Abstract:
A drive system for each arm of a mobile robot, each drive system including a drive motor and an adjustable clutch system interconnected between its associated arm and the drive motor and having a high friction locked position for enabling direct drive of the arm by the drive motor and a reduced friction slip position for enabling manual movement of the associated arm without back-driving the drive motor.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to a drive system for mobile robot arms including an adjustable clutch system. 
       BACKGROUND OF THE INVENTION 
       [0002]    Mobile, remotely controlled robots are becoming increasingly popular for use by the military, SWAT units, and police and fire departments. They typically can include an arm with an end effecter, several cameras, several antennas, and a deployable mast. Frequently the end effector is a gripper, e.g. a pair of jaws that can be opened and closed on command to grasp objects such as debris, hazardous material, unexploded ordinance and the like. The larger robots even have the capability to grip an injured, downed, person by some personal paraphernalia such as a shirt collar and drag them out of harm&#39;s way to safety. Often these end effectors, cameras, tools and other devices may be mounted on an arm, typically articulated, with two or more arms, an upper arm and a lower arm, for example. In emergency or combat situations it is often necessary to collapse or extend the arm(s) by hand for loading and transport or deployment, respectively. With smaller less powerful mobile robots their arms may be manually manipulated by back-driving the drive motors. But in larger more powerful mobile robots the force required to manually extend or collapse the arm(s) by back-driving the motors is quite large and so may not be done as quickly as needed and may require more than average strength. 
       SUMMARY OF THE INVENTION 
       [0003]    It is therefore an object of this invention to provide an improved drive system for a mobile robot arm. 
         [0004]    It is a further object of this invention to provide such an improved drive system which enables direct drive of the arm(s) but quick and easy manipulation of the arms in a manual collapse or extension mode. 
         [0005]    It is a further object of this invention to provide such an improved drive system which employs a clutch system which can be adjusted between a high friction positive locked condition and a lower friction slip mode wherein arm collapse and extension can be quickly and easily accomplished. 
         [0006]    It is a further object of this invention to provide such an improved drive system which the slip mode can be set to a lower friction range where the arm(s) can be re-positioned to hold its own weight in any new position without total collapse. 
         [0007]    It is a further object of this invention to provide such an improved drive system where the friction can vary relatively smoothly between positive lock and slip modes. 
         [0008]    The invention results from the realization that a drive system for an arm of a mobile robot which enables positive direct drive and yet allows quick and easy manual extension and collapse of the arm can be achieved with a drive motor and an adjustable clutch system interconnected between its associated arm and the drive motor and having a high friction locked position for enabling direct drive of the arm by the drive motor and a reduced friction slip position for enabling manual movement of the associated arm without back-driving the drive motor. 
         [0009]    The subject invention, however, in other embodiments, need not achieve all these objectives and the claims hereof should not be limited to structures or methods capable of achieving these objectives. 
         [0010]    This invention in at least one embodiment features a drive system for each arm of a mobile robot, each drive system including a drive motor and an adjustable clutch system interconnected between its associated arm and the drive motor and having a high friction locked position for enabling direct drive of the arm by the drive motor and a reduced friction slip position for enabling manual movement of the associated arm without back-driving the drive motor. 
         [0011]    In preferred embodiment there may be lower and upper articulated arms and there may be a lower drive system associated with the lower arm and an upper drive system associated with the upper arm. The clutch system may include a housing drivable by the drive motor, a stack of friction disks moveable with the housing and a plurality of clutch plates, interstitial of the friction discs and movable relative to the housing, an output shaft engaged and rotatable with the clutch plates, a pressure plate, a spider mechanism for urging the pressure plate to compress the friction disks and clutch plates together against the housing, a cover for constraining the friction disks, clutch plate, pressure plate and spider mechanism in the housing and an activator device for moving the spider mechanism between the locked and slip positions. The clutch system may further include a resilient spring member in the housing with the stack. The resilient spring member may be at the end of the stack in the housing. The resilient spring member may include elastomeric material. The spider member may include a plurality of fingers pivotably attached to a hub. The hub may be rotatable to radially extend and withdraw the fingers between locked and slip positions. The pressure plate may include a plurality of radial grooves corresponding to the fingers. The at least one of the grooves and fingers may be tapered to enable rotation of the hub to drive the fingers radially in and out to decrease and increase the force exerted by the pressure plate on the stack of friction discs and clutch plates. There may be a release mechanism for rotating the hub. The lower arm drive system may be fixed to and rotate the lower arm. The lower arm may house a chain drive for driving the upper arm and the chain drive may be driven by the upper arm drive system. There may be a second adjustable clutch mechanism and a second drive motor, each clutch system including an interlocking mechanism for mating with receptive interlocking mechanisms on the arm for tool free engagement of the arm between the clutch mechanisms. In the reduced friction slip position, the adjustable clutch system may support the arm&#39;s own weight. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0012]    Other objects, features and advantages will occur to those skilled in the art from the following description of a preferred embodiment and the accompanying drawings, in which: 
           [0013]      FIG. 1  is a diagrammatic three dimensional view of a mobile robot with articulated arms using two drive systems according to this invention; 
           [0014]      FIG. 2  is a three dimensional top view of a portion of the mobile robot of  FIG. 1  with parts removed showing both drive systems including drive motors and clutches; 
           [0015]      FIG. 3  is an exploded three dimensional view of a clutch system according to this invention; 
           [0016]      FIG. 4  is an enlarged three dimensional view of the spider mechanism of  FIG. 3 ; 
           [0017]      FIG. 5  is a side sectional view of the spider mechanism of  FIG. 4 ; 
           [0018]      FIGS. 6 and 7  are schematic views of the spider mechanism of  FIGS. 4 and 5  radially extended in the friction locked position and radially withdrawn in a slip position; 
           [0019]      FIG. 8  is an enlarged three dimensional view from the clutch side of the clutch and worm gear drive system of  FIG. 2 ; 
           [0020]      FIG. 9  is an enlarged three dimensional view from the worm gear drive side of the clutch and worm gear drive system of  FIG. 2 ; 
           [0021]      FIG. 10  is a three dimensional partially exploded view of a clutch system showing the release mechanism for rotating the hub of the spider mechanism; 
           [0022]      FIG. 11  is a side view of the lower arm of  FIG. 1 ; and 
           [0023]      FIG. 12  is a sectional view along line  12 - 12  of  FIG. 11 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0024]    Aside from the preferred embodiment or embodiments disclosed below, this invention is capable of other embodiments and of being practiced or being carried out in various ways. Thus, it is to be understood that the invention is not limited in its application to the details of construction and the arrangements of components set forth in the following description or illustrated in the drawings. If only one embodiment is described herein, the claims hereof are not to be limited to that embodiment. Moreover, the claims hereof are not to be read restrictively unless there is clear and convincing evidence manifesting a certain exclusion, restriction, or disclaimer. 
         [0025]    There is shown in  FIG. 1  a mobile robot  10  having a pair of articulated arms, upper arm  12 , and lower arm  14 . Upper arm  12  has an end effector  16  which, for example, includes a pair of jaws or grippers  18  and  20 . Upper arm  12  rotates on axis  22  with respect to lower arm  14 . Lower arm  14  rotates on axis  24  with respect to turret  26 . Turret  26  rotates in either direction as indicated by arrows  28  on base  30  which includes, for example, driven treads  32  and  34 . There are two drive systems according to this invention, lower arm drive system  36  and upper drive system  38 . Each drive system includes a release member  40 , clutch system  42  and worm drive  44 . 
         [0026]    Drive systems  36  and  38  further include drive motors  46 ,  FIG. 2 , and may include gear reducers  48  which through shafts  50  couple to worm drives  44 . Drive systems  36  and  38  are identical mirror images of each other. Clutch system  42  and worm drive  44  of drive system  36  is shown in more detail in  FIG. 3 , where clutch system  42  includes a clutch housing  60  rotatable with respect to worm drive housing  62 . A plurality of friction discs  64 , for example eight, are stacked with interstitial clutch plates  66  and are mounted in clutch housing  60  where the teeth  68  of each friction disk  64  aligns with the splines  70  on the inside of clutch housing  60  so that they rotate with clutch housing  60 . Clutch plates  66  do not rotate with housing  60 . Rather clutch plates  66  rotate with shaft  72  which carries output drive plate  74 , fastened in place by bolt  76 , receives thrust bearing washer  76 , thrust bearing cage  78  and another thrust bearing washer  80  and passes through bore  82  in worm drive housing  62  and clutch housing  60 . Shaft  72  has four elongated recesses,  84 , which receive four pins  86 , which in turn engage the four curved corners  88  of the aperture  90  in each clutch plate  66 . Thus, the clutch plates are fixed to rotate with shaft  72  and rotate relative to clutch housing  60 . Pressure plate  92  includes a plurality of tapered slots  94 , each one having at its radially outward tip a ball bearing recess  96  for receiving ball bearings  98 . In this particular embodiment there are twelve slots  94 , twelve ball bearing recesses  96  and twelve ball bearings  98  which accommodate the twelve fingers  100  of spider  102 . Fingers  100  are pivotably attached to hub  104  at pivot pins  106 . The backsides of fingers  100  are tapered and contain recesses to accommodate ball bearings  98 . The front side of fingers  100  are also tapered and also have recesses to accommodate ball plugs  108  controlled by set screws  110 . Set screws  110  are threadably received in holes  112  of spider cover  114 , which is fastened by screws  116  through holes  118  to clutch housing  60 . 
         [0027]    Spider  102  is shown in more detail in  FIG. 4  and  FIG. 5  where the twelve fingers  100  and their pivots  106  are shown more clearly. Hub  104 ,  FIG. 4 , includes a center hole  120  for receiving a fastening bolt and two alignment holes  122  for receiving pins to prevent the release member from rotating relative to hub  120  so that it rotates only with it. The bolt fastener  124  that passes through release member  40  to be received in hole  120  is shown more clearly in  FIG. 5  as are the alignment pins  126  which are received in holes  122 . Also more clearly visible in  FIG. 5  is the tapered shape at the tip  128  of each finger  100  along with the recess  130  on the back of each finger  100  that accommodates ball bearings  98  and the recess  132  on the front of each finger that accommodates ball plugs  108 . Also shown more clearly in  FIG. 5  are the pivots  106  that pivotably mount each finger  100 . 
         [0028]    In operation in the positive lock position,  FIG. 6 , each of the fingers  100  is fully radially extended so that their tapered shape along with the tapered shape of slots  94  in pressure plate  92  enable a maximum force to be applied to the clutch plates and friction discs in the direct drive mode. However, with an easy rotation of release member  40 , for example, a counter clockwise rotation as shown in  FIG. 7 , the fingers  100  rotate around their pivots  106  and are withdrawn radially inwardly in some measure thereby correspondingly decreasing the force on clutch plates  66  and friction disks  64 . In this way the resistance can be reduced so that the arm or arms can be more easily manually collapsed or extended without having to back drive the motor  40  and/or gear drive  48  yet providing support for the arm&#39;s own weight. This also provides mechanical overload protection for the gears and arm members against collisions, jamming or exceeding load limits. The amount of force required in either case is determined in part by the number of fingers  100 . The more fingers there are the less force there will have to be applied by each finger ad the less torque required to lock and release. 
         [0029]    Worm drive  44  is shown more clearly in  FIG. 8 , as including worm gear  140  driven by worm  142  driven in turn by shaft  50 . Also shown more clearly in  FIG. 8  are the ball plugs  108  and set screws  110  which control them.  FIG. 9  shows another view of worm gear  140 , worm  142 , and output drive plate  74 . Release member  40  is shown more clearly in  FIG. 10  along with its mounting screw  124  where it is shown to have a cross bar  150  to facilitate manual gripping and rotating of release member  40 . 
         [0030]    The output plate  74  shown in  FIGS. 8 and 9  engages with a receptor plate  160 ,  FIG. 11 , which is fixed to arm  14  so that as plate  74  rotates, plate  160  rotates with it and with plate  160 . Arm  14  rotates as well, all about axis  24 . Lower arm drive system  36  through its output plate  74  drives receptor plate  160  and this rotates arm  14  as previously indicated. Upper drive system  38  drives its output plate  74  which in turn drives receptor plate  162 ,  FIG. 12 . Receptor plate  162  has an integral shaft  164  which carries sprocket  166  that drives chain  168 . Chain  168  rotates a second sprocket  170  which rotates the upper arm about axis  22 . Sprocket  170  is fixed to a second drive plate  172  which rotates upper arm  12 . See also  FIG. 1 . Chain tension is adjustable via tensioner  173 . The use of two clutches  42 ,  FIG. 2 , one on either side of the arm  14  enables a fastener free engagement of arm  14  using the clutches themselves. Each clutch has an interlocking mechanism  200 ,  FIG. 9 , which for example has four radial recesses  202  and a center hole  204 . These mate with the raised radial fins  206  and stud  208 , respectively, shown in  FIGS. 11 and 12 . 
         [0031]    One preferred robot chassis is disclosed in MODULAR MOBILE ROBOT, by Andrus et al. Ser. No. 12/316,311, filed Dec. 11, 2008 (FM-398J). A turret assembly is disclosed in ROBOT ARM ASSEMBLY by Nathaniel J. M. Seavey, Ser. No. 12/317,131, filed Dec. 18, 2008. 
         [0032]    Although specific features of the invention are shown in some drawings and not in others, this is for convenience only as each feature may be combined with any or all of the other features in accordance with the invention. The words “including”, “comprising”, “having”, and “with” as used herein are to be interpreted broadly and comprehensively and are not limited to any physical interconnection. Moreover, any embodiments disclosed in the subject application are not to be taken as the only possible embodiments. 
         [0033]    In addition, any amendment presented during the prosecution of the patent application for this patent is not a disclaimer of any claim element presented in the application as filed: those skilled in the art cannot reasonably be expected to draft a claim that would literally encompass all possible equivalents, many equivalents will be unforeseeable at the time of the amendment and are beyond a fair interpretation of what is to be surrendered (if anything), the rationale underlying the amendment may bear no more than a tangential relation to many equivalents, and/or there are many other reasons the applicant can not be expected to describe certain insubstantial substitutes for any claim element amended. 
         [0034]    Other embodiments will occur to those skilled in the art and are within the following claims.