Adnane Houbbadi
email: adnane.houbbadi@ifsttar.fr

Rochdi Trigui
email: rochdi.trigui@ifsttar.fr

Serge Pelissier
email: serge.pelissier@ifsttar.fr

Eduardo Redondo-Iglesias

Tanguy Bouton
email: tanguy.bouton@transdev.com

A quadratic programming based optimisation to manage electric bus fleet charging

Keywords: electric bus fleet, optimisation, quadratic programming, charging infrastructure, electric vehicle supply equipment

The use of electric buses (EBs) is expected to increase significantly in the coming years. Uncontrolled charging of EBs can affect not only the power grid (grid instability, harmonic pollution) but also the operating cost. This paper introduces an optimal charging strategy based on charging schedule planning and modulation of charging power for a fleet of electrical-powered buses. The optimal charging strategy allows minimising the charging cost as well as the load power variations using quadratic programming. The proposed quadratic programming can significantly reduce the computation time and simultaneously handle a large bus fleet. First results indicate a significant reduction in customer energy bills while avoiding potential penalties due to peak loads.

Introduction

The transport sector in Europe is responsible for significant air pollutant emissions, which became a major public health issue. The European Union (EU) has committed to cut its emissions of greenhouse gases (GHG) to 40% below 1990 levels by 2030 (European Commission, 2018).

Electro-mobility will better address the challenges associated to urban transport with high energy efficiency and low GHG emissions. Therefore, the use of electric buses (EBs) is a key aspect to achieve these objectives and a way to reduce the GHG emissions. However, managing electro-mobility in local public transport is not an easy task. A large-scale deployment of EBs will have a great impact on the electrical system, generating network congestion problems and requiring more electricity generation to cover the peak demand [START_REF] Dietmannsberger | Modelling the electrification of bus depots using real data: consequences for the distribution grid and operational requirements[END_REF].

On the other hand, over cost of EB purchase compared to thermal buses should be paid back by reducing the operation cost that is sensitive to electricity price.

To optimise the EB fleet charging, a quadratic programming optimisation has been developed in this work. The capability of modulating and scheduling the charging power allows then adopting smart strategies in order to reduce the charging cost and the load power variations with regard to technical constraints including maximum power limits.

This paper is organised as follows. In Section 2, we introduce the charging infrastructure and the electrical power system. In Section 3, we discuss our proposed approach for smart charging of EBs. Then, we present and discuss our results for a case study with different operating scenarios. In Section 7, we draw some conclusions and present some future work.

2 Infrastructure and charging system

Electric vehicle supply equipment

An electric vehicle charging infrastructure, also called electric vehicle supply equipment (EVSE), is an infrastructure that provides electric energy, energy conversion, monitoring and safety functionality according to international standards from the International Electrotechnical Commission (International Electrotechnical Commission, 2017).

In this paper, we only deal with heavy vehicles (electric buses) that are connected to the main power grid through an external dedicated off-board AC/DC and DC/DC converter that supplies DC power directly to the EB's battery. Control and protection functions and the vehicle charging cable are installed permanently in the installation. The considered charging infrastructure is equipped with a power transformer, which lowers voltage and supplies the conversion system. The conversion system consists of an AC/DC converter and a DC/DC charger, which is dedicated to a charging point. The generalised system architecture is presented in Figure 1. The DC/DC charger is managed by a central control system. This controller checks the conversion equipment and carries out the communication with the EB to perform the charging according to a standardised communication protocol (PLC) EN 61851-23 (International Electrotechnical Commission, 2017). A standard socket type Combo 2 CCS makes the hardware connection between the EB and the charger.

During the charging process, several information needed are exchanged in PLC format between the bus and the charger (International Electrotechnical Commission, 2017).

Communication and charging protocol via CCS/COMBO

The International Standard IEC 61851-1 defines 4 charging modes for light EV: modes 1, 2, 3 are for AC charging with slow and fast charging up to 43 kW, while charging of EBs is governed by mode 4, which uses DC power charging beyond 50 kW. Currently, there exists two types of DC charging systems: the CCS2 (Combined Charging System) COMBO used on this paper and ChaDeMo charger [START_REF] Lewandowski | Interference analyses of electric vehicle charging using PLC on the control pilot[END_REF]. The most common charging method employed for charging lithium-ion batteries is the constant current/constant voltage (CC/CV) charging algorithm.

During the CC sequence, a constant current is applied to charge the battery until the battery voltage reaches a maximal value defined as the cut-off voltage at which CV begins. CV charging is used to limit the current and thus prevent the battery from overcharge. The charging process stops when the charging current reaches a small value. Figure 2 shows the charging profile of the CC/CV [START_REF] Redondo-Iglesias | Global model for self-discharge and capacity fade in lithium-Ion batteries based on the generalized eyring relationship[END_REF]. The CC and CV phase duration depends on initial state-of-charge (SoC) and on charging power. The CV phase lasts about 20 min for a 1 C charging rate for lithium iron phosphate cells [START_REF] Eddahech | Determination of lithium-ion battery state-ofhealth based on constant-voltage charge phase[END_REF] and takes even less time at low charging rates. During the CCS 2 COMBO protocol charging, a master-slave configuration is used (battery being the 'master' and charger the 'slave') to share information and set the maximum charging current limit based on the power rating of the EV and the charger.

In case of 'smart charging', the 'slave-charger' has to be able to modulate the power with a maximum limit remaining below the one requested by the 'master-battery'. The charger and battery continuously negotiate and set a charging current setpoint command every 200 ms based on the charging algorithm of the battery management system, which is any electronic system that manages the cell or battery pack charging.

The charger can make a new setpoint request to change the current and battery has to accept or decline this request. If the request is accepted, battery changes the current set point and the charger can charge the battery based on the negotiated set point as shown in Figure 3 [START_REF] Mouli | Implementation of dynamic charging and V2G using Chademo and CCS/Combo DC charging standard[END_REF]. For the period (t 1 + t 2 ), a buffer capacity is required either to store the energy from the grid or to provide the energy required.

Methodology and system modelling

This part introduces a methodological approach (Figure 4) to develop an optimal charging strategy for a fleet of EBs in urban transport. This approach uses quadratic programming to search for optimal plans according to the objective function (by minimising the charging cost as well as the load variations) while taking into account the technical constraints (actual operating constraints, constraints of the power grid and the charging station). The optimisation methodology has been implemented in the Matlab/Simulink environment. During the smart charging process, information on the operating bus constraints (number of buses, initial SoC, the target SoC, the amount of energy required, arrival and departure time, maintenance period) has to be filled.

Other constraints related to the charging infrastructure and power grid are added. For instance, the subscribed power, the maximum charging power delivered by the charger and the electricity cost. The optimisation algorithm attributes an optimal charging power profile for each bus depending on objectives and respecting these constraints. Once the optimisation is finished, the optimal charging power profile is applied to a converter model that represents the charger and a battery model. The aim is to check if the battery received enough energy and if its temperature is not too high. These models are presented in Figure 5.

Converter model

The efficiency of an EV charger depends on the efficiency of various internal components. Electrical power comes from the grid and is converted several times, from the AC supply to the DC/DC converter and from the DC/DC converter to the battery, as we presented in Figure 1.

To stay in an acceptable simulation time, we used some experimental results of a quick charger test efficiency as converter model to represent the AC/DC and the DC/DC converter power losses [START_REF] Genovese | On the energy efficiency of quick DC vehicle battery charging[END_REF]. These data represent the average charger efficiency during the charging tests for different charging power.

In a first approach, until we develop a specific converter model, we will use five charger efficiency values corresponding to five charging power ranges based on the experimental results.

Battery model

Several equivalent electrical models are proposed in the literature [START_REF] Mousavi | Various battery models for various simulation studies and applications[END_REF]. The simplest model to describe the behaviour of an accumulator is the OCV + R model, which associates a voltage source and a resistance. This model is very effective to describe phenomena in a simplified way. However, it does not represent the dynamic behaviour of a battery. More complex models consist of a voltage source in series with different dipoles. Different evolutions of the OCV + R model are possible through the addition of one or several capacitors C or a CPE ('constant phase element') to represent the dynamic behaviour of the battery (Long [START_REF] Lam | A practical circuit-based model for Li-ion battery cells in electric vehicle applications[END_REF]. However, it appears for the purpose of this work that an OCV + R model provides the necessary accuracy with very short computation time.

The battery model used in this work contains a previously developed electric model based on VEHLIB [START_REF] Trigui | Systemic modelling of hybrid vehicles in order to predict dynamic performance and energy consumption building the VEHLIB library of models[END_REF] which is a systemic vehicle simulation software, developed by IFSTTAR-LTE. The simplified electrical model is shown in Figure 6. 4 Problem formulation

Quadratic programming optimisation

As part of this work, an optimisation methodology to identify the optimal charging strategy for a fleet of EBs has been developed. The methodological approach is based on both charging scheduling and power modulation in order to minimise the charging cost as well as the load power variations by taking into account operating constraints.

Several methods for smart charging of electric vehicles were compared through an extensive literature review [START_REF] Hu | Electric vehicle fleet management in smart grids: a review of services, optimization and control aspects[END_REF]. [START_REF] Hu | Electric vehicle fleet management in smart grids: a review of services, optimization and control aspects[END_REF] have compared nine optimisation methods used for smart charging of electric vehicles with different objectives. These methods include linear programming, quadratic programming, dynamic programming, mixed integer linear programming, mixed integer nonlinear programming, stochastic programming, heuristics and metaheuristics.

In terms of computational time, the linear programming (LP) is generally the fastest one. However, in terms of applicability, it cannot be used in this problem because of the non linearity of the objective function. A quadratic programming (QP) was compared to the linear programming (LP) [START_REF] Sundstrom | Flexible charging optimization for electric vehicles considering distribution grid constraints[END_REF] in order to minimise the total charging cost of 50 vehicles. Results showed that the calculation time using the QP is then increased compared to the one using LP and showed that the gain in accuracy of the results between using LP and QP is minor. [START_REF] Clement-Nyns | The impact of charging plug-in hybrid electric vehicles on a residential distribution grid[END_REF] indicated that the computational time for dynamic programming is higher compared to QP. The study in [START_REF] Sousa | Day-ahead resource scheduling in smart grids considering vehicle-to-Grid and network constraints[END_REF] indicated that the computational time of non-linear programming is highly dependent of the number of EVs. Stochastic programming [START_REF] Clement-Nyns | The impact of charging plug-in hybrid electric vehicles on a residential distribution grid[END_REF], heuristics and metaheuristics [START_REF] Sousa | A hybrid simulated annealing approach to handle energy resource management considering an intensive use of electric vehicles[END_REF], robust and model predictive control [START_REF] Di Giorgio | Electric vehicles charging control in a smart grid: a model predictive control approach[END_REF], particle swarm optimisation [START_REF] Soares | Application-specific modified particle swarm optimization for energy resource scheduling considering vehicle-to-grid[END_REF] are generally longer and are more suitable to complex problem difficult to implement.

The choice of the optimisation algorithm strongly depends on the form of the objective functions. In this paper, regarding the quadratic form of our objective function with linear constraints, QP has been selected for dealing with the optimisation problem expecting a fast calculation time and sufficiently accurate results.

Pre-optimisation process

Before the optimisation process, one need to determine the amount of energy required to reach the target SoC of the battery. We use the battery model with different charging power at different SoC values to determine an average charging efficiency that will be used during the optimisation.

Different charging power was applied over 30 min as an input in the battery model. The battery efficiency represent the average value for different initial SoC values ranging from 10% to 90%. The results are reported in Table 1.

Different charging power was applied in [START_REF] Genovese | On the energy efficiency of quick DC vehicle battery charging[END_REF] for different initial SoC values to determine the charger efficiency. The results are reported in Table 2.

Optimisation design variable

The quadratic optimisation problem refers to the optimisation of a quadratic objective function of several variables. In this work, the optimisation variable represents the charging power P of the bus fleet in an (n × m) matrix:

1,1 1,2 1, 2,1 2,2 2, , ,1 ,2 , 1 . . . ( ) 1 .
. .

m m n n nm p p p p p p i n j m p p p ⎛ ⎞ ⎜ ⎟ ⎜ ⎟ ≤ ≤ ⎧ ⎫ ⎜ ⎟ = = ⎨ ⎬ ≤ ≤ ⎜ ⎟ ⎩ ⎭ ⎜ ⎟ ⎜ ⎟ ⎝ ⎠ … … … … … i j P p ( 2
)
where n is the total number of EB and m the number of time slots, , i j p is the charging power for EB i during a time slot j .

Objective functions

The aim is to minimise the overall cost of charging as well as the load power variations. This problem can be formulated as a follow:

objective cost load f f f = + (3)
The charging cost is expressed as a linear function:

cost , 1 1 n m j i j f t c = = = ×Δ× ∑∑ i j p (4)
where , i j p denotes the charging power of EB i during a time slot j (kW), t Δ represents the time-slot of 30 min (h), j c the electricity price during a time slot j (€/kWh)

The load power variations is expressed as a quadratic function:

2 , 1 1 n m load i j f = = = ∑∑ i j p (5)
The squared values of the charging power are used to penalise load variations and promote a smooth average load demand.

The total weighted objective function

We normalised these two functions to introduce a weighting factor α that would tend to prioritise the charging cost. Thus, this problem can be formulated as a quadratic program:

objective , , 1 2 1 n m j i j f tc α = = = ×Δ× + × ∑∑ i j i j p p (6)

Intermediate variables

During the quadratic optimisation problem, the optimisation variable P is subjected to several constraints. These can take various forms such as bound constraints, equality and inequality constraints. The constraints influence in one case all elements of the optimisation variable matrix P and in other case, they are applied to certain rows and columns of the matrix P . Therefore, we introduced two intermediate variables that represent a submatrix of the optimisation variable P . We defined a submatrix { } j P that represents the charging power for all the buses during a time slot j :

{ } { } 1, 2, , . 1 . j j n j p p j m p ⎛ ⎞ ⎜ ⎟ ⎜ ⎟ ⎜ ⎟ = ≤ ≤ ⎜ ⎟ ⎜ ⎟ ⎜ ⎟ ⎝ ⎠ j P (7)
We defined a submatrix { } i P that represents the charging power of a bus i during the total time slots:

{ } ( ){ } ,1 ,2 , . 1 i i im p p p i n = ……… ≤ ≤ i P (8)

Constraints and variable boundaries

During the optimisation, the maximum charging power for each individual DC/DC charger imposes a bound constraint to all elements of the optimisation variable

P , m a x 1 0 1 i n p j m ≤ ≤ ⎧ ⎫ ≤ ≤ ⎨ ⎬ ≤ ≤ ⎩ ⎭ i j p (9)
The charging infrastructure subscribed power imposes an inequality constraint to the submatrix { } j P (10). A denotes an all-ones (1 × n) matrix, { } j P is an (n × 1) refers to the charging power for all the buses during a time slot j:

{ } subscribed A p × ≤ j P ( 10
)
The operating bus constraints (the bus arrival and departure time) impose an equality constraint to the submatrix

{ } i P { } 0 T B× = i P (11)
B denotes an (1 × m) matrix that will take 0 between the bus arrival and departure time and 1 in the other case, { } T i P (the transpose of the matrix { } i P ) is an (m × 1) matrix that represents the charging power of a bus i during the total time slots.

The operating bus constraint (number of km) will define the final battery SoC to reach. It also impose the amount of energy required to reach the target SoC as an equality constraint to the submatrix { } 1 and2.

Case study

A case study was performed to simulate the smart charging of an EB fleet. The considered station is capable of supporting the simultaneous recharge of 10 EBs. The schematic of the setup is shown in Figure 7. The EBs will operate an existing conventional bus line. An AC/DC converter draws the power request from the grid to the DC/DC converter. Each DC/DC converter powers a charger where standard Combo CC2 is used. The EB fleet is charged only at the depot within a period ranging from 6:00 pm to 7:30 am. Because of the large time range during charging (more than 12 h between the starting time and the end time), we chose a time step t Δ of 30 min that gives a total of m = 27 time slots, which results in a reasonable sized search space. The ambient and initial battery temperatures are fixed to 25°C. These data correspond to the input of our optimisation model. We chose variable electricity costs in order to analyse the behaviour of our optimisation algorithm towards a dynamic charging scenario. The high cost period is from 6:00 pm to 8:00 pm and 6:30 am to 7:30 am, whereas the low-cost period starts from 8:00 pm to 6:30am. The simulation parameters are shown in Table 3.

Each charging point can provide up to 60kW for charging a bus and the maximum subscribed power represent the sum of all the maximum power delivered by each charging point. The battery cell characteristics and battery pack specifications are shown in Tables 4 and5. 6 Results and analysis

Optimisation of the bus fleet charging using a specific scenario

We are going to optimise one single EB with specific operating constraints to see if the optimisation algorithm trends towards optimal values. First, information on the operating bus constraints (number of buses, initial SoC, arrival and departure time, the length of the trip (km), maintenance time) and EVSE constraints has to be filled. The optimisation algorithm attributes the optimal charging power for the EB fleet to minimise the charging cost as well as the load power variations while respecting these constraints. Once the optimisation is finished, the optimal charging power goes through a converter model that represents the charger and a battery model in order to check if the battery received enough energy and if its temperature is not too high.

The results of quadratic optimisation in Figure 8 show that the optimal charging power agrees perfectly with the variation of the electricity costs while respecting the subscribed power. The used weighting factor ( 0.7) α = tend to charge the EB during all the low-cost period with an average load demand of 40 kW. The optimisation with a larger size of bus fleets (10 EBs) with the same constraints has been performed. It shows the same results and follows the same trend as one single EB.

We present an example of one optimal solution among others with a weighting factor (α = 0) in Figure 9. The use of this weighting factor makes the objective function totally dependent on the charging cost. The result shows that the algorithm charges during the low cost period without considering the mean power. The fact of disabling the quadratic part of the objective function makes that the only criterion is electricity cost. Other solutions are equivalent to this one in terms of electricity cost, for example, the constant power profile shown in Figure 8.

The optimisation parameters and constraints are shown in Table 6.

Optimisation of the bus fleet charging using different scenarios

In scenario No. 2, we are going to optimise a fleet of two buses by adding some variant operating constraints to see if the optimisation algorithm will converge while respecting all the operating constraints presented in Table 7. The weighting factor was fixed to (α = 0.7). The results of quadratic optimisation in Figure 10 show that the optimal charging power charges the EB 2 during all the possible charging period (when the bus is available) with an average power of 50 kW. Once the EB 2 charging period is filled, the algorithm set up the EB 1 charging period in a way to avoid exceeding the subscribed power during the low-cost period. In scenario No. 3, we are going to optimise 4 EBs by adding some operating constraints quite similar to an existing conventional bus line while imposing a subscribed power of 100 kW. The weighting factor was fixed to (α = 0.7).

The results of quadratic optimisation in Figure 11 show that the optimal charging power starts to charge the most constrained bus which is the EB 4, then the algorithm try to fill the other EBs charging profile in a way to avoid exceeding the subscribed power during the low-cost period. Subject to several constraints, once the algorithm filled all the low-cost period, it has been forced to charge during the high cost period otherwise the power would exceed the subscribed power as we can see for EB 1, EB 2, and EB 3.

Baseline comparison and annual cost review

To illustrate the potential economic gain, we will compare a baseline situation to an optimised charge strategy. The baseline represents one typical behaviour by charging the EB with a maximum power of 60 kW as soon as possible, ignoring cost and maximum subscribed power, until it is fully charged.

We will use the same operating constraints as the scenario no. 3 excepting the number of the buses in the fleet that goes from 4 to 10. The weighting factor was fixed to (α = 0.7). The overshooting of subscribed power will be optionally charged at a rate of 0,060 €/kWh as a penalty. The optimisation constraints results are shown respectively in Tables 9 and10.

The optimisation parameters and constraints are shown in Table 8. The results of quadratic optimisation in Table 10 and Figure 12 show that the optimal solution reduces the charging cost significantly with only 10 s of computing time.

The optimal solution has been able to achieve a 6% reduction in the annual charging cost compared to the baseline solution and 17% compared to the baseline solution + the over-limit charges if we consider that the overshooting of subscribed power is charged at a rate of 0.060 €/kWh.

Conclusion and future works

This paper introduces an optimal charging strategy based on charging schedule planning and modulation of charging power for a fleet of electrical-powered buses. A case study has been implemented to illustrate the smart charging of an electric bus fleet during the night at the bus depot. The first results showed a coherent behaviour of the algorithm and a short computational time that makes possible to deal with large fleet of several hundreds buses.

In future work, we would like to extend the method in order to perform a conjoint optimisation of the cost together with the battery lifetime. Actually, the calendar ageing mechanisms require paying attention to the moments of the charge in relation to temperature and SoC of the batteries.

The end of the charging process has also to be carefully studied, in particular the CV phase that could have an impact on the time slots needed for a full recharge. Finally, a comparison between different methods that allow a multi objective optimisation will be necessary to achieve an acceptable trade-off between the optimum quality and the computational time.

Figure 1

 1 Figure 1 System architecture of the EVSE (see online version for colours)

Figure 2

 2 Figure 2 Charging profile the CC/CV charging algorithm for a lithium-ion battery (see online version for colours)

Figure 3 .

 3 Figure 3. Charging current request via CCS 2 (see online version for colours)

Figure 4

 4 Figure 4 Smart charging methodology (see online version for colours)

Figure 5

 5 Figure 5 Converter and battery models

Figure 6

 6 Figure 6 Battery equivalent circuit

  an all-ones (1 × m) matrix, { } T i P is an (m × 1) matrix that represents the charging power of a bus i during the total time slots (W), T Δ the time-slot of 30 min (h), and Capacity Bat denotes the total battery capacity (Ah), ch η is the average charger efficiency (%), bat η is the average battery efficiency (%), OCV is the open-circuit voltage of the battery (Volt). The average values are from Tables

Figure 7

 7 Figure 7 Charging infrastructure (see online version for colours)

Figure 8

 8 Figure 8 Optimal charging schedules scenario 1 (α = 0.7) (see online version for colours)

Figure 9

 9 Figure 9 Optimal charging schedules scenario 1 (α = 0) (see online version for colours)

Figure 10

 10 Figure 10 Optimal charging schedules scenario 2 (see online version for colours)

Figure 12

 12 Figure 12 Optimal charging schedules scenario No. 4 (see online version for colours)

Table 1

 1 Battery model voltage and efficiency

	Charging power	Battery efficiency (%)
	10 kW		99.7
	20 kW		99.4
	30 kW		99.2
	40 kW		99
	50 kW		98.7
	60 kW		98.5
	Average value	99
	Table 2	EB charger efficiency
	Charging power	Charger efficiency (%)
	3 kW		86
	16 kW		91.6
	22 kW		92.2
	43 kW		92.6
	50 kW		92.6
	Average value	91

Source:

[START_REF] Genovese | On the energy efficiency of quick DC vehicle battery charging[END_REF]

Table 3

 3 Simulation parameters

	Parameters

Table 4

 4 Battery cell specifications

	Parameters		Value
	Battery type		LFP
	Nominal energy/capacity	64 Wh/20 Ah
	Nominal voltage	3.2 V
	Table 5	Battery pack specifications
	Parameters		Value
	Nominal energy/capacity	311 kWh/540 Ah
	Nominal voltage	576 V

Table 6

 6 Scenario 1: optimisation constraints

	Smart charging	Operating constraints scenarios
	Number of bus fleet	1
	Initial SoC	10%
	Arrival time	18:00
	Departure time	07:30
	Length of the trip	200 km
	Target SoC	100% SoC
	Maximum charging power per bus	60 kW
	Subscribed power (total maximum power)	60 kW

Table 7

 7 Scenario 2: Optimisation constraints

		Number of bus fleet
	Smart charging	EB1	EB 2
	Initial SoC	20%	10%
	Arrival time	18:00	23:00
	Departure time	07:30	05:00
	Length of the trip	100 km	200 km
	Target SoC	50%	100%
	Maximum charging power per bus	60 kW	60 kW
	Subscribed power (total maximum power)	60 kW

Table 10

 10 Scenario 4: optimisation parameters and results

	Smart charging	Baseline solution	Optimal solution
	Optimisation	-		Quadratic programming
	Objective	-		Charging cost + load power
				variations
	Number of bus fleet	10		10
	Charging power	Fixed 60 kW	0 -> 60 kW
	Computing time	-		10 s
	Subscribed power	300 kW		300 kW
	Maximal charging power	600 kW		300 kW
	Annual consumption below the	527 MWh		742 MWh
	subscribed power
	Annual consumption beyond the	215 MWh		0 MWh
	subscribed power
	Total annual consumption	742 MWh		742 MWh
	Charging cost annual review	Without penalty	31 k€	29 k €
		With penalty	35 k€

ParisTech in 2016. In 2017, he joined IFSTTAR as a PhD student. His work is in collaboration with TRANSDEV and focuses on the optimisation of an electric bus fleet charging. Rochdi Trigui received his PhD in Electrical Engineering in 1997 from the Polytechnic National Institute of Lorraine. He then worked for one year as an Associate Researcher at PSA Peugeot Citroën. Since 1998, he is Full Researcher (senior since 2012


Joseph Adam's House

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Parallèlement, la dénonciation de la ville délétère s'amplifie au xix e siècle, avec la croissance des villes et les préoccupations d'hygiène publique. Les réquisitoires contre le surpeuplement des quartiers populaires, la vétusté des logements et la stagnation de l'air vicié encouragent les médecins à recommander les cures d'air, comme on prescrit un séjour en sanatorium aux tuberculeux. Cette cure d'air exige évidemment de résider loin des miasmes de la ville ou dans des quartiers périphériques agrémentés de parcs. Parallèlement, l'audience du naturisme va croissant. Il prône un retour à la na-ture fondé sur un autre mode de vie. La ville n'est plus alors seulement nocive, mais on l'accuse en plus de dépraver les moeurs 3 . La mise en paysage de la nature dans l'esthétique du xviii e siècle, les phi-losophies et les nouveaux usages du jardinage font de l'habitat temporaire un jeu. Ce jeu, qui consiste à habiter par intermittence et en condition de précarité la nature, est concomitant de l'avènement des pédagogies nou-velles, de L'Emile de Jean-Jacques Rousseau aux scoutismes et autres mou-vements de jeunesse 4 . Il est également un des catalyseurs du tourisme mo-derne dès le tournant du xx e siècle, avec les loisirs sportifs, l'extension du camping, la randonnée et les pratiques sportives de pleine nature 5 . à l'occa-sion de la diffusion de ces activités largement tournées vers la jeunesse, l'abri de loisirs devient un élément constitutif des sociétés occidentales et de leurs mentalités : que l'on pense aux congés payés, aux utopies commu-nautaristes, aux villages recomposés, à l'hygiénisme social, aux figures d'ex-plorateurs et d'aventuriers… qui sont autant de circonstances où se re-jouent les rapports nature-culture propres à l'Occident 6 .

Un objet de référence de la culture occidentale

La grande variété des abris de loisirs et de leurs dénominations témoigne de la variabilité des expériences qui les caractérisent, des groupes sociaux qui les portent et des dispositifs de sociétés qu'ils incarnent. Dans les années 1840, de nouveaux mots font leur entrée dans la langue française : pergola, cabanon, tente abri, tente baraque… La littérature anglo-saxonne met l'accent sur ces nouveaux objets techniques, dans une société où le Comment expliquer le renouveau d'intérêt pour ces objets ? Le terrain a été préparé en amont par les philosophes et les voyageurs. Avec l'essor des pédagogies nouvelles, mais aussi le thème récurrent du bon sauvage, l'Occident a exalté les valeurs du dénuement et de la vie précaire comme voies d'accès au bonheur. Le roman champêtre -de G. Sand à E. Guillauminreprendra ces thèmes en montrant comment la part magique de la nature s'exerce encore au contact de la vie simple. Face à l'enfermement urbain et à la rationalisation du travail industriel, les utopistes inventent des mondes où l'abri devient un espace refuge et fantasmagorique. Phalanstères, jardins ouvriers, cités-jardins, camps pédagogiques pour jeunes enfants et adolescents incarnent désormais un faisceau d'expériences jusqu'alors décrit dans le conte ou le roman. Entre la nécessité d'une réforme sociale de l'habitat populaire au xix e siècle et l'importation du chalet dans les cercles de la bourgeoisie à la campagne, à la montagne ou en front de mer, la petite habitation individuelle s'impose vite comme un horizon à développer dans la société française 8 . Cette réforme de l'habitat en France, en partie amorcée par F. Le Play et ses congénères, va trouver d'importants relais dans les milieux philanthropiques. à l'instar du chalet luxueux de la bourgeoisie, l'ouvrier aura à disposition un abri de jardin faisant office de résidence secondaire. Le défi architectural sera poursuivi en pleine période du Front populaire, autour d'innovateurs tels que Le Corbusier, Charlotte Perriand, Jean Prouvé ou 7. Outre l'émergence de nombreuses sociétés d'excursion, la langue française redéfinit les termes de bivouac et de caravane en les étendant aux activités ludiques associées aux grands espaces : montagne, désert, mer.

8. Perrot Michelle (dir.), Histoire de la vie privée, tome 4 : De la Révolution à la grande guerre, Paris, éditions du Seuil, 1987.

Pierre Jeanneret. Ces derniers feront le lien entre les chalets préfabriqués et autres maisons démontables exposés au récent salon des Arts ménagers, et la politique de développement des loisirs populaires en collaboration avec les associations de jeunesse 9 . La massification des vacances, à la fin des an-nées 1960, marquera une étape essentielle dans la diffusion et la reproduc-tion technique à grande échelle de ces abris de loisirs. La profusion des clubs de vacances, l'idée de stations de vacances intégrées ou encore le dé-veloppement massif du camping feront de l'abri à vocation de loisirs un élément incontournable du paysage.

Aujourd'hui, le marché des abris réservés aux loisirs n'a fait que s'accroître. L'entreprise Bénéteau a vu, ces dernières années, son activité de production de voiliers doublée par celle de confection de mobile homes 10 . On estime aujourd'hui à 1,5 million le nombre de foyers français équipés d'une caravane, alors qu'ils sont 180 000 à disposer d'un camping-car. Les tours opérators développent la formule d'hébergement nomade sous la yourte ou le tipi en explorant les sentiers empruntés par Stevenson. Un camping aux abords du château de Versailles propose à sa clientèle une nuit dans les arbres avec vue sur le site. De nouvelles entreprises spécialisées dans la confection haut de gamme de cabanons et de cabanes ont émergé dans le sud de la France, reconfigurant ainsi les abris traditionnels des pê-cheurs et des chasseurs. Ce marché n'est pas le seul à désigner cet engoue-ment. Les débats contemporains sur les sans-abri, les débats politiques au-tour des gens du voyage, l'importante fréquentation des magasins de bricolage et des salons ménagers, l'élan retrouvé pour la décoration des intérieurs, le succès cinématographique du camping… nombreux sont les indices qui font de l'abri un vecteur de droit aux loisirs dans nos sociétés contemporaines. La réduction de la surface habitable liée à l'inflation de l'immobilier dans les grandes métropoles rapproche de plus en plus l'amé-nagement de la domus 11 des caractéristiques de l'abri.

Un objet qui déroge aux catégories et aux normes instituées

Cette multiplication des formes d'abris de loisirs n'est pas sans interroger. à cet égard, le sociologue Joffre Dumazedier décrit cet avènement comme la manifestation d'une pensée sauvage diffuse 12 . à l'instar des artistes tels que Picasso ou Kokoschka fascinés par le primitivisme, l'abri de loisirs semble exprimer une magie souterraine que l'on pensait perdue face à la rationalité de nos modes de vie. Cette manifestation des forces vitales, telluriques qui prennent racine dans l'abri de loisirs perdure lorsque (rappelant ici sa racine de cabinet de travail) il devient un espace de retrait pour les intellectuels. Pour Thoreau dans sa ferme délabrée de Walden en 1854, comme pour Emerson, Nathaniel Hawthorne ou John Muir 13 , l'abri est avant tout un espace sanctuarisé qui permet de mieux ressentir la nature et de prendre une distance avec le monde. Ces pionniers de l'écologie, membres du Sierra Club et fondateurs de l'Association des Parcs naturels nationaux, font encore entendre leurs voix aujourd'hui à travers les chartes pour des abris de loisirs de qualité, mais aussi pour des normes écologiques d'habitation plus en harmonie avec la nature. Les maisons en bois ou en paille sont là aussi les témoins discrets d'un objet multiforme qui aide à penser les fondations du social. Ainsi, les mouvements de retour à la nature contemporains semblent rappeler ceux du Larzac en 1970, des hippies des années 1960 ou de la Route en 1950, proches à leur tour des mouvements de jeunesse de l'entre-deux-guerres. Les mouvements passent, et malgré son caractère temporaire et éphémère, l'abri semble rester, se métamorphosant sans cesse à la manière d'un phénix.

Toutes ces formes d'abri ont en commun d'être des demeures précaires, éphémères, de petites dimensions, réalisées à partir d'une variété infinie de matériaux de toute sorte, et de s'inscrire dans une relation étroite avec la nature ou le plein air, y compris lorsque la situation d'implantation est urbaine, comme le montrent les jardins ouvriers ou l'expérience de l'implantation architecturale des clubs de jeunes dans les années 1960, par exemple. Il semble que ces abris de loisirs expriment un goût pour la vie simple, une forme de relâchement des codes sociaux et une forte sociabilité, une rupture du temps et de l'espace, une coupure avec le quotidien et les contraintes domestiques, un désir d'évasion et enfin un rapport privilégié avec la nature.

Leur statut juridique et leur existence sociale sont flous, ils dérogent souvent aux catégories et aux normes instituées. Situés dans un entre-deux, entre le dedans et le dehors, jouant sur la mixité des espaces, ils sont un lieu 12. Dumazedier Joffre, Sociologie empirique du loisir. Critique et contre-critique de la civilisation du loisir, Paris, éditions du Seuil, 1974.

13. Outre l'immense littérature anglo-saxonne sur la thématique, on se contentera ici de renvoyer le lecteur à Larrère Catherine, Les Philosophies de l'environnement, Paris, PUF, 1997. d'investissement imaginaire et symbolique intense, souvent porteurs de contestation des conventions établies. En bref, ils apparaissent comme des objets labiles et indisciplinés. Les formes architecturales, les représentations, les valeurs, les rapports à l'environnement, au temps et à l'espace, les pratiques de sociabilité et les activités qui leur sont associées s'affirment alors avec un dénominateur commun : la transgression des clivages et des cloisonnements, l'effacement de certaines démarcations.

Un territoire de recherche

Le vaste territoire de recherche que dessinent les abris de loisirs peut se mesurer à celui des corpus à constituer. La peinture de paysage, et notamment les écoles orientalistes et impressionnistes, révèle les rencontres entre tentes, caravanes, cabanons et activités ludiques dans la nature. Le peintre américain Winslow Homer saisit dans les scènes champêtres, excursionnistes ou maritimes ces moments de jeu avec la nature où l'abri s'impose comme un appui nécessaire. Il en va de même des toiles de H. Vernet ou des croquis de voyage d'E. Fromentin. De même, les scènes de canotage et de déjeuners sur l'herbe rendues par Caillebotte, Monet, Manet et Renoir tissent l'orée d'une société de loisirs à la recherche d'objets techniques pour prendre pied dans la vie, en arrêtant le cours du temps.

La littérature offre à son tour une richesse certaine au chercheur. Le roman d'aventures, les récits d'expériences vécues, mais aussi les contes pour enfants font des abris un objet propre au périple initiatique, véritable interface entre l'accélération et la pause. Sans abri dans le monde merveilleux de Jules Verne ou dans les aventures décrites par Jack London ou Robert-Louis Stevenson, nul périple n'est possible. Celui-ci devient ainsi la condition d'accès au ludique. Louis Pergaud, dans La Guerre des boutons, fait de la cabane perchée dans les arbres la condition nécessaire au déroulement des jeux. Point d'observation, refuge ou cache au trésor, la cabane reste l'archétype même du monde de l'enfance et imbibe les mémoires d'adultes. Pour suivre l'analyse de M. Halbwachs 14 , l'abri de loisirs permet une prise nécessaire sur la vie. En faisant un court-circuit avec le quotidien, en proposant une mise en retrait, un face à face avec soi, l'abri permet de reprendre pied dans notre existence. Cette (re)prise de contact possède des variations infinies. Elle évolue en fonction des matériaux techniques mis à disposition, selon la forme cultu-relle de l'habitat, mais aussi et surtout en fonction des parcours de vie. Le chercheur peut alors se référer aux travaux nombreux sur l'anthropologie de l'habitat nomade ou à l'histoire de l'architecture. Mais la principale avancée réside dans les investigations relatives à l'histoire des loisirs. Le colonialisme a agi comme un miroir déformant dans l'importation de modes de vie dont nous n'avons pas encore fini de saisir l'importance. Les tentes ramenées et exposées comme trophées par les armées napoléoniennes, les huttes exposées dans les musées d'ethnographie ou encore les exhibitions humaines lors des expositions universelles ont eu des conséquences certaines sur le façonnage de nos loisirs. Il en va de même de la transposition des dispositifs militaires tels que le camp ou le bivouac à la sphère des activités de plein air.

La comparaison des données et le développement des problématiques tout au long de cet ouvrage, depuis les communautés et les abris apparemment les plus « traditionnels » jusqu'aux établissements pionniers et novateurs d'aujourd'hui, ont permis de tester et de faire avancer les hypothèses que nous avions formulées. Rappelons-les d'emblée succinctement, de manière à bien clarifier les enjeux de ce travail. Notre double hypothèse de travail a consisté 1) à envisager l'abri de loisirs comme le révélateur et le support du développement des loisirs dans nos sociétés contemporaines, et 2) à s'interroger sur les passages à un habitat multiforme à des fins ludiques. Sur ces hypothèses viennent se greffer certains mécanismes identifiés : la réversibilité et la labilité de l'objet qui permet de passer, en un instant, de la précarité sociale et de la pauvreté au jeu et aux loisirs ; le contentement du provisoire articulé à une forme de relâchement des codes sociaux et à un habitat précaire et temporaire ; un rapport privilégié à la nature et à l'uni-vers du plein air ; un désir d'évasion et de rupture avec le quotidien, un imaginaire de la vacance et du temps libre ; un espace alternatif, encadrant le continuum qui va des communautés recomposées (le village de toile, par exemple) au retrait social d'individus solitaires.

L'ancrage dans le folklore et le jeu L'abri de loisirs témoigne d'une rencontre entre folklore, traditions et pratiques ludiques. à la fin du xix e siècle, les jeunes bourgeois de la vieille Europe n'hésitent pas à interpeller les populations tziganes afin d'explorer leurs roulottes, pour en construire eux-mêmes à des fins touristiques. En Irlande, un premier club de caravaniers verra le jour, délaissant le chariot bâché pour la roulotte. Les occupants de Beauduc ou de Quiberon ont côtoyé les pêcheurs et leurs cabanons. Les enquêtes menées par le ministère de la Jeunesse et des Sports dans les années 1960 témoignent de cette rencontre entre le camping sauvage sur le littoral méditerranéen et la tradition folklorique de pêcheurs amenant dormir leur famille au cabanon sur la plage, en période estivale. Les Alpes et les Pyrénées ont connu, à travers l'essor de l'alpinisme et de la randonnée, la rencontre entre touristes spor-tifs et ruraux autour du chalet d'alpage ou du refuge de berger. De la même manière, les années 1970 sont encore marquées par la confrontation entre paysans et campeurs, alors que la France ne répond qu'à la moitié des de-mandes de vacances sous la tente avec son parc de terrains de camping classés. Le caractère éminemment réversible de l'abri de loisirs peut se lire largement dans ces entrelacs entre populations utilisant l'habitat précaire à des fins différentes. Autour d'un même type d'abri, le temps des uns n'est pas nécessairement celui des autres : on peut s'y détendre mais aussi y tra-vailler. Derrière la toile de tente ou la caravane ne se dissimule pas toujours un oisif ; l'actualité nous y fait découvrir avec voyeurisme des populations mises à la marge. Une organisation ludique telle que « Paris plage » voit d'un mauvais oeil inclure à son espace les tentes de la Croix-Rouge délivrées aux personnes sans abri. On touche là aussi au critère de réversibilité de notre objet. L'abri de loisirs, par sa constitution matérielle, peut passer, en un clin d'oeil, de la comédie humaine des vacances au tragique de l'exis-tence des vagabonds et des clochards.

Un potentiel symbolique

Au fil de son élaboration technique, l'abri de loisirs raconte des histoires singulières qui s'inscrivent dans de petites mythologies. Au Plessis-Robinson, un restaurant perché dans un arbre accueille ses convives en hommage au roman de D. Defoe. Il semble ainsi que l'habitat temporaire de loisirs incarne au niveau symbolique un potentiel recherché par ses utilisateurs. Posséder un voilier reste un désir fort pour une partie importante de la population, mais 90 % des embarcations restent à quai toute l'année. Il en va de même des caravanes laissées au garage pendant l'hiver ou cabanisées sur parcelles privées. Ainsi, l'abri de loisirs se caractérise avant tout par son potentiel d'évasion qui vient flatter l'inconscient du citadin. Les mythologies de l'abri de loisirs indiquent alors l'horizon vers lequel vagabonde le rêve : mythe de la route pour les caravaniers et camping-caristes, robinsonnade pour les plaisanciers, retrait pour les campagnards… Les références à Kerouac ou à Thoreau s'actualisent en permanence lors des enquêtes ethnologiques.

On comprend que l'abri de loisirs n'est pas inerte, mais qu'il constitue une sorte « d'objet actant », mis en mouvement par les personnes et les groupes qui l'utilisent. Sa plasticité et son originalité se prêtent à une grande variété d'utilisations et d'interprétations et offrent de nombreuses prises aux projections imaginaires. Il constitue, de ce point de vue, une sorte « d'espace potentiel », propre à des usages différenciés et pourtant contraints par le milieu, les formes et les symboles qui y sont associés. Tout un système d'investissements, de relations et de bricolage se construit pro-gressivement entre les usagers et leur habitat spécifique. L'abri de loisirs est à la fois mis en mouvement par les individus et par les groupes qui l'uti-lisent et, inversement, les conduites de chacun sont influencées par la lo-gique de l'espace et par l'architecture.

Le témoignage de retours à la nature Au-delà de ces projections symboliques, l'abri de loisirs s'inscrit plus lar-gement dans un récit mythique de retour à la nature et de fréquentation du sauvage. L'essor des actions philanthropiques en matière d'habitat reste traversé par la thématique de l'hygiénisme et par la pédagogie de l'aventure. E. R. Burroughs, le créateur de Tarzan, proposait aux Américains des an-nées 1930 des voyages clés en main en Afrique, dans la cabane de Tarzan juchée sur la cime des arbres. Dans les années 1960, Connaissance du monde propose, à son tour, des circuits touristiques exotiques côtoyant l'habitat des peuples nomades. Derrière les manifestations commerciales de l'abri de loisirs, se profile un mouvement fort de retour à la nature. Face à l'insalubrité des modes de vie urbains, il faut fuir vers la campagne et proposer aux jeunes un hébergement sain. Jardins, sociétés naturistes, asso-ciations de plein air, mouvements de jeunesse vont participer de cette lutte contre les maladies urbaines. L'hygiénisme semble toujours d'actualité, se manifestant dans les slogans publicitaires (manger équilibré, faire de l'exer-cice, sortir) mais s'incarnant également dans les normes sanitaires et sécu-ritaires des abris et installations en plein air. De l'école de plein air aux normes AFNOR, en passant par les différentes législations sur l'habitat mobile, les retours à la nature s'enrobent d'une morale avec laquelle tergi-versent les usagers d'abris de loisirs. L'abri de loisirs se constitue comme un espace de transition entre la nature et la culture. Les rapports à la nature, avons-nous relevé précédemment, sont quasiment communs à tous les types d'abris de loisirs. Mais celle-ci est l'objet d'une relation toujours ambiguë. L'abri témoigne autant du désir de la retrouver que de s'en protéger. Perdu au coeur des glaciers, il est l'ultime refuge des alpinistes, refuge à l'égard des risques naturels. Mais du tonneau de Diogène à la hutte de Wittgenstein en Norvège (où il pas-sera une année d'isolement), l'abri a aussi symbolisé le retrait du philosophe ou de l'écrivain à l'égard de l'agitation de la société. Que l'on pense au chalet d'Heidegger en forêt noire, à la petite maison d'écriture de Virgi-nia Woolf à la campagne, à la cabane au bout du monde de Kenneth White en pays cévenole, à celle de Le Corbusier au cap Martin, à l'abri de toile de Marcel Proust à Combray, ou encore à Henry David Thoreau et sa cabane isolée en pleine forêt, lieu où il écrit, à partir de sa propre expérience, un des grands classiques de la littérature américaine, Walden où la vie dans les bois.

Illustrant la polarisation de nos représentations entre la culture et la nature, les abris de loisirs ne témoignent pourtant d'aucun point stable qui permettrait de fixer le règne de la culture et celui de la nature. « Le flou juridique les concernant relève de la même adaptation à l'univers des règles qu'aux caprices de la Nature 15 . » La zone de Beauduc en Camargue ou celle de la grève de la Maison Blanche à Brest, en Bretagne, comme celle des « maisons dans l'eau » de Kien Svay, au Cambodge, soulignent que la précarité des abris de loisirs est, la plupart du temps, la meilleure réponse possible à l'instabilité du milieu naturel : mouvance du littoral et des bancs de sables, des marais et des crues des rivières. L'usage des lieux n'est ni une appropriation privée ni une appropriation publique, mais une tolérance. En ce sens, le territoire des abris de loisirs n'est pas régi par le régime de la propriété mais par celui de l'appropriation tolérée. De ce point de vue, le modèle de l'abri de loisirs peut être considéré comme une forme sociale d'appropriation des espaces de loisirs : appropriation du rivage, de la montagne, de la forêt, de la rivière ou du lac, de la campagne. L'incertitude est donc au fondement de ce type de construction. Rien ne la garantit, ni du côté des éléments naturels généralement hostiles, ni du côté de l'environnement social et institutionnel.

L'expérience de la vie simplifiée à côté de cette idéologie d'encadrement des touristes, l'abri de loisirs propose également une simplification des conditions d'existence. La corporéité y est davantage affichée, le dénuement pratiqué. Les parois de l'abri sont un prolongement du corps laissant passer plus largement les sons, les odeurs, les variations de température et de lumière. En certaines circonstances, l'abri doit se concilier avec une gymnastique du corps, en raison de 15. Picon Bernard, « Les cabanes de l'entre-deux mondes », in Cabanes, cabanons et campements. Formes sociales et rapports à la nature en habitat temporaire, Brun Bernard, Dufour Annie-Hélène, Picon Bernard et Ribéreau-Gayon Marie-Dominique (dir.), Châteauneuf de Grasse, éditions de Bergier, 2001, p. 334. son exiguïté et de son confort tout relatif. Enfin, par son caractère modulable et transformable, il incarne au plus près les activités permanentes de bricolage, de jardinage ou de cuisine qui composent le socle des loisirs actifs selon G. Friedman [START_REF]C'est-à-dire des loisirs propices au processus d'individuation, pouvant aussi être compris comme un second travail[END_REF] . Conservatoire à sa manière des arts de faire, il est aussi un espace où s'élabore la domus familiale et où se génèrent les empreintes de l'enfance. Il permet ainsi de descendre dans la part la plus corporelle et la plus intime de soi. Face à une telle mise à nu, il amplifie les rapports humains, les électrise par sa quasi absence de médiation. Les humoristes traduisent bien cette comédie humaine, caricaturant les disputes et les ébats conjugaux pendant le temps des vacances sous la tente, dans la caravane ou sur la terrasse du chalet.

Des dispositifs d ' encadrement des loisirs

Enfin, les abris de loisirs transcrivent des intentions explicites d'encadrement des modalités du temps libre. à l'instar des activités sportives, les abris de loisirs ont été pensés, à la fin du xix e siècle, comme un dispositif de formation de la jeunesse. La pédagogie du camp développée par les scou-tismes ne se trouve guère éloignée de celle des internats à la campagne, du mouvement des auberges de jeunesse, des clubs alpins, des Touring clubs, des associations de camping et de plein air. Les exemples ne manquent guère [START_REF]Voir notamment les numéros de la revue Recherches consacrés à l'hygiénisme et au travail[END_REF] . Le créateur du Centre franco-américain, Royal Ramson Miller, par-lait déjà, en 1924, de « dispositif » pour désigner les évasions offertes par l'auto-camping. L'idée fut transférée aux loisirs de masse, incarnés par l'es-sor des Clubs Méditerranée ou des terrains de camping organisés. Le camp, le bivouac, la cogestion, le village vacances… autant de termes auxquels le chercheur doit rester attentif pour construire son objet. Comme le signalait en son temps Michel Foucault 18 , ces mots sont ambivalents : ils incarnent à la fois les grandes utopies sur lesquelles se sont construits les loisirs, et en même temps traduisent des aphasies, des manières de court-circuiter les rythmes imposés par le travail et les normes édifiées par les institutions.

Au final, il nous semble que l'économie générale de l'abri produit un ailleurs familier, requalifiant les relations entre ville et nature, entre travail

  9. Willemin Véronique, Maisons mobiles, Paris, Alternatives, 2004. 10. Cette production représente 6,5% du chiffre d'affaires de l'entreprise. 11. Bonnain Philippe et Villanova Roselyne (dir.), D'une maison l'autre. Parcours et mobilité résidentielle, Paris, Créaphis, 1999.

  3. Voir notamment sur ce thème Corbin Alain, Le Miasme et la jonquille. L'odorat et l'imaginaire social xviii e -xix e siècles, Paris, Aubier, 1982 ; Barles Sabine, La Ville délétère. Médecins et ingénieurs dans l'espace urbain xviii e -xix e siècle, Seyssel, Champ Vallon, 1999 ; ou encore Murard Lion et Zylberman Patrick (dir.), L'Haleine des faubourgs. Ville, habitat et santé au xix e siècle, Paris, Recherches, n° 29, dé-Nature and Society. Anthropological Perspectives, Londres, Routdledge, 1996 ; Descola Philippe, Par-delà nature et culture, Paris, Gallimard, 2005. voyage est reconfiguré par l'excursion. Mark Twain, de retour en Angleterre, décrit longuement les roulottes dans les faubourgs de Londres, comme les cabanes où trouvent refuge les jeux d'enfants. Elisabeth von Arnim décrit les voyages en roulotte entrepris par la bourgeoisie à la fin du xix e siècle. Les voyageurs anglais, en Orient, profitent des tentes et des bara-quements expérimentés par la Compagnie anglaise des Indes orientales pour s'héberger la nuit lors des circuits balisés par les premiers voyagistes tels que T. Cook. Le xix e siècle montre une grande porosité entre les abris liés aux activités de terroir, le renouveau du voyage 7 et les objets confection-nés par les militaires et les explorateurs. Lorsque A. Daudet publie Tartarin de Tarascon, il confronte les cercles bourgeois de la chasse en Provence, l'appel exotique de l'Orient et le dernier chic technologique incarné par la nouvelle tente abri.

	cembre 1977.
	4. Cholvy Gérard, Histoire des organisations et mouvements chrétiens de jeunesse
	en France (xix e -xx e siècles), Paris, Cerf, 1999 ; Gauthé Jean-Jacques, Le Scoutisme
	en France, inventaire de la bibliographie et des sources, Montpellier, PUM, 1997.
	5. Corbin Alain, L'Avènement des loisirs, Paris, Aubier, 1995 ; Boyer Marc, His-
	toire de l'invention du tourisme, La Tour d'Aigues, L'Aube, 2003.
	6. Dalla Bernadina Sergio, L'utopie de la nature, Paris, Imago, 1996 ; Descola
	Philippe et Gisli Palsson (éd.),

Halbwachs Maurice, Les Cadres sociaux de la mémoire, Paris, Albin Michel, 1994.


Elyes Lamine
email: elyes.lamine@univ-jfc.fr

Marie -Noëlle
email: marie-noelle.cufi@chic-cm.fr

Katarzyna Borgiel
email: katarzyna.borgiel@univ-jfc.fr

Christophe Bortolaso
email: christophe.bortolaso@berger-levrault.fr

Hervé Pingaud
email: herve.pingaud@univ-jfc.fr

Mustapha Derras
email: mustapha.derras@berger-levrault.fr

BL.Frailty: Towards an ICT-Based Platform for Frailty Assessment at Home

Keywords: ageing, frailty management, ICT-based platform, knowledge management, smartphone application, IoT device. I

Frailty is a clinical syndrome relative to ageing, and characterizes an intermediate state between robust health and the loss of autonomy. The preservation of one's capacities or abilities falls within a dependency prevention approach, based on a thorough understanding of one's medical and social situation, and his/her environment of life. This understanding is usually gained through an extensive collection of data, using standardized assessment surveys. The obtained data is next analyzed in order to provide personalized recommendations relative to the ways of living. In this paper, we describe the concept, architecture and use of an ICT platform which aims to support professionals and patients in the assessment of frailty at home. Our prototype consists of a knowledge-based system relative to assessment surveys which is connected to a smartphone application and IoT devices.

INTRODUCTION

In the context of the demographic transition towards older population, experiencing the last years of life in good health is a perspective that brings many positive implications for the elderly and for the society [START_REF]World report on ageing and health[END_REF]. However, healthy and active aging does not only mean to be free from chronic diseases, but also to be away from declines in physical, cognitive or psychosocial capacities, which define the functional ability in the older age that enables well-being.

Disability and loss of independence can be triggered by illness and/or accidents, or be a consequence of decrease in physiological reserves [START_REF] Robine | Introducing frailty and the frailty process within the disablement models[END_REF]. In clinical terms, the age-related decline in physiological systems is defined as the syndrome of frailty [START_REF] Clegg | Frailty in elderly people[END_REF]. Unlike disability, frailty is reversible or can be minimized by personalized interventions [START_REF] Subra | The integration of frailty into clinical practice: preliminary results from the Gérontopôle[END_REF], aiming to preserve one's capacities. Thus, frailty assessment and personalized interventions form the basis of dependency prevention. The preventive approach aims to reduce burdens posed by disabilities not only on the elderly, but also on the healthcare system, including high healthcare costs.

In the French health system, frailty management can be seen as a decision making process. It can be described through a three stages model including: (1) frailty screening, (2) frailty evaluation and the definition of a personalized intervention plan, and (3) frailty follow-up. Hence, the aim of this management process is to prevent and/or to delay disability and dependence, and thus to improve the quality of life of older people. It aims also at reducing both the number and the length of hospitalization and institutionalization [START_REF] Iglesia-Gomez | Action group on prevention of frailty of the European Innovation Partnership (EIP) on active and healthy ageing[END_REF].

Despite the valuable potential benefits stemming from the frailty management process, its effective implementation in primary care is quite recent and still faces many challenges, particularly in terms of sustainable strategy and effective tools. This issue represents the motivations of our work.

In this paper, we describe an ongoing research project which aims the development of new assessment support for frailty management. We first provide, in section II, a brief presentation of the medical and organizational background, and we introduce main challenges related to frailty assessment. Then (section III) we describe our prototype of a ICT platform for frailty assessment. The paper ends with a discussion (section IV) and a conclusion (section V).

II. BACKGROUND

To understand our research motivations and the challenges to address in order to design an ICT system for frailty assessment, we must previously capture basic medical knowledge about what are the artefacts relevant to the loss of autonomy in older age, and how they can be attained in a running process of care.

A. Frailty

Frailty refers traditionally to the health status of an elderly person. It is defined as a multidimensional clinical syndrome, characterized by loss of reserves (i.e. energy, physical ability, cognition, health) and diminished resistance to stressors, causing vulnerability to adverse health outcomes [START_REF] Fried | Frailty in Older Adults: Evidence for a Phenotype[END_REF][START_REF] Rockwood | A global clinical measure of fitness and frailty in elderly people[END_REF][START_REF] Hogan | Models, Definitions, and Criteria for Failty[END_REF]. Adverse health outcomes usually associated with frailty include: morbidity, disability, inappropriate healthcare use, institutionalization, poor quality of life, and even death [START_REF] Marzetti | Innovative Medicines Initiative: The SPRINTT Project[END_REF].

There exist two main conceptualizations used to depict and to assess frailty [START_REF] Cesari | The frailty phenotype and the frailty index: different instruments for different purposes[END_REF]: the phenotype model [START_REF] Fried | Frailty in Older Adults: Evidence for a Phenotype[END_REF] and the cumulative deficit model [START_REF] Rockwood | A global clinical measure of fitness and frailty in elderly people[END_REF].

The frailty phenotype is defined across five criteriasymptoms: (1) unintentional weight loss, (2) poor handgrip strength, (3) self-reported exhaustion, (4) slow gait speed, and (5) low physical activity level. The result allows to classify an individual as one of three categories: "robust", "pre-frail" or "frail", by an ordinal value. Fried's model is related directly with the physical ability dimension.

The second model, the cumulative deficit model, quantifies a Frailty Index that is obtained by the count of clinical deficits (i.e. diseases, abilities, physical and neurological signs). The original list of deficits contains 70 items. The evaluation result is the ratio of health deficits present for a given individual to the total of deficits considered for this individual. Thus, frailty evaluated by Frailty Index is a continuous variable. This model covers several dimensions of frailty, including physical, cognitive, and psycho-social.

The use of these models, and associated tools, can be seen as complementary [START_REF] Cesari | The frailty phenotype and the frailty index: different instruments for different purposes[END_REF]: frailty phenotype was developed in order to identify frail people, while Frailty Index was created with the idea to characterize their situation in detail. Identification and characterization form the two first steps within the dependency prevention approach.

B. Frailty management process

Discriminated by the phenotype of frailty, the older population can be categorized into three sub-groups: "robust", "frail" and "disabled" elderly people [START_REF] Subra | The integration of frailty into clinical practice: preliminary results from the Gérontopôle[END_REF]. Dependency prevention can be applied within each of them. In France, the master process of frailty management can be described through a three stages model (Fig. 1) including: (1) screening (or detection), (2) evaluation and personalized intervention plan (PIP) definition, and (3) follow-up [START_REF] Subra | The integration of frailty into clinical practice: preliminary results from the Gérontopôle[END_REF][START_REF] Vellas | Looking for frailty in community-dwelling older persons: The Gérontopôle Frailty Screening Tool (GFST)[END_REF][START_REF] De Kerimel | How to Manage Frail Older Adults in the Community? Proposal of a Health Promotion Program Experienced in a City of 16,638 Inhabitants in France[END_REF].

Stage 1: Screening consists of the assessment of target individuals (i.e. 65 years old or more, without physical disability and without acute clinical disease) in order to identify pre-frail and frail elderly among the general elderly population. Frailty screening relies mostly on easy and quick assessment tools, often in the form of questionnaires, like Gérontopôle Frailty Screening Tool (GFST) [START_REF] Vellas | Looking for frailty in community-dwelling older persons: The Gérontopôle Frailty Screening Tool (GFST)[END_REF] or Frail Non-Disabled (FIND) [START_REF] Cesari | A Self-Reported Screening Tool for Detecting Community-Dwelling Older Persons with Frailty Syndrome in the Absence of Mobility Disability: The FiND Questionnaire[END_REF]. In case of GFST, screening is done by a GP, in case of FIND -by the elderly person himself/herself.

Stage 2:

Once the person is identified as pre-frail or frail, he/she can benefit from a multidisciplinary clinical assessment of different dimensions of his/her health, situation, lifestyle, and life environment. The evaluation, usually in form of a comprehensive geriatric assessment (CGA) enables the refinement of the initial diagnosis and the definition of a set of personalized prevention activities, according to the need of support. Elderly person's preferences, and the availability of resources for the realization of preventive activities, are equally considered during the formulation of recommendations. Table I resumes surveys frequently used [START_REF] Vellas | Implementing frailty screening, assessment, and sustained intervention: The experience of the Gérontopôle[END_REF], frailty dimensions covered by each survey, and the number of items (data) collected. Additional evaluations may also be proposed if necessary. The preventive interventions are behavioral and therapeutic suggestions to correct specific disability risk factors (e.g. dietary intake recommendations, physical exercises, etc.).

Stage 3:

The third and last stage of frailty management process aims to follow-up the person's frailty evolution, his/her compliance to the PIP, and the evaluation of the efficiency of the proposed recommendations. At different times after the first evaluation (Stage 2), the elderly person is contacted (i.e. phone call or medical consultation) to evaluate his/her degree of engagement in new lifestyle habits and his/her situation. In the case of deterioration or maladjustment, the PIP is updated (loop from stage 3 to 2). In France, the general practitioner plays an important role in all three stages of such a frailty management process, being the main process owner on the medical side.

C. Frailty management challenges

Although the theoretical concept of frailty is agreed upon, its practical screening and evaluation still present some limitations due to the existence of a multitude of frailty assessment surveys [START_REF] Hogan | Models, Definitions, and Criteria for Failty[END_REF][START_REF] De Vries | Outcome instruments to measure frailty: A systematic review[END_REF][START_REF] Sternberg | The Identification of Frailty: A Systematic Literature Review[END_REF][START_REF] Buta | Frailty assessment instruments: Systematic characterization of the uses and contexts of highly-cited instruments[END_REF][START_REF] Xie | Components and indicators of frailty measures: a literature review[END_REF]. One could point the choice of the right set of surveys as the main challenge within the frailty management tools. The choice of the data to use to assess the person's situation is clearly of utmost importance, but the differences in their use between professionals coming from different institutions or countries is more a cultural issue.

Given the number of evaluation surveys (e.g.19 in the example in Table I), the evaluation and the definition of personalized intervention plan are quite time consuming. Moreover, evaluation is often done in a hospital, by a group of healthcare professionals (i.e. geriatrician, nurse, neuropsychologist, physical therapist, dietician), who must be seen as limited resources. Thus, the number of elderly people who actually undergo screening and evaluation remains low compared to their actual number in a given territory.

In the light of these limitations, there is an urgent need to implement home-based frailty management, relying on home care services, and using digital solutions for data collection. It is noteworthy that each stage of frailty management process faces specific challenge relative to data collection. During screening (Stage 1), the challenge is to get in touch with and collect the data form the whole population of target individuals (i.e. people of 65 years or more). During evaluation and PIP definition (Stage 2), the challenge is to collect important amounts of data in the most efficient way, both for the evaluated person, and for the evaluators (professionals). During follow-up (Stage 3), the challenge is to collect personalized sets of data, over long periods of time (months to years) and with high frequency (several times during a year), in order to detect changes as they occur.

To deal with these challenges, many research projects aim the design and/or the evaluation of technological artefacts for automated collection of frailty-related indicators, with the idea to augment and/or to replace traditional paper support [START_REF] Kelaiditi | Frailty and Novel Technologies -A Step Ahead[END_REF][START_REF] Mugueta-Aguinaga | Is Technology Present in Frailty? Technology a Back-up Tool for Dealing with Frailty in the Elderly: A Systematic Review[END_REF]. Among them, we can name individual wearable artefacts for automated assessment of activity patterns by objective uniaxial accelerometer [START_REF] Chan | Measuring activity performance of continuing care residents using the activpal: an exploratory study[END_REF], or of the muscular strength during stair climbing by using 3D-accelerometers and 3D-gyroscopes [START_REF] Hellmers | Stair Climb Power Measurements via Inertial Measurement Units. Towards an Unsupervised Assessment of Strength in Domestic Environments[END_REF]. As the extension of person-embedded sensors systems, are projects aiming environment-embedded systems composed of multiple sensors. For example, Indoor Proximity Systems are experimented in order to monitor indoor patient activity [START_REF] Power | Developing a Sensor based Homecare System. The Role of Bluetooth Low-Energy in Activity Monitoring[END_REF]. In both cases, the use of sensors enables more frequent data collection and objective measurements [START_REF] Hellmers | Stair Climb Power Measurements via Inertial Measurement Units. Towards an Unsupervised Assessment of Strength in Domestic Environments[END_REF]. There are other research projects that aim the design and/or the evaluation of technologies supporting the user entry of frailty-related indicators, including self-assessment by the elderly (FrailSafe by porto4ageing). Finally, there exist also projects that support mixed data collection methods, including both manual and automatic. For example, data can be collected from sensors and from accelerometer sensors in a mobile phone and from the patient record [START_REF] Fontecha | A Mobile and Ubiquitous Approach for Supporting Frailty Assessment in Elderly People[END_REF].

Given the need to support home-based frailty management, our goal is to provide an ICT platform, named BL.Frailty, dedicated for frailty assessment (screening, evaluation and follow-up) at home. In comparison with related work, our motivation is to provide an adaptable data collection platform through a mix of automatic, semi-automatic and manual data entry solutions. The automatic data entry is to be based not on the creation of new devices, but on the integration of already existing solutions. The semi-automatic data collection will be based on the study of assessment surveys. If the ultimate goal is to assist frailty assessment process by automating some assessment activities, the automation is not always feasible nor desirable, and the manual-automatic data collection will also be made possible. Thus, for each data traditionally used to assess frailty, we aim to provide, where possible, several alternative data collection methods. This way, we want to provide the users (the elderly and professionals) with the possibility of creating, for each assessment case, a personalized data collection system, depending on their needs, preferences, constraints, etc.

III. BL.FRAILTY PLATFORM OVERVIEW

In order to study the opportunities for automation of assessment activities within the frailty management process, we have first analyzed the content of different assessment surveys used by a local hospital center, offering frailty evaluation service within one-day hospitalization. The analysis of data covered by each survey rapidly showed that there exist similarities between them, more precisely in the topics and the variables that they cover. In order to identify the similarities in a rigorous manner, we carried out a semantic mapping of the content of 29 surveys (Table II). Once we have defined the variable assessed by each question and by each possible answer for a question, we specified two types of semantic links (Fig. 2). The first type, called "similar to", expresses a semantic equivalence relationship between two concepts. This is a two-way relationship. The second type, called "relating to", expresses a closely related relationship between two concepts, and is a unidirectional relationship.

We have used these two semantic link types to map question items addressing the same variable, with the same meaning, among different assessment surveys.

For example, the MNA survey and the ADL survey both include the assessment of the ability of an elderly person to feed himself/herself and his/her ability to move around. In the first case, the MNA question item is "Mode of feeding", and it has three possible answers. The ADL question item is "Feeding", with three possible answers in the French version. The result of mapping of possible answers for these two questions for these two surveys are four one-way semantic links (Fig. 3, at the top).

MNA and ADL both serve as well to evaluate the ability of the elderly person to move. The ADL question is "Transferring", and the MNA question is "Mobility". However, the meaning of the evaluation items is not exactly the same in these two surveys, thus there is only one mapping possible (Fig. 3, at the bottom). In this case, the identified semantic link is two-way.

A. BL.Frailty platform concept

The identification of links between assessment surveys was at the origin of the concept of the future platform to design. Indeed, by providing such a knowledge base of the surveys and their semantic connections, the system could assist the user in the evaluation process by suggesting to complete at the same time all of the questions addressing the same variable in the same manner. Thus, the first functional requirement for the platform was to support frailty assessment by reusing data collected and entered by the evaluator (user).

As the possible propagation should always remain under the control of the user, the platform was also to be designed to support frailty assessment by allowing the manual entry and the storage of all assessment data. The support role of the technological media is here more traditional, and relies in the capacity to aid the calculation of evaluation scores, to access historical data, and to represent it textually and graphically.

Finally, with the idea of data collection without the presence of any professional, the system was to support frailty assessment by automatic data collection from sensors. Here, our goal was not to develop new ways of collecting data, but to reuse already existing technologies.

Thus, the future platform should give both manual, semiautomatic and automatic support for frailty data entry. In order to experiment the validity of the concept, we have worked on a first prototype of the ICT platform.

B. Surveys and functionalities

The prototype implements at this stage two screening and nine evaluation surveys (stage 1 and stage 2). Screening surveys are (1) GFST and (2) FIND. Evaluation surveys cover: (1) ADL, (2) IADL, (3) SPPB, (4) Tinetti, (5) MNA, (6) MMSE, (7) GDS, (8) Doloplus and (9) Algoplus. Moreover, the prototype covers weight and BMI. measures

The prototype of the ICT platform encompasses eight main functionalities (digital services): (1) survey and measures management, (2) knowledge base management, (3) user management, (4) patient management, (5) administrative patient data entry, storage and display, (6) medical patient data entry, storage and display, (7) calculation of assessment survey scores, and (8) creation and displays of graphs of assessment survey results and measures.

C. Smartphone application

The smartphone application is the principal part of the platform. It has three main components: (1) connection page, (2) patient list, and (3) patient assessment record. Patient assessment record includes: (3.1) patient administrative data, (3.2) assessment surveys, (3.3) assessment measures, and (3.4) assessment charts (Fig. 4). The connection page guarantees patient data security and is enabled by a username and a password. Once the user is connected, the application displays the list of patients associated with the user. By choosing a given patient name, the user enters the patient assessment record. The main page of the assessment record is composed of patient administrative data and of five navigation icons. The icons enable to access assessment surveys, assessment questions, measures, assessment history, and to include data collected by sensors (Fig. 4-1).

The list of assessment surveys shows not only the names of different surveys, but also -if one or many of surveys have already been used for the patient -the score obtained during the last evaluation, the day of the last evaluation and the name of the evaluator (the user; Fig. 4-2). After opening a given survey, the user visualizes different survey questions and question items (possible answers). Also, if the survey has already been used in the past, for each question the user visualizes question items used during the last evaluation (Fig. 4-3). Thus, a new evaluation is always carried out in reference to the previous one, and the evaluation data is entered as modifications of question items.

Similarly, the list of measures shows measure names and, if applicable, the last obtained value, the day and the person who collected and entered the data.

Assessment history enables to consult all past evaluations (score, date, hour and username) in chronological order and under two representations: textual and graphical (Fig. 4-4).

In line with the concept, the smartphone application includes two forms of data collection: manual and semiautomatic propagation of evaluation results. Indeed, the presence of semantic links enables to assist the user during the assessment process. For example, while completing the MNA, if the user choses "Self-fed without any problem", the interface offers him the possibility two answer in the same time the ADL question by entering "Serves food and eats without assistance" (Fig. 45).

D. Sensor

The sensor that we have decided to experiment in the first step, in order to enable the automatic collection of data, is a weight & BMI (Body Mass Index) Wi-Fi scale, the scale "Body" by Nokia Withings. It enables to collect automatically the weight of the person, and his/her BMI. Fig. 3. Semantic links "relating to" (RL) and "similar to" (SL) resulting from mapping between MNA and ADL surveys.

E. Architecture

The architecture of BL.Frailty consists of: (1) a server, (2) an administration web interface, (3) a smartphone application, and (4) a sensor (Fig. 5).

The server was developed in Java and communicates both with the interface, the mobile application, and the sensor system, through web services. The database on the server is divided in two parts. The first part, a SQL Database 1 (MySQL), contains static data relative to surveys (i.e. survey names, survey questions, possible answers, knowledge base of semantic links), to measures (measure list), to users (user list and rights) and to patients (patient list and their administrative data). The second part, a NoSQL database 2 (MongoDB), contains dynamic data relative to results of patient evaluations (answers given during an evaluation, values of measures).

The administration web interface was developed with standard web technologies (HTML, CSS and JavaScript). The interface enables to manage (addition, modification, suppression) the list of surveys and measures, the knowledge database, the list of users and the list of patients.

The mobile application was developed in Android. It operates thanks to a user interface and a local SQLite database, which communicates with the server databases. The access to the user interface requires a user account. Despite the presence of a local database, the use of the mobile application requires constant access to the server in order to guarantee the security of patient data, through constant control of user rights.

The "Body" scale holds its proper database, and offers a smartphone application enabling to monitor collected data. The interface between the server and the scale is done through the communication with the scale's API. At this stage of the project, the user has to manually request the update of data, which are next registered in the BL.Frailty database.

IV. DISCUSSION

In order to address the definition of the concept and the design of a new technological solution for frailty assessment, we have adopted the Living Lab design methodology based on a partnership between local actors: (1) a software company, (2) an engineering school and its living lab, specialized in academic and applied research in e-health, and (3) with a local hospital center specialized in frailty management. This approach allowed us to integrate future users, healthcare professionals in our case, in the development process from the first stage of the project. Its output is the prototype of the BL.Fraility platform. This first version includes manual data entry; automatic data collection by electronic body weight scale "Body" from Nokia Withings; and semi-automatic propagation of evaluation results, based on the knowledge base of semantic links within the nine evaluation surveys.

Overall, there is only one survey, IADL, for which no semantic link with other survey has been identified. For the eight surveys, we identified 32 semantic links. Among these, eight links are "similar to" (two-way) links (Table III). The remaining 24 links are "relating to" (one-way) links (Table IV). Overall, the number of links identified between surveys was the highest for surveys aiming the assessment of the same domain (i.e. pain assessment with Doloplus and Algoplus). In the case of complementary surveys, the links were also present but less numerous. These first results show that the knowledge database of semantic links can provide support for the frailty management process, however this kind of data entry assistance will apply only to a subset of assessment variables. The effective support needs to be further studied, both based on the integration of other surveys (i.e. Table I) and on its application within real-life frailty management practice.

Our proposal to support frailty assessment at home, developed in this paper, is to provide an adaptable data collection platform, that would enable to create personalized frailty assessment systems based on the integration of a mobile application, of a knowledge database and of sensors. We identify several research directions for future work. First, within the idea of alternative data collection methods, we plan to study the value of these different methods, which can possibility be different depending on the assessment variable in question. Next, as the platform relies on the integration of sensors already existing on the market, and as usually there exist several different sensors for collecting a given data (i.e. weight), we must consider the value of usage of these alternative sensors in order to promote the acceptability of the platform and its components by the end users. Also, as the flexibility of the platform could also come from the personalization of manual data entry, we plan also to study the value of data entry by non-healthcare professionals, including elderly people themselves. Finally, we plan to evaluate the usability of the mobile application, with professionals and elderly people, both in laboratory and natural settings.

V. CONCLUSION

In order to address data collection challenges within the dependency prevention approach, we have developed a concept and a prototype of an ICT platform for frailty assessment. The concept of the system is based on a mix of manual, semi-automatic (knowledge base) and automatic (sensors) data collection techniques. The prototype of the system implements successfully these three techniques and thus forms a valid proof of concept.

Fig. 1 .

 1 Fig. 1. The process of elderly evolution and the process of frailty management.

Fig. 2 .

 2 Fig. 2. Two types of links between assessment questions.

Fig. 4 .

 4 Fig. 4. Architecture of the system.

Fig. 5 .

 5 Fig. 5. Smartphone application (from the left): (4-1) patient assessment record, (4-2) list of tests, (4-3) MNA test entry (on the left); (4-4) automatic proposition of answer for a question of ADL test, while doing MNA test, (4-5) MNA test score graph.

TABLE I .

 I FRAILTY EVALUATION SURVEYS.

	Survey name	Survey abbrev.	Frailty dimens.	Nb items (score)
	1. Frailty criteria (Fried)	-	Physical 5 (5)
	2. Mini Mental State Examination	MMSE Cognition 30 (30)
	3. Clinical Dementia Rating	CDR	Cognition 6 (3)
	4. Memory Impairment Screen	MIS	Cognition 4 (8)
	5. Memory Impairment Screen -Delayed MIS-D Cognition 4 (8)
	6. Activities of Daily Living	ADL	Physical 6 (6)
	7. Instrumental Activities of Daily Living IADL	Physical 8 (8)
	8. Short Physical Performance Battery	SPPB	Physical 3 (12)
	9. Gait speed	-	Physical 1 (n/a)
	10. Wrist strength	-	Physical 1 (n/a)
	11. Mini Nutritional Assessment	MNA	Nutrition 18 (30)
	12. Vitamin D concentration	-	Nutrition 1(n/a)
	13. Geriatric Depression Scale	GDS	Psycho-social	15 (15)
	14. Distance vision	-	Sensory	1 (n/a)
	15. Near vision	-	Sensory	1 (n/a)
	16. Amsler grid	-	Sensory	1 (n/a)
	17. Hearing Handicap Inventory for the Elderly -Screening	HHIE-S Sensory	10 (40)
	18. Urinary incontinence	-	Other	6 (6)
	19. Oral Health Assessment Tool	OHAT Other	8 (16)
	SUM number of items (score)			123

TABLE III .

 III "SIMILAR TO" LINKS BETWEEN SURVEYS.

	Between survey	Number of links	and survey
	ADL	1	MNA
	Doloplus	2	ADL
	Doloplus	1	GDS
	Doloplus	4	Algoplus
	TABLE IV.	"REALTING TO" (LINKS BETWEEN SURVEYS.
	From survey	Number of links	Towards survey
	ADL	2	MNA
	MNA	2	ADL
	Tinetti	2	SPPB
	Doloplus	4	ADL
	Doloplus	2	GDS
	Doloplus	12	Algoplus

ACKNOWLEDGMENTS

The authors would like to thank A. Lefort (CHIC-CM) for her precious insights on the frailty management process running and challenges. A. Lapeyre (ISIS) has realized the research and development work of the first prototype, which was subsequently continued by T. Frassati and S. Tournou (ISIS). C. Picard and V. Morel (Berger-Levrault) have both contributed to the creation and to the execution of this project.