Rules to fly by: pigeons navigating horizontal obstacles limit steering by selecting gaps most aligned to their flight direction

Flying animals must successfully contend with obstacles in their natural environments. Inspired by the robust manoeuvring abilities of flying animals, unmanned aerial systems are being developed and tested to improve flight control through cluttered environments. We previously examined steering strategies that pigeons adopt to fly through an array of vertical obstacles (VOs). Modelling VO flight guidance revealed that pigeons steer towards larger visual gaps when making fast steering decisions. In the present experiments, we recorded three-dimensional flight kinematics of pigeons as they flew through randomized arrays of horizontal obstacles (HOs). We found that pigeons still decelerated upon approach but flew faster through a denser array of HOs compared with the VO array previously tested. Pigeons exhibited limited steering and chose gaps between obstacles most aligned to their immediate flight direction, in contrast to VO navigation that favoured widest gap steering. In addition, pigeons navigated past the HOs with more variable and decreased wing stroke span and adjusted their wing stroke plane to reduce contact with the obstacles. Variability in wing extension, stroke plane and wing stroke path was greater during HO flight. Pigeons also exhibited pronounced head movements when negotiating HOs, which potentially serve a visual function. These head-bobbing-like movements were most pronounced in the horizontal (flight direction) and vertical directions, consistent with engaging motion vision mechanisms for obstacle detection. These results show that pigeons exhibit a keen kinesthetic sense of their body and wings in relation to obstacles. Together with aerodynamic flapping flight mechanics that favours vertical manoeuvring, pigeons are able to navigate HOs using simple rules, with remarkable success.

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Head movements quadruple the range of speeds encoded by the insect motion vision system in hawkmoths

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2017.1622 ◽

2017 ◽

Vol 284 (1864) ◽

pp. 20171622 ◽

Cited By ~ 3

Author(s):

Shane P. Windsor ◽

Graham K. Taylor

Keyword(s):

Visual System ◽

Flight Control ◽

Vision System ◽

Head Movements ◽

Motion Vision ◽

Full Field ◽

Closed Loop Systems ◽

Spatial Frequencies ◽

Optokinetic Responses ◽

Self Motion

Flying insects use compensatory head movements to stabilize gaze. Like other optokinetic responses, these movements can reduce image displacement, motion and misalignment, and simplify the optic flow field. Because gaze is imperfectly stabilized in insects, we hypothesized that compensatory head movements serve to extend the range of velocities of self-motion that the visual system encodes. We tested this by measuring head movements in hawkmoths Hyles lineata responding to full-field visual stimuli of differing oscillation amplitudes, oscillation frequencies and spatial frequencies. We used frequency-domain system identification techniques to characterize the head's roll response, and simulated how this would have affected the output of the motion vision system, modelled as a computational array of Reichardt detectors. The moths' head movements were modulated to allow encoding of both fast and slow self-motion, effectively quadrupling the working range of the visual system for flight control. By using its own output to drive compensatory head movements, the motion vision system thereby works as an adaptive sensor, which will be especially beneficial in nocturnal species with inherently slow vision. Studies of the ecology of motion vision must therefore consider the tuning of motion-sensitive interneurons in the context of the closed-loop systems in which they function.

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Design of sliding mode flight control system for a flexible aircraft

Proceedings of the Institution of Mechanical Engineers Part G Journal of Aerospace Engineering ◽

10.1177/09544100211045592 ◽

2021 ◽

pp. 095441002110455

Author(s):

Majeed Mohamed ◽

Madhavan Gopakumar

Keyword(s):

Control System ◽

Rigid Body ◽

Flight Control ◽

High Speed ◽

Sliding Mode ◽

Flight Mechanics ◽

Frequency Separation ◽

Flight Control System ◽

Flexible Aircraft ◽

Aircraft Dynamics

The evolution of large transport aircraft is characterized by longer fuselages and larger wingspans, while efforts to decrease the structural weight reduce the structural stiffness. Both effects lead to more flexible aircraft structures with significant aeroelastic coupling between flight mechanics and structural dynamics, especially at high speed, high altitude cruise. The lesser frequency separation between rigid body and flexible modes of flexible aircraft results in a stronger interaction between the flight control system and its structural modes, with higher flexibility effects on aircraft dynamics. Therefore, the design of a flight control law based on the assumption that the aircraft dynamics are rigid is no longer valid for the flexible aircraft. This paper focuses on the design of a flight control system for flexible aircraft described in terms of a rigid body mode and four flexible body modes and whose parameters are assumed to be varying. In this paper, a conditional integral based sliding mode control (SMC) is used for robust tracking control of the pitch angle of the flexible aircraft. The performance of the proposed nonlinear flight control system has been shown through the numerical simulations of the flexible aircraft. Good transient and steady-state performance of a control system are also ensured without suffering from the drawback of control chattering in SMC.

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Robust Three-Dimensional Collision Avoidance for Fixed-Wing Unmanned Aerial Systems

AIAA Guidance, Navigation, and Control Conference ◽

10.2514/6.2015-1988 ◽

2015 ◽

Cited By ~ 2

Author(s):

Thomas J. Stastny ◽

Gonzalo Garcia ◽

Shahriar Keshmiri

Keyword(s):

Collision Avoidance ◽

Three Dimensional ◽

Unmanned Aerial Systems ◽

Aerial Systems

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A Moving Frame Trajectory Tracking Method of a Flying-Wing UAV Using the Differential Geometry

International Journal of Aerospace Engineering ◽

10.1155/2016/3406256 ◽

2016 ◽

Vol 2016 ◽

pp. 1-9 ◽

Cited By ~ 3

Author(s):

Yi Zhu ◽

Xin Chen ◽

Chuntao Li

Keyword(s):

Flight Control ◽

Trajectory Tracking ◽

Dimensional Space ◽

Three Dimensional ◽

Elliptic Cylinder ◽

Dynamic Equations ◽

Moving Frame ◽

Moving Frames ◽

Tracking Method ◽

Tracking Process

The problem of UAV trajectory tracking is a difficult issue for scholars and engineers, especially when the target curve is a complex curve in the three-dimensional space. In this paper, the coordinate frames during the tracking process are transformed to improve the tracking result. Firstly, the basic concepts of the moving frame are given. Secondly the transfer principles of various moving frames are formulated and the Bishop frame is selected as a final choice for its flexibility. Thirdly, the detailed dynamic equations of the moving frame tracking method are formulated. In simulation, a moving frame of an elliptic cylinder helix is formulated precisely. Then, the devised tracking method on the basis of the dynamic equations is tested in a complete flight control system with 6 DOF nonlinear equations of the UAV. The simulation result shows a satisfactory trajectory tracking performance so that the effectiveness and efficiency of the devised tracking method is proved.

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Postnatal Development of Three-Dimensional Head Movements in Spontaneously Behaving Unrestrained Rabbits

Three-Dimensional Kinematics of Eye, Head and Limb Movements ◽

10.1201/9780203735701-36 ◽

2020 ◽

pp. 297-302

Author(s):

Helmut Tegetmeyer

Keyword(s):

Postnatal Development ◽

Three Dimensional ◽

Head Movements

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Supervised Learning of Natural-Terrain Traversability with Synthetic 3D Laser Scans

Applied Sciences ◽

10.3390/app10031140 ◽

2020 ◽

Vol 10 (3) ◽

pp. 1140 ◽

Cited By ~ 4

Author(s):

Jorge L. Martínez ◽

Mariano Morán ◽

Jesús Morales ◽

Alfredo Robles ◽

Manuel Sánchez

Keyword(s):

Supervised Learning ◽

Autonomous Navigation ◽

Three Dimensional ◽

Point Clouds ◽

Natural Environments ◽

Good Prediction ◽

Ground Vehicles ◽

3D Point Clouds ◽

Natural Terrain ◽

Robotic Simulator

Autonomous navigation of ground vehicles on natural environments requires looking for traversable terrain continuously. This paper develops traversability classifiers for the three-dimensional (3D) point clouds acquired by the mobile robot Andabata on non-slippery solid ground. To this end, different supervised learning techniques from the Python library Scikit-learn are employed. Training and validation are performed with synthetic 3D laser scans that were labelled point by point automatically with the robotic simulator Gazebo. Good prediction results are obtained for most of the developed classifiers, which have also been tested successfully on real 3D laser scans acquired by Andabata in motion.

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Three-Dimensional Model of the Human Eye-Head Saccadic System

Journal of Neurophysiology ◽

10.1152/jn.1997.77.2.654 ◽

1997 ◽

Vol 77 (2) ◽

pp. 654-666 ◽

Cited By ~ 52

Author(s):

Douglas Tweed

Keyword(s):

Three Dimensional ◽

Head Movements ◽

Dimensional Model ◽

Three Dimensional Model ◽

Gaze Shifts ◽

One Dimensional ◽

Human Eye ◽

Saccadic System ◽

Listing's Law ◽

Listing’S Law

Tweed, Douglas. Three-dimensional model of the human eye-head saccadic system. J. Neurophysiol. 77: 654–666, 1997. Current theories of eye-head gaze shifts deal only with one-dimensional motion, and do not touch on three-dimensional (3-D) issues such as curvature and Donders' laws. I show that recent 3-D data can be explained by a model based on ideas that are well established from one-dimensional studies, with just one new assumption: that the eye is driven toward a 3-D orientation in space that has been chosen so that Listing's law of the eye in head will hold when the eye-head movement is complete. As in previous, one-dimensional models, the eye and head are feedback-guided and the commands specifying desired eye position eye pass through a neural “saturation” so as to stay within the effective oculomotor range. The model correctly predicts the complex, 3-D trajectories of the head, eye in space, and eye in head in a variety of saccade tasks. And when it moves repeatedly to the same target, varying the contributions of eye and head, the model lands in different eye-in-space positions, but these positions differ only in their cyclotorsion about the line of sight, so they all point that line at the target—a behavior also seen in real eye-head saccades. Between movements the model obeys Listing's law of the eye in head and Donders' law of the head on torso, but during certain gaze shifts involving large torsional head movements, it shows marked, 8° deviations from Listing's law. These deviations are the most important untested predictions of the theory. Their experimental refutation would sink the model, whereas confirmation would strongly support its central claim that the eye moves toward a 3-D position in space chosen to obey Listing's law and, therefore, that a Listing operator exists upstream from the eye pulse generator.

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Numerical Investigation on Flapping Aerodynamic Performance of Dragonfly Wings in Crosswind

International Journal of Aerospace Engineering ◽

10.1155/2020/7325154 ◽

2020 ◽

Vol 2020 ◽

pp. 1-14

Author(s):

Chao Wang ◽

Rui Zhang ◽

Chaoying Zhou ◽

Zhenzhong Sun

Keyword(s):

Stokes Equations ◽

Three Dimensional ◽

Lateral Force ◽

Aerodynamic Characteristics ◽

Navier Stokes ◽

Aerodynamic Forces ◽

Sideslip Angle ◽

Flight Direction ◽

Time Average ◽

Dragonfly Wings

Numerical simulations are performed to investigate the influence of crosswind on the aerodynamic characteristics of rigid dragonfly-like flapping wings through the solution of the three-dimensional unsteady Navier-Stokes equations. The aerodynamic forces, the moments, and the flow structures of four dragonfly wings are examined when the sideslip angle ϑ between the crosswind and the flight direction varied from 0o to 90o. The stability of the dragonfly model in crosswind is analyzed. The results show that the sideslip angle ϑ has a little effect on the total time-average lift force but significant influence on the total time-average thrust force, lateral force, and three-direction torques. An increase in the sideslip angle gives rise to a larger total time-average lateral force and yaw moment. These may accelerate the lateral skewing of the dragonfly, and the increased rolling and pitching moments will further aggravate the instability of the dragonfly model. The vorticities and reattached flow on the wings move laterally to one side due to the crosswind, and the pressure on wing surfaces is no longer symmetrical and hence, the balance between the aerodynamic forces of the wings on two sides is broken. The effects of the sideslip angle ϑ on each dragonfly wing are different, e.g., ϑ has a greater effect on the aerodynamic forces of the hind wings than those of the fore wings. When sensing a crosswind, it is optimal to control the two hind wings of the bionic dragonfly-like micro aerial vehicles.

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