Abstract:
A tow bar for connecting and controlling two autonomous vehicles with respect to one another. The tow bar including a plurality of sections with at least one sensor, mounted or coupled onto each, for measuring and determining the orientation of one autonomous vehicle in relation to the other autonomous vehicle. A signal may be transmitted to either or to both of the autonomous vehicles to control propulsion and/or steering and/or braking of the vehicles when an adjustment is required to maintain stability of the tandem vehicles.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     This invention relates to the towing of one autonomous vehicle by another autonomous vehicle, and, more particularly, to a tow bar connected between the vehicles and providing information as to vehicle orientation and traction to a controller of vehicle operation.  
         [0002]     Towing needs are present in a variety of situations. A tractor may pull a trailer along a highway, may pull a farm implement such as a sprayer between crop rows, or may pull an aircraft into a hangar. A common aspect of the above situations is that the terrain is generally level and the vehicle under tow is unpowered. The trailer or towed vehicle may have independent steering and braking ability, but generally lacks independent propulsion.  
         [0003]     Other environments where towing is required are less accommodating. For example, the terrain may be off road and include slopes of hills and mountains. Within a short distance, traction may change from firm to absent as the traction available to individual vehicle wheels is reduced as a result of contact with loose rocks, mud, ice, snow, or wet pavement. There is the ever present danger of a trailer slipping out of control and endangering both vehicles.  
         [0004]     Further, current tow bars do not provide control signals for control of propulsion, braking, and steering to the vehicles based on information provided by the tow bar. Currently, in towing situations, most tow bars are passive in nature. Some have been designed to allow for a fairly simple braking control of the towed vehicle. In some instances separate brake control units are available to allow for brake application in the towed vehicle. By themselves, independent steering and braking for the tractor and the trailer may not be able to preserve a tandem arrangement of the vehicles where the towed vehicle follows directly behind the towing vehicle.  
       BRIEF SUMMARY OF THE INVENTION  
       [0005]     The needs for the present invention set forth above as well as further and other needs and advantages of the present invention are achieved by the embodiments of the invention described herein below.  
         [0006]     According to one aspect of the invention, a tow bar for connecting a first autonomous vehicle to a second autonomous vehicle in a tandem arrangement includes several sections—a first section coupled to the first autonomous vehicle and to a strain module, a second section coupled to the strain module and to a roll sensor, a third section coupled to the roll sensor and to a first angular sensor, a fourth section coupled to the first angular sensor and to a second angular sensor, and a terminal section coupled to the second angular sensor and to the second autonomous vehicle. In other embodiments of the invention, the terminal section comprises a fifth section coupled to the second angular sensor and to a sixth section and to a seventh section, and the sixth section and the seventh sections coupled to the fifth section and to the second autonomous vehicle. The exact number of sections may vary within the scope of the present invention.  
         [0007]     In certain embodiments of the invention, the roll sensor may detect a roll angle between the first and second sections, the first angular sensor a pitch angle between the third and the fourth sections, and the second angular sensor a yaw angle between the fourth and the terminal sections. In other embodiments, the sixth and the seventh sections may be adjustable in length where each may include a plurality of subsections held in position by biasing mechanisms, which may be spring pins.  
         [0008]     According to another aspect of the invention, a method for maintaining a tandem arrangement of a first autonomous vehicle and a second autonomous vehicle includes measuring at least one angle characterizing an orientation of the first autonomous vehicle relative to the second autonomous vehicle, measuring a force between the first and second autonomous vehicles, and determining acceleration, braking, and steering of the second autonomous vehicle on the basis of the measured angle and force, and effecting the acceleration, braking, and steering to maintain the tandem arrangement.  
         [0009]     In other embodiments, the measured angle may be a roll angle and may be measured with a roll sensor, may be a pitch angle and may be measured with an angular motion sensor, or may be a yaw angle and may be measured with an angular motion sensor. In another embodiment, the method may include transmitting the measured angle to a controller. In a further embodiment, the force between the first and second autonomous vehicles may be measured with a strain module. In a still further embodiment, the method may include transmitting the measured force. In a certain embodiment, the method may also include determining likelihood of a roll over of the tandem arrangement.  
         [0010]     According to a further aspect of the invention, a system for maintaining a tandem arrangement of a first autonomous vehicle and a second autonomous vehicle includes means for measuring at least one angle characterizing an orientation of the first autonomous vehicle relative to the second autonomous vehicle, means for measuring a force between the first and second autonomous vehicles, means for determining an acceleration, braking, and steering of the second autonomous vehicle on the basis of the at least one measured angle and measured force, and means for effecting the acceleration, braking, and steering of the second autonomous vehicle to maintain the tandem arrangement.  
         [0011]     In one embodiment of the invention, the system includes means for transmitting the measured angle. In another embodiment, the system may include means for transmitting the measured force.  
         [0012]     According to a further aspect of the invention, a multi-vehicle control system includes a first vehicle, a second vehicle, and a tow bar. The tow bar interconnects the first vehicle with the second vehicle and includes a plurality of sections and at least one sensor. The sensor is coupled to at least one of the sections and is capable of measuring an orientation of the first vehicle in relation to the second vehicle.  
         [0013]     In another embodiment of the invention, the tow bar includes a first section coupled to the first autonomous vehicle and to a strain module, a second section coupled to the strain module and to a roll sensor, a third section coupled to the roll sensor and to a first angular sensor, a fourth section coupled to the first angular sensor and to a second angular sensor, and a terminal section coupled to the second angular sensor and to the second autonomous vehicle.  
         [0014]     In a further embodiment of the invention, the terminal section comprises a fifth section coupled to the second angular sensor and to a sixth section and to a seventh section, and the sixth section and the seventh sections coupled to the fifth section and to the second autonomous vehicle.  
         [0015]     For a better understanding of the present invention, together with other and further needs thereof, reference is made to the accompanying drawings and detailed description. Its scope will be pointed out in the appended claims. 
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0016]      FIG. 1  is a schematic of a tractor-trailer combination pulling a second nonautonomous trailer mounted on a prior art nonautonomous steerable dolly;  
         [0017]      FIG. 2  is a pictorial of an embodiment of the present invention where the tow bar of this invention connects an autonomous utility vehicle with an autonomous companion trailer;  
         [0018]      FIG. 3A  is a pictorial of the tow bar embodiment of the present invention shown in  FIG. 2  illustrating the various interconnected sections;  
         [0019]      FIG. 3B  is a pictorial of  FIG. 3A  illustrating the interconnection of two leg sections by a spring pin;  
         [0020]      FIG. 3C  is a pictorial of another tow bar embodiment of the present invention including a terminal section.  
         [0021]      FIG. 4A  is a pictorial of the tow bar embodiment of the present invention shown in  FIGS. 2 .  3 A, and  3 B illustrating various sensors mounted to the interconnected sections;  
         [0022]      FIG. 4B  is a schematic block diagram illustration of the UV controller and the control loop of the present invention;  
         [0023]      FIG. 5  is a pictorial representing several angles that characterize the orientation of the autonomous companion trailer with respect to that of the autonomous utility vehicle;  
         [0024]      FIG. 6  is a process flow diagram illustrating one logical method for correcting the orientation of one autonomous vehicle relative to another autonomous vehicle in the present invention;  
         [0025]      FIG. 7  is a process flow diagram of a closed loop control circuit for preserving the tandem arrangement of a first and a second autonomous vehicle in the present invention; and  
         [0026]      FIG. 8  is a pictorial of an embodiment of the present invention illustrating orientation sensors attached to the tow bar. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0027]     Independent propulsion, in addition to independent braking and steering, on a pulled vehicle, such as a trailer, is characteristic of an autonomous vehicle and allows for control of a tandem arrangement of a pulling vehicle, such as a tractor, and the trailer that is absent when only the tractor has propulsion and, consequently, is autonomous. However, preservation of the tandem arrangement of the two vehicles depends upon knowledge of the traction condition of both vehicles and the orientation of one vehicle with respect to the other. On the basis of traction and orientation information of the vehicles, propulsion, steering, and braking of one or both vehicles may be adjusted to achieve a stable tandem arrangement where the trailer follows directly behind and in line with the tractor.  
         [0028]     There are reasons for providing trailers with independent propulsion. For example, transport vehicles may be more easily loaded onto and unloaded from airplanes or ships if they have their own means of movement and do not have to rely on an independent tractor or sheer manpower. Further, efficiency is enhanced if several transport vehicle are attached so that only a single driver is needed. Coincidentally, because of the nature of certain missions, transport vehicles are likely to encounter the variability of terrain that tends to disrupt a tandem relationship.  
         [0029]     Control of an independently powered tandem arrangement of a tractor and a trailer depends upon acquisition and transmission of accurate orientation and traction information to a controller for processing into steering, braking, and acceleration instructions to the tractor and trailer. This information may be acquired by means independent of the tractor and trailer since such means are necessary only when the tractor and trailer are attached and not when they are separated. An intelligent tow bar, as further described below, may provide such orientation information.  
         [0030]      FIG. 1  illustrates a typical tandem tractor/trailer arrangement in operation today. A tractor  110  pulls a nonautonomous trailer  120 , which is pulling a dolly  130 , which itself is pulling a second nonautonomous trailer  140 . The dolly  130  may have its own steering and braking capabilities that can be employed by a driver  150  of the tractor I  10  to supplement the actions of the tractor  110 , for example, braking the dolly  130  when the tractor  110  is braked or steering the dolly  130  in the direction in which the tractor  110  is steered. However, if the second trailer  140  begins to fall out of alignment, that is, to jackknife or to tip, the second trailer  140  and the dolly  130  can do little to correct the difficulty. There is no facility to sense the actions of the second nonautonomous trailer  140  or to use a separate propulsion system to avoid or circumvent a difficult situation.  
         [0031]      FIG. 2  illustrates one embodiment of the tow bar  230  of the present invention connecting or coupling an autonomous tractor or utility vehicle (UV)  210  to an autonomous trailer or companion trailer (CT)  220 . In this case, the CT  220  is essentially a cab-less truck capable of both autonomous operation and being towed behind the UV  210 . The CT  210  may contain the same propulsion system and drive components as the UV  210  or different ones.  
         [0032]     For towing the CT  220  with the UV  210 , there will be instances when the CT  220  should be under active control of the UV  210  to insure that the UV/CT tandem  215  stays in control and does not endanger vehicle driver  240  or equipment  245 . The UV  220  needs to control the CT brakes  250 , steering  260 , propulsion  270  (diesel, electric, diesel/electric hybrid or any other drive system), and other subsystems, such as lights  290  and parking brakes  295 . Closed loop control feedback to the UV controller  280  based upon monitoring of CT operation, allows correction of control problems and allows alert to the UV driver  240  of potential problems. Given the mission profile, such as resupply necessitating a large payload divided between the UV and the CT, lack of CT control could lead to overall UV/CT  215  tandem control concerns, such as sliding down a steep grade, tipping over, jack knifing, or otherwise causing instability of the tandem arrangement.  
         [0033]     In certain instances, control of the CT  220  may simply follow commands of the UV driver  240  to the UV  210 . For example, when the driver  240  in the UV  210  engages the UV brake  255 , or alternatively commands acceleration, the CT  220  will be directed to brake, or to accelerate, as well. However, if the CT  220  is in a different situation than is the UV  210 , the CT  220  may respond to the commands in a manner that differs from the response of the UV  210  to those commands. For instance, if the CT  220  has better, or worse, traction than does the UV  210 , the CT  220  may hinder UV/CT tandem  215  operation and may place the driver  240  and/or the equipment  245  in jeopardy. Therefore, the UV controller  280  needs to be aware of CT  220  conditions.  
         [0034]      FIG. 3A  illustrates an embodiment of the tow bar  230  for providing situational awareness of the CT  220  to the UV  210  and to the UV controller  280 , leading to closed loop control via positive control feedback to the UV controller  280 . (A block diagram of a closed loop control circuit including UV controller  280  is provided in  FIG. 4B  and process flow diagrams illustrative of two methods of control are provided in  FIGS. 6 and 7 .) In providing CT operational status data to the UV  210  or UV controller  280 , the tow bar  230  can inform the UV  210  or UV controller  280  if the CT  220  is tending to drag, or push, relative to the UV  210 . The tow bar  230  can also monitor whether the CT  220  is maintaining a proper following orientation, and not, for example, slipping on a scree—or small rock-covered side slope traverse.  
         [0035]     As illustrated in  FIGS. 2, 3A , and  3 B, the tow bar  230  forms a fixed length three-point connection between the CT  220  and UV  210 . The tow bar  230  uses links  310  and  312  to attach to forward tow provisions  235  on the CT  220  and the receiver mount neck  320  to the towing receiver  237  on the UV  210 . Built in pivots  311  and  313  allow the desired variation in UV/CT vehicle alignment when hooking up. Additionally, leg  314  and leg  315  of the tow bar  230  have biasing mechanisms, shown as spring pin  316  and spring pin  317  respectively, that allows the lengths of leg  314  and leg  315  to vary during hook up. Then, pin  368  passes through a hole  370  in a first section  360  of leg  314  and rides on top of a second section  362  of leg  314 . Once linked, the driver  240  simply drives forward or backward so as to cause the pin  368  to engage in a hole  372  of the second section  362 , thereby fixing the length of leg  314 . Similarly, the length of the leg  315  is fixed. As a result, the leg  314  and the leg  315  form a fixed length connection with the receiver mount neck  320 .  
         [0036]      FIG. 3C  illustrates another embodiment of the invention where a terminal section  380  enables the tow bar  230  to form a fixed length connection between the CT  220  and the forward tow provisions  235  on the CT  220 . In this embodiment, the length of the tow bar  230  is not adjustable, as was the case in the embodiment illustrated in  FIGS. 3A and 3B .  
         [0037]     As shown in  FIG. 4A , the tow bar  230  includes a plurality of sensors to measure the orientation of the CT  220  relative to the UV  210  and the pulling or pushing force exerted by the CT  220  on the UV  210 . This data input is employed by the UV controller  280 , shown schematically in  FIG. 4B , to direct the CT  220  to execute steps to insure that the CT  220  follows properly behind the UV  210 .  
         [0038]     Where the UV  210  simply tows the CT  220  over fairly even improved roads, the tow bar  230  may act as a conventional tow bar and simply pull the CT  220 . However, most towing of the CT  220  by the UV  210  occurs off-road on un-improved roads. Given the requirements of grade climb/descend and traverse, a significant amount of control of the CT  220  will be required to prevent accidents like roll-overs. The intelligent tow bar  230  may provide one source of information to allow the CT  220  to be accelerated, braked, or steered in order to maintain control. This also allows for “torque blending” of UV  210  and the CT  220  vehicles to optimize performance in off road driving. The requisite amount of power to move the tandem arrangement  215  is divided between the UV  210  and the CT  220 , not overly taxing either vehicle and taking advantage of the vehicle and wheels having the most traction.  
         [0039]     As illustrated in  FIG. 4A , first section, receiver mount neck,  320 , couples to the UV  210  at a first end  420  and to a second section  425  at a second end  421  via a tension/compression strain module  422 . The second section  425  couples to a third section  430  via a roll sensor  427 , which may be a rotary encoder. The third section  430  pivotally couples to a fourth section  435  via a first angular motion sensor  433 . The fourth section  435  couples to a fifth section  440  via a second angular motion sensor  437 . The fifth section  440  also couples to a sixth section  445  or leg  314  and seventh section  447  or leg  315 . In the embodiment of  FIG. 3C , the terminal section  380  plays the role of the fifth  440 , sixth  445 , and seventh  447  sections in coupling between the second angular motion sensor  437  and the CT  220 .  
         [0040]     Transmission of the status of the tension/compression strain module  422 , together with the status of the roll sensor  427  and first  433  and second  437  angular motion sensors to UV controller  280  provides the UV controller  280  with the extent to which the UV  210  pulls or is pulled by the CT  220  and the relative orientations of the CT  220  with respect to the UV  210 .  
         [0041]     As illustrated in  FIG. 4B  for control loop  400 , the UV controller  280  receives UV status indicators  470  over a UV/CT communications bus  478 . UV status indicators  470  may include a UV braking status  472 , a UV speed status  474 , and a UV steering angle  476 . The UV controller  280  also receives tow bar orientation status indicators  420  from the tow bar  230 . The tow bar orientation status indicators  420  include signals from the tension/compression strain gauge or module  422 , the roll sensor  427 , and the first  433  and the second  437  angular motion sensors. The first angular motion sensor  433  includes a pitch angle motion sensor and the second angular motion sensor  437  includes a yaw angle motion sensor.  
         [0042]     On the basis of the UV status  470  and tow bar orientation status  420  indicators, the UV controller  280  provides UV control signals  450  and CT control signals  460 . The UV control signals  450  may include a UV braking control  452 , a UV propulsion control  454 , and a UV steering control  456 . The CT control signals  460  may include a CT steering control  462 , a CT propulsion control  464 , and a CT braking control  466 .  
         [0043]      FIG. 5  illustrates the association of the angles with the relative orientation. Roll sensor  427  provides a measure of a roll angle  510  of the CT  220  relative to the UV  210 , first angular motion sensor  433  of a pitch angle  520  of the CT  220  relative to the UV  210 , and second angular motion sensor  437  of a yaw angle  530  of the CT  220  relative to the UV  210 . UV steering angle  540  is the angle between the direction  544  in which UV steering wheels  580  are pointing and the direction  542  in which the UV  210  is pointing. CT steering angle  560  is the angle between the direction  564  in which CT steering wheels  590  are pointing and the direction  562  in which the CT  220  is pointing.  
         [0044]     With the distance between towing provisions fixed along with the length of tow bar legs  314  and  315 , sensors provide measures of angular differences, rotational differences, and tension/compression in the tow bar  230 . This sensory input then forms one source for control information for closed loop control of the CT  220  by the UV  210 , as shown in the process flow diagrams of  FIGS. 6 and 7 .  
         [0045]      FIG. 6  provides a process flow diagram  600  illustrating one logical method for correction of the orientation of the CT  220  vehicle relative to the UV  210 . Upon input of the CT yaw angle  530  in step  610 , the CT pitch angle  520  in step  620 , the roll or rotary angle  510  in step  630 , and the UV steering angle  540  in step  640 , the CT steering angle  560  is adjusted to match the UV steering angle in step  650 . The pitch angle  520 , the yaw angle  530 , and the rotary angle  510  are then assessed in steps  660 ,  670 , and  680 , respectively, to determine whether any are out of bounds. If the pitch angle  520  is out of bounds, the UV  210  and the CT  220  are slowed in step  665 . If the yaw angle  530  is out of bounds, the UV  510  is slowed, the CT  220  is braked, and the steering of the CT  220  is adjusted in step  675 . If the rotary angle  510  is out of bounds, the UV  220  and the CT  210  are braked and the operator or driver  240  is alerted in step  685 .  
         [0046]      FIG. 7  provides a process flow diagram  700  of a closed loop control circuit for preserving the tandem arrangement of the UV  210  and the CT  220 . Following input of the speed of the UV  210  in step  710  and the speed of the CT  220  in step  720 , the speed of the CT  220  is set to match the speed of the UV  210  in step  730 . Following input of a signal from the strain gauge  422  in step  740 , if the strain is found to be positive in step  750 , propulsion of the CT  220  is increased in step  755 . If the strain is found to be negative in step  760 , propulsion of the CT  220  is decreased in step  765 . Following input of the UV steering angle  540  in step  770 , the CT steering angle  560  is matched to the UV steering angle  540  in step  780 . If the yaw sensor  437  indicates an under value in step  790 , the CT  220  is oversteered in step  795 . If the yaw sensor  437  indicates an over value in step  800 , the CT  220  is understeered in step  805 .  
         [0047]     In some instances of towing, such as on improved roads over even terrain it may not be necessary to have this tight control. For reasons of fuel conservation it may be desirable to not run the CT propulsion system. However it may still be necessary to control steering, and it will always be necessary to control brakes. The intelligent tow bar  230  may provide input in any case if desired.  
         [0048]      FIG. 8  illustrates another embodiment of the present invention where a first orientation sensor  810  may be attached to the receiver mount neck  320 , fixed with respect to the UV  210 , and a second orientation sensor  820  attached to the leg  314 , fixed with respect to the CT  220 . The first orientation sensor  810  and the second orientation sensor  820  may transmit a first and a second output to the UV controller  280  by wire or wireless connection (as shown in  FIG. 8 ). Based at least in part on the outputs of the first orientation sensor  810  and the second orientation sensor  820  outputs, the UV controller  280  may determine the orientation of the CT  220  relative to the UV  210 , and, in conjunction with the output provided by the tension/compression strain module  422  mounted on the tow bar  230 , may determine a UV propulsion, braking, and steering and a CT propulsion, braking, and steering that, upon implementation by the UV  210  and the CT  220 , restores and preserves the inline tandem relationship between the UV  210  and the CT  220 . The first orientation sensor  810  and the second orientation sensor  820  may include gyroscopes that may further include angular rate sensors, accelerometers, and magnetometers in combination with transmitters.  
         [0049]     Although the invention has been described with respect to various embodiments, it should be realized that this invention is also capable of a wide variety of further and other embodiments within the spirit and the scope of the appended claims.