Abstract:
A method for path planning for a plurality of vehicles in a mission space includes determining, with a processor, information indicative of a first local graph of a first vehicle; receiving, with the processor over a communication link, information indicative of a second local graph from a second vehicle; assembling, with the processor, information indicative of a global graph in response to the receiving of the second local graph; wherein the global graph includes information assembled from the first local graph and the second local graph; and wherein the global graph indicates connectivity of objectives for each vehicle of the plurality of vehicles in the mission space.

Description:
BACKGROUND 
       [0001]    The subject matter disclosed herein relates generally to the field of vehicle management systems and to a method and system for coordinated mission planning and graph sharing between independent agents over a communication network. 
       DESCRIPTION OF RELATED ART 
       [0002]    Multiple homogeneous (similar vehicles) or heterogeneous (different types of vehicles) independent agents may coordinate to effectively navigate a new environment or accomplish a common task in support of mission goals. These independent agents may cooperate through information sharing over a common network through a “common operating picture.” However, coordinated planning applications in unmanned autonomous vehicles (“UAV&#39;s”) present new challenges. For example, the nature of the environment can cause UAV&#39;s to become impeded by unknown obstacles or situations as they go about the execution of tasks and mission plans may be compromised on account of these obstacles. A coordinated planning method between autonomous and semi-autonomous independent agents is desired. 
       BRIEF SUMMARY 
       [0003]    According to an aspect of the invention, a method for path planning for a plurality of vehicles in a mission space includes determining, with a processor, information indicative of a first local graph of a first vehicle; receiving, with the processor over a communication link, information indicative of a second local graph from a second vehicle; assembling, with the processor, information indicative of a global graph in response to the receiving of the second local graph; wherein the global graph includes information assembled from the first local graph and the second local graph; and wherein the global graph indicates connectivity of objectives for each vehicle of the plurality of vehicles in the mission space. 
         [0004]    In addition to one or more of the features described above, or as an alternative, further embodiments could include determining of the information of the first local graph comprises receiving sensor information indicative of obstacles and constraints in the mission space. 
         [0005]    In addition to one or more of the features described above, or as an alternative, further embodiments could include comprising determining nodes and edges for each of the first and second local graph. 
         [0006]    In addition to one or more of the features described above, or as an alternative, further embodiments could include receiving the first local graph by the second vehicle and assembling the global graph in the second vehicle in response to the receiving of the first local graph. 
         [0007]    In addition to one or more of the features described above, or as an alternative, further embodiments could include receiving the first and second local graphs through direct communication links between the first and second vehicle over a communication network. 
         [0008]    In addition to one or more of the features described above, or as an alternative, further embodiments could include receiving the first and second local graphs through an indirect communication link connected to a communication beacon over a communication network. 
         [0009]    In addition to one or more of the features described above, or as an alternative, further embodiments could include re-planning the global graph as re-planned first and second local graphs are received by the first and second vehicles. 
         [0010]    In addition to one or more of the features described above, or as an alternative, further embodiments could include establishing direct communication links between the first vehicle and other vehicles as objectives in the global graph are accomplished. 
         [0011]    According to another aspect of the invention, a system for path planning for a plurality of vehicles in a mission space includes a communication network; a processor; and memory having instructions stored thereon that, when executed by the processor, cause the system to: determine information indicative of a first local graph of a first vehicle; receive information indicative of a second local graph from a second vehicle; assemble information indicative of a global graph for the mission space in response to the receiving of the second local graph; wherein the global graph includes information from the first local graph and the second local graph; and wherein the global graph indicates connectivity of objectives for each vehicle of the plurality of vehicles in the mission space. 
         [0012]    In addition to one or more of the features described above, or as an alternative, further embodiments could include the processor configured to receive sensor information indicative of obstacles and constraints in the mission space. 
         [0013]    In addition to one or more of the features described above, or as an alternative, further embodiments could include the processor configured to determine nodes and edges for each of the first and second local graph. 
         [0014]    In addition to one or more of the features described above, or as an alternative, further embodiments could include the processor configured to receive the first local graph by the second vehicle and assemble the global graph in the second vehicle in response to the receiving of the first local graph. 
         [0015]    In addition to one or more of the features described above, or as an alternative, further embodiments could include the processor configured to receive the first and second local graphs through direct communication links between the first and second vehicle over the communication network. 
         [0016]    In addition to one or more of the features described above, or as an alternative, further embodiments could include the processor configured to receive the first and second local graphs through an indirect communication link connected to a communication beacon over the communication network. 
         [0017]    In addition to one or more of the features described above, or as an alternative, further embodiments could include the processor configured to re-planning the global graph as re-planned first and second local graphs are received by the first and second vehicles. 
         [0018]    Technical functions of the combination of features include providing for mission success and improved mission feasibility through collaboration of plans between agents with a path planning method. 
         [0019]    Other aspects, features, and techniques of the invention will become more apparent from the following description taken in conjunction with the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0020]    The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which like elements are numbered alike in the several FIGURES: 
           [0021]      FIG. 1  is a schematic view of an example independent agent according to an embodiment of the invention; 
           [0022]      FIG. 2  is a schematic view of an example computing system according to an embodiment of the invention; 
           [0023]      FIG. 3  is a schematic view of a network topology according to an embodiment of the invention; and 
           [0024]      FIG. 4  is a schematic view of a graph topology according to an embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0025]    Referring now to the drawings,  FIG. 1  illustrates a general perspective view of an exemplary independent agent or vehicle equipped for operation in accordance with embodiments of the invention. The exemplary independent agent (hereinafter “agent”) is in the form of a vertical takeoff and landing (VTOL) autonomous or semi-autonomous rotary-wing aircraft or helicopter  100  that implements a motion planning algorithm  204  for implementing a sampling-based planning method for coordinated mission planning between a plural or multiple number of independent agents that are substantially similar to independent agent  100 . The sampling based-planning method is described below with reference to  FIGS. 3-4 . For purposes of describing the invention, the term “independent agent” is intended to refer to any heterogeneous vehicle such as, for example, VTOL autonomous aircraft  100  that cooperates with one or more other independent agents to undertake tasks, objectives, and/or navigate within a mission space in support of a mission. 
         [0026]    Rotary-wing aircraft  100  includes an airframe  102  having a main rotor assembly  104  and an extending tail  106  which mounts an anti-torque system, such as a tail rotor assembly  108 . Main rotor assembly  104  includes a plurality of substantially similar rotor blades  112  while tail rotor assembly  108  includes a plurality of substantially similar blades  114 . Also, aircraft  100  can include a sensor system  212  ( FIG. 2 ). Sensor system  212  can include sensors associated with one or more devices for receiving state information or navigation data for aircraft  100 . Although a particular vehicle in the form of a rotary-wing aircraft  100  is illustrated and described in the disclosed embodiments, it will be appreciated that other configurations and/or machines include autonomous and optionally piloted vehicles that may operate in land or water including fixed-wing aircraft, rotary-wing aircraft, marine vessels (e.g., submarines, ships, etc.), and land vehicles (e.g., trucks, cars, etc.) may also benefit from embodiments disclosed. As such, embodiments of the disclosed invention are not restricted to application in aircraft, but are applicable wherever coordinated motion planning between cooperative agents is desired. 
         [0027]      FIG. 2  illustrates a schematic block diagram of a control system  200  for implementing coordinated motion planning in order to accomplish mission goals according to an exemplary embodiment. As illustrated, control system  200  implements a motion planning algorithm  204  for coordinated planning between cooperative agents, e.g., substantially similar to aircraft  100 , in order to build a common operating picture though a communication network. Control system  200  includes a computing system such as an aircraft computer  202  having one or more processors and memory to process sensor data acquired from sensor system  212 . Aircraft computer  202  can be provided on each cooperative agent. Aircraft computer  202  includes a memory  208 . Memory  208  stores motion planning algorithm  204  as executable instructions that is executed by processor  206 . The instructions may be stored or organized in any manner and at any level of abstraction, such as in connection with the execution of motion planning algorithm  204 . Processor  206  may be any type of processor, central processing unit (“CPU”) or graphics processing unit (“GPU”), including a general purpose processor, a digital signal processor, a microcontroller, an application specific integrated circuit (“ASIC”), a field programmable gate array (“FPGA”), or the like. In embodiments, memory  208  may include random access memory (“RAM”), read only memory (“ROM”), or other electronic, optical, magnetic or any other computer readable medium onto which is stored motion planning algorithm  204  described below with reference to  FIGS. 3-4 . 
         [0028]    Sensor system  212  includes sensors associated with one or more data acquisition devices for sensing state information or position information for aircraft  100 . In embodiments, sensor system  212  can include one or more navigation systems such as, for example, a Global Positioning System (“GPS”), an Inertial Measurement unit (“IMU”), or other inertial measurement system such as air data sensors or radio navigation systems that can be used to acquire positional data related to a current location and acceleration of aircraft  100  and can be used to determine a geographic location of aircraft  100  including a change from an initial position of aircraft  100 , and sensors associated with a vision system such as cameras, LIght Detection and Ranging scanner (LIDAR), LAser Detection and Ranging scanner (LADAR). Communication system  210  can include radio communications such as air data scanner, instrument landing system (ILS), and radio navigation, or the like. 
         [0029]      FIG. 3  illustrates a schematic view depicting a network topology  300  for information sharing between agents over a communication network according to an embodiment of the invention. Network topology  300  includes agents  302 - 308  that communicate their respective local graphs over a communication network comprising communication links  312 - 316  in order to build a common or global graph for accomplishing mission goals. Each local graph comprises motion-based graph data objects having nodes and edges, as is described below. The network topology  300  may be dynamic, i.e., different connections may be made between agents  302 - 308  as objectives are accomplished by agents  302 - 308  or new obstacles require re-planning of the local- and global graphs. 
         [0030]    As shown in  FIG. 3 , agents can have a direct communication link with other agents in the communication network through which local graph data from each independent is transmitted to agent. However, one or more agents may not have direct communication links with other agents such as, for example, agent  302  does not have a direct communication link with agent  304 . In this case, communication of information may be facilitated through other agents that are connected in the communication network, for example, from agent  302  to agents  308 ,  306 , and  304 . In addition to the network connections depicted above, or alternatively, an optional communication beacon  310  (e.g., ground control station, airborne control station, airborne early warning control system, or the like) may facilitate network communication of information between agents  302 - 308  through communication links  318 - 324  in order to extend the range of communication network and/or facilitate communications between agents that are not directly connected through a communication link. In embodiments, each communication link  312 - 324  comprises communication system  210  ( FIG. 2 ) that connects aircraft computer  202  ( FIG. 2 ) by wire, cable, fiber optic, and/or wireless links facilitated by various types of well-known network elements, such as hubs, switches, and the like. Communication links  312 - 324  may employ various well-known protocols to transmit and receive information among independent agents  302 - 308  and/or communication beacon  310 . For example, protocols can include wifi, wireless communications, e.g., long-term evolution (“LTE”), worldwide Interoperability for microwave access (“WiMAX”), general packet radio service (“GPRS”), or the like. 
         [0031]      FIG. 4  illustrates a schematic view of a graph topology  400  for information sharing between agents based on a sampling-based planning method in a mission space that is performed by motion planning algorithm  204  ( FIG. 2 ) according to an embodiment of the invention. Graph topology  400  depicts coordinated mission planning with local graph sharing between agents  302 - 308  in order to share a common operating picture of a mission space. The common operating picture is provided through a global graph where multiple agents coordinate to accomplish a set of tasks in the mission space. 
         [0032]    As shown in  FIG. 4 , global graph  401  includes nodes and edges that are created from local graphs of agents  302 - 308 . The global graph  401  can be assembled from local graphs of each agent  302 - 308  as they are received. In one example, agent  306  creates a local graph  401  that includes nodes  401   a - 401   c  and edges  401   d - 401   f.  Local graph  402  is shown decoupled from the global graph  401 . Also, agent  304  is shown adding itself to respective local graphs received from agents  302 ,  304  to assemble global graph  401 ; agent  302  has created graph  403  from respective local graphs received from agents  304 ,  308 ; and agent  304  is shown adding itself to respective local graphs received from agents  302 ,  308 . The global graph  401  is created with new information from the local graphs received by each agents  302 - 308  in order to create a common reachable roadmap of a mission space taking into account sensed obstacles  416 - 422 , global mission planning data such as constraints, or the like for each independent agent  302 - 308 . The global graph  401  designates the connectivity of a mission space for each agent  302 - 308  and the locations it can reach without conflicting with plans or objectives of other agents. 
         [0033]    Each agent  302 - 308  has a sensor system  212  ( FIG. 2 ) that can perceive local threats or obstacles within its environment. In addition, each agent  302 - 308  can store information related to mission planning constraints such as, e.g., no-fly zone areas, obstacles, or threats in a mission space, in order to construct a local graph based on threats and constraints in the environment. Each agent  302 - 308  creates a local graph including graph data objects comprising nodes and edges. The sampling-based planning method includes each agent  302 - 308  generating a local graph. Each agent  302 - 308  creates a local graph by placing various nodes throughout a roadmap in a mission space and joins these nodes using edges (i.e., path segments) to create a local graph. In the example shown in  FIG. 4 , nodes  404  and  406  are connected by edge  408  and nodes  410  and  412  are connected by edge  414 . Each agent updates its local graph by assembling it with the local graphs received from other agents  302 - 306  in order to build a copy of a global graph at a “swarm” level. Agents  302 - 308 , representing a swarm of agents, exchange information representing their respective local graphs having graph data objects over a communication network ( FIG. 3 ) that connects the agents  302 - 308 . The method of sharing local graphs and assembling these into a global graph is repeated as required for completing the underlying mission. Each agent  302 - 308 , through the global graph  401 , can determine the activities of other agents and can plan accordingly by avoiding the other agents, for example, in multi-vehicle collision avoidance applications, in convoy-type applications, or in rendezvous applications. 
         [0034]    In multi-vehicle type applications, different vehicles share a common graph to deconflict motion plans. As a global graph, for example, global graph  401 , provides a way to construct a common picture of reachability for each vehicles gent, it can provide means to compute rapid alternatives when plans conflict. 
         [0035]    In rendezvous applications, two or more vehicles can plan to meet at a particular location. A tree-like graph object, which is a specific instance of a graph based data object, can be used where two vehicles build their local tree refinements and build consensus over the communication network by updating each other&#39;s tree information. For example, in a medical evacuation mission—where a soldier or an unmanned ground vehicle (“UGV”) on the ground is meeting up with a helicopter to evacuate a casualty. The soldier or UGV&#39;s possible locations of reachability could be computed concurrently and shared with the helicopter and vice-versa. When a consensus is reached—the helicopter is able to reach a position that is also reachable by the UGV or the soldier. 
         [0036]    In convoy-type applications where a convoy of autonomous vehicles is travelling to a common destination or a set of close destinations, the leading autonomous vehicle can provide the reachability information to trailing vehicle through its graph, and therefore, conduct mission plans in a convoy more effectively. 
         [0037]    Benefits of the embodiments of the invention discussed herein provide for collaboration of plans between independent agents through a path planning method so that mission success and feasibility can be improved. The path planning method allows each agent to search the same graph for alternatives in order to avoid conflicts and complete objectives in a mission space. 
         [0038]    The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. While the description of the present invention has been presented for purposes of illustration and description, it is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications, variations, alterations, substitutions or equivalent arrangement not hereto described will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the invention. Additionally, while the various embodiments of the invention have been described in relation to an autonomous aircraft, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.