Optic flow based autopilot: From insects to rotorcraft and back

International audienceWhen insects are flying forwards, the image of the ground sweeps backwards across their ventral viewfield, forming an "optic flow", which depends on both the groundspeed and the height of flight. To explain how these animals manage to avoid the ground using this image motion cue, we suggest that insect navigation hinges on a visual feedback loop we have called the optic flow regulator, which controls the vertical lift. To test this idea, we built a micro-helicopter equipped with a fly-inspired optic flow sensor and an optic flow regulator. We showed that this fly-by-sight microrobot can perform exacting tasks such as takeoff , level flight and landing. Our control scheme accounts for many hitherto unexplained findings published during the last 70 years on insects' visually guided performances, including the facts that honeybees descend under headwind conditions, land with a constant slope and drown when travelling over mirror-smooth water. Our control scheme explains how insects manage to fly safely without any of the instruments used onboard aircraft to measure the height of flight, the airspeed, the groundspeed, and the descent speed. An optic flow regulator could be easily implemented neurally. It is just as appropriate for insects (1) as it would be for aircraft (2,3)

Réguler le flux optique latéral pour naviguer dans un corridor

International audienceAs a first step toward an Automatic Flight Control System (AFCS) for Micro-Air Vehicle (MAV) obstacle avoidance, we introduce a vision based autopilot (LORA: Lateral Optic flow Regulation Autopilot), which is able to make a hovercraft automatically follow a wall or centre between the two walls of a corridor. A hovercraft is endowed with natural stabilization in pitch and roll while keeping two translational degrees of freedom (X and Y) and one rotational degree of freedom (yaw). We show the feasibility of an OF regulator that maintains the lateral Optic Flow (OF) on one wall equal to an OF set-point. The OF sensors used are Elementary Motion Detectors (EMDs), whose working was directly inspired by the housefly motion detecting neurons. The properties of these neurons were previously analysed at our laboratory by performing electrophysiological recordings while applying optical microstimuli to single photoreceptor cells of the compound eye. The simulation results show that depending on the OF set-point, the hovercraft either centres along the midline of the corridor or follows one of the two walls, even with local lack of optical texture on one wall, such as caused, for instance, by an open door or a T-junction. All these navigational tasks are performed with one and the same feedback loop, which consists of a lateral OF regulation loop that permits relatively high-speed navigation (1m/s, i.e 3 body lengths per second), with a minimalist visual system (only two EMDs, each EMD uses two pixels). This principle contrasts with the formerly proposed strategy that consists in equalizing the two lateral OFs. The passive visual sensors and the simple processing system are suitable for use with MAVs with an avionic payload of only a few grams. The goal is to achieve MAV automatic guidance or to relieve a remote operator from guiding it in challenging environments such as urban canyons or indoor environments

UV-induced inactivation and mutation-induction in a new two-component heterokaryon (59) homozygous for the excision-repair deficient mutant uvs-2

UV-induced inactivation and mutation-induction in a new two-component heterokaryon (59) homozygous for the excision-repair deficient mutant uvs-2

Flying in 3D with an Insect based Visual Autopilot

International audienceFlying insects rely on Optic Flow (OF) cues to avoid collisions, control their speed, control their height, and land. Recent studies have shown that the principle of “OF regulation” may account for various behaviors observed in freely flying insects. The aim of the present study was to suggest a visually guided autopilot enabling an insect to navigate in 3D, and to test its robustness to natural images. Using computer-simulation experiments, we simulated a bee that flies through a tunnel wallpapered with natural images, by controlling both its ground speed and clearance all four sides: the lateral walls, the ground, and the ceiling. The simulated bee can translate along three directions (the surge, sway, and heave axes): it is therefore fully actuated. The new visuo-motor control system, called ALIS (AutopiLot using an Insect based vision System), is a dual OF regulator consisting of two interdependent feedback loops: the speed control loop (along the surge axis) and the positioning control loop (along both the sway and heave axes), each of which has its own OF set-point. The experiments show that the simulated bee navigates safely along a straight tunnel, while compensating for the major OF perturbations caused by, e.g., a tapering of the tunnel or the lack of texture on one wall. The minimalistic visual system used here (only eight pixels) is robust to naturally contrasted stimuli and tunnels, and is sufficient to control both the clearance from the four sides and the forward speed jointly, without requiring to measure any speeds or distances. Besides, the ALIS autopilot accounts remarkably for the quantitative results of ethological experiments performed on honeybees flying freely in straight or tapered corridors

Negotiating the inhuman: Bakhtin, materiality and the instrumentalization of climate change

The article argues that the work of literary theorist Mikhail M. Bakhtin presents a starting point for thinking about the instrumentalization of climate change. Bakhtin’s conceptualization of human–world relationships, encapsulated in the concept of ‘cosmic terror’, places a strong focus on our perception of the ‘inhuman’. Suggesting a link between the perceived alienness and instability of the world and in the exploitation of the resulting fear of change by political and religious forces, Bakhtin asserts that the latter can only be resisted if our desire for a false stability in the world is overcome. The key to this overcoming of fear, for him, lies in recognizing and confronting the worldly relations of the human body. This consciousness represents the beginning of one’s ‘deautomatization’ from following established patterns of reactions to predicted or real changes. In the vein of several theorists and artists of his time who explored similar ‘deautomatization’ strategies – examples include Shklovsky’s ‘ostranenie’, Brecht’s ‘Verfremdung’, Artaud’s emotional ‘cruelty’ and Bataille’s ‘base materialism’ – Bakhtin proposes a more playful and widely accessible experimentation to deconstruct our ‘habitual picture of the world’. Experimentation is envisioned to take place across the material and the textual to increase possibilities for action. Through engaging with Bakhtin’s ideas, this article seeks to draw attention to relations between the imagination of the world and political agency, and the need to include these relations in our own experiments with creating climate change awareness

Retreating to nature : rethinking 'therapeutic landscapes'

There is a long history of removing oneself from ‘society’ in order to recuperate or repair. This paper considers a yoga and massage retreat in Southern Spain, and what opportunities this retreat experience might offer for recuperation and the creation of healthy bodies. The paper positions ‘nature’ as an active participant, and as ‘enrolled’ in the experiences of the retreat as a ‘therapeutic landscape’, and questions how and what particular aspects of yoga practice (in intimate relation with place) give rise to therapeutic experiences

From paradox to pattern shift: Conceptualising liminal hotspots and their affective dynamics

This article introduces the concept of liminal hotspots as a specifically psychosocial and sociopsychological type of wicked problem, best addressed in a process-theoretical framework. A liminal hotspot is defined as an occasion characterised by the experience of being trapped in the interstitial dimension between different forms-of-process. The paper has two main aims. First, to articulate a nexus of concepts associated with liminal hotspots that together provide general analytic purchase on a wide range of problems concerning “troubled” becoming. Second, to provide concrete illustrations through examples drawn from the health domain. In the conclusion, we briefly indicate the sense in which liminal hotspots are part of broader and deeper historical processes associated with changing modes for the management and navigation of liminality

Improving tribological properties of cast Al-Si alloys through application of wear-resistant thermal spray coatings

Flame Spray Thermal Spray coatings are low-cost, high-wear surface-treatment technologies. However, little has been reported on their potential effects on cast automotive aluminum alloys. The aim of this research was to investigate the tribological properties of as-sprayed NiCrBSi and WC/12Co Flame Spray coatings applied to two cast aluminum alloys: high-copper LM24 (AlSi8Cu3Fe), and low-copper LM25 (AlSi7Mg). Potential interactions between the mechanical properties of the substrate and the deposited coatings were deemed to be significant. Microstructural, microhardness, friction, and wear (pin-on-disk, microabrasion, Taber abrasion, etc.) results are reported, and the performance differences between coatings on the different substrates were noted. The coefficient of friction was reduced from 0.69-0.72 to 0.12-0.35. Wear (pin-on-disk) was reduced by a factor of 103-104, which was related to the high surface roughness of the coatings. Microabrasion wear was dependent on coating hardness and applied load. Taber abrasion results showed a strong dependency on the substrate, coating morphology, and homogeneity