Unmanned Air Research Articles

Рассредоточенный нагрев гелия в беспилотном дирижабле сельскохозяйственного назначения

In modern agricultural production, unmanned aerial vehicles are capable of solving many tasks. It is expedient to use airships to perform long technological operations above the ground. To justify the need for the dispersed heating of helium in the working chamber of the airship, the authors considered the influence of the ratio of the volumes occupied by heated and cold helium in the working chamber of the airship, as well as the influence of the helium temperature on the lifting force. Calculations have shown that the dispersed heating of helium causes an accelerated change in its density, provides a reduction in the energy consumption for heating, and reduces the requirements for the thermal strength of the envelope. It is shown that distributed heating of helium in the whole working chamber of the airship has a number of advantages over local heating. In the proposed design of the unmanned airship, the technical implementation of the distributed heating of helium is achieved by means of an electrical heating device, the conductive elements of which are placed throughout the working chamber on supports made of light dielectric material. To increase the heating efficiency, the inner surface of the envelope is covered with a reflector made of thin basalt wool foil. The vertical maneuvering of the airship is automatically maintained by the control unit by connecting an electric heating device depending on the helium temperature and the ambient temperature.

Autonomous Flight in Hover and Near-Hover for Thrust-Controlled Unmanned Airships

The ability of airships to fly in hover is a major plus of this category of flying vehicles. However, especially for the case of autonomous flight, this feature can be exploited only recurring to a carefully designed layout of the thrusters on board. Furthermore, the thrusters need to be suitably governed by a dedicated control algorithm. This paper explores a scheme for the control in hover of a thrust-controlled airship without thrust vector control, also assessing its effectiveness in near-hover positioning problems. The control scheme proposed herein extends the capability of a stability augmentation and guidance controller for forward flight, previously introduced by the authors for a conceptually similar airship. A control action based on a system of thrust forces required for hover, and additional thrust components for stabilizing and steering the airship in slow (near-hover) navigation, is thoroughly described. The ensuing control suite is applied and tested in the present paper on the high-fidelity virtual model of a five-thruster airship, showing reasonable stability levels and navigation accuracy of the controlled system.

Viewpoint-Driven Formation Control of Airships for Cooperative Target Tracking

For tracking and motion capture (MoCap) of animals in their natural habitat, a formation of safe and silent aerial platforms, such as airships with on-board cameras, is well suited. In our prior work we derived formation properties for optimal MoCap, which include maintaining constant angular separation between observers w.r.t. the subject, threshold distance to it and keeping it centered in the camera view. Unlike multi-rotors, airships have non-holonomic constrains and are affected by ambient wind. Their orientation and flight direction are also tightly coupled. Therefore a control scheme for multicopters that assumes independence of motion direction and orientation is not applicable. In this paper, we address this problem by first exploiting a periodic relationship between the airspeed of an airship and its distance to the subject. We use it to derive analytical and numeric solutions that satisfy the formation properties for optimal MoCap. Based on this, we develop an MPC-based formation controller. We perform theoretical analysis of our solution, boundary conditions of its applicability, extensive simulation experiments and a real world demonstration of our control method with an unmanned airship. Open source code <uri xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">https://tinyurl.com/AsMPCCode</uri> and a video of our method is provided at <uri xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">https://tinyurl.com/AsMPCVid</uri>

Enhanced Recurrent Fuzzy Neural Fault-Tolerant Synchronization Tracking Control of Multiple Unmanned Airships via Fractional Calculus and Fixed-Time Prescribed Performance Function

This article proposes a fractional-order intelligent fault-tolerant synchronization tracking control (FO-I-FTSTC) scheme for multiple unmanned airships (UAs) against actuator faults. Within the developed control architecture, fixed-time prescribed performance functions (PPFs) are first designed to transform the synchronization tracking errors into a new set of error variables, such that the original errors are strictly confined within the prescribed bounds. Then, fractional calculus and sliding mode surface are sequentially introduced to construct the FO errors. Moreover, to handle the unknown terms and bias faults in the FO sliding-mode error dynamics, fuzzy neural networks with recurrent loops are artfully constructed to act as the intelligent learning units. Furthermore, the norm of the loss-of-effectiveness fault factors is introduced for each UA to reduce the number of adaptive parameters. The distinct feature of the proposed method is that the FO-I-FTSTC performance is significantly enhanced by integrating recurrent fuzzy neural networks, fractional calculus, and fixed-time PPFs into a unified framework, leading to a high-precision control scheme. It is shown by Lyapunov analysis that all UAs can track their desired references in a synchronized manner, and the synchronization tracking errors are bounded and strictly confined within the prescribed error bounds. Comparative hardware-in-the-loop experiments are presented to show the effectiveness of the proposed FO-I-FTSTC scheme.

Distributed Fractional-Order Intelligent Adaptive Fault-Tolerant Formation-Containment Control of Two-Layer Networked Unmanned Airships for Safe Observation of a Smart City.

This article investigates a distributed fractional-order fault-tolerant formation-containment control (FOFTFCC) scheme for networked unmanned airships (UAs) to achieve safe observation of a smart city. In the proposed control method, an interval type-2 fuzzy neural network (IT2FNN) is first developed for each UA to approximate the unknown term associated with the loss-of-effectiveness faults in the distributed error dynamics, and then a disturbance observer (DO) is proposed to compensate for the approximation error and bias fault encountered by each UA, such that the composite learning strategy composed of the IT2FNN and the DO is obtained for each UA. Moreover, fractional-order (FO) calculus is incorporated into the control scheme to provide an extra degree of freedom for the parameter adjustments. The salient feature of the proposed control scheme is that the composite learning algorithm and FO calculus are integrated to achieve a satisfactory fault-tolerant formation-containment control performance even when a portion of leader/follower UAs is subjected to the actuator faults in a distributed communication network. Furthermore, it is shown by Lyapunov stability analysis that all leader UAs can track the virtual leader UA with time-varying offset vectors, and all follower UAs can converge into the convex hull spanned by the leader UAs. Finally, comparative hardware-in-the-loop (HIL) experimental results are presented to show the effectiveness and superiority of the proposed method.

A GA and SVM Classification Model for Pine Wilt Disease Detection Using UAV-Based Hyperspectral Imagery

Pine wilt disease (PWD), caused by the pine wood nematode (Bursaphelenchus xylophilus), is a global destructive threat to forests and has led to serious economic losses all over the world. Therefore, it is necessary to establish a feasible and effective method to accurately monitor and estimate PWD infection. In this study, we used hyperspectral imagery (HI) collected by an unmanned airship with a hyperspectral imaging spectrometer to detect PWD in healthy, early, middle and serious infection stages. To avoid massive calculations on the full spectral dimensions of the HI, 16 spectral features were extracted from the HI, and a genetic algorithm (GA) was implemented to identify the optimal ones with the least fitness. Simultaneously, a support vector machine (SVM) classifier was established to predict the PWD infection stage for an individual pine tree. The following results were obtained: (1) the spectral characteristics for pine trees in different PWD infection stages were distinctive in the green region (510–580 nm), red edge (680–760 nm) and near-infrared (780–1000 nm) spectra; (2) the six optimal spectral features (Dgreen, SDgreen, Dred, DRE, DNIR, SDNIR) selected with the GA effectively distinguished the PWD infection stages of pine trees with a lower calculation cost; (3) compared with the traditional classifiers, such as k-nearest neighbor (KNN), random forest (RF) and single SVM, the proposed GA and SVM classifier achieved the highest overall accuracy (95.24%) and Kappa coefficient (0.9234). The approach could also be employed for monitoring and detecting other forest pests.

Distributed Adaptive Fault-Tolerant Time-Varying Formation Control of Unmanned Airships With Limited Communication Ranges Against Input Saturation for Smart City Observation.

This article investigates the distributed fault-tolerant time-varying formation control problem for multiple unmanned airships (UAs) against limited communication ranges and input saturation to achieve the safe observation of a smart city. To address the strongly nonlinear functions caused by the time-varying formation flight with limited communication ranges and bias faults, intelligent adaptive learning mechanisms are proposed by incorporating fuzzy neural networks. Moreover, Nussbaum functions are introduced to handle the input saturation and loss-of-effectiveness faults. The distinct features of the proposed control scheme are that time-varying formation flight, actuator faults including bias and loss-of-effectiveness faults, limited communication ranges, and input saturation are simultaneously considered. It is proven by Lyapunov stability analysis that all UAs can achieve a safe formation flight for the smart city observation even in the presence of actuator faults. Hardware-in-the-loop experiments with open-source Pixhawk autopilots are conducted to show the effectiveness of the proposed control scheme.

Fractional-Order Sliding-Mode Fault-Tolerant Control of Unmanned Airship Against Actuator Faults

This paper proposes a fractional-order sliding-mode fault-tolerant control scheme for unmanned airship in the presence of actuator faults. In the control scheme, a control-oriented unmanned airship model is first developed by considering the unexpected actuator faults. Then, fractional-order calculus and sliding-mode control strategies are integrated to achieve refined fault-tolerant performance. Fixed-time sliding-mode disturbance observer is employed to estimate the fault-induced uncertainty. Moreover, Lyapunov stability analysis is conducted to show that the faulty unmanned airship can track the desired reference even in the presence of actuator faults. Simulation results are presented to show the effectiveness of the proposed control scheme.

Defect Detection for a Vertical Shaft Surface Based on Multimodal Sensors

Hydroelectricity is a major source of renewable electricity originating from a turbine driven by dammed large-volume water via a penstock or a drop shaft. Shafts suffer from risks of collapse due to the pressure from exterior structures and the erosion from inner water flow. Vertical shafts are an important part of hydroelectric power generation systems, and detecting defects in shafts guarantees the stable operation of hydropower stations. However, shaft defect detection is a great challenge due to the poor conditions, large drop in height, limited entrance size, lack of light and damp air, where suitable technology and equipment are not available. Aiming at defect detection for vertical shafts, we have developed a defect-detecting system based on unmanned airships, integrated panoramic CCD cameras, 3D laser scanners, inertial measurement units, barometric altimeters, illumination sensors, and control modules. Shaft defect detection methods (SDDMs) are proposed by fusing the multi-modal image features to extract typical defects on concrete surfaces. Compared with machine learning methods, the proposed method achieves the highest overall accuracy of 90.90&#x0025; for defect detection. Our system was validated by experiments in the shafts of the Nuozhadu hydropower station to be functional for defect detection, which demonstrates its capability of reducing the risk of collapse and improving safety.

ПРИМЕНЕНИЕ ПЕРСПЕКТИВНОГО МНОГОФУНКЦИОНАЛЬНОГО ЭШЕЛОНИРОВАННОГО ВОЗДУШНОГО КОМПЛЕКСА НА БАЗЕ ЛЕТАТЕЛЬНЫХ АППАРАТОВ ЛЕГЧЕ ВОЗДУХА В ОРГАНАХ ВНУТРЕННИХ ДЕЛ

Introduction: The paper substantiates a justification for the use of Lighter-Than-Air aircrafts in the interests of the internal affairs bodies of the Russian Federation. Purpose: Аnalysis of existing Heavier-Than-Air unmanned aircrafts and Lighter-Than-Air aircrafts capabilities, as well as review of a wide range of payloads with the aim of synthesis of the multilevel aerial complex destined for the internal affairs bodies. Results: Based on the analysis of existing unmanned aerial vehicles and Lighter-Than-Air aircrafts, the article proposes the composition and further use of multifunctional echeloned air complex based on lighter-than-air aircrafts designed for the internal affairs bodies. Taking into consideration the internal affairs bodies tasks specificity, various options of an air complex construction scheme, as well as its equipment with designed and existing payload modules, are proposed. Practical relevance: Practical recommendations for the construction of a two-tier scheme air complex for internal affairs bodies based on Lighter-Than-Air aircrafts have been developed. The first tier is built on well-known samples of tethered balloon complexes (stationary component) and medium-altitude unmanned airships (mobile component), as well as perspective small (up to 50 kilograms of payload) and ultra-small (up to 20 kilograms of payload) tethered and unmanned aerial vehicles (stationary and mobile components) proposed in this article. The second tier comprises the unmanned high-altitude aerostatic platforms (mobile component). Discussion: the results obtained in the article are proposed to be used for the calculation of the individual modules performance characteristics, of the performance characteristics of a repeater system built on the basis of airships and for developing an algorithm for the coordination control of the interoperable Lighter-Than-Air aircrafts and Heavier-Than-Air unmanned aircrafts.

БЕСПИЛОТНАЯ ГОРОДСКАЯ АЭРОМОБИЛЬНОСТЬ: ТЕХНОЛОГИИ БЛИЖАЙШЕГО БУДУЩЕГО

The further development of urban mobility, taking into account the latest technical and technological achievements, is considered by many leading vehicle manufacturers in creating and introducing unmanned urban air mobile vehicles into the urban environment. Despite the fact that currently the development of these means of transportation of passengers and cargo is actually in the technical plane - the integral success of introducing this type of transport depends on multiple socio-technological aspects of this phenomenon, which will have various social consequences. The objective of this paper is to identify the socio-technological issues of the phenomenon of unmanned urban air mobility. The result of this paper is to make recommendations to developers of unmanned urban air mobile vehicles in order to minimize the damage from ignoring the negative socio-technological consequences of introducing this type of transport into the urban environment. The novelty of the paper lies in the fact that this type of transport was studied not from a technical and technological point of view, which is the leading one at this stage, but using a socio-technological approach. The paper clearly proves that unmanned urban air mobile vehicles are also multifaceted social objects.

Stabilization of an Unconventional Large Airship When Hovering

In this paper, we present the stabilization of an unconventional unmanned airship above a loading and unloading area. The study concerns a quad-rotor flying wing airship. This airship is devoted to freight transport. However, during the loading and unloading phases, the airship is very sensitive to squalls. In this context, we present in this paper the dynamic model of the airship, and we propose a strategy for controlling it under the effects of a gust of wind. A feedforward/feedback control law is proposed to stabilize the airship when hovering. As part of the control allocation, the non-linear equations between the control vectors and the response of the airship actuators are highlighted and solved analytically through energy optimization constraints. A comparison with classical numerical algorithms was performed and demonstrated the power and interest of our analytic algorithm.

Computational Aerodynamics Study of Competing Conceptual Designs for Advanced Tactical Fighter Aircraft

Advanced tactical fighter (ATF) configurations are bound to perform high angle of attack (AoA) maneuvers. However, existing conceptual design tools available in aerospace industry are based on empirical or potential flows that cannot predict aerodynamic data in nonlinear regimes. High-fidelity computational fluid dynamics algorithms have to be incorporated during conceptual design phase for better assessment between competing configurations. In this research, steady state aerodynamic analysis is conducted to compare four conceptual designs of advanced tactical fighters through Reynolds-averaged Navier–Stokes (RANS) simulations. Prior to the study, two validation test cases were conducted based on ONERA M6 Wing and benchmark unmanned combat air vehicle (UCAV) design to assess the computational setup for the problem. Pressure based solver is used to model the flow field in subsonic, transonic and supersonic regimes at sea level for all four competing designs. The quantitative results include the aerodynamic forces and the longitudinal stability coefficient comparisons among the models and its components. The qualitative analyses include pressure distribution, eddy shedding and behavior of vortices at varying flow angle. Additionally, the empirical estimation for interpolation and post-stall extrapolation are carried out for further flight performance studies.

Design of indoor unmanned airship propelled by ionic wind

The indoor unmanned airship is a lighter-than-air aircraft that can hover in the air for a long time without consuming energy. Indoor unmanned airships are widely used in indoor inspections, special operations, commercial advertising, education and scientific research. In this paper, an indoor unmanned airship propelled by ionic wind is designed. The airship can complete motions such as forward and yaw, and almost no noise and vibration are generated during the working process.

Neural network adaptive backstepping fault tolerant control for unmanned airships with multi-vectored thrusters

This paper presents the fault tolerant control (FTC) of an unmanned airship with multiple vectored thrusters in the presence of model parameter uncertainties and unknown wind disturbances. A fault tolerant control based on constrained adaptive backstepping (CAB) approach, combined with a radial basis function neural network (RBFNN) approximation, is proposed for the airship with thruster faults. A wind observer is designed to estimate the bounded wind disturbances. An adaptive fault estimator is proposed to estimate the unknown actuator faults. A weighted pseudo inverse based control allocation is incorporated to reconstruct and optimize the practical control inputs of the failed airship under constraints of actuator saturation. Rigorous stability analysis shows that trajectory tracking errors of the airship position and attitude converge to the desired set through Lyapunov theory. Numerical simulations demonstrate the fault tolerant trajectory tracking capability of the proposed NN-CAB controller under the actuator faults, even in the presence of aerodynamic coefficient uncertainties, and unknown wind disturbances.

Development of a power plant for an unmanned airship

In this work, a power plant layout for an unmanned airship was designed and tested. The layout is designed to provide power to the target load with a rated power of not more than 500 W, peak power of not more than 1000 W and daily energy consumption of not more than 2600 W · h (of which in the dark - no more than 1300 W · h) with a daily total solar radiation not less than 5.51 kW · h / m2 (daily average for July in the Moscow region is given). Testing the layout, which consists in checking the characteristics of individual elements of the layout in ground-based conditions, has shown the feasibility of using airships in the service sectors.

Development of an unmanned airship for magnetic exploration

An unmanned airship was used to overcome the limitations of conventional aeromagnetic exploration systems. The airship was fabricated from non-magnetic fibre-reinforced plastic and urethane cloth, and filled with helium. The maximum payload is 10 kg and the flight time (with all equipment installed) is approximately 1 h. The airship is simple to move and store prior to gas injection, and easy to handle in the field because of its small size. An automatic flight algorithm enables stable and efficient exploration. A radiofrequency modem and long-term evolution router connect the airship to ground control even when it is not in the line of sight. Magnetic data and airship location are monitored in real time and verified using a helicopter. The airship showed high efficiency.

Characterization of Back-Scattering and Multipath in a Suburban Area after the Calibration of an X-Band Commercial Radar.

The increasing interest in the radar detection of low-elevation and small-size targets in complicated ground environments (such as urban, suburban, and mixed country areas) calls for a precise quantification of the radar detection capabilities in those areas. Hence, a set of procedures is devised and tested, both theoretically and experimentally, using a commercial X-band radar, to (i) calibrate the radar sensor (with an online evaluation of its losses) using standard scatterers, (ii) measure the multipath effect and compensate for it, and (iii) create “true radar cross section” maps of the area of interest for both point and distributed clutter. The above methods and the related field results are aimed at future qualification procedures and practical usage of small, cheap, and easily moveable radars for the detection of low-observable air targets, such as unmanned air vehicles/systems (UAV/UAS), in difficult ground areas. A significant set of experimental results as discussed in the paper confirms the great relevance of multipath in ground-based radar detection, with the need for correcting measures.

Assessing the Impact of Land Cover Changes on Surface Urban Heat Islands with High-Spatial-Resolution Imagery on a Local Scale: Workflow and Case Study

Low-altitude remote sensing platform has been increasingly applied to observing local thermal environments due to its obvious advantage in spatial resolution and apparent flexibility in data acquisition. However, there is a general lack of systematic analysis for land cover (LC) classification, surface urban heat island (SUHI), and their spatial and temporal change patterns. In this study, a workflow is presented to assess the LC’s impact on SUHI, based on the visible and thermal infrared images with high spatial resolution captured by an unmanned airship in the central area of the Sino-Singapore Guangzhou Knowledge City in 2012 and 2015. Then, the accuracy assessment of LC classification and land surface temperature (LST) retrieval are performed. Finally, the commonly-used indexes in the field of satellites are applied to analyzing the spatial and temporal changes in the SUHI pattern on a local scale. The results show that the supervised maximum likelihood algorithm can deliver satisfactory overall accuracy and Kappa coefficient for LC classification; the root mean square error of the retrieved LST can reach 1.87 °C. Moreover, the LST demonstrates greater consistency with land cover type (LCT) and more fluctuation within an LCT on a local scale than on an urban scale. The normalized LST classified by the mean and standard deviation (STD) is suitable for the high-spatial situation; however, the thermal field level and the corresponded STD multiple need to be judiciously selected. This study exhibits an effective pathway to assess SUHI pattern and its changes using high-spatial-resolution images on a local scale. It is also indicated that proper landscape composition, spatial configuration and materials on a local scale exert greater impacts on SUHI.

Adaptive neural dynamic surface control of MIMO uncertain nonlinear systems with time-varying full state constraints and disturbances

In order to stabilize multiple-input–multiple-output uncertain strict feedback nonlinear systems with time-varying full-state constraints and external disturbances, an adaptive neural dynamic surface control method is investigated in this paper. A new compensator is proposed, which combines approximation error based adaptive radial basis function neural networks (RBFNNs) and nonlinear disturbance observer (NDOB) to improve the compensate performance of unmodeled dynamics and external disturbances. To prevent that the time-varying full state constraints are violated, the controller is designed via asymmetric time-varying barrier Lyapunov function (ATBLF). Meanwhile, the dynamic surface control is established to avoid the problem of “explosion of complexity” in traditional backstepping design. All closed-loop signals are proved to be semiglobally uniformly ultimate bounded through stability analysis. Finally, the simulation for six degrees of freedom (6-DOF) model unmanned airship are given to illustrate the effectiveness of the proposed control method.