Ricardo P S M Lobo

Christine Allancon

Francisco J Gotor

Jean-Marc Bassat

Jean-Pierre Loup

Philippe Odier

Krystoff Dembinski

Francois Gervais

Corinne Champeaux

Pascal Marchet

Alain Catherinot

Analysis of infrared -visible -near -ultra violet reflectivity of conducting and superconducting oxides

We analyse infrared-visible-near-ultraviolet spectra of oxide materials in the semiconducting or metallic phase. We show that the response of laser-ablated YBa2Cu3O7 film can be fitted by a modified Drude term without mid-infrared absorptions. Mid-infrared and visible absorptions are discussed for textured YBaCuO, BaBiO3 and Pr2NiO4+δ as well as indication of their polaronic origin.

INTRODUCTION

Since the discovery of high-Tc superconductivity by Bednorz and Mullcr [1], an enormous interest in conducting and superconducting oxides has appearcd. Despite the monumental number of works in this field, many points remain still unclear either in the normal state behaviour or in the superconducting one. To better understand the phenomena observed in these materials, we have performed room temperature polarised measurements in various conducting oxide materials for comparison.

EXPERIMENTAL

Reflectivity measurements have been performed with a new IFS 307 Bruker spectrometer composed of two complementary interferometers covering the spectral range of 20 to 25000 cm -l . Samples used have been obtained by laser ablation (YBaCuO), crystallisation of molten BaBiO3, floating zone (Pr2NiO4) and texturation methods (textured YBaCuO).

MODIFIED DRUDE MODELLING

A Drude model cannot account for the conducting behaviour of oxides [2]. Generally, additional midinfrared bands and/or frequency dependent damping are necessary [3]. Here we propose a very simple extension of a Drude behaviour which introduces different dampings (γ) at plasma (ωp) and zero frequency yielding at dielectric susceptibility (χpl).

= -∝

(1)

Note that on setting γp = γo one arrives at the well known Drude behaviour. We show in Fig. 1 reflection measurements of a laser ablated YBaCuO ab-oriented film besides fits obtained from a simple Drude term and a modified one (Eq. 1) Changes of reflectivity introduced by phonons oscillators or mid-infrared bands are negligible because they are screened by the plasmon, so that we can state that the conducting behaviour is expressed by a free charge carrier based model only.

MID INFRARED EXCITATIONS

Up to now, we have observed mid-infrared and visible bands in all oxides with a charge carrier concentration lower than 10 21 cm -3 , a threshold above which they are screened by the plasmon. Here we present two examples: BaBiO3 (Fig. 2) has an absorption near 2 eV. This absorption is generally interpreted as a charge disproportionation between Bi sites. Being in a effective +4 site, Bi atoms would sit at these sites in states +3 and +5 creating an energy gap which can originate the absorption [5]. An alternative is to think in terms of a dynamic interchange of the valence of the Bi atom.

Pr2NiO4+x shown in Fig. 3. presents only phonons when x = 0. Both Drude-likc profile and mid-infrared bands appear when the compound becomes conducting with oxygen excess (δ ≠ 0). The plasma frequency increases upon heating and starts screening both phonons and mid-infrared band. No change is observed for the polarisation parallel to the c axis, with only phonons in all cases. Electronic properties are thus clearly found bidimensional with, for the conducting ab-planes simultaneous appearance of two excitations. One is a Drude like component. The other (at 5000 cm -1 ) might be a polaronic signature.

Finally, a similar effect can be observed in textured YBaCuO sample with an oxygen concentration of about 6.5. Its reflectivity spectra are in Fig. 4. In this case we do observe a mid-infrared band in the conducting ab-plane but such an absorption is not so evident along the almost insulator c-axis [6). Once again we observe that this extra absorption (near 4000 cm -1 ) in the ab-plane is associated with the presence of free charge carriers introduced by oxygen stoichiometry, This means that possibly this absorption is also polaronic in YBaCuO.

CONCLUSION

We have shown that the infrared-visible-near UV conductivity of oxides with highest charge carrier concentration can be explained in terms of a modified Drude model alone with no need for additional mid-infrared bands. Nevertheless, these mid-infrared bands do exist in the conducting plane of 2D systems, for moderated electronic concentrations, and they may have a polaronic origin.

RPSML thanks Brazilian agency CNPq. FJG Acknowledges EU (Human Capital and Mobility)

Fig. 1 :

 1 Fig. 1: Room temperature YBaCuO reflectivity and fits by Drude and modified Drude models

Fig. 2 :Fig. 3 :Fig. 4 :

 234 Fig. 2: Visible absorption in BaBiO3


C Champeaux

P Marchet

A Catherinot

Epitaxial ferroelectric PZT and BST thin films by pulsed UV laser deposition

Ferroelectric PbZr0.52Ti0.48O3 (PZT) and Ba0.65Sr0.35TiO3 (BST) thin films are prepared by laser ablation of sintered ceramic targets. The influence of the substrate temperature during deposition on the composition and the crystallographic structure is investigated for different substrates, in order to achieve an oriented or epitaxial growth.

Introduction

Ferroelectric materials are highly attractive with respect to non-volatile memories, dynamic random access memories and pyroelectric devices [1][2][3], because of their spontaneous polarization and high dielectric constant. So various thin ferroelectric films such as BaTiO3, SrTiO3, PbTiO3, etc., have been synthesized using different techniques including sol gel method [4], ion-beam sputtering [5], metal-organic decomposition [6] and pulsed laser deposition [7]. This latter method, 'famous' since its success in producing high quality thin films of high temperature superconductors, offers the ability to achieve highly oriented stoichiometric films at low substrate temperature in a high oxygen pressure. It can be applied to the deposition of ferroelectric materials of which many are multicomponent oxides having a perovskite-like structure, as superconductors have.

In this paper we describe our recent experiments to grow PbZr0.52Ti0.48O3 (PZT) and Ba0.65Sr0.35TiO3 (BST) thin films by pulsed laser ablation, under various conditions and the characterization of their composition and crystalline structure.

Experimental procedure

Set-up

Experiments are performed in an ultra high vacuum stainless-steel cell equipped with an introduction chamber for target and substrate manipulations. The stoichiometric sintered target of PbZr0.52Ti0.48O3 or Ba0.65Sr0.35TiO3, prepared by a conventional sintering process and having a density of 90% of the theoretical value, is mounted on a rotating system to ensure an uniform ablation rate. The beam of a pulsed excimer laser (248 nm wavelength, pulse duration 14 ns, repetition rate 10 Hz, energy per pulse 20-300 mJ), focused by a UV grade lens, is incident onto the target at an angle of 35°. The size of the elliptical laser spot on the target surface is typically 2.2 mm 2 . The vaporized material ejected normally to the target surface is deposited on a substrate placed opposite the target at about 4 cm. The substrate can be heated up to about 800°C by an halogen lamp. Several gas inlets allow the control of the deposition and the cooling atmospheres.

Deposition parameters

According to the likeness of superconducting and ferroelectric materials (oxides with complex chemical composition and perovskite-like structure), working parameters are similar to those that we used for the realisation of high quality epitaxial YBaCuO superconducting thin films [8]. So the laser fluence on the target is 3 J/cm 2 , the oxygen pressures are 0.3 mbar during deposition and 330 mbar during cooling. The films thickness, investigated by a surface profile measuring system, is typically 300-400 nm after ten minutes deposition.

Film characterization

The chemical composition of the films is determined by energy dispersive spectroscopy (EDS) and the structure is investigated by X-ray diffraction (XRD).

PZT films on (100) MgO substrates

Single-crystal MgO substrate is chosen because of the compatibility between its lattice parameter (a = 4.21 Å) and the PZT one (a = 4.036 Å; c = 4.146 Å).

Composition

Fig. 1 shows the evolution of the composition of films as a function of the deposition temperature. While the compositions of Zr and Ti remain constant close to the ideal ones (dotted lines on the figure), the one of Pb is strongly dependent of the deposition temperature. Above 600°C the Pb content of films decreases drastically and cancels at 790°C because of the volatility of this element and its oxides at elevated temperatures [9,10].

Structure

XRD patterns of the films deposited in the temperature range 400-800°C are given on Fig. 2. At low temperature (400°C), the films are amorphous. The pyrochlore phase is present at 500°C. The increase of the temperature leads to the vanishing (at 600°C) of the pyrochlore phase on behalf of the perovskite one. A high degree of orientation is observed for perovskite phase, with (100) or (001) orientation. Above 700°C, phases without Pb, in agreement with composition study, take the place of the perovskite phase. These results indicate that in situ obtaining of PZT films with oriented perovskite structure is possible in the deposition temperature range 600-650°C.

PZT film on gold electrodes

100 nm thick bottom gold electrode is deposited on a MgO substrate using a sputtering technique. The PZT film is realized in the previous experimental conditions with an intermediate temperature (630°C). X-ray diffraction (Fig. 3) measurements show mainly perovskite phase with a weak secondary phase which is not identified (only one peak). Unlike previous reports [9], perovskite phase remains (100) oriented, showing little influence of the metallic electrode. This result is very important because a high degree of orientation (up to epitaxy) is needed for good electrical properties.

BST films

1. On (100) SrTiO3 substrates

Concerning the BST (lattice parameter 3.97 Å deposition, strontium titanate substrates (SrTiO,, a = 3.9Å) are chosen. A systematic study of the crystalline structure of the deposited films is undertaken in the range 500-700°C. X-ray diffraction results are given on Fig. 4. At 500°C, the films are amorphous. (100)-oriented BST phase grows from 600°C. Lattice parameters, calculated from X-ray diffraction (3.97 Å), is significant of the Ba0.65Sr0.35TiO3 stoichiometry. So the transport of the species from the target to the substrate is congruent. The increase of the substrate temperature leads to a decrease of the width of the X-ray peaks, so, probably to an increase of the grain sizes.

On Si substrates with metallic multilayers bottom electrodes

For microelectonic applications (memories), silicon substrates are preferred. A few experiments are performed on different metallic electrodes (Au, Pt, TiN, TiW… ). with the same deposition parameters. Unlike observations for PZT films, X-ray diffraction investigations reveal in all cases unoriented (polycristalline) BST perovskite phase. So, the orientation during deposition seems to depend strongly on substrate structure and interface phenomena.

Conclusion

PZT and BST films are prepared respectively on various substrates by laser ablation. The first experiments show a congruent transport of the species from the target to the substrate and an epitaxial growth on single-crystal substrates for a deposition temperature of 600°C, when the other parameters are similar to those that we used for the deposition of epitaxial YBaCuO superconducting thin films (oxygen pressure 0.3 mbar, fluence 3 J/cm 2 ). These results prove that the deposition parameters seem to be approximatively the same for multicomponent oxides with perovskite-like structures. But the crystalline structure of films depends strongly on the substrate nature. The second step of this study will concern the deposition of PZT and BST materials on YBaCuO/MgO substrates in order to characterize their electrical properties.

Fig. 1 .

 1 Fig. 1. PZT film composition versus deposition temperature (dotted lines correspond to the theoretical composition).

Fig. 2 .

 2 Fig. 2. X-ray diffraction patterns of PZT films on MgO substrates as a function of the deposition temperature (: (100) oriented PZT perovskite, : PZT pyrochlore, S: substrate).

Fig. 3 .

 3 Fig. 3. X-ray diffraction patterns of PZT film on Au/MgO substrate (: (100) oriented PZT perovskite, : unidentified secondary phase, S: substrate).


G Mugnier

P Panczer

A Marchet

B Catherinot

Jacquier

C Garapon

C Champeaux

J Mugnier

G Panczer

P Marchet

A Catherinot

B Jacquier

Preparation of TiO2 thin films by pulsed laser deposition for waveguiding applications

Preparation of TiO, thin films by pulsed laser deposition for waveguiding applications

Introduction

TiO2 is an important material for optical applications (as antireflective coating for example) and TiO2 thin films have been grown by a number of techniques, each one of them emphasizing different advantages [l]. Surprisingly there are only few reports on Pulsed Laser Deposition (PLD) of TiO2 [2][3][4], though the interest of this technique has been well recognized. If optical waveguide fabrication and characterization are extensively studied for integrated optics applications, PLD technique has only very recently been used, and only for nonlinear optical materials such as LiNbO3 [5,6]. The aim of this study is to show the feasibility of growing by PLD TiO2 thin films suitable for optical waveguiding applications.

Thin films deposition

The experimental set-up has already been described [7]. We give only the main parameters of the deposition procedure. The beam of a KrF excimer laser (A = 248 nm) was focussed on the rotating target with a fluence of 3 J/cm 2 . The temperature of the substrate, heated by an halogen lamp, was 790°C. The base pressure in the deposition chamber was 4 X 10 -8 mbar but the film deposition took place in an oxygen pressure of 10 -l mbar. The cooling of the films was achieved in a 200 mbar pressure of oxygen. The targets have been prepared from TiO2 rutile powder with very fine grains (around 10 nm), compressed and sintered at 1050°C in air up to 56% of the bulk density, keeping the rutile structure as checked by X-ray diffraction (XRD) and Raman spectroscopy (see Section 3.2). Films have been grown on carefully cleaned monocrystalline substrates: MgO (100), Si covered with a SiO2 amorphous layer, about 1 µm thick, and Al2O3. The discussion will concentrate more specifically on these samples.

The thickness of the films was determined with a Sloan Dektak IIA profilometer. Films of less than 1 µm thickness have been obtained after a 40 mn deposition. Optical microscopy observations show that the samples have good transparency and are homogeneous, crack-free, with no droplets. Some films have been grown under other conditions (Table I) and the influence of the deposition parameters will be discussed briefly in the next section.

Structural characterization

TiO2 exists in three different crystalline phases: anatase, rutile (both tetragonal) and brookite (orthorhombic). Amorphous TiO2 crystallises upon heating into anatase, which transforms into rutile above about 700°C. Depending on the deposition techniques and parameters, it is possible to obtain amorphous TiO2 (for low substrate temperature generally) or the anatase and rutile phases or both, with various proportions, orientations and crystal sizes [1,8]. For the structural characterization we used X-ray diffraction and Raman spectroscopy.

X-ray diffraction

Fig. 1 shows the XRD diagrams of TiO2 thin films deposited on SiO2/Si,and MgO substrates, registered with a Siemens D500 diffractometer (λ Cu Kα= 1.540 A, graphite back-monochromator). In the case of SiO2/Si substrate the spectrum contains essentially the (004) line of anatase with very weak (101) and (200) lines. The film is thus constituted of partially oriented anatase crystals, the preferential orientation of the c-axis being perpendicular to the film surface. A small amount of rutile is also detected, as some weak rutile lines, (101), ( 111) and (211) are observed.

For the film deposited on the oriented MgO substrate, besides the very intense line due to the (200) plane of MgO, the same (004) anatase line is predominant in the spectrum. The same preferential orientation of the c-axis of the anatase crystals, perpendicular to the film surface, is obtained. In addition weak (112) and (200) lines are observed for anatase. The contribution of rutile, detected by the (200) and (111) lines, is weak.

Raman spectroscopy

The films were investigated using a Dilor X-Y modular multichannel laser Raman spectrometer equipped with a confocal microscope (backscattering configuration). The exciting wavelength is 514.5 nm. With the used objective ( X 50), the analysed area has a diameter of about 10 µm.

Fig. 2 compares the Raman spectra of the rutile target and the film deposited on SiO2/Si. The target exhibits the characteristic rutile spectrum in this range [9], with bands at 612 cm -1 (A1g), 447 cm -1 (E g), and 143 cm -1 (B1g). The 235 and 360 cm -1 lines are attributed to multiphonon scattering. The spectrum of the film, besides the 521.5 cm -1 line due to the Si substrate, is mainly constituted by the anatase spectrum [10]: 639 cm -1 ' (E g), 516 cm -1 (A1g -B1g), 399 cm -1 (B1g) , 197 cm -1 (E g), 144 cm -1 (E g). Two weak bands at 618 and 442 cm -1 show that some amount of rutile phase is also present. Changing the polarization of the exciting laser beam does not modify significantly the relative line intensities. This is in agreement with a preferential orientation of the c-axis perpendicular to the film surface, taking into account the polarization selection rules for the Raman spectrum of anatase [10].

Fig. 3 gives the Raman spectra of the film grown on a MgO substrate for two polarizations. The anatase spectra are recognized, with a weak rutile contribution. The change in the relative intensities of the lines with polarization indicates that the c-axis preferential orientation perpendicular to the film surface is less well defined than for the SiO2/Si substrate. All these results are in agreement with those of X-ray diffraction. However further information may be obtained, as will be discussed below.

Discussion

It is interesting to notice first that, under these deposition conditions (0.1 mbar of O2, 790°C as substrate temperature), the predominant phase is anatase, though its growth takes place at a temperature above that at which it is supposed to begin to transform into rutile (700°C). However, if rutile is the thermodynamically stable phase, anatase may be kinetically stable until about 1000°C, depending on the grain size for example. Such a situation is similar to that of sol-gel thin films where anatase alone has been observed even after annealing at 900°C [11].

Another point of interest is that anatase has a preferential orientation of the c-axis perpendicular to the film surface, for both a monocrystalline substrate, MgO, and an amorphous one, SiO2, deposited on Si. The film deposited on Al2O3 is amorphous according to XRD, but shows some of the rutile and anatase lines in the Raman spectrum. As the coherent domain sizes for the two processes should be different, it may be inferred that very small and/or imperfect crystallites are present.

For films #l and #2 the width of the anatase main line at 144 cm -1 is broaden relative to that of the bulk crystal (14 cm -1 instead of 7 cm -1 ) [12]. The line width can be related to the mean size of the crystals, which could be of the order of 10 nm as it has been observed for anatase powders [START_REF] Vasseur | These d'universite[END_REF] and in anatase thin films deposited by the sol-gel method [11].

Our results differ from previous reports on TiO2 deposition on Si wafers, as could be expected for different deposition parameters. Depositions with a YAG laser at 532 nm under vacuum lead to polycrystalline rutile films for a substrate temperature of 850°C, with a few anatase phase at 500°C. Films grown at lower substrate temperatures are amorphous [2], as those deposited with an ArF laser at substrate temperature less than 200°C, under various O2 pressures [3]. At last, for a deposition with an ArF laser at 450°C without introduction of O2, rutile is obtained with a (200) orientation and when increasing the O2, pressure from 0.1 T to 0.3 T, one goes from rutile (with (110) and (200) lines) to anatase (with (101) and (004) main lines) [4].

Preliminary results on the influence of deposition parameters for a MgO substrate (Table 1) show that rutile is preponderant at higher laser fluence, higher oxygen pressure and if a rutile ceramic target prepared with coarser grains is used. Better understanding of the deposition process could result from the study of the nature and energy of the species present in the plume [START_REF] Champeaux | Laser Ablation of Electronic Materials: Basic Mechanisms and Applications[END_REF].

Optical characterization

The optical waveguiding potentiality has been tested by the dark m-line spectroscopy, the principle of which is briefly recalled. The beam of an He-Ne laser (λ= 632.8 nm) is coupled into the film with the aid of a rutile prism (angle: 45.38 degrees): for discrete values of the incidence angle, the evanescent wave, existing in the air gap between the prism and the film, may excite the guided modes in the film. The coupling is detected by the apparition of dark lines in the reflected beam and the effective index may be calculated for each mode [START_REF] Uhich | [END_REF].

For sample #l (TiO2 on SiO2/Si) five TE (transverse electric) modes and only three TM (transverse magnetic) modes are observed due to a low coupling efficiency. Assuming a step index profile, the thickness (930 nm) and the refractive index (n = 2.219) have been deduced from the TE modes. For sample #2 (TiO2 on MgO) four TE and four TM modes are pointed, but, as for sample #l, the dark lines are large (up to 0.5 degree), inducing a low precision of the measurements. Both TE and TM observations provide a thickness of 870 ± 3 nm.

The refractive index are ranging from 2.23 (TE) to 2.25 (TM) which is in agreement with an anisotropy of the layer observed by XRD and Raman spectroscopy. Though light coupling into the film could be achieved with a prism, it was not possible to detect any propagation on a significant distance. This can be due to several reasons: surface roughness, porosity at the scale of the wavelength, as the refractive index is smaller than for the bulk crystals (n0 = 2.605, ne = 2.899 for rutile, n0 = 2.488, ne = 2.561 for anatase, at 589.3 nm).

For the film #4 (TiO2 on MgO deposited at lower temperature) two dark lines, very sharp (less than 0.05 degree), are observed for the TE, and TM, modes. As this film is thin (less than 200 nm) due to a shorter deposition time, only the first two modes exist, which does not allow the calculation of the thickness and refractive index. The good quality of this film is attested by the sharpness of the lines. In this case a good hope exists of observing guided wave propagation. Unfortunately, due to the small size of the sample (5 X 5 mm 2 ), this could not be checked. At last, waveguiding over a distance of about 1 cm was observed in TiO2 film #3 on Al2O3.

Conclusion

We have grown TiO, thin films on MgO, SiO2/Si and Al2O3 substrates by PLD from rutile ceramic targets. The films are mainly constituted by small crystals of anatase, r-utile or both, depending on the deposition parameters. These crystals are partially oriented, as characterized by X-ray diffraction and micro-Raman spectroscopy. We measured their thickness and refractive index by m-line spectroscopy. Favorable waveguiding properties may be expected, depending on substrate and film structure.

Fig. 1 .

 1 Fig. 1. X-ray diffraction diagrams of TiO2 films deposited on SiO2 /Si and MgO

Fig. 2 .Fig. 3 .

 23 Fig. 2. Raman spectra of the rutile target and TiO2 films on SiO2 /Si

Table 1 :

 1 Deposition parameters of the samples and predominant crystalline phase observed by X-ray diffraction and Raman spectroscopy

Acknowledgements

We are indebted to R.S.A. LeRubis for graciously providing us with the sapphire substrate. We would like to thank very much Pr. M. Boudeulle for helpful discussions, C. Urlacher for m-line data treatment and R. Vera for carrying out X-ray diffractometry.


Nicolò Pedemonte
email: nicolo.pedemonte@irt-jules-verne.fr

Tahir Rasheed
email: tahir.rasheed@ls2n.fr

David Marquez-Gamez
email: david.marquez-gamez@irt-jules-verne.fr

Philip Long
email: p.long@northeastern.edu

Étienne Hocquard
email: etienne.hocquard@irt-jules-verne.fr

Francois Babin
email: francois.babin@irt-jules-verne.fr

Charlotte Fouché
email: charlotte.fouche@irt-jules-verne.fr

Guy Caverot
email: guy.caverot@basystemes.fr

Alexis Girin
email: alexis.girin@irt-jules-verne.fr

Stéphane Caro
email: stephane.caro@ls2n.fr

E Hocquard

FASTKIT: A Mobile Cable-Driven Parallel Robot for Logistics

niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Introduction

Cable-Driven Parallel Robots (CDPRs) form a particular class of parallel robots whose moving platform is connected to a fixed base frame by cables. The cables may be coiled/uncoiled by motorized winches allowing a contro system to adjust the cable lengths between the winch exit points and the cable attachment points on the platform. Appropriate length adjustment of cables allows one to control the degrees of freedom of the moving platform. CDPRs have several advantages such as mechanical simplicity and a potentially very large workspace. They have been used in several applications, e.g. heavy payload handling and airplane painting [START_REF] Albus | The NIST spider, a robot crane[END_REF], cargo handling [START_REF] Holland | Cable array robot for material handling[END_REF], warehouse applications [START_REF] Bruckmann | Design and realization of a high rack and retrieval machine based on wire robot technology[END_REF], large-scale assembly and handling operations [START_REF] Pott | Large-scale assembly of solar power plants with parallel cable robots[END_REF], and fast pick-and-place operations [START_REF] Kamawura | High-speed manipulation by using parallel wire-driven robots[END_REF]. Other possible applications include the broadcasting of sporting events, haptic devices Fortin2014, simulators [START_REF] Miermeister | The CableRobot simulator large scale motion platform based on cable robot technology[END_REF], and search and rescue deployable platforms [START_REF] Merlet | A portable, modular parallel wire crane for rescue operations[END_REF]. The performance improvement of CD-PRs is still a challenge because the cable unilaterality (cables can pull but cannot push) makes their analysis much more complex than parallel robots with rigid legs. Indeed, it is necessary to introduce cable models in the analysis, that are usually complex, non-linear, non-algebraic and computer demanding.

As we have seen CDPRs may perform various kinds of applications but they impose a strong requirement regarding the free circulation of the cables without interference with the environment. It is therefore reasonable to adjust their geometry (which has a large influence on the performances) according to the task requirements and the robot's environment. FASTKIT has aimed therefore at developing an mobile, deployable and autonomous CDPRs, called Mobile Cable-Driven Parallel Robots (MCDPRs), that can be adapted to the logistic task. From a mechanical point of view changing the geometry of CDPR is relatively easy either by moving the winches, by using pulleys to modify the location of the winches exit points or by changing the location of the cable attachment points on the load. Preliminary studies on reconfigurable CDPRs were performed in the context of the NIST RoboCrane project [START_REF] Bostelman | Cable-based reconfigurable machines for large scale manufacturing[END_REF]. Izard et al. [START_REF] Izard | A reconfigurable robot for cable-driven parallel robotic research and industrial scenario proofing[END_REF] also studied a family of RCDPRs for industrial applications. Beside the mechanical modularity, a challenge is to develop a strategy that will allow one to determine the best CDPR geometry for a given task to be fulfilled. Discrete reconfigurations where the locations of the cable exit points are selected from a finite set of possible values have been recently studied in [START_REF] Gagliardini | Discrete reconfiguration planning for cable-driven parallel robots[END_REF].

This paper deals with the design, modeling and performance analysis of a Mobile Cable-Driven Parallel Robot (MCDPR), named FASTKIT, developed in the framework of ECHORD++ FASTKIT project. FASTKIT project addresses an industrial need for fast picking and kitting operations in existing storage facilities while being easy to install, keeping existing infrastructures and covering large areas. Nowadays there exist several robotic solutions for logistic applications. One of the most popular automatic storage systems is the multi-shuttle system described in [START_REF] Gagliardini | Discrete reconfiguration planning for cable-driven parallel robots[END_REF], which guarantees high performance in terms of working rate. The main drawbacks of such systems are the high investment cost, the long installation time and the lack of flexibility.

Laser Scanner

Laser Scanner

Fig. 1 FASTKIT concept: A cable-driven parallel robot mounted on two mobile platforms Such systems are usually installed over large warehouses presenting a high entry and exit flow of storage boxes. In such conditions, an acceptable Return On Investment (ROI) is usually guaranteed. On the other hand, this solution is no longer possible or profitable for small warehouses, where there is no room for the installation of a large multi-shuttle system, or for warehouses characterized by a very low entry and exit flow of storage units, for which the high investment cost of a multi-shuttle solution is not justified.

The FASTKIT concept shown in Fig. 1 and developed in the scope of FASTKIT project is made up of CDPR mounted on two mobile platforms. As a result, it combines the autonomy of mobile robots with the advantages of CDPR, namely, large workspace, high payload-to-weight ratio, low end-effector inertia, deployability and reconfigurability. Moreover, CDPRs lead generally to low cost and easy maintenance solutions. Thanks to their characteristics, CDPRs can be used for different tasks such as the manipulation of heavy payloads or fast pick-and-place operations. Indeed, logistics is a very interesting field of application for CDPRs. Accordingly, FASTKIT aims at providing the user with a flexible and low cost logistic solution to equip small warehouses.

Therefore, the novelty of FASTKIT lies in the combination of autonomous mobile platforms and a CDPR. The main challenge in FASTKIT dealt with the design, modeling and assembly of the CDPR and the two mobile bases as well as the synchronization of their control laws.

This paper is organized as follows. Section 2 describes the main components, the control strategy and the architecture of the navigation stack of FASTKIT. Section 3 deals with to the kinematic modeling and kinematic performance evaluation of FASTKIT. The wrench capability of FASTKIT is assessed in Sec. 4. Some discussions and conclusions are given in Sec. 5. FASTKIT is capable of autonomously navigating in its environment to reach the task location referred to as a navigation mode. During this mode, the two Mobile Bases (MBs) are coupled together and act as a single working unit while the MP is fixed on the two MBs (see Fig. 3(a)). The twist of the MP and the passive mobile base is equal to the twist generated by the active mobile base. No cable motion is generated during the navigation mode. The second working mode, referred to as the task mode, deploys the system at the desired location such that the desired pick or/and place operation is achievable within the defined workspace. During this mode, the passive mobile base is static while the motion of the cables and the active mobile base is used to deploy the complete system (see Figs. 3(b) and 3(c)) 1 . It should be noted that during the task mode, FASTKIT is kinematically redundant due to the additional mobility of the active mobile base as explained in [START_REF] Rasheed | Optimal Kinematic Redundancy Planning For Planar Mobile Cable Driven Parallel Robots[END_REF].

FASTKIT Prototype

Main Components

The main components of FASTKIT are: (i) the main structure, (ii) the actuation system, (iii) its twelve pulleys, (iv) its MP equipped with a gripper, (v) Two s300 sick laser scanners, and (vi) two electrical cabinets. Here are the FASTKIT specifications:

• a desired workspace of 5 meters long by 2 meters high,

• a linear velocity of the moving-platform equal to 1 m/s, • a 7 kg payload.

The 2.4 m high main structure is made up of aluminum profile bars. The eight feet of the two structures are directly fixed on the top of the two mobile bases.

Actuation and Transmission System

The actuation system consists of eight identical modules, each module being composed a motor, a gearbox, an elastic coupling, a transmission shaft, two bearings and a winch, as shown in Fig. fig:FASTKITactsystem.

Based on the foregoing specifications, the required maximum cable tension and maximum cable velocity are equal to 45 N and 2 m/s, respectively. As a result, 8LVA23 B&R motors coupled with 8GP30 B&R gearboxes were selected. Table 1 gives the characteristics of the selected motors.

Pulleys

The pulleys have been realized in such a way that the friction is a minimum and the pulley to be sustainable. Hence, the pulley must be designed such that the cable can easily roll around the sheave and that the sheave itself can rotate freely around its The moving-platform has been designed to be capable of grasping, carrying and dropping a box of size 0.4 m × 0.3 m × 0.15 m, which is a typical size of the storage units used in logistics. Inner dimensions of the platform are 0.6 m × 0.36 m ×0.2 m. Figure 7(a) depicts the CAD model of the MP equipped with its gripper. Here, the mass of the moving-platform should be a minimum. The actual moving-platform, shown in Fig. 7, weighs 5 Kg. A Firgelli linear motor2 was used to realized the MP gripper. It should be noted that the MP tilt, required to grab and release boxes, is controlled through the cable lengths. Indeed, no exteroceptive sensor is used to manage the pick-and-place task and the MP tilt. Note that the good FASTKIT's repeatability allows us to execute this task in open-loop. On the other hand, ongoing work is dedicated to increase FASTKIT's accuracy in the initial MP positioning by means of cameras.

Moving-Platform and Gripper

Sick Laser Scanners

Each mobile base is equipped with a s300 sick laser scanner shown in Fig. 4. It has 3 m field range and 270 • scanning angle. This kind of scanner is usually used for obstacle avoidance and the navigation of the overall system described in Sec. 2.3.

Electrical Cabinets

The actuation system of the CDPR is controlled and powered by means of two electrical cabinets, one installed onto each mobile base. Those two cabinets are slightly different. Both electrical cabinets are composed of: (i) two variable speed drives; (ii) two 80V power supplies for the synchronous motors; (iii) one 24V power supply for the drives and (iv) one safety relay. In addition, the electrical cabinet embedded in the active mobile base is equipped with an industrial PC that controls the whole robot. Figure 8 shows the main electrical cabinet with the industrial PC. For the sake of compatibility, the speed drives, the power supplies and the industrial PC have been provided by the motor supplier, namely, B&R Automation™.

Control Strategy

The first control law that has been tested on the FASTKIT CDPR is a velocity control law. In order to implement it, the geometric and kinematic models of the CDPR are required. The velocity control is quite easy to implement and apply, but one major inconvenient arises: the cable tensions are not necessarily well distributed. Hence, during the task execution and because of ineluctable model errors, cables might get slack or too stretched. In order to cope with this undesired behavior, a torque control can be applied. First, one needs to estimate the intrinsic frictions (static, Coulomb and viscous frictions) for each motor. Once these values are established, they can be compensated in the final control law. Secondly, the optimal cable tension distribution should be computed to properly move the robot in its workspace. Several approaches to this problem are described in the literature [START_REF] Rasheed | Tension Distribution Algorithm for Planar Mobile Cable-Driven Parallel Robots[END_REF][START_REF] Lamaury | A tension distribution method with improved computational efficiency[END_REF][START_REF] Mikelsons | A real-time capable force calculation algorithm for redundant tendon-based parallel manipulators[END_REF]. The last strategy adopted in the scope of FASTKIT is described in Fig. 9. It aims to write the control algorithms in Matlab and then to communicate with the industrial PC through R.O.S. (Robot Operating System) 3 . A ROS package for communicating with the B&R™motors had already been implemented in [START_REF] Gagliardini | Discrete reconfiguration planning for cable-driven parallel robots[END_REF]. There is no need of code generator for Automation Studio. However, it should be noted that R.O.S. cannot run as fast as the B&R™industrial PC. Hence, some data might get lost during the communication and the system does no longer conform to an industrial standards in terms of robustness and response time.

Navigation

This section deals with the implementation of a navigation stack by means a set of interconnected algorithms. As shown in Fig. 10, those algorithms create altogether a complex decision making process:

Base driver: low-level software to control the velocity of the mobile platform ; Sensor driver: low-level software to get sensor information, here a scanner distance readings from the two lasers; Localization: software to localize the robot in the environment; Collision avoidance: software, with high priority, to compute free-path for the robot w.r.t. environement dynamics ; Path planning: global planner to compute shortest path to goal ; User Interface: visualization tool to control robot behaviour.

Therefore, the robot is able to model its environment, plan and move to a specific goal while avoiding obstacles.

The system uses ROS navigation algorithms. The core of the framework is to provide a set of standards, namely, sensors information, actuators control and transmission protocols, to allow users to share work and generic algorithms for multiple and various robotic systems. The reader is referred to as [START_REF] Quigley | Ros: an open-source robot operating system[END_REF] for further details about the ROS framework 4 . The key challenge for an autonomous mobile robot relies on the perception of its environment and the decision it makes accordingly. By means, from the robot point of view answer to the main questions: Where am I? Where am I going? How should I get there? Navigation can therefore be separated in three problematics: (i) mapping, (ii) localization and (iii) planning motion. For more details about autonomous navigation, the reader is referred to as [START_REF] Eskandarian | Handbook of intelligent vehicles[END_REF][START_REF] Philippsen | Autonomous navigation in dynamic environments[END_REF][START_REF] Brady | Robot motion: Planning and control[END_REF][START_REF] Howie | Principles of robot motion: theory, algorithms, and implementation[END_REF][START_REF] Steven M Lavalle | Planning algorithms[END_REF]. Figure 11 shows a result of planned trajectory in dynamic environment. The computed polygons can be seen in red. Note that if no polygon can be found, a single point still considers the obstacle. In this scenario, people were around the mobile base, hence the planned trajectory to go toward the red arrow (i.e. objective) required a step backward and a move toward the goal while avoiding obstacles. The obtained results are very promising. However, the computation cost remains high and requires fine tuning of parameters.

Kinematics

The kinematic performance of any robotic system can be analyzed from its first order kinematic model [START_REF] Roberts | On the inverse kinematics, statics, and fault tolerance of cable-suspended robots[END_REF] and the Available Twist Set (ATS). The ATS of CDPRs was defined in [START_REF] Lessanibahri | Twist Feasibility Analysis of Cable-Driven Parallel Robots[END_REF]. Thus, this section aims at presenting the kinematic model and ATS of FASTKIT. The mobile bases of FASTKIT are four-wheeled planar robots with two-DoF translational motions and one-DoF rotational motion, thus, they can be modeled as a virtual RPP kinematic chain between the base frame F 0 and the frame F b1 (F b2 , resp.) attached to active (passive, resp.) mobile base.

x [m ] y [ m ] z [m]
The cables attached to the active mobile base are named in ascending order as C 11 , C 21 , C 31 and C 41 respectively. Similarly, the cables connected to the passive mobile base are named in ascending order as C 12 , C 22 , C 33 and C 44 respectively. The twist 0 t cables P of the moving-platform as a function of cable velocities is expressed as follows:

A 0 t cables P = l, ( 1
)
where A is the (8 × 6) parallel Jacobian matrix, containing the actuation wrenches applied by the cables onto the moving-platform. The twist 0 t P = [ω ω ω, ṗ] T is composed of the platform angular velocity vector ω ω ω = [ω x , ω y , ω z ] T and linear velocity vector ṗ = [ ṗx , ṗy , ṗz ] T , expressed in F 0 . 0 t cables P denotes the platform twist only due to the cable motions. l is a eight-dimensional cable velocity vector. Here, Eq. ( 1) can be expressed as:

A 1 A 2 0 t cables P = l1 l2 , (2)
where ˙l1 = [ l11 , l21 , l31 , l41 ] T and l1 = [ l12 , l22 , l32 , l42 ] T . A 1 and A 2 are expressed as:

A 1 =     [( 0 b 11 -0 p) × u 11 ] T u T 11 [( 0 b 21 -0 p) × u 21 ] T u T 21 [( 0 b 31 -0 p) × u 31 ] T u T 31 [( 0 b 41 -0 p) × u 41 ] T u T 41     , A 2 =     [( 0 b 12 -0 p) × u 12 ] T u T 12 [( 0 b 22 -0 p) × u 22 ] T u T 22 [( 0 b 32 -0 p) × u 32 ] T u T 32 [( 0 b 42 -0 p) × u 42 ] T u T 42     (3)
where A 1 and A 2 contain the actuation wrenches associated with cables connected to the active and passive mobile bases, respectively. l11 to l42 denote the velocity of cables C 11 to C 42 . 0 b 11 to 0 b 42 denote the Cartesian coordinate vectors of anchor points B 11 to B 42 in F 0 . 0 u 11 to 0 u 42 denote the unit vector alongs cable C 11 to C 42 . 0 p is the Cartesian coordinate vector of the geometric center of the moving-platform expressed in frame F 0 .

First Order Kinematic Model of FASTKIT

The twist 0 t j P of the moving-platform due to the cables and the mobile bases is expressed as [24]:

A 1 A 2 t P = A 1 b1 Ad P J b1 0 0 A 2 b2 Ad P J b2 qb1 qb2 + ˙l1 ˙l2 , (4)
where b1 Ad P ( b2 Ad P , resp.) is called the adjoint matrix, which represents the transformation matrix between twists expressed in F b1 (F b2 , resp.) and twist expressed in F P ,

b1 Ad P = I 3 0 3 -b1 rP I 3 , b2 Ad P =

I 3 0 3 -b2 rP I 3 ( 5
)
b1 rP ( b2 rP , resp.) is the cross-product matrix of vector ---→ O b1 P ( ---→ O b2 P, resp.) expressed in F 0 shown in Fig. 12(a). From Eq. ( 4), qb1 ( qb2 , resp.) is the three-dimensional joint velocity vector of the virtual RPP kinematic chain for the active (passive, resp.) mobile base, expressed as:

qb1 =   θ1 ρ11 ρ21   , qb2 =   θ2 ρ12 ρ22   (6)
J b1 (J b2 , resp.) is the (6 × 3) serial Jacobian matrix of the active (passive, resp.) mobile base, namely,

J b1 = k 0 0 3 0 3 k 0 × 0 p 0 R b1 i 0 0 R b1 j 0 , J b2 = k 0 0 3 0 3 k 0 × 0 p 0 R b2 i 0 0 R b2 j 0 ( 7
)
where i 0 , j 0 and k 0 denote the unit vector along x 0 , y 0 and z 0 axes, respectively. 0 R b1 ( 0 R b2 , resp.) is the rotation matrix between frame F 0 and frames F b1 (F b2 , resp.). Equation ( 4) can be expressed in a matrix form as:

At P = B b qb + ˙l ( 8
)
At P = B q (9)
where B = [B b I m ] is a (8 × 14) matrix while q = [ qb ˙l] T is a fourteen-dimensional vector containing all joint velocities. As a result, Eq. ( 9) represents the first order kinematic model of FASTKIT.

FASTKIT Available Twist Set

The Available Twist Set (ATS) is used to characterize the twist capabilities of the moving-platform. The ATS of FASTKIT is obtained from its joint velocity limits and first order kinematic model. The joint velocity limits of the active mobile base are the following:

-0.2 rad.s -1 ≤ θ1 ≤ 0.2 rad.s -1 (10) -0.2 m.s -1 ≤ ρ11 ≤ 0.2 m.s -1 (11) -0.2 m.s -1 ≤ ρ21 ≤ 0.2 m.s -1 (12)
Once FASTKIT is deployed, its passive trailer is stabilized and does not move. Therefore, its linear and angular velocities are null, i.e., θ2 = 0 rad.s -1

(13) ρ12 = 0 m.s -1 (14) ρ22 = 0 m.s -1 (15)
From Tab. 1, the cable velocity limits are the following: From the ATS of FASTKIT in the configuration shown in Fig. 12(a), the maximum angular (linear, resp.) velocities of the MP about (along, resp.) x, y and z axes are shown in Fig. 13. It is noteworthy that the twist capacity of the moving-platform is higher when the MBs are moving than when the MBs are fixed.

-2 m.s -1 ≤ l11 , l21 , l31 , l41 , l12 , l22 , l32 , l42 ≤ 2 m.s -1 (16)

Wrench Feasibility

The classical techniques used to analyze the workspace of CDPRs are wrenchclosure workspace (WCW) [START_REF] Gouttefarde | Analysis of the wrench-closure workspace of planar parallel cable-driven mechanisms[END_REF][START_REF] Lau | Wrench-Closure Workspace Generation for Cable Driven Parallel Manipulators using a Hybrid Analytical-Numerical Approach[END_REF] and wrench-feasible workspace (WFW) [START_REF] Gouttefarde | Interval-analysis-based determination of the wrench-feasible workspace of parallel cable-driven robots[END_REF][START_REF] Ruiz | ARACHNIS : Analysis of Robots Actuated by Cables with Handy and Neat Interface Software, Cable-Driven Parallel Robots[END_REF]. To analyze the workspace of FASTKIT, WFW has been choosen as it is more relevant from a practical viewpoint. WFW is defined as the set of platform poses for which the required set of wrenches can be balanced with wrenches generated by the cables, while maintaining the cable tension within the defined limits [START_REF] Gouttefarde | Interval-analysis-based determination of the wrench-feasible workspace of parallel cable-driven robots[END_REF]. For a given pose, the set of wrenches a mechanism can generate is defined as available wrench set (AWS), denoted as A .

The AWS for CDPRs only takes into account the Static Equilibrium (SE) of the moving-platform. In contrast, for FASTKIT to be in SE, both mobile bases and the moving-platform should be in SE [START_REF] Rasheed | Available wrench set for planar mobile cable-driven parallel robots[END_REF]. Its a necessary and a sufficient condition for the FASTKIT to be in SE. Thus this section aims at presenting the AWS of FASTKIT by taking into account the SE of both the moving platform and the mobile bases.

Static Equilibrium of the Moving-Platform

The Static Equilibrium (SE) of the moving platform is expressed as [START_REF] Kawamura | A new type of master robot for teleoperation using a radial wire drive system[END_REF][START_REF] Hiller | Design, analysis and realization of tendon based parallel manipulators[END_REF]:

Wt + w e = 0, (17)
where W is a (6 × 8) wrench matrix mapping the cable tension vector t ∈ R 8 onto the wrench applied by the cables on the end-effector expressed as: (18) r 11 to r 42 are the vectors pointing from the reference point P of the moving platform to the cable anchor points B 11 to B 42 . w e denotes the external wrench applied to the end effector expressed as:

W = u
w e = f e m e ( 19
)
where f e = [ f x e , f y e , f z e ] T and m e = [m x e , m y e , m z e ] T respectively denote the external forces and moment applied by the MP. The cable tension vector is bounded between a minimum tension vector t and a maximum tension vector t, t ≤ t ≤ t.

(20)

Static Equilibrium of the Mobile Bases

The SE of both the mobile bases is defined by the moment generated at the boundaries of the mobile base footprint formed by their respective wheels, referred to as the tipping constraints. For the active mobile base, the footprint is formed by joining the contact points of the wheels with the ground C 11 to C 41 in ascending order of the wheels numbering (See Fig. 12a). Similarly, the footprint of the passive mobile base is formed by joining the contact points C 12 to C 42 in ascending order. Let L C 11 denote the boundary of the footprint between the two consecutive contact points of the wheels C 11 and C 21 . Let u C 11 be the unit vector along L C 11 . For the active mobile base to be in SE, the moment m C 11 generated about L C 11 should be always lower than zero, namely,

m C 11 = u T C 11 ((g 1 -c 11 ) × w g1 ) + u T C 11 ((c 11 -b 11 ) × t 11 ) + u T C 11 ((c 11 -b 21 ) × t 21 ) + u T C 11 ((c 11 -b 31 ) × t 31 ) + u T C 11 ((c 11 -b 41 ) × t 41 ) ≤ 0, (21)
where c 11 and g 1 denote the Cartesian coordinate vectors of contact point C 11 and the center of gravity G 1 , respectively. w g1 denotes the weight vector of the active mobile base. Similarly for the active mobile base to be in SE, the moment generated about each boundary of the footprint must be negative. Therefore, the tipping conditions of the active mobile base are expressed as follows:

          m C 11 m C 21 m C 31 m C 41           =              u T C 11 ((g 1 -c 11 ) × w g1 ) + u T C 11 ((c
             ≤ 0 4 , (22)
where u C 21 , u C 31 , and u C 41 are the unit vectors along the lines L C 21 , L C 31 and L C 41 , respectively. Similarly, for the passive mobile base to be in SE, the tipping conditions takes the form:

          m C 12 m C 22 m C 32 m C 42           =              u T C 12 ((g 2 -c 12 ) × w g1 ) + u T C 12 ((c 12 -b 12 ) × t 12 ) + u T C 12 ((c 12 -b 22 ) × t 22 ) +u T C 12 ((c 12 -b 32 ) × t 32 ) + u T C 12 ((c 12 -b 42 ) × t 42 ) u T C 22 ((g 2 -c 22 ) × w g1 ) + u T C 22 ((c 22 -b 12 ) × t 12 ) + u T C 22 ((c 22 -b 22 ) × t 22 ) +u T C 22 ((c 22 -b 32 ) × t 32 ) + u T C 22 ((c 22 -b 42 ) × t 42 ) u T C 32 ((g 2 -c 32 ) × w g1 ) + u T C 32 ((c 32 -b 12 ) × t 12 ) + u T C 32 ((c 32 -b 22 ) × t 22 ) +u T C 32 ((c 32 -b 32 ) × t 32 ) + u T C 32 ((c 32 -b 42 ) × t 42 ) u T C 42 ((g 2 -c 42 ) × w g1 ) + u T C 42 ((c 42 -b 12 ) × t 12 ) + u T C 42 ((c 42 -b 22 ) × t 22 ) +u T C 42 ((c 42 -b 32 ) × t 32 ) + u T C 42 ((c 42 -b 42 ) × t 42 )              ≤ 0 4 , (23)

Available Wrench Set of FASTKIT

The AWS (A ) of FASTKIT is defined by Eq. ( 17), respecting the cable tension limits (Eq. 20) and the tipping conditions defined by Eqs. ( 22) and ( 23). There A can be expressed as:

A = f m ∈ R 6 | f m = Wt t t, t ≤ t ≤ t, m C11 ≤ 0, m C21 ≤ 0, m C31 ≤ 0, m C41 ≤ 0, m C12 ≤ 0, m C22 ≤ 0, m C32 ≤ 0, m C42 ≤ 0 . (24)
where f = [ f x , f y , f z ] T and m = [m x , m y , m z ] T denote the forces and moments exerted by the cables onto the moving platform, namely,

f = -f e , m = -m e . (25)
From the AWS of FASTKIT in the configuration shown in Fig. 12(a), the maximum absolute moments (forces, resp.) that the platform can support about (along, resp.) x, y and z axes are illustrated in Fig. 14. It can be noted that the wrench capability of the moving-platform is lower when the MBs are moving than when the MBs are fixed.

Conclusions and Future Work

This paper dealt with the design, modeling and performance analysis of a Mobile Cable-Driven Parallel Robot (MCDPR), named FASTKIT, developed in the framework of ECHORD++ FASTKIT project. FASTKIT project addressed an industrial need for fast picking and kitting operations in existing storage facilities while being easy to install, keeping existing infrastructures and covering large areas. The FASTKIT prototype consists of two mobile bases that carry the exit points of the CDPR.

FASTKIT is capable of autonomously navigating in its environment to reach the task location referred to as a navigation mode. During this mode, the two Mobile Bases (MBs) are coupled together and act as a single working unit while the MP is fixed on the two MBs. The twist of the MP and the passive mobile base is equal to the twist generated by the active mobile base. No cable motion is generated during the navigation mode. The second working mode, referred to as the task mode, deploys the system at the desired location such that the desired pick or/and place operation is achievable within the defined workspace. During this mode, the passive mobile base is static while the motion of the cables and the active mobile base is used to deploy the complete system. It should be noted that during the task mode, FASTKIT is kinematically redundant due to the additional mobility of the active mobile base as explained in [START_REF] Rasheed | Optimal Kinematic Redundancy Planning For Planar Mobile Cable Driven Parallel Robots[END_REF].

The main components, the control strategy and the architecture of the navigation stack of FASTKIT were presented in this paper. Both the hardware design and the software architecture of the prototype were discussed. First, the Cable-Driven Parallel Robot (CDPR) and mobile based were studied separately. It turns out that the combination of a CDPR with two mobile bases leads to several issues such as: (i) the hardware + software assembly of the CDPR with the mobile bases; (ii) the definition of a control law to properly manage the robot motion in all its phases, and notably the deployment phase.

The main outcome of this paper is the demonstrator of a MCDPR. This demonstrator is capable of navigating in unknown environments, positioning in front of the shelves and picking some boxes on the shelf. The kinematic performance and the wrench capability of FASTKIT have also been assessed in some specific configurations.

Therefore, a compact and reconfigurable CDPR that can work both in a fully constrained configuration and in a suspended configuration have been developed. Customized pulleys for the CDPR have designed and realized to reduce cable friction. Two electromagnetic links between the two mobile bases that rigidly connect them during the navigation phase were also implemented. From a software view point, a navigation algorithm for the mobile CDPR based on existing open-source libraries was written. A global control law that synchronizes the CDPR actuators with the active mobile base during the deployment phase was synthesized too.

There are still several open issues to be solved in the future such as: (i) the kinematic redundancy planning of FASTKIT and (ii) the wrench analysis of MCDPRs while considering both tipping and sliding conditions of their mobile bases.

Fig. 2

 2 Fig. 2 FASTKIT prototype

Fig. 3

 3 Fig. 3 FASTKIT working modes

Table 1 Fig. 5 Fig. 6

 156 Fig. 4 FASTKIT actuation and transmission system

Fig. 7

 7 Fig. 7 Moving-platform with its gripper grabbing a storage unit box

Fig. 8

 8 Fig.8The FASTKIT electrical cabinet mounted onto the active mobile base

Fig. 10

 10 Fig. 10 Architecture of the Fastkit navigation stack. Green boxes represents software packages, names of packages are in brackets

Fig. 11

 11 Fig. 11 Visualization of the planned trajectory towards a goal. The robot is represented by the green box. The planned trajectory is represented by the blue arrow, red polygons represent obstacles and red arrow shows the position objective. Black area represent the inflation around obstacles for the cost function that guarantees collision avoidance

Fig. 12

 12 Fig. 12 FASTKIT kinematics

Fig. 13

 13 Fig. 13 Kinematic performance of FASTKIT

where u C 12 ,

 12 u C 22 , u C 32 , and u C 44 are the unit vectors along the lines L C 12 , L C 22 , L C 32 and L C 42 , respectively.

Fig. 14

 14 Fig. 14 Wrench capability of FASTKIT

  11 × u 11 r 21 × u 21 r 31 × u 31 r 41 × u 41 r 12 × u 12 r 22 × u 22 r 32 × u 32 r 42 × u 42

	11	u 21	u 31	u 41	u 12	u 22	u 32	u 42
	r

  11b 11 ) × t 11 ) + u T C 11 ((c 11b 21 ) × t 21 ) +u T C 11 ((c 11b 31 ) × t 31 ) + u T C 11 ((c 11b 41 ) × t 41 ) u T C 21 ((g 1c 21 ) × w g1 ) + u T C 21 ((c 21b 11 ) × t 11 ) + u T C 21 ((c 21b 21 ) × t21 ) +u T C 21 ((c 21b 31 ) × t 31 ) + u T C 21 ((c 21b 41 ) × t 41 ) u T C 31 ((g 1c 31 ) × w g1 ) + u T C 31 ((c 31b 11 ) × t 11 ) + u T C 31 ((c 31b 21 ) × t 21 ) +u T C 31 ((c 31b 31 ) × t 31 ) + u T C 31 ((c 31b 41 ) × t 41 ) u T C 41 ((g 1c 41 ) × w g1 ) + u T C 41 ((c 41b 11 ) × t 11 ) + u T C 41 ((c 41b 21 ) × t 21 ) +u T C 41 ((c 41b 31 ) × t 31 ) + u T C 41 ((c 41b 41 ) × t 41 )

Videos on FASTKIT YouTube channel: https://www.youtube.com/channel/ UCJ8QRs818MBc8YSbn-bZVjA

https://www.firgelliauto.com/products/mini-track-actuator\ #ptab-specifications

http://www.ros.org/

Ros navigation stack [online]. http://wiki.ros.org/navigation. Accessed: 2015-06-11.

Acknowledgements This research work is part of the European Project ECHORD++ FASTKIT dealing with the development of collaborative and Mobile Cable-Driven Parallel Robots for logistics. Moreover, Centrale Nantes is dutifully acknowledged for the doctorate thesis financial support provided to the second author of the paper.


Guillaume Duboisdindien

Cyril Grandin

Dominique Boutet

Anne Lacheret-Dujour

A Multimodal corpus to check on pragmatic competence for Mild Cognitive Impaired aging people

Keywords:

Approche sur corpus des compétences pragmatiques et

multimodales des personnes âgées présentant un trouble cognitif léger.

Clinicians have a duty to develop their professional practice through an evidence-based clinical approach whose main objective is to reconcile clinical practice with the best evidence from research [START_REF] Dollaghan | The handbook for evidencebased practice in communication disorders[END_REF]. In the case of speech-language pathology, clinicians consider themselves very limited in this approach [START_REF] Lof | Science-based practice and the speech-language pathologist[END_REF]McCurtin, 2011], especially for patients with mild cognitive impairment [START_REF] Mungas | Heterogeneity of cognitive trajectories in diverse older persons[END_REF][START_REF] Hopper | An evidencebased systematic review on cognitive interventions for individuals with dementia[END_REF][START_REF] Morello | Language and communication non-pharmacological interventions in patients with Alzheimer's disease: a systematic review. Communication intervention in Alzheimer[END_REF] and more specifically when it comes to assessing or supporting language functions [START_REF] Cummings | Pragmatic disorders[END_REF]. The studies focusing on Mild Cognitive impairment require longitudinal corpora i) to understand the naturally occurring evolutions in subjects, ii) the implication of the cognitive reserve in each individual, and iii) to take advantage of these parameters as evidence for research and earlier rehabilitation. We aim to show the benefits of linguistic and interactional scientific investigation methods through fragile aging, for health professionals and everyday caregivers.

Résumé

Cet article présente un corpus vidéo d'analyse multimodale dont l'objectif principal est de modéliser et prédire les effets du vieillissement en situation de trouble cognitive léger sur les compétences pragmatiques et communicationnelles. Nous prenons comme observable les marqueurs pragmatiques verbaux et non-verbaux. Cette démarche, à l'interface des sciences du langage, des sciences cognitives et de la médecine réadaptative (l'orthophonie) s'inscrit dans un processus de recherche longitudinale en situation écologique (entretiens menés par des intimes des personnes âgées). Nous présenterons en première partie de cet article les caractéristiques langagières, cognitives et sociales du vieillissement dans son continuum jusqu'aux troubles cognitifs léger et pathologiques. En seconde partie nous développerons l'intérêt d'une approche multimodale sur corpus notamment pour renseigner l'accompagnement non-médicamenteux et enrichir les connaissances orthophoniques. Enfin nous présenterons le corpus depuis sa conception expérimentale à ses résultats préliminaires qui concernent deux locutrices de l'étude âgées de plus 75 ans et qui présentent un trouble cognitif léger. Les conclusions générales indiquent qu'avec l'avancée en âge, les marqueurs pragmatiques verbaux revêtent préférentiellement une fonction interactive permettant ainsi aux personnes avec TCL de maintenir les relations intersubjectives avec l'interlocuteur. Par ailleurs, au niveau non-verbal, les manifestations gestuelles sont de plus en plus mobilisées dans le temps avec une préférence pour les marqueurs pragmatiques non-verbaux à fonction référentielle et à fonction interactive. L'une permettant de compenser les manques du mot, difficultés de planification, accrocs discursifs; l'autre optimisant et maintenant l'interaction avec l'interlocuteur. Les cliniciens ont le devoir de développer leur pratique professionnelle par l'approche clinique basée sur des données probantes dont l'objectif majeur est de concilier la pratique clinique et les meilleures preuves issues de la recherche [START_REF] Dollaghan | The handbook for evidencebased practice in communication disorders[END_REF]. Pour le cas de l'orthophonie, les cliniciens s'estiment très limités quant à cette approche [START_REF] Lof | Science-based practice and the speech-language pathologist[END_REF]McCurtin, 2011] en particulier pour les patients avec TCL [START_REF] Mungas | Heterogeneity of cognitive trajectories in diverse older persons[END_REF][START_REF] Hopper | An evidencebased systematic review on cognitive interventions for individuals with dementia[END_REF][START_REF] Morello | Language and communication non-pharmacological interventions in patients with Alzheimer's disease: a systematic review. Communication intervention in Alzheimer[END_REF] et plus spécifiquement lorsqu'il s'agit d'évaluer ou soutenir les fonctions langagières [START_REF] Cummings | Pragmatic disorders[END_REF]. L'approche en TCL nécessite des corpus longitudinaux pour comprendre i) les évolutions naturellement en oeuvre chez les sujets, ii) renseigner l'implication de la réserve cognitive chez chaque individu et iii) tirer avantage de ces paramètres comme bases de données attestées pour la recherche et la rééducation précoce. Nous désirons montrer quels sont les avantages des méthodes d'investigation scientifiques linguistiques et interactionnelles à travers le vieillissement fragilisé, pour les professionnels de la santé et les aidants au quotidien.

Introduction

The monitoring of elderly patients with cognitive and physiological multifactorial disorders at home or in healthcare institutions, increasingly encourages caregivers to consider the language resources of these patients, while aiming at maintaining communication and promoting their autonomy in a benevolent and medication-free environment. Current assessment tools focus mainly on losses, particularly in the language system, with limited reference to language use and to the resources preserved by the elderly. Those gaps hamper the effectiveness of speechlanguage interventions which rely on levels of evidence still limited in scientific ressources [START_REF] Dollaghan | The handbook for evidencebased practice in communication disorders[END_REF]. Our study offers an overview of a a multimodal analysis focusing on Mild Cognitive Impaired People by mining longitudinal corpus built on recorded intergenerational exchanges in ecological situation, with an emphasize on the identification of pragmatic markers. By definition, pragmatic markers (PM) are rooted in the discussion situation and aim to maintain discourse consistency [START_REF] Brinton | Discourse Markers[END_REF]. We propose an approach to language aging in a continuum ranging from normal to pathological aging, in which we identify a profile of people at the frontier of potential dementia.

We hypothesize that the identification of multimodal pragmatic markers, produced by people who are a priori at risk of developing dementia or of anchoring themselves in pathological aging, can help us to characterize inter-individual variations and significant compensatory communication skills in the aging process. We postulate that verbal and gestural pragmatic markers are relevant indicators for studying the subject's entrenchment in discourse [START_REF] Davis | Sociolinguistics, Language and Aging -Chapter[END_REF][START_REF] Duboisdindien | Des aînés hors normes ? Interroger le continuum du vieillissement langagier à travers une perspective interactionnelle. Atypies langagières de l'enfant à l'âge adulte[END_REF]Duboisdindien, Bolly, & Lacheret-Dujour, 2017;Hamilton, 1999]. We also consider the influence of interactional context on the use of these markers and what they can reveal about the emotional states and language skills of the elderly participant with respect to the proposed task: autobiographical recollection of recent or past events. The aim of our study is not to determine a quantitative threshold of multimodal pragmatic markers for the diagnosis of dementia, but rather to give insights in what is at stake for elderly people with the use or misuse of these markers and their pragmatic functions all along the cognitive alteration.

We implemented the data processing following [START_REF] Kennedy | An introduction to Corpus Linguistics[END_REF] recommendations on the balance to be found between an ecological study (i.e. non-invasive and spontaneous), and technical constraints. In doing so, we obtained a sufficient representativeness of the studied population, comparability between the sub-components of the corpus and the proposed tasks, as well as interoperability between the tools in order to systematize the analysis. The data processing consists of 6 steps : (i) development of an interview protocols inspired both by those written in CorpAGEst [START_REF] Bolly | The multimodal CorpAGEst corpus: Keeping an eye on pragmatic competence in later life[END_REF] and our clinical experience, (ii) selection of participants, collection of field data for 14 months, sampling phase, digitization of video and audio data and their editing on the ORTOLANG scientific platform, (iii) transcription and alignment of audio data, (iv) annotation of audio and video data, (v) a unimodal and multimodal analyses of data, and (vi) systematic storage of original sources and annotated files.

All the tasks proposed during the semi-structured interviews as well as the collection protocol correspond to the framework imposed by the ethics committee of the Psychological Sciences Research Institute of Louvain-la-Neuve University in Belgium.

Our data include 20 hours of video recording corresponding to 36 interviews with nine speakers (mean age: 83 years; average score at Moca-Test: 20/30). After subsampling, we ended with a total of 6 hours (30 minutes per speaker) for this specific study. From the results of our first analyses on the multimodal communicative features that characterize language evolution in aging, we expect that verbal deficits are accompanied/compensated by an increase in non-verbal acts with a specialization of both verbal and non-verbal pragmatic functions.

The use of corpus in natural interaction informs us on different levels. The more complex the verbal content becomes, the more the elderly person uses referential and deictic gestures and intersubjective solicitations addressed to the interlocutor (signs of co-agreement, shared knowledge, interactive gaze) in order to keep communicating. This corpus delivers a different point of view compared to other investigations published so far on aging psychology and mostly based on data generated in laboratory conditions. Our approach allows us to grasp authentic interactions produced in natural exchange situations with their intrinsic complexity and enables a fine-grained functional analysis of productions in various modality. The project is in line with the work of C.T. Bolly [2013Bolly [ -2015]], which focuses on healthy aging. The trends observed in this scope commit us to thinking of language as a resource for detecting dementia signs and understanding compensation strategies. Therefore, this work appears as an outstanding opportunity for clinical practitioners such as speech pathologists, physiotherapists, and psychomotor therapists to develop care protocols relying on verbal and nonverbal communication in aging. The significance of pragmatic marker functions in elderly speech, as well as approaches induced by linguistics and specifically pragmatics, contributes to broaden the urgent request to develop non-medicinal psychosociable methods, and evaluation tools for vulnerable old people to ensure their well-being.

Results on two case studies:

Constance is an 86-year-old woman; she lives alone in her own home. After a few years as a cleaner, she stayed at home to raise her children. Her sons and neighbors come to visit her daily. She does not require medical care and benefits from physiotherapeutic care. Mild cognitive impairment appeared about three years ago, according to her relatives. Her regular lapses of memory led the family to consult a neurologist in April 2015 who did not detect any dementia but concluded that the cognitive fragility was moderately worsening over time. Constance's predominant communication complaint is lexical deficits (word finding problems). The following graph shows the set of scores for longitudinal cognitive assessments conducted every 4 months.

As for Tristane, she is an 81-year-old autonomous woman. She does not require any special medical care. However, her family has alerted the general practitioner regarding memory issues affecting both discussions and daily life (forgetting recent discussions and family events: birth, death, marriage). The scores for the longitudinal cognitive assessments performed every 4 months are presented in the following graph. The medical diagnosis for Alzheimer's disease was given this year after two and a half years of follow-up (approximately every four months) with memory evaluation There has been a gradual decline in the scores of the screening Moca-Test up to a problematic threshold. Complete neurological examinations were performed in April 2015 without revealing any AD or related syndrome. Constance is located in the clinical category of MCI patients. After exporting the VPMs data of the two speakers out from Elan, we first evaluated the quality of the corpus and validated it by carefully checking the presence and if necessary the wellfoundedness of missing data.

The data set that can finally be used for analysis includes 3931 VPM distributed as follows:

In order to smooth the "speaker" effect and to take into account a possible idiosyncratic differential of the verbal content (prolific subject vs. taciturn subject), we chose to work in frequency. Still with this concern of normalization and in order to minimize the effects of extrinsic co-factors (different emotional state between two interviews), we decided to proceed to a normalization in frequency by task.

Thus, for each speaker, the data will be expressed in frequency of use of each functional domain among all the VPMs expressed during a task.

General characteristics of the VPM device: Use of VM (in frequencies per task and speaker)

The figure below gives an overview of the data thus generated: The interactive aspect prevails. Constance and Tristane use interpersonal VPMs to solicit the interlocutor and their shared knowledge in order to ensure interaction is maintained and remains anchored in discourse (in particular by inserting coagreement VPMs). Thus, this situation of interaction disturbed by language fragilities (naming deficits, disfluencies, doubts) is dealt with by the speaker but can also be dealt with by relatives if they are attentive to these indicators of cognitive discomfort. Once these elements have been identified, they could be valuable resource tools for clinicians in order to intervene at times when tiredness occurs or if the theme addressed requires a major effort in the exchange. These markers would alleviate the feeling of powerlessness of older speakers who could overcome the situation by transmitting a positive and committed image of themselves in speech. The clinician must be sufficiently sensitive to these interaction marks. In order to characterize the system upstream, and to reveal any underlying structures, we then used a hierarchical clustering strategy (based on Pearson's correlation and Ward's D2 aggregation criterion), the idea being to graphically visualize the similarities and di-similarities between the different classes of VPM according to the way they are used by the different speakers. The heatmap below presents the results of this analysis. For a given cell, the warmer the colour is, the more important the use of a class of VPM during a given interview is for the speaker in question (and vice versa when it is coloured in cold blue).

We see here (Figure 9) that: -The interactive VPMs are generally more mobilized, whoever the speaker and whatever the exercise, when compared with the other classes of VPM, corroborating the previous observations. -The way the interactive and ideational VPM types are used is relatively homogeneous across tasks.

-The structure is more unclear concerning the VPM of structuring and expressive types.

-AgeSC3 makes greater overall use of interactive VPMs -AgeIT1 makes greater use of expressive and structuring VPMs.

In addition to this analysis, we also characterized non-verbal manifestations in Constance's speech. To do this, we counted the NVPMs (of hands) in r2 and r4, which allowed us to note an increase of 22% of NVPMs produced by Constance between these two interviews.

Graphic 2 : Frequency of VPM versus NVPM between interview 2 and interview 4 with ageSC3

Given these preliminary results, it remains to be seen whether NVPMs would increase over time in seniors' discourse. In comparison, these NVPMs are more numerous than the VPMs produced within these two corpora. This finding may indicate a tendency for Constance to produce more gestures during interaction while verbal information content decreases.

In the third and fourth interviews, referential gestures tend to take a deictic orientation by taking precedence over representational gestures.

In an exchange about odor recollections, Constance is not able to name the stimulus, which is the smell of lavender. She explains to her son that she recognizes the smell but the word does not cross her mind. She ends up looking into her direct environment and pointing her finger at the bouquet of lavender placed in her kitchen while at the same time verbalizing her discomfort:

Constance : « euh…comment… euh… [pointing at the bouquet]» Jules : « de la lavande oui ! » Constance : « oui de la lavande c'est ça … ah ! » * Constance: "hum…How can i…hum" [pointing at the bouquet] Jules: "a bunch of lavander, yeah !" Constance: "yeah that's it, a bunch of lavander … ah !" (see illustration 1.b. in this article : Example of a deictic gesture: pointing the bunch of lavender (in ageSC3_r3_S5-00:59))

In the light of recent studies [START_REF] Schiaratura | Verbal and gestural communication in interpersonal interaction with Alzheimer's disease patients[END_REF]Carlomagno et al., 2005] we assume that representational gestures are also becoming too cognitively expensive for Constance. Indeed, it is a complex activity that involves both semantic memory (e.g. encyclopedic knowledge, language, and concepts) and executive functions that govern the cognitive mechanisms required to perform gestures and fine motor skills. Moreover, the overall situation is stressful for Constance experiencing naming and frustration for several months. Yet willingness to communicate is still there but manifests itself in a simpler form.

Another interesting orientation concerns the developmental approach of communication throughout life. We can hypothesize that this duality between deficit phenomena and compensatory phenomena is to be analyzed under a retroactive light of human communication. During their development, young children gradually experiment with gesture and communication skills that will enhance their language acquisition. The development of referential gestures is gradually achieved through the deictics scale first (finger/hand pointing, joint attention and gaze designation), and then through ideational gestures that require greater cognitive skill and greater refinement on the semantic level as the young child develops his knowledge. During the aging process, and especially during the fragile and problematic aging, these gestural manifestations take the opposite path but always sign this need to communicate and share emotions. The cognitive stock could be involved in this process because it would contain all the neuronal capacities to cope with cognitive difficulties. Throughout their life experiences, the elderly have internalized a set of verbal and nonverbal behaviors that would allow them to compensate and maintain interactions in the event of difficulties in an individualspecific process. These attempts would be all the more valued and effective if the interlocutor, either close, clinician or allcoming, proves to be supportive and empathetic.

Conclusion

This study sheds light on a point of view differing from the classical investigation methods proposed so far in aging psychology (for the most part based on data produced in laboratory conditions). Our approach give room for the expression of authentic interactions in natural exchange situations that can be observed as closely as possible. Our study develops several innovative aspects. First, the pragmatic competence of elderly people with mild cognitive deficits is still a marginal topic in linguistic. Secondly, it proposes a methodology based on the reasoned and explicit annotation of multimodal data in natural spontaneous exchange situations, which can therefore be used for other research perspectives.

Third, the multidisciplinary dimension of this study, at the crossroads of pragmatics, discourse analysis, psychology of aging and multimodality, offers diversified avenues for the scientific community and -we hope -may encourage clinical research to develop corpus-based approaches. Indeed, the community is engaged in soliciting the humanities and social sciences for a better understanding of the language continuum and in developing clinical models favoring diagnosis and therapeutic support in an evidence-based approach.

We propose a continuous approach to language aging, and identify a singular profile for MCI people within this frame. The trends we highlight commit us to thinking of language as an interesting resource for detecting early markers of dementia. Without talking about pathological aging, it is necessary to observe the profiles of the participants in our study and to analyze the distinctions that exist between the common and heterogeneous pathways that they take over time. This has always been done after the diagnosis has been made. However, it seems crucial to carefully consider these pragmatic markers before the establishment of any obvious clinical signs in order to enrich research on pathological aging.

Finally, it is worth developing a multimodal approach to account for the non-verbal compensatory elements within the deficit elements of these MCI people.

At the end of this discussion on the communicational traits that would characterize this in-between profile in language aging, we postulate that verbal deficits are accompanied by an increase in non-verbal acts with a specialization of these nonverbal manifestations as the deficits increase. The more verbal content becomes difficult to represent manually, the more the elderly person relies on deictic gestures and intersubjective solicitations addressed to the interlocutor (signs of coagreements, shared, interactive knowledge) in order to maintain the communication.

In a long term perspective, considering language in its plural dimension offers a relevant anchorage as soon as we build interactive corpuses. We have seen that speech in action is usually accompanied by communicative gestures. Follow-up researches on this topic would be beneficial in order to point the compensatory or facilitating nature of the gesture within the disturbed language, and to identify possible predictors of dementia like Alzheimer's disease (AD). AD is characterized by a progressive deterioration of intellectual abilities, memory loss, attention difficulties and language disorders (particularly at the semantic level). The person's deep identity is altered, accompanied by behavioural and mood disturbances. These changes alter communication skills and disrupt not only the patient's life, but also social relationships.

Currently, the few studies addressing these questions [START_REF] Glosser | Gestural communication in Alzheimer's disease[END_REF]Taler & Philipps, 2008 ;[START_REF] Schiaratura | La communication non verbale dans la maladie d'Alzheimer[END_REF][START_REF] Taler | Comprehension of grammatical and emotional prosody is impaired in Alzheimer's disease[END_REF][START_REF] Davis | Sociolinguistics, Language and Aging -Chapter[END_REF] engage research to develop models considering the communication of the elderly with TCL or MA: i) in its multimodal dimension i) interactive ii); iii) and in approaches toured on its manifestations at the level of discourse and more generally at the level of the pragmatic and social dimension. We emphasize the importance of considering nonverbal communication in its interactive dimension in people with LCH. If non-verbal and adaptive cues are not perceived by the interlocutor within repeated daily activities -care, meals, friendly exchange, activity -then the person is less and less likely to interact in this modality, at the risk of increasing the symptoms a little more by the effect of social and emotional comorbidity.

  The entire article is located at the following link : Guillaume Duboisdindien, Cyril Grandin, Dominique Boutet et Anne Lacheret-Dujour, « A Multimodal corpus to check on pragmatic competence for Mild Cognitive Impaired aging people », Corpus [En ligne], 19 | 2019, mis en ligne le 01 janvier 2019, URL : http://journals.openedition.org/corpus/4295

Figure 8 :

 8 Figure 8 : General characteristics of the VPM device: Use of VM (in frequencies per task and speaker)

Figure 9 :

 9 Figure 9 : Hierarchical clustering: Speakers vs. Use of VPM (in frequencies) per task

Acknowledgements :

The authors would like to thank :

-The European project CorpAGEst -People Marie Curie Actions (PIEF-GA-2012-328282) and Dr Catherine T. Bolly for her precious support and these evenings of rich discussions about aging, ethics and pragmatics.

-The France Médéric Alzheimer National Association and Paris Lumière (PLUM) for their confidence in our researches.

-MoDyCo lab UMR 7114 and Paris Nanterre University for their support.

-We warmly thank: Dr Pierre-François Roux, postdoctoral fellow at the Nuclear Organization and Oncogenesis unit -Pasteur Institute (Paris) for assisting us with our statistical analyses and his brilliant sense for pedagogy.

-Special thanks to Dr Marion Blondel, current CNRS research fellow and Coralie Vincent, engineer and head of the experimental platform, members at the SFL lab, Pouchet, UMR 7023 (Paris), to believe in us.

-We would like to express our special thanks to the Pr L. Degand's team from Louvain la Neuve University and Dr L. Meurant from Namur University, for your sense of reception, your help and your kindness.