UAV Group Autonomy In Network Centric Environment

Abstract

It is a well-recognized fact that unmanned aerial vehicles are considered an essential element in today’s network-centric integrated battlefield environment. Compared to solo UAV missions, deploying multiple unmanned aerial vehicles in cooperative mode offers many advantages and it motivates UAV researchers all over the world to evolve concepts of operations that aim to achieve a paradigm shift in information collection, from traditional “dull” missions to performing “dirty” and “dangerous” missions. In the past, mission success depended on continuous interaction of a ground pilot with a single UAV, but in the future it would depend only on interaction among UAV groups with no interaction with any ground entity. To reach this capability level, it is necessary for researchers to first understand the various levels of autonomy and the crucial role that information and communication play in making these autonomy levels possible. The first part of this research thesis is focused on “Development of an organized framework to realize the goal of achieving fully autonomous systems.” An in-depth analysis of the UAV solo and group autonomous control levels has been done and autonomous mission control has been defined through eleven levels to complete the autonomy hierarchy. Each autonomous level has several sublevels to be achieved and these are described in detail for better appreciation and clarity. The role of communication and information in each level has been highlighted with respect to mission scenario. This first-of-its-kind research work helps in classifying the existing problems and solutions for each level and also presents various research opportunities available at each level. Based on the literature review on autonomous mission control level and gap analysis, group autonomy is selected as the major area for this research thesis. In group autonomy, group coordination is the first level to be achieved and it involves grouping of UAVs, identifying, prioritizing and allocating tasks to team members and demonstration of basic coordination procedures. A ground attack mission by a group of UAVs is one of the most important and practical applications in the military context in which group autonomy and coordination tactics play a crucial role in determining the success of the mission. The second part of this research thesis is focused on “Design of UAV grouping algorithm and coordination tactics for ground attack missions.” In this part of the research work, we present a novel method for the UAV grouping problem based on Dubins’ path to determine the number of UAVs required to engage at different attack angles in a ground attack mission. Procedures to create a generic battlefield scenario, intra and inter-group mission tactics, its demonstration through simulation using Group Flyer software, performance metrics and mission success index definition and performance evaluation for various off-nominal conditions are presented. Precise navigation information of each UAV plays a crucial role in the success of a cooperative mission. Though present-day UAVs are equipped with GPS, the UAVs have to rely on navigation information obtained from inertial navigation systems in GPS-denied environments. The third part of this research thesis is focused on “Group coordination and path replan tactics in GPS-denied environments.” This part of the research work addresses the problem of establishing a GPS-protected wireless MAV network (WIMAN) using three classes of navigation systems: one equipped only with GPS, another equipped only with high-accuracy inertial navigation systems, and another equipped with relatively low-accuracy inertial navigation systems. A distributed cooperative localization computes the true position of each MAV as a convex linear combination of the barycentric coordinates of the MAV with respect to their neighbors, which are determined from the Cayley–Menger determinants. NP-hardness in establishing GPS-protected WIMAN architecture is discussed and a heuristic algorithm is proposed. The effect of INS error and communication distortions on WIMAN performance, improvement based on localization algorithm and selection of update time for trajectory correction is discussed. Group coordination and tactical replan procedures that enable WIMAN to maintain its configuration. uration, reconfiguration to adapt to various phases of cooperative threat reconnaissance mission, is demonstrated through simulation results. Since the last few years, UAV researchers all over the world are evolving concepts of operations that aim to achieve a paradigm shift in information collection, from mere reconnaissance to persistent Intelligence Surveillance and Reconnaissance (ISR) missions. Instead of detecting a relatively isolated movement in an area of interest, the problem shifts to detecting an activity that is interconnected with other activities within the same space-time volume. Using persistent ISR, an area of interest can be monitored continuously, maintaining constant and enduring contact with the targets of interest. This increasing understanding about the target enables a faster decision cycle at all levels of command and supports the application of precision strike to achieve the desired effects on the area of interest. Though persistent ISR plays a major role in the battlefield, it plays an equally promising role in a wide-area urban environment, particularly in applications related to counter-terrorism and counter-insurgent activities. The fourth part of this research thesis is focused on establishing a layered persistent intelligence, surveillance and reconnaissance network to demonstrate “UAV group tactical path and goal replan for persistent ISR mission in GPS-denied wide-area urban environment.” A three-layer UAV surveillance network operating at three different altitudes, with each group in each layer consisting of three different classes of navigation systems—one equipped only with GPS, another equipped only with high-accuracy inertial navigation system (INS), and another equipped with relatively low-accuracy INS-is designed. An algorithm to generate the layered surveillance network and persistent surveillance trajectories is discussed. An algorithm for group tactical path replan in the event of UAV failures and enroute obstacles, and group tactical goal replan to exploit enroute surprise targets, is presented. The algorithm performances are demonstrated through simulation on a representative GPS-denied wide-area urban environment. In summary, this research thesis represents many first steps taken in the study of autonomous UAV systems and, in particular, group autonomy. An organized framework for autonomous mission control level by defining various sublevels, classifying the existing solutions and highlighting the various research opportunities available at each level is discussed. Significant contributions to group autonomy research, by providing first-of-its-kind solutions for UAV grouping based on Dubins’ path, establishing a GPS-protected wireless network capable of operating in GPS-denied environments, and demonstration of group tactical path and goal replan in a layered persistent ISR mission, are presented. Algorithms discussed in this thesis are generic in nature and can be applied to higher autonomous mission control levels, involving strategic decisions among UAVs, unmanned ground vehicles, unmanned underwater vehicles, and satellites in a network-centric environment.