Optimal rendezvous trajectory for unmanned aerial-ground vehicles

Fixed-wing unmanned aerial vehicles (UAVs) can be an essential tool for low cost aerial surveillance and mapping applications in remote regions. There is however a key limitation, which is the fact that low cost UAVs have limited fuel capacity and hence require periodic refueling to accomplish a mission. Moreover, the usual mechanism of commanding the UAV to return to a stationary base station for refueling can result in fuel wastage and inefficient mission operation time. Alternatively, one strategy could be the use of an unmanned ground vehicle (UGV) as a mobile refueling unit, where the UAV will rendezvous with the UGV for refueling. In order to accurately perform this task in the presence of wind disturbances, we need to determine an optimal trajectory in 3D taking UAV and UGV dynamics and kinematics into account. In this paper, we propose an optimal control formulation to generate a tunable UAV trajectory for rendezvous on a moving UGV that also addresses the possibility of the presence of wind disturbances. By a suitable choice of the value of an aggressiveness index that we introduce in our problem setting, we are able to control the UAV rendezvous behavior. Several numerical results are presented to illustrate the reliability and effectiveness of our approach

Fault-tolerant formation driving mechanism designed for heterogeneous MAVs-UGVs groups

A fault-tolerant method for stabilization and navigation of 3D heterogeneous formations is proposed in this paper. The presented Model Predictive Control (MPC) based approach enables to deploy compact formations of closely cooperating autonomous aerial and ground robots in surveillance scenarios without the necessity of a precise external localization. Instead, the proposed method relies on a top-view visual relative localization provided by the micro aerial vehicles flying above the ground robots and on a simple yet stable visual based navigation using images from an onboard monocular camera. The MPC based schema together with a fault detection and recovery mechanism provide a robust solution applicable in complex environments with static and dynamic obstacles. The core of the proposed leader-follower based formation driving method consists in a representation of the entire 3D formation as a convex hull projected along a desired path that has to be followed by the group. Such an approach provides non-collision solution and respects requirements of the direct visibility between the team members. The uninterrupted visibility is crucial for the employed top-view localization and therefore for the stabilization of the group. The proposed formation driving method and the fault recovery mechanisms are verified by simulations and hardware experiments presented in the paper

A convoy protection strategy using the moving path following method

This paper considers the problem of convoy protection missions using a fixed-wing Unmanned Aerial Vehicle (UAV) in scenarios where the radius of the circular region of interest around the convoy is smaller than the UAV minimum turning radius. Using the Moving Path Following (MPF) method, we propose a guidance algorithmic strategy where a UAV moving at constant ground speed is required to converge to and follow a desired geometric moving path that is attached to the convoy center. Conditions under which the proposed strategy solves the convoy problem are derived. A performance metric that is proposed together with numerical simulation results demonstrate the effectiveness of the proposed approach.info:eu-repo/semantics/acceptedVersio

Optimal algorithm design for transfer path planning for unmanned aerial vehicles

Over the past three decades unmanned aerial vehicles (UAV) have seen significant development with a current focus on automation. The main area of development that is pushing automation is that of path planning allowing a UAV to generate its own path information that it can then follow to carry out its mission. Little work however has been carried out on transfer path planning. This work attempts to address this shortcoming by developing optimal algorithms for a path planning task to move on to a circular flightpath to carry out a target tracking mission. The work is developed in three main sections. Firstly the transfer algorithm itself is derived including gradient analysis for the cost function being applied, adaptation of this cost function into two separate minimising actions and analysis of a cost function issue that introduces a separation distance constraint. The algorithm is tested proving correct constraint activation and cost selection. The second part of this work looks at validating the results of the transfer algorithm against the Dubin's car result and a receding horizon approach when applied to the transfer operation. Utilising the cost results from the transfer algorithm an efficiency analysis against the equivalent costs from the other methods is carried out. Lastly this work looks at the comparison between the developed transfer algorithm and a more flexible transfer approach by developing a new cost function form. A switching cost function is introduced where environmental parameters from the target tracking mission (i.e target position and velocity) are used to switch between a number of applicable cost functions (time minimal, distance minimal and minimum speed transfer). An analysis is carried out to investigate the performance of both the original algorithm and the newly developed switching function based on key target tracking parameter

Guaranteed Road Network Search with Small Unmanned Aircraft

The use of teams of small unmanned aircraft in real-world rapid-response missions is fast becoming a reality. One such application is search and detection of an evader in urban areas. This paper draws on results in graph-based pursuit-evasion, developing mappings from these abstractions to primitive motions that may be performed by aircraft, to produce search strategies providing guaranteed capture of road-bound targets. The first such strategy is applicable to evaders of arbitrary speed and agility, offering a conservative solution that is insensitive to motion constraints pursuers may possess. This is built upon to generate two strategies for capture of targets having a known speed bound that require searcher teams of much smaller size. The efficacy of these algorithms is demonstrated by evaluation in extensive simulation using realistic vehicle models across a spectrum of environment classes