Abstract:
Methods and apparatus for supporting a payload within a vehicle, especially a land vehicle. In some embodiments, the apparatus includes a cradle that permits the payload to translate fore and aft during sudden decelerations of the vehicle, such as when an off road vehicle runs into an obstacle. Preferably, the payload motion is damped by dampeners that couple the payload to the vehicle.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims priority to U.S. Provisional Patent Application Ser. No. 60/710,604, filed Aug. 23, 2005, which is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention pertains to methods and apparatus for isolating a payload from a low frequency, high amplitude movement, and in particular for isolating sensitive electronics or a driver from the effects of vehicle collisions.  
       BACKGROUND OF THE INVENTION  
       [0003]     There are increasing applications for robotically controlled vehicles, especially robotically controlled ground vehicles that are adapted and configured to traverse unprepared terrain. Some robotic, all-terrain vehicles are used in military applications. These vehicles may be required to carry supplies, sensors, weapons, or injured soldiers. There are also analogous non-military uses for such vehicles, including transportation of supplies during wilderness trips, remote surveillance by law enforcement officials, and transportation of injured people.  
         [0004]     Unfortunately, the algorithms for controlling the path of a vehicle over unprepared terrain sometimes produce unexpected results. Even though the vehicle controller may have information from a variety of spatial sensors (including visual, infrared, acoustic, and radar signals, and GPS information in combination with stored terrain maps). The sensors may not detect some obstacles, the computer may not properly interpret the sensor information, or the path of the vehicle may change suddenly in time (such as from falling boulders or shock waves from nearby explosions). In such cases, the vehicle may be impacted in such a way that low frequency, high amplitude G levels are encountered. One example would be a vehicle running into a wall.  
         [0005]     These low frequency, high G impacts can have a severe effect on the payload of the vehicle. As one example, the vehicle can include a controller, such as a computer. The computer may fail mechanically because it is inadequately designed for the low frequency, high amplitude environment. Often, such controllers are vibration tested, typically at frequencies of 20 hertz and above; or shock tested, such as with half sine waveforms; or exposed to static G levels, such as in a centrifuge but these various testing methods and environment may be inadequate to simulate a vehicle hitting a wall. If the controller&#39;s qualification testing was inadequate for this environment, then failures will likely result.  
         [0006]     What is needed are methods and apparatus for managing the environment of a critical payload being exposed to a low frequency, high G environment. The present invention does this in novel and unobvious ways.  
       SUMMARY OF THE INVENTION  
       [0007]     Some aspects of various embodiments of the inventions described or claimed herein relate to the cradling of a payload within a vehicle to reduce the exposure of the payload to sudden acceleration of the vehicle.  
         [0008]     Yet other aspects of various embodiments of the inventions described or claimed herein relate to the support of a payload such that the payload is provided with sway-space within the vehicle in which the payload can be more slowly accelerated than the vehicle itself.  
         [0009]     These and other aspects of the various embodiments of the invention will be apparent from the claims, drawings, and description to follow.  
     
    
     DESCRIPTION OF THE DRAWINGS  
       [0010]      FIG. 1  is a front, top, left side perspective view of a vehicle according to one embodiment of the present invention.  
         [0011]      FIG. 2A  is a perspective view of the vehicle of  FIG. 1  with the body removed.  
         [0012]      FIG. 2B  is a side view of the apparatus of  FIG. 1  with the body and other parts removed.  
         [0013]      FIG. 3  is a top plan view of a cradling assembly according to one embodiment of the present invention.  
         [0014]      FIG. 4A  is a cross sectional view of the apparatus of  FIG. 3  as taken along line  4 A- 4 A of  FIG. 3 .  
         [0015]      FIG. 4B  is a cross sectional view of the apparatus of  FIG. 3  as taken along line  4 A- 4 A of  FIG. 3 .  
         [0016]      FIG. 5  is a bottom view of the apparatus of  FIG. 3 .  
         [0017]      FIG. 6  is a top plan view of a portion of the apparatus of  FIG. 3 .  
         [0018]      FIG. 7  is a cross sectional view of the apparatus of  FIG. 6  as taken along lines  7 - 7  of  FIG. 6 .  
         [0019]      FIG. 8  is a bottom plan view of the apparatus of  FIG. 6 .  
         [0020]      FIG. 9  is top, front, left side perspective view of a cradling assembly according to another embodiment of the present invention.  
         [0021]      FIG. 10  is front, left side view of an apparatus according to another embodiment of the present invention.  
         [0022]      FIG. 11  is a side elevational view of the apparatus of  FIG. 10 .  
         [0023]      FIG. 12  is a schematic representation of the dynamic interconnection of various components to each other and also the interconnection of various sensors and actuators to an electronic controller.  
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0024]     For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated device, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.  
         [0025]     As used herein, the directions X, Y, and Z refer to fore and aft (longitudinal), right and left (lateral), and up and down (vertical) direction, respectively, for a conventional right-hand, orthogonal, Cartesian coordinate system, as best seen in  FIG. 1 . The terms roll, pitch, and yaw refer to rotations about the X, Y, and Z axes, respectively. Additionally, the use of an N-prefix in front of an element number (NXX) refers to an element that is the same as the non-prefixed element number (XX), except for the changes shown and described.  
         [0026]     In one embodiment, the present invention pertains to a method and apparatus for modifying the acceleration load into the payload of a vehicle which is being exposed to a low frequency shock input. As one example, the apparatus includes a cradle that is pivotally supported by front and rear pivot joints. In one embodiment, each pivot joint is a ball and socket joint which permits rotational movement of the ball relative to the socket in three directions; although in some embodiments the particular design of the cradle and attachment structure may limit movement in one or two directions. In yet other embodiments, each pivot joint permits two degrees of relative rotational movement (such as a universal joint), such as for roll and pitch. In yet other embodiments, each pivot joint permits relative rotational movement in only a single direction, such as either roll or pitch.  
         [0027]     In yet other embodiments, the payload is suspended by a cradle which is adapted and configured to place the center of gravity of the payload lower than the roll or pitch axes of the front and rear cradle support joints, such that any movement of the payload center of gravity (C.G.) from the centerline of the pivot joints produces a restoring moment which tends to realign the payload C.G. relative to the rotational axes.  
         [0028]     In yet other embodiments, there is a cradle within a vehicle which is pivotally supported from the vehicle chassis at the front and the rear by central pivot joints. Each of the central pivot joints is captured between top and bottom biasing units, such as top and bottom springs. In one embodiment, each spring is preloaded so that the cradle attachment is approximately centered about the corresponding pivot joint. Preferably, the preload of the bottom spring is greater than the corresponding supported portion of the cradle and payload static weight.  
         [0029]     In yet another embodiment of the present invention, a cradle is suspended by a plurality of pivot joints from a vehicle chassis. The cradle is further pivotally coupled to the chassis by a plurality of dampening units which utilize a magnetorheological (MR) fluid. Each dampening assembly is operably connected to an electronic controller which can apply a voltage to the fluid in order to modify the dampening characteristics of the damper by modifying the properties of the MR fluid. The electronic controller is preferably a computer which operates a software algorithm to isolate the payload from low frequency, high amplitude movements. In one embodiment, the controller senses rapid deceleration of the vehicle (such as when hitting an object) and applies a controlled voltage to one or more of the MR dampers in order to lessen the G-amplitude into the payload, sometimes with a corresponding lengthening of the time duration of the event.  
         [0030]     In yet another embodiment of the present invention, a vehicle chassis is pivotally connected to a first cradle, and a second cradle is pivotally connected to the first cradle. The second cradle is pivotally attached to the first cradle and is pivotal about an axis generally parallel to the vehicle pitch axis. In yet other embodiments, a dampening unit is pivotally coupled at one end to the second cradle and pivotally coupled at the other end to the first cradle.  
         [0031]     Yet another embodiment of the present invention includes a cradle placed within a vehicle and supported at each end by a central pivot joint. One attachment of the cradle to the central pivot joint (either the front or the rear) is by a substantially close-fitting bushing. The other pivotal connection of the cradle (at the other of the front or rear) is by means of a longitudinally oriented slot which permits limited relative movement of the cradle relative to the corresponding central pivot joint in a direction generally parallel to the longitudinal axis of the vehicle. This arrangement of a pivot within a longitudinally-oriented slot permits the front and rear central pivot joints, which are attached to the frame, to move longitudinally relative to each other without putting the cradle in a load path attempting to maintain their relative positions.  
         [0032]      FIGS. 1 and 2 A are perspective views of a vehicle  20  according to one embodiment of the present invention. Vehicle  20  includes a body  22  mounted to a chassis  30 . A plurality of tires  24  and corresponding wheels  25  provide cushioned support for body  22  and chassis  30  by a plurality of suspension arms  26  and spring/shock dampers  28 . In one specific embodiment, each tire  24  is supported on a wheel that is pivotally attached to upper and lower suspension control arms  26  to chassis  30 . Further, each wheel is biased from the chassis by a pair of spring/damper units  28 . Further, the suspension control arms  26 , spring/damper units  28 , and the chassis  30  can be adapted and configured to permit large vertical movements of a suspended tire as the vehicle crosses natural terrain. In yet other embodiments, the vehicle  20  is robotically controlled by an operator that is not riding in the vehicle. The vehicle described and depicted in  FIGS. 1 and 2 A is an adaptation of an all-terrain vehicle. In such vehicles the tires  24  are sometimes relatively soft due to low tire inflation pressures, or as run-flat tires.  
         [0033]     In one embodiment, vehicle  20  is a robotic all-terrain vehicle with the following measurements and capacities:  
                                       DISPLACEMENT   641 cc       ENGINE TYPE   SOHC 4-stroke 4-valve       COOLING SYSTEM   Liquid w/fan       TRANSMISSION   Automatic CVT with engine           braking system       DRIVE SYSTEM   2/4 WD + Diff Lock       OVERAL WIDTH   47.5″       OVERALL HEIGHT   49.3″       OVERAL LENGTH   84.8″       WHEEL BASE   50.0″       SUSPENSION TRAVEL FRONT   10.0″       SUSPENSION TRAVEL REAR   10.0″       GROUND CLEARANCE   12.0″       SUSPENSION TYPE - FRONT   Double A-Arm       SUSPENSION TYPE - REAR   Fully Independent Suspension       BRAKE FRONT   Hydraulic Disc       BRAKE REAR   Hydraulic Disc       TIRE FRONT   25 × 8-12       TIRE REAR   25 × 11-12       MAX FUEL CAPACITY   6.5 Gallons/24.6 Liters       RACK CAPACITY - FRONT   100 lbs.       RACK CAPACITY - REAR   200 lbs.       TOWING CAPACITY   1050 lbs.       ALTERNATOR CAPACITY   25 Amps       SPEEDOMETER   Digital       ODOMETER   Digital       DRY WEIGHT (LBS)   699                  
 
         [0034]     Some features of vehicle  20  include: compact, all-aluminum body frame; carbon fiber and Kevlar body; sleek, low-profile body with low CG; heavy-duty independent front and rear suspension; high-ground clearance suspension geometry; run-flat all-terrain tires; lightweight; comparable size to a full-size ATV or small automobile; and turn-key, plug and go capability. Although specific measurements, capacities, and dimensions have been described, the present invention is not so limited, and this data is provided as an example only.  
         [0035]     Although a robotic, all-terrain vehicle has been shown and described; the present invention also contemplates those embodiments in which the vehicle  20  is any kind of vehicle in which it is desired to manage any low frequency movement (including both low amplitude and high amplitude) into a payload of the vehicle. As examples, the present invention contemplates usage on automobiles, trucks, buses, ships and boats (including small, high speed military boats), fixed wing aircraft, and rotary wing aircraft. Further, although what has been shown and described is a robotic vehicle, the present invention also contemplates those embodiments in which the payload being supported is the vehicle operator, a weapons officer, or an injured person. Some embodiments of the present invention support a person in a “cocoon”-type structure or shell that is suspended within the vehicle. This operator enclosure completely surrounds the person and in some embodiments provides sealed protection against chemical and biological agents. Yet other enclosures provide armor protection from explosives and gunfire, especially to the bottom and sides of the person, such as by addition of Kevlar® or ceramic armor. The enclosure preferably includes one or more windows to the top and sides of the person to provide visibility during operation of the vehicle.  
         [0036]      FIG. 2A  is a view of vehicle  20  with body  22  and other components removed for clarity of viewing. As one example, the power train of vehicle  20  is not shown. The present invention contemplates any type of motive operation including an internal combustion engine driving two or four wheels, hydraulic motors driving one or more wheels, electric motors driving one or more wheels, and combinations of these power trains in hybrid operation.  
         [0037]     A chassis  30  includes a frame  31  which interconnects the wheel suspension units  26 . In one embodiment, vehicle  20  is adapted and configured to incur large tire deflections and large suspension movements when encountering obstacles and uneven terrain. However, the present invention is not so limited, and also contemplates those embodiments in which the tires and suspension are adapted and configured for modest deflection (such as passenger cars) and also those vehicles having solid axles and substantially rigid suspensions.  
         [0038]      FIG. 2A  includes a cradling assembly  240  centrally supported generally about the vehicle longitudinal axis by front and rear central pivot joints  46   a  and  46   c,  respectively. Cradling assembly  240  includes a main cradle  242  pivotally coupled to central pivot joints  46   a  and  46   c,  and a secondary cradle  260  pivotally supported by main cradle  242 . A payload  236   a  such as an electronic controller is attached to secondary cradle  260 .  
         [0039]      FIG. 2B  is a side view of a portion of the vehicle of  FIG. 1  as reproduced from a photograph. The body  22  and most of the cradling assembly  40  have been removed for clarity of viewing. Cradling assembly  42  is pivotally coupled to frame  31 , and is also damped relative to the movements of frame  31 . Cradling assembly  40  is also pivotally coupled to frame  31  by at least one damping unit  52 . Preferably, damping unit  52  operates with a magnetorheological (MR) fluid, and is operably attached to a controller  80 . However, various embodiments of the present invention also contemplate the use of cradle dampers  52  which utilize a conventional damping fluid. As shown in  FIG. 2B , in some embodiments, a plurality of damping units  52  are pivotally coupled to both cradle  40  and frame  31 . In one embodiment, a pair of front dampers  52   a,  a pair of rear dampers  52   b,  and a pair of central dampers  52   c  are pivotally connected to cradle  40  and also to frame  31 .  
         [0040]      FIGS. 3, 4A ,  4 B, and  5  show various views of a cradling assembly  40  which is substantially similar to cradling assembly  240 , except lacking the pivotal attachment of a secondary cradle  260 . Cradling assembly  40  includes a main cradle  42  which is pivotally coupled to bracket  34   a  of chassis  30  by a front, central pivot joint  46   a,  and to a rear bracket  34   c  of chassis  30  by a rear central pivot joint  46   c.  As best seen in  FIGS. 5 and 6 , front bracket  34   a  is rigidly attached to frame  31  by a pair of front posts  32   a.  Rear bracket  34   c  is rigidly attached to frame  31  by a pair of rear posts  32   b.    
         [0041]     Main cradle  42  includes a payload section  42   a  which is located between a front yoke  42   b  and a rear yoke  42   c.  In one embodiment, cradle  42  is symmetric about the longitudinal axis of the vehicle, and the front and rear central pivot joints  46   a  and  46   c,  respectively, are also arranged along the vehicle longitudinal axis. However, other embodiments of the present invention contemplate asymmetric cradles, as well as front and rear pivot connections to the chassis that are not aligned in a plane containing the vehicle longitudinal axis.  
         [0042]     Referring to  FIG. 4B , cradling assembly  40  includes a main cradle  42  having a payload support surface  42   g  that is located below pitch axes  46   b  and  46   d  and roll axes  46   f  and  46   g.  Preferably, support surface  42   g  is located sufficiently below roll axes  46   f  and  46   g  such that the center of gravity of the combination of the payload and cradle  42  remains below the plane  46   h  (identified with double lines) which contains both roll axes  46   f  and  46   g.  In the embodiment shown in  FIG. 3 , roll axes  46   f  and  46   g  are co-linear. However, the present invention also contemplates those embodiments in which these roll axes are not co-linear but are co-planar.  FIG. 4B  also shows that the pitch axes  46   b  and  46   d  of the central pivot joints  46   a  and  46   c,  respectively, also lie within plane  46   h.  For those embodiments of the present invention utilizing ball and socket joints for the front and rear central pivot joints, the pitch and roll axes intersect each other and also intersect the center of the ball. However, the present invention also contemplates those embodiments in which the pitch and roll axes are displaced from one another, especially in the X or Z directions, by a system of pivotal linkages.  
         [0043]      FIG. 4B  also shows that the front and rear pitch axes  54   b  and  54   d,  respectively, of the cradle  42  lie within plane  54   e  (indicated by double lines). It can be seen that in one embodiment of the present invention, cradling assembly  40  can move fore and aft in motion suggestive of a 4-bar parallelogram linkage. In this 4-bar linkage, the two long links are cradle  42  (from pivot axis  54   b  to pivot axis  54   d ) and chassis  31  (from pivot axis  46   b  to pivot axis  46   d,  which distance is established by frame  31 ). The two short links are rod  50   a  of front central pivot joint  46   a  (from pitch axis  46   b  to pitch axis  54   b ), and the corresponding rod from the rear central pivot joint  46   c  (from pitch axis  46   c  to pitch axis  54   d ). Further, main cradle  42  as drawn in  FIG. 4B  includes slotted pivot attachments  42   e  at both the front and rear.  
         [0044]     Payload section  42   a  is adapted and configured for attachment of a payload  36   a.  In one embodiment, payload  36   a  comprises one or more electronic units such as a vehicle controller, a sensor and/or its corresponding electronics, or a weapons controller. In yet other embodiments, payload  36   a  comprises a seat for an occupant or a cot for an injured passenger. Some embodiments include a main cradle having an enclosure or shell which surrounds a person within the vehicle. The enclosure is suspended inside the vehicle as described herein for other cradles. Cradling assembly  40  provides less exposure to low frequency, high amplitude accelerations for the payload.  
         [0045]     In one embodiment, vehicle  20  includes a pair of front cradle dampers  52   a  which are pivotally connected on one end to frame  31 , and which are pivotally connected on the other end to lower arm  50   d  of the front central pivot joint  56   a.  A pair of rear cradle dampers  52   b  are each pivotally connected at one end to frame  31  and to the frame of chassis  30  and at the other end to the lower arm of the rear central pivot joint  46   c.  In yet other embodiments, the main cradle  42  is also pivotally coupled on right and left sides to right and left central cradle dampers  52   c,  which are likewise pivotally connected at their other ends to frame  31  of chassis  30 . Cradling assembly  40  is thus suspended from a frame of a vehicle, and in turn the frame of the vehicle is suspended from the wheels of the vehicle, and the wheels in turn are supported from the terrain by the tires. Each of the suspension connections thus described (from terrain to the wheel; from the wheel to the frame; from the frame to the cradling assembly  40 ) permits rigid body motion of the suspended item with multiple degrees of freedom.  
         [0046]      FIGS. 6, 7  and  8  show various views of the front central attachment of cradling assembly  40 . Cradling assembly  40  provides for the pivotal, multiple degree of freedom suspension of a main cradle  42  from vehicle frame  31 . The following description also applies to the rear central attachment of cradling assembly  40 , except for the slotted pivotal attachment which will be discussed later.  
         [0047]     Front chassis bracket  34   a  captures within it a pocket or socket  34   b.  A spherical ball  50   b  is constrained by socket  34   b  such that ball  50   b  and accompanying upper and lower spring guides are rotatable about socket  34   b  in three axes. However, the present invention also contemplates those embodiments in which ball and socket joint  50   b  and  34   b,  respectively, are replaced with a universal-type joint which permits rotation about roll and pitch directions, and further includes those embodiments which permit only a single degree of rotational freedom about a pitch axis.  
         [0048]     In some embodiments of the present invention, the three degrees of freedom permitted by ball and socket joint  50   b  and  34   b  are constrained by the attached mechanisms to two degrees of freedom. For example, the connection of cradle  40  at each end to ball and socket joints effectively eliminates the ability of cradle  40  to rotate in yaw. Even so, the use of a ball and socket joint is preferred in some embodiments, because the joints do not permit bending of frame  31  to impart a Z axis moment into the suspended cradle. In addition, the use of multiple degree of freedom central pivot joints can also minimize moments that would otherwise be imparted by frame flexure about the X and the Y axes.  
         [0049]     Referring to  FIG. 7 , a rod  50   a  is slidably guided within a cylindrical hole through ball  50   b.  Rod  50   a  is securely fastened at the top to a cap  50   c,  and at the bottom to a lower arm  50   d.  Cap  50   c  and lower arm  50   d  establish lower and upper extreme limits, respectively, on vertical travel of rod  50   a  relative to ball  50   b.  The present invention also contemplates those embodiments in which lower arm  50   d  is a rigid extension of ball  50   b,  such that the lower arm cannot be vertically displaced relative to the ball and socket joint.  
         [0050]     Still referring to  FIG. 7 , central pivot joint  46   a  includes upper and lower centering springs  48   a  and  48   b,  respectively. Upper spring  48   a  is captured between the upper spring guide of ball  50   b  and the corresponding spring guide of cap  50   c.  Lower front spring  48   b  is captured between a spring guide of ball  50   b  and an opposing spring guide of lower arm  50   d.  In a preferred embodiment, each spring  48   a  and  48   b  is preloaded when assembled into front central pivot joint  46   a  so that the rigid connection of cap  50   c,  rod  50   a,  and lower arm  50   d  is suspended at a point intermediate of the upper and lower travel limits of the assembly. As one example, upper spring  48   a  is preloaded to a spring force that is greater than the portion of weight of cradling assembly  40  which would otherwise be statically supported. Further, a portion of the preload of upper spring  48   a  balances the preload of bottom spring  48   b.    
         [0051]     Lower arm  50   d  further includes means for pivotally attaching arm  50   d  to the front yoke  42   b  of main cradle  42 . In one embodiment, the pivotal connection of yoke  42   b  to arm  50   d  is a simple, single degree of freedom pivot joint, which can be accomplished with any type of bearing, including plain, ball, roller, and tapered roller as examples. The connection of the rear central pivot joint  46   c  to main cradle  42  is substantially the same as described above for the front central pivot joint  46   a,  except that rear yoke  42   c  includes a slotted hole which permits pivoting as well as limited fore and aft movement of rear yoke  42   c  relative to the rear lower arm of pivot joint  46   c  (referring to  FIG. 4A ). If frame  31  flexes in any manner such that the distance between the cradle central attachment point decreases, the slotted hole of rear yoke  42   c  permits a simple sliding of the pivot joint relative to the cradle, such that the cradle is not longitudinally loaded by the cradle central attachments. Further, the use of a slotted hole also accommodates any longitudinal differential thermal growth of frame  31  relative to cradle  42 .  
         [0052]      FIG. 9  shows a cradling assembly  140  according to another embodiment of the present invention. Cradling assembly  140  includes a main cradle  142  having a payload section  142   a  which is substantially of a ladder-type configuration. Front and rear yokes  142   b  and  142   c  are integrated into the longitudinal side rails of payload section  142   a.    
         [0053]     Front yoke  142   b  includes a lower arm  150  that has a front lower arm  150   d  that includes a longitudinally-oriented slot  142   e  for pivotal connection of yoke  142   b  to lower arm  150   d.  Preferably, the pivotal connection of rear yoke  142   c  to the rear lower arm is by way of a pivot connection to a circular hole. However, the present invention also includes those embodiments in which both the front and rear lower arms are pivotally connected to the front and rear yokes, respectively, by slotted holes.  
         [0054]      FIG. 9  also shows the connection of the four front suspension dampers  128  to chassis  30 . A pair of left side suspension dampers  128  are pivotally connected to the fore and aft sides of an ear which extends from post  132   a.  In one embodiment, the other pairs of suspension dampers  128  are likewise pivotally connected to members extending from the front and rear posts. However, the present invention is not so limited, and also contemplates those embodiments in which the suspension dampers are attached more remotely from fore and aft brackets  134   a  and  134   b.    
         [0055]      FIGS. 10 and 11  show views of a portion of a cradling assembly  240  according to another embodiment of the present invention (and as also shown in  FIG. 2 ). A main cradle  242  includes a payload section  242   a,  and front and rear yokes  242   b  and  242   c  extending therefrom. Payload section  242   a  includes right and left side pivot supports  242   f  from which a secondary cradle  260  is pivotally suspended. Cradle  260  is suspended from main cradle  204  about a pitch axis  260   g  which is substantially parallel to the pitch axis of the vehicle. A frame substantially surrounds the secondary payload section  260   a,  and further interconnects the right and left pivotal joints. Other embodiments of the present invention contemplate other arrangements for pivoting of the secondary cradle  260  relative to the main cradle  242 , including those embodiments in which the pivotal couplings are placed fore and aft of secondary cradle  260  and permit rolling motion of the secondary cradle relative to the main cradle. In yet other embodiments, secondary cradle  260  is attached by a single Z-axis oriented pivot joint to the main cradle which permits yawing motion of the secondary cradle relative to the main cradle.  
         [0056]     Still referring to  FIGS. 10 and 11 , secondary cradle  260  is also pivotally coupled to main cradle  242  by one or more pitch dampers. As best seen in  FIG. 1 , the forward end of frame  260   b  is pivotally coupled to one end of a front pitch damper  260   e,  the other end of the damper being pivotally connected to payload section  242   a  (this second connection being shown with an optional, multiple attachment hole bracket). A rear pitch damper  260   f  is likewise attached pivotally at each end to secondary cradle frame  260   b  and payload section  242   a.  As best seen in  FIGS. 10 and 2 A, front and rear secondary cradle pitch dampers  260   f  and  260   e  are preferably located along the longitudinal axis of the vehicle, although the present invention is not constrained to this mounting. Further, each damper  260   f  and  260   e  is also angled relative to a vertical axis as best seen in  FIG. 11 .  
         [0057]     The present invention contemplates those embodiments in which either or both of the secondary cradle pitch dampers utilize a conventional dampening fluid, and also those embodiments in which either or both of the secondary cradle pitch dampers employ a magnetorheological fluid. In the latter case, the MR damper is operably connected to an electronic controller which controls the properties of the fluid according to an algorithm which lowers the peak G-load experienced by the payload  236   a.    
         [0058]      FIG. 12  is a schematic representation of the interconnection of various components of vehicle  20  to each other and also to an electronic controller  80 . This figure shows a series of rigid bodies interconnected schematically by the components and assemblies previously described. Each rigid body has at least one degree of freedom relative to the adjacent, interconnected rigid bodies. Further,  FIG. 12  includes a schematic representation of various sensors and actuators interconnected to an electronic controller.  
         [0059]     Fundamentally, the first rigid body (wheel  25 ) is interconnected to the terrain T by a resilient tire  24 . Wheel  24  can move relative to a specific point of contact on the terrain along several degrees of freedom: vertically (sidewall deflection when encountering a bump B); longitudinally (such as one encountering a wall W); and roll (due to flexing of the tire sidewall when transmitting torque). Rigid body movement of the wheel in pitch, yaw, and lateral directions may also be present.  
         [0060]     The wheel (the first rigid body) is interconnected to frame  31  (a second rigid body) as represented by arrow A. Arrow A represents the linkages such as the upper and lower control arms  26  and spring/damper units  28  as best seen in  FIG. 2A . This second rigid body (frame  31 ) is able to move relative to the first rigid body in the roll, pitch, yaw, longitudinal, lateral, and vertical directions, with significantly different amounts of travel among these directions. In some embodiments, frame angular movement in roll and pitch may be significantly greater than angular movement in yaw. As another example, body  22  and frame  31  may move significantly more in the vertical direction than in the longitudinal or lateral directions relative to the wheels.  
         [0061]     This second rigid body (frame  31 ) is interconnected as represented by arrow B to a third rigid body (main cradle  242 ) by the front and rear central pivot joints  46   a  and  46   c,  centering springs  48 , and cradle dampers  52 . Main cradle  242  can move relative to frame  31  in the longitudinal direction (both as a link in a 4-bar parallelogram linkage and also as a result of longitudinal free play of slot  242   e ); in the vertical direction (acting uniformly against both front and rear centering springs); in roll (rolling about the front and rear ball and socket joints), and in pitch (accompanied by differential movement of the front and rear centering springs).  
         [0062]     In some embodiments, the third rigid body (main cradle  242 ) is further interconnected to a secondary cradle  260  as indicated by arrow C. The interconnection represented by arrow C includes the pivotal attachments  260   c  and  260   d  and the front and rear pitch dampers  260   e  and  260   f.  A payload  236   a  is shown rigidly connected to secondary cradle  260 , but as has been previously described, the payload may alternatively be connected to main cradle  242 . Secondary cradle  260  can move in the pitch direction relative to main cradle  242 .  
         [0063]      FIG. 12  also shows an electronic controller  80  such as a computer which is operably connected to various sensors and actuators. In one embodiment, computer  80  receives input from a plurality of accelerometers  82  that are located on frame  31 . These accelerometers can be oriented to provide information about acceleration in all six degrees of freedom, or only in those degrees of freedom previously discussed for frame  31 . In addition, controller  80  receives acceleration data from one or more cradle accelerometers  86  attached to main cradle  242 . Accelerometers  86  may include sensors for all six degrees of freedom, or only for those degrees of freedom previously discussed for cradle  242 . Further, the present invention contemplates those embodiments in which accelerometers can be located within the confines of the housing of the controller  80 , thus sensing acceleration of whatever the controller is mounted to.  
         [0064]     In one embodiment of the present invention, cradle dampers  52  use an MR fluid. These dampers are operably coupled to computer  80 , which includes an actuator output for applying a voltage to the dampers such that the electrified MR fluid changes its properties. This actuator input from computer  80  to dampers  52  is shown schematically by an arrow and dashed line into arrow B. In some embodiments, cradle dampers  52 , whether utilizing an MR fluid or other fluid, have incorporated into them a load sensor (such as a load cell, strain gauge, or pressure transducer, as examples) in order to calculate the force being applied by the actuator.  
         [0065]     Arrow C is representative of the interface between cradles  242  and  260  includes at least one secondary cradle damper  260   e,  with some embodiments having multiple secondary cradle dampers. These dampers  260   e  and  260   f  utilize MR fluid in some embodiments and conventional hydraulic fluid in other embodiments. For those embodiments utilizing the MR fluid, the dampers  260  are adapted and configured to impose the voltage applied by the corresponding actuators of computer  80  onto the MR fluid so as to change its fluid properties. In some embodiments, dampers  260   e  and  260   f  also employ a sensor for measuring the force applied by the damper for use in calculation performed by computer controller  80 .  
         [0066]     For those embodiments of the present invention utilizing cradle dampers that use conventional hydraulic fluid, dampers  52  respond primarily to differences between the relative velocities of frame  31  and cradle  242 . A sudden G input to frame  31  (such as when body  22  runs into a wall), is not transmitted immediately into cradle  242 , since the relative velocity of frame  31  to cradle  242  (which prescribes the force of the dampers) lags behind the relative acceleration of frame  31  relative to frame  242 . Thus, the harsh effects of an impact to vehicle  20  are softened by the damped suspension represented by arrow B.  
         [0067]     In those embodiments of the present invention in which one or more of the cradle dampers ( 52  or  260 ) utilize an MR fluid, computer  80  can change the damping characteristics of the particular damper, based on a measurement of the load applied by that damper, and further based on a controlling algorithm which describes the desired relationship of frame acceleration to payload (i.e. cradle acceleration). The present invention also contemplates those embodiments in which some dampers utilize an MR fluid, and other dampers do not.  
         [0068]     In those embodiments having an internal enclosure or shell for a person, the damping characteristics can be controlled to orient the suspended enclosure in a manner which increases the person&#39;s awareness of the vehicle environment. As one example, the damping characteristics can be controlled to offer haptic feedback from the vehicle environment to the person. As another example, the damping characteristics can be adjusted to minimize the deviation of the roll angle of the shell from the horizontal, so as to maintain the person&#39;s head and inner ear relatively level. Such roll stabilization can help the person maintain eye or weapon contact with a target. This stabilization can also increase the comfort of and reduce motion induced injuries to a wounded person being transported to medical care.  
         [0069]     One embodiment of the present invention pertains to a vehicle having a plurality of wheels in contact with a surface, and a frame suspended from the wheels. This embodiment of the invention includes a platform which is suspended on opposite sides by pivotal joints. Each pivotal joint permits rotation about two orthogonal axes. The platform includes a mounting surface located below the pivotal joints. In a different embodiment, the two joints are laterally spaced apart and coupled to the frame. In yet other embodiments each of the two joints are suspended vertically between top and bottom springs. In yet other embodiments at least one of the top springs is preloaded.  
         [0070]     In yet another embodiment of the present invention, there is a vehicle with wheels for traversing over a surface. The vehicle includes a frame which is suspended from the wheels by a plurality of springs or shock absorbers. A cradle is pivotally supported by the frame with at least two pivotal attachments. Each pivotal attachment permits rotation about each of three orthogonal axes.  
         [0071]     In yet another embodiment of the present invention there is a vehicle with a plurality of wheels, each of the wheels being pivotally coupled to a frame of the vehicle. The vehicle includes a plurality of shock absorbers, each shock absorber being pivotally coupled at one end to the frame and pivotally coupled at the other end to either a wheel or a suspension component. The vehicle includes first and second attachment arms, each attachment arm being pivotally coupled to the frame by a joint that permits rotation about a corresponding axis. The vehicle further includes a cradle that is pivotally coupled at the first end to the first arm, and pivotally coupled at the second end to the second arm. Each of the joints connecting the cradle to the arms permits rotation about a corresponding axis. Each of the four axes thus described are parallel to each other.  
         [0072]     In another embodiment of the present invention there is a vehicle having a frame and a plurality of wheels, each of the wheels being pivotally coupled to the frame and biased apart from the frame by a corresponding biasing unit such as a spring. The vehicle also includes a cradle that is pivotally attached to the frame at two attachments. Each attachment permits rotation in the roll and pitch directions. The cradle is adapted and configured to support a payload such that the center of gravity of the payload is below the roll and pitch axes of the first attachment and below the roll and pitch axes of the second attachment.  
         [0073]     Yet another embodiment of the present invention pertains to a vehicle having a frame and wheels, the frame being pivotally coupled to the wheels, each wheel being biased away from the wheel by a spring or shock absorber. A cradle is pivotally coupled to the frame by at least two pivot joints that are spaced apart. The vehicle further includes at least one dampening unit that is pivotally coupled at one end to the cradle and pivotally coupled at the other end to the frame. In yet another variation of this embodiment, the dampening unit operates with a magnetorheological fluid, and the vehicle includes a computer operably connected to the damper to modify the dampening characteristics based on a sensed parameter.  
         [0074]     Yet another embodiment of the present invention pertains to a vehicle having a frame and wheels, the wheels being pivotally coupled to the frame, the frame being biased apart from each of the wheels. A cradle is pivotally coupled to the frame. The cradle and the pivotal couplings are adapted and configured to permit limited movement of the cradle to translate longitudinally, and to rotate about roll and pitch axes. In yet a variation of this embodiment there is a second cradle which is pivotally coupled to the first cradle. The second cradle, first cradle, and the pivotal attachment are adapted and configured to permit limited pitching motion of the second cradle relative to the first cradle. In either of these two embodiments there is a plurality of dampening units pivotally connected at one end to the first cradle and pivotally connected at the other end to the frame. In either of those same two embodiments there can be at least one dampening unit pivotally coupled at a first end to the first cradle and pivotally coupled at a second end to a second cradle.  
         [0075]     While the inventions have been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiment has been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected.