Three-dimensional Flight Path Research Articles

An Accurate UAV 3-D Path Planning Method for Disaster Emergency Response Based on an Improved Multiobjective Swarm Intelligence Algorithm.

Planning a practical three-dimensional (3-D) flight path for unmanned aerial vehicles (UAVs) is a key challenge for the follow-up management and decision making in disaster emergency response. The ideal flight path is expected to balance the total flight path length and the terrain threat, to shorten the flight time and reduce the possibility of collision. However, in the traditional methods, the tradeoff between these concerns is difficult to achieve, and practical constraints are lacking in the optimized objective functions, which leads to inaccurate modeling. In addition, the traditional methods based on gradient optimization lack an accurate optimization capability in the complex multimodal objective space, resulting in a nonoptimal path. Thus, in this article, an accurate UAV 3-D path planning approach in accordance with an enhanced multiobjective swarm intelligence algorithm is proposed (APPMS). In the APPMS method, the path planning mission is converted into a multiobjective optimization task with multiple constraints, and the objectives based on the total flight path length and degree of terrain threat are simultaneously optimized. In addition, to obtain the optimal UAV 3-D flight path, an accurate swarm intelligence search approach based on improved ant colony optimization is introduced, which can improve the global and local search capabilities by using the preferred search direction and random neighborhood search mechanism. The effectiveness of the proposed APPMS method was demonstrated in three groups of simulated experiments with different degrees of terrain threat, and a real-data experiment with 3-D terrain data from an actual emergency situation.

High frequency social calls indicate food source defense in foraging Common pipistrelle bats

Social calls have the function to coordinate the behavior of animals. In the presence of conspecifics foraging Common pipistrelle bats (P. pipistrellus) emitted, in addition to typical echolocation signals, two types of social calls: complex social calls and an as-of-yet undescribed, short, frequency-modulated call type with high terminal frequency, which we term “high frequency social call”. By recording the flight and acoustic behavior of free flying pairs of foraging P. pipistrellus with an array of four microphones we were able to determine their three-dimensional flight paths and attribute emitted calls to particular behavioral situations. Complex social calls were emitted at further inter-individual distances and at large bearing angles to conspecifics, whereas high frequency social calls were produced at significantly shorter distances and at smaller bearing angles. These calls were associated with chasings and the eviction of the intruder. We assume that the emission of both types of social calls by foraging bats reflects a two-stage-process of the occupation and defense of a food patch. Common pipistrelle bats use complex social calls to claim a food patch and switch to agonistic behaviors, including chasings and high frequency social call emissions, when they defend their foraging territory against an intruder.

Three-Dimensional Localization of Bats: Visual and Acoustical

We introduce a multi-sensor array consisting of multiple microphones and a stereo-vision system that enables to track three-dimensional (3D) flight paths of bats. Field applicability is a major design factor which led to a portable battery powered system. Eight microphones form the acoustic array that allows the detection and localization of ultrasonic echolocation calls. Two near infrared sensitive cameras provide a visual identification of the three dimensional flight path. We minimized costs of this multi-sensor arrays by developing the system from ground up, including a novel acoustic signal recording and processing hardware. Our acoustic data acquisition system is the first to sample eight microphones simultaneously at 1MS/s/CH with 16 Bit resolution without the necessity of computers or laptops. All channels are processed in real time in the frequency and time domain to evaluate the occurrence of echolocation calls. Hereby, long term deployments of the system are achieved since only relevant signals are recorded. Parallel to the acoustic acquisition, the system records images of two near-infrared (IR) sensitive cameras at 12Hz frame rate each. Combined with IR illumination 3D flight paths can be extracted in post-processing. In addition, the system is able to log several environmental parameters, such as temperature and humidity. Recorded datasets can be associated with a global position and time-stamp through a GPS module and transformed to GPS coordinates with a three-axis accelerometer to determine the angle. The overall system (microphones, cameras, and sensors) was designed to be affordable, user-friendly, battery powered and without the necessity of an additional laptop.

130 대 소형 쿼드로터의 실외 자율 군집비행을 위한 좌표계 확장 및 실험

This article presents the extension of existing coordinate systems for autonomous swarming flight and subsequent experimental results using 130 mini quadrotors. The flight performance of mini quadrotors has been continuously improved in our laboratory, the Unmanned System Research Group (USRG). Mini quadrotors can fly autonomously using a GNSS-based navigation algorithm. We also extended the horizontal and equatorial coordinate systems to more easily generate a three-dimensional flight path, and these coordinate systems represent a powerful tool for the generation of flight paths and the improvement in flight quality. To confirm the effectiveness of the proposed coordinate systems, we assessed autonomous swarming flight using 130 mini quadrotors.

Prediction of microunmanned aerial vehicle flight behavior from two-dimensional intensity images

The increasing number of microunmanned aerial vehicles (MUAVs) is a rising risk for personal privacy and security of sensitive areas. Owing to the highly agile maneuverability and small cross section of the MUAV, effective countermeasures (CMs) are hard to deploy, especially when a certain temporal delay occurs between the localization and the CM effect. Here, a reliable prediction of the MUAV flight behavior can increase the effectiveness of CMs. We propose a pose estimation approach to derive the three-dimensional (3-D) flight path from a stream of two-dimensional intensity images. The pose estimation in a single image results in an estimation of the current position and orientation of the quadcopter in 3-D space. Combined with flight behavior model, this information is used to reconstruct the flight path and to predict the flight behavior of the MUAV. In our laboratory experiments, we obtained a standard deviation between 1 and 24 cm in a five-frame prediction of the 3-D position, depending in the actual flight behavior.

Path planning of plant protection UAV based on improved A* algorithm under wind conditions

In order to improve safety and reduce energy consumption, a path planning method for the transition of plant protection unmanned aerial vehicles (UAVs) in mountainous and hilly terrain between different plots based on improved A* algorithm was proposed. According to the height of three-dimensional terrain information, a raster voxel map was built. The search space was determined by assigning weights to each grid. The wind cost was introduced into the actual cost function to improve the algorithm. Different weight parameters were set for distance cost and wind cost. Simulation experiments were carried out in the fixed wind field and the variable wind field respectively to obtain the track length and flight time of path planning. The simulation results showed that compared with the classic A* algorithm, the improved A* algorithm could save 9.76%, 7.22% and 11.4% in trajectory, energy and time at the maximum under the condition of fixed wind. Under the condition of variable wind field, the maximum trajectory, energy and time saving percentage was 27.6%, 33.1% and 26.2% respectively compared with the classic A* algorithm. The proposed algorithm could effectively plan a safe and reliable three-dimensional flight path, which provided an effective method for better application of plant protection UAVs in complex hilly terrain. Keywords: A* algorithm; Path-planning; wind vector DOI: 10.33440/j.ijpaa.20200304.125 Citation: Sun G H, Fang X F, Zhu L C, Yuan Y W, Zhao B, Han Z H. Path planning of plant protection UAV based on improved A* algorithm under wind conditions. Int J Precis Agric Aviat, 2020; 3(4): 31–38.

Mission Performance Simulation of Integrated Helicopter–Engine Systems Using an Aeroelastic Rotor Model

This paper presents an integrated approach, targeting the comprehensive assessment of combined helicopter engine designs within designated operations. The developed methodology comprises a series of individual modeling theories, each applicable to a different aspect of helicopter flight dynamics and performance. These relate to rotor blade modal analysis, three-dimensional flight path definition, flight dynamics trim solution, aeroelasticity, and engine performance. The individual mathematical models are elaborately integrated within a numerical procedure, solving for the total mission fuel consumption. The overall simulation framework is applied to the performance analysis of the Aérospatiale SA330 helicopter within two generic, twin-engine medium helicopter missions. An extensive comparison with flight test data on main rotor trim controls, power requirements, and unsteady blade structural loads is presented. It is shown that, for the typical range of operating conditions encountered by modern twin-engine medium civil helicopters, the effect of operational altitude on fuel consumption is predominantly influenced by the corresponding effects induced on the engine rather than on airframe rotor performance. The implications associated with the implicit coupling between aircraft and engine performance are discussed in the context of mission analysis. The potential to comprehensively evaluate integrated helicopter engine systems within complete three-dimensional operations using modeling fidelity designated for main rotor design applications is demonstrated. The proposed method essentially constitutes an enabler in terms of focusing the rotorcraft design process on designated operation types rather than on specific sets of flight conditions.

Three-dimensional Route Planning for Unmanned Aerial Vehicles in a Risk Environment

This paper introduces a new approach for three-dimensional flight path optimization for unmanned aerial vehicles. It considers the performance of the air vehicle as well as mission specific requirements including the avoidance of no-fly areas, risk reduction in threat environments by terrain following flight or terrain masking low-level flight, and other regulations such as fixed release and approach vectors at the start and destination locations. The focus of the approach is on a proper discretization of the airspace by a network which allows the application of standard algorithms of combinatorial optimization. In contrast to conventional discretizations by grids or grid-like graphs, our network is non-regular since created by some random process. Moreover, each path in the network corresponds to a twice continuously differentiable trajectory which obeys the kinematic restrictions of the air vehicle and which is feasible with respect to the operational requirements of the mission. With suitable costs defined on the edges of the network, a minimum-cost path calculation allows to identify a trajectory of shortest length, shortest flight time, minimum flight height, or minimum visibility from the ground. The latter objectives aim to minimize the probability of being detected by hostile forces, hence increasing the survivability of the air vehicle.

Microphone-Array Tracking of Echolocating Bats Foraging in the Field

Microphone-Array Tracking of Echolocating Bats Foraging in the Field

How do tiger moths jam bat sonar?

The tiger moth Bertholdia trigona is the only animal in nature known to defend itself by jamming the sonar of its predators - bats. In this study we analyzed the three-dimensional flight paths and echolocation behavior of big brown bats (Eptesicus fuscus) attacking B. trigona in a flight room over seven consecutive nights to determine the acoustic mechanism of the sonar-jamming defense. Three mechanisms have been proposed: (1) the phantom echo hypothesis, which states that bats misinterpret moth clicks as echoes; (2) the ranging interference hypothesis, which states that moth clicks degrade the bats' precision in determining target distance; and (3) the masking hypothesis, which states that moth clicks mask the moth echoes entirely, making the moth temporarily invisible. On nights one and two of the experiment, the bats appeared startled by the clicks; however, on nights three through seven, the bats frequently missed their prey by a distance predicted by the ranging interference hypothesis (∼15-20 cm). Three-dimensional simulations show that bats did not avoid phantom targets, and the bats' ability to track clicking prey contradicts the predictions of the masking hypothesis. The moth clicks also forced the bats to reverse their stereotyped pattern of echolocation emissions during attack, even while bats continued pursuit of the moths. This likely further hinders the bats' ability to track prey. These results have implications for the evolution of sonar jamming in tiger moths, and we suggest evolutionary pathways by which sonar jamming may have evolved from other tiger moth defense mechanisms.

Echolocation and flight strategy of Japanese house bats during natural foraging, revealed by a microphone array system

Using only a microphone array system, echolocation pulses and three-dimensional flight paths in the frequency-modulated bat, Pipistrellus abramus, during natural foraging, were simultaneously examined. During the search phase, the inter-pulse interval, pulse duration, and moving distance of the bat between successive emissions were relatively constant at around 89.5 ± 18.7 ms, 6.90 ± 1.31 ms, and 0.50 ± 0.20 m, respectively. The bats started to decrease these acoustical parameters within 2-3 m of the prey capture point. For every emission along a flight path, the distance between a bat and its prey capture point was calculated as both direct distance to capture (DDC), which corresponded to the target distance, and flight distance to capture (FDC) along the flight path. The DDC matched the FDC after the start of the approach phase, indicating that foraging bats followed a straight-ahead path to the target. In addition, the duration of the quasi-constant frequency component of emitted pulses was slightly extended just before the convergence of the DDC with the FDC. These findings suggest that the bats confirm the presence of target prey by extending the duration of the pulse and then select a straight-ahead approach by forecasting the movement of the prey.

Adaptive behavior for texture discrimination by the free-flying big brown bat, Eptesicus fuscus

This study examined behavioral strategies for texture discrimination by echolocation in free-flying bats. Big brown bats, Eptesicus fuscus, were trained to discriminate a smooth 16 mm diameter object (S+) from a size-matched textured object (S-), both of which were tethered in random locations in a flight room. The bat's three-dimensional flight path was reconstructed using stereo images from high-speed video recordings, and the bat's sonar vocalizations were recorded for each trial and analyzed off-line. A microphone array permitted reconstruction of the sonar beam pattern, allowing us to study the bat's directional gaze and inspection of the objects. Bats learned the discrimination, but performance varied with S-. In acoustic studies of the objects, the S+ and S- stimuli were ensonified with frequency-modulated sonar pulses. Mean intensity differences between S+ and S- were within 4 dB. Performance data, combined with analyses of echo recordings, suggest that the big brown bat listens to changes in sound spectra from echo to echo to discriminate between objects. Bats adapted their sonar calls as they inspected the stimuli, and their sonar behavior resembled that of animals foraging for insects. Analysis of sonar beam-directing behavior in certain trials clearly showed that the bat sequentially inspected S+ and S-.

Active Listening for Spatial Orientation in a Complex Auditory Scene

To successfully negotiate a complex environment, an animal must control the timing of motor behaviors in coordination with dynamic sensory information. Here, we report on adaptive temporal control of vocal–motor behavior in an echolocating bat, Eptesicus fuscus, as it captured tethered insects close to background vegetation. Recordings of the bat's sonar vocalizations were synchronized with high-speed video images that were used to reconstruct the bat's three-dimensional flight path and the positions of target and vegetation. When the bat encountered the difficult task of taking insects as close as 10–20 cm from the vegetation, its behavior changed significantly from that under open room conditions. Its success rate decreased by about 50%, its time to initiate interception increased by a factor of ten, and its high repetition rate “terminal buzz” decreased in duration by a factor of three. Under all conditions, the bat produced prominent sonar “strobe groups,” clusters of echolocation pulses with stable intervals. In the final stages of insect capture, the bat produced strobe groups at a higher incidence when the insect was positioned near clutter. Strobe groups occurred at all phases of the wingbeat (and inferred respiration) cycle, challenging the hypothesis of strict synchronization between respiration and sound production in echolocating bats. The results of this study provide a clear demonstration of temporal vocal–motor control that directly impacts the signals used for perception.

Aviation emissions and abatement policies in the United States: a city-pair analysis

Due to the increasing demand for passenger travel, aircraft emissions that contribute to local and global air pollution are of rising concern. This paper presents a city-pair gravity model to project the domestic US passenger air traffic through 2030. Unlike previous research that considered traffic within disconnected flight segments, our model simulates air traffic between the true origin and the ultimate destination. Results from the city-pair model are then fed into a simplified three-dimensional flight path and emissions distribution model. We illustrate the usefulness of the model system through various scenarios. Based upon a reference case without any deliberate emission control, the model system is used to analyze the change in emissions resulting from three abatement policies: a more aggressive reduction in aircraft NO x emissions through advanced engine technology, the substitution of some short-distance air travel with high-speed rail in suitable corridors, and the replacement of the hub-and-spoke system with exclusively direct flight connections.

Assessing the aerodynamic effects of tail elongations in the house martin ( Delichon urbica ): implications for the initial selection pressures in hirundines

Of the three species of hirundine that breed sympatrically across the U.K., one, the barn swallow, has outer tail feathers elongated into streamers, whereas the other two species, the house martin and the sand martin, do not. The tail streamer of the barn swallow is regarded as a classic example of a sexually selected trait. Recent evidence, however, has suggested that streamers may have evolved largely through natural selection for enhanced flight performance and increased maneuverability. We tested the hypotheses that small streamers (1) increase performance in turning flight, but (2) decrease performance in flight variables related to velocity. We manipulated the lengths of house martin outer tail feathers and measured changes in their free-flight performance, using stereo-video to reconstruct the birds" three-dimensional flight paths. Five flight variables were found to best describe individual variation in flight performance. Of these five, the three variables determining maneuverability predicted that flight performance would be optimized by a 6- to 10-mm increase in the length of the outer tail feathers. In contrast, for mean velocity and mean acceleration, extension of the outer tail feathers appears to have a detrimental effect on flight performance. We suggest that the initial selection pressure for streamers in ancestral short-tailed "barn swallows" was via natural selection for increased maneuverability. In addition, we propose that the benefits of increased maneuverability have differed between hirundines in the past, such that the cost of increasing the length of the outer tail feather has, to date, outweighed the benefits of doing so in streamerless hirundines.

The effect of tail streamer length on aerodynamic performance in the barn swallow

The elongated tail of the male barn swallow (Hirundo rustica) is regarded as one of the classic examples of a male trait exaggerated by female choice. However, recently a hypothesis has been proposed suggesting that the streamers, or elongated outer tail feathers, may aid aerodynamic performance through the Norberg mechanism, providing lift at slow speeds and high angles of attack when the tail is fully spread. The possibility exists that the tail streamer has evolved under natural selection, sexual selection, or a combination of both selection pressures. We tested these three hypotheses by reducing the streamer length of free-flying swallows and measuring their aerodynamic performance, using stereo-video. Measurements of flight performance were made from the digitized three-dimensional flight paths. Five flight variables best described the individual variation in flight performance. Four of these five parameters—mean velocity, mean curvature, maximum agility, and mean rate change of curvature in the XY plane—had significant second-order polynomial relationships with tail streamer manipulation. The first and second principal components (from principal components analysis of the flight variables) also showed similar relationships with streamer manipulation. The combination of a curvilinear relationship between flight performance and streamer length and an aerodynamic optimum between 0 and 20 mm reduction is only predicted if both natural and sexual selection have been acting on streamer morphology. Our data therefore suggest that sexual selection has extended streamer length by around 10 mm beyond its aerodynamic optimum. We suggest that both natural and sexual selection have been important in shaping tail morphology in the barn swallow, and the relative importance of both selection pressures is discussed. Key words: barn swallows, flight performance, Hirundo rustica, maneuverability, natural selection, Norberg mechanism, sexual selection. [Behav Ecol 11: 228–238 (2000)]

Development of an automated fuzzy-logic-based expert system for unmanned landing

Fuzzy control is not just another buzzword nor is it a passing fashion in control theory, but a promising novel branch of control theory which can and should open up new vistas of applications. Applied fuzzy logic allows the design of knowledge-based controllers without requiring a precise model, it provides us with highly flexible and adjustable mechanisms, and may be very useful when accelerated development is required. Fuzzy logic provides approximate solutions to complicated control problems via the use of fuzzy rule base expert systems. This paper focusses on the nonlinear control actions of such a fuzzy controller (FC) operating effectively in the automated landing of unmanned aircrafts. The fuzzy controller controls successfully three-dimensional flight path, sink rate, and angular altitudes to allow safe landing of the unmanned aircraft. Applied fuzzy logic has been used to design a High SIQ (System Intelligent Quotient) mechanism which combines elements of human pilot intelligence with landing knowledge. The system was tested in simulations as well as in “real-life” landings in which performance demonstrate clearly significant potential of fuzzy logic, for the intelligent control of similar unmanned activities.

Numerical simulation of aircraft rotary aerodynamics

A potential-flow based panel method was used to compute the aerodynamic loads along a three-dimensional flight path. Comparisons were made with rotary rig tests of an airplane performing a coning motion and found to compare well with the main components of the aerodynamic forces. The effect of the sting-type wind tunnel mounting of the model on the measured loads was briefly investigated, and the possible benefits of using this method combined with wind tunnel experiments were highlighted.

The territorial flight of male houseflies (Fannia canicularis L.)

The three-dimensional flight paths of male Fannia canicularis underneath prominent indoor landmarks were filmed and reconstructed for analysis. The flies patrol well-defined airspaces (of about 50x50 cm horizontal, 25 cm vertical extent) underneath landmarks like lampshades. Their flight paths have a distinct structure: they fly straight for on average 400 ms and an average distance of 20 cm; they change flight direction by abruptly turning through on average 95° and continue to fly straight. the sign of changes in flight direction is kept constant for periods of 2–20 s and changed at irregular intervals. Male flies approach a landmark from below and, in the absence of other flies, settle to patrol an airspace close to the landmark. A second male approaching the same landmark chases, or is chased away by, the patrolling fly when it comes too close and may eventually settle to patrol 10–30 cm below the airspace occupied by the first fly. A dummy fly presented to a patrolling fly between the airspace he patrols and the landmark is vigorously attacked from below and prevents the fly from regaining his former patrolling station. By trapping flies on sticky ribbons suspended from the ceiling, which served as landmarks, it can be shown that males and females approach and land on landmarks. It is suggested that male flies establish a lek-type mating assembly underneath landmarks to intercept approaching females. The position of male patrolling stations relative to the landmark suggests that females might arrive at landmarks from the side (and not from below, as males do), thus crossing the dorsal visual field of patrolling males.

Minimum-fuel, three-dimensional flight paths for jet transports

A number of studies dealing with fuel minimization are concerned with three-dimensional flight. However, only Neuman and Kreindler (1982) consider cases involving commercial jet transports. In the latter study, only the climb-out and descent portions of complete long-range flight paths below 10,000 ft altitude have been investigated. The present investigation is concerned with the computation of minimum-fuel nonturning and turning flight paths for climb-outs from 2000 to 10,000 ft for long-range flights (greater than 50 n mi), and for complete flight paths of lengths between 5 and 50 n mi.