Miniature Air Vehicles Research Articles

COMPARATIVE ANALYSIS OF AIRFOIL SELECTION FOR MINIATURE AIR VEHICLE

This article outlines factors to take into account when choosing an MAV airfoil (Miniature Air Vehicle). A MAV is mostly used in hazardous and defense regions that are inaccessible to humans. The MAV has some specified range of speed in which it has travel, i.e.: - 9 to 20m/s. Here, a few airfoils are chosen, and after doing a comparison analysis, the airfoil that produces the best results is chosen. The airfoil is chosen with a flat lower surface for comparative examination. In order to choose the right airfoil, "ANSYS FLUENT" is used to analyze the airfoil and calculate the lift to drag ratio. The reason for this criterion is that the MAV should have a stable flight. This article provides guidance on choosing the ideal airfoil for gliding. The airfoil with the maximum lift to drag ratio is being selected. According to the study of the data, NACA-2205 would be the ideal for MAV since it has a high lift to drag ratio at a high angle of attack and a high capability of gliding.

A Review of Bat-Inspired Shape Morphing Robotic Design

AbstractBy virtue of distinguished wing shape morphing characteristics, the unrivaled agility and flight maneuverability of bats have inspired scientists and engineers to develop novel forms of robots that can fly like bats. The unique wing conformations, flight kinematics, and aerodynamics offer significant advantages over the conventional form of miniature air vehicle in terms of quiet, safe operations, improved efficiency, and enhanced maneuverability. Meanwhile, they also pose substantial challenges for robot design from multiple perspectives, including mechanical design, sensing, control, etc. The practical benefits and technical bottleneck have motivated the development of bat-inspired robots in recent years. The purpose of this paper is to summarize the designing principles and report current state-of-the-art of bat-inspired robot designs, emphasizing the respective distinguishing features of each paradigm, along with the room for further improvement. Rather than showcasing advancement in wing materials, we will focus on the mechanical design and control methodology. This paper will help researchers new in this realm to get familiar with the bat-inspired robots by adopting features from existing designs. It also concludes technical challenges associated with future development, involving biological research, aerodynamic modeling, mechanical design, and control technique.

Curvature-constrained trajectory generation for waypoint following for miniature air vehicle

This paper addresses trajectory generation problem of a fixed-wing miniature air vehicle, constrained by bounded turn rate, to follow a given sequence of waypoints. An extremal path, named as γ-trajectory, that transitions between two consecutive waypoint segments (obtained by joining two waypoints in sequence) in a time-optimal fashion is obtained. This algorithm is also used to track the maximum portion of waypoint segments with the desired shortest distance between the trajectory and the associated waypoint. Subsequently, the proposed trajectory is compared with the existing transition trajectory in the literature to show better performance in several aspects. Another optimal path, named as loop trajectory, is developed for the purpose of tracking the waypoints as well as the entire waypoint segments. This paper also proposes algorithms to generate trajectories in the presence of steady wind to meet the same objective as that of no-wind case. Due to low computational burden and simplicity in the design procedure, these trajectory generation approaches are implementable in real time for miniature air vehicles.

Optimal Trajectory Generation for Convergence to a Rectilinear Path

This paper presents a strategy to determine the shortest path of a fixed-wing Miniature Air Vehicle (MAV), constrained by a bounded turning rate, to eventually fly along a given straight line, starting from an arbitrary but known initial position and orientation. Unlike the work available in the literature that solves the problem using the Pontryagin's Minimum Principle (PMP) the trajectory generation algorithm presented here considers a geometrical approach which is intuitive and easy to understand. This also computes the explicit solution for the length of the optimal path as a function of the initial configuration. Further, using a 6-DOF model of a MAV the generated optimal path is tracked by an autopilot consisting of proportional-integral-derivative (PID) controllers. The simulation results show the path generation and tracking for different cases.

New compliant strain gauges for self-sensing dynamic deformation of flapping wings on miniature air vehicles

Over the past several years there has been an increasing interest in the development of miniature air vehicles (MAVs) with flapping wings. To allow these MAVs to adjust to changes in wind direction and to maximize their efficiency, it is desirable to monitor the deformation of the wing during flight. This paper presents a step in this direction, demonstrating the measurement of strain on the surface of the wing using minimally invasive compliant piezoresistive sensors. The strain gauges consisted of latex mixed with electrically conducting exfoliated graphite, and they were applied by spray coating. To calibrate the gauges, both static and dynamic testing up to 10 Hz were performed using cantilever structures. In tension the static sensitivity was a linear 0.4 Ω με−1 and the gauge factor was 28; in compression, the gauge factor was −5. Although sensitivities in tension and compression differed by a factor of almost six, this was not reflected in the dynamic data, which followed the strain reversibly with little distortion. There was no attenuation with frequency, indicating a sufficiently small time constant for this application. The gauges were thin, compliant, and light enough to measure, without interference, deformations due to shape changes of the flexible wing associated with generating lift and thrust. During flapping the resistance closely tracked the generated thrust, measured on a test stand, with both signals tracing figure-8 loops as a function of wing position throughout each cycle.

Characterization of the Mechanics of Compliant Wing Designs for Flapping-Wing Miniature Air Vehicles

Flapping-wing miniature air vehicles (MAVs) offer multiple performance benefits relative to fixed-wing and rotary-wing MAVs. This investigation focused on the problem of designing compliant wings for a flapping-wing MAV where only the spar configuration was varied to achieve improved performance. Because the computational tools needed for identifying the optimal spar configuration for highly compliant wing designs have yet to be developed, a new experimental methodology was developed to explore the effects of spar configuration on the wing performance. This technique optically characterized the wing deformations associated with a given spar configuration and used a customized test stand for measuring lift and thrust loads on the wings during flapping. This revealed that spar configurations achieving large and stable deformed volume during the flapping cycle provided the best combination of lift and thrust. The approach also included a sensitivity and reproducibility analysis on potential spar configurations. Results indicated that the wing shape and corresponding lift and thrust performance were very sensitive to slight changes in volume and 3-D shape associated with slight variations in the spar locations.

A fractional order proportional integral controller for path following and trajectory tracking of miniature air vehicles

In this paper, a fractional order proportional-integral controller is developed for a miniature air vehicle for rectilinear path following and trajectory tracking. The controller is implemented by constructing a vector field surrounding the path to be followed, which is then used to generate course commands for the miniature air vehicle. The fractional order proportional-integral controller is simulated using the fundamentals of fractional calculus, and the results for this controller are compared with those obtained for a proportional controller and a proportional integral controller. In order to analyze the performance of the controllers, four performance metrics, namely (maximum) overshoot, control effort, settling time and integral of the timed absolute error cost, have been selected. A comparison of the nominal as well as the robust performances of these controllers indicates that the fractional order proportional-integral controller exhibits the best performance in terms of ITAE while showing comparable performances in all other aspects.

Time-Optimal Convergence to a Rectilinear Path in the Presence of Wind

This paper considers the problem of determining the time-optimal path of a fixed-wing Miniature Air Vehicle (MAV), in the presence of wind. The MAV, which is subject to a bounded turn rate, is required to eventually converge to a straight line starting from a known initial position and orientation. Earlier work in the literature uses Pontryagin's Minimum Principle (PMP) to solve this problem only for the no-wind case. In contrast, the present work uses a geometric approach to solve the problem completely in the presence of wind. In addition, it also shows how PMP can be used to partially solve the problem. Using a 6-DOF model of a MAV the generated optimal path is tracked by an autopilot consisting of proportional-integral-derivative (PID) controllers. The simulation results show the path generation and tracking for cases with steady and time-varying wind. Some issues on real-time path planning are also addressed.

Vision-Based Local-Level Frame Mapping and Planning in Spherical Coordinates for Miniature Air Vehicles

This paper presents a vision-based collision avoidance technique for small and miniature air vehicles (MAVs) using local-level frame mapping and planning in spherical coordinates. To explicitly address the obstacle initialization problem, the maps are parameterized using the inverse time-to-collision (TTC). Using bearing-only measurements, an extended Kalman filter is employed to estimate the inverse TTC, azimuth, and elevation to obstacles. Nonlinear observability analysis is used to derive conditions for the observability of the system. Based on these conditions, we design a path planning algorithm that simultaneously minimizes the uncertainties in state estimation while avoiding collisions with obstacles. The behavior of the planning algorithm is analyzed, and the characteristics of the environment in which the planning algorithm is guaranteed to generate collision-free paths for MAVs are described. Numerical results show that the proposed method is successful in solving the path planning problem for MAVs.

A vision-based collision avoidance technique for micro air vehicles using local-level frame mapping and path planning

This paper presents a vision-based collision avoidance technique for small and miniature air vehicles (MAVs) using local-level frame mapping and path planning. Using computer vision algorithms, a depth map that represents the range and bearing to obstacles is obtained. Based on the depth map, we estimate the range, azimuth to, and height of obstacles using an extended Kalman filter that takes into account the correlations between obstacles. We then construct maps in the local-level frame using cylindrical coordinates for three dimensional path planning and plan Dubins paths using the rapidly-exploring random tree algorithm. The behavior of our approach is analyzed and the characteristics of the environments where the local path planning technique guarantees collision-free paths and maneuvers the MAV to a specific goal region are described. Numerical results show the proposed technique is successful in solving path planning and multiple obstacle avoidance problems for fixed wing MAVs.

A Review of Bird-Inspired Flapping Wing Miniature Air Vehicle Designs

Physical and aerodynamic characteristics of a bird in flight offer benefits over typical propeller or rotor driven miniature air vehicle (MAV) locomotion designs in certain applications. A number of research groups and companies have developed flapping wing vehicles that attempt to harness these benefits. The purpose of this paper is to report different types of flapping wing miniature air vehicle designs and compare their salient characteristics. This paper is focused on mechanical design aspects of mechanisms and wings. The discussion presented will be limited to miniature-sized flapping wing air vehicles, defined as 10 to 100 g total weight. The discussion will be focused primarily on designs which have performed at least one successful test flight. This paper provides representative designs in each category, rather than providing a comprehensive listing of all existing designs. This paper will familiarize a newcomer to the field with existing designs and their distinguishing features. By studying existing designs, future designers will be able to adopt features from other successful designs. This paper also summarizes the design challenges associated with the further advancement of the field and deploying flapping wing vehicles in practice.

Nonholomic-like Corridor Navigation of a Quad-rotor MAV using Optical Flow

The paper presents initial results towards a reactive vision-based autonomous navigation within an indoor corridor performed by a quad-rotor miniature air vehicle (MAV). A model separation is proposed to simplify the control of the six-degrees-of-freedom (6DOF) dynamics of the flying robot. Such approach allows to deal with quad-rotor's 3D-motion through two subsystems: dynamic (altitude and MAV-relative forward velocity) and kinematic (nonholonomic navigation) subsystems. In terms of control, a hierarchical control scheme is used to stabilize dynamic and kinematic underactuaded subsystem involved in the navigation task. A Lyapunov-based bounded controller is used to stabilize the angular error dynamics. Furthermore, the corresponding stability analysis is presented to guarantee the asymptotical convergence of angular states to the origin. Promising simulations results shows the validity of the proposed control strategy since experimental values obtained from semi-automatic flight of quadrotor while navigating through an indoor corridor were used in such numerical evaluation.

Low-altitude road following using strap-down cameras on miniature air vehicles

This paper addresses the problem of autonomously maneuvering a miniature air vehicle (MAV) to follow a road using computer vision as the primary guidance sensor. We focus on low-altitude flight with the objective of maximizing the pixel density of the road in the image. The airframe is assumed to be a bank-to-turn fixed-wing MAV with a downward-looking strap-down camera. The road is identified in the image using HSV classification, flood-fill operations, and connected-component analysis. The main contribution of the paper is the derivation of explicit roll-angle and altitude-above-ground-level (AGL) constraints that guarantee that the road will remain in the footprint of the camera, assuming a flat earth. The effectiveness of our approach is demonstrated through high fidelity simulation and through flight results.

Vision-based navigation frame mapping and planning for collision avoidance for miniature air vehicles

This paper presents a vision-based navigation frame mapping and path planning technique for collision avoidance for Miniature Air Vehicles. A depth map that represents the range and bearing to obstacles is obtained by computer vision. Based on the depth map, an extended Kalman Filter is used to estimate the range and bearing. Using this information, a map, constructed in polar coordinates, is created in the navigation frame of the MAV. The Rapidly-exploring Random Tree algorithm is employed to find a collision-free path in the navigation frame. The proposed algorithm was successfully implemented in both simulation and flight tests.

Vision-Based Landing of Fixed-Wing Miniature Air Vehicles

This paper outlines a method for using vision-based feedback to land a miniature air vehicle accurately on a visually identifiable target of approximately known location. The method presented is robust to wind, capable of handling both stationary and moving targets, and capable of correcting for camera misalignment, state estimation biases, and parameter estimation biases. Landing results from actual flight tests are presented that demonstrate the effectiveness of the proposed method.

Inertially Aided Visual Odometry for Miniature Air Vehicles in GPS-denied Environments

Unmanned miniature air vehicles (MAVs) have recently become a focus of much research, due to their potential utility in a number of information gathering applications. MAVs currently carry inertial...

Stabilization of Video from Miniature Air Vehicles for Target Localization

Miniature air vehicles equipped with lightweight, inexpensive cameras have recently been employed in a greater variety of missions owing to their increased capability and relatively low cost. Unfortunately, miniature air vehicle video is often difficult to watch owing to high-frequency jitter caused by environmental disturbances such as wind gusts. This paper describes a methodology for producing real-time stabilized video by eliminating jitter.Video stabilizationisenabledbyestimatingtheintendedvideomotionthroughthemethodicalselection and tracking of image features from one frame to the next.The effectiveness of the video stabilizationroutineisdemonstratedinareal-worldsurveillancetaskoflocalizingstationary and moving targets on a mobile ground station. The paper also describes the unique mobile platformthatisusedtocreateandrefinetheseminiature-air-vehicle-specificcomputervision technologies.

Selection of engine type for Micro Air Vehicles. Turbojet or turboprop?

Interactive communication, airspace explorations, optical-electronic complexes for mini-satellites, planetary protection system devices, identification of heavenly bodies of "asteroid-comet danger" class, etc., this is just a short list of the currently emerging branches of science and engineering, in which challenges could be solved only given that you do apply Micro Air Vehicle (MAV), i.e., Miniature Air Vehicles (MAVs) (Miller, 2004; Akulov et al., 2004). At the same time, considering their aerodynamic characteristics (flight number Re, moment of inertia, flight mass, etc.) and their variations due to effects of the atmospheric turbulence, wind's perturbations, weather conditions, etc., MAV seems to be not quite equivalent to unmanned larger size AVs.

A vision-based autopilot for a miniature air vehicle: joint speed control and lateral obstacle avoidance

In our project on the autonomous guidance of Micro-Air Vehicles (MAVs) in confined indoor and outdoor environments, we have developed a vision based autopilot, with which a miniature hovercraft travels along a corridor by automatically controlling both its speed and its clearance from the walls. A hovercraft is an air vehicle endowed with natural roll and pitch stabilization characteristics, in which planar flight control systems can be developed conveniently. Our hovercraft is fully actuated by two rear and two lateral thrusters. It travels at a constant altitude (∼2 mm) and senses the environment by means of two lateral eyes that measure the right and left optic flows (OFs). The visuo-motor control system, which is called LORA III (Lateral Optic flow Regulation Autopilot, Mark III), is a dual OF regulator consisting of two intertwined feedback loops, each of which has its own OF set-point and controls the vehicle’s translation in one degree of freedom (surge or sway). Our computer-simulated experiments show that the hovercraft can navigate along a straight or tapered corridor at a relatively high speed (up to 1 m/s). It also reacts to any major step perturbations in the lateral OF (provided by a moving wall) and to any disturbances caused by a tapered corridor. The minimalistic visual system (comprised of only 4 pixels) suffices for the hovercraft to be able to control both its clearance from the walls and its forward speed jointly, without ever measuring speed and distance. The non-emissive visual sensors and the simple control system developed here are suitable for use on MAVs with a permissible avionic payload of only a few grams. This study also accounts quantitatively for previous ethological findings on honeybees flying freely in a straight or tapered corridor.

Experiments in Cooperative Timing for Miniature Air Vehicles

This paper presents experimental results for two cooperative timing missions carried out using a team of three miniature air vehicles (MAVs). Using a cooperative timing algorithm based on coordination functions and coordination variables, the MAV team executed a series of simultaneous arrival and cooperative fly-by missions. In the presence of significant wind disturbances,theaveragetimedifferencebetweenthefirstandlastvehicleinthesimultaneous arrival experiments was 1.6s. For the cooperative fly-by experiments, the average timing error between vehicle arrivals was 0.6s. These results demonstrate the practical feasibility of the cooperative timing approach.