NOTE: the new slot is on Thursdays (and no longer on Wednesdays) !
23.03.2023 14h00 CET Postponed!
Dr. Aimie Berger, ISM, Aix-Marseille Université
Title to be announced.
Abstract to be announced
**early 2023 CONFIRMED (date to be fixed)! Dr. Sebastian Büsse, Kiel University, Kiel, Germany Hunting with catapults: the predatory strike of the dragonfly (tentative title)
Abstract to be announced
Past talks
16.03.2023 14h00 CET
Dr. Lucia Bergantin, ISM, Aix-Marseille Université
In the hive, foraging honeybees inform their nestmates about the «location» of a food source by performing a waggle dance, which carries knowledge about the direction and «distance» to travel. Previous studies have suggested that the odometer (serving as a distance-meter) of flying honeybees assesses distance by mathematically integrating the raw angular velocity of the image sweeping backwards across their ventral viewfield, which is known as the translational optic flow. In aerial robotic applications, performing visual odometry onboard micro- and nano-drones is a particularly challenging task due to the low computational and perception resources available. Several winged insects, such as bees and butterflies, oscillate up and down while flying forward, adding an expansion and contraction component to their ventral optic flow vector field: this is the optic flow divergence. The question arises as to how raw integration of the optic flow (expressed in rad/s) could reliably encode a distance, since optic flow depends on the ground speed and the ground height. In this thesis, a model for the honeybee visual odometer, called SOFIa, is presented. The current ground height is estimated solely by means of an Extended Kalman Filter (EKF) and the optic flow divergence generated by the oscillating trajectory. The ground height estimate scales the translational optic flow, which is then mathematically integrated to obtain the distance travelled. By measuring the translational and divergence optic flow cues with optic flow sensors, the SOFIa visual odometer could be tested onboard a hexarotor both indoors and outdoors. A second model for the visual odometer (called SuRf) was also developed and tested in simulation. The SuRf visual odometer is also based on the scaling of the translational optic flow, but in this case, the optic flow taken into account is always perceived perpendicularly to the surface below. For this purpose, an active reorientation process was added so as to always keep the visual plane parallel to the ground below. The SuRf model improved the odometric performances obtained over uneven terrain in comparison with those of the raw SOFIa model. Modelling of the honeybee visual odometer using biologically plausible vision is therefore of great interest for two main reasons: (i) shed new light on the neuro-ethological processes at work in winged insects, and (ii) open the way to providing micro flying robots with minimalistic visual odometric equipment and abilities.
26.01.2022, 14h00 CET
Prof. Daniel Robert, University of Bristol, UK The bee, the flower and the Coulomb force
Exchanging nutrition for pollination services, bees and flowers interact relying on vision, olfaction, touch, and humidity sensing. Recently, we have discovered that bees can also detect and learn about the weak electric field that arises when they approach a flower. This electric field is generated because flying bees are usually electrically positively charged whilst flowers tend to be negatively charged. A third component contributes to this electric interaction, the atmospheric potential gradient (APG) that is a consequence of the ionization of the atmosphere and the global electric circuit. I will present our current understanding of this triadic interaction (Bee-Flower-APG), but also specifically discuss the role that triboelectrification may play in the sensory ecology of terrestrial arthropods and plants. I will show that physical contact and friction between insects and their environment can generate charge separation and a Coulomb force. It will be proposed that this triboelectric charging may play a role in the biology and sensory ecology of plants and insects. The enticing possibility that many arthropod species, beyond bees, are capable of electroreception will be briefly addressed and discussed.
19.01.2023 14h00 CET CONFIRMED (postponed from Dec 8) Prof. Basil el Jundi, Norwegian University of Science and Technology, Trondheim, Norway Unravelling the migratory compass of monarch butterflies.
Each fall, millions of monarch butterflies migrate over up to 5.000 km from North America and Canada to their overwintering habitat in the mountain ranges of Central Mexico. To maintain their direction, these butterflies rely on the sun as their main orientation reference. In my research group, we are interested in understanding how these fragile butterflies use the sun for orientation to maintain a directed migratory direction and how they master such a remarkable migration despite exhibiting a brain that is smaller than a grain of rice. We are studying the sun compass of monarch butterflies through behavioral and neuroanatomical techniques, as well as through electrophysiological approaches, such as multichannel tetrode recordings from tethered-flying butterflies. Our recent results show that the butterfly’s internal sun compass consists of head-direction neurons, steering neurons, as well as neurons that represent the animal’s goal direction. Together, these neurons establish a navigation network in brain that represents the animal’s current heading and the desired goal direction, generating steering commands whenever the butterfly deviates from its migratory course.
15.12.2022 14h00 CET CONFIRMED! Dr. Bardia Hejazi & Prof. Eberhard Bodenschatz, Max Planck Institute Dynamics and Self-Organization, Göttingen, Germany Honeybee flight in windy conditions
The study of bee flight and their collective behavior has been the focus of many studies that have offered us insight into how bees are able to fly and how they communicate with one another. However not much is known about honeybee fight dynamics in turbulent and windy conditions and how they manage to maneuver in such environments.
In this talk we will be presenting results from recent experiments performed to study honeybee flight and behavior in windy conditions in their natural habitat. We first present experiments where we use 3 GoPro cameras to track honeybees in three-dimensions (3D) during their flight to and from the hive. We create different turbulent conditions using fans and a mobile active grid, similar to one used in high Reynolds number wind tunnel experiments. We find that under the conditions investigated, honeybees seem to exhibit similar flight dynamics which are not dependent on the characteristics of the different flows they are exposed to. In flight, honeybees accelerate slowly and decelerate rapidly. While this behavior is observed in both calm and windy conditions, it is increasingly dominant in windy conditions where short straight trajectories are broken up by turns and increased maneuvering.
Additionally, we will present more recent work studying honeybee landing and takeoff dynamics near the hive entrance and their interactions with each other in different conditions.
01.12.2022 16h00 CET CONFIRMED!
Prof. Jon Harrison, Meghan Duell, Jordan Glass, Arizona State University, Tempe, USA Scaling and thermal effects on the energetics of insect flight
Body size and temperature are two dominant variables affecting animal flight performance and energetics, yet many basic questions remain about patterns and causes.
Among flying birds and larger insects (and runners), mechanical power output and energetic expenditure appear to show similar patterns with body mass, with power output scaling approximately isometrically (proportional to mass1), and metabolic rates scaling hypometrically (proportional to mass<1). This pattern may be due to lower frequencies of movement in larger species, and resultant lower costs of calcium cycling, as well as possibly improved elastic energy storage. However, in small insects, different patterns are observed. Stingless bees (Meliponini) are a speciose tribe of tropical and subtropical bees that vary in body mass from 1 mg to > 100 mg, and therefore provide an excellent model group for examining the scaling of flight kinematics and energetics across this relatively unexplored size range. My former Ph.D. student, Meghan Duell, spent multiple years in Panama studying the hovering flight of this group, with a bit of help from me. Body size has strong effects on body temperatures achieved during flight, with larger bees (over 50 mg) having flight muscle temperatures 10-13°C above air temperature, while thorax temperatures of smaller bees are 1-2°C above air temperature. Thorax mass scaled isometrically, but larger species have relatively smaller and narrower forewings (scaling slope of 0.5, significantly less than the isometric prediction of 0.67). In contrast to the hypometric scaling of flight metabolic rates shown for larger bees and birds, within these stingless bee species, flight metabolic rate scales strongly hypermetrically, with a scaling exponent of 2.25. This hypermetric scaling of flight metabolism cannot be explained by temperature differences among the species, as applying a Q10 correction of 2 only reduces the scaling slope to 2.1. In contrast to larger insects and birds, wing beat frequency is independent of mass, averaging 170 Hz. Regardless of body size, stingless bees voluntarily lifted and flew with nectar loads nearly equal to their body mass. Combining our data across all insects that have been measured to date, it appears that flight metabolic rate scales hypermetrically (scaling slope = 1.2) for insects less than 58 mg in body mass, and hypometrically (slope = 0.67) for larger insects. The causes of this biphasic pattern remain unknown, but the energetic benefits to small size may arise from reduced lift requirements at lower Reynolds numbers, relatively larger wings, and decreased wing venation.
An important question for understanding the effects of climatic warming on agriculture and biodiversity is how warming temperatures will affect the flight of insect pollinators. In stingless bees, both field body temperatures and the critical temperature that stops flight increases with body size. For smaller species, heat wave temperatures (up to 40°C) already exceed those at which bees can fly, suggesting that for these tropical species, with CTmax values ranging from 33 – 44°C, further climatic warming could strongly inhibit flight and foraging. Honey bees (Apis mellifera) are the most important agricultural pollinator, and are particularly well-adapted for heat, having a CTmax value of approximately 48°C. But, how does variation in air and body temperature affect flight metabolic rate and performance? Jordan Glass, a current Ph.D. student in my lab has recently used variable gas mixtures to create a “flight treadmill” and to vary body temperatures (heliox is more thermally conductive than nitrogen). At 35°C air temperature, thoracic temperature is little-affected by heliox, and flight metabolic rate increases about 1.4x until failure at a gas density below about 0.4 (relative to normal air density of about 1.3 kg m-3). However, at 23°C air temperature, thorax temperature and flight metabolic rate falls strongly as the fraction of heliox increases, and bees failed to hover at gas densities below 0.7, likely due to their inability to sustain flight muscle temperatures sufficient generate high power output. Honey bees show a classic thermal performance curve for maximal flight metabolic rate, with an optimal flight muscle temperature of 39°C, and an increase of about 2% per 1°C below the optimal temperature, and a decrease of about 5% per 1°C above the optimal. Nectar loading up to 60% of body mass increases thorax temperatures 2-4°C and flight metabolic rates by about 30% at air temperatures of 20°C and 30°C, but did not affect either parameter at an air temperature of 40°C, at which thorax temperatures are about 45°C. Bees prevent further overheating during flight at 40°C air temperatures by dramatically increasing water loss rates. The finding that bees can carry similar heavy loads at flight muscle temperatures of 45°C with 30% less cost suggests an as yet unidentified mechanism (Jordan is still analyzing the high speed videos) to increase efficiency. Supported partially by USDA 2022-67013-36285.
24.11.2022 14h00 CET CONFIRMED!
Prof. Andy Philippides, University of Sussex, UK Insect-inspired visual navigation: lessons from small brains
The use of visual information for navigation is a universal strategy for sighted animals, amongst whom desert ants are particular experts. Despite having brains of only a million neurons and low-resolution vision equivalent to a 1 kilobyte camera, desert ants learn long paths through complex terrain after travelling the paths once only. Such rapid learning with small brains is possible because learning is an active process scaffolded by innate behaviours which have co-evolved with the ant’s brain and sensory system to robustly solve the single task of navigation. In this talk, I will show that consideration of the innate behaviours that scaffold navigation has lead us to a model in which views specify actions not locations and in which route navigation is recast as a search for familiar views. This simplification means that the information needed to robustly navigate routes can be encoded by a single layer neural network after a single exposure to the training data, and that an ant can navigate home without recognising specific objects or locations nor knowing when it needs to learn.
17.11.2022 18h00 CETCONFIRMED! Prof. John S. Allen, University of Hawaiʻi , Mānoa, USA Experimental and Computational Investigation of Aero-Acoustics of Flying Beetles
The Coconut Rhino Beetle is an invasive species to Hawaii since 2013 and the goal of the State of Hawaii with funding from the US Department of Agriculture is eradicated the beetle. The beetle has few known predators in Hawaii and feeds upon the coconut palm trees. It has been cause of devastating effects on the palm trees in Guam stripping them of their leaves and resulting the loss significant amounts of vegetation. The impact on the agricultural and tourisms industries to Hawaii if the invasion unmitigated could result significant financial losses. The insect burrows in the ground during the day and is only active in flight making traditional detection and tracking methods of the dispersal patterns difficult to implement. Acoustic detection for ground activity and flight offer potential due to relative low cost and array gain. Moreover, tracking with close proximity to traps could provide additional information on navigation and flight techniques. Given that the flights of the large size Coconut Rhino Beetles for specific to foraging and feeding.
We are able to measure and analysis the time frequency characteristics of the chirp sounds which reveal an interesting, novel harmonic structure not reported previously. Thee sounds from flight due to wing beat are not well understood for this invasive species. The sounds of flapping wing insects are typically dominated by a fundamental with higher harmonics though the underlying structure and aero-acoustics beyond the frequency and amplitude are not well understood, especially for beetles. However, the aerodynamics and acoustics of invasive species of beetles are of interest in terms of fundamentals of flight and detection methods. The Coconut Rhinoceros Beetle (Oryctes rhinoceros) and the Oriental Flower Beetle (Protaetia orientalis) were studied during tethered flight with synchronized microphone array measurements and high speed video (1000-10,000 fps). The larger Coconut Rhinoceros Beetles have fundamental ~ 50 Hz with distinctive torsional wing rotation compared to Oriental Flower Beetle (~100 Hz). Computational fluid dynamics simulations were performed using the unsteady compressible flow solver (CAESIM, Adaptive Research, Inc.) using a high resolution (TVD) methodology. Models of the wing flapping motion were accomplished using mesh deformation techniques with the flapping following from rotation with prescribed bending and coupled rotation and translation from the wing’s hinge position. Fluid structure interaction with respect the wing’s flexibility are possible for extended experimental comparison.
13.04.2022 14h CET CONFIRMED! Prof. Barbara Webb, University of Edinburgh, UK Modelling locomotor dynamics in Drosophila larvae
The Drosophila larva is an important model system for understanding the interaction of neural circuits and body mechanics in directed locomotion. Its behaviour is often described as alternating between straight peristaltic crawling (runs) produced by a central pattern generator (CPG), and lateral bending to reorient (turns), either for random exploration or to move up or down a sensory gradient (taxis) by making appropriate ‘decisions’ when to switch. To better understand the control of motion we have developed a mathematical model of larval segmental mechanics, and show that (in the absence of damping and driving) the mechanics of the body produce axial travelling waves, lateral oscillations, and unpredictable, chaotic deformations. Adding a simple reflexive neuromuscular circuit to this model to counter friction gives rise to forward and backward peristalsis and turning, even though the nervous system has no CPG and neither senses nor drives bending motions. This produces life-like exploratory behaviour, and by adding a reflex to enhance bending in response to sensory input, we can produce directed taxis that closely resembles the observed behaviour of larvae in a sensory gradient.
30.03.2022 14h CET CONFIRMED! Prof. Karen Mulleners, EPFL, Lausanne, Switzerland Flying high and efficiently through parameter space.
Nature’s flapping wing fliers do not cease to amaze us with their incredible flight performance and efficiency. They automatically adapt their flapping motion kinematics to optimally fit varying flight conditions, which is a highly desirable ability for human-engineered devices. Yet, many experimental studies on flapping wing flight have focussed on simplified kinematics. In the first part of this talk, I will present our elegant automated experimental flapping wing mechanism that can recreate insect-like pitch angle kinematics and that allowed us to conduct a multi-objective optimisation of the pitch angle kinematics of a rigid flat plate wing. In the second part of the talk, I will introduce a novel bio-inspired membrane wing design that can passively deform and discuss results of a recent systematic experimental study of the fluid-structure interactions of our flapping membrane wings.
23.03.2022, 14h00 CET CONFIRMED! Dr. Arion Pons, Hebrew University of Jerusalem, Jerusalem, Israel Elasticity, Energy, and Nonlinear Resonance in Insects and FW-MAVs
Insect flapping-wing flight, alongside many other biological and biomimetic modes of locomotion, has a vibrational character: it is founded on patterns of periodic motion, in stark contrast to the non-periodic patterns utilised by artificial locomotive structures (e.g., propellors). As we try to analyse and understand this vibrational character, the phenomenon of resonance hovers uneasily in the background. Resonance offers the prospect of significant energy savings, and performance improvements, based on close tuning between frequency, elasticity, mass, and other structural properties; but details are cloudy, especially when exploring the complex nonlinearities present in real locomotive structures. In this talk, I will discuss how new theoretical results in nonlinear dynamics paint a new picture of the role of resonance in these vibrational modes of locomotion, with a particular focus on insect flight and flapping-wing micro-air-vehicles (FW-MAVs). These results challenge several core assumptions about how resonant systems behave. I will demonstrate i) how even simple vibrational locomotive systems have multiple different resonant states, motivating new approaches to the analysis of insect thoracic resonant properties; ii) how it is possible to access resonant states using only unidirectional actuation, motivating new designs of FW-MAV; and iii) how it is possible to deviate from the resonant frequency and still maintain resonant energetic optimality, motivating new interpretations for insect flight control behaviour. Together, these results provide new insight into the fundamental relationship between nonlinear resonance, elasticity, and energy in insects and FW-MAVs, and provide new qualitative and quantitative tools for the design and analysis of other forms of vibrational locomotive system.
09.03.2022 15h CET CONFIRMED!
Prof. Iain D. Couzin, Max Planck Institute of Animal Behavior, Konstanz, Germany Geometrical Principles of Decision-Making on the Move
A central challenge for animals when alone, or when grouping with others, is deciding where to go. Running, swimming, or flying through the world, animals are constantly making decisions while on the move—decisions that allow them to choose where to eat, where to hide, and with whom to associate. Despite this most studies have considered only on the outcome of, and time taken to make, decisions. Motion is, however, crucial in terms of how space is represented by organisms during spatial decision-making. Employing a range of new technologies, including automated tracking, computational reconstruction of sensory information, and immersive ‘holographic’ virtual reality (VR) experiments with fruit flies, locusts and zebrafish (representing aerial, terrestrial and aquatic locomotion, respectively), I will demonstrate that this time-varying representation results in the emergence of new and fundamental geometric principles that considerably impact effective decision-making. Specifically, we find that the brain spontaneously reduces multi-choice decisions into a series of abrupt (critical) binary decisions in space-time, a process that repeats until only one option—the one ultimately selected by the individual—remains. This mechanism facilitates highly effective decision-making, and is shown to be robust both to the number of options available, and to context, such as whether options are static (e.g. refuges) or mobile (e.g. other animals). In addition, we find evidence that the same geometric principles of decision-making occur across scales of biological organisation, from neural dynamics to animal collectives, suggesting they are fundamental features of spatiotemporal computation.
23.02.2022 14h CET CONFIRMED!
Dr. Ignazio Maria Viola, University of Edinburgh, Edinburgh, UK Aerodynamics of Plant Seeds
Pollen and seeds are dispersed by air, water or animals, allowing the plant to colonise new territories and ensure its survival. The most common dispersal mechanism is airborne. The diaspore, which include the seed, its protective fruit and some additional appendages, trade its potential energy to overcome the aerodynamic resistance of flying over a horizontal distance. This is efficiently done by gliding. Alternatively, diaspores might fall slowly and let the horizontal wind displace them. The dispersal can be substantially enhanced by turbulent updrafts, which lift diaspores by hundreds of metres, where the horizontal wind speed is higher and can disperse diaspores by hundreds of kilometres. In this talk, we discuss the aerodynamic strategies of four different diaspores to maximise their dispersal. The dandelion diaspore, for example, forms a filamentous disc-shaped surface of 90% porosity [1]. This allows the aerodynamic force to increase even higher than for an impervious disk, with only 1/10 of the mass. The maple diaspore is 70 times heavier than the dandelion’s and thus falls at a higher Reynolds number (Re > 1000), where filamentous wings are no longer efficient. Instead, it has a blade-like shape that autorotates while falling, effectively making a porous disk [2]. The Zelkova diaspore is comparable to that of the maple, but it includes dry leaves attached to a twig [3]. The dry leaves are light, resulting in a weight per unit area that is about half that of the maple and a comparable terminal velocity. Finally, the diaspore of the Javan cucumber, which is more than 300 times heavier of the dandelion, grows the largest and lightest wing per unit area known to all diaspores to glide long distances without wind [4]. The mass of these four diaspores ranges from less than one gram for that of the dandelion to hundreds of grams for that of alsomitra. Both range and endurance increase with Re, and we would expect that only the heaviest diaspore would adapt to glide. Yet, the Ulmus glabra also disperse by gliding and its mass is only few grams. This reminds us that our understanding of the morphological adaptations is still very limited, and aerodynamics itself is insufficient to fully understand them. Some areas of ongoing research on these diaspores include the transient condition before terminal velocity is reached, the unsteady flight in turbulence, and the effect of morphological changes during flight.
[1] Cummins et al., Nature 2018, 563:414-418.
[2] Lentink et al., Science 2009, 324:1438-1440.
[3] Certini et al., Am. J. Bot. 2020, 107(12):1-8.
[4] Azuma & Okuno, J. Theor. Biol. 1987, 129(3):236-275.
09.02.2022 16h CET CONFIRMED!
Prof. Amy Lang, University of Alabama, Tuscaloosa, USA Sharks and Butterflies: Micro-Sized Surfaces for Flow Control
Sharks and butterflies swim and fly in different flow regimes, yet the structure of their surfaces interacting with the surrounding fluid appear to both contain very important microscopic features that lead to reduced drag and increased flying or swimming efficiency. Sharks have moveable scales (on the order of 200 microns in size) that have been demonstrated to act as a passive, flow-actuated dynamic roughness for separation control. Water tunnel experiments with real shortfin mako shark skin samples mounted to models have shown significant control of flow separation in both laminar and turbulent boundary layer scenarios. Alternatively, butterfly scales (100 microns in size covering the wings in a roof shingle pattern) appear to fundamentally alter the local skin friction drag depending on flow orientation for what is dominantly a laminar boundary layer interacting with the wings. However, in this case the surface may also slow the growth and formation of the leading-edge vortex and these effects shown in experiments may help explain a mean decrease in climbing efficiency (joules per flap) of 32.2% for live butterflies once their scales were removed. An overview of these results will be presented bringing out the importance of finding solutions in nature for important engineering problems.
12.01.2022 15h CET CONFIRMED! Prof. David W. Murphy, University of South Florida, Tampa, USA Flapping flight in air and water: Bio-inspiration from tiny insects and sea butterflies
The flapping of wings is a common locomotion technique for tiny animals in both air and water. Insects flap their wings to fly in air, and zooplanktonic marine snails called sea butterflies flap wing-like appendages (called parapodia) to “fly” in water. Despite the thousand-fold difference in density between air and water, the flight systems of these very different animals show surprising similarities in how the wings move and in how they generate lift. These similarities point towards the possibility of designing a bio-inspired micro-aerial vehicle capable of aerial and aquatic flapping flight, but the fluid dynamics of such flight systems are not well understood. Here I describe our experimental efforts to understand these locomotion systems.
22.12.2021 15h CET CONFIRMED! Prof. Anne E. Staples, Virginia Tech, Blacksburg, USA Modeling circulation in a microfluidic insect wing replica.
Insect wings bend, twist, and deform during flapping flight. Distribution of hemolymph (insect blood) is needed for wing hydration and flexibility, sustaining living organs in the wing, and supplying active mechanosensing during flapping. Although insects possess a specific thoracic pump employed for driving hemolymph flow in the wing, the flapping frequency during flight (20-500 Hz) is much higher than that of thoracic pumping (1-3 Hz). How the nominally creeping (Re = 0.1) hemolymph flows in the wing are influenced by this high frequency flapping during flight is unknown. Using the North American grasshopper (Schistocerca americana), a dynamic flier with a complex wing vein network, we built a microfluidic flapping wing model to test hypotheses that flapping motions influence hemolymph circulation in a wing. The flapper was scaled up by a factor of 2.4x with a flow channel design that maintains dynamic similarity (Re = 0.1, Wo = 1.88), and printed using a stereolithography FormLabs Form 3 printer. The channels were seeded with dye droplets, sealed, and attached to a sinusoidal oscillator, and flapped at 3.45 Hz. Fluid movement was visualized in the channels using a high-speed camera (Photron Mini UX100) and analyzed. Preliminary results from these experiments will be shared.
15.12.2021 14h CET Prof. Olivier Thomas, Arts et Métiers Institute of Technology, Lille, France A fully flexible vibrating wing nano-drone: resonant concepts and results.
This talk will address the design of the smallest and lightest bio-inspired man-made nano air vehicle. It shows two main original characteristics. Firstly, it is made in polymer materials and built using micro-machining processes, enabling to easily obtain parts of only several micrometers, a span smaller than 30 mm and a mass of 20 mg. Secondly, it is composed of a fully compliant structure, with no hinges, leading to use special vibration theory concepts to create high amplitude vibrations of the wings with the right kinematics to produce lift. In particular, the distributed stiffness and inertia of the wings is designed and optimized such that two vibration modes are combined in a quadrature phase shift. The talk will address our results on the design of the structure, the wing kinematics characterisation and lift measurements, the modelling of the nonlinear damping brought by the fluid structure interaction between the vibrating wings and the surrounding air, and the numerical estimation of the lift force.
8.12.2021 14h CET Dr. Jong-Seob Han, TU Munich, Munich, GermanyLeading-edge vortex of flapping wings in freestream.
Leading-edge vortex (LEV) attachment on the wings of biological flyers is one key phenomenon explaining their superior aerodynamic performances and a high degree of aerial agility. Tremendous follow-up studies have revealed that the radial pressure gradient induced by the Coriolis acceleration, which is originally driven by the revolving/flapping motion of the wings, stabilizes the LEV with the spanwise flow. Complicated wingbeat kinematics, undulating surroundings, and unsteady wake vortex dynamics, however, have confined most of the studies to that in hover, despite the fact that staying particular point in space is very rare for most biological flyers and that an inflow during maneuvering would directly affect the LEV stability. This talk will deal with the LEV characteristics when it meets the inflow. The effect of a freestream on the LEV behavior will be dealt with, considering their sweptback angle and consequent spanwise flow. The effect of a steady lateral inflow on the LEV will also be discussed in conjunction with their flight stability.
20.10.2021, 14h00 CEST Victor Colognesi, UC Louvain, Louvain, Belgium Numerical simulation of bird flapping flight
Birds are capable of truly impressive performance. For example, the bar-tailed godwits migrate each year from Alaska to New Zealand in a 11000km journey without stopping nor feeding. Part of a project aiming at understanding how birds fly in organised formations, this work focuses on the simulation of a single bird and its wake. For this, coupled bio-mechanical and aerodynamic models have been coupled to represent accurately the dynamics of the wing and the evolution of the wake. Controllers have been designed to ensure the stability of the flight and enable manoeuvers of the simulated bird. The simulation framework allows an accurate representation of the wake of the bird, which can be analysed. Finally, we simulate the flight of a bird in the wake of another, where he is able to exploit the flow to save energy.
13.10.2021, 09h00 CEST Prof. Makoto Iima, Hiroshima University, Hiroshima, Japan Phase reduction technique on oscillating flows towards to analysis of flapping flight
Flying insects and swimming animals can be regarded as the limit cycles when dynamics of both wings/fins and fluid are considered. Phase reduction technique is a powerful tool to extract an essential dynamics around the limit cycles; it has been applied to many phenomena such as mechanical vibrations and circadian rhythms. However, applications to the incompressible fluid systems have been limited due to the high computational cost. In this seminar, I will discuss the techniques to overcome the difficulty and its applications to Kármán’s vortex streets as the first application of the phase reduction theory, and a flapping flight model.
06.10.2021, 14h00 CEST Prof. Eva Kanso, University of Southern California, Los Angeles, USA The Sea Star Bounce
Sea stars crawl and bounce using hundreds of tube feet that line their ventral surface. A tube foot is a soft muscular membrane, supported by a hydrostatic skeleton, that extends and contracts in response to local mechano-sensory cues. However, it is not clear how tube feet coordinate among each other to produce coherent locomotion and how they transition from crawling to bouncing. Here, I will present fascinating footage of the sea star bounce and briefly discuss the underlying biomechanics and neurophysiology. I will investigate the decentralized neuronal control of sea star locomotion in a mathematical model that accounts for distributed sensing and actuation at the tube feet level. I will show that symmetry-breaking leading to coherent and robust locomotion can emerge spontaneously from mechanical coupling between the tube feet, and that gait transitions can be predicted from tube feet activity. I will comment on the utility of this system to robotic applications that use distributed arrays of smart soft actuators.
22.09.2021, 16h00 CEST Prof. Mark Jankauski, Montana State University, USA Dynamics and Vibrations of Flapping Wing Insects
The specialized morphology of flying insects enables them to locomote with minimal energetic and cognitive demands. As a result, insects serve as inspiration for a variety of cutting-edge engineering technologies such as micro robotic systems and energy harvesting devices. Although research efforts have advanced the understanding of insect dynamics over the past decade, many of the mechanisms employed by small-scale biological fliers remain poorly understood. In this talk, I will highlight recent work conducted by the Montana State University Bio-Inspired Dynamics Laboratory to characterize the component-level dynamics of the insect flight mechanism. I will discuss advances in the aeroelastic modeling of flexible wings and demonstrate how wing flexibility augments flight performance. I will present recent experimental studies that characterize the vibratory properties of the insect thorax in-vivo and ex-vivo and show how these properties vary across insect species. The long-term objective of this research is to synthesize component models into a holistic system-level model of the insect flight mechanism.
15.09.2021, 14h00 CEST Prof. Long Chen, Northeastern University, Shenyang, China Leading-edge Vortex Formation and Stability: A Vorticity Transport Perspective.
Flying insects are excellent micro flyers in nature, considering their tiny bodies, stable hovering, and agile maneuvers. Evidence has shown that the formation and stable attachment of leading-edge vortex (LEV) on their wings are beneficial to the strong lift generation and the revolving motion of the wing leads to unique three-dimensional (3D) effects that benefit the LEV stability. Several hypotheses have been presented to account for the formation of a stable LEV. Alternatively, our work revisits the LEV dynamics from a vorticity transport perspective and two novel mechanisms that contribute to LEV stability are found, named the planetary vorticity tilting (PVT) and the radial-tangential vorticity balance (RTVB). Moreover, the role of Coriolis acceleration in LEV stability is explicitly explained. Previous hypotheses for LEV stability are also supported by our results and therefore we believe this vorticity-transport-based analysis may provide a universal explanation for LEV stability.
08.09.2021, 14h00 CEST Prof. Graham Taylor, Oxford University, Oxford, UK How are insect sensory systems matched to their flight mechanics?
Insects are richly equipped with sensors and actuators, so have a fundamentally different flight control architecture to today’s flying vehicles. But instead of complicating the computation that they require, this sensor-rich architecture actually appears to simplify it. What are its underlying organizational principles? How are the sensors matched to the stimuli they expect to receive in flapping flight? And how does this embodied intelligence aid motor control? Answering these questions is challenging, requiring measurements of the deforming wing kinematics of free-flying insects to identify their available control inputs, computational modelling of the aerodynamics to identify the mapping from kinematics to forces and moments, measurements of body inertial properties to identify the mapping from forces and moments to kinematics, electrophysiological recordings to estimate the mapping from kinematics to sensor output, and finally systems level modelling to put all of this together. Ideally, this modelling would also be expanded to include measurements of the mapping from muscle output to wing kinematics. In this talk, I will describe the long-term programme of research that has gone towards assembling this model and testing this hypothesis – from published work involving high-speed videogrammetry, aerodynamic modelling, and time-resolved synchrotron-based microtomography, through to new work using systems theory to identify the evolutionary design principles that underlie the sensor-rich flight control architecture of insects.
16.06.2021, 09h00 CEST (16h JST) Prof. Hiroto Tanaka, Tokyo Insitute of Technology, Tokyo, Japan Penguin-mimetic flapping-wing propulsion
Penguins have evolved to swim underwater. They are capable of high-speed foraging, agile maneuver, and deep diving by the flapping wings, that can be a promising model for biomimetic underwater robots in the future. The biomechanics and hydrodynamics studies of penguin swimming, however, are sparse to date, remaining the details of the propulsion mechanism unclear. In this talk, the first 3-D motion analysis of swimming penguins at an aquarium will be explained. Quasi-steady hydrodynamic calculation suggests that the wing deformation perhaps contribute to thrust generation. Then, an electric 3-DoF penguin-mimetic wing and its hydrodynamic experiment in a water tunnel will be demonstrated. By active control of each motion, magnitude and direction of the thrust largely change. The above biomimetic approach can contribute to both biology and engineering in swimming penguins.
09.06.2021, 14h00 CEST
Prof. Holk Cruse, Bielefeld University, Bielefeld, Germany neuroWalknet, a decentralized, context sensitive controller to explain insect walking
Legged locomotion comprises various tasks as are standing still, walking with different footfall patterns (or „gaits“), different velocities, forward or backward, negotiation of curves with different radii, dealing with disturbances, controlling stance, swing, and searching (and other behaviors as e.g. jumping or swimming). Here we show a controller for hexapod walking, neuroWalknet, that is considered part of a larger decentralized hierarchy, consisting of context sensitive local controllers being arranged at different levels of organization. neuroWalknet is able to describe and perhaps explain a large amount of behavioral data plus “behavior” of partly or fully deafferented animals, known e.g. from stick insect experiments. Although it has often been postulated that these behaviors are based on application of central pattern generators, our network shows that such elements are not necessary to explain the data. In contrast, not using CPGs may simplify its performance. Therefore, following Popper, we propose to endorse the simpler solution as best hypothesis.
02.06.2021, 14h00 Thomas Steinmann, CNRS and Université de Tours, Tours, France Singularity of the water strider propulsion mechanisms
Our understanding of animal locomotion in air and water has progressed considerably, based on studies of their wakes. Wake vortices are the hallmarks of momentum transfer and enable an inverse inference of the forces applied by animals. Such approach has recently been extended to locomotion at the air–water interface, focusing on the familiar water striders and their dual hallmarks, surface capillary waves and bulk water vortices, produced by their paddling legs. However, the principal mechanisms of propulsion used in this type of locomotion remain a matter of debate. We confirm that the main force driving propulsion is the capillary force resulting from surface tension, and that interface relaxation makes a major contribution to the increase in vorticity of the water bulk. There is therefore no one-to-one mapping between forces and hallmarks in the fluid. Locomotion at the air–water interface for animals with virtual oars much larger than the size of their legs thus requires specific treatment outside the existing framework based on immersed propulsive appendices.
12.05.2021, 14h00 Dr. Anna Stöckl, Würzburg University, Würzburg, Germany Flower tracking performance in hawkmoths – the role of sensory cues and wing damage.
The hawkmoth insect family is well known for their characteristic hovering flight, which they use to hover in front of flowers and suck nectar through their long proboscis. This intricate visuo-motor coordination is further challenged when the flowers move in the wind, forcing hawkmoths to track their movements in the air to keep their proboscis in the nectary. In my talk, I will highlight two sets of recent experimental results that shed light on the parameters vital to this behaviour: the sensory inputs required to accurately track the flower position and own body movements, as well as the integrity of their wings.
28.04.2021, 14h00
Prof. Volker Dürr, Biological Cybernetics, Faculty of Biology and Centre for Cognitive Interaction Technology (CITEC), Bielefeld University, Bielefeld, Germany Flexibility of insect walking behaviour: the significance of body posture and spatial coordination
A key feature of natural locomotion behaviour of animals is the flexible use of limbs according to their prevalent goals and needs. While it is reasonable to assume that the neural mechanisms underlying the control of locomotion are fairly similar within a given taxon – say, among insects – the behavioural requirements on locomotion control vary strongly, e.g., for biomechanical, ecological or contextual reasons. In my talk I will focus on how terrestrial locomotion is affected by body posture and the concurrent interaction between the limbs and the substrate. I will argue that spatial coordination of limbs may often be more important than temporal coordination.
Assuming that much of the movement repertoire of an animal is not pre-programmed (not even in insects), the ability to coordinate limbs in an adaptive, state- and context-dependent manner requires the integration of sensory information about posture, touch and interaction forces between the body and the substrate. Using stick insects as an example, I will discuss experimental evidence on distinct step classes, load dependent coordination, and the transfer of spatial information among limbs to demonstrate how both intra- and inter-leg coordination depend on load, grip, limb posture and/or contact events. With regard to the control of whole-body posture, I will also discuss the requirements of an internal representation of space in insects and its relevance for flexible motor behaviour.
14.04.2021, 09h00 CET (15h HKT) Xiaohui Liu, Department of Mechanical and Aerospace Engineering, The Hong Kong University of Science and Technology, Hong Kong Special Administrative Region of China Aerodynamics of dragonfly flight: impact of wing kinematics and morphology
Micro air vehicles (MAVs) are operated in the size region under the same environmental conditions as natural flyers. Insects are a good teacher for bioinspired designs of MAVs, and dragonflies are highly aerobatic insects having high aspect ratio wings in tandem. The forewing and the hindwing of a dragonfly have different geometry that could be an evolutionary specialization for better aerodynamic performance via sophisticated wing pitch control. Firstly, the dragonfly wing surface structure is reconstructed with FTP, and the wing deformation under two different wing speed are measured. It shows that dragonfly wing is corrugated over the whole surface, especially in the root and leading-edge region. Compare with forewing, the hindwing is easier to occur chord deformation due to larger chord length. Secondly, we measured the flow around the flapping wings using time-resolved particle image velocimetry (TR-PIV) to investigate the consequences of shape and the pitching mechanisms of the wings on the aerodynamics of dragonflies. The flow fields and pitching angle variations of the naturally actuated wing of the dragonfly were compared with that of the same wing artificially actuated only by flapping motion. We found that the trailing edge vortex dynamics and the wake were affected by the wing shape only for the in-vivo experiment with muscle induced pitching. Under the in-vivo with muscle induced pitching, the hindwing took more part in generating horizontal momentum with larger pitching magnitude, due to the larger chord length compared with forewing. Meanwhile, when there was only pitching due to the wing membrane deformation of artificially actuated flapping, a slight difference in the surrounding flow structures was found between the hindwing and the forewing, and the net flow in one period was reduced nearly to zero. Thirdly, we measured the kinematic parameters of the wings in two different flight modes (normal flight mode (NFM) and escape flight mode (EFM)). When the specimens switched from normal to escape mode the flapping frequency was invariant, but the stroke plane of the wings was more horizontally inclined. The flapping of both wings was adjusted to be more ventral with a change of the pitching angle that resulted in a larger angle of attack during downstroke and smaller during upstroke to affect the flow directions and the added mass effect. Noticeably, the phasing between the fore and hind pair of wings varies between two flight modes. It is found that the momentum stream in the wake of EFM is qualitatively different from that in NFM. The change of the stroke plane angle and the varied pitching angle of the wings diverts the momentum downwards, while the smaller flapping amplitude and less phase difference between the wings compresses the momentum stream.
24.03.2021 14 CET
Dr. Hung Truong, Aix-Marseille University, Marseille, France
Aerodynamics of insect flight and modelling of wing flexibility
Insects have fascinated a large, interdisciplinary community of engineers, biologists, physicists and mathematicians for a long time with their extraordinary capabilities of flying by flapping their wings. Insect flight has been extensively studied in the past assuming that insects fly with rigid wings in quiescent flow conditions. In the real world, however, most insect wings are complex structures that consist of a thin, flexible membrane supported by a network of veins. The aim of this project is to investigate the influence of wing flexibility on the aerodynamic performance of insects. For this purpose, a wing model has been developed using a mass-spring system where the wing is discretized by mass points connected by springs. Based on different mechanical behaviors, veins are modeled as a rod using extension and bending springs while membranes are modeled as a thin sheet using extension springs only. This functional approach allows us to mimic the distinctive structure and dynamics of insect wings. The wing model is then coupled with a fluid solver which is based on a spectral discretization of the three-dimensional penalized Navier–Stokes equations. The code is designed to run on massively parallel supercomputers for high-resolution computations. After being validated with respect to previous works, the code is firstly employed to simulate a tethered bumblebee with flexible wings. In order to analyze the effect of wing flexibility, the Young’s modulus of wing cuticle is varied to make a comparison between two different wing models that we refer to as flexible and highly flexible. We then examine a second species which is Calliphora vomitoria (blowfly) in a tethered flight context. Using covariance matrix adaptation evolution strategy, the wing stiffness is optimized by comparing the wing model with a set of experimental data of wing deformation in response to static point forces. Our studies show that wing flexibility plays an important role in minimizing flight energetic cost. Moreover, the wing inertia also helped to damp out the fluctuation of the aerodynamic force and thus stabilized the insect during flight.
10.03.2021 14h CET Prof. Harald Wolf, Ulm University, Ulm, Germany Navigation in desert ants : odometry and path integration
Desert ants of the genus Cataglyphis navigate back to their nests after foraging trips by means of path integration (as do many central place foragers, from social isopods to wolves). A brief review of this navigation strategy shall be provided, including experimental strategies to study ant navigation. A focus is on distance measurement, or odometry, (rather than on the well-studied compass mechanisms that include sun, polarisation, and spectral gradient compasses). The ants use two odometer mechanisms, stride integration and optic flow integration. Interaction of these two odometers and potential neuronal mechanisms shall be discussed.Differences in the search performances of sibling Cataglyphis species dwelling in habitats with different walking substrates may be related to accuracy limitations of the stride integrator. The above findings highlight biological principles for solving computational problems: typical solutions appear to rely on manageable approximations and calibration through learning rather than on mathematically exact calculations.
24.02.2021 16h CET / 8am MST (Mountain Standard Time) Prof. Laura Miller, University of Arizona, Tucson, Arizona, USA Using computational fluid dynamics to understand jellyfish swimming and feeding
Recent advancements in computational fluid dynamics have enabled researchers to efficiently explore problems that involve moving elastic boundaries immersed in fluids for problems such as cardiac fluid dynamics and animal swimming. These advances have also made modeling both nutrient exchange in a fluid and the muscle-driven motion of a flexible organ or organism through a fluid feasible. The work presented here focuses on the development and implementation of such methods and models for the pumping and pulsation of jellyfish bells used for swimming and feeding. We leverage existing computational algorithms for fluid-structure interactions and extend this technology to “living” boundaries. The models are used to reveal the role of resonance in jellyfish swimming and turning swimming and the effect of porous boundaries on particle capture.
10.02.2021, 14h00 CET Mourad Jaffar-Bandjee, Université de Tours, Tours, France Odor capture by pectinate antennae
In some moth species, male adults possess pectinate antennae which detect sexual pheromones emitted by females. A critical step in the olfaction process is the capture of pheromone molecules which depends heavily on the shape of the antenna. Pectinate antennae are however difficult to study because they are multi-scale objects spanning over four orders of sizes, depending on the structural elements. We focused on the species Samia cynthia and split its antenna in two levels, the macro- and the microstructures, and studied them separately. In both cases, we used Additive Manufacturing to build artificial scaled up models and Particle Image Velocimetry to determine their respective leakiness, the proportion of flow deflected from an object. We then adapted a heat transport model to calculate the mass transport problem of pheromone capture by the microstructure. Using FEM simulations, we combined the two levels and determined the capture efficiency of the entire antenna. We compared it with a cylindrical one and showed that a pectinate antenna is a good design to increase the surface of the antenna without significantly decreasing the capture efficiency.
03.02.2021, 10h00 CET Dr. Shantanu Bhat, University of Adelaide, Australia An alternate length scale for the Reynolds- and Rossby numbers in the context of insect wings
A stable leading-edge vortex formed over a rotating or flapping insect-like wing is known to be a primary reason behind an extra lift acting on the wing. Inspired from earlier studies at high Reynolds-number on the high aspect-ratio aircraft wings, the wing chord has been used as the reference length-scale, even for the insect-scaled wings. However, the flow structure on a typical low aspect-ratio insect wing is highly three-dimensional. As per the conventional scaling, this flow structure has been observed to be influenced by aspect ratio, Reynolds number, and Rossby number. Our work shows that the flow structure scales better with the wingspan, which we propose as the new reference scale in the context of insect wings. Use of this modified scaling for the Reynolds number and Rossby number decouples the effects of the aspect ratio. Interestingly, this also helps reconcile the apparently conflicting trends in the previous aspect-ratio studies on insect wings.
27.01.2021, 16h00 CET Prof. Dr. Kunihiko Taira, Mechanical and Aerospace Engineering, UCLA, USA Tackling the complex vortex dynamics around wings with simulation, modeling, and control
While the setup of a wing in freestream may appear simple, the flow generated in its wake exhibits remarkably rich dynamics. This is especially true for a finite-aspect-ratio wing at a post-stall angle of attack, which is often the wing of choice for birds, insects, and modern aircraft. The wing aspect ratio, angle of attack, sweep, Reynolds number, and Mach number (!) all uniquely contribute to the complex dynamics [1, 2, 3]. Although low-aspect-ratio wings are ever more prevalent in aeronautical designs, understanding of these flows is limited due to the vast parameter space. To gain fundamental insights into low-aspect-ratio wing flows at low Reynolds numbers, we computationally examine the importance of three-dimensional separation and wake behavior. Furthermore, a brief survey of our recent efforts to model and control these flows with modal analysis and data-driven techniques will be provided [4, 5, 6].
[1] K. Taira and T. Colonius, “Three-Dimensional Flows around Low-Aspect-Ratio Flat-Plate Wings at Low Reynolds Numbers,” Journal of Fluid Mechanics, 623, 187-207, 2009.
[2] K. Zhang, S. Hayostek, M. Amitay, W. He, V. Theofilis, and K. Taira, “On the Formation of Three-Dimensional Flows over Wings under Tip Effects,” Journal of Fluid Mechanics, 895, A9, 2020.
[3] K. Zhang, S. Hayostek, M. Amitay, A. Burtsev, V. Theofilis, and K. Taira, “Laminar Separated Flows over Finite-Aspect-Ratio Swept Wings,” Journal of Fluid Mechanics, 905, R1, 2020.
[4] A. M. Edstrand, Y. Sun, P. J. Schmid, K. Taira, and L. N. Cattafesta, “Active Attenuation of a Trailing Vortex Inspired by a Parabolized Stability Analysis,” Journal of Fluid Mechanics, 855, R2, 2018.
[5] K. Taira, M. S. Hemati, S. L. Brunton, Y. Sun, K. Duraisamy, S. Bagheri, S. T. M. Dawson, and C.-A. Yeh, “Modal Analysis of Fluid Flows: Applications and Outlook,” AIAA Journal, 58(3), 998-1022, 2020.
[6] A. G. Nair, C.-A. Yeh, E. Kaiser, B. R. Noack, S. L. Brunton, and K. Taira, “Cluster-Based Feedback Control of Turbulent Post-Stall Separated Flows,” Journal of Fluid Mechanics, 875, 345-375, 2019.
20.01.2021, 14h00 CET Stéphane Viollet, CNRS and Aix-Marseille Université, Marseille, France Aerial righting reflex in hoverflies and gravity perception
Recent studies carried out at our laboratory focused on gravity perception in hoverflies. Gravity perception in flying insects has mainly been studied in terms of grounded animals’ tactile orientation responses, but it has not yet been established whether hoverflies use gravity perception cues to detect a nearly weightless state at an early stage or even to stabilize their flight. Once dropped in free fall, hoverflies frequently initiated wingbeats but managed to avoid crashing only in variably structured visual environments [1]. We have also shown that the position of the lighting (overhead or bottom lighting) significantly affected both the stabilization rates and the time taken by the flies to stabilize [2]. Behavioural data have suggested that the vertical optic flow plays a key role in this anti-crash response. Free fall behavior analyses have also suggested that flying insect may not rely on graviception to stabilize their flight. Based on these two assumptions, we have developed a model which accounts for hoverflies ́ position and pitch orientation [3]. Finally, I will present results and model about the righting reflex in hoverflies. It was observed here for the first time [4] that hoverfly reorientation is entirely achieved within 6 wingbeats (48.8 ms) at angular roll velocities of up to 10×10^3 deg s−1. The fundamental role of the halteres will be discussed.
[1] R. Goulard, J-L. Vercher and S. Viollet (2016), To crash or not to crash: how do hoverflies cope with free-fall situations and weightlessness?, J. of Experimental Biology, vol. 219, 2497-2503.
[2] R. Goulard, A. Verbe, J-L. Vercher and S. Viollet (2018), Contribution of the Dorsal Light Response to freely falling hoverflies’ flight stabilization strategy, Biology Letters, 14: 20180051.
[3] R. Goulard, J-L. Vercher and S. Viollet (2018), Modeling visual-based pitch, lift and speed control strategies in hoverflies, PloS Computational Biology, 4(1): e1005894.
[4] A. Verbe, L. Varennes, J-L Vercher and S. Viollet (2020) How do hoverflies use their righting reflex?, J. of Experimental Biology, vol. 223:jeb215327.
16.12.2020, 14h00 CET Dr. Julien Serres, ISM (Institut des Sciences du Mouvement), Aix-Marseille Université Navigation possibilities without GPS or 5G: the AntBot solution
Autonomous navigation has become one of the major technological challenges of the 21st century because the need for robotic mobility is huge. Several outdoor location systems are now available: civil GNSS (Global Navigation Satellite System) with an accuracy of 5 m to 30 m depending on the weather and the environment, or GSM (Global System for Mobile communications) which self-localises using terrestrial networks by merging GSM and GNSS information. This can achieve an accuracy of 5 to 10 cm under optimal signal reception conditions. These technological solutions will work, but they also require significant energy due to radio emissions. Moreover, in the event of a blackout or service interruption, how will we guarantee the continuity of the localisation service? The solution lies in nature as many animals navigate with ease and precision without using such conventional systems. Bio-inspired solutions would allow navigation in the event of major faults in the GNSS and GSM networks. Directly inspired by the desert ant Cataglyphis fortis, the hexapod robot AntBot self-localises by counting its strides, measures its distance travelled from the integration of the visual scrolling of the ground and estimates its course using a celestial compass. AntBot repositions itself with an error of just 7 cm, almost 100 times lower than civil GNSS. AntBot’s celestial compass detects ultraviolet radiation scattered by the atmosphere. This compass is inspired by the dorsal part of the compound eyes of insects, and it only requires two photodiodes surmounted by linear rotary polarising filters that scan the sky dome. It thus measures the angle of polarisation of the light from the sky to provide the robot with a heading (accuracy: ~0.4°). The heading detection model is directly inspired by the polarisation vision used by insects. Although this biological model appears simple it is very interesting, due to its sensory parsimony, for developing bio-inspired instruments capable of providing directional information. The performance of this new bio-inspired navigation instrument attest to the innovative, reliable and robust nature of this optical compass for obtaining course information, and it is already the subject of research with industrial partners.
25.11.2020, 10h00 Ru Xu, Biomechanical Engineering Lab, Chiba University, Chiba, Japan Intermittent Control Strategy Can Enhance the Stabilization Robustness in Bumblebee Hovering
Active flight control plays a crucial role in stabilizing the body posture of insects to stay aloft under a complex natural environment. Insects can achieve a closed-loop flight control by integrating the external mechanical system and the internal working system through manipulating wing kinematics according to feedback information from multiple sensors. While studies of Proportional Derivative (PD) / Proportional Integral Derivative (PID)-based algorithms are the main subject to explore the continuous flight control mechanisms associated with insect flights, it is normally observed that insects achieve an intermittent spike firing in steering muscles to manipulate wings in flight control discontinuously. Here we proposed a novel intermittent control strategy for a 3 Degree of Freedom (DoF) pitch-control and explored its stabilization robustness in bumblebee hovering. An integrated computational model was established and validated, which comprises an insect-inspired dynamic flight simulator and a novel discrete feedback controller as well as a simplified free-flight dynamic model. We found that the intermittent control model can achieve an angular-dominant flight control, whereas the continuous control model corresponds to an angular-velocity-dominant one. Given the biological constraints in sensorimotor neurobiology and musculoskeletal mechanics, the intermittent control strategy was examined capable of enhancing the stabilization robustness in terms of sensory latency, stroke derivation, spike interval, and damping strength. Our results indicate that the intermittent control strategy is likely a sophisticated flight control mechanism in insect flights while providing a bioinspired flight-control design for insect size flapping-wing Micro Air Vehicles.
11.11.2020, 10h00 Dr. Sridhar Ravi, School of Engineering and Information Technology, UNSW Canberra at the Australian Defence Force Academy, Australia Visually guided strategies for flight through cluttered environments in insects
The natural habitat of insects that fly close to the Earth’s surface can be challenging to navigate. The terrain is seldom flat and unobstructed and instead it is complex, consisting of a plethora of natural and artificial features. Once airborne insects are likely to encounter obstacles in collision course and will be tasked with performing evasive manoeuvres. Insects are also small in size with tiny brains and thus, they are further constrained in the sensorimotor and neural apparatus that can be accommodated. Despite these challenges insects like bees display a remarkable ability to navigate through highly cluttered terrain. Several previous studies have revealed the significant role of vision and more specifically optic flow, in mediating navigation in unobstructed environments. In cluttered environments, the combination of stable sensing for obstacle detection and nimble manoeuvring for evasion poses unique challenges. In our study we presented bumblebees with various types of spatial clutter, from solitary obstacles to constellations, and sought further insights into their navigational “toolkit”. We analysed the finely resolved measurements of the head and body orientation of bees in free flight through the different environments that were also used to reconstruct the instantaneous visual field of the bees and estimate the optic flow in the different environments. In this talk I will present on how bees in free flight effectively decouple their sensing and motor systems and the salient cues used for performing canonical tasks such as obstacle detection and gap perception, and the manoeuvres performed for collision avoidance and navigating through tight spaces. Time permitting, I will also present on how bees also learn to avoid invisible obstacles.
Come along even if you are not into this stuff because there will be lots of cool highspeed videos!
28.10.2020, 14h00 Dr. Chandan Bose, Department of Aerospace and Mechanical Engineering, University of Liège, Belgium Dynamical Analysis of the Unsteady Flow Phenomena around a Flapping Wing
The present work deals with the transitional wake dynamics and nonlinear fluid-structure interaction behavior of flapping wings in the low Reynolds number regime through high-fidelity
numerical simulations. This talk is largely focused on identifying the dynamical transition routes to chaos in the unsteady flow-field of rigid and flexible flapping wings and unraveling the underlying flow-physics behind the chaotic transition. A quasi-periodic (QP) route is established in the near-field of a pitching-plunging airfoil as the dynamic plunge velocity (kh), proportionally the amplitude-based Strouhal number, is gradually increased. Further, it is observed that the QP state gets interspersed with intermittent bursts of aperiodicity preceding chaos. Following this, the role of near-field vortex interactions in making the unsteady flow-field transition from periodicity to chaos is investigated. A dynamic interlinking of the near and far-field wake transitions shows that the deflected jet undergoes a switching of direction at its far-end due to the propagation of the QP trigger from the nearfield. Eventually, this near-field QP state gets interspersed with aperiodic bursts which trigger the direction flipping of the immediate couple at the trailing-edge resulting in a full reversal of the deflection direction of the wake. Finally, the wake topology becomes chaotic through a series of rapid aperiodic jet-switching. A similar aperiodic transition is observed in the 3D flow-field beyond a considerably high value of kh. The underlying complex interactions among leading-edge, trailing-edge, and tip vortices are analyzed in detail with the aid of Qcriterion iso-surfaces. This study establishes that the transition to aperiodicity in the wake of a flapping wing is indeed a physical phenomenon and not an artefact of the 2D flow assumption. In order to understand the nonlinear FSI dynamics of flapping wings, the flow-induced vibration of a 2-DOF passively flapping airfoil is investigated at a low value of the structure-to-fluid added mass ratio. This flexibly mounted flapping system is seen to undergo a chaotic transition through a Ruelle-Takens-Newhouse (RTN) route. Nonlinear time series analysis techniques have been implemented to characterize the different dynamical states present in the course of transition and to establish the associated transition route to chaos.
21.10.2020, 14h00 Dr. Liang Li, Department of Collective Behaviour, Max Planck Institute of Animal Behavior, Konstanz, Germany Robotic fish: from bio-inspiration to bio-understanding
Robotic fish has drawn increasing attention in both constructions and applications. Scientists have constructed a large amount of robotic fish mimicking almost all underwater creatures, such as tuna, pike, boxfish etc. Most applications of these robotic fish are focused on how can we make an underwater vehicle endowed with a high swimming efficiency, great agility and surprising stealth. Few of them explored how can we take the robotic fish as a high fidelity physical model to help understand fish behaviour. In this talk, I will first introduce how we constructed the robotic fish, including the morphology, locomotion control, optimisations, and swarms. Following that, I will give an example to apply these robots to help understand group fish swimming behaviour. We make the robotic fish replicate the movements of the real fish or interact with the real fish to explore when and how fish make decisions. The results show that the robotic fish is one of the promising and powerful platforms to study collective fish behaviour.
14.10.2020, 14h00 Dr. Jorn Cheney, Royal Veterinary College, London, United Kingdom Avian-inspired flight suspension for small aircraft
Birds fly in extreme conditions that small, modern air vehicles cannot manage safely. They can compensate for gusts of similar magnitude to their flight speed. We studied how a gliding barn owl (Tyto alba) responded to upward gusts of varying intensity (peaking at 68% of the bird’s mean flight speed). Movements of the wing are too rapid to be prescribed by control inputs sent from the brain, and we explore a purely aeromechanical explanation that depends upon the spanwise distributions of mass and pressure, and possessing a hinged wing (shoulder). Inertial effects, rather than aerodynamic effects, dominate early gust rejection and stabilise the head and torso over a period that should allow the brain to interpret and respond to the gust. We implemented this bio-inspired mechanism into a passive glider that achieved similar gust-rejection performance as the barn owl.
07.10.2020, 14h00 Dr. Franck Ruffier, CNRS Senior Researcher, Aix-Marseille University Biorobotics : from motion vision to motion camouflage
A robot named ACEbot locate and follow a target (Colonnier et al. 2019), using the vibrating artificial compound eye called active CurvACE (Floreano et al. 2013; Colonnier et al. 2013). This visual sensor actively scans the environment at an imposed frequency (50 Hz) with an angular scanning amplitude of 4.2deg : it successfully locates a textured cylindrical target with hyperacuity, i.e. much finer resolution than the coarse inter-receptor angle of the artificial compound eye.In particular, ACEbot follow a target by localizing the right and left edges of the cylindrical target.
The ACEbot controller applies two simple control laws (Colonnier et al. 2019):
(i) maintaining the target at a precise gaze angle in the field of view by rotating only in yaw, and,
(ii) maintaining constant the measured subtended angle of the target by translating only forward or backward in the target direction.
ACEbot consistently achieved similar pursuit performances under various lighting conditions with a high level of repeatability. The robotic pursuit pattern mimicked finely the natural pursuit pattern of the female fly Syritta Pipens L. by the male (Collett & Land, 1975).
As an outcome, such a biomimetic visual tracking strategy limits the apparent movement that could have been detected by a target perceiving the visual movement. The resulting robotic behavior could be interpreted as the emergence of motion camouflage patterns.
23.09.2020, 14h00 Dr. Ramiro Godoy-Diana, PMMH, ESPCI Paris Fish and fish-like swimming interactions
The interaction between two neighbouring swimmers constitutes the fabric of the very rich collective dynamics that is observed in a fish school in nature. I will discuss different aspects of our recent work on swimmer interactions, where we have designed experiments with real fish or with simple robotic models, as well as numerical simulations, to examine the questions of swimmers synchronisation, pattern formation and energy expenditure, using the most basic interactions between a pair of neighboring swimmers.
16.09.2020, 14h00 Prof. Frédéric Boyer and Dr. Johann Hérault, IMT Atlantique, France Strategies of locomotion for anguilliform aquatic robots: from model-based control laws to bio-inspired complex network of oscillators
Since the 2000s, a new generation of marine robots inspired by eels and aquatic snakes has emerged in academic contexts. In this talk, we report different strategies to control the body actuation of aquatic slender robots thanks to the bio-inspired robots of our colleagues from biorob team (EPFL).
In the first part, we present a model-based approach for control (and simulation) of swimming elongated fish and robots. The approach is a prolongation of the Lighthill Large Amplitude Elongated Body Theory (LAEBT). The fish body is modeled as an internally actuated Cosserat beam in finite deformations,. The LAEBT is revisited from this point of view, from which the fluid around the fish can be seen as a fluid Cosserat beam sliding along the fish body. The partial differential equations of the fluid and the body dynamics are derived with standard Newton’s laws and illustrated through several applications in simulation and control.
In the second part, we study the emergence of locomotive gaits produced by decentralized control law based on distributed neural oscillators controlling the cyclic motion of the servomotors. This method aims to reproduce the activity of central pattern generators, which orchestrate the muscle coordination of vertebrate animals. We investigate the effect of hydrodynamical feedback on the network of oscillators. We show that the sensory feedback produces redundancy in the oscillators chain and that the control becomes robust to oscillator disruptions. Finally, we explain the role of the sensory feedback: it produces a frequency detuning along the spinal cord, which results in a constant phase lag in the chain thanks to the diffusive effect of the CPGs.
09.09.2020, 14h00 (2 Talks, each 20+10min)
M. Sc. Gianmarco Ducci, UC Louvain, Belgium Stability and Sensitivity Analysis of Bird Flight
Birds have been a source of inspiration for the scientific community for decades. Flight dynamics is one of the many fascinating aspects about bird flight, especially regarding their ability of reacting to environmental perturbations, to maintain straight trajectories despite wind, and to perform outstanding agile maneuvers.
We introduce a numerical framework aiming at identifying trimmed conditions, and quantifying the stability properties of flapping flight at the scale of migratory birds. Such framework builds upon the coupling of a quasi-steady morphing lifting line with a multiple-shooting algorithm.
The lifting line takes the wing kinematics as input, and calculates the aerodynamic loads at every time step acting on the actual position of the flapping wing.
The multiple-shooting algorithm detects the trimmed conditions (defined as limit cycles) and assess their stability via Floquet theory.
Results of this framework will be presented, and the impact of some relevant flight parameters, such as wingbeat amplitude and tail opening, will be discussed.
M. Sc. Henja-Niniane Wehmann, Rostock U, Germany Insect wing flexibility with an emphasis on flies
When flying, many insects perform complex flight behaviours using their wings. Insect wings are flexible body appendages and can bend and twist in flight. Their properties vary across different species, but overall there seem to be possible benefits of deformable over rigid wings. For certain configurations, flexible wings have been shown to be aerodynamically favourable, although in other experiments the opposite was found to be true.
In order to further investigate the areodynamic effects of flexibility, we plan to create a flexible fly wing model to be used in computational fluid dynamics simulations. As a biological basis for this model, we have conducted static stiffness measurements of fly wings by locally applying small point forces on wings fixed at the wing base. In this talk, I will present these experiments and their results. We found spring stiffnesses between ca. 0.02 to 1.0 N/m in fruit flies and ca. 0.2 and 2.8 N/m in blowflies. While the line between point of force application and wing base can be approximated as a cantilever beam for the small deformations induced in these experiments, the wing also shows deformation along other directions.
22.07.2020, 16h00 CEST Prof. Dr. Vivek Prakash, University of Miami Surprising tradeoffs and consequences of locomotion in simple, enigmatic marine animals
Animals are characterized by their movement, and their tissues are continuously subjected to dynamic force loading. The adaptive response and mechanics of tissues determine the ecological niches that can be endured by a living organism. In the first part of my talk, I will present our surprising discovery of locomotion-induced tissue fractures and healing in a simple, early divergent marine animal – the Trichoplax adhaerens. I will demonstrate how fracture mechanics governs dramatic shape changes and asexual reproduction in this animal.
In the second part of my talk, I will focus on the role of fluid mechanics in marine invertebrates. Many marine invertebrates have larval stages covered in linear arrays of beating cilia, which propel the animal while simultaneously entraining prey. In starfish larvae, we discovered that these ciliary arrays give rise to a beautiful pattern of slowly evolving vortices. I will elucidate how these vortices create a physical tradeoff between feeding and swimming in heterogeneous environments. For more information, please visit: www.marinebiophysics.org
15.07.2020, 14h00 Prof. Dr. Emily Baird, Stockholm University, Sweden Visually guided control of landing: Surprising lessons from bees
Landing is arguably one of the most difficult challenges facing any flying agent. Nonetheless, flying animals such as bees execute safe landings, sometimes over hundreds of times per day as they make repeated foraging trips between flowers and their hive. This is remarkable considering the miniature size of the brains and the sensory systems with which they do this. In this talk, I will present findings from studies investigating how landing is coordinated in different bee species, including some unexpected results that just go to show that there is always something to learn from the study of biolocomotion and biology in general!
08.07.2020, 10h00 Prof. Dr. Stanislav Gorb, Kiel University Fly Walking on the Ceiling: Animal Attachment Devices and Biologically-Inspired Reversible Adhesives
01.07.2020, 10h00 CEST ( 5pm local time ) Prof. Dr. Kosuke Suzuki, Department of Mechanical Systems Engineering, Shinshu University Numerical simulations of a butterfly-like flapping wing-body model: effects of wing planform, mass, and flexibility.
Butterflies have unique and interesting features compared with other insects. The most conspicuous example is their erratic trajectory and large variation in flight speed. This behavior suggests that butterflies have outstanding agility and maneuverability, which are attractive features in practical applications such as micro air vehicles (MAVs). It has been know that butterfly’s flight is far from hovering or steady forward flights and is longitudinally unstable. Therefore, in order to elaborately simulate the free-flying butterfly, we have to consider the interaction between the fluid motion, wing motion, body motion (translational and rotational), and attitude control. Instead of performing such an elaborate simulation, our research group has attempted to clarify the minimum configuration for reproducing the free-flying butterfly by using a simplified butterfly model, namely butterfly-like flapping wing-body model. This model is composed of two thin rigid wings and a rod-shaped body, and flaps its wings downward to generate lift force and backward to generate thrust force like an actual butterfly. It has been found that such a simple model can generate enough lift force to support an actual butterfly’s weight even in its free flight from the resting state. In addition, we have investigated the impact of the individual factors, such as wing planform, mass and flexibility. In my presentation, I will show the recent results using the butterfly-like flapping wing-body model.
24.06.2020, 16h00 CEST Prof. Dr. Jan-Henning Dirks, Biological Structures and Biomimetics, HS Bremen, Germany The insect exoskeleton – a versatile tool for locomotion
The insect exoskeleton is probably one of the evolutionary most successful skeletal structures. In my talk I will present and discuss a few selected examples of how morphology and biomechanical properties of the cuticle exoskeleton are closely correlated with basically all forms of insect locomotion, from flight to walking and even falling. Specific structures in the wings of locusts for example increase the wing’s resistance to fracture with a minimum of additional weight, thus allowing the locusts to migrate over long distances without wing failure. The locusts’ jumping hind leg tibia shows a structure biomechanically optimal to resist bending forces. Adhesive organs allow insects to stick to many surfaces, however can be tricked using a characteristic roughness. Finally, I will present a current project to illustrate how insects cope with “unwanted” forms of locomotion, such as falling or lying on their backs.
17.06.2020, 15h00 CEST Prof. Dr. Florian Mujires, Departement of Animal Sciences, Wageningen University, NL Maneuvering flight in flies and robots.
Flies are highly-maneuverable flyers, which is most apparent when you try to swat one. When evading a swatter or predator, a fly performs an
extremely-rapid and highly-controlled banked turn. These turns are
controlled by producing aerodynamic roll and pitch torques using
surprisingly small adjustments in their wingbeat pattern. Here, I will
discuss the unsteady aerodynamics of flapping insect flight, and how
insects such as flies adjust the aerodynamic forces on their wings to
control flight. I will also discuss how this knowledge has led to the
development of bio-inspired flapping robotic flyers, and how we then
used such flying robot to further unravel the control dynamics of
maneuvering insect flight.
10.06.2020, 15h00 CEST ( 9am local time ) Prof. Dr. Alper Erturk, Georgia Institute of Technology, USA
Woodruff Professor of Mechanical Engineering // Smart Structures and Dynamical Systems Laboratory // G. W. Woodruff School of Mechanical Engineering Bio-inspired actuation and aquatic locomotion using piezoelectric materials
This talk reviews our efforts over the past decade on bio-inspired piezoelectric actuation and hydrodynamic thrust generation for aquatic locomotion using fiber-based piezoelectric structures with interdigitated electrodes, namely Macro-Fiber Composite (MFC) structures. Most piezoelectric materials offer large actuation force but small deformation, requiring additional mechanisms for motion amplification. However, MFCs inherently strike a balance between the actuation force and deformation capabilities, offering high performance, ease of fabrication, geometric scalability, robustness, and silent operation. We describe three generations of our relevant research, starting with resonant mean thrust characterization for a bimorph MFC fin in a quiescent water for the first bending mode, enabled by out-of-phase actuation of two vacuum-bonded MFC laminates. The effect of a passive fin extension on the thrust resultant is also discussed over a wide frequency range covering the resonant dynamics. The second generation efforts include the first untethered piezoelectric swimmer in the literature, with thrust levels similar to those of biological fish with similar dimensions. Distributed-parameter electromechanical model of the piezoelectric fin is coupled with semi-empirical hydrodynamic loads from Morison’s equation for fins with different length-to-width aspect ratios, to identify inertia and drag coefficients. Vibration response is coupled with Lighthill’s equation for simple estimates of the mean thrust, confirmed with experimental measurements. The third generation concept contains a streamlined untethered swimmer with 3D printed components, tested both in a quiescent water and under imposed flow. Our early efforts toward actuation with multiple MFCs for 3D thrust vectoring are also discussed. Since piezoelectricity is reversible, the multifunctional concept of using the swimmer as an energy harvester is summarized to generate electricity from underwater base excitation and vortex-induced vibrations. Modeling and analysis of nonlinear structural dynamics of MFC fins under large deformations due to counteracting geometric and material nonlinearities are briefly addressed.
27.05.2020, 16h00 CEST ( 10am local time ) Ersan Demirer, Georgia Institute of Technology, USA Fish-like locomotion using bio-inspired plates
We develop a fluid-structure interaction computational model based on the lattice Boltzmann method and the thin plate model to investigate the impact of different strategies for bio-inspired locomotion with an oscillating elastic plate. We first probe the effects of actuation patterns on the dynamic response of plates with different mechanical and geometrical properties. In particular, we consider the actuation using a distributed internal moment that represents the actuation of piezoelectric smart materials and compare the hydrodynamic performance of such plates with the hydrodynamics of a plunging elastic plate. We then examine the combined plate actuation that integrates plunging using an external actuator with internal piezoelectric actuation. We search for hydrodynamic regimes in which the synergy of two different actuation modes leads to improved thrust production and efficiency. Furthermore we probe how passive attachments to active plates, including attachments with tapered geometry, can be harnessed to enhance the thrust production and efficiency. Finally, we study how complex actuation patterns integrating external and internal actuations can be used for navigation and maneuvering of robotic swimmers.
29.04.2020, 14h00 CEST Dr. Dmitry Kolomenskiy, Tokyo Institute of Technology and Chiba University, Japan Quantitative estimates in the fluid dynamics of bristled wings of small insects
Some smallest insects have fringed wings with long bristles (setae) visually resembling bird feathers. They are active fliers, which implies that bristled wings produce enough force to support the animal body weight and propel it through the air. Aerodynamic function of the bristled wings is a curious topic for its biological context as well as for the peculiarities of the air flow conditions. In this regard, experiments and numerical simulations have been carried out to evaluate aerodynamic force generation capacity of the wings of a miniature featherwing beetle Paratuposa placentis. The aerodynamic force coefficients have been determined from a dynamically scaled force measurement experiment with rotating bristled and membrane wing models in a glycerin tank. They have been used as numerical validation data for a computational fluid dynamics simulation using an adaptive Navier-Stokes solver. The latter has provided point-wise information about the flow field, thus allowing to evaluate flow parameters such as leakiness and permeability, and gain an understanding of the underlying fluid-dynamic mechanisms.
15.04.2020, 14h00 CEST Truong Hung, Aix-Marseille University, France Modelling of flexible insect wings using mass-spring system
The secret to the spectacular flight capabilities of flapping insects lies in their wings, which are often approximated as flat, rigid plates. Real wings are however delicate structures, composed of veins and membranes, and can undergo significant deformation. In this talk, we present detailed numerical simulations of such deformable wings. Two models of a bumblebee (Bombus ignitus) wing and a blowfly (Calliphora vicina) wing, using a mass-spring system, are presented. The mass-spring model uses a functional approach, thus modeling the different mechanical behaviors of the veins and the membranes of the wing. Then, numerical simulations of tethered flapping insects with the flexible wings are obtained with a fluid-structure interaction solver, coupling a mass–spring model for the flexible wing with a pseudo-spectral code solving the incompressible Navier–Stokes equations. We impose the no-slip boundary condition through the volume penalization method; the time-dependent complex geometry is then completely described by a mask function. This allows solving the governing equations of the fluid on a regular Cartesian grid. Our implementation for massively parallel computers allows us to perform high resolution computations with up to 500 million grid points. The preliminary results obtained in this work allow us to have some understanding about the role of wing flexibility in flapping flight. We found that wing flexibility hardly contributed to lift or thrust enhancement. However, the significant reduction of the required power suggested that wing flexibility plays an important role in saving flight energetic cost.
