Concept of Modular Kinematics to Design Ultra-high Precision Parallel Robots

Miniaturisation will be the key challenge for the next decade in numerous industrial fields, such as microelectronics, optics and biomedical engineering. Although most of their products already achieve footprints of some square millimeters, the trend towards the integration of a maximum number of elements in a minimal volume requires even more compact components. This tendency creates a growing need for industrial robots able to perform micromanipulation and microassembly tasks with a submicrometric precision. Nonetheless, the design of such machines is nowadays costly, both in time and money, mostly because of the twofold complexity of their development: first, from a kinematic standpoint, the use of a parallel structure consists in a particularly interesting approach to build ultra-high precision robots. However, the synthesis of such a kinematics proves especially challenging for machines presenting more than 3 degrees of freedom. Moreover, the resulting robots are scarcely flexible: if the industrial specifications are modified, which for example necessitates to add a degree of freedom or to change the position of a rotation centre, the design process has to be restarted, often from the very beginning. The second challenge consists in the mechanical design of flexure-based mechanisms: flexure hinges are joints which are based on the elasticity of the matter. They allow to perform motions which are without friction, backlash and wear; their use is thus mandatory to achieve the aimed submicrometric precision. Albeit the synthesis of planar and low-degree of freedom structures is now widely investigated, the development of a whole tridimensional flexure-based robot is still infrequent, especially in the industrial context. This thesis thus introduces a modular design methodology which significantly reduces the time-to-market of ultra-high precision robots. This procedure can be compared to a robotic Lego, where a finite number of conceptual building bricks allows to easily design and modify parallel robots. Furthermore, this work shows that the machines resulting from this approach present similar or even improved performances compared to robots developed more traditionally. The key aspect of this thesis consists in the concept of modular kinematics, which aims at facilitating the synthesis of parallel kinematics thanks to solution catalogues. At this step of the methodology, the conceptual building bricks and the kinematics are totally independent from any mechanical design: they can thus be used to synthesise a large variety of robots, from machine-tools to microscale robots. An exhaustive conceptual solution catalogue groups all kinematics generated by the combination of the building bricks. Then, a reduced solution catalogue for ultra-high precision is proposed: based on selection criteria linked with the design and machining of flexure-based mechanisms, it allows to reduce the total number of solutions and thus facilitates the practical use of the concept. The second part of this work details the mechanical design of the building bricks, whose main challenge consists in increasing the ratio between the working ranges of the mechanisms and their overall size. One or more flexure-based solutions have been developed for each motorised brick: a special emphasis is given to the original use of a Remote Centre of Motion, which allows to achieve high rotation angles while drastically reducing parasitic translations. The development of a standardised actuation sub-brick, common to all motorised bricks, introduces a new level of modularity, thus increasing even more the flexibility of the methodology. As for non-actuated bricks, original designs and uncommon uses of well-known mechanisms are proposed. A case study on a 5-degree of freedom robot, Legolas 5, finally illustrates the practical use of the methodology: first, the selection in the solution catalogue of a kinematics adapted to the specifications of the robot is detailed. Then, the development of the Legolas 5 prototype highlights the mechanical design of the necessary building bricks, as well as assembly subtleties, such as force alignment and gravity compensation, which allow to shrewdly design a high-performance robot. The measurements of this machine have shown motion resolution and repeatability of 50 nm in translation and 1.9 µrad in rotation (limited by the sensor resolution). This case study has generated the Legolas family, a new family of ultra-high precision parallel robots, which notably includes the orthogonal version of the Delta kinematics: using only 6 of the conceptual building bricks, one solution can be built for each of the 19 possible robot mobilities. The promising characterisation of the Legolas 5 tends to suggest that the robots from this family will be interesting candidates to fulfill the upcoming need for quickly designed and high-performance industrial ultra-high precision machines

Modularity and parallel kinematics: an original design methodology applied to high precision

This paper introduces a new methodology to design modular industrial ultra-high precision robots; it aims at significantly reducing both the complexity of their design and their development time. This modular concept can be considered as a robotic Lego®, where a finite number of building bricks is used to quickly design the robot and to easily change its mobility. The core of the concept is the thorough conceptual solution catalogue, which is independent from any mechanical design. This paper will first present the methodology and the techniques to establish this solution catalogue. Then, its application to high precision will include the formulation of hypotheses and a practical example of a 5-degree of freedom ultra-high precision robot design

A new concept of modular kinematics to design ultra-high precision flexure-based robots

This work deals with the kinematic conception and the mechanical design of ultra-high precision robots, which are at present costly to develop, both in time and money. The aim of this paper is thus to introduce a new modular concept of kinematics which allows to significantly reduce the time-to-market and a new double-stage flexure-based pivot. Regarding the modular concept of kinematics, this ‘robotic Lego’ consists in a finite number of building bricks allowing to rapidly design a high precision machine and to easily modify its mobility. The realised mock-up of a 4-DOF (Degrees of Freedom) robot, transformable into a 5-DOF one, validates this concept and the mechanical design of its bricks. Flexure hinges are used to achieve the aimed sub-micrometer precision; however, existing flexure-based rotary joints are not able to fulfil the requirements of some applications, as they present a too low angular stroke and a parasitic motion of their centre of rotation. Thus, this paper also introduces a new double-stage pivot based on blades working in torsion; experiments performed on a prototype allow to validate its principle and the simulation model used for its development

Chemical and enzymatical modifications of sugar derived from lignocellulose

Actually, biorefinery is increasingly considered as a promising alternative to petroleum chemistry, since it aims at not only the replacement of fossil energy but also the development of chemicals from biomass, with applications such as detergents, phytopharmaceutics, solvents, plastics, etc. The valorisation of carbohydrates from renewable raw materials is currently the subject of numerous researches. In this context, the synthesis of new surfactants derived from the sugars issued from the lignocellulose hydrolysis was undertaken by chemical or enzymatic routes. In this poster, the examples of glucose, cellobiose and uronic acids will be discussed. Whatever the way used, the reaction conditions (use of a catalyst, protection/deprotection steps, type of solvent, presence of co-solvent, reactant concentrations, etc) were optimized to yield a panel of carbohydrate derivatives (some examples of the structures obtained are given above). These differ by the nature of the alkyl chain (in length and in degree of saturation), the type of chemical bond (amide, ester, thioester, acetal), and the position of substitution. The impact of these differences on the techno-functional properties of these modified sugars will be evaluated.Programme d'Excellence TECHNOS

Food distribution influences social organization and population growth in a small rodent

This is the postprint version of the article. The published article can be located at the publisher's websiteIn polygynous mammals, the spatial clumping and predictability of food should influence spacing behavior of females whose reproductive success depends to a great extent on food availability, which would in turn affect male spacing behavior. Changes in the social and mating systems can then influence individual fitness and population dynamics. To test these hypotheses, we manipulated food distribution and predictability in enclosed populations of bank voles (Myodes glareolus) and monitored spacing behavior, survival, and reproduction of adult females and males over 3 months. Food was either spread out (dispersed treatment), spatially clumped and highly predictable (clumped treatment) or spatially clumped but less predictable (variable treatment). We found that females in the clumped treatment were more aggregated and had more overlapping home ranges compared with females in the dispersed and variable treatments. Male spacing behavior followed the same patterns. Despite different social organizations between treatments, no differences in home range size and mating systems were found in females and males. In addition, we found that females in the clumped food treatment had a higher probability of successfully producing weaned offspring, likely due to lower infanticide rates. This led to higher population growth compared with the other 2 treatments. These results suggest a tight relationship between the spatiotemporal distribution of food, social organization, and population dynamics.2014-04-3

Renal Proliferative and Phenotypic Changes in Rats With Two-Kidney, One-Clip Goldblatt Hypertension

Angiotensin II (All) is a vasoconstrictive peptide with hypertrophic and mitogenic effects on many cell types. Previous studies have shown that in vivo administration of All in rats results in proliferation of, and phenotypic changes in, many renal cell populations, but in doses also causing hypertension. Thus, it was not possible to differentiate nonhemodynamic from hypertensive effects of All. Therefore, we studied rats with renin-dependent, All-mediated hypertension (the two-kidney, oneclip Goldblatt model; mean systolic blood pressure 238 ± 48 ν 140 ± 6 mm Hg in sham-operated controls). The undipped kidneys, which were exposed to high blood pressure, developed significant glomerular and tubulointerstitial injury, tubulointerstitial cell proliferation, dense focal interstitial monocyte-macrophage influx, increased deposition of types I and IV collagen, as well as increased cellular expression of desmin and actin, in tubulointerstitial areas when examined at 11 weeks. In contrast, clipped kidneys, protected from hypertension but with high local renin expression, had minimal abnormalities. These studies suggest that in this model increased renin, and presumably All, does not mediate significant proliferative or phenotypic changes in the kidney in the absence of hypertension at 11 weeks. Am J Hypertens 1994;7:177-18

Complement inhibition can decrease the haemostatic response in a microvascular bleeding model at multiple levels.

BACKGROUND Haemostasis is a crucial process by which the body stops bleeding. It is achieved by the formation of a platelet plug, which is strengthened by formation of a fibrin mesh mediated by the coagulation cascade. In proinflammatory and prothrombotic conditions, multiple interactions of the complement system and the coagulation cascade are known to aggravate thromboinflammatory processes and increase the risk of arterial and venous thrombosis. Whether those interactions also play a relevant role during the physiological process of haemostasis is not yet completely understood. The aim of this study was to investigate the potential role of complement components and activation during the haemostatic response to mechanical vessel injury. METHODS We used a microvascular bleeding model that simulates a blood vessel, featuring human endothelial cells, perfusion with fresh human whole blood, and an inducible mechanical injury to the vessel. We studied the effects of complement inhibitors against components of the lectin (MASP-1, MASP-2), classical (C1s), alternative (FD) and common pathways (C3, C5), as well as a novel triple fusion inhibitor of all three complement pathways (TriFu). Effects on clot formation were analysed by recording of fibrin deposition and the platelet activation marker CD62P at the injury site in real time using a confocal microscope. RESULTS With the inhibitors targeting MASP-2 or C1s, no significant reduction of fibrin formation was observed, while platelet activation was significantly reduced in the presence of the FD inhibitor. Both common pathway inhibitors targeting C3 or C5, respectively, were associated with a substantial reduction of fibrin formation, and platelet activation was also reduced in the presence of the C3 inhibitor. Triple inhibition of all three activation pathways at the C3-convertase level by TriFu reduced both fibrin formation and platelet activation. When several complement inhibitors were directly compared in two individual donors, TriFu and the inhibitors of MASP-1 and C3 had the strongest effects on clot formation. CONCLUSION The observed impact of complement inhibition on reducing fibrin clot formation and platelet activation suggests a role of the complement system in haemostasis, with modulators of complement initiation, amplification or effector functions showing distinct profiles. While the interactions between complement and coagulation might have evolved to support haemostasis and protect against bleeding in case of vessel injury, they can turn harmful in pathological conditions when aggravating thromboinflammation and promoting thrombosis

Food distribution influences social organization and population growth in a small rodent

This is the postprint version of the article. The published article can be located at the publisher's websiteIn polygynous mammals, the spatial clumping and predictability of food should influence spacing behavior of females whose reproductive success depends to a great extent on food availability, which would in turn affect male spacing behavior. Changes in the social and mating systems can then influence individual fitness and population dynamics. To test these hypotheses, we manipulated food distribution and predictability in enclosed populations of bank voles (Myodes glareolus) and monitored spacing behavior, survival, and reproduction of adult females and males over 3 months. Food was either spread out (dispersed treatment), spatially clumped and highly predictable (clumped treatment) or spatially clumped but less predictable (variable treatment). We found that females in the clumped treatment were more aggregated and had more overlapping home ranges compared with females in the dispersed and variable treatments. Male spacing behavior followed the same patterns. Despite different social organizations between treatments, no differences in home range size and mating systems were found in females and males. In addition, we found that females in the clumped food treatment had a higher probability of successfully producing weaned offspring, likely due to lower infanticide rates. This led to higher population growth compared with the other 2 treatments. These results suggest a tight relationship between the spatiotemporal distribution of food, social organization, and population dynamics.2014-04-3

Multiple glacial refugia and contemporary dispersal shape the genetic structure of an endemic amphibian from the Pyrenees

Historical factors (colonization scenarios, demographic oscillations) and contemporary processes (population connectivity, current population size) largely contribute to shaping species’ present-day genetic diversity and structure. In this study, we use a combination of mitochondrial and nuclear DNA markers to understand the role of Quaternary climatic oscillations and present-day gene flow dynamics in determining the genetic diversity and structure of the newt Calotriton asper (Al. Dugès, 1852), endemic to the Pyrenees. Mitochondrial DNA did not show a clear phylogeographic pattern and presented low levels of variation. In contrast, microsatellites revealed five major genetic lineages with admixture patterns at their boundaries. Approximate Bayesian computation analyses and linear models indicated that the five lineages likely underwent separate evolutionary histories and can be tracked back to distinct glacial refugia. Lineage differentiation started around the Last Glacial Maximum at three focal areas (western, central and eastern Pyrenees) and extended through the end of the Last Glacial Period in the central Pyrenees, where it led to the formation of two more lineages. Our data revealed no evidence of recent dispersal between lineages, whereas borders likely represent zones of secondary contact following expansion from multiple refugia. Finally, we did not find genetic evidence of sex-biased dispersal. This work highlights the importance of integrating past evolutionary processes and present-day gene flow and dispersal dynamics, together with multilocus approaches, to gain insights into what shaped the current genetic attributes of amphibians living in montane habitats.info:eu-repo/semantics/publishedVersio

Impact of work arrangements during the COVID-19 pandemic on mental health in France

• Symptoms of anxiety/depression were found in 28.8% of the participants at least once. • Unemployment and financial difficulties were associated with anxiety/depression. • Targeted mental health support could lessen mental health impact