Rotary-wing Unmanned Aerial Vehicle Research Articles

UAVs Trajectory Planning by Distributed MPC under Radio Communication Path Loss Constraints

In this paper, a distributed linear MPC approach to solve the trajectory planning problem for rotary-wing UAVs is proposed, where the objective of the UAV system is to form a communication network to multiple targets with given radio communication capacities. The approach explicitly incorporates constraints on radio communication path losses, computed by using SPLAT! that is able to take into account terrain models and antenna locations. In order to enhance the online optimization, at each time sample the terrain below each UAV and the communication path losses are approximated with linear functions of the spatial coordinates. This leads to linear MPC sub-problems, which are solved by using convex quadratic programming. An algorithm for automatic initialization and optimal reconfiguration of the communication topology in case of failures or severe radio path loss due to e.g. channel fading, is proposed. The communication network that is provided by the UAVs is considered to be a payload communication capacity that is normally independent of the command and control datalink used to control the UAVs. The performance of the distributed linear MPC trajectory planning and the reconfiguration algorithm is studied on two simulation cases with four UAVs and two targets.

A methodology for the identification of inertial properties of small size UAVs

This paper illustrates a procedure for estimating the inertial properties of small size aerial vehicles. An identification algorithm has been developed that, starting from experimental data, estimates the parameters of a physical model describing the pendular motion of a generic rigid body. The attitude time histories of a structure (“cage”), carrying the object whose inertial properties have to be evaluated, are the experimental data obtained through a measurement unit attached to the cage itself. The cage, designed in order to facilitate the assembly issues, is put in pendular motion thanks to a needle shaped pivot, placed to the cage top and leaning against a beam. Before proceeding to the identification of the aerial vehicle inertial properties, several tests have been performed to evaluate the performance of the algorithm. A preliminary effectiveness of the algorithm has been assessed via simulation environment, by artificially creating “virtual” time histories. Afterwards, the algorithm has been validated experimentally by loading the cage with a proof mass of known inertial characteristics. During these experimental tests, specific attention has been focused on the effect of the cage initial attitude on the inertial properties estimate. After this algorithm test phase, the developed methodology has been applied to a small rotary-wing UAV in order to evaluate its inertial properties.

Assessment of Photogrammetric Mapping Accuracy Based on Variation Flying Altitude Using Unmanned Aerial Vehicle

Photogrammetry is the earliest technique used to collect data for topographic mapping. The recent development in aerial photogrammetry is the used of large format digital aerial camera for producing topographic map. The aerial photograph can be in the form of metric or non-metric imagery. The cost of mapping using aerial photogrammetry is very expensive. In certain application, there is a need to map small area with limited budget. Due to the development of technology, small format aerial photogrammetry technology has been introduced and offers many advantages. Currently, digital map can be extracted from digital aerial imagery of small format camera mounted on light weight platform such as unmanned aerial vehicle (UAV). This study utilizes UAV system for large scale stream mapping. The first objective of this study is to investigate the use of light weight rotary-wing UAV for stream mapping based on different flying height. Aerial photograph were acquired at 60% forward lap and 30% sidelap specifications. Ground control points and check points were established using Total Station technique. The digital camera attached to the UAV was calibrated and the recovered camera calibration parameters were then used in the digital images processing. The second objective is to determine the accuracy of the photogrammetric output. In this study, the photogrammetric output such as stereomodel in three dimensional (3D), contour lines, digital elevation model (DEM) and orthophoto were produced from a small stream of 200m long and 10m width. The research output is evaluated for planimetry and vertical accuracy using root mean square error (RMSE). Based on the finding, sub-meter accuracy is achieved and the RMSE value decreases as the flying height increases. The difference is relatively small. Finally, this study shows that UAV is very useful platform for obtaining aerial photograph and subsequently used for photogrammetric mapping and other applications.

A Miniature Integrated Navigation System for Rotary-Wing Unmanned Aerial Vehicles

This paper presents the development of a low cost miniature navigation system for autonomous flying rotary-wing unmanned aerial vehicles (UAVs). The system incorporates measurements from a low cost single point GPS and a triaxial solid state inertial/magnetic sensor unit. The navigation algorithm is composed of three modules running on a microcontroller: the sensor calibration module, the attitude estimator, and the velocity and position estimator. The sensor calibration module relies on a recursive least square based ellipsoid hypothesis calibration algorithm to estimate biases and scale factors of accelerometers and magnetometers without any additional calibration equipment. The attitude estimator is a low computational linear attitude fusion algorithm that effectively incorporates high frequency components of gyros and low frequency components of accelerometers and magnetometers to guarantee both accuracy and bandwidth of attitude estimation. The velocity and position estimator uses two cascaded complementary filters which fuse translational acceleration, GPS velocity, and position to improve the bandwidth of velocity and position. The designed navigation system is feasible for miniature UAVs due to its low cost, simplicity, miniaturization, and guaranteed estimation errors. Both ground tests and autonomous flight tests of miniature unmanned helicopter and quadrotor have shown the effectiveness of the proposed system, demonstrating its promise in UAV systems.

719 後置静翼による姿勢制御機構を用いた回転翼型UAVのヨー軸回りの姿勢安定化

719 後置静翼による姿勢制御機構を用いた回転翼型UAVのヨー軸回りの姿勢安定化

Radio Controlled “3D Aerobatic Airplanes” as Basis for Fixed-Wing UAVs with VTOL Capability

There are fundamental performance compromises between rotary-wing and fixed-wing UAVs. The general solution to address this well-known problem is the design of a platform with some degree of reconfigurable airframes. For critical missions (civilian or military), it is imperative that mechanical complexity is kept to a minimum to help achieve mission success. This work proposes that the tried-and-true radio controlled (RC) aerobatic airplanes can be implemented as basis for fixed-wing UAVs having both speed and vertical takeoff and landing (VTOL) capabilities. These powerful and highly maneuverable airplanes have non-rotatable nacelles, yet capable of deep stall maneuvers. The power requirements for VTOL and level flight of an aerobatic RC airplane are evaluated and they are compared to those of a RC helicopter of similar flying weight. This work provides quantitative validation that commercially available RC aerobatic airplanes can serve as platform to build VTOL capable fixed-wing UAVs that are agile, cost effective, reliable and easy maintenance.

Evaluation of UAS Class and EO Sensor Payload Type for Applications in Hostage Crisis Missions

Donohue V. (2014). Evaluation of UAS class and EO sensor payload type for applications in hostage crisis missions. International Journal of Unmanned Systems Engineering. 2(1): 1-8. Law Enforcement entities are tasked with ensuring the safety of citizens to the best of their ability. They use every advantage at their disposal to capture and restrain criminals while reducing the risk to civilians. This ability is often limited by the constraints of slim and shrinking budgets. Departments with larger budgets and greater flexibility have historically taken advantage of airborne assets, most often helicopters, which provide a tremendous advantage against criminals due to enhanced surveillance, pursuit, and capture capability. The latest technological advancements in remote electronic sensing, along with major strides in aircraft automation and miniaturization, have allowed a surge in the implementation of Unmanned Aircraft Systems (UAS) in Law Enforcement missions. This paper discusses the use of UAS by Law Enforcement in a hostage crisis situation. A scenario is presented and a Concept of Operations (CONOPS) is developed to thoroughly detail the mission goal, strategy and tactics. The class of UAS appropriate for the mission, including Micro Air Vehicles and small UAS, and a refined selection between fixed wing and rotary wing aircraft are identified. The Draganflyer X6 and the RAPTR rotary wing UAVs are discussed in deciding what system best accomplishes the hostage crisis mission. Electro-optical sensors, including high definition video, low light level TV and infrared sensors, provide superior applicability. © Marques Engineering Ltd.

Rotary Wing UAV pre-sizing : Past and Present Methodological Approaches at Onera

Rotary Wing UAV pre-sizing : Past and Present Methodological Approaches at Onera

MARTIAN SWARM EXPLORATION AND MAPPING USING LASER SLAM

Abstract. In order to explore planet Mars in detail and search for extra-terrestrial life the observation from orbit is not sufficient. To realize complex exploration tasks the use of automatic operating robots with a robust fault-tolerant method of navigation, independent of any infrastructure is a possibility. This work includes a concept of rotary-wing Unmanned Aerial Vehicles (UAVs) and Unmanned Ground Vehicles (UGVs) for Martian exploration in a swarm. Besides the scenario of Martian surrounding, with a small number of distinctive landmarks, the challenge consists of a Simultaneous Localization and Mapping (SLAM) concept using laser data of all swarm members.

Automated Vision‐based Recovery of a Rotary Wing Unmanned Aerial Vehicle onto a Moving Platform

This paper describes an integrated control demonstration in which a rotary wing unmanned aerial vehicle (UAV) landed on a moving platform using vision‐based localization of the target vehicle. Three key areas are covered in this paper: the system components and integration, the control system structure and design, and finally flight test data including the first such successful landing. All the development and demonstration flights were carried out in the field, and key system challenges and lessons learned are highlighted throughout the paper. Results are given for landings carried out on both stationary and translating targets, in wind speeds of up to 15 knots. While the translating target was constrained to linear motion, there are several applications such as recovery to a land‐based convoy for which this capability would be applicable. The results show that the approach adopted for this demonstration could form part of a practical solution to the problem of automated UAV recovery in both civilian and military environments.

Development and Flight Test Evaluations of an Autonomous Obstacle Avoidance System for a Rotary-Wing UAV

This paper presents the development and flight-testing of an obstacle avoidance system that can provide a rotary-wing unmanned aerial vehicle (UAV) the autonomous obstacle field navigation capability in uncertain environment. The system is composed of a sensor, an obstacle map generation algorithm from sensor measurements, an online path planning algorithm, and an adaptive vehicle controller. The novel approach of path planning presented in the paper is the integration of a newly developed receding horizon (RH) trajectory optimization scheme with a global path searching algorithm. The developed RH trajectory optimization scheme solves the local nonlinear trajectory optimization problem using approximated vehicle dynamics, maneuverability constraints, and terrain constraints within the finite range of the sensor. The global path searching by dynamic programming algorithm finds the shortest path to the destination to provide the initial guess to the RH trajectory optimization. The spline-based direct solver, Nonlinear Trajectory Generation (NTG), solves the RH trajectory optimization in real time and updates the solution continuously. The developed system is implemented within the Georgia Tech UAV Simulation Tool (GUST) and on the onboard computer of the Georgia Tech UAV test bed. Simulations and flight tests carried out for the benchmark scenarios and with sensor-in-the-loop flight tests demonstrated the viability of the developed system for autonomous obstacle field navigation capability of a UAV.

BLACK-BOX TOOL FOR NONLINEAR SYSTEM IDENTIFICATION BASED UPON FUZZY SYSTEM

This paper introduces a novel identifier scheme for identification of nonlinear systems with disturbances. The identification process is carried out in two steps: an offline procedure and an online procedure. The method comprises of an automatic structure generating phase using entropybased technique. The accuracy of the model is suitably controlled using the entropy measure. The parameter learning phase uses the backpropagation technique. To improve the accuracy and also for generalization of the model to handle different data sets, Differential Evolution technique is employed whereby the parameters of the model are suitably tuned using evolutionary technique. A semi serial-parallel model is introduced to improve the online identification process in the presence of noisy data. The proposed mechanism is utilized and compared against the classical Sugeno, adaptive network-based fuzzy inference system (ANFIS) modeling and Laguerre Network-Based Fuzzy System for the identification of a nonlinear benchmark problem. In addition, the proposed technique is also used to model a rotary wing unmanned aerial vehicle (UAV) from real test input–output data. The modeling performance and generalization capability are seen to be superior with our method.

Displacement motion prediction of a landing deck for recovery operations of rotary UAVs

This paper proposes a practical prediction procedure for vertical displacement of a Rotarywing Unmanned Aerial Vehicle (RUAV) landing deck in the presence of stochastic sea state disturbances. A proper time series model tending to capture characteristics of the dynamic relationship between an observer and a landing deck is constructed, with model orders determined by a novel principle based on Bayes Information Criterion (BIC) and coefficients identified using the Forgetting Factor Recursive Least Square (FFRLS) method. In addition, a fast-converging online multi-step predictor is developed, which can be implemented more rapidly than the Auto-Regressive (AR) predictor as it requires less memory allocations when updating coefficients. Simulation results demonstrate that the proposed prediction approach exhibits satisfactory prediction performance, making it suitable for integration into ship-helicopter approach and landing guidance systems in consideration of computational capacity of the flight computer.

Rotary-Wing UAVs Trajectory Planning by Distributed Linear MPC with Reconfigurable Communication Network Topologies

In this paper, a distributed approach to Model Predictive Control (MPC)-based trajectory planning for rotary-wing UAV (Unmanned Aerial Vehicle) communication network topologies under radio path loss constraints is proposed. The goal is to find trajectories that are safe with respect to grounding and collision, fuel efficient and satisfy criteria for communication such that the UAVs form chains to multiple targets with given radio communication capacities. The MPC-based optimization sub-problems are computed autonomously within each UAV, using convex quadratic programming, with the requirement that each UAV communicates its current measured position to all other UAVs. In addition, a simple coordination between UAVs allows for the communication network topology to be reconfigured in case of failures or radio path loss changes. The control performance of the distributed linear MPC trajectory planning is studied based on a simulation case with four UAVs and two targets.

Integrated Planning and Control of Rotary-wing Unmanned Aerial Vehicle Navigation

This paper presents an integrated planning and control algorithm for the navigation of an autonomous rotarywing unmanned aerial vehicle in a cluttered environment. The model predictive control combined with a potential fieldlike function integrates planning and control in a single step. This strategy enables the generation of dynamically feasible motion because the planning is done in the action space of the rotary-wing unmanned aerial vehicle. Moreover, it is able to respond promptly to abrupt changes in the environment because the reactive obstacleavoidance method only considers local sensory information. Finally, the shortsightedness of control-based reactive methods can be relieved by the larger planning horizon of the model predictive control. Simulation results show that the proposed integrated planning and controlmethod can complete the navigationmission successfully in a cluttered environment, and it can be applicable to more complicated missions, such as weed surveillance and management.

EFFECTS OF PROPELLER BLADE TWIST ON RECONNAISSANCE QUAD-ROTOR UAV

ABSTRACTRotors play a pivotal role in the overall performance of a rotary-wing aircraft. Forcesand moments required for flight are achieved through effective, compact and high-liftrotor design. Important rotor parameters are thrust, power and torque, which arefunctions of blade twist and rotor radius. A robust and efficient rotary-wing UAV flightcontrol system must provide the vehicle with the ability to perform safe flightmanoeuvres. This comprise normal flight conditions and proportionate regulation ofthrust in response to the variation in power demand, which comes to play due tochanges in aerodynamics conditions within the vehicle operating environment. Thispaper presents an in-depth analysis on the effect of variations of propeller blade twistand diameter with the view to designing an autonomous flight control system for amicro rotary-wing UAV. Virtual Blade Model (VBM) was used for the analysis and theresult validated using a quad-rotor vehicle. The study comes up with an efficientpropeller choice suitable for autonomous reconnaissance quad-rotor UAV.

A simulation study on the capabilities of rotor wing unmanned aerial vehicle in aerial terrain mapping

Many applications can be solved by using the unmanned aerial vehicle (UAV) technology such as farming, surveillance, monitoring, fire disaster, flood monitoring and aerial terrain mapping. This study was carried out to investigate the use of light weight rotary-wing UAV for mapping simulation model. The accuracy of photogrammetric product will be assessed as one of the objectives of this study. There are two types of UAV units known as rotor wing and fixed-wing. Based on few studies, rotor wing units are more stable and are able to capture images easily. It allows remote control UAV to be practiced in the environment and urban mapping. In the simulation model, ground control points (GCP) and checked point (CP) were established using total station. The GCP is used in the photogrammetric processes to produce photogrammetric output while the CP is used for accuracy assessment. This study also used a low cost digital camera in image acquisition to capture the aerial image of a simulated model. Two methods were implemented in this study. In the first method, the camera was mounted vertically at a fixed height on the simulated model. In the second method, the camera was mounted vertically; it was then attached at the bottom of rotary-wing UAV and the images were captured at an altitude. The productions of digital orthophoto and digital elevation model of the simulated model were obtained after the acquired images were processed using the photogrammetric software. Based on the finding, the root mean square errors (RMSEs) for fixed platform are ±0.002, ±0.001 and ±0.214 for coordinate x, y and z, respectively while the RMSE for UAV platform are ±0.002, ±0.002 and ±0.223 for coordinate x, y and z, respectively. It can be concluded that the differences between the mobile and fixed platforms are small. In conclusion, UAV system can be used for large scale mapping of aerial terrain mapping. Key words: Mobile mapping, non-metric, digital elevation models (DEM), photogrammetry, simulation.

Non-linear position control for hover and automatic landing of unmanned aerial vehicles

This study presents a disturbance attenuation controller for horizontal position stabilisation for hover and automatic landings of a rotary-wing unmanned aerial vehicle (RUAV) operating close to the landing deck in rough seas. Based on a helicopter model representing aerodynamics during the landing phase, a non-linear state feedback ℋ∞ controller is designed to achieve rapid horizontal position tracking in a gusty environment. Practical constraints including flapping dynamics, servo dynamics and time lag effect are considered. A high-fidelity closed-loop simulation using parameters of the Vario XLC gas-turbine helicopter verifies performance of the proposed horizontal position controller. The proposed controller not only increases the disturbance attenuation capability of the RUAV, but also enables rapid position response when gusts occur. Comparative studies show that the ℋ∞ controller exhibits performance improvement and can be applied to ship/RUAV landing systems.

Model-Based Design, Development and Validation for UAS Critical Software

This paper focuses on the major phases present in the development of critical software for UAS: design, development, testing and validation with flying experiments. A model-based approach is the backbone of all these development phases. The presented approach enables the researchers or engineers to work over the whole development cycle with the same tools, and produces an improvement over the classical design cycle. The model-based approach is illustrated with the development of guidance, navigation and control algorithms applied to rotary-wing UAVs. The paper discusses several implementation issues, including the integration of a hardware in the loop (HWIL) test environment within the model-based development cycle. Finally, several simulations and experimental results for this application are shown.

Flight validation of a feedforward gust-attenuation controller for an autonomous helicopter

This paper presents a practical scheme to control heave motion for hover and automatic landing of a Rotary-wing Unmanned Aerial Vehicle (RUAV) in the presence of strong horizontal gusts. A heave motion model is constructed for the purpose of capturing dynamic variations of thrust due to horizontal gusts. Through the construction of an effective gust estimator, a feedback–feedforward controller is developed which uses available measurements from onboard sensors. The proposed controller dynamically and synchronously compensates for aerodynamic variations of heave motion, enhancing disturbance-attenuation capability of the RUAV. Simulation results justify the reliability and efficiency of the suggested gust estimator. Moreover, flight tests conducted on our Eagle helicopter verify suitability of the proposed control strategy for small RUAVs operating in a gusty environment.