Abstract:
An apparatus for traversing obstacles having an elongated, round, flexible body that includes a plurality of articulating propulsion members. This plurality of propulsion members cooperate in a worm-like or alternating tripod gait to provide forward propulsion wherever a propulsion member is in contact with any feature of the environment, regardless of how many or which ones of the plurality of propulsion members make contact with such environmental feature.

Description:
STATEMENT OF GOVERNMENTAL SUPPORT 
     This invention was made with Government support under Grant No. DE-FG02-86NE37969 awarded by the Defense Advanced Research Projects Agency. The Government has certain rights in this invention. 
    
    
     FIELD OF THE INVENTION 
     The present invention generally relates to an apparatus for traversing obstacles and, more particularly, to an apparatus for traversing obstacles having an elongated, flexible body and a coordinated millipede-type propulsion. 
     BACKGROUND OF THE INVENTION 
     Robotic vehicles are often used to navigate or traverse varying terrain. As is well known, wheeled robotic vehicles, both large and small, are particularly well adapted for travel over relatively smooth terrain, such as roads and smooth floors. However, it is often necessary for robots to traverse terrain that is not smooth, such as stairs or curbs. Moreover, it is often necessary for robots to traverse terrain that may pose a danger to humans, such as those situations presenting an environmental risk, military risk, or the like. Often robotic devices are useless in these dangerous situations because of their inability to successfully and reliably traverse any severely broken and/or fractured ground that they may encounter. Attempts have been made to overcome the numerous disadvantages of wheeled robotic vehicles in these situations by simply increasing the diameter of the wheels or adding tank crawler tracks to increase the ability of the robotic device to traverse large objects or spans. However, these solutions include additional disadvantages, such as increasing the overall size of the vehicle, which may inhibit the robot&#39;s ability to pass through small openings. 
     Furthermore, many robots suffer from being rendered immobile as a result of a rollover or other situation that prevents contact of their propulsion member(s) on the ground surface. That is, should a wheeled robot encounter a grade sufficient to roll it on its side, the wheels are no longer capable of propelling the robot. In terrains that pose a risk to humans, such rollovers may render the robot unrecoverable. 
     Accordingly, there exists a need in the relevant art to provide an apparatus capable of traversing severely broken and/or fractured ground. Further, there exists a need in the relevant art to provide an apparatus capable of traversing severely broken and/or fractured ground without unduly limiting the ability to pass through small openings. Still further, there exists a need in the relevant art to provide an apparatus capable of engaging its environment at any point about its periphery to minimize the possibility of the apparatus becoming immobile. Furthermore, there exists a need in the relevant art to provide an apparatus for traversing obstacles that overcomes the disadvantages of the prior art. 
     SUMMARY OF THE INVENTION 
     According to the principles of the present invention, an apparatus for traversing obstacles having an advantageous design is provided. The apparatus having an elongated, round, flexible body that includes a plurality of articulating propulsion members. This plurality of propulsion members are disposed generally continuously about each articulating propulsion member and cooperate in a worm-like or alternating tripod gait to provide forward propulsion whenever a propulsion member is in contact with any feature of the environment, regardless of how many or which ones of the plurality of propulsion members make contact with such environmental feature. 
     The apparatus according to the principles of the present invention is capable of traversing terrain that includes obstacles larger than its body. Furthermore, the apparatus according to the principles of the present invention is capable of burrowing into soft soil. 
     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
     FIG. 1 is a perspective view illustrating an apparatus for traversing obstacles according to the principles of the present invention; 
     FIG. 2 is a side view illustrating the apparatus; 
     FIG. 3 is a front view illustrating the apparatus; 
     FIG. 4 is an enlarged perspective view illustrating the actuation of a joint between two segments of the apparatus; 
     FIG. 5 is a perspective view illustrating an articulating leg mechanism according to the principles of the present invention; 
     FIG. 6 is a perspective view of a universal coupling interconnecting drive shafts of adjacent segments of the apparatus; 
     FIG. 7 is a perspective view of a transmission for transmitting power from the drive shaft to the drive leg mechanism; 
     FIG. 8 is a perspective view of the transmission of FIG. 7 having portions removed for clarity; 
     FIG. 9 is a schematic view illustrating the motion trajectory of the articulating leg mechanism according to the principles of the present invention; and 
     FIG. 10 is a perspective view of an articulating joint according to the principles of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The following description of the preferred embodiment is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. 
     Referring to the drawings, an apparatus  10  for traversing obstacles is illustrated having a plurality of identical segments  12 . Each of the plurality of segments  12  includes a plurality of articulating leg mechanisms  14  disposed about the periphery of each segment  12 . According to the present embodiment, each of the plurality of segments  12  includes four articulating leg mechanisms  14  evenly spaced at 90° intervals about the periphery of each segment  12  to provide a generally continuous series of propulsion members. However, it is anticipated that any number of articulating leg mechanisms may be used so long as they generally extend around the outer diameter or periphery of each segment  12 . By positioning articulating leg mechanisms  14  continuously about the periphery of segment  12 , apparatus  10  is more likely to engage a feature within the environment to provide reliable locomotion. This ability to engage an environmental feature, whether it be the ground surface, wall protrusion, ceiling cavity, or the like, irrespective of its physical orientation provides apparatus  10  with a reliable means of continued propulsion. Adjacent segments  12  are joined together via an articulating joint  16  and a drive shaft  18 . 
     Apparatus  10  may include any number of identical segments  12  connected to each other in a serial fashion. The number of segments  12  required depends on the terrain that must be covered. Moreover, as a result of their identical construction, segments  12  may be easily added, removed, or exchanged with other robots. For illustration and discussion purposes, the figures contained herein comprise nine individual segments  12 . 
     Referring in particular to FIGS. 4 and 5, each of the plurality of articulating leg mechanisms  14  includes a leg  20 , a foot  22 , a driven gear  24 , and a drive gear  26 . As can be seen in FIG. 4, articulating leg mechanism  14  includes only one degree of freedom, providing a simplified propulsion system. That is, by having only one degree of freedom per leg, instead of the multiple degrees of freedom like many other legged vehicles, the number of required actuators is reduced, thereby reducing the weight, complexity, and cost of apparatus  10 . 
     As best seen in FIG. 3, foot  22  is generally arcuate in shape so as to be generally complimentary to an overall outer shape of apparatus  10 . However, the radius of curvature of each foot  22  is preferably less than the radius of curvature of a circle C (FIG. 3) swept around apparatus  10  and intersects the outermost point of each foot  22 . This arrangement minimizes the potential for sideways rolling of apparatus  10 . However, as described above, should apparatus  10  nonetheless rollover, at least some of articulating leg mechanisms  14  disposed about the periphery of each segment  12  will engage a feature of the environment for continued locomotion. 
     The trajectory of foot  22  is determined by the mechanism illustrated in FIG.  5 . Specifically, driven gear  24  enmeshingly engages drive gear  26 . Driven gear  24  includes a pivot pin  28  that is operably received within an aperture  30  of leg  20 . Similarly, drive gear  26  includes a cam pin  32  that is operably received within a cam slot  34  of leg  20 . As driven gear  24  rotates in a first direction and thereby drives drive gear  26  in an opposite direction, pivot pin  28  acts within aperture  30  to drive leg  20  in an extending and retracting motion. Simultaneously, cam pin  32  cammingly engages cam slot  34  and drives leg  20  in a sweeping, shoveling, or rotating motion, as illustrated in FIG.  9 . Thus, the trajectory of foot  22  generally includes a lowered portion that is in contact with the ground surface for applying a propelling force to move apparatus  10  and a raised portion that is not in contact with the ground surface to allow for forward placement of foot  22  without interfering with the propelling force applied by other feet  22 . 
     Apparatus  10  further includes a “head” segment  36 . Head segment  36  is identical to segment  12 ; however, head segment  36  further includes a plurality of sensors  38  (only one shown) and an onboard computer/controller  40 . The plurality of sensors  38  may be used to gather environmental data, surveillance data, or any number of other uses. Onboard computer  40  is used to control the movement of apparatus  10  and to provide a means of controlling and/or communicating with the various systems of apparatus  10 . To this end, onboard computer  40  preferably includes a controller area network (CAN) interface. In operation, onboard computer  40  receives environmental data, surveillance data, or any number of other data from other onboard sensors located throughout apparatus  10 . The data is then carried to onboard computer  40  via a serial CAN bus. The CAN may then be used to provide a control signal to the plurality of articulating leg mechanisms  14  of apparatus  10 . This arrangement reduces the number of electrical wires needed throughout apparatus  10 . The mechanical operation of head segment  36  is identical to that of segments  12 . Therefore, in the interest of brevity, only a single segment  12  will be discussed in detail, except as otherwise noted. 
     Apparatus  10  further includes drive shaft  18 . Drive shaft  18  provides input power to each of the plurality of articulating leg mechanisms  14  via a transmission  42  disposed in each segment  12 . Drive shaft  18  is a single drive shaft that kinematically links each segment  12  and, more particularly, each articulating leg mechanism  14 . To this end, drive shaft  18  includes a universal joint  44  (FIG. 6) that allows power transfer independent of the relative orientation of segments  12 . This arrangement enables all articulating leg mechanisms  14  to be driven by a single actuator, generally indicated at  45 , which supplies torque to drive shaft  18 . It should be appreciated that since all articulating leg mechanisms  14  are kinematically linked by single drive shaft  18 , the phase differences between each articulating leg mechanism  14  are fixed. That is, the phase relationship of articulating leg mechanisms  14 , which defines the gait of apparatus  10 , will remain whatever it was when the robot was assembled. 
     The use of single actuator  45  for supplying power to all articulating leg mechanisms  14  has numerous advantages. Firstly, actuator  45  can be placed on a specially designed segment (not shown) at the tail end of apparatus  10  in such a way as to minimize the load on articulating leg mechanisms  14 , thus reducing the required size of the actuator. Secondly, multiple actuators weigh more than a single actuator that produce the same amount of power, thus the overall weight of apparatus  10  is reduced by using a single actuator for all articulating leg mechanisms  14 . Thirdly, the use of high energy density power sources, such as a small gasoline engine, might be feasible. The energy density of a small gasoline engine with tank is about one order of magnitude greater than that of a comparable electric motor with lithium-ion battery. 
     Referring now to FIGS. 7 and 8, transmission  42  interconnects drive shaft  18  with an input shaft  62  of each articulating leg mechanism  14  of each segment  12 . Transmission  42  includes an inner spur gear  50  that is fixedly coupled to drive shaft  18  for rotation therewith. Inner spur gear  50  meshes with two idler spur gears  52  (only one shown), which each mesh with an outer spur gear  54  (only one shown). Outer spur gear  54  is fixedly coupled to a shaft  56 . Also fixedly coupled to shaft  56  is a worm gear  58 . Worm gear  58  meshes with two worm gears  60 . Each of these four worm gears  60  is fixedly coupled to input shaft  62  of articulating leg mechanism  14 . Input shaft  62  is fixed for rotation with drive gear  26 , which thus drives driven gear  24  and rotates leg  20  and foot  22  through a five-bar geared mechanism as described above to produce the trajectory illustrated in FIG.  9 . Alternatively, inner spur gear  50  and outer spur gear  54  may each be replaced with a pulley and belt system for power transfer. 
     Adjacent segments  12  of apparatus  10  are connected using articulating joints  16  (FIGS.  4  and  10 ). Specifically, for discussion purposes, adjacent segments  12  will be referred to as segment  12   a  and segment  12   b  in FIG. 10 only. Although, it should be appreciated that segments  12   a  and  12   b  are identical in construction. Each articulating joint  16  comprises two revolute joints, generally indicated as axis A and axis B, whose axes intersect at an intersection point of articulating joint  16 . These two revolute joints are separated by 90° to provide the two degrees of freedom. As best seen in FIG. 10, these two degrees of freedom are each independently controlled with an actuator or pneumatic piston  64   a  and  64   b  (generally indicated as  64  elsewhere). Each segment  12   a  and  12   b  include a pair of arm supports  66  extending from end surfaces  68  thereof (FIGS.  7  and  10 ). The pair of arm supports  66  are pivotally journalled to a floater bracket  70  via a pair of pivot pins  72 . Articulation of joint  16  about axis A is caused when actuator  64   a,  which is mounted on segment  12   a,  pushes or pulls a bracket  74   a  by means of a rotating crank  76   a.  Accordingly, this actuation rotates segment  12   a  relative to floater bracket  70  about axis A. 
     Similarly, articulation of joint  16  about axis B is caused when actuator  64   b,  which is mounted on segment  12   b,  pushes or pulls a bracket  74   b  (located on a backside in FIG. 10) by means of a rotating crank  76   b  (located on a backside in FIG.  10 ). Accordingly, this actuation rotates segment  12   b  relative to floater bracket  70  about axis B. Actuators  64   a  and  64   b  enable apparatus  10  to lift its front end on top of obstacles. This allows apparatus  10  to adjust to the contour of the terrain and overcome obstacles that are orders of magnitude larger than its step height. 
     A skin (not shown) may be applied around apparatus  10  to protect all internal parts from moisture or sand. However, in some applications, a skin may not be necessary. 
     As best seen in FIGS. 2 and 3, apparatus  10  is illustrated as walking on a flat surface, for a simplified discussion model. However, it should be understood that apparatus  10  is capable of traversing rough terrain. As seen in FIG. 3, the front view of apparatus  10  shows that feet  22  of segment  12  touch the ground at two contact points A and B. This is due to the fact that the radius of curvature of feet  22  is smaller than the overall radius of curvature of apparatus  10 , thereby producing generally flat surfaces extending between the ends of adjacent feet  22  on a single segment  12  (see FIG.  3 ). This arrangement reduces the tendency of the otherwise cylindrical robot (when all segments are aligned) to roll. However, it should be understood that these contact points may be at any point about the periphery of apparatus  10 . For instance, should apparatus  10  span a fractured ground or fractured pipe, feet  22  of articulating leg mechanism  14  may engage a feature along the ceiling thereof to provide locomotion. Moreover, should apparatus  10  traverse a continuous pipe that is only slightly larger in diameter than apparatus  10 , then all feet  22  disposed about each segment  12  would engage the walls thereof. Thus, each segment  12  may have multiple simultaneous contact points. 
     The particular gaits of apparatus  10  will now be described with general reference to FIG. 2, which illustrates a worm-like gait. For purposes of discussion, head segment  36  will be referred to as segment one while the last segment will be referred to as segment nine and the remaining segments numbered consecutively therebetween. Furthermore, the two feet  22  that are contacting the ground at each segment will be referred to as the right and left feet as apparatus  10  faces forward. 
     FIG. 2 illustrates a worm-like gait in that the plurality of articulating leg mechanisms  14  disposed on each segment  12  are synchronized to provide a simultaneous driving motion. That is, accordingly to the worm-like gate, all leg mechanisms  14  on a given segment  12  are in phase with the other leg mechanisms  14  on that given segment  12 . However, adjacent segments  12  are out of phase with each other. For example, to achieve a worm-like gait, the left and right feet of segment one would be in a pre-driving position, the left and right feet of segment two would be in a driving position in contact with the ground surface, and the left and right feet of segment three would be in a post-driving position (see FIG.  2 ). Such a worm-like gait is particularly useful for burrowing and/or tunneling into soil. 
     Alternatively, an alternating tripod gait may be used and is particularly useful for traversing an above-ground surface. According to this alternating tripod gait, the right foot of segments one and seven, and the left foot of segment four all touch the ground simultaneously in generally a triangular pattern. The left foot of segments two and eight, and the right foot of segment five will be the next to touch the ground, and so forth. Accordingly, it should be appreciated that unlike the aforementioned worm-like gait, each articulating leg mechanism  14  is 180° out of phase with the adjacent leg mechanism of the same segment. This arrangement provides a very stable tripod support structure. 
     It should be appreciated that the particular gait employed depends, in part, on the terrain encountered. It is anticipated that onboard computer  40  and articulating leg mechanism  14  of apparatus  10  could be adapted to change the gait of apparatus  10  in accordance with the environmental conditions experienced. 
     Accordingly, the apparatus of the present invention may find utility in a wide variety of applications. By way of non-limiting example, apparatus  10  may be used for fully autonomous search for survivors of earthquakes underneath the rubble of collapsed buildings; military applications in very rugged terrain; mining and autonomous search for other natural resources in terrain that is not accessible to humans (i.e., jungles, mountains, etc.); autonomous burrowing in soft soil; monitoring potential underground radiation leakage of buried radioactive waste; nuclear disaster cleanup (e.g., Chernobyl) and sample retrieval; or research platform for studying many-legged locomotion. 
     The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.