Abstract:
A floor-cleaning robot includes a wheeled housing having a perimeter, a motor drive operably connected to wheels of the housing to move the robot across a floor surface, and a bumper responsive to obstacles encountered by the robot. A controller is in electrical communication with both the bumper and the motor drive and is configured to control the motor drive to maneuver the robot to avoid detected obstacles across the floor surface during a floor-cleaning operation. A driven cleaning brush, rotatable about an axis substantially parallel to an underside of the housing, is disposed substantially across a central region of the underside and is positioned to brush the floor surface as the robot is moved across the floor surface. Additionally, a driven side brush extending beyond the perimeter is positioned to brush floor surface debris from beyond the perimeter toward a projected path of the driven cleaning brush.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application for U.S. patent is a continuation of U.S. patent application Ser. No. 12/201,554 filed Aug. 29, 2008, which is a division of U.S. patent application Ser. No. 10/818,073 filed Apr. 5, 2004, now U.S. Pat. No. 7,571,511, which is a continuation of U.S. patent application Ser. No. 10/320,729 filed Dec. 16, 2002, now U.S. Pat. No. 6,883,201, which claims the benefit of U.S. Provisional Application No. 60/345,764 filed on Jan. 3, 2002, the contents of all of which are expressly incorporated by reference herein in their entireties. The subject matter of this application is also related to commonly-owned U.S. patent application Ser. No. 09/768,773 filed Jan. 24, 2001, now U.S. Pat. No. 6,594,844, U.S. patent application Ser. No. 10/167,851 filed Jun. 12, 2002, now U.S. Pat. No. 6,809,490, and U.S. patent application Ser. No. 10/056,804 filed Jan. 24, 2002, U.S. Pat. No. 6,690,134, which are all expressly incorporated by reference herein in their entireties. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    (1) Field of the Invention 
         [0003]    The present invention relates to cleaning devices, and more particularly, to an autonomous floor-cleaning robot that comprises a self-adjustable cleaning head subsystem that includes a dual-stage brush assembly having counter-rotating, asymmetric brushes and an adjacent, but independent, vacuum assembly such that the cleaning capability and efficiency of the self-adjustable cleaning head subsystem is optimized while concomitantly minimizing the power requirements thereof. The autonomous floor-cleaning robot further includes a side brush assembly for directing particulates outside the envelope of the robot into the self-adjustable cleaning head subsystem. 
         [0004]    (2) Description of Related Art 
         [0005]    Autonomous robot cleaning devices are known in the art. For example, U.S. Pat. Nos. 5,940,927 and 5,781,960 disclose an Autonomous Surface Cleaning Apparatus and a Nozzle Arrangement for a Self-Guiding Vacuum Cleaner. One of the primary requirements for an autonomous cleaning device is a self-contained power supply—the utility of an autonomous cleaning device would be severely degraded, if not outright eliminated, if such an autonomous cleaning device utilized a power cord to tap into an external power source. 
         [0006]    And, while there have been distinct improvements in the energizing capabilities of self-contained power supplies such as batteries, today&#39;s self-contained power supplies are still time-limited in providing power. Cleaning mechanisms for cleaning devices such as brush assemblies and vacuum assemblies typically require large power loads to provide effective cleaning capability. This is particularly true where brush assemblies and vacuum assemblies are configured as combinations, since the brush assembly and/or the vacuum assembly of such combinations typically have not been designed or configured for synergic operation. 
         [0007]    A need exists to provide an autonomous cleaning device that has been designed and configured to optimize the cleaning capability and efficiency of its cleaning mechanisms for synergic operation while concomitantly minimizing or reducing the power requirements of such cleaning mechanisms. 
       SUMMARY OF THE INVENTION 
       [0008]    One object of the present invention is to provide a cleaning device that is operable without human intervention to clean designated areas. 
         [0009]    Another object of the present invention is to provide such an autonomous cleaning device that is designed and configured to optimize the cleaning capability and efficiency of its cleaning mechanisms for synergic operations while concomitantly minimizing the power requirements of such mechanisms. 
         [0010]    These and other objects of the present invention are provided by one embodiment autonomous floor-cleaning robot according to the present invention that comprises a housing infrastructure including a chassis, a power subsystem; for providing the energy to power the autonomous floor-cleaning robot, a motive subsystem operative to propel the autonomous floor-cleaning robot for cleaning operations, a control module operative to control the autonomous floor-cleaning robot to effect cleaning operations, and a self-adjusting cleaning head subsystem that includes a deck mounted in pivotal combination with the chassis, a brush assembly mounted in combination with the deck and powered by the motive subsystem to sweep up particulates during cleaning operations, a vacuum assembly disposed in combination with the deck and powered by the motive subsystem to ingest particulates during cleaning operations, and a deck height adjusting subassembly mounted in combination with the motive subsystem for the brush assembly, the deck, and the chassis that is automatically operative in response to a change in torque in said brush assembly to pivot the deck with respect to said chassis and thereby adjust the height of the brushes from the floor. The autonomous floor-cleaning robot also includes a side brush assembly mounted in combination with the chassis and powered by the motive subsystem to entrain particulates outside the periphery of the housing infrastructure and to direct such particulates towards the self-adjusting cleaning head subsystem. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    A more complete understanding of the present invention and the attendant features and advantages thereof may be had by reference to the following detailed description of the invention when considered in conjunction with the accompanying drawings wherein: 
           [0012]      FIG. 1  is a schematic representation of an autonomous floor-cleaning robot according to the present invention. 
           [0013]      FIG. 2  is a perspective view of one embodiment of an autonomous floor-cleaning robot according to the present invention. 
           [0014]      FIG. 2A  is a bottom plan view of the autonomous floor-cleaning robot of  FIG. 2 . 
           [0015]      FIG. 3A  is a top, partially-sectioned plan view, with cover removed, of another embodiment of an autonomous floor-cleaning robot according to the present invention. 
           [0016]      FIG. 3B  is a bottom, partially-section plan view of the autonomous floor-cleaning robot embodiment of  FIG. 3A . 
           [0017]      FIG. 3C  is a side, partially sectioned plan view of the autonomous floor-cleaning robot embodiment of  FIG. 3A . 
           [0018]      FIG. 4A  is a top plan view of the deck and chassis of the autonomous floor-cleaning robot embodiment of  FIG. 3A . 
           [0019]      FIG. 4B  is a cross-sectional view of  FIG. 4A  taken along line B-B thereof. 
           [0020]      FIG. 4C  is a perspective view of the deck-adjusting subassembly of autonomous floor-cleaning robot embodiment of  FIG. 3A . 
           [0021]      FIG. 5A  is a first exploded perspective view of a dust cartridge for the autonomous floor-cleaning robot embodiment of  FIG. 3A . 
           [0022]      FIG. 5B  is a second exploded perspective view of the dust cartridge of  FIG. 5A . 
           [0023]      FIG. 6  is a perspective view of a dual-stage brush assembly including a flapper brush and a main brush for the autonomous floor-cleaning robot embodiment of  FIG. 3A . 
           [0024]      FIG. 7A  is a perspective view illustrating the blades and vacuum compartment for the autonomous floor cleaning robot embodiment of  FIG. 3A . 
           [0025]      FIG. 7B  is a partial perspective exploded view of the autonomous floor-cleaning robot embodiment of  FIG. 7A . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0026]    Referring now to the drawings where like reference numerals identify corresponding or similar elements throughout the several views,  FIG. 1  is a schematic representation of an autonomous floor-cleaning robot  10  according to the present invention. The robot  10  comprises a housing infrastructure  20 , a power subsystem  30 , a motive subsystem  40 , a sensor subsystem  50 , a control module  60 , a side brush assembly  70 , and a self-adjusting cleaning head subsystem  80 . The power subsystem  30 , the motive subsystem  40 , the sensor subsystem  50 , the control module  60 , the side brush assembly  70 , and the self-adjusting cleaning head subsystem  80  are integrated in combination with the housing infrastructure  20  of the robot  10  as described in further detail in the following paragraphs. 
         [0027]    In the following description of the autonomous floor-cleaning robot  10 , use of the terminology “forward/fore” refers to the primary direction of motion of the autonomous floor-cleaning robot  10 , and the terminology fore-aft axis (see reference characters “FA” in  FIGS. 3A ,  3 B) defines the forward direction of motion (indicated by arrowhead of the fore-aft axis FA), which is coincident with the fore-aft diameter of the robot  10 . 
         [0028]    Referring to  FIGS. 2 ,  2 A, and  3 A- 3 C, the housing infrastructure  20  of the robot  10  comprises a chassis  21 , a cover  22 , a displaceable bumper  23 , a nose wheel subassembly  24 , and a carrying handle  25 . The chassis  21  is preferably molded from a material such as plastic as a unitary element that includes a plurality of preformed wells, recesses, and structural members for, inter alia, mounting or integrating elements of the power subsystem  30 , the motive subsystem  40 , the sensor subsystem  50 , the side brush assembly  70 , and the self-adjusting cleaning head subsystem  80  in combination with the chassis  21 . The cover  22  is preferably molded from a material such as plastic as a unitary element that is complementary in configuration with the chassis  21  and provides protection of and access to elements/components mounted to the chassis  21  and/or comprising the self-adjusting cleaning head subsystem  80 . The chassis  21  and the cover  22  are detachably integrated in combination by any suitable means, e.g., screws, and in combination, the chassis  21  and cover  22  form a structural envelope of minimal height having a generally cylindrical configuration that is generally symmetrical along the fore-aft axis FA. 
         [0029]    The displaceable bumper  23 , which has a generally arcuate configuration, is mounted in movable combination at the forward portion of the chassis  21  to extend outwardly therefrom, i.e., the normal operating position. The mounting configuration of the displaceable bumper is such that the bumper  23  is displaced towards the chassis  21  (from the normal operating position) whenever the bumper  23  encounters a stationary object or obstacle of predetermined mass, i.e., the displaced position, and returns to the normal operating position when contact with the stationary object or obstacle is terminated (due to operation of the control module  60  which, in response to any such displacement of the bumper  23 , implements a “bounce” mode that causes the robot  10  to evade the stationary object or obstacle and continue its cleaning routine, e.g., initiate a random—or weighted-random—turn to resume forward movement in a different direction). The mounting configuration of the displaceable bumper  23  comprises a pair of rotatable support members  23 RSM, which are operative to facilitate the movement of the bumper  23  with respect to the chassis  21 . 
         [0030]    The pair of rotatable support members  23 RSM are symmetrically mounted about the fore-aft axis FA of the autonomous floor-cleaning robot  10  proximal the center of the displaceable bumper  23  in a V-configuration. One end of each support member  23 RSM is rotatably mounted to the chassis  21  by conventional means, e.g., pins/dowel and sleeve arrangement, and the other end of each support member  23 RSM is likewise rotatably mounted to the displaceable bumper  23  by similar conventional means. A biasing spring (not shown) is disposed in combination with each rotatable support member  23 RSM and is operative to provide the biasing force necessary to return the displaceable bumper  23  (through rotational movement of the support members  23 RSM) to the normal operating position whenever contact with a stationary object or obstacle is terminated. 
         [0031]    The embodiment described herein includes a pair of bumper arms  23 BA that are symmetrically mounted in parallel about the fore-aft diameter FA of the autonomous floor-cleaning robot  10  distal the center of the displaceable bumper  23 . These bumper arms  23 BA do not per se provide structural support for the displaceable bumper  23 , but rather are a part of the sensor subsystem  50  that is operative to determine the location of a stationary object or obstacle encountered via the bumper  23 . One end of each bumper arm  23 BA is rigidly secured to the displaceable bumper  23  and the other end of each bumper arm  23 BA is mounted in combination with the chassis  21  in a manner, e.g., a slot arrangement such that, during an encounter with a stationary object or obstacle, one or both bumper arms  23 BA are linearly displaceable with respect to the chassis  21  to activate an associated sensor, e.g., IR break beam sensor, mechanical switch, capacitive sensor, which provides a corresponding signal to the control module  60  to implement the “bounce” mode. Further details regarding the operation of this aspect of the sensor subsystem  50 , as well as alternative embodiments of sensors having utility in detecting contact with or proximity to stationary objects or obstacles can be found in commonly-owned, co-pending U.S. patent application Ser. No. 10/056,804, filed 24 Jan. 2002, entitled Method and System for Multi-Mode Coverage for an Autonomous Robot. 
         [0032]    The nose-wheel subassembly  24  comprises a wheel  24 W rotatably mounted in combination with a clevis member  24 CM that includes a mounting shaft. The clevis mounting shaft  24 CM is disposed in a well in the chassis  21  at the forward end thereof on the fore-aft diameter of the autonomous floor-cleaning robot  10 . A biasing spring  24 BS (hidden behind a leg of the clevis member  24 CM in  FIG. 3C ) is disposed in combination with the clevis mounting shaft  24 CM and operative to bias the nose-wheel subassembly  24  to an ‘extended’ position whenever the nose-wheel subassembly  24  loses contact with the surface to be cleaned. During cleaning operations, the weight of the autonomous floor-cleaning robot  10  is sufficient to overcome the force exerted by the biasing spring  24 BS to bias the nose-wheel subassembly  24  to a partially retracted or operating position wherein the wheel rotates freely over the surface to be cleaned. Opposed triangular or conical wings  24 TW extend outwardly from the ends of the clevis member to prevent the side of the wheel from catching on low obstacle during turning movements of the autonomous floor-cleaning robot  10 . The wings  24 TW act as ramps in sliding over bumps as the robot turns. 
         [0033]    Ends  25 E of the carrying handle  25  are secured in pivotal combination with the cover  22  at the forward end thereof, centered about the fore-aft axis FA of the autonomous floor-cleaning robot  10 . With the autonomous floor-cleaning robot  10  resting on or moving over a surface to be cleaned, the carrying handle  25  lies approximately flush with the surface of the cover  22  (the weight of the carrying handle  25 , in conjunction with arrangement of the handle-cover pivot configuration, is sufficient to automatically return the carrying handle  25  to this flush position due to gravitational effects). When the autonomous floor-cleaning robot  10  is picked up by means of the carrying handle  25 , the aft end of the autonomous floor-cleaning robot  10  lies below the forward end of the autonomous floor-cleaning robot  10  so that particulate debris is not dislodged from the self-adjusting cleaning head subsystem  80 . 
         [0034]    The power subsystem  30  of the described embodiment provides the energy to power individual elements/components of the motive subsystem  40 , the sensor subsystem  50 , the side brush assembly  70 , and the self-adjusting cleaning head subsystem  80  and the circuits and components of the control module  60  via associated circuitry  32 - 4 ,  32 - 5 ,  32 - 7 ,  32 - 8 , and  32 - 6 , respectively (see  FIG. 1 ) during cleaning operations. The power subsystem  30  for the described embodiment of the autonomous floor-cleaning robot  10  comprises a rechargeable battery pack  34  such as a NiMH battery pack. The rechargeable battery pack  34  is mounted in a well formed in the chassis  21  (sized specifically for mounting/retention of the battery pack  34 ) and retained therein by any conventional means, e.g., spring latches (not shown). The battery well is covered by a lid  34 L secured to the chassis  21  by conventional means such as screws. Affixed to the lid  34 L are friction pads  36  that facilitate stopping of the autonomous floor-cleaning robot  10  during automatic shutdown. The friction pads  36  aid in stopping the robot upon the robot&#39;s attempting to drive over a cliff. The rechargeable battery pack  34  is configured to provide sufficient power to run the autonomous floor-cleaning robot  10  for a period of sixty (60) to ninety (90) minutes on a full charge while meeting the power requirements of the elements/components comprising motive subsystem  40 , the sensor subsystem  50 , the side brush assembly  70 , the self-adjusting cleaning head subsystem  80 , and the circuits and components of the control module  60 . 
         [0035]    The motive subsystem  40  comprises the independent means that: (1) propel the autonomous floor-cleaning robot  10  for cleaning operations; (2) operate the side brush assembly  70 ; and (3) operate the self-adjusting cleaning head subsystem  80  during such cleaning operations. Such independent means includes right and left main wheel subassemblies  42 A,  42 B, each subassembly  42 A,  42 B having its own independently-operated motor  42 A M ,  42 B M , respectively, an independent electric motor  44  for the side brush assembly  70 , and two independent electric motors  46 ,  48  for the self-adjusting brush subsystem  80 , one motor  46  for the vacuum assembly and one motor  48  for the dual-stage brush assembly. 
         [0036]    The right and left main wheel subassemblies  42 A,  42 B are independently mounted in wells of the chassis  21  formed at opposed ends of the transverse diameter of the chassis  21  (the transverse diameter is perpendicular to the fore-aft axis FA of the robot  10 ). Mounting at this location provides the autonomous floor-cleaning robot  10  with an enhanced turning capability, since the main wheel subassemblies  42 A,  42 B motor can be independently operated to effect a wide range of turning maneuvers, e.g., sharp turns, gradual turns, turns in place. 
         [0037]    Each main wheel subassembly  42 A,  42 B comprises a wheel  42 A W ,  42 B W  rotatably mounted in combination with a clevis member  42 A CM ,  42 B CM . Each clevis member  42 A CM ,  42 B CM  is pivotally mounted to the chassis  21  aft of the wheel axis of rotation (see  FIG. 3C  which illustrates the wheel axis of rotation  42 A AR ; the wheel axis of rotation for wheel subassembly  42 B, which is not shown, is identical), i.e., independently suspended. The aft pivot axis  42 A PA ,  42 B PA  (see  FIG. 3A ) of the main wheel subassemblies  42 A,  42 B facilitates the mobility of the autonomous floor-cleaning robot  10 , i.e., pivotal movement of the subassemblies  42 A,  42 B through a predetermined arc. The motor  42 A M ,  42 B M  associated with each main wheel subassembly  42 A,  42 B is mounted to the aft end of the clevis member  42 A CM ,  42 B CM . One end of a tension spring  42 B TS  (the tension spring for the right wheel subassembly  42 A is not illustrated, but is identical to the tension spring  42 BTS of the left wheel subassembly  42 A) is attached to the aft portion of the clevis member  42 B CM  and the other end of the tension spring  42 B TS  is attached to the chassis  21  forward of the respective wheel  42 A W ,  42  B W . 
         [0038]    Each tension spring is operative to rotatably bias the respective main wheel subassembly  42 A,  42 B (via pivotal movement of the corresponding clevis member  42 A CM ,  42 B CM  through the predetermined arc) to an ‘extended’ position when the autonomous floor-cleaning robot  10  is removed from the floor (in this ‘extended’ position the wheel axis of rotation lies below the bottom plane of the chassis  21 ). With the autonomous floor-cleaning robot  10  resting on or moving over a surface to be cleaned, the weight of autonomous floor-cleaning robot  10  gravitationally biases each main wheel subassembly  42 A,  42 B into a retracted or operating position wherein axis of rotation of the wheels are approximately coplanar with bottom plane of the chassis  21 . The motors  42 A M ,  42 B M  of the main wheel subassemblies  42 A,  42 B are operative to drive the main wheels: (1) at the same speed in the same direction of rotation to propel the autonomous floor-cleaning robot  10  in a straight line, either forward or aft; (2) at different speeds (including the situation wherein one wheel is operated at zero speed) to effect turning patterns for the autonomous floor-cleaning robot  10 ; or (3) at the same speed in opposite directions of rotation to cause the robot  10  to turn in place, i.e., “spin on a dime”. 
         [0039]    The wheels  42 A W ,  42 B W  of the main wheel subassemblies  42 A,  42 B preferably have a “knobby” tread configuration  42 A KT ,  42 B KT . This knobby tread configuration  42 A KT ,  42 B KT  provides the autonomous floor-cleaning robot  10  with enhanced traction, particularly when traversing smooth surfaces and traversing between contiguous surfaces of different textures, e.g., bare floor to carpet or vice versa. This knobby tread configuration  42 A KT ,  42 B KT  also prevents tufted fabric of carpets/rags from being entrapped in the wheels  42 A W ,  42 B and entrained between the wheels and the chassis  21  during movement of the autonomous floor-cleaning robot  10 . One skilled in the art will appreciate, however, that other tread patterns/configurations are within the scope of the present invention. 
         [0040]    The sensor subsystem  50  comprises a variety of different sensing units that may be broadly characterized as either: (1) control sensing units  52 ; or (2) emergency sensing units  54 . As the names imply, control sensing units  52  are operative to regulate the normal operation of the autonomous floor-cleaning robot  10  and emergency sensing units  54  are operative to detect situations that could adversely affect the operation of the autonomous floor-cleaning robot  10  (e.g., stairs descending from the surface being cleaned) and provide signals in response to such detections so that the autonomous floor-cleaning robot  10  can implement an appropriate response via the control module  60 . The control sensing units  52  and emergency sensing units  54  of the autonomous floor-cleaning robot  10  are summarily described in the following paragraphs; a more complete description can be found in commonly-owned, co-pending U.S. patent application Ser. Nos. 09/768,773, filed 24 Jan. 2001, entitled Robot Obstacle Detection System, 10/167,851, 12 Jun. 2002, entitled Method and System for Robot Localization and Confinement, and 10/056,804, filed 24 Jan. 2002, entitled Method and System for Multi-Mode Coverage for an Autonomous Robot. 
         [0041]    The control sensing units  52  include obstacle detection sensors  52 OD mounted in conjunction with the linearly-displaceable bumper arms  23 BA of the displaceable bumper  23 , a wall-sensing assembly  52 WS mounted in the right-hand portion of the displaceable bumper  23 , a virtual wall sensing assembly  52 VWS mounted atop the displaceable bumper  23  along the fore-aft diameter of the autonomous floor-cleaning robot  10 , and an IR sensor/encoder combination  52 WE mounted in combination with each wheel subassembly  42 A,  42 B. 
         [0042]    Each obstacle detection sensor  52 OD includes an emitter and detector combination positioned in conjunction with one of the linearly displaceable bumper arms  23 BA so that the sensor  52 OD is operative in response to a displacement of the bumper arm  23 BA to transmit a detection signal to the control module  60 . The wall sensing assembly  52 WS includes an emitter and detector combination that is operative to detect the proximity of a wall or other similar structure and transmit a detection signal to the control module  60 . Each IR sensor/encoder combination  52 WE is operative to measure the rotation of the associated wheel subassembly  42 A,  42 B and transmit a signal corresponding thereto to the control module  60 . 
         [0043]    The virtual wall sensing assembly  52 VWS includes detectors that are operative to detect a force field and a collimated beam emitted by a stand-alone emitter (the virtual wall unit—not illustrated) and transmit respective signals to the control module  60 . The autonomous floor cleaning robot  10  is programmed not to pass through the collimated beam so that the virtual wall unit can be used to prevent the robot  10  from entering prohibited areas, e.g., access to a descending staircase, room not to be cleaned. The robot  10  is further programmed to avoid the force field emitted by the virtual wall unit, thereby preventing the robot  10  from overrunning the virtual wall unit during floor cleaning operations. 
         [0044]    The emergency sensing units  54  include ‘cliff detector’ assemblies  54 CD mounted in the displaceable bumper  23 , wheeldrop assemblies  54 WD mounted in conjunction with the left and right main wheel subassemblies  42 A,  42 B and the nose-wheel assembly  24 , and current stall sensing units  54 CS for the motor  42 A M ,  42 B M  of each main wheel subassembly  42 A,  42 B and one for the motors  44 ,  48  (these two motors are powered via a common circuit in the described embodiment). For the described embodiment of the autonomous floor-cleaning robot  10 , four (4) cliff detector assemblies  54 CD are mounted in the displaceable bumper  23 . Each cliff detector assembly  54 CD includes an emitter and detector combination that is operative to detect a predetermined drop in the path of the robot  10 , e.g., descending stairs, and transmit a signal to the control module  60 . The wheeldrop assemblies  54 WD are operative to detect when the corresponding left and right main wheel subassemblies  32 A,  32 B and/or the nose-wheel assembly  24  enter the extended position, e.g., a contact switch, and to transmit a corresponding signal to the control module  60 . The current stall sensing units  54 CS are operative to detect a change in the current in the respective motor, which indicates a stalled condition of the motor&#39;s corresponding components, and transmit a corresponding signal to the control module  60 . 
         [0045]    The control module  60  comprises the control circuitry (see, e.g., control lines  60 - 4 ,  60 - 5 ,  60 - 7 , and  60 - 8  in  FIG. 1 ) and microcontroller for the autonomous floor-cleaning robot  10  that controls the movement of the robot  10  during floor cleaning operations and in response to signals generated by the sensor subsystem  50 . The control module  60  of the autonomous floor-cleaning robot  10  according to the present invention is preprogrammed (hardwired, software, firmware, or combinations thereof) to implement three basic operational modes, i.e., movement patterns, that can be categorized as: (1) a “spot-coverage” mode; (2) a “wall/obstacle following” mode; and (3) a “bounce” mode. In addition, the control module  60  is preprogrammed to initiate actions based upon signals received from sensor subsystem  50 , where such actions include, but are not limited to, implementing movement patterns (2) and (3), an emergency stop of the robot  10 , or issuing an audible alert. Further details regarding the operation of the robot  10  via the control module  60  are described in detail in commonly-owned, co-pending U.S. patent application Ser. Nos. 09/768,773, filed 24 Jan. 2001, entitled Robot Obstacle Detection System, 10/167,851, filed 12 Jun. 2002, entitled Method and System for Robot Localization and Confinement, and 10/056,804, filed 24 Jan. 2002, entitled Method and System for Multi-Mode Coverage for an Autonomous Robot. 
         [0046]    The side brush assembly  70  is operative to entrain macroscopic and microscopic particulates outside the periphery of the housing infrastructure  20  of the autonomous floor-cleaning robot  10  and to direct such particulates towards the self-adjusting cleaning head subsystem  80 . This provides the robot  10  with the capability of cleaning surfaces adjacent to baseboards (during the wall-following mode). 
         [0047]    The side brush assembly  70  is mounted in a recess formed in the lower surface of the right forward quadrant of the chassis  21  (forward of the right main wheel subassembly  42 A just behind the right hand end of the displaceable bumper  23 ). The side brush assembly  70  comprises a shaft  72  having one end rotatably connected to the electric motor  44  for torque transfer, a hub  74  connected to the other end of the shaft  72 , a cover plate  75  surrounding the hub  74 , a brush means  76  affixed to the hub  74 , and a set of bristles  78 . 
         [0048]    The cover plate  75  is configured and secured to the chassis  21  to encompass the hub  74  in a manner that prevents the brush means  76  from becoming stuck under the chassis  21  during floor cleaning operations. 
         [0049]    For the embodiment of  FIGS. 3A-3C , the brush means  76  comprises opposed brush arms that extend outwardly from the hub  74 . These brush arms  76  are formed from a compliant plastic or rubber material in an “L”/hockey stick configuration of constant width. The configuration and composition of the brush arms  76 , in combination, allows the brush arms  76  to resiliently deform if an obstacle or obstruction is temporarily encountered during cleaning operations. Concomitantly, the use of opposed brush arms  76  of constant width is a trade-off (versus using a full or partial circular brush configuration) that ensures that the operation of the brush means  76  of the side brush assembly  70  does not adversely impact (i.e., by occlusion) the operation of the adjacent cliff detector subassembly  54 CD (the left-most cliff detector subassembly  54 CD in  FIG. 3B ) in the displaceable bumper  23 . The brush arms  76  have sufficient length to extend beyond the outer periphery of the autonomous floor-cleaning robot  10 , in particular the displaceable bumper  23  thereof. Such a length allows the autonomous floor-cleaning robot  10  to clean surfaces adjacent to baseboards (during the wall-following mode) without scrapping of the wall/baseboard by the chassis  21  and/or displaceable bumper  23  of the robot  10 . 
         [0050]    The set of bristles  78  is set in the outermost free end of each brush arm  76  (similar to a toothbrush configuration) to provide the sweeping capability of the side brush assembly  70 . The bristles  78  have a length sufficient to engage the surface being cleaned with the main wheel subassemblies  42 A,  42 B and the nose-wheel subassembly  24  in the operating position. 
         [0051]    The self-adjusting cleaning head subsystem  80  provides the cleaning mechanisms for the autonomous floor-cleaning robot  10  according to the present invention. The cleaning mechanisms for the preferred embodiment of the self-adjusting cleaning head subsystem  80  include a brush assembly  90  and a vacuum assembly  100 . 
         [0052]    For the described embodiment of  FIGS. 3A-3C , the brush assembly  90  is a dual-stage brush mechanism, and this dual-stage brush assembly  90  and the vacuum assembly  100  are independent cleaning mechanisms, both structurally and functionally, that have been adapted and designed for use in the robot  10  to minimize the over-all power requirements of the robot  10  while simultaneously providing an effective cleaning capability. In addition to the cleaning mechanisms described in the preceding paragraph, the self-adjusting cleaning subsystem  80  includes a deck structure  82  pivotally coupled to the chassis  21 , an automatic deck adjusting subassembly  84 , a removable dust cartridge  86 , and one or more bails  88  shielding the dual-stage brush assembly  90 . 
         [0053]    The deck  82  is preferably fabricated as a unitary structure from a material such as plastic and includes opposed, spaced-apart sidewalls  82 SW formed at the aft end of the deck  82  (one of the sidewalls  82 SW comprising a U-shaped structure that houses the motor  46 , a brush-assembly well  82 W, a lateral aperture  82 LA formed in the intermediate portion of the lower deck surface, which defines the opening between the dual-stage brush assembly  90  and the removable dust cartridge  86 , and mounting brackets  82 MB formed in the forward portion of the upper deck surface for the motor  48 . 
         [0054]    The sidewalls  82 SW are positioned and configured for mounting the deck  82  in pivotal combination with the chassis  21  by a conventional means, e.g., a revolute joint (see reference characters  82 RJ in  FIG. 3A ). The pivotal axis of the deck  82 -chassis  21  combination is perpendicular to the fore-aft axis FA of the autonomous floor-cleaning robot  10  at the aft end of the robot  10  (see reference character  82   PA  which identifies the pivotal axis in  FIG. 3A ). 
         [0055]    The mounting brackets  82 MB are positioned and configured for mounting the constant-torque motor  48  at the forward lip of the deck  82 . The rotational axis of the mounted motor  48  is perpendicular to the fore-aft diameter of the autonomous floor-cleaning robot  10  (see reference character  48 RA which identifies the rotational axis of the motor  48  in  FIG. 3A ). Extending from the mounted motor  48  is an shaft  48 S for transferring the constant torque to the input side of a stationary, conventional dual-output gearbox  48 B (the housing of the dual-output gearbox  48 B is fabricated as part of the deck  82 ). 
         [0056]    The desk adjusting subassembly  84 , which is illustrated in further detail in  FIGS. 4A-4C , is mounted in combination with the motor  48 , the deck  82  and the chassis  21  and operative, in combination with the electric motor  48 , to provide the physical mechanism and motive force, respectively, to pivot the deck  82  with respect to the chassis  21  about pivotal axis  82   PA  whenever the dual-stage brush assembly  90  encounters a situation that results in a predetermined reduction in the rotational speed of the dual-stage brush assembly  90 . This situation, which most commonly occurs as the autonomous floor-cleaning robot  10  transitions between a smooth surface such as a floor and a carpeted surface, is characterized as the ‘adjustment mode’ in the remainder of this description. 
         [0057]    The deck adjusting subassembly  84  for the described embodiment of  FIG. 3A  includes a motor cage  84 MC, a pulley  84 P, a pulley cord  84 C, an anchor member  84 AM, and complementary cage stops  84 CS. The motor  48  is non-rotatably secured within the motor cage  84 MC and the motor cage  84 MC is mounted in rotatable combination between the mounting brackets  82 MB. The pulley  84 P is fixedly secured to the motor cage  84 MC on the opposite side of the interior mounting bracket  82 MB in such a manner that the shaft  48 S of the motor  48  passes freely through the center of the pulley  84 P. The anchor member  84 AM is fixedly secured to the top surface of the chassis  21  in alignment with the pulley  84 P. 
         [0058]    One end of the pulley cord  84 C is secured to the anchor member  84 AM and the other end is secured to the pulley  84 P in such a manner, that with the deck  82  in the ‘down’ or non-pivoted position, the pulley cord  84 C is tensioned. One of the cage stops  84 CS is affixed to the motor cage  84 MC; the complementary cage stop  84 CS is affixed to the deck  82 . The complementary cage stops  84 CS are in abutting engagement when the deck  82  is in the ‘down’ position during normal cleaning operations due to the weight of the self-adjusting cleaning head subsystem  80 . 
         [0059]    During normal cleaning operations, the torque generated by the motor  48  is transferred to the dual-stage brush subassembly  90  by means of the shaft  48 S through the dual-output gearbox  48 B. The motor cage assembly is prevented from rotating by the counter-acting torque generated by the pulley cord  84 C on the pulley  84 P. When the resistance encountered by the rotating brushes changes, the deck height will be adjusted to compensate for it. If for example, the brush torque increases as the machine rolls from a smooth floor onto a carpet, the torque output of the motor  48  will increase. In response to this, the output torque of the motor  48  will increase. This increased torque overcomes the counter-acting torque exerted by the pulley cord  84 C on the pulley  84 P. This causes the pulley  84 P to rotate, effectively pulling itself up the pulley cord  84 C. This in turn, pivots the deck about the pivot axis, raising the brushes, reducing the friction between the brushes and the floor, and reducing the torque required by the dual-stage brush subassembly  90 . This continues until the torque between the motor  48  and the counter-acting torque generated by the pulley cord  84 C on the pulley  84 P are once again in equilibrium and a new deck height is established. 
         [0060]    In other words, during the adjustment mode, the foregoing torque transfer mechanism is interrupted since the shaft  48 S is essentially stationary. This condition causes the motor  48  to effectively rotate about the shaft  48 S. Since the motor  48  is non-rotatably secured to the motor cage  84 MC, the motor cage  84 MC, and concomitantly, the pulley  84 P, rotate with respect to the mounting brackets  82 MB. The rotational motion imparted to the pulley  84 P causes the pulley  84 P to ‘climb up’ the pulley cord  84 PC towards the anchor member  84 AM. Since the motor cage  84 MC is effectively mounted to the forward lip of the deck  82  by means of the mounting brackets  82 MB, this movement of the pulley  84 P causes the deck  82  to pivot about its pivot axis  82 PA to an “up” position (see  FIG. 4C ). This pivoting motion causes the forward portion of the deck  82  to move away from surface over which the autonomous floor-cleaning robot is traversing. 
         [0061]    Such pivotal movement, in turn, effectively moves the dual-stage brush assembly  90  away from the surface it was in contact with, thereby permitting the dual-stage brush assembly  90  to speed up and resume a steady-state rotational speed (consistent with the constant torque transferred from the motor  48 ). At this juncture (when the dual-stage brush assembly  90  reaches its steady-state rotational speed), the weight of the forward edge of the deck  82  (primarily the motor  48 ), gravitationally biases the deck  82  to pivot back to the ‘down’ or normal state, i.e., planar with the bottom surface of the chassis  21 , wherein the complementary cage stops  84 CS are in abutting engagement. 
         [0062]    While the deck adjusting subassembly  84  described in the preceding paragraphs is the preferred pivoting mechanism for the autonomous floor-cleaning robot  10  according to the present invention, one skilled in the art will appreciate that other mechanisms can be employed to utilize the torque developed by the motor  48  to induce a pivotal movement of the deck  82  in the adjustment mode. For example, the deck adjusting subassembly could comprise a spring-loaded clutch mechanism such as that shown in  FIG. 4C  (identified by reference characters SLCM) to pivot the deck  82  to an “up” position during the adjustment mode, or a centrifugal clutch mechanism or a torque-limiting clutch mechanism. In other embodiments, motor torque can be used to adjust the height of the cleaning head by replacing the pulley with a cam and a constant force spring or by replacing the pulley with a rack and pinion, using either a spring or the weight of the cleaning head to generate the counter-acting torque. 
         [0063]    The removable dust cartridge  86  provides temporary storage for macroscopic and microscopic particulates swept up by operation of the dual-stage brush assembly  90  and microscopic particulates drawn in by the operation of the vacuum assembly  100 . The removable dust cartridge  86  is configured as a dual chambered structure, having a first storage chamber  86 SC 1  for the macroscopic and microscopic particulates swept up by the dual-stage brush assembly  90  and a second storage chamber  86 SC 2  for the microscopic particulates drawn in by the vacuum assembly  100 . The removable dust cartridge  86  is further configured to be inserted in combination with the deck  82  so that a segment of the removable dust cartridge  86  defines part of the rear external sidewall structure of the autonomous floor-cleaning robot  10 . 
         [0064]    As illustrated in  FIGS. 5A-5B , the removable dust cartridge  86  comprises a floor member  86 FM and a ceiling member  86 CM joined together by opposed sidewall members  86 SW. The floor member  86 FM and the ceiling member  86 CM extend beyond the sidewall members  86 SW to define an open end  86 OE, and the free end of the floor member  86 FM is slightly angled and includes a plurality of baffled projections  86 AJ to remove debris entrained in the brush mechanisms of the dual-stage brush assembly  90 , and to facilitate insertion of the removable dust cartridge  86  in combination with the deck  82  as well as retention of particulates swept into the removable dust cartridge  86 . A backwall member  86 BW is mounted between the floor member  86 FM and the ceiling member  86 CM distal the open end  86 OE in abutting engagement with the sidewall members  86 SW. The backwall member  86 BW has an baffled configuration for the purpose of deflecting particulates angularly therefrom to prevent particulates swept up by the dual-stage brush assembly  90  from ricocheting back into the brush assembly  90 . The floor member  86 FM, the ceiling member  86 CM, the sidewall members  86 SW, and the backwall member  86 BW in combination define the first storage chamber  86 SC 1 . 
         [0065]    The removable dust cartridge  86  further comprises a curved arcuate member  86 CAM that defines the rear external sidewall structure of the autonomous floor-cleaning robot  10 . The curved arcuate member  86 CAM engages the ceiling member  86 CM, the floor member  86 F and the sidewall members  86 SW. There is a gap formed between the curved arcuate member  86 CAM and one sidewall member  86 SW that defines a vacuum inlet  86 VI for the removable dust cartridge  86 . A replaceable filter  86 RF is configured for snap fit insertion in combination with the floor member  86 FM. The replaceable filter  86 RF, the curved arcuate member  86 CAM, and the backwall member  86 BW in combination define the second storage chamber  86 SC 1 . 
         [0066]    The removable dust cartridge  86  is configured to be inserted between the opposed spaced-apart sidewalls  82 SW of the deck  82  so that the open end of the removable dust cartridge  86  aligns with the lateral aperture  82 LA formed in the deck  82 . Mounted to the outer surface of the ceiling member  86 CM is a latch member  86 LM, which is operative to engage a complementary shoulder formed in the upper surface of the deck  82  to latch the removable dust cartridge  86  in integrated combination with the deck  82 . 
         [0067]    The bail  88  comprises one or more narrow gauge wire structures that overlay the dual-stage brush assembly  90 . For the described embodiment, the bail  88  comprises a continuous narrow gauge wire structure formed in a castellated configuration, i.e., alternating open-sided rectangles. Alternatively, the bail  88  may comprise a plurality of single, open-sided rectangles formed from narrow gauge wire. The bail  88  is designed and configured for press fit insertion into complementary retaining grooves  88 A,  88 B, respectively, formed in the deck  82  immediately adjacent both sides of the dual-stage brush assembly  90 . The bail  88  is operative to shield the dual-stage brush assembly  90  from larger external objects such as carpet tassels, tufted fabric, rug edges, during cleaning operations, i.e., the bail  88  deflects such objects away from the dual-stage brush assembly  90 , thereby preventing such objects from becoming entangled in the brush mechanisms. 
         [0068]    The dual-stage brush assembly  90  for the described embodiment of  FIG. 3A  comprises a flapper brush  92  and a main brush  94  that are generally illustrated in  FIG. 6 . Structurally, the flapper brush  92  and the main brush  94  are asymmetric with respect to one another, with the main brush  94  having an O.D. greater than the O.D. of the flapper brush  92 . The flapper brush  92  and the main brush  94  are mounted in the deck  82  recess, as described below in further detail, to have minimal spacing between the sweeping peripheries defined by their respective rotating elements. Functionally, the flapper brush  92  and the main brush  94  counter-rotate with respect to one another, with the flapper brush  92  rotating in a first direction that causes macroscopic particulates to be directed into the removable dust cartridge  86  and the main brush  94  rotating in a second direction, which is opposite to the forward movement of the autonomous floor-cleaning robot  10 , that causes macroscopic and microscopic particulates to be directed into the removable dust cartridge  86 . In addition, this rotational motion of the main brush  94  has the secondary effect of directing macroscopic and microscopic particulates towards the pick-up zone of the vacuum assembly  100  such that particulates that are not swept up by the dual-stage brush assembly  90  can be subsequently drawn up (ingested) by the vacuum assembly  100  due to movement of the autonomous floor-cleaning robot  10 . 
         [0069]    The flapper brush  92  comprises a central member  92 CM having first and second ends. The first and second ends are designed and configured to mount the flapper brush  92  in rotatable combination with the deck  82  and a first output port  48 B O1  of the dual output gearbox  48 B, respectively, such that rotation of the flapper brush  92  is provided by the torque transferred from the electric motor  48  (the gearbox  48 B is configured so that the rotational speed of the flapper brush  92  is relative to the speed of the autonomous floor-cleaning robot  10 —the described embodiment of the robot  10  has a top speed of approximately 0.9 ft/sec). In other embodiments, the flapper brush  92  rotates substantially faster than traverse speed either in relation or not in relation to the transverse speed. Axle guards  92 AG having a beveled configuration are integrally formed adjacent the first and second ends of the central member  92 CM for the purpose of forcing hair and other similar matter away from the flapper brush  92  to prevent such matter from becoming entangled with the ends of the central member  92 CM and stalling the dual-stage brush assembly  90 . 
         [0070]    The brushing element of the flapper brush  92  comprises a plurality of segmented cleaning strips  92 CS formed from a compliant plastic material secured to and extending along the central member  92 CM between the internal ends of the axle guards  92 AG (for the illustrated embodiment, a sleeve, configured to fit over and be secured to the central member  92 CM, has integral segmented strips extending outwardly therefrom). It was determined that arranging these segmented cleaning strips  92 CS in a herringbone or chevron pattern provided the optimal cleaning utility (capability and noise level) for the dual-stage brush subassembly  90  of the autonomous floor-cleaning robot  10  according to the present invention. Arranging the segmented cleaning strips  92 CS in the herringbone/chevron pattern caused macroscopic particulate matter captured by the strips  92 CS to be circulated to the center of the flapper brush  92  due to the rotation thereof. It was determined that cleaning strips arranged in a linear/straight pattern produced a irritating flapping noise as the brush was rotated. Cleaning strips arranged in a spiral pattern circulated captured macroscopic particulates towards the ends of brush, which resulted in particulates escaping the sweeping action provided by the rotating brush. 
         [0071]    For the described embodiment, six (6) segmented cleaning strips  92 CS were equidistantly spaced circumferentially about the central member  92 CM in the herringbone/chevron pattern. One skilled in the art will appreciate that more or less segmented cleaning strips  92 CS can be employed in the flapper brush  90  without departing from the scope of the present invention. Each of the cleaning strips  92 S is segmented at prescribed intervals, such segmentation intervals depending upon the configuration (spacing) between the wire(s) forming the bail  88 . The embodiment of the bail  88  described above resulted in each cleaning strip  92 CS of the described embodiment of the flapper brush  92  having five (5) segments. 
         [0072]    The main brush  94  comprises a central member  94 CM (for the described embodiment the central member  94 CM is a round metal member having a spiral configuration) having first and second straight ends (i.e., aligned along the centerline of the spiral). Integrated in combination with the central member  94 CM is a segmented protective member  94 PM. Each segment of the protective member  94 PM includes opposed, spaced-apart, semi-circular end caps  94 EC having integral ribs  94 IR extending therebetween. For the described embodiment, each pair of semi-circular end caps EC has two integral ribs extending therebetween. The protective member  94 PM is assembled by joining complementary semi-circular end caps  94 EC by any conventional means, e.g., screws, such that assembled complementary end caps  94 EC have a circular configuration. 
         [0073]    The protective member  94 PM is integrated in combination with the central member  94 CM so that the central member  94 CM is disposed along the centerline of the protective member  94 PM, and with the first end of the central member  94 CM terminating in one circular end cap  94 EC and the second end of the central member  94 CM extending through the other circular end cap  94 EC. The second end of the central member  94 CM is mounted in rotatable combination with the deck  82  and the circular end cap  94 EC associated with the first end of the central member  94 CM is designed and configured for mounting in rotatable combination with the second output port  48 B O2  of the gearbox  48 B such that the rotation of the main brush  94  is provided by torque transferred from the electric motor  48  via the gearbox  48 B. 
         [0074]    Bristles  94 B are set in combination with the central member  94 CM to extend between the integral ribs  94 IR of the protective member  94 PM and beyond the O.D. established by the circular end caps  94 EC. The integral ribs  94 IR are configured and operative to impede the ingestion of matter such as rug tassels and tufted fabric by the main brush  94 . 
         [0075]    The bristles  94 B of the main brush  94  can be fabricated from any of the materials conventionally used to form bristles for surface cleaning operations. The bristles  94 B of the main brush  94  provide an enhanced sweeping capability by being specially configured to provide a “flicking” action with respect to particulates encountered during cleaning operations conducted by the autonomous floor-cleaning robot  10  according to the present invention. For the described embodiment, each bristle  94 B has a diameter of approximately 0.010 inches, a length of approximately 0.90 inches, and a free end having a rounded configuration. It has been determined that this configuration provides the optimal flicking action. While bristles having diameters exceeding approximately 0.014 inches would have a longer wear life, such bristles are too stiff to provide a suitable flicking action in the context of the dual-stage brush assembly  90  of the present invention. Bristle diameters that are much less than 0.010 inches are subject to premature wear out of the free ends of such bristles, which would cause a degradation in the sweeping capability of the main brush. In a preferred embodiment, the main brush is set slightly lower than the flapper brush to ensure that the flapper does not contact hard surface floors. 
         [0076]    The vacuum assembly  100  is independently powered by means of the electric motor  46 . Operation of the vacuum assembly  100  independently of the self-adjustable brush assembly  90  allows a higher vacuum force to be generated and maintained using a battery-power source than would be possible if the vacuum assembly were operated in dependence with the brush system. In other embodiments, the main brush motor can drive the vacuum. Independent operation is used herein in the context that the inlet for the vacuum assembly  100  is an independent structural unit having dimensions that are not dependent upon the “sweep area” defined by the dual-stage brush assembly  90 . 
         [0077]    The vacuum assembly  100 , which is located immediately aft of the dual-stage brush assembly  90 , i.e., a trailing edge vacuum, is orientated so that the vacuum inlet is immediately adjacent the main brush  94  of the dual-stage brush assembly  90  and forward facing, thereby enhancing the ingesting or vacuuming effectiveness of the vacuum assembly  100 . With reference to  FIGS. 7A ,  7 B, the vacuum assembly  100  comprises a vacuum inlet  102 , a vacuum compartment  104 , a compartment cover  106 , a vacuum chamber  108 , an impeller  110 , and vacuum channel  112 . The vacuum inlet  102  comprises first and second blades  102 A,  102 B formed of a semi-rigid/compliant plastic or elastomeric material, which are configured and arranged to provide a vacuum inlet  102  of constant size (lateral width and gap-see discussion below), thereby ensuring that the vacuum assembly  100  provides a constant air inflow velocity, which for the described embodiment is approximately 4 m/sec. 
         [0078]    The first blade  102 A has a generally rectangular configuration, with a width (lateral) dimension such that the opposed ends of the first blade  102 A extend beyond the lateral dimension of the dual-stage brush assembly  90 . One lateral edge of the first blade  102 A is attached to the lower surface of the deck  82  immediately adjacent to but spaced apart from, the main brush  94  (a lateral ridge formed in the deck  82  provides the separation therebetween, in addition to embodying retaining grooves for the bail  88  as described above) in an orientation that is substantially symmetrical to the fore-aft diameter of the autonomous floor-cleaning robot  10 . This lateral edge also extends into the vacuum compartment  104  where it is in sealed engagement with the forward edge of the compartment  104 . The first blade  102 A is angled forwardly with respect to the bottom surface of the deck  82  and has length such that the free end  102 A FE  of the first blade  102 A just grazes the surface to be cleaned. 
         [0079]    The free end  102 A FE  has a castellated configuration that prevents the vacuum inlet  102  from pushing particulates during cleaning operations. Aligned with the castellated segments  102 CS of the free end  102 A FE , which are spaced along the width of the first blade  102 A, are protrusions  102 P having a predetermined height. For the prescribed embodiment, the height of such protrusions  102 P is approximately 2 mm. The predetermined height of the protrusions  102 P defines the “gap” between the first and second blades  102 A,  102 B. 
         [0080]    The second blade  102 B has a planar, unitary configuration that is complementary to the first blade  102 A in width and length. The second blade  102 B, however, does not have a castellated free end; instead, the free end of the second blade  102 B is a straight edge. The second blade  102 B is joined in sealed combination with the forward edge of the compartment cover  106  and angled with respect thereto so as to be substantially parallel to the first blade  102 A. When the compartment cover  106  is fitted in position to the vacuum compartment  104 , the planar surface of the second blade  102 B abuts against the plurality of protrusions  102 P of the first blade  102 A to form the “gap” between the first and second blades  102 A,  102 B. 
         [0081]    The vacuum compartment  104 , which is in fluid communication with the vacuum inlet  102 , comprises a recess formed in the lower surface of the deck  82 . This recess includes a compartment floor  104 F and a contiguous compartment wall  104 CW that delineates the perimeter of the vacuum compartment  104 . An aperture  104 A is formed through the floor  104 , offset to one side of the floor  104 F. Due to the location of this aperture  104 A, offset from the geometric center of the compartment floor  104 F, it is prudent to form several guide ribs  104 GR that project upwardly from the compartment floor  104 F. These guide ribs  104 GR are operative to distribute air inflowing through the gap between the first and second blades  102 A,  102 B across the compartment floor  104  so that a constant air inflow is created and maintained over the entire gap, i.e., the vacuum inlet  102  has a substantially constant ‘negative’ pressure (with respect to atmospheric pressure). 
         [0082]    The compartment cover  106  has a configuration that is complementary to the shape of the perimeter of the vacuum compartment  104 . The cover  106  is further configured to be press fitted in sealed combination with the contiguous compartment wall  104 CW wherein the vacuum compartment  104  and the vacuum cover  106  in combination define the vacuum chamber  108  of the vacuum assembly  100 . The compartment cover  106  can be removed to clean any debris from the vacuum channel  112 . The compartment cover  106  is preferable fabricated from a clear or smoky plastic material to allow the user to visually determine when clogging occurs. 
         [0083]    The impeller  110  is mounted in combination with the deck  82  in such a manner that the inlet of the impeller  110  is positioned within the aperture  104 A. The impeller  110  is operatively connected to the electric motor  46  so that torque is transferred from the motor  46  to the impeller  110  to cause rotation thereof at a constant speed to withdraw air from the vacuum chamber  108 . The outlet of the impeller  110  is integrated in sealed combination with one end of the vacuum channel  112 . 
         [0084]    The vacuum channel  112  is a hollow structural member that is either formed as a separate structure and mounted to the deck  82  or formed as an integral part of the deck  82 . The other end of the vacuum channel  110  is integrated in sealed combination with the vacuum inlet  86 VI of the removable dust cartridge  86 . The outer surface of the vacuum channel  112  is complementary in configuration to the external shape of curved arcuate member  86 CAM of the removable dust cartridge  86 . 
         [0085]    A variety of modifications and variations of the present invention are possible in light of the above teachings. For example, the preferred embodiment described above included a cleaning head subsystem  80  that was self-adjusting, i.e., the deck  82  was automatically pivotable with respect to the chassis  21  during the adjustment mode in response to a predetermined increase in brush torque of the dual-stage brush assembly  90 . It will be appreciated that another embodiment of the autonomous floor-cleaning robot according to the present invention is as described hereinabove, with the exception that the cleaning head subsystem is non-adjustable, i.e., the deck is non-pivotable with respect to the chassis. This embodiment would not include the deck adjusting subassembly described above, i.e., the deck would be rigidly secured to the chassis. Alternatively, the deck could be fabricated as an integral part of the chassis—in which case the deck would be a virtual configuration, i.e., a construct to simplify the identification of components comprising the cleaning head subsystem and their integration in combination with the robot. 
         [0086]    It is therefore to be understood that, within the scope of the appended claims, the present invention may be practiced other than as specifically described herein.