Abstract:
A cargo lift system employs multiple unmanned lift vehicles acting as vertical lift generating machines. An autonomous control system controls coordinated movements of the cooperating unmanned vertical lift generating machines. A coupling system connects the cargo load to each of the plurality of unmanned vertical lift generating machines. The plurality of unmanned vertical lift generating machines are separated from each other by a distance through spacing by individual onboard flight computers in the lift generating machines or by rigid or semi-rigid connections between the lift generating machines.

Description:
BACKGROUND INFORMATION 
     1. Field 
     Embodiments of the disclosure relate generally to the field of vertical lift cargo vehicles and more particularly to a vertical lift system employing one or more UAV&#39;s incorporating control and interconnection systems to cooperatively lift payloads of various sizes with the number of UAVs employed determined by the payload size. 
     2. Background 
     Vertical lift systems for moving personnel and cargo have become ubiquitous in modern military and civil transportation. Helicopters range in size from light personnel carrying machines such as the Robinson R-22 or Bell OH-58 Kiowa to very large cargo lifting vehicles such as the Sikorsky CH-53 Sea Stallion or Boeing Vertol CH-47Chinook, which are dual purpose personnel or cargo transport, or cargo dedicated vehicles such as the Sikorsky S-64 Skycrane or Kaman KMAX. Heavy lift vehicles such as the Skycrane or KMAX often provide more lift performance than necessary for smaller cargo tasks. Both large capacity cargo dedicated systems and dual purpose systems are often expensive to design, operate and maintain. It is therefore desirable to provide a vertical lift cargo system that can be matched to varying cargo lift requirements 
     SUMMARY 
     Embodiments disclosed herein provide a cargo lift system employing a plurality of unmanned lift vehicles acting as vertical lift generating machines. An autonomous control system controls coordinated movements of the plurality of unmanned vertical lift generating machines. A coupling system connects the cargo load to each of the plurality of unmanned vertical lift generating machines. The plurality of unmanned vertical lift generating machines are separated from each other by a distance through spacing by individual onboard flight computers in the lift generating machines or by rigid or semi-rigid connections between the lift generating machines. 
     Operation of the embodiments disclosed for cargo lift may be accomplished by determining a load weight and configuration and selecting a number of individual lift vehicles required to provide the necessary lift. The individual lift vehicles are then assembled into a multiple vehicle configuration (MVC). If the MVC is to be operated without physical connection between lift vehicles, individual lift vehicle control is implemented through an onboard flight controller in each lift vehicle to maintain lift vehicle separation using vehicle encoded mutual range sensing. Autonomous control of the MVC is provided by an elected master controller with individual collective and cyclic control of each lift vehicle by an onboard flight computer for MVC flight path control. If the MVC is operated with physical connection with semi-rigid beams, the beams are connected between lift vehicles of the MVC to a ball joint in an interconnection and load support module of each lift vehicle. Autonomous control of the MVC is provided by the master controller with individual collective and cyclic control of each lift vehicle by each onboard flight computer for MVC flight path control. If the MVC is operated with physical connection with rigid beams, the beams are connected between lift vehicles of the MVC to a rigid connection in the in the interconnection and load support module of each lift vehicle. Autonomous control of the MVC is then provided by the master controller with individual collective and cyclic control of each lift vehicle by each onboard flight computer for MVC flight path control. Alternatively for MVCs with three or four lift vehicles, autonomous control of the MVC is accomplished with individual collective control of each lift vehicle by each onboard flight controller responsive to the autonomous controller for pitch and roll control of the MVC for MVC flight path control. 
     The features, functions, and advantages that have been discussed can be achieved independently in various embodiments of the present disclosure or may be combined in yet other embodiments further details of which can be seen with reference to the following description and drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a pictorial view of an exemplary embodiment with communication coupling between the vertical lift vehicles; 
         FIG. 1B  is a pictorial view of an exemplary embodiment with physical coupling between the vertical lift vehicles in addition to communication coupling; 
         FIG. 2A  is an isometric view of one example vehicle employed in the embodiment of  FIG. 1 ; 
         FIG. 2B  is a side view of the vehicle; 
         FIG. 2C  is a top view of the vehicle with the rotor disk removed for clarity; 
         FIG. 3  is a pictorial view of an example of load matching with a single vehicle; 
         FIG. 4A  is a pictorial view of an example of load matching with a cooperative pair of lift vehicles; 
         FIG. 4B  is a side view of the cooperative pair of lift vehicles; 
         FIG. 5A  is a pictorial view of an example of load matching with a cooperative triplet of lift vehicles; 
         FIG. 5B  is a front view of the cooperative triplet of lift vehicles; 
         FIG. 6A  is a pictorial view of an example of load matching with a cooperative quadruplet of lift vehicles; 
         FIG. 6B  is a top view of the cooperative quadruplet of lift vehicles; 
         FIG. 7A  is an example of cooperative interaction by lift vehicles with no physical connection; 
         FIG. 7B  is an example of cooperative interaction by lift vehicles with a semi-rigid connection; 
         FIG. 7C  is an example of cooperative interaction by lift vehicles with a rigid physical connection; 
         FIG. 8  is a schematic diagram of elements of a semi-rigid connection of lift vehicles; 
         FIG. 9  is a schematic diagram of elements of a rigid connection of lift vehicles; 
         FIG. 10  is a schematic block diagram of the elements of the lift vehicle connection and control systems for cooperative control; 
         FIG. 11  is a block diagram of the operation of the control systems and instrumentation for cooperative control of the lift vehicles; 
         FIG. 12  is a schematic diagram of cooperative communications between the lift vehicles and a base station; 
         FIG. 13  is a schematic diagram of load handling by cooperating lift vehicles; 
         FIG. 14  is a representation of control interaction between cooperative lift vehicles with an obstructed view; 
         FIG. 15  is a schematic diagram of the emergency disconnect system for the cooperative lift vehicles; and, 
         FIG. 16  is a flow chart of selection and operation of MVC configurations for matched loads. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments disclosed herein provide a vertical lift system with multiple lift vehicles operating as vertical lift generating machines that can modularly interact to cooperatively lift varying payloads. Connection between the lift vehicles can be rigid, flexible or by control system interaction only. Small loads may be lifted with one lift vehicle, larger loads with two interconnected lift vehicles, yet larger loads with three interconnected lift vehicles and maximum loads with four or more interconnected lift vehicles. 
     Referring to the drawings,  FIGS. 1A and 1B  show exemplary cases for a modularly connected vertical lift vehicle system  10  lifting of a payload  12  using three lift vehicles  14   a ,  14   b  and  14   c  supporting the payload with cables  18   a ,  18   b  and  18   c . For the embodiment shown in  FIG. 1A , the lift vehicles are not physically connected but operate cooperatively using mutual sensing and communication for maintaining spacing and cooperative lift and movement of the payload  12  as will be described in greater detail subsequently. For the embodiment shown in  FIG. 1B , interconnection of the vehicles using connection beams  16   a ,  16   b  and  16   c  is employed with vehicle interaction as will be described in greater detail subsequently. Payload  12  is supported by cables  18   a ,  18   b  and  18   c  from the lift vehicles. 
     Details of an example embodiment for the modular lift vehicles  14  are shown in  FIGS. 2A ,  2 B and  2 C. A fuselage  20  provides a base structure for the vehicle with co-axial, counter-rotating rotor discs  22   a  and  22   b  driven by a propulsion unit  24 . Landing gear  26  support the vehicle on the ground when not in use. An interconnection and load support module  28  is provided for interconnection between the vehicles and as a coupling system for connection of load cables or slings to carry the load  12 . In alternative embodiments, the vehicle interconnection elements and load coupling system may be separately accommodated. A sensor suite  29  including elements such as and inertial measurement unit (IMU) and/or global positioning system (GPS), video cameras, laser imaging, detection and ranging (LIDAR) and/or radar sensors are provided for navigation and control as well as mutual position sensing for lift vehicles operating cooperatively. For an example vehicle, 45 ft. diameter rotors with a 4.5 ft axial spacing are employed. The propulsion unit provides a total of 8,888 shp in an example embodiment using one or more turboshaft engines such as GE-38B by General Electric. With an empty weight of 12,000 lbs and 3,000 lbs of fuel for approximately 200 nm range, payload of 15,000 lbs results in a total gross weight of the lift vehicle of approximately 30,000 lbs. 
     Depending on cargo load, the modular lift vehicles  14  may operate independently as shown in  FIG. 3 , or with multiple vehicle configurations (MVC) as a cooperative pair,  14   a ,  14   b , (MVC2) as shown in  FIGS. 4A and 4B , a cooperative triplet  14   a ,  14   b  and  14   c  (MVC3) as shown in  FIGS. 5A and 5B  or a cooperative quadruplet,  14   a ,  14   b ,  14   c  and  14   d  (MVC4) as shown in  FIGS. 6A and 6B . In each example case, the interconnection between the vehicles shown is a beam connection which may be rigid or semi-rigid, as will be described in greater detail subsequently, however, the cooperating lift vehicles may operate at a spaced distance without physical interconnection as will also be described subsequently. Example loads for a single lift vehicle would be a payload of between 10,000 and 15,000 lbs such as a HUMVEE military vehicle or commercial loads such as 463 L pallets, logging or fire fighting loads. A MVC2 may be employed for a payload of between 15,000 and 30,000 lbs such as a M-ATV or commercial loads such as high rise construction or oil and gas rig payloads. A MVC3 may lift between 30,000 and 45,000 lbs for such loads as a STRYKER combat vehicle or commercial loads such as high rise construction or oil and gas rig payloads. A MVC4 may lift between 45,000 and 60,000 lbs to accommodate portable fuel tanks, construction equipment, high rise construction or oil and gas rig payloads. 
     The modular cooperative system for carrying loads with multiple lift vehicles provides an individual lift vehicle control system that adjusts, as a function of the MVC and the position of the individual lift vehicle within the configuration to compute a desired attitude and position with respect to the other lift vehicles. Formation flight algorithms known in the art may be employed as an autonomous control system to cooperatively “fly” the MVC under common guidance by an elected master controller or similar approach with each lift vehicle controlled by an onboard flight computer as will be described in greater detail subsequently. Communications between the individual lift vehicles in the MVC may employ a wireless system such as a radio interlink or other communication system including a wired or optical fiber system where physical interconnection of the lift vehicles in the MVC is present. Each flight computer would be used to process the incoming sensor data, and apply the control algorithm to direct each individual vehicle to act as cooperative system when linked with other vehicles. 
     Cooperative operation of the modular lift vehicles can be accomplished with control system interaction only and no physical connection as shown in  FIG. 7A  with an exemplary MVC2 configuration having vehicles  14   a  and  14   b . The control systems of the lift vehicles maintain a safe operating distance between individual lift vehicles. Physical connection between lift vehicles can be accomplished with a semi-rigid connection shown in  FIG. 7B  having a beam  16  interconnecting vehicles  14   a  and  14   b  with pinned connection provided by ball joints as will be described in greater detail subsequently. A rigid connection can also be accomplished with a beam  16   a  as shown in  FIG. 7C . With no physical connection as shown in  FIG. 7A , the lift provided by the rotors of the lift vehicle must have a lateral component as shown by vectors  30   a  and  30   b  to accommodate the lateral component of the tension T1 and T2 on cables  18   a  and  18   b  created by supporting the load from the cooperative lift vehicles  14   a  and  14   b  (thrust effects to counter weight of the vertical lift units themselves are not shown for simplicity). Interconnecting the lift vehicles  14   a  and  14   b  with a beam  16  or  16   a , as a pinned connection or rigidly, allows compressive load C1 to be carried by the beam between the lift vehicles to accommodate the lateral component of the load tension T1 and T2 (or the associated moments M1 and M2 in the rigid case) allowing the rotor lift to be directly fully vertically as represented by vectors  32   a  and  32   b  which improves lift efficiency of the cooperative system. 
     With no physical connection between the lift vehicles as shown in  FIG. 7A  (and  FIG. 1A ), all vehicles can move independent of one another in space, and have full cyclic and collective controls for tilting the rotor disk plane. Each unit is operated and controlled in its own coordinate system,  33   a ,  33   b . Pitch, roll and yaw of total cooperative system is done by coordinating each vehicle independent of one another. A virtual MVC coordinate system  36 , as described in detail subsequently, may be employed to have all vehicles fly under common control. Each vertical lift vehicle would still independently move; however, they would have target flight paths defined by the MVC coordinate system, to keep them working as a cooperative team, and to minimize variable tension on the cables between the load and the vertical lift vehicles. 
     With a semi-rigid connection, the details of vehicle interaction are shown in  FIG. 8  (and  FIG. 1B ). Lift vehicles  14   a  and  14   b  are interconnected by beam  16  with ball joints  34   a  and  34   b . Lift vehicle  14   a  and lift vehicle  14   b  have full cyclic and collective for disk tilt. All lift vehicles in the MVC can rotate freely but are linked in translation by the beam(s) which also provide compression reaction for the lateral components of load tension as previously described. All lift vehicles in the MVC use the total system coordinate system  36  for relative cooperative control in carrying the load  12 . Each vehicle behaves as part of the total system under control of the master controller. Pitch, roll and yaw of total system are done by coordinating each lift vehicle independent of other lift vehicles in the MVC. 
     Similarly with a rigid connection, the details of lift vehicle interaction are shown in  FIG. 9 . Beam  16   a  is attached to the lift vehicles  14   a  and  14   b  with rigid connectors  37   a  and  37   b  such as mating quick connect flanges or bayonet connections. Lift vehicle  14   a  and lift vehicle  14   b  have collective for thrust control. In a MVC3 or MVC4 system, the lift vehicles can optionally have cyclic, but cyclic control would not be required since pitch and roll could be accommodated with differential collective control between lift vehicles. Again, total system coordinates are used to fly the cooperative lift vehicles in the MVC and for a triplet or quadruplet configuration, thrust on each lift vehicle is used to control total system pitch, yaw, roll control. 
     For rigid or semi-rigid lift vehicle connections, lift vehicle cyclic and collective are also controlled to limit static and dynamic forces imparted on the connecting structure. As shown in  FIG. 10 , load cell  38   a  and load cell  38   b  measure forces in the beam  16  during flight operations. The force data is measured sent to the onboard flight computer  40   a  and  40   b  in each vehicle. The onboard flight control computers  40   a  and  40   b  determine the collective or cyclic control for the respective vehicle required to minimize forces in the beam  16  and send control commands to the respective vehicle control system,  42   a  and  42   b . Wireless communication link  43  between vehicles which may be a radio, WiFi or other link, shares loads and controls data to provide a feedback loop between vehicles to further minimize loads. 
     A feedback loop is established between the load cell forces and the vehicle control system to minimize connection loads as shown in  FIG. 11 . A feedback loop is established through the onboard flight computers  40   a  and  40   b  between the load cells  38   a  and  38   b  and the vehicle control systems,  42   a  and  42   b  reactive to the loads measured by the load cells to minimize connection loads on the beam  16 . A feedback loop between vehicles using the wireless communication link  43  to adjust the cooperative control algorithms further minimizes loads. 
     Individual lift vehicles in the MVC incorporate visual, LIDAR or other sensing systems in the sensor suite  29  for lift vehicle location and navigation. Positioning between lift vehicles in the MVC flying with no physical connection between vehicles may be monitored by radar or laser ranging systems or similar devices with coded returns for identification of individual lift vehicles. 
     As previously described, all lift vehicles have radio receiver and transmitters or comparable communications capability to provide the wireless communications link  43 . The sensor suites  29  on each vehicle gather data. As shown in  FIG. 12  each lift vehicle  14   a  communicates with other lift vehicle(s)  14   b  in the MVC and a base station  44  over the wireless communications link  43 . In example embodiments the based station is optimally a portable computer or hand held tablet device. The vehicles fly autonomously through a set path given by the base station. Collision avoidance is done through vehicle—to —vehicle communication when operating without physical connection. If physically connected with beams  16 , the lift vehicles minimize loads in the beam however collision avoidance algorithms are not necessary. Handling of the load  12  is accomplished through commands from the base station  44  considering all lift vehicles state data. 
     To accomplish load handling, as previously described, the sensor suite  29  in each lift vehicle has an onboard camera (or LIDAR) sensor ( 46   a ,  46   b ,  46   c ) to track the load and the other lift vehicles as represented in  FIG. 13 . Each lift vehicle  14   a  communicates with other lift vehicles  14   b ,  14   c  and the base station  44  on position of all elements. The base station  44  knows all positions through the onboard sensors and cameras and directs the MVC to position the lift vehicles over the load  12 . A reflector  47 , laser beacon or similar device may be present on the load to interface with the appropriate sensors on the lift vehicles. The load  12  is attached and detached via cables  18   a ,  18   b  and  18   c  between the lift vehicles and the load by ground personnel. Each lift vehicle is given specific position target positions by the base station for assembly into the MVC but can fly autonomously to reach those target positions. The master controller, which may be the base station  44  or an elected flight computer in the MVC minimizes forces in the cables by keeping lift vehicles close together but at a safe distance for wind gusts. The MVC is then directed to fly way points via GPS to transport and position the load  12 . 
     Lift vehicles in the MVC share data in order to compute an improved estimate of position and attitude in terms of accuracy and reliability over what would be possible with sensors on a single vehicle. (i.e., if one lift vehicle&#39;s landing spot camera view is obstructed, then data from other vehicle cameras can be used by all the vehicles). An example is shown in  FIG. 14 . 
     Vehicle  14   a  has a clear field of view  45   a  of the payload  12  and/or mission goal such as landing location with sensor  46   a . Vehicle  14   b  has a field of view  45   b  for its sensor  46   b  of payload  12  or mission goal obstructed by tree  48 . Vehicle  14   a  and vehicle  14   b  share sensor data through the wireless communication link. Vehicle  14   a  becomes the master node and directs lift vehicle  14   b  (or all lift vehicles in the MVC) to the payload or mission goal. A feedback loop is used between all lift vehicles to determine which has the best view or views, and combines for the most accurate spatial awareness. 
     In certain instances if anomalies arise with the MVC, anomalies with individual lift vehicles, load anomalies or other issues, emergency disconnect of the load may be required. As shown in  FIG. 15 , the interconnection and load support module  28  in each lift vehicle incorporates an emergency electrical disconnect (represented as elements  50   a  and  50   b  on lift vehicles  14   a  and  14   b  respectively). The emergency electrical disconnects are synchronized through the wireless communications system such that upon command, the load is simultaneously disconnected from all lift vehicles in the MVC. Normal mechanical automatic disconnects  52   a  and  52   b  provide for load connection at the individual lift vehicles  14   a  and  14   b , respectively while a load normal disconnect  54  allows attachment of the cables  18   a ,  18   b  (or slings or other interconnection systems) to the load  12 . 
     Configuration and operation of a selected MVC for carrying a desired load is shown in  FIG. 16 . A load weight and configuration is determined, step  1602 , and a number of individual lift vehicles required to provide the necessary lift is selected, step  1604 . The individual lift vehicles are assembled into a MVC, step  1606 . If the MVC is to be operated without physical connection between lift vehicles, individual lift vehicle control is implemented through each vehicle onboard flight controller to maintain lift vehicle separation using vehicle encoded mutual range sensing, step  1608 , and autonomous control of the MVC by the elected master controller is accomplished with individual collective and cyclic control of each lift vehicle by each onboard flight computer for MVC flight path control, step  1610 . If the MVC is operated with physical connection with semi-rigid beams, the beams are connected between lift vehicles of the MVC to the ball joint in the interconnection and load support module of each lift vehicle, step  1612 . Autonomous control of the MVC is accomplished by the master controller with individual collective and cyclic control of each lift vehicle by each onboard flight computer for MVC flight path control, step  1614 . If the MVC is operated with physical connection with rigid beams, the beams are connected between lift vehicles of the MVC to the rigid connection in the in the interconnection and load support module of each lift vehicle, step  1616 . 
     Connection of the air vehicles in the MVC may be automated. The user inputs payload requirement into an automated controller which may be the base station  44 . For operation with no physical connection, a selected number of lift vehicles assemble themselves to lift desired payload amount. Alternatively, on the ground the desired number of lift vehicles may be positioned by a ground handling robot. The ground handling robot positions connection beams between designated lift vehicles. A quick disconnect system on each lift vehicle engages the connection beam(s) to create the MVC. The MVC is then ready for flight commands. 
     For MVC3 and MVC4 configurations, autonomous control of the MVC is accomplished with individual collective control of each lift vehicle by each onboard flight controller responsive to the autonomous controller for pitch and roll control of the MVC for MVC flight path control, step  1618 . Force data at the beam connection is measured and the flight control computer in each lift vehicle provides flight control to minimize static and dynamic forces on the interconnecting beam(s), step  1620 . Lift vehicles in the MVC share sensor data to compute an improved estimate of position and attitude in terms of accuracy and reliability, step  1622 . Flight path guidance may be transferred to a lift vehicle having unobscured sensor field of view, step  1624 . 
     Mission objectives may then be accomplished by controlling the MVC using the autonomous controller to identify and engage a load, step  1626 . The load is then lifted and carried by the MVC under control of the autonomous controller on a predetermined flight path to a drop location, step  1628 . The load is positioned at the drop location and disconnected, step  1630 . If a functional anomaly is encountered, synchronized emergency disconnect may be accomplished, step  1632 . 
     Having now described various embodiments of the disclosure in detail as required by the patent statutes, those skilled in the art will recognize modifications and substitutions to the specific embodiments disclosed herein. Such modifications are within the scope and intent of the present disclosure as defined in the following claims.