Agile mobility chassis design for robotic all-terrain vehicle

An improved connection between articulated bodies for agile vehicles is disclosed. It features independent bodies which are connected to each other with concentric sleeves serving as the pivot to allow the bodies to rotate in a plane parallel to the direction of forward movement. The concentric bushings are preferably made of graphite/epoxy and secured to the chassis body sidewalls. Each of the body segments remains uninterrupted by the bushings which are principally disposed between the facing interior sides of the two bodies. The bearing assembly, which is preferably graphite/epoxy, is self-lubricating as it wears over time. Lateral movement is easily controlled, and relative rotation is also controlled by a collar which serves a dual function to control lateral movement of the bodies as well as relative rotation.

FIELD OF THE INVENTION
 The field of this invention relates to chassis design for highly mobile
 all-terrain vehicles.
 BACKGROUND OF THE INVENTION
 Various robotic vehicles have been developed in the past. To obtain maximum
 agility, such vehicles have incorporated an all-wheel drive dual-body
 design where the bodies are disposed parallel to each other with a
 transverse pivot, generally at their mid-point, disposed transversely to
 the direction of forward or rearward motion. For example, highly mobile
 tractors have been designed using such a transversely mounted mid-body
 pivot for independent rotation in the vertical plane of forward motion
 about such pivot between the two bodies of the vehicle. This design is
 illustrated in U.S. Pat. No. 1,430,251. More recently, in the field of
 lunar exploration rovers, Klarer in "A Highly Agile Ground Assessment
 Robot (HAGAR) for Military Battlefield and Support Missions", SAND94-0408C
 (1994), and in "R.A.T.L.E.R.: Robotic All Terrain Lunar Exploration
 Rovers", SAND92-1821C (1992), has revealed similar designs. The basic
 concept of the prior art designs is illustrated in FIG. 1 of this
 application. FIG. 1 is a section view through a pivot 10 which extends
 through bodies 12 and 14. Each of the bodies 12 and 14 has stationary
 bushings, such as 16, 18, 20, and 22. The bushings 16, 18, 20 and 22 fully
 surround the pivot 10 so that the bodies 12 and 14 can rotate in a plane
 perpendicular to the longitudinal axis of pivot 10.
 There are numerous problems with this type of design. In order to run power
 or communication wiring from one of the bodies 12 to the other 14, or vice
 versa, slits or openings were needed to be made between the bushings in
 each of the bodies 12 and 14 for entrances and exits of such wires. Thus,
 for example, slits made to the pivot 10 between bushings 16 and 18 would
 weaken the pivot 10 in that location. Additionally, if maintenance work
 was necessary or additional wires had to be added and connectors were
 disposed on wiring inside the pivot 10 in area 24, such connectors would
 get hung up on the slits used for access for such wires to get through the
 pivot 10 in the first place. Another problem with the use of a pivot 10
 which goes cleanly through both bodies 12 and 14 is that as shown in FIG.
 1, it separates the bodies 12 and 14 into two halves where communication
 with wiring becomes problematic. The prior art design shown in FIG. 1 also
 had problems in designing an effective travel stop. Although one attempted
 design was to put a projection on the pivot 10 which would, within bodies
 12 or 14, strike a fixed object, the problem was that the pivot 10 was of
 such a diameter so as to present a significant lever arm on the projection
 mounted to its outer surface. Thus, what resulted in the past was shear
 failures of the travel stop. The function of a travel stop is significant
 in this particular prior art design in view of the fact that a variety of
 wires for both power and signals cross through the area 24 from body 12 to
 14 and vice versa. This means that if undue relative rotation between
 bodies 12 and 14 were to occur, some of those wires could be cut, causing
 a battery or other power system failure or even a fire.
 Yet another problem with the prior designs which used carbon composite
 bushings, with an aluminum pivot 10 was that galvanic action created
 maintenance problems at the interface of those two components.
 Accordingly, the apparatus of the present invention seeks to improve the
 prior art design revealed in FIG. 1 and present a comparable degree of
 agility to the vehicle, while at the same time providing the enhanced
 benefits of a more compact design which alleviates the problems previously
 described in the prior art design of FIG. 1. Just how such problems in the
 prior art design are overcome is best understood by a review of the
 preferred embodiment of the invention which appears below.
 SUMMARY OF THE INVENTION
 An improved connection between articulated bodies for agile vehicles is
 disclosed. It features independent bodies which are connected to each
 other with concentric sleeves serving as the pivot to allow the bodies to
 rotate in a plane parallel to the direction of forward movement. The
 concentric bushings are preferably made of graphite/epoxy and secured to
 the chassis body sidewalls. Each of the body segments remains
 uninterrupted by the bushings which are principally disposed between the
 facing interior sides of the two bodies. The bearing assembly, which is
 preferably graphite/epoxy, is self-lubricating as it wears over time.
 Lateral movement is easily controlled, and relative rotation is also
 controlled by a collar which serves a dual function to control lateral
 movement of the bodies as well as relative rotation.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
 Referring to FIG. 2, the vehicle V comprises parallel bodies 26 and 28.
 These are generally rectangular in cross-section, as shown in FIG. 4, and
 elongated, as shown in FIG. 2. They are generally enclosed and contain
 many components such as the drive motors 30 which can give a four-wheel
 drive capability to the vehicle V. Various power supplies, signal and
 power cables extend in the interior spaces 32 and 34 of the bodies 26 and
 28, respectively. A passage 36 extends through the pivot assembly 38.
 Pivot assembly 38 has an axis 40. The bodies 26 and 28 rotate in a plane
 perpendicular to axis 40. There is a limit to the relative rotation by way
 of a travel stop, which is illustrated in FIG. 5, which will be described
 below.
 Before describing the travel stop, the details of the pivot assembly 38
 will be described by referring to FIGS. 3 and 4. FIG. 3 shows the basic
 components which include an inner sleeve 42, which has a flange 44 at end
 46. An outer sleeve 48 has a flange 50 at end 52. A stop collar 54 has a
 flange 56. The essential components and assembly now having been shown in
 FIG. 3, the mounting to the bodies 26 and 28 can be best seen in either
 FIGS. 2 or 4. The flange 44 is secured to the interior wall 58, with inner
 sleeve 42 extending through an opening 60 in body 26. The outer sleeve 48
 is slipped over the inner sleeve 42 and its flange 50 is secured to wall
 62 of body 28. Opposite exterior wall 62 is interior wall 64. The stop
 collar 54 is secured to the inner sleeve 42 inside of inner wall 64 such
 that flange 56 acts as a lateral travel stop. In essence, the gap 66
 between flanges 50 and 56 is fixed; thus, flange 56 prevents the bodies 26
 and 28 from moving away from each other. Lower end 68 eventually can
 contact surface 70 on flange 44 to limit the movement of bodies 26 and 28
 toward each other.
 The wall which comprises exterior wall 62 and interior wall 64, for
 example, can be a composite of carbon surfaces with an intermediate
 honeycomb. This wall assembly can also be used as the opposite wall in
 body 26. Sleeve 48 is then advanced through opening 60 in the composite
 wall and flange 44 is secured to interior carbon wall 58.
 Referring now to FIG. 5, the travel stop feature is illustrated. Flange 56,
 which is inside body 28, has an oversized diameter with a flat spot or
 spots 72. Since the stop collar 54 is secured to the inner sleeve 42, upon
 a predetermined amount of rotation the flat spot 72 will strike the bottom
 74 of body 28, thus limiting the ability of body 26 to continue rotating
 with respect to body 28. Going the other way, a travel stop for body 28
 with respect to body 26 can be provided in a variety of ways. The outer
 sleeve 48 can have a circumferential slot through which extends a pin
 secured to the inner sleeve 42, as illustrated in FIG. 6. Accordingly,
 with the body 26 held fixed, the relative rotation of body 28 can be
 limited as the ends of the slot approach the pin. Those skilled in the art
 will appreciate that other mechanisms can be used to create the relative
 travel stops without departing from the spirit of the invention.
 The preferred materials for the inner sleeve 42 and the outer sleeve 48 are
 graphite/epoxy to make them self-lubricating as they wear over time.
 Those skilled in the art will readily appreciate the advantages of the
 design shown in FIGS. 2-5 as compared to FIG. 1. The two bodies 26 and 28
 do not have valuable space internally taken up by the pivot 10 as shown in
 the prior art. Instead, spaces 34 and 32 are uninterrupted over the long
 dimension of the vehicle. This increases the ability to insert payload or
 components and dramatically increases the space for wiring and cooling
 gases to pass between the chassis bodies. The design is compact and low
 maintenance and incorporates in it a feature of controlling the spacing
 between the bodies 26 and 28, as well as relative rotation. The fact that
 the pivot assembly 38 does not extend transversely through the bodies 26
 and 28 also dramatically reduces its weight, hence the increase in payload
 capability. While graphite/epoxy materials are preferred, other materials
 can be used for the pivot assembly 38 without departing from the spirit of
 the invention. The stop collar 54 can be removably mounted so that the
 bodies 26 and 28 can be separated easily if that is desired.
 The foregoing disclosure and description of the invention are illustrative
 and explanatory thereof, and various changes in the size, shape and
 materials, as well as in the details of the illustrated construction, may
 be made without departing from the spirit of the invention.