have a first surface with a width substantially equal to a width of a tread surface of the tire and the second curved fender may have a second surface with a width substantially equal to the width of the tread surface of the tire. The first wheel well member may include an arched surface with a width substantially equal to a width of a tread surface of the tire and having a first end aligned with the first surface of the first curved fender. There may be a second end aligned with the second surface of the second curved fender when the when the removable wheel drive assembly is mounted on the mobile base. The first surface, the second surface, and the arched surface may each be spaced less than 4 mm from the tread surface of the tire. The arched flange may be adjacent to extends in a direction perpendicular to the arched surface of the first wheel well member. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing features of embodiments will be more readily understood by reference to the following detailed description, taken with reference to the accompanying drawings, in which: 
         FIG.  1    is a front and side perspective view of an autonomous mobile robot with a replaceable wheel drive assembly according to an embodiment of this disclosure; 
         FIG.  2    is bottom and side perspective view of the autonomous mobile robot of  FIG.  1    with a replaceable wheel drive assembly removed; 
         FIG.  3    is a front perspective view of a portion of the autonomous mobile robot of  FIG.  1    with a replaceable wheel drive assembly removed; 
         FIG.  4 A  is a side perspective view of the lower wheel member of the replaceable wheel drive assembly with the remainder of the wheel drive assembly shown in phantom; 
         FIG.  4 B  is a front perspective view of the lower wheel member of the replaceable wheel drive assembly with the remainder of the wheel drive assembly shown in phantom; 
         FIG.  5 A  is an enlarged side view of a portion of the autonomous mobile robot of  FIG.  2   ; 
         FIG.  5 B  is an enlarged bottom view of a portion of the autonomous mobile robot of  FIG.  2   ; 
         FIG.  6    is a perspective view of the upper and lower wheel well members of the replaceable wheel drive assembly disclosed herein. 
     
    
    
     DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS 
     The disclosure and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments and examples that are described and/or illustrated in the accompanying drawings and detailed in the following description. It should be noted that the features illustrated in the drawings are not necessarily drawn to scale, and features of one embodiment may be employed with other embodiments, as the skilled artisan would recognize, even if not explicitly stated herein. 
     Descriptions of well-known components and processing techniques may be omitted to not unnecessarily obscure the embodiments of the disclosure. The examples used herein are intended merely to facilitate an understanding of ways in which the disclosure may be practiced and to further enable those of skill in the art to practice the embodiments of the disclosure. Accordingly, the examples and embodiments herein should not be construed as limiting the scope of the disclosure. Moreover, it is noted that like reference numerals represent similar parts throughout the several views of the drawings. 
     It is desired to provide a mobile robot with a wheel drive assembly that can be easily removed and replaced with minimal time, skill and tooling. The concept described herein permits the motor drive assembly to be removed from the bottom of the robot by disconnecting wiring and removing several screws. The motor drive assembly described herein is also well-sealed to protect against entry of dust and contaminants into the components which may cause premature failure. Additionally, the design restricts access to the components of the motor drive assembly when it is installed on a robot which can prevent injuries, such as finger entrapment between the wheel and the wheel well. 
     An autonomous mobile robot  100 , according an embodiment of this disclosure, is shown in  FIG.  1   . Mobile robot  100  includes a platform  102  for carrying items directly or for supporting a shelving unit or other form of tote and a mobile base  104 . The mobile robot may include a mast unit (not shown) for mounting a user input device, such as handheld computer like an ipad®. There is also an array of sensors  106  at the front of mobile base  104 , which may include laser radar (LIDAR) and vision cameras, used for navigation. Charging port  108  is included so the robot may autonomously dock at a charging station to recharge its batteries. Mobile base  104  also includes two removable wheel drive assemblies  110  and  112  (see  FIG.  2   ) on either side of the mobile base  104 . Caster wheels  114  and  116  at the front and rear, respectively, of the mobile base  104  are shown in  FIG.  2   . 
     One example of robot  100  is described in U.S. Pat. No. 10,019,015, for use in warehouse order fulfillment. The operation and application of robot  100  is not critical to the removable wheel drive assemblies described and claimed herein so they will not be described further. The removable wheel drive assemblies described and claimed herein may be used with various types of mobile robots designed for any suitable robot application. 
     Referring to  FIGS.  1  and  2   , mobile base  104  may include a frame or chassis  120  on which are mounted removable wheel drive assemblies  110  and  112  and caster wheels  114  and  116 . There is an exterior cover  122 , which may comprise a number of exterior cover components, including upper wheel well cover  131 , including leg portions  132   a  and  132   b,  which are interconnected by an arch portion  132   c.  Upper wheel well cover  131  forms part of upper wheel well member  132 , described below. Part of upper wheel well cover  131  disposed above leg portions  132   a  and  132   b  is label region  134 . Label region  134  may be used to display insignia, such as a logo or name/number associated with the robot. Lower wheel well cover portions  130   a  and  130   b  of wheel drive assembly  110 , mate with leg portions  132   a  and  132   b  of upper wheel well cover portion  131  when removable wheel drive assemblies  110  is installed. Together, these exterior cover components interconnect to form a part of the exterior cover  122 , as best shown in  FIG.  1   . 
     As shown in  FIG.  2   , removable wheel drive assembly  110 , includes mounting bracket  140  on which the components of the wheel drive assembly are mounted when installed within wheel drive region  124 . The mounting bracket  140  may be installed on mobile base  104  by means of fasteners (e.g. screws)  142   a - 142   d  inserted through holes  144   a - 144   d  in the bottom of mounting bracket  140  and secured in holes  146   a - 146   d  in frame member  126 . The bottom of mounting bracket  150  of removable wheel drive assembly  112  is shown in the installed position. Other components disposed on mounting bracket  140  include wheel  160  on which is mounted tire  162 . There is also included a motor drive unit  170 . 
     An advantage of using a standard mounting bracket, like mounting brackets  140 / 150 , is that it can provide standard mounting platform that is easily installable and removable on the robot base, but can support different motor drive assemblies. This allows for diversity of suppliers or for field replacement of an obsolete drive assembly with updated units not directly providing identical mounting features. In other words, the mounting plate can serve as an adapter. 
     Referring now to  FIG.  3   , a side perspective view of removable wheel drive assembly  110  is shown. In this view, motor drive unit  170  is shown to include an electric motor  172  integrated with a gear box unit  174 , which is interconnected to an axle (not shown). In turn, the axle is connected to the wheel  160  (also not shown in this view). Wheel drive assembly  110  is a right hand type drive with electric motor unit  172 , having a vertically oriented axis of rotation  176 , which at a right angle to the horizontally oriented axis of rotation  178  of the gear box unit  174 . While not a requirement of the wheel drive assembly disclosed herein, this type of drive unit is desirable as it is compact and readily mountable on mounting bracket  140 . 
     Continuing to refer to  FIG.  3    and to  FIGS.  4 A and  4 B , disposed on mounting bracket  140  is a lower wheel well member  180  positioned between gearbox  174  of the motor drive unit  170  and the wheel  160 /tire  162 . Wheel  160  is disposed on an axle (not shown) which passes through aperture  182  and connects gearbox  174  to wheel  160 . As described further below, upper wheel well member  132  mates with a lower wheel well member  180  on the removable wheel drive assembly  110  to form a sealed wheel well. The upper and lower wheel well member are designed to interconnect when removable wheel drive assembly  110  is mounted on mobile base  104  to form a seal to limit/prevent dust (and other matter) from entering the motor drive unit  170 , which may otherwise cause premature failure of motor drive unit  170 . The upper and lower wheel well members and external cover components also guard against safety issues, such as finger entrapment between wheel and wheel well. In addition to the connection between the upper and lower wheel well portions, the design also provides a minimized amount of clearance between the wheel well portions and the wheel  160  and tire  162 . 
     Referring to  FIGS.  5 A and  5 B , the minimized clearances between the wheel well members and the wheel  160  and tire  162  are depicted. Wheel well cover portion  130   a , which forms part of lower wheel well member  180 , is spaced a very small distance from tire  162 , forming a minimized gap  192 , as shown in  FIG.  5 A . In this example, the gap is approximately 3.5 mm from the tread surface  190  of tire  162 . This gap distance may be made smaller or larger, but typically gap  192  would be small enough to prevent insertion of a little (or “pinkie”) finger of a smaller sized person. 
     In  FIG.  5 B  a bottom plan view of lower wheel well member  180  is shown. In this view, the connection of the base  202  of wheel well member  180  to mounting bracket  140  via bolt  194  is shown. A very small gap, gap  196 , between the front surface  200  of wheel well portion  180  and the edge of tire tread surface  190  of tire  162  is shown. In this example, the gap is approximately 1.625 mm, but the typical size gap  196  would be small enough prevent insertion of a little (or “pinkie”) finger of a smaller sized person. 
     Turning back to  FIGS.  4 A and  4 B , the design of lower wheel well member  180  is further described. The remainder of the removable wheel drive assembly  110  (i.e. all but wheel well member  180 ) is shown in phantom in  FIGS.  4 A and  4 B , so the focus of these views and the description herein is on the wheel well member  180 . Lower wheel well member  180  includes a base portion  202 , which sits on and is connected to the mounting bracket  140  as indicated above with regard to  FIG.  5 B . While the wheel well portion  180  is a single integrated component, for description purposes only, it is described in sections, which are divided by broken lines in  FIG.  4 B . First, there is a central section  210  having an aperture  182  through which the axle (not shown) passes. Central section  210  has a curved or arched top surface  212 , which may be conformed to the curvature of wheel  160 /tire  162 . There is a first side section  214  extending in a first direction indicated by arrow  215  away from the central section  210 . There is a second side section  216  extending in a second direction indicated by arrow  217  away from the central section  216 . The second direction is opposite the first direction. 
     Extending from first side section  214 , in a direction perpendicular to front surface  200  (i.e. outwardly from the front surface), is a first curved fender  220 . First curved fender  220  has a curved surface  221 , which faces tread surface  190  of tire  162  and is in close proximity thereto, i.e. spaced by gap  192  of  FIG.  5 A . The curved surface  221  has a width approximately equal to the width of tread surface  190 . The curved surface  221  is conformed to the curvature of tread surface  190  of the tire  160 . 
     Extending from second side section  216 , in a direction perpendicular to front surface  200  (i.e. outwardly from the front surface), is a second curved fender  240 . Second curved fender  240  has a curved surface  241 , which faces tread surface  190  of tire  162  and is in close proximity thereto, i.e. spaced by gap  192  of  FIG.  5 A . Curved surface  241  has a width approximately equal to the width of tread surface  190 . Curved surface  241  is conformed to the curvature of tread surface  190  of the tire  160 . 
     Lower wheel well cover portions  130   a  and  130   b  of  FIGS.  1  and  2   , are described with respect to  FIGS.  4 A and  4 B . Lower wheel well cover portion  130   a  has a curved edge  250  affixed to and conforming with a curved edge of curved surface  221  of first fender  220 . The wheel well cover portion  130   a  extends from curved edge  250  in a direction parallel to arrow  215 . Wheel well cover portion  130   b  has a curved edge  252  affixed to and conforming with a curved edge of curved surface  241  of second curved fender  240 . Wheel well cover portion  130   b  extends from curved edge  252  in a direction parallel to arrow  217 . 
     As described further below with regard to  FIG.  6   , upper wheel well member  132  mates with a lower wheel well member  180  on the removable wheel drive assembly  110  to form a sealed wheel well when removable wheel drive assembly  110  is installed on wheeled base  104 . The upper and lower wheel well members are designed to interconnect when removable wheel drive assembly  110  is mounted on mobile base  104  in wheel drive region  124  to form a seal to limit/prevent dust (and other matter) from entering the motor drive unit  170 , which may otherwise cause premature failure of motor drive unit  170 . In addition, wheel well cover portions  130   a  and  130   b  of lower wheel well member  180  mate with leg portions  132   a  and  132   b  of upper wheel well portion  131  to form a sealed external cover portion about wheel drive region  124 . 
       FIG.  6    shows a front perspective view of upper wheel well member  132  mounted on mobile base  104  mated with lower wheel well member  180  on the removable wheel drive assembly  110 . In this view, wheel  160  and tire  162  are not depicted, so the engagement of upper and lower wheel well members may be clearly seen. Moreover, base portion  202  of lower wheel well member  180 , which is normally connected to mounting bracket  140  of wheel drive assembly  110 , is shown to be disconnected. This is also to more clearly depict the engagement of upper wheel well member  132  and lower wheel well member  180 . 
     Forming part of upper wheel well  132  is a thin arched flange member  300 , which is part of frame portion  302 . Frame portion  302  is part of the mobile base frame  120  shown in  FIG.  1   . Thus, upper wheel well member  132  comprises arched flange member  300  and upper wheel well portion  131 . Leg portions  132   a  and  132   c  and arch  132   c  define an inner surface  310 , which act as an upper fender for tire  162 . The inner surface  310  has a surface width approximately the same width as surfaces  221  and  241 , respectively, of first and second fenders  220  and  240 . Thus, together the first and second fenders  221  and  241  and surface  310  form a fender for tire  162  with a very small gap between the tire surface and the fender as shown in  FIG.  5 A . This design guards against safety issues, such as finger entrapment between wheel and wheel well. 
     When lower wheel well portion  180  is mated with upper wheel well portion  132 , curved or arched top surface  212  of central section  210  engages with complementarily curved/arched flange member  300 , together forming a closed or sealed surface bounded by fender surfaces  240 ,  241 , and  310 . The only opening in the surface is aperture  182  through which the axle for mounting wheel  160  is disposed. The region in which wheel  160  and tire  162  are mounted is sealed to limit/prevent dust (and other matter) from entering the motor drive unit  170 . 
     Various embodiments of the present invention may be characterized by the potential claims listed in the paragraphs following this paragraph (and before the actual claims provided at the end of this application). These potential claims form a part of the written description of this application. Accordingly, subject matter of the following potential claims may be presented as actual claims in later proceedings involving this application or any application claiming priority based on this application. Inclusion of such potential claims should not be construed to mean that the actual claims do not cover the subject matter of the potential claims. Thus, a decision to not present these potential claims in later proceedings should not be construed as a donation of the subject matter to the public. 
     The embodiments of the invention described above are intended to be merely exemplary; numerous variations and modifications will be apparent to those skilled in the art. All such variations and modifications are intended to be within the scope of the present invention as defined in any appended claims.