Unmanned Air Research Articles

RESEARCH ON THE KEY TECHNOLOGY OF LARGE SCALE MAPPING FROM LOW ALTITUDE PHOTOGRAMMETRY

Abstract. Based on the theoretic analysis of the accuracy in large scale photogrammetric mapping, some defects in traditional procedure were discussed. A set of key technologies dedicate to accuracy improvement in low altitude photogrammetry were analyzed in detail, namely the utilization of wide angle camera and low altitude flight, enhancement in image matching, predesigned layout of Ground Control Points (GCPs) in field survey, optimization of adjustment model and improvement in map processing. Besides, a low altitude aerial unmanned airship system was established. Finally, successful implementation in 1:500 topographic mapping project in built-up areas of 30 counties in Shanxi Province proves the practicability and effectiveness of the proposed approaches.

Design of Predictive Controller Based on Linear Optimization for Unmanned Airship

Design of Predictive Controller Based on Linear Optimization for Unmanned Airship

Modelling and preliminary results of a tri-ellipsoid unmanned autonomous airship

Unmanned autonomous airship has its own advantages over other aerial vehicles in near-ground surveillance and rescue tasks. In this study, we present a novel designed unmanned autonomous blimp. We built the dynamic model of the tri-ellipsoid blimp then we designed an anti-wind controller based on the model. We also implemented the prototype which included the tri-ellipsoid blimp body, the flying control system and the ground communication station. We carried out field experiments including payload experiment, remote control experiment and automatic flying experiment to validate the system. Experimental results demonstrate that the proposed blimp is a potential tool in accomplishing tasks of near-ground search with large payloads.

A Mixed H<sub>2</sub>/H<sub>∞ </sub> Jump Markovian Design Approach for the Automatic Flight Control System of an Unmanned Airship

This paper presents a design methodology for the heading control system of an unmanned airship. Since the aircraft motion depends both on deterministic command signals required for tracking a desired path and on random exogenous inputs modelling the wind influence, a mixed H2/H-infinity type method have been chosen for the design of the automatic flight control. Moreover, due to the fact that the vehicle dynamics at straight and level flight is different from the model at level turning flight, a stochastic Markovian model with two states is adopted to simulate these two situations. A design methodology for a state-feedback controller with Markov jumps is presented. The theoretical developments are illustrated by numerical comparative results indicating the benefits of proposed optimal design approach.

An Unmanned Airship Thermal Infrared Remote Sensing System for Low-Altitude and High Spatial Resolution Monitoring of Urban Thermal Environments: Integration and an Experiment

Satellite remote sensing data that lacks spatial resolution and timeliness is of limited ability to access urban thermal environment on a micro scale. This paper presents an unmanned airship low-altitude thermal infrared remote sensing system (UALTIRSS), which is composed of an unmanned airship, an onboard control and navigation subsystem, a task subsystem, a communication subsystem, and a ground-base station. Furthermore, an experimental method and an airborne-field experiment for collecting land surface temperature (LST) were designed and conducted. The LST pattern within 0.8-m spatial resolution and with root mean square error (RMSE) value of 2.63 °C was achieved and analyzed in the study region. Finally, the effects of surface types on the surrounding thermal environment were analyzed by LST profiles. Results show that the high thermal resolution imagery obtained from UALTIRSS can provide more detailed thermal information, which are conducive to classify fine urban material and assess surface urban heat island (SUHI). There is a significant positive correlation between the average LST of profiles and the percent impervious surface area (ISA%) with R2 around 0.917. Overall, UALTIRSS and the retrieval method were proved to be low-cost and feasible for studying micro urban thermal environments.

Gain-scheduling model predictive control for unmanned airship with LPV system description

This paper presents a gain-scheduling model predictive control (MPC) for linear parameter varying (LPV) systems subject to actuator saturation. The proposed gain-scheduling MPC algorithm is then applied to the lateral control of unmanned airship. The unmanned airship is modeled by an LPV-type system and transformed into a polytopic uncertain description with actuator saturation. By introducing a parameter-dependent state feedback law, the set invariance condition of the polytopic uncertain system is identified. Based on the invariant set, the gain-scheduling MPC controller is presented by solving a linear matrix inequality (LMI) optimization problem. The proposed gain-scheduling MPC algorithm is demonstrated by simulating on the unmanned airship system.

Design of a Solar Powered, Unmanned, Low Altitude, High Endurance Airship

This article presents the design of a low altitude long endurance solar powered unmanned airship. In the first part of the article, a brief introduction about the airships, their potential areas of usage, the advantages of using an unmanned air vehicle, and a comparison between unmanned counterparts will be given. In the second part, the design criteria and the general design specifications will be outlined briefly. During the design, emphasis is given on the general design parameters of the Lighter Than Air (LTA) vehicles. Lastly, the detailed design results, in order to reach the projected design parameters, have been presented.

Control Parameters Optimization Based on Co-Simulation of a Mechatronic System for an UA-Based Two-Axis Inertially Stabilized Platform.

This paper presents a method based on co-simulation of a mechatronic system to optimize the control parameters of a two-axis inertially stabilized platform system (ISP) applied in an unmanned airship (UA), by which high control performance and reliability of the ISP system are achieved. First, a three-dimensional structural model of the ISP is built by using the three-dimensional parametric CAD software SOLIDWORKS®; then, to analyze the system’s kinematic and dynamic characteristics under operating conditions, dynamics modeling is conducted by using the multi-body dynamics software ADAMS™, thus the main dynamic parameters such as displacement, velocity, acceleration and reaction curve are obtained, respectively, through simulation analysis. Then, those dynamic parameters were input into the established MATLAB® SIMULINK® controller to simulate and test the performance of the control system. By these means, the ISP control parameters are optimized. To verify the methods, experiments were carried out by applying the optimized parameters to the control system of a two-axis ISP. The results show that the co-simulation by using virtual prototyping (VP) is effective to obtain optimized ISP control parameters, eventually leading to high ISP control performance.

Experimental analysis of artificial dragonfly wings using black graphite and fiberglass for use in Biomimetic Micro Air Vehicles (BMAVs)

This article examines the suitability of two different materials which are black graphite carbon fiber and red pre-impregnated fiberglass from which to fabricate artificial dragonfly wing frames. These wings could be of use in Biomimetic Micro Aerial Vehicles (BMAV). BMAV are a new class of unmanned micro-sized air vehicles that mimic flying biological organisms. Insects, such as dragonflies, possess corrugated and complex vein structures that are difficult to mimic. Simplified dragonfly wing frames were fabricated from these materials and then a nano-composite film was adhered to them, which mimics the membrane of an actual dragonfly. Experimental analysis of these results showed that although black graphite carbon fiber and red pre-impregnated fiberglass offer some structural advantages, red pre-impregnated fiberglass was a less preferred option due to its warpage and shrinking effects. Black graphite carbon fiber with its high load bearing capability is a more suitable choice for consideration in future BMAV applications.

Manned-unmanned teaming: expanding the envelope of UAS operational employment.

Abstract : The employment of unmanned aerial systems (UAS) has become ubiquitous, not only within modern multinational militaries, but also among the civilian and commercial aviation communities. Although the concept of UAS application dates much farther back than most realize (unmanned balloons were used during the American Civil War for ordnance delivery with limited success, for example), most trace the origins of contemporary apposite UAS application to the Israelis and Americans in the 1970s and 1980s ( 11 ). Over the past few decades, there has been rapid expansion of UAS technology, capability, and employment strategies on many fronts. One of these important developments includes interoperability of manned and unmanned aerial platforms to enhance mission command and complement combat power. Titled Manned-Unmanned Teaming (MUM-T), this entails the synchronized employment of manned and unmanned air (and ground) vehicles, sensors, and weapons systems. The concept has existed for decades, but relatively recent advances in technology and doctrine have spearheaded the movement from concept to real-world application. And as development continues to swiftly mature, the aerospace medical community at large would do well to pay attention. Many of these applications, while no doubt providing enhanced capability, may pose aeromedical and human factors challenges to which we should remain vigilant. These may include (but are not limited to) visual overload, increased workload and task saturation, distraction and diminished fl ight situation awareness (SA), motion sickness, and spatial disorientation (SD).

Design and Fabrication of a Scaled-Down Unmanned Quad-Tilt-Prop Personal Air Vehicle

AbstractThis paper describes the design, fabrication, and test of a scaled-down unmanned personal air vehicle (PAV) with dual mode drive and flight capabilities. Considerations of the operational requirements of such a vehicle led to the concept of a quad-tilt-prop platform that has nacelle tilt capability with a multiple rotor configuration. Motors for both propeller propulsion and the driving mechanism were integrated into a single nacelle, and they were then implemented with a nacelle tilt mechanism for conversion between the drive and flight modes. The primary design parameters were examined through the conceptual design process, as follows: (1) overall dimensions, (2) empty weight, (3) propeller diameter, and (4) propulsion motor were determined based on design requirements. Functional tests were then performed, with test platforms designated for each development step. Comprehensive drive and flight tests demonstrated the operational capabilities of the finalized prototype. The fabricated vehicle has...

Solving the Problem of UAV Air Combat Game Based on Differential Variational Inequality and D-Gap Function

The strategy of unmanned aerial vehicle air combat can be described as a differential game problem. The analytical solutions for the general differential game problem are usually difficult to obtain. In most cases, we can only get its numerical solutions. In this paper, a Nash differential game problem is converted to the corresponding differential variational inequality problem, and then converted into optimal control problem via D-gap function. The nonlinear continuous optimal control problem is obtained, which is easy to get numerical solutions. Compared with other conversion methods, the specific solving process of this method is more simple, so it has certain validity and feasibility.

Positioning control for an unmanned airship using sliding mode control based on fuzzy approximation

This paper addresses the positioning problem of an unmanned airship in the presence of parametric uncertainties and external disturbances. A sliding mode controller (SMC) based on fuzzy approximati...

Real-time Desktop Flying Qualities Evaluation Simulator

This paper presents the application of model based design for the development of a real-time flying quality evaluation simulator named NALSim, built around Windows platform. NALSim is a novel rapid prototyping system based on MatlabR, SimulinkR and the Real-Time-Windows TargetR, applicable for fighter, transport and unmanned air vehicles/micro air vehicles simulations. The simulator uses state of the art modeling and simulation technologies to validate various design and flying quality concepts. NALSim is developed such that it is scalable and low cost. The paper presents the simulator architecture and its application for flying qualities. A novel non linear Least Squares optimization based methodology is proposed for efficient handling quality studies. Defence Science Journal, Vol. 64, No. 1, January 2014, DOI:10.14429/dsj.64.4961

Micro air vehicle trajectory generation in pitch plane

For autonomous operations, unmanned micro air vehicles depend on novel trajectory generation schemes. Trajectories parallel to the ground are fairly well understood in surveillance and reconnaissance contexts. In addition, trajectories with altitude as one of the navigational parameters are also envisioned for aerial robots, urban terrain coverage, etc. In these missions, trajectory generation in pitch plane becomes an important problem. In this article, a linear algebraic procedure is applied to generate the pitch plane trajectories. That is, when a terrain (latitude, longitude and altitude) is sensed from a global positioning system, a trajectory to navigate the aircraft along the terrain is presented. By linear algebra, the state vector is spanned using a set of known vectors and some of their scalars (coefficients of spanning vectors) are solved in an optimization framework so that the state variables mapping the desired terrain are determined. After the trajectories are generated, normally smoothening is recommended so that the trajectories are continuous for autonomous control development. Thus, an extended Kalman filter is applied to smooth the trajectories. A nonlinear micro air vehicle model is considered to illustrate the trajectory generation and smoothening scheme.

Autonomous Control Agents for Adaptive MAV Mission Profiles

When a mission profile of an unmanned micro air vehicle is known a priori, one of the strategies adopted in autonomous control is to first generate a compatible trajectory in off-line and then implement a controller to track the trajectory. However, in decision rich intelligent aerial robots and in 6DOF operations of unmanned aerial vehicles, the mission profiles are usually known during an operation. Hence the trajectories are instantaneously inferred. Here an adaptive controller with capabilities to track these trajectories is required. In this paper, it is shown that an extended Kalman filter is an excellent tool to design such a controller which accepts the trajectory generation module as an input and then reconstructs its trajectories. To illustrate this feature, a 3DOF micro air vehicle in pitch plane is considered and an adaptive controller (referred as autonomous control agent) using an extended Kalman filter is applied to infer typical adaptive mission profiles.

Unmanned Airship Based High Resolution Images Acquisition and the Processing

Low altitude high resolution aerial images captured by Unmanned Airship (UA) have great potentials in application of environment investigation and large scale mapping. Taken Miyun, Beijing as the test area, a UA-based imaging system was employed and 640 aerial images at 370m and 430 images at 170m were captured. Then photogrammetric processing of these images, including preprocessing, image matching, aerial triangulation and panorama stitching, are described in detail. The ground resolution of final panorama is 15 mm, and space precision is 0.00136, approximately 0.25 pixels. To assess the image quality quantitatively, remote sensing images on SPOT and Quickbird are compared with unmanned airships by swiping horizontally and vertically. What’s more, the correction error of overlap is less than 0.5 pixels. Therefore, the images captured by UA, valuable complements of satellite remote sensing, are reliable and capable of meeting practical demands.

A directional control system for UCAV automatic takeoff roll

PurposeThe purpose of this paper is to develop a directional and roll control system for unmanned combat air vehicle (UCAV) automatic takeoff roll, with the objective of keeping the UCAV along the runway centerline and keeping the wings level, especially when there is a crosswind.Design/methodology/approachThe nonlinear model of the UCAV during takeoff roll is established. The model is linearized about the lateral‐directional equilibrium point at different forward speeds. The approximate directional model and roll model are extracted using time‐scale decomposition technique. Then the directional control law and roll control law are developed using gain scheduling approach. Nose wheel steering, differential brake and rudder are used as the primary directional control device at low, medium and high speeds, respectively, according to both the qualitative and quantitative analysis of their control effectiveness at different speeds. A priority matrix is developed to determine the secondary control device which is used if the primary control device fails, thus the directional control system can have a certain degree of fault tolerance.FindingsThis work developed the directional control law and roll control law by using gain scheduling approach. Experimental results verified that the developed directional and roll control system has high robustness and satisfactory fault tolerance: it can guarantee a safe takeoff under a 50 ft/sec crosswind, even if one directional control device fails, which satisfies the relevant criteria in MIL‐HDBK‐1797.Practical implicationsThe directional and roll control system developed can be easily applied to practice and can steer the UCAV during takeoff roll safely, which will considerably increase the autonomy of the UCAV.Originality/valueThe paper shows how time‐scale decomposition technique is employed to extract the approximate directional model and roll model, which simplifies model analysis and control law design. A fault‐tolerant directional control system is designed to improve safety during takeoff.

Development of a flight dynamics model of a small unmanned airship

The scientific community has a renewed interest in airships owing to their potential applications in various tasks. The small unmanned airships are often used for inspection and environmental monitoring missions at low altitude. In this paper we introduce a study of two possible tail configurations of the unmanned airship AIUX15, arranged without ballast and ballonets and provided with an electric engine. We developed Matlab/Simulink models to simulate the dynamic behavior of two airship configurations. One of the goals of this research was to conduct an analysis of the feedback control laws for the 6-degrees-of-freedom model, which is linearized around the operational trim conditions. The controller gains were determined according to the pole-placement method. The closed-loop flight control was achieved by means of the state–space approach, to limit the oscillatory rolling motions induced by the rudder deflections.

Numerical Investigation of Flow-Induced Vibration of a Cantilever Beam for a Piezoelectric Energy Harvester

Flexible cantilever beams in channel flow loses its stability through a flutter mechanism at sufficiently high Reynolds number. This sustained transfer of flow work to cantilever beam oscillation could be extracted to generate electrical power, which may be utilized to power wireless sensors for structural health monitoring or supply additional power in unmanned or micro air vehicles. Such flexible beam system is known to exhibit some form of hysteresis, with super- and sub-critical velocities for onset of flutter, which may not be captured by current potential flow modeling. We present numerical simulation of a viscous, Navier-Stokes solver coupled to a cantilever beam, to capture this flutter velocity hysteresis. Numerical result under a linearly varying flow velocity shows an approximately 11% hysteresis, suggesting potential of present model for identifying more accurate boundaries of beam flutter. The prediction of cantilevered piezoelectric beam response under varying or unsteady flow velocities is necessary for reliable design of energy harvesting devices and warrants further experimental investigations.