Unmanned Aerial Vehicle UAV Research Articles

Fault-Tolerant Control of an Hexarotor Unmanned Aerial Vehicle Applying Outdoor Tests and Experiments

This paper presents a fault-tolerant control approach for actuators failures in multirotor Unmanned Aerial Vehicles UAVs. The strategy is applied on an hexarotor UAV. First, the hexarotor model is derived by means of the Newton-Euler formalism. A Controllability study based on the modified Kalman Rank condition is presented in case of one or more failing motors. A control allocation based recovery strategy is applied on the hexarotor when it is controllable. The control allocation problem is stated using a parametric programming formulation and is solved for an explicit solution. Outdoor real-time experimental results demonstrate the effectiveness of the applied strategy.

Studies of 4-rotor unmanned aerial vehicle UAV in the field of control system

The key goal of this work was to develop a functional mathematical model of a 4-rotor UAV, including regulatory apparatus and identification of its parameters. The functionality of a quadrocopter traffic control has been reduced to solving differential equations that define the motion and dynamics of an unmanned aerial vehicle. It should be noted that the synthesis of the quadrocopter control system is not an easy task, due to the non-linear nature of the dynamics of this object and its structural instability. Therefore, in this article the tested object UAV was accepted as a physical model, which may cause potential material damage resulting from damage to the device as well as other elements that are located in its immediate surroundings. In addition, the article discusses the problem of improving the quality of the estimation rate of climb of unmanned aircraft of vertical takeoff and landing UAV, this problem was considered for the object in the low-ceiling range, i.e. in the range of 0-6 m, so the issue concerns autonomous take-off and landing. For the presentation of the results, the 4-rotor UAV was used, with the use of a proportional-integral-derivative PID controller in the context of the control system. The obtained results were supported by research and analysis of real results - the discussed algorithm was implemented in the 4-rotor UAV driver.

Hierarchical land cover and vegetation classification using multispectral data acquired from an unmanned aerial vehicle

The use of multispectral cameras deployed on unmanned aerial vehicles UAVs in land cover and vegetation mapping applications continues to improve and receive increasing recognition and adoption by ...

A novel post-calibration method for digital cameras using image linear features

With the advent of new digital cameras, especially low-weight non-metric ones mounted on unmanned aerial vehicles UAVs, camera calibration models should be reinforced in accordance with their compl...

Multi-sensor based high-precision direct georeferencing of medium-altitude unmanned aerial vehicle images

A high-precision direct georeferencing method based on multi-sensor information for unmanned aerial vehicle UAV remote sensing is proposed in this research. The method makes contributions in three ...

Lightweight UAV digital elevation models and orthoimagery for environmental applications

Digital elevation models DEMs generated from unmanned aerial vehicle UAV photogrammetry offer opportunities for on-demand DEM production in environmental modelling and flood risk prediction applica...

Utility of unmanned aerial vehicles for mapping invasive plant species

This study investigates the utility of an off-the-shelf, consumer-grade unmanned aerial vehicle UAV for invasive species mapping in a lacustrine fringe environment. Specifically, this work sought t...

STUDY OF THE TURBOJET ENGINES AS PROPULSION SYSTEMS FOR THE UNMANNED AERIAL VEHICLES

The use of jet engines as propulsion systems for Unmanned Aerial Vehicles UAV's represents a actual challenge. For a large class of UAV's, providing more advantages with respect to the turboprop and turboshaft engines, as well as super-charged V12 piston engines, the small to medium size turbojet engines represent a more effective option. The research presented in this paper is focused on the thermo-dynamical analysis of a small sized turbojet. The single- spool turbojet engine model was used for the performance analysis; the one-dimensional engine cycle design was used to calculate the turbojet performances for a specified range of flight altitude and Mach number, as well as various engine operational regimes. From the numerical simulations have been expressed new parameter correlations, e.g. thrust - fuel flow, which will contribute to the deduction of a control law for the fuel flow. The objectives of the thermo- dynamical analysis have been fulfilled, with the calculated engine operating maps (i.e. variation of performances with altitude, flight Mach number and engine rotational speed), universal map of the engine; in addition, this analysis provides the values for significant engine parameters which are required by the engine's dynamic study.

An investigation of image processing techniques for substrate classification based on dominant grain size using RGB images from UAV

Imagery collected with an unmanned aerial vehicle UAV in conjunction with image processing provides new sources of environmental intelligence data and can be implemented in river habitat studies. H...

Image matching applied to autonomous navigation of unmanned aerial vehicles

This paper brings results of an image matching approach applied to the estimation of position for autonomous navigation of unmanned aerial vehicles UAVs. The main idea is to replace the global positioning system GPS signal by matching the onboard video to a georeferenced satellite image. Image processing techniques and edge descriptors are considered in order to achieve robustness to different sensors and luminosity conditions. The UAV position is then calculated by finding the pixel in the georeferenced image providing a higher spatial correlation to the image captured at flight time. The evaluation of our vision system takes into account different kinds of terrains, such as in forests, roads and urban areas and its capacity to follow real routes specified in a flight simulator. The results obtained are promising and indicate that our methodology can be used in substitution for GPS on real flights.

Controlling an unmanned quad-rotor aerial vehicle with model parameter uncertainty and actuator failure

It is challenging to stabilise an unmanned quad-rotor aerial vehicle when a dynamic change in its model parameters or failure of its actuator occurs. In this paper, a quad-rotor unmanned aerial vehicle UAV is controlled based on model reference adaptive control MRAC and a linear quadratic regulator LQR. The kinematics and dynamics of the quad-rotor are calculated, and Lyapunov's direct stability method is used to design the MRAC. In order to evaluate the performance of the adaptive control algorithms in the presence of thrust loss that may occur due to component failure or physical damage, a real quad-rotor is built from scratch using commercial components. Both controllers are designed, implemented and tested using AVR microcontrollers. Comparison is made between the controllers under normal and faulty situations and the effectiveness of the proposed control strategy is verified. Simulation and experimental results show that both controllers have satisfactory performance under normal conditions and even in the presence of the partial loss of thrust that may occur due to the loss of control effectiveness in one of the rotors or the damage of one propeller, superior system performance is observed using the proposed MRAC controller.

Vision-aided Guidance and Navigation for Close Formation Flight

Close formation flight can extend an unmanned aerial vehicle's UAV range and endurance by utilizing lift from a wingman's wake vortices and by autonomous midair refueling or recharging. The prohibitive challenge in each of these applications is the highly accurate and reliable relative positioning that is required to station-keep in the wingman's wake and to dock, amid external disturbances. Global navigation satellite systems are well-suited to reliable absolute positioning, but they fall short for accurate relative positioning. This work proposes a relative positioning solution for UAV rendezvous and close formation flight that has been verified in multiple flight tests. A nonlinear estimation framework uses precise air-to-air measurements to correct onboard sensor measurements and produce an accurate relative state estimate that is resilient to intermittent relative measurement outages and degrades gracefully during extended outages. A guidance strategy compensates for wingman turn dynamics, acts explicitly on the estimated relative state, and is applicable to both rendezvous and formation flight. Ground testing showed a relative position estimate accuracy that is 2% of the separation distance, with successful detection and correspondence at up to 36i¾?m. Autonomous close formation flight tests verified the relative positioning solution over extended periods, as close as two wingspans, in winds that were 30%-40% of the cruise airspeed, and at altitudes as low as 15i¾?m. Root-mean-square relative position errors were 1.2i¾?m horizontally and 0.44i¾?m vertically during flights at the closest separation.

Multispectral analysis of vegetation for remote sensing applications

This paper describes the development of a hardware and software tool for analysis of vegetation cover using remote sensing techniques. Begins with a study of the interaction of electromagnetic waves in the leaves of plants on the single and multiple plate models for the spectrum of visible and infrared, which allows using an application developed in Python found the spectral signature of coverage according to parameters of the leaves (known as an inversion model), which accounts for an approximation of what may occur with the reflectance of the surface of the leaves. The development of a system for acquiring and processing images in the visible and near infrared bands for use in precision agriculture through an unmanned aerial vehicle UAV is also explained.

Fuzzy Control of a Quadrotor for Reconstructed States Feedback Using Multiobserver

A type of aircraft that is currently being very reference in the area of ​​control is the quadrotor helicopter, compared to other UAV's (Unmanned Aerial Vehicles UAV's-) has been of great interest for the research groups. Principally were developed for military applications. However, UAVs don’t have only military use, also civilian use and it is in this last field that can have multiple applications. The State variables of the system obtained are, however, in the most general case, internal operation of the system variables whose values ​​can’t be measured directly on physical quantities. An observer is used for to reconstruct partially or completely the state vector of a system from the known inputs, outputs and the dynamic model of this. The reconstruction and calculation of the state variables is performed in a system known as Multiobserver. Applying the fuzzy representation of type Takagi-Sugeno, also known as multi-model [1], in dynamic model of the quadrotor and developing an algorithm based in law control for reconstructed states feedback, the vehicle is stabilized.

Coverage path planning for UAVs in unknown directional regions

This paper addresses the problem of path planning for Unmanned Aerial Vehicles UAVs in an unknown directional region. Paths are planned to maximise the amount of information from desired region whi...

A fast object detector based on high-order gradients and Gaussian process regression for UAV images

Unmanned aerial vehicles UAVs acquire images characterized by an exceptional level of detail, which calls for processing and analysis methods capable of efficiently exploiting their rich informatio...

Coverage path planning for UAVs in unknown directional regions

This paper addresses the problem of path planning for Unmanned Aerial Vehicles UAVs in an unknown directional region. Paths are planned to maximise the amount of information from desired region while accounting for the trajectory length. In this paper, an exploration system is proposed for specific cases with shifting directions such as rivers and lakes. Taking account of data synchronisation errors, this method maximises the amount of information value and optimises the path length. Desired region is divided into grids based on required image resolution as well as time needed during the process. Analyses show that the real area and path length are closely related to the yaw angle of UAVs. The path planning issue is studied as an optimisation problem and has been solved by a modified depth-first search method. Monte-Carlo simulations are carried out to validate the effectiveness of the proposed algorithm, in which the UAV performs a task to track targets on a flowing river.

The Earthquake Damage Remote Sensing Automatic Recgnition Based on Texture of Roof Tiles

To meet the technical demands of rapid assessment on small and medium earthquake damages, this paper presents the comprehensive disaster evaluation method of on-spot human-computer interaction survey and remote sensing image analysis based on the GIS technology support in the small and medium earthquakes. By making full use of the advantages of existing data, emphasizing on the automatical identification of the unique texture features of small earthquakes with a combination analysis on high resolution images gained from unmanned aerial vehicles (uav) and the seismic damages, the new method results in the rank distribution of earthquakes by gaining the experienced parameter of local small-medium earthquakes based on the analysis of regional characteristics of texture features of remote sensing images. It is concluded that the evaluation method is more accurate and efficient for small and medium earthquake rapid disaster assessment.

Discuss of Unmanned Plane Braking Experiment Base on Eddy Current Technology

In the process of unmanned aerial vehicle (uav) landing safely and quickly brake problem，Puts forward a uav electric eddy current braking method.The method through the eddy current and magnetic field interact to produce braking torque. According to the uav braking requirements, Design the uav electric eddy current brake simulation system. Test results show that: Based on the eddy current brake technology the average braking torque for 870N·m is greater than the “inner” type uav brake the average braking torque for 530N·m, Can meet the requirements of the uav braking system, So will the eddy current brake applied to unmanned aerial vehicle is feasible.

Optimal Search and Detection of Clustered Hidden Targets under Imperfect Inspections

We formulate and solve a discrete-time search-optimization problem where a single searcher or several searchers (for example, unmanned aerial vehicles UAVs or robots) operate and move in a discretized 3-dimensional airspace, looking for static or moving targets in a finite set of locations. Prior probabilities of target location are known for each target, and each searcher (UAV) has to sequentially inspect the locations. The inspections are imperfect: a probability of overlooking the target (that is, a false-negative outcome) and a probability of a “false alarm” (that is, a false-positive outcome) exist. The objective is to find the targets as effectively as possible within a given level of confidence. Common measure of effectiveness for the search/detection process are: the expected time of the search; the expected cost of the search; the expected losses; and the expected averted risk. An effective index-based search algorithm is developed. An example for an automatic device (UAV or robot) searching for a target moving along a highway is discussed.