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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
As illustrated in
As shown in
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.
As illustrated in
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.
As illustrated in
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.
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
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.
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.