Philippe Wenger
email: philippe.wenger@lan.ec-nantes.fr

Damien Chablat

Uniqueness Domains in the Workspace of Parallel Manipulators

Keywords: Parallel Manipulator, Workspace, Singularity, Aspect, Uniqueness domains, Octree

This work investigates new kinematic features of parallel manipulators. It is well known that parallel manipulators admit generally several direct kinematic solutions for a given set of input joint values. The aim of this paper is to characterize the uniqueness domains in the workspace of parallel manipulators, as well as their image in the joint space. The study focuses on the most usual case of parallel manipulators with only one inverse kinematic solution. The notion of aspect introduced for serial manipulators in [Borrel 86] is redefined for such parallel manipulators. Then, it is shown that it is possible to link several solutions to the forward kinematic problem without meeting a singularity, thus meaning that the aspects are not uniqueness domains. An additional set of surfaces, namely the characteristic surfaces, are characterized which divide the workspace into basic regions and yield new uniqueness domains. This study is illustrated all along the paper with a 3-RPR planar parallel manipulator. An octree model of spaces is used to compute the joint space, the workspace and all other newly defined sets.

INTRODUCTION

A well known feature of parallel manipulators is the existence of multiple solutions to the direct kinematic problem. That is, the mobile platform can admit several positions and orientations (or configurations) in the workspace for one given set of input joint values [ Merlet 90]. The dual problem arises in serial manipulators, where several input joint values correspond to one given configuration of the endeffector. To cope with the existence of multiple inverse kinematic solutions in serial manipulators, the notion of aspects was introduced [ Borrel 86]. The aspects were defined as the maximal singularity-free domains in the joint space. For usual industrial serial manipulators, the aspects were found to be the maximal sets in the joint space where there is only one inverse kinematic solution. Many other serial manipulators, referred to as cuspidal manipulators, were shown to be able to change solution without passing through a singularity, thus meaning that there is more than one inverse kinematic solution in one aspect. New uniqueness domains have been characterized for cuspidal manipulators [ Wenger 92], [El Omri 96]. It is also of interest to be able to characterize the uniqueness domains for parallel manipulators, in order to separate and to identify, in the workspace, the different solutions to the direct kinematic problem. To the authors knowledge, the only work concerned with this issue is that of [Chételat 96], which proposes a generalization of the implicit function theorem. Unfortunately, the hypothesis of convexity required by this new theorem is still too restrictive. This paper is organized as follows. Section 2 describes the planar 3-RPR parallel manipulator which will be used all along this paper to illustrate the new theoretical results. Section 3 restates the notion of aspect for parallel manipulators. New surfaces, the characteristic surfaces, are defined in section 4, which, together with the singular surfaces, further divide the aspects into smaller regions, called basic regions. Finally, the uniqueness domains are defined in section 5. The workspace, the aspects, the characteristic and singular surfaces, and the uniqueness domains are calculated for the planar 3-RPR parallel manipulator using octrees. The images in the joint space of the uniqueness domains are also calculated. It is shown that the joint space is composed of several subspaces with different numbers of direct kinematic solutions.

PRELIMINARIES

PARALLEL MANIPULATOR STUDIED

This work deals with those parallel manipulators which have only one inverse kinematic solution. In addition, the passive joints will be always assumed unlimited in this study. For more legibility, a planar manipulator will be used as illustrative example all along this paper. This is a planar 3-DOF manipulator, with 3 parallel RPR chains (Figure 1). The input joint variables are the three prismatic actuated joints. The output variables are the positions and orientation of the platform in the plane. This manipulator has been frequently studied, in particular by The passive revolute joints are assumed unlimited.

OCTREE MODEL

The octree is a hierarchical data structure based on a recursive subdivision of space [Meagher 81]. It is particularly useful for representing complex 3-D shapes, and is suitable for Boolean operations like union, difference and intersection. Since the octree structure has an implicit adjacency graph, arcwiseconnectivity analyses can be naturally achieved. The octree model of a space S leads to a representation of S with cubes of various sizes. Basically, the smallest cubes lie near the boundary of the shape and their size determines the accuracy of the octree representation. Octrees have been used in several robotic applications [Faverjon 84], [Garcia 89], [El Omri 93]. In this work, the octree models are calculated using discretization and enrichment techniques as described in [Chablat 96].

The octree models of the reachable joint space (in the space ρ 1 , ρ 2 , ρ 3 ) and of the workspace (in the space x, y et φ) of the 3-RPR parallel manipulator are shown in figures 2 and 3 (the workspace and the reachable joint space are defined in section 3.1). The reachable joint space is not a complete parallelepiped, since not any joint vector can lead to an assembly configuration of the manipulator.

SINGULARITIES

The vector of input variables and the vector of output variables for a n-DOF parallel manipulator are related through a system of non linear algebraic equations which can be written as :

( )

F q X , = 0 (4)
where 0 means here the n-dimensional zero vector.

Differentiating (4) with respect to time leads to the velocity model :

A X B q & & + =0 (5)
where A et B are n × n Jacobian matrices. These matrices are functions of q and X :

A F X B F q = = ∂ ∂ ∂ ∂ (6)
These matrices are useful for the determination of the singular configurations [Sefrioui 92].

Type-1 singularities

These singularities occur when det(B) = 0.

For the planar manipulator, this condition can be satisfied only when ρ 1 = 0 or ρ 2 = 0 or ρ 3 = 0.

In practise, the type-1 singularities are attained when one of the actuated prismatic joints reaches its limit [Gosselin 90]. The corresponding configurations are located at the boundary of the workspace.

For parallel manipulators which may have more than one inverse kinematic solution, type-1 singularities are configurations where two solutions to the inverse kinematic problem meet. By hypothesis, type-1 singularities will be always associated with joint limits in this paper.

Type-2 singularities

They occur when det(A) = 0. Unlike the preceding ones, such singular configurations occur inside the workspace. They correspond to configurations for which two branches of the direct kinematic problem meet. They are particularly undesirable since the manipulator cannot be steadily controlled in such configuration where the manipulator stiffness vanishes in some direction.

For the planar manipulator, such configurations are reached whenever the axes of the three prismatic joints intersect (possibly at infinity). In such configurations, the manipulator cannot resist a wrench applied at the intersecting point (Figure 4).

The resulting singular surface is built and modelled using octrees (Figure 5). The equation of Det(A) can be put in an explicit form y = s(x,φ), only two variables need to be swept in the octree enrichment process

NOTION OF ASPECT FOR PARALLEL MANIPULATORS

The notion of aspect was introduced by [Borrel 86] to cope with the existence of multiple inverse kinematic solutions in serial manipulators. An equivalent definition was used in [ Khalil 96] for a special case of parallel manipulators, but no formal, more general definition has been set. The aspects are redefined formally in this section.

DEFINITION

Let OS m and JS n denote the operational space and the joint space, respectively. OS m is the space of configurations of the moving platform and JS n is the space of the actuated joint vectors. Let g be the map relating the actuated joint vectors to the moving platform configurations :

g OS JS X q g X m n : ( ) → → = (7)
It is assumed m = n, that is, only non-redundant manipulators will be studied in this paper. Let W be the reachable workspace, that is, the set of all positions and orientations reachable by the moving platform [Kumar 92], [ Pennock 93]. Let Q be the reachable joint space that is, the set of all joint vectors reachable by actuated joints.

{ }

Q q JS i n q q q Q JS n i i i n = ∈ ∀ ≤ ≤ ≤ ⊂ , , , min max (8)
( )

Q g W W OS m = ⊂ , (9)
Definition 1:

The aspects WA i are defined as the maximal sets such that :

• WA i ⊂ W ;

• WA i is connected ;

• ∀ X ∈ WA i , ( ) Det A ≠ 0 .
In other words, the aspects are the maximal singularity-free connected regions in the workspace.

The aspects are computed as the connected components of the set obtained by removing the singularity surfaces from the workspace, which can be done easily with the octree model :

∪ = - WA W S i (10)

Application :

For the planar manipulator studied, we get two aspects (WA 1 and WA 2 ), where Det(A) > 0 and Det(A) < 0, respectively. The singular surface of Figure 5 is the common boundary of the two aspects (Figure 6). In [Innocenti 92], a non-singular configuration changing trajectory was found for the planar manipulator. However, it appears that this trajectory passes close to a singular configuration. We have been able to confirm that non-singular configuration changing trajectories do exist for this robot. For the following input joint values : . .

(11)

The solutions to direct kinematic problem are (Table 1) :

x y Table 1 : Six direct kinematic solutions for the planar manipulator It can be verified that solutions -2-, -3-, -6-are in the same aspect (WA 1 ) (Figure 7).

CHARACTERISTIC SURFACES 4.1 DEFINITION

The characteristic surfaces were initially introduced in [Wenger 92] for serial manipulators. This definition is restated here for the case of parallel manipulators.

Definition 2 :

Let WA an aspect in workspace W. The characteristic surfaces of the aspect WA, denoted S c (WA), are defined as the preimage in WA of the boundary WA that delimits WA (Figure 8) :

( ) ( ) ( ) S WA g g WA WA c = ∩ -1 (12)
where :

• g is defined as in (15)

• g -1 is a notation. Let B ⊂ Q : ( ) { } g B X W g X B - = ∈ ∈ 1 ( ) /
The boundaries WA of WA are composed of :

• the type-2 singularities ;

• the type-1 singularities (limits of the actuated joints).

-RPR

MANIPULATOR

The characteristic surfaces are computed using definition (12). The singular surfaces are scanned and their preimages in the joint space are calculated using g. The resulting inverse singularities are mapped back into the workspace using the direct kinematic model. We get one characteristic surface for each aspect, denoted S c1 and S c2 , respectively. Figure 9 depicts the singularity surface S along with the characteristic surface S c1 .

WA S WA C ( ) ( ) WA WAb S WA i I i C = ∪ ∪ ∈ (13)
Definition 4 :

Let QA bi = g(WAb i ), QA bi is a domain in the reachable joint space Q called basic components. Let WA an aspect and QA its image under g. The following relation holds :

( ) ( ) ( ) QA QAb g S WA i I i C = ∪ ∪ ∈ (14)
Proposition 1 :

The basic components of a given aspect are either coincident, or disjoint sets of Q.

Theorem 1 :

The restriction of g to any basic region is a bijection. In other words, there is only one direct solution in each basic region.

Proof :

We define the function F of WA QA × in QA (where QA = g(WAb)) such that :

( ) ( ) ( ) ∀ ∈ × = - X q WA QA F X q g X q , , , (15)
F is a continuous and differentiable function on WA QA × . Let QAb i be any basic component and let

WAb i be such that ( )

QAb g WAb i i = .
Let (X 0 , q 0 ) be an arbitrary point in WAb QAb i i × such that ( )

F X q 0 0 0 , = .
Since ( )

X q WAb QAb i i 0 0 , ∈ × , ( ) Det F X X q ∂ ∂ 0 0 0 , ⎛ ⎝ ⎜ ⎞ ⎠ ⎟ ≠ .
Then, the implicit function theorem tells us that there exists a neighbourhood U of X 0 in WAb i and a neighbourhood V of q 0 in QAb i such that, for any q in V, equation F(X, q) has one unique solution X = f 1 (q) in U.

Let f 2 be another solution to equation ( ) ( )

F f q q 2 0 , =
and such that ( ) ( )

f q f q 1 0 2 0 = .
Since q 0 is the image of a configuration lying neither on the boundary nor on a singularity, f 2 is well defined at q 0 , and

( ) ( ) Det F X f q q ∂ ∂ 2 0 0 0 , ⎛ ⎝ ⎜ ⎞ ⎠ ⎟ ≠ .
If we prove that ( ) ( )

f q f q 1 0 2 0 = .
for any point q in QAb i , theorem 1 will be proved.

Let

( ) ( ) { } C q QAb f q f q i = ∈ = / 1 2 :
we have to prove that C = QAb i . C is a not empty since it contains points q 0 . C is a closed set in QAb i since C is the set of all the roots of ( ) ( )

f q f q 2 1 0 - = . Now ( ) ( ) Det F X f q q ∂ ∂ 2 0 , ⎛ ⎝ ⎜ ⎞ ⎠ ⎟ ≠ for any point q in C,
since QAb i and thus C does not contain points which are the image under g of a singularity. Therefore, it stems from the implicit function theorem that C has a neighbourhood of each of its points, and thus is also an open set in QAb i . Since QAb i is connected, the only subsets of QAb i which are open an closed at the same time are QAb i and the empty set. Since C is not empty, C = QAb i and the theorem is proved.

Application :

The basic regions are calculated as the connected components of the set obtained by removing the characteristic surfaces from the aspects :

∪ = - WA WA S bi i ci (16)
We obtain thus 28 basic regions for the planar manipulator at hand (Figure 10). We notice that, in accordance with proposition 1, the basic components are either coincident or disjoint. The coincident components yield domains with 2, 4 or 6 solutions for the direct kinematic problem : the upper one domains contain two coincident basic components, the middle five domains are composed of four coincident domains, and the last two domains contain six coincident basic components (Figure 11).

X Y φ

UNIQUENESS DOMAINS

Theorem 1 yields sufficient conditions for defining domains of the workspace (the basic regions) where there is one unique solution for the direct kinematic problem. However, the basic regions are not the maximal uniqueness domains. The following theorem 2 intends to define the larger uniqueness domains in the workspace.

Six coincident basic components in each domain

Two coincident basic components in each domain

Four coincident basic components in each domain

ρ 1 ρ 2 ρ 3 ρ 1 ρ 2 ρ 3 ρ 1 ρ 2 ρ 3 ρ 1 ρ 2 ρ 3 ρ 1 ρ 2 ρ 3 ρ 1 ρ 2 ρ 3 ρ 1 ρ 2 ρ 3
( ) ( ) Wu WAb Sc I k i I i = ∪ ∪ ∈ ' ' (18) with I' ⊂ I such as ∀ ∈ i I 1 2 ,i ' , ( ) ( ) g WAb g WAb i i 1 2 ∩ =∅.

Proof :

Since the basic regions which define the Wu k are such that their preimages in the joint space do not overlap, there is still one unique solution in each Wu k . Application :

To build the uniqueness domains, we have to consider the adjacent basic regions corresponding to disjoint, adjacent basic components. Six uniqueness domains have been found for the planar manipulator (Figure 12), that is as many as the number of direct kinematic solutions. Note that in general, the number of uniqueness domains should be always more or equal to the maximal number of direct kinematic solutions. We notice that, in the joint space, a non-singular configuration changing trajectory has to go through a domain made of only two coincident basic components, that is, a domain where there are only two direct kinematic solutions (one in each aspect). In addition, it is worth noting that the domain with six coincident basic components map into six basic regions which are linked together by singular surfaces. This means that a non-singular configuration changing trajectory cannot be a straightforward motion between two such basic regions, but should pass through another intermediate basic region (Figure 13).

Figure 1

 1 Figure 1 : 3-RPR planar manipulator The dimensions of the platform are the same as in [Merlet 90] and in [Innocenti 92] : • A 1 = (0.0, 0.0) B 1 B 2 = 17.04 • A 2 = (15.91, 0.0) B 2 B 3 = 16.54 • A 3 = (0.0, 10.0) B 3 B 1 = 20.84 The limits of the prismatic actuated joints are those chosen in [Innocenti 92] : 10 0 32 0 . . ≤ ≤ ρ i

  Figure 2 : Octree model of the joint space

Figure 5 :

 5 Figure 4 : Type-2 singular configurations Figure 5 : Octree model of the set of type-2 singularities in the workspace

  Finding the solutions X to equation q= g(X) means solving the direct kinematic problem. For our planar parallel manipulator, it has been shown that the direct kinematic model can admit six real solutions [Gosselin 91].

  Figure 6 : Octree model of the aspects 3.2 NON-SINGULAR CONFIGURATION CHANGING TRAJECTORIES

Figure 7 :

 7 Figure 7 : Three direct kinematic solutions in one single aspect This example clearly shows that the aspects are not the uniqueness domains. Additional surfaces have to be defined for separating the solutions.

Figure 8 :

 8 Figure 8 : Definition of the characteristic surfaces 4.2 CASE

Figure 9 :

 9 Figure 9 : Octree model of the singularities and of the characteristic surfaces S c1 5. UNIQUENESS DOMAINS 5.1 BASIC COMPONENTS AND BASIC REGIONS Definition 3 : Let WA be an aspect. The basic regions of WA, denoted { } WAb i I i , ∈ , are defined as the connected components of the set ( )

Figure 10 :

 10 Figure 10 : Octree model of the basic regions The basic components are computed as : ( ) QA g WAb i i =

Figure 11 :

 11 Figure 11 : Octree model of the basic components Theorem 2 : The uniqueness domains Wu k are the union of two sets : the set of adjacent basic regions ( ) ' ∪ ∈ i I i WAb of the same aspect WA whose respective preimages are disjoint basic components, and the set S c (I') of the characteristic surfaces which separate these basic components :

Figure 12 :1 ρ 2 ρ 3 Figure 13 :

 12313 Figure 12 : Octree model of the six uniqueness domains

& -( & means the difference between sets). The basic regions induce a partition on WA :


Ibrahim Sadek

Jit Biswas

Bessam Abdulrazak

Zhang Haihong

Mounir Mokhtari

Mounir Mokhtari Continuous

Continuous and Unconstrained Vital Signs Monitoring with Ballistocardiogram Sensors in Headrest Position

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

Continuous and Unconstrained Vital Signs Monitoring with Ballistocardiogram Sensors in Headrest Position

Ibrahim Sadek, Member, IEEE, Jit Biswas, Bessam Abdulrazak, Zhang Haihong, Mounir Mokhtari

Abstract-Unobtrusive and long-term monitoring of human vital signs are essential requirements for early diagnosis and prophylaxis due to many reasons, one of the most important being improving the quality of life. Currently, vital signs are continuously monitored through sensors attached to the body, such as multiple electrodes for measuring electrical activity of the heart. Such methods may be undesirable, especially for elderly, infants and other groups of people. In this paper, we introduce an improved technique for measuring heart rate from noisy ballistocardiogram signals acquired from 50 human volunteers in a sitting position using a massage chair. The signals are unobtrusively collected from a microbend fiber optic sensor embedded within the headrest of the chair, and then transmitted to a computer through a Bluetooth connection. The heart rate is computed using the multiresolution analysis of the maximal overlap discrete wavelet transform. The error between the proposed method and the reference ECG is estimated in beats per minute using the mean absolute error, where the system achieved relatively good results (7.31 ± 1.60) despite the large amount of motion artifacts produced owing to the frequent body movements and/or vibrations of the massage chair during stress relief massage. Unlike the complete ensemble empirical mode decomposition algorithm, previously employed for heart rate estimation, the suggested system is much faster. Hence, it can be used in real-time applications.

I. INTRODUCTION

Unobtrusive monitoring of vital signs is an increasing requirement for the medical community due to a number of reasons that may be outlined as follows: a) increased need for the recording of vital signs continuously under normal life conditions, i.e., for days and weeks, which is not achievable in hospitals; b) increased numbers of residents at assisted living facilities and numbers of elderly living alone in their own homes, caused by rapid increases in the aging population with need to self-monitor vital signs; c) the increased number of people with chronic diseases, giving rise to a need for self and remote monitoring of vital signs [START_REF] Shafiq | Automatic identification of systolic time intervals in seismocardiogram[END_REF]; d) increased need for health care providers to accurately measure vital signs of their clients; e) the issue of rising health care costs Ibrahim Sadek is with Image and Pervasive Access Laboratory (IPAL), CNRS UMI 2955, Singapore, Télécom ParisTech, Institut Mines Télécom, France, Institute for Infocomm Research (I 2 R), Singapore (email: stuis@i2r-astar.edu.sg)

Jit Biswas is with Information Systems Technology and Design (ISTD), Singapore University of Technology and Design, Singapore (email: jit biswas@sutd.edu.sg)

Bessam Abdulrazak is with Department of Computer Science, Facult des sciences, Universit de Sherbrooke (UdeS), Canada (email: Bessam.Abdulrazak@usherbrooke.ca)

Zhang Haihong is with Institute for Infocomm Research (I 2 R), Singapore (email: hhzhang@i2r.a-star.edu.sg)

Mounir Mokhtari is with Image and Pervasive Access Laboratory (IPAL), CNRS UMI 2955, Singapore, Institut Mines Télécom, France (email: mounir.mokhtari@mines-telecom.fr) throughout the world [START_REF] Zheng | Unobtrusive sensing and wearable devices for health informatics[END_REF]. As an example, an elderly person may have the condition of sleep-disordered breathing (SDB). The SDB, better known as the obstructive sleep apnea (OSA) syndrome and associated cardiovascular complications are one of the most common clinical disorders; OSA is expected to influence approximately 14% of men and 5% of women in the general population [START_REF] Kimoff | 88 -obstructive sleep apnea[END_REF]. The gold-standard approach to diagnose OSA is known as polysomnography (PSG), the PSG test should be performed in a specialist sleep clinic for a complete overnight. In principle, the sleep test includes many sensors placed on the patient body to record specific body functions such as the heart's electrical activity, brain's electrical activity, breathing, thoracoabdominal movement, blood oxygen saturation, body movement, etc. The PSG system provides accurate and real-time data. However, it imposes many limitations, i.e., complexity, invasiveness, high cost, and absence of privacy. Advanced development in hardware technology and signal processing tools enables noninvasive and unobtrusive sensing of vital signs. An alternative approach which may help diagnose OSA and other cardiovascular diseases, is the ballistocardiography. The ballistocardiogram (BCG) signal records the mechanical activity originating from the rebound of the body, generated when the blood is pumped out of ventricles into the large blood vessel synchronous with each heart beat. BCG sensors such as the microbend fiber, may be embedded in ambient locations such as mattresses, pillows, chairs, beds, or even weighing scales [START_REF] Inan | Ballistocardiography and seismocardiography: A review of recent advances[END_REF], in order to measure BCG. Some common BCG sensing technologies in literature are microbend fiber optic sensors, fiber Bragg grating sensors, piezoresistive fabric sensors, electromechanical film and polyvinylidenefluoride film based sensors [START_REF] Zheng | Unobtrusive sensing and wearable devices for health informatics[END_REF], [START_REF] Inan | Ballistocardiography and seismocardiography: A review of recent advances[END_REF]. One of the main advantages of the microbend fiber is that due to its immunity to electrical and electromagnetic interference it is a very suitable tool to be implemented in the magnetic resonance imaging environment. Other advantages include small size, light weight, and lower price. Additionally, the sensor is an appropriate choice for unconstrained continuous monitoring of vital signs as it is highly sensitive to pressure changes induced due to the ballistic forces on the heart, while not required to be in close contact with the body. The contribution of the current paper is to measure interbeat intervals (IBIs) from human subjects resting in a massage chair through a microbend fiber optic sensor (FOS) embedded in the headrest of the chair by utilizing the maximal overlap discrete wavelet transform (MODWT).

II. RELATED WORK

In healthy subjects, the electrocardiogram (ECG) signal, which is considered as a reference to measure IBIs has a uniform and repeated template known as PQRST complex, i.e., cardiac cycle. Thus, this property facilitates the measurement of the subject's heart rate. Unlike ECG signals, the BCG morphology varies between and within subjects, and the shape of the signal is highly dependent on the subject's positions, i.e., sleeping or sitting. In addition, the raw signal is noisy and non-stationary owing to body movement, induced respiratory efforts, and the characteristics of the sensing system itself. Therefore, estimating IBIs from BCG signals is a troublesome procedure. In [START_REF] Jin | A novel heart rate detection algorithm in ballistocardiogram based on wavelet transform[END_REF] a translation-invariant adaptive discrete wavelet transform (DWT) is proposed to denoise BCG signals. Then, the heart rate (HR) is computed using a pseudo-period detection approach. In [START_REF] Noh | Development of the bcg feature extraction methods for unconstrained heart monitoring[END_REF] DWT is implemented to cancel related BCG artifacts and a template matching for IBIs detection. The BCG data is collected from five healthy subjects in a sitting position using an electromechanical film sensor. In [START_REF] Gilaberte | Heart and respiratory rate detection on a bathroom scale based on the ballistocardiogram and the continuous wavelet transform[END_REF] continuous wavelet transform (CWT) is introduced for HR and respiratory rate measurements, where in each case, the scale which matches the periodicity of the signal is selected. The proposed approach is applied to six healthy subjects standing on a bathroom scale equipped with multiple strain gages. A similar approach is proposed in [START_REF] Alvarado-Serrano | An algorithm for beat-to-beat heart rate detection from the bcg based on the continuous spline wavelet transform[END_REF], where authors used CWT with splines for optimal scale selection. However, this approach required a training phase for parameter initialization. The BCG data is acquired from seven seated healthy subjects via a piezoelectric sensor. We implemented multiresolution analysis decomposition using MODWT since the MODWT overcomes the time variant drawback of the classical DWT by upsampling the filter coefficients [START_REF] Percival | Wavelet methods for time series analysis[END_REF].

III. METHODOLOGY

A. Experimental Setup and Data Collection

The configuration of the microbend FOS implemented in our experiment is shown in Fig. 2. The system encompasses a mat, which is embedded with microbend FOS and a transceiver. The FOS data is transmitted wirelessly to a computer through a Bluetooth connection with a sampling frequency of 50Hz. If a pressure force is introduced to the sensing mat, the separation between the two microbenders (tooth blocks) changes. Hence, the sinusoidal amplitude of the squeezed multimode optical fiber alternates due to the ballistic forces on the heart. This ballistic force modulates the intensity of the light passing through the fiber and this modulation is subsequently recovered as a ballistocardiogram signal. The BCG signals are unobtrusively acquired from a group of 50 healthy subjects resting in a massage chair, while the sensor is embedded in the headrest of the chair. During data acquisition, subjects are instructed to complete predefined sessions, i.e., answering questionnaires, rest (no movement), and stress relief massage. At the same time, ECG signals are also collected to appraise the system performance in the HR estimation. Fig. 3 shows an example of a BCG signal with its ECG reference. Since subjects are performing multiple tasks, there are different scenarios for BCG data acquisition, i.e., good signals, noisy signals, and no signals. In the first, the subject is sitting still during the rest period. In the second, during the massage session, the BCG signal is strongly affected by the chair vibration. At last, the contact between the sensor mat and the subject head might be lost while the subject is filling in the questionnaire.

Tooth Blocks

Multimode

B. Hardware Description

The introduced algorithm is implemented using MATLAB (R2015b, MathWorks Inc., MA) on a windows based laptop platform (Intel core i5-4200U, 2.4GHz and 6GB RAM).

C. Maximal Overlap Discrete Wavelet Transform

Discrete Wavelet transform analysis is an adequate tool for transforming a time-domain signal into a time-frequencydomain signal and contrariwise. The maximal overlap discrete wavelet transform shares some common characteristics with the DWT, i.e., at each stage the input signal is convolved with a series of low-pass and high-pass filters. However, it omits the decimation of wavelet coefficients. Although the MODWT does not provide an orthogonal decomposition, it has some advantages over the DWT. For example, it is a translation-invariant approach and can manipulate any sample size n, which is not necessary to be divisible by two. Moreover, the detail and smooth coefficients of the MODWT are affiliated with zero-phase filters. Hence, it is applicable to align features in a multiresolution analysis in a meaningful way along with the original time series [START_REF] Percival | Wavelet methods for time series analysis[END_REF]. The MODWT decomposes a finite time signal U t into wavelet coefficients (W k,t ) and approximation coefficients (V k,t ); k denotes the decomposition level, and t denotes the time, where k = {1, . . . , K}, t = {1, . . . , N -1}, K represents the number of scales, and N denotes the number of time points. The MODWT wavelet (W k,t ) and approximation (V k,t ) coefficients for a signal U t including N time points are derived as detailed below:

W k,t = L k -1 l=0 h k,l • U t-lmodN
(1)

V k,t = L k -1 l=0 g k,l • U t-lmodN (2)
The length of equivalent MODWT wavelet (h k,l ), and approximation (g k,l ) filters are defined such as:

L k = (2 k -1)(L -1) + 1 (3)

D. Heart Rate Detection

A sliding window of a length (10 seconds/500 samples) is used to compute the HR for BCG and ECG signals. The proposed system is presented in Fig. 4 and can be elaborated as discussed below: 1) BCG Signal Extraction: The raw data of the microbend sensor consists of multiple components, i.e., BCG signals, respiratory signals, and body movements. Body movements are eliminated using a moving window of a size 1 second/50 samples with 50% overlap. Thereafter, for each window if the difference between the maximum and minimum (range) is greater than a predetermined threshold, the current window is discarded. The BCG signal is retrieved by employing a bandpass Butterworth filter with frequency limits between 1Hz and 10Hz. 2) Decomposition: For each 10 seconds of the BCG signal, a multiresolution analysis based on MODWT is applied to decompose the signal into approximation and detail coefficients. 3) Suitable Level Selection: The 4 th level smooth coefficient is preferred for HR computation because the periodicity of the maxima well matches with the heart beats as presented in Fig. 5.

IV. RESULTS AND DISCUSSION

In our study, a MODWT with level four, and 8 th order Symlets (Symlet-8) is applied to a BCG time series of 10 seconds to compute the HR. The Symlet-8 is selected for the decomposition as discussed in [START_REF] Jin | A novel heart rate detection algorithm in ballistocardiogram based on wavelet transform[END_REF], because the outline of the scaling function is similar to the profile of the BCG signal. The HR is calculated in beats per minute (BPM) for the two-time series. The mean and standard deviation (Std) of the mean absolute error (MAE) between ECG and BCG signals are computed across all subjects to check the quality of the proposed approach with regard to HR detection. The work proposed in [START_REF] Sadek | Automatic heart rate detection from fbg sensors using sensor fusion and enhanced empirical mode decomposition[END_REF], [START_REF] Sadek | Sensor data quality processing for vital signs with opportunistic ambient sensing[END_REF] suggested to utilize the complete ensemble empirical mode decomposition with an adaptive noise (CEEMDAN) method to decompose the BCG signal into amplitude modulated -frequency modulated functions known as intrinsic mode functions (IMFs). Then, selecting the IMF that best represents the heart beats. The results were promising since the CEEMDAN algorithm was able to overcome the limitations of the original empirical mode decomposition (EMD) algorithm such as end effects and mode mixing. A comparison between the CEEMDAN algorithm and the proposed MODWT multiresolution analysis is implemented to examine the performance of each method. In many situations, the MODWT method is able to handle the motion artifacts originated during the massage session.

As shown in Fig. 7, the algorithm managed to detect all the corresponding J-Peaks in the noisy BCG signal. On the other hand, sometimes the MODWT detects more / less peaks than the reference ECG, which is not taken into account for HR estimation. Usually, this situation arises because of the induced motion artifacts. Furthermore, during the massage period the ECG electrodes might not be attached correctly to the subject body. As a result, incorrect synchronization between both signals occurred.

To sum up, in spite of the unstable environment employed to collect BCG signals, the MODWT managed to deal with motion artifacts caused by body movements and vibrations of the massage chair during relief therapy with reasonably good results.

V. CONCLUSION

In this study, a new approach is developed to measure human vital signs using BCG signals produced by a microbend FOS pressure mat embedded in the headrest of a massage chair. The proposed system is completely noninvasive and unobtrusive, where no electrodes are attached to the human body and the data can be transmitted to a personal computer via a Bluetooth connection or to a server through Wi-Fi. The HR is computed using multiresolution analysis based on MODWT, where the smooth coefficient of the wavelet decomposition is chosen to compute the HR, since the periodicity of the local maxima matches with the heart beats. The MODWT attains relatively good results against the reference ECG despite the many challenges related to motion artifacts. The MODWT is much faster than the CEEMDAN algorithm. Thus, it is an appropriate tool for real-time vital signs monitoring.

Fig. 1 .

 1 Fig. 1. Unobtrusive remote monitoring of vital signs.

Fig. 1

 1 Fig. 1 emphasizes how the FOS is used in a wellness application for the unobtrusive monitoring of vital signs.

Fig. 2 .

 2 Fig. 2. Basic microbend fiber optic sensor.

Fig. 3 .

 3 Fig.3. BCG signal with its reference ECG signal, J-Peaks (dominant BCG peaks) represent heart beats as similar to R-Peaks in ECG.

Fig. 4 .

 4 Fig. 4. The flowchart of the proposed HR estimation method; BM: Body Movement, RR: Respiratory Rate, and MRA: Multiresolution Analysis.

Fig. 5 .

 5 Fig. 5. Symlet-8 MODWT multiresolution decomposition of a BCG signal.

Fig. 7 .

 7 Fig. 7. BCG signal with the 4 th level smooth coefficient during a massage session.

Local Server Remote Server or Cloud Remote Monitoring Sensor and Transceiver PC For Data Collection and Processing Massage Cahir Table PC Stand For Table PC Game Controller PC For Hosting Games and Presenting Animation Results and Final Statistics

TABLE I THE

 I MEAN AND STD OF ERROR FOR MODWT AND CEEMDAN, AND THE RUN TIME OVER 10 SECONDS SIGNAL. TableIpresents the mean and Std of the error for both methods as well as the run time of 10 seconds signal. In addition, Fig.6shows box plots of the average MAE for MODWT and CEEMDAN methods. Even though the error of the CEEMDAN algorithm (6.81 ± 1.15) is slightly lower than the error for the MODWT (7.31 ± 1.60), the MODWT is much faster than CEEMDAN algorithm. Subsequently, the MODWT is more suitable for real-time applications.

		MAE (Average)	MAE (Std)	Run Time (Sec)
	MODWT	7.31	1.60	0.04
	CEEMDAN	6.81	1.15	20
	The CEEMDAN is applied with a noise standard deviation
	of 0.35, an ensemble size of 100, and a maximum number of
	5 11 siftings of 30. MODWT 6 7 8 9 10 Average Mean Absolute Error (MAE)	CEEMDAN
			Methods
	Fig. 6. Box plots of the average MAE for both CEEMDAN and MODWT
	methods.


Damien Chablat
email: damien.chablat@ircyn.ec-nantes.fr

Philippe Wenger

Jorge Angeles

Jorge Angeles The Kinematic

The Kinematic design of a 3-dof Hybrid Manipulator

teaching and research institutions in France or abroad, or from public or private research centers.

Introduction

It is worth noting that most industrial manipulators have a serial kinematic architecture, that is, their links are arranged serially, resulting in a cantilever type structure. The serial kinematic arrangement of links produces large workspaces but suffers from high positioning errors and poor stiffness. Another well know but far less widespread kinematic architecture is the fully-parallel one for which the output link is connected to the ground through several « legs ». Fully-parallel kinematic architectures are known for their high stiffness and low positioning errors but suffer for relatives small workspace. They had been used for a long time in flight simulators and, more recently, in robotic and machine tool applications. The idea of mixing the above two kinds of kinematic arrangement in a single « hybrid » architecture is more recent and still too poorly exploited, despite of the potential benefits which can be gained with such architecture. This paper focuses on the kinematic properties of a new three-degree-of-freedom hybrid manipulator. This manipulator is obtained by adding in series to a five-bar planar mechanism a third revolute passing through the line of centers of the two actuated revolute joints of the above linkage (Figures 2 &3). The resulting architecture is hybrid in that it has both serial and parallel links. The hybrid manipulator studied is intrinsically stiffer and more accurate than the classical 3-revolute-jointed 3-DOF fully serial « elbow » manipulator (Figure 1). Furthermore, since all actuators are located on the first axis, the inertial effects are considerably reduced. In addition, it is shown that the special kinematic structure of our manipulator has the potential of avoiding parallel singularities by a suitable choice of the « working mode », thus leading to larger workspaces. The main kinematic equations of the hybrid manipulator are derived. Two Jacobian matrices appear in the kinematic relations between the joint-rate and the Cartesianvelocity vectors, which are called the « inverse-kinematics » and the « direct-kinematics matrices ». These matrices enable the determination of the serial and parallel singularities, which govern the global behavior of the manipulator and define the topological structure of the workspace in Cartesian and joint spaces. The influence of the different structural dimensions (e.g. the link lengths) on the kinematic and mechanical properties are analyzed in view of the optimal design of such hybrid manipulators.

Preliminaries

A TWO-DOF CLOSED-CHAIN MANIPULATOR

The closed-chain manipulator which constitutes the parallel array of the hybrid manipulator is a five-bar, revolute (R)-coupled linkage, as displayed in figure 2. The actuated joint variables are θ 1 and θ 2 , while the Cartesian variables are the (x, y) coordinates of the revolute center P. To decrease the inertia effects of moving bodies, we place actuated joints of the closed-chain onto pivots A and B. Lengths L 0 , L 1 , L 2 , L 3 , and L 4 define the geometry of this manipulator entirely. However, in this paper we focus on a symmetrical manipulators, with L 1 = L 3 and L 2 = L 4 . The symmetrical architecture of the manipulator at hand is justified for general tasks. In manipulator design, then, one is interested in obtaining values of L 0 , L 1 , and L 2 that optimize a given objective function under some prescribed constraints.

A THREE-DOF HYBRID MANIPULATOR

Now we add one degree of freedom to the manipulator of figure 2. We do this by allowing the overall two-dof manipulator to rotate about line AB by means of a revolute coupling the fixed link of the above manipulator with the base of the new manipulator. We thus obtain the manipulator of figure 3.

KINEMATIC RELATIONS

The velocity . p of point P can be obtained in two different forms, depending on the direction in which the loop is traversed, namely, . p = . c + ( .

θ 1 j + . θ 4 k) × (p -c) ( 1a ) and .
p = . d + ( . θ 1 j + . θ 5 k) × (p -d) ( 1b )
The equations (1a & b) can be shown to lead to the following 3-dimensional vector equation relating joint and Cartesian velocities [START_REF] Chablat | The isoconditioning Loci of A Class of Closed-Chain Manipulators[END_REF],

A . p = B . θ ( 2 ) where A ≡ ⎣ ⎢ ⎢ ⎡ ⎦ ⎥ ⎥ ⎤ L 2 k T (p -c) T (p -d) T ( 3 ) B ≡ L 1 L 2 ⎣ ⎢ ⎢ ⎡ ⎦ ⎥ ⎥ ⎤ sin(θ 2 ) + λ 1 sin(θ 4 ) 0 0 0 sin(θ 2 -θ 4 ) 0 0 0 sin(θ 3 -θ 5 ) ( 4 )
with λ 1 defined as λ 1 ≡ L 2 / L 1 , while vectors . ,θ and . ,p are given by .

θ = [ . θ 1 , . θ 2 , . θ 3 ] T , . p = [ . x , . y , . z] T ( 5 )

THE WORKING MODE

The manipulator under study has a diagonal inverse-kinematics matrix B, as shown in eq. ( 4), the vanishing of one of its diagonal entries thus indicating the occurrence of a serial singularity. The set of manipulator postures free of this kind of singularity is termed a working mode. The different working modes are thus separated by a serial singularity, with a set of postures in different working modes corresponding to an inverse kinematic solution. The formal definition of the working mode is detailed in [START_REF] Chablat | Domaines d'unicité des manipulateurs parallèles : Cas général[END_REF].

For the manipulator at hand, the closed chain admits eight working modes, four of which are depicted in figure 4, the remaining four being the mirror image of the first ones about line AB.

THE PARALLEL SINGULARITIES

Parallel singularities occur when the determinant of the direct kinematics matrix A vanishes, the corresponding singular configurations occurring inside the workspace. They are particularly undesirable because the manipulator can not resist efforts in some direction(s). To interpret these singularities, we calculate A A T : whence it is apparent that these singularities occur whenever θ 4 -θ 5 = k (π / 2), for an integer k, i.e., when the points C, D and P are aligned. In such configurations, the manipulator cannot resist an effort in the orthogonal direction of DC (Figure 5). Besides, when the points C and D coincide, the position of P is no longer controllable since P can rotate freely around D even if the actuated joints are locked (Figure 6). It will be shown in § 3.2 and § 3.3 that parallel singularities can be avoided either by design or by pathplanning.

A A T ≡ L 2 2 ⎣ ⎢ ⎢ ⎡ ⎦ ⎥ ⎥ ⎤ 1 0 0 0 1 cos(θ 4 -θ 5 ) 0 cos(θ 4 -θ 5 ) 1 ( 6 )

THE SERIAL SINGULARITIES

Serial singularities occur when the determinant of the inverse kinematics matrix B vanishes. When the manipulator is in such a singularity there exists a direction along which no Cartesian velocity can be produced (Figure 7). Such singularities are reached at the boundary of the workspace when BD and DP or AC and CP are aligned. They cannot be avoided.

Kinematic analysis and design

WORKSPACE

A possible design of the manipulator at hand is obtained upon maximizing its workspace volume, which is given by the intersection of two hollow spheres, where radii are L 1 + L 2 and L 1 -L 2 , the distance between the centers of these spheres being L 0 . Therefore, the workspace is maximum when L 0 is equal to 0 and, by extrapolating the results from [START_REF] Paden | Optimum kinematic design of 6R manipulators[END_REF], when L 1 is equal to L 2 . A cross section of the workspace of such an optimized manipulator is displayed in both Cartesian and joint spaces in figures 8 and 9. We notice that the optimum manipulator has only two operative working mode because the other two working modes lie in parallel singular configurations (see figures 4 b & c when L 0 = 0 and L 1 = L 2 ). Thus, all singularities of this mechanism lie at the border of the workspace.

AVOIDING PARALLEL SINGULARITIES BY PROPER DESIGN

We choose lengths allowing to avoid this configurations for which points C and D coincide. If the sum of lengths L 1 + L 1 is greater than the distance between the two pivots A and B, i.e. L 0 , we eliminate a parallel singularity type. In the same way, we can eliminate all parallel singularities if the condition below is imposed: 2 L 2 -2L 1 > L 0 In using this property, the mechanism has no parallel singularity (Figures 10 &11).

AVOIDING PARALLEL SINGULARITIES BY A CHANGE OF WORKING MODE

According to the working mode chosen, the parallel-singularity posture changes inside the workspace, as displayed in figure 12. In the « convex working mode » (Figure 12 left), the manipulator is in parallel singularity, while it is in a regular configuration in the non-convex working mode (Figure 12 right). Also, to execute operations in a highly constrained environment, it can be desirable to change working mode. It is possible, by means of a change of working mode, to reach points inside the two workspace sections displayed in figures 13 and 14.

To change working mode, it is necessary to pass through a serial singularity, located at the boundary of the Cartesian workspace. By doing so, we can reach a workspace that is twice as large as each of those displayed in figures 13 and 14. In fact, parallel singularities not being avoidable, the workspace of a parallel manipulator is always smaller than that of its serial counterpart of the same size. Also, according to the working mode, the condition numbers of the direct-and the inverse-kinematics matrices are different. Thus, according to the task to execute, requiring either a precise motion or a fast motion, we can choose one suitable working mode.

THE ISOCONDITIONING CURVES

Another interesting design criteria is the isoconditioning curves in the workspace ( [START_REF] Gosselin | Stiffness Mapping for Parallel Manipulators[END_REF] and [START_REF] Chablat | The isoconditioning Loci of A Class of Closed-Chain Manipulators[END_REF]). We derive below the loci of equal condition number of the direct-kinematics matrices.

To do this, we first recall the definition of condition number of an m × n matrix M, with m ≤ n, κ(M). This number can be defined in various ways; for our purposes, we define κ(M) as the ratio of the largest, σ l , to the smallest σ s , singular values of M, namely,

κ(M) = σ l σ s ( 7 )
The singular values {σ k } The condition number of matrix A is thus

κ(A) = 1 |tan((θ 4 -θ 5 ) / 2)| ( 8 )
These loci are, in fact, surfaces of revolution generated by the isoconditioning curves of the 2-dof manipulator, when these are rotated about the axis of the first revolute.

In light of expression (8) for the condition number of the Jacobian matrix A, it is apparent that κ(A) attains its minimum of 1 when |θ 3 -θ 4 |= π / 2, the equality being understood modulo π. At the other end of the spectrum, κ(A) tends to infinity when θ 3 -θ 4 = k π, for k= 1, 2, ... . When matrix A attains a condition number of unity, it is termed isotropic, its inversion being performed without any roundoff-error amplification. Manipulator postures for which condition θ 3 -θ 4 = π / 2 holds are thus the most accurate for purposes of the direct kinematics of the manipulator. Correspondingly, the locus of points whereby matrix A is isotropic is called the isotropy locus in the Cartesian workspace.

On the other hand, manipulator postures whereby θ 3 -θ 4 = k π denote a singular matrix A, and hence, define the boundary of the Cartesian workspace of the manipulator. Such singularities occur at the boundary of the Cartesian workspace of the manipulator, and hence, the locus of P whereby these singularities occur, namely, the singularity locus in the Cartesian space, defines this boundary. Interestingly, isotropy can be obtained regardless of the dimensions of the manipulator, as long as i) it is symmetric and ii) L 2 ≠ 0. For the two working modes, the position of the isotropic configurations are different (Figure 15). The isoconditioning curves are, by definition, the sets of points which are at equal distance from the singularities and, in turn, can be used as a criterion for designing and/or placing the manipulator in such a way that the working trajectories be in a region of the workspace where a minimum stiffness is guaranteed.

Conclusions

We have defined a novel architecture of hybrid manipulators and produced design and path-planning guidelines for the implementation of these manipulators. Two Jacobian matrices were identified in the mapping of joint rates into Cartesian velocities, namely, the direct-kinematics and the inverse-kinematics matrices.

The hybrid manipulators studied were optimized for maximum Cartesian workspace volume and iso-conditioning. Further research work is being conducted by the authors on such hybrid manipulators with regard to their optimal design.

Figure 1 .

 1 Figure 1. The « elbow » manipulator Robot anthropomorphe

Figure 2 . 3 .

 23 Figure 2. A two-dof closed-chain manipulator Figure 3. The three-dof hybrid manipulator

Figure 4 .

 4 Figure 4. The four working modes

Figure 5 .

 5 Figure 5. Parallel singularity Figure 6. Parallel singularity

Figure 7 .

 7 Figure 7. Serial singularity

Figure 8 .Figure 9 .

 89 Figure 8. A cross section of the Cartesian workspace for L 0 = 0

Figure 10 .Figure 11 .

 1011 Figure 10. Cross-section of the workspace free of parallel singularities

Figure 12 .

 12 Figure 12. Working mode and parallel singularity

Figure 13 .

 13 Figure 13. Workspace of the convex working mode Figure 14. Workspace of the nonconvex working mode

m 1

 1 _of matrix M are defined, in turn, as the square roots of the nonnegative eigenvalues of the positive-semidefinite m × m matrix M M T . The eigenvalues of the matrix A A T (6) are, α 1 = 1 -|cos(θ 4 -θ 5 )|, α 2 = 1, and α 3 = 1 + | cos(θ 4 -θ 5 ) | [3], the foregoing eigenvalues having been ordered as α 1 ≤ α 2 ≤ α 3

Figure 15 .

 15 Figure 15. Isoconditioning curves for two working modes

Acknowledgments

The third author acknowledges the support from the Natural Sciences and Engineering Research Council, of Canada, the Fonds pour la formation de chercheurs et l'aide à la recherche, of Quebec, and École Centrale de Nantes (ECN). The research reported here was conducted during a sojourn that this author spent at ECN's Institut de Recherche en Cybernétique de Nantes.


Vincent Ribaud
email: ribaud@univ-brest.fr

Rory V O'connor
email: roconnor@computing.dcu.ie

Blending process assessment and employees' competencies assessment in Very Small Entities

Keywords: small entities, process assessment, competency framework. 1

The ISO/IEC 29110 series aims to provide Very Small Entities (VSEs) with a set of standards based on subsets of existing standards. Process capability determination does not seem suitable for a VSE in terms of return on investment. Our approach moves the viewpoint away from process and to the human resources. We propose a blended assessment model using the ISO/IEC 15504 for the level 1, but based on competency assessment for higher levels.

Introduction

Since 2011 the ISO/IEC 29110 [START_REF]Software Engineering --Lifecycle profiles for Very Small Entities --Part 1: Overview[END_REF] series provides Very Small Entities -VSE (up to 25 people) with a set of standards establishing a framework for software life cycle processes and helping VSEs in achieving capability recognition of their processes. A requirement for the Working Group 24 (of which the authors are members) mandated to develop the 29110 series was that processes should be assessed using ISO/IEC 15504 [START_REF]Information technology --Process assessment --Part 1: Concepts and vocabulary[END_REF] approach. A meta-analysis [START_REF] Pino | Software process improvement in small and medium software enterprises: a systematic review[END_REF] about case studies reporting process improvement approaches for 122 SMEs states that the ISO/IEC15504 model was used only in 9% of the reported improvement efforts, which would tend to support that a 15504-based approach for VSE process assessment may not be the most appropriate approach. Accordingly, the first research question addressed in this paper is: How small organizations or projects can use the ISO/IEC 29110 standard to effectively monitor their progress and to evaluate their performance?

Competency frameworks, such as the e-Competences Framework [START_REF]European e-Competence Framework 3.0-Part 1: A Common European Framework for ICT Professionals in All Industry Sectors[END_REF] focus on professional skills rather than organizational and technical processes. We propose that such information will be found more relevant by VSEs staff and furthermore that competency assessment helps ICT professionals by developing the right skills and by deploying them to best effect, it will, in time, improve understanding and performing software processes. Thus we define a second research question: How can we relate VSE process performance with employees' competencies proficiency? Section 2 overviews background work and section 3 Process Assessment Models. In section 4, we present a Competency Assessment Model for VSEs, and then we conclude the paper.

2

Background and Related Work

Standard Background

The documents in the ISO/IEC 29110 series are referred to as VSE profiles (organized within Groups) [START_REF]Generic profile group[END_REF] and are based on subsets of appropriate standards elements, which are relevant to the VSE context such as processes and outcomes of ISO/IEC 12207 [START_REF]Software life cycle processes[END_REF] and products of ISO/IEC 15289 [START_REF]Systems and SE --Content of life cycle process information products[END_REF]. The Basic Profile describes software development of a single application by a single project team with no special risk or situations factors [START_REF]Software Engineering --Lifecycle profiles for Very Small Entities --Part 1: Overview[END_REF]. The Basic Profile yields a comprehensive set of life cycle processes, activities and tasks, with input and output work products. The starting point for a VSE aiming to establish conformance to a profile is the use a Process Assessment Model, suitable for the purpose of assessing process capability, based on the targeted profile. One result presented in this paper is to formally exhibit the underlying Process Reference Model (PRM) contained into the ISO/IEC 29110 Basic Profile documents, and to propose a Process Assessment Model for the capability level 1.

A competency framework is intended to foster the development of skills, either by individuals or organizations. The European e-Competence Framework (www.ecompetences.eu/) is a reference framework of 40 ICT competences that can be used and understood by ICT stakeholders [START_REF]European e-Competence Framework 3.0-Part 1: A Common European Framework for ICT Professionals in All Industry Sectors[END_REF]. A competence is "a demonstrated ability to apply knowledge, skills and attitudes to achieving observable results [8]."

Following the recommended ISO/IEC 15504 approach, a Process Assessment Model (PAM) will expand the Basic Profile PRM by adding the definition and use of assessment indicators, either process performance indicators or process capability indicators. The latter are, in our opinion, too complex and too far from day-to-day VSE concerns. Our approach proposes to move the viewpoint from process perspective to human resource (i.e. the VSE staff). Job profiles contain many components describing the essential elements of a job and how it should be performed. Jobs profiles provide a bridge between enterprises and individuals, and establish the link between an organization processes and employees' competencies. It is our proposition that VSE employees should be motivated by competencies assessment related to their job profiles. It is also considered that assessing employees' competencies provide a correct indication of the VSE maturity as long as process and competency framework are correctly aligned.

Related Work

A lot of research has been performed on software process assessment for small companies based either on ISO/IEC 15504 [START_REF] Von Wangenheim | Helping Small Companies Assess Software Processes[END_REF][START_REF] Cater-Steel | Process Improvement in Four Small Software Companies[END_REF][START_REF] Rout | The Rapid Assessment of Software Process Capability[END_REF][START_REF] Oktaba | Software Process Improvement: The Competisoft Project[END_REF] or CMMI [START_REF] Grunbacher | A software assessment process for small software enterprises[END_REF][START_REF] Mc Caffery | Adept: A Unified Assessment Method for Small Software Companies[END_REF][START_REF] Habra | Initiating software process improvement in very small enterprises Experience with a light assessment tool[END_REF]. Almost all approaches aims to minimize the assessment time or are reducing the number of assessed processes or the number of resources involved. Several approaches are using process-area interviews (or questionnaires) as the central stage to collect evidences of process achievement. In [START_REF] Varkoi | Process Assessment In Very Small Entities -An ISO/IEC 29110 Based Method[END_REF], the authors propose the development of a novel process assessment model for VSEs using the ISO/IEC 29110. The proposed PRM is similar to ours, expected that base practices are extracted from ISO/IEC 15504-5 and based on the mapping to ISO/IEC 12207 outcomes. They limit the assessment model to process performance indicators, excluding capability levels higher than level 1. We are not aware of other research performed on software process assessment based on ISO 29110. [START_REF]Information technology --Process assessment --Part 1: Concepts and vocabulary[END_REF]. In the process dimension, individual processes are described in terms of Process Title, Process Purpose, and Process Outcomes as defined in ISO/IEC 12207. In addition to this PRM, the 15504 process dimension provides a set of Base Practices (BP); a number of input and output Work Products (WP); and characteristics associated with each work product [START_REF]Information technology --Process assessment --Part 1: Concepts and vocabulary[END_REF].

ISO/IEC 29110 Basic Profile Processes.

The Basic Profile [START_REF]Generic profile group[END_REF] is made of 2 processes: Project Management (PM) and Software Implementation (SI). Processes are described with: Name; Purpose; Objectives; Input, output, and internal products; Roles involved; Activities list and activities description. Clause 7 contains the specification of the standardized profiles and its conceptual model is represented in Figure 1. Clause 8 establishes the reference between the 29110 elements and the source standards [START_REF]SE --Lifecycle profiles for VSEs --Part 5-1-2: Management and engineering guide: Basic profile. ISO[END_REF] and its conceptual model is also represented in Figure 1.

As pointed out in [START_REF] Varkoi | Process Assessment In Very Small Entities -An ISO/IEC 29110 Based Method[END_REF], ISO/IEC 29110-4-1 cannot be considered as a Process Reference Model (PRM) per se, but the ISO/IEC 29110 set of documents is containing all materials required to build a PRM for the Basic Profile. A PRM is "a model comprising definitions of processes in a life cycle described in terms of process purpose and outcomes, together with an architecture describing the relationships between the processes [START_REF]Information technology --Process assessment --Part 1: Concepts and vocabulary[END_REF]." ISO/IEC 29110-4-1 provides the architecture and processes purposes. We only lack of outcomes and we created process outcomes using 12207 process outcomes referenced by each 29110 objective. This appears in Figure 1 with a dotted dependence link between 29110 and 12207 outcomes. The PRM we built is available at http://29110.univ-brest.fr/en.nexus.

A Process Assessment Model for VSEs

ISO/IEC 15504.

The capability dimension consists of six capability levels and nine Process Attributes (PA) for levels 1 to 5. A process attribute is "a measurable characteristic of process capability applicable to any process [START_REF]Information technology --Process assessment --Part 1: Concepts and vocabulary[END_REF]."

The ISO/IEC 15504 approach indicates that a Process Reference Model lacks of level of detail for conducting consistent and reliable assessments. Therefore, a) the PRM needs to be supported with a comprehensive set of indicators of process performance; and b) the capability levels and process attributes need to be supported with a set of indicators of process capability. A Deployment Package (DP) is a set of artifacts developed to facilitate the implementation of the ISO/IEC 29110 series. DPs are provided, at no cost, by a network of centers to support VSEs. Our research results use the set of available Deployment Packages to provide the set of indicators of process performance. In order to prepare our contribution to an Assessment Model for VSEs (see next section), we present in the left part of Figure 1, the conceptual model of the ISO/IEC 15504 Process assessment, mainly 15504 processes, outcomes, base practices and work products. The ISO/IEC 15504-5 provides an exemplar model for performing process assessments that is based upon and directly compatible with the Process Reference Model in ISO/IEC 12207. References appear in Figure 1 with a dotted dependence link between 15504 and 12207 elements.

ISO/IEC 15504 Performance Indicators.

ISO/IEC 15504 states the result of successful implementation of process assessment: information and data that characterize the processes assessed is determined; the extent to which the processes achieve the process purpose is determined [START_REF]Information technology --Process assessment --Part 1: Concepts and vocabulary[END_REF]Part 2]. This extent is derived from the process attributes ratings for an assessed process. The extent of achievement of a process attribute is measured on a scale using values: N Not achieved, 0 to 15 % achievement; P Partially achieved, > 15 % to 50 % achievement; L Largely achieved, > 50 % to 85% achievement; F Fully achieved, > 85 % to 100 % achievement.

Capability Level 0 denotes an incomplete process. Capability Level 1 denotes a performed process. Higher levels denote higher process maturity: the process is managed (Level 2), established (Level 3), predictable (Level 4), optimizing (Level 5).

Performing its business processes is the main concern of a VSE. That means that a VSE's main (and may be the unique one) goal in a Process Assessment is to be assessed at Capability Level 1 for each selected process. Therefore helping a VSE to perform process through a Capability Level 1 assessment will probably retain its attention and raise some investment. The rating of process performance indicators, which apply exclusively to capability level 1, should motivate VSEs. These indicators are BPs and WPs.

ISO 29110 Process Attributes.

Our first research question is asking how small organizations or projects can use the ISO/IEC 29110 standard to effectively monitor their progress and to evaluate their performance. Our answer is to focus on Base Practices and Work Products indicators.

Specifying BPs and WPs for the Basic Profile is submitted to the problem that ISO/IEC 29110 process granularity is too broad and we will specify BPs and WPs at the 29110 activity level. In an earlier work [START_REF] Ribaud | Process Assessment Issues of the ISO-IEC 29110 emerging standard[END_REF] about ISO/IEC 29110 Process Assessment Issues, we established the reduced set of ISO/IEC 15504 Processes and Base Practices that are related to 29110 Processes and Objectives thanks to a mapping between ISO 15504 BPs and 29110 processes. The merge of this earlier work and the work presented should be the basis to build an exemplar process assessment model for VSEs. This model shifts the viewpoint from process assessment to activity. Following this point of view, our contribution is to propose in the next section a set of BPs for each ISO/IEC 29110 activities.

ISO 29110 Performances Indicators.

In Part 5-1-2 [START_REF]SE --Lifecycle profiles for VSEs --Part 5-1-2: Management and engineering guide: Basic profile. ISO[END_REF], each activity is associated with a set of constitutive tasks that shall be considered as Base Practices. 6 Deployment Packages are provided with the Basic Profile. DP 1 [START_REF] O'connor | Deployment Package -Project Management[END_REF] covers the whole Project Management Process; DPs 2 to 6 [START_REF] Alexandre | Deployment Package -SW Requirement Analysis[END_REF][START_REF] Guillemot | Deployment Package -Software Design[END_REF][START_REF] Vasquez | Deployment Package -Construction and Unit Testing. 5th level[END_REF][START_REF] Gómez | Deployment Package -SW Testing[END_REF][START_REF] Laporte | DP -Product Delivery[END_REF]] cover all of the activities of Software Implementation Process. We carefully examined DPs 1 to 6, which cover the majority of the Basic Profile activities. Almost none excepted DP Software Design is using the standardized tasks decomposition and almost all -DP Software Design excepted -are providing alternative activity decomposition with input and output WPs. The analysis is available at http://29110.univ-brest.fr/en.nexus/index.php/AAB Each corresponding DP provides a task decompositionalthough not standardized and for each task, a step-by-step guideline to perform the task. Formally, the term 'task' should not be used in DPs and we will call 'sub-activity' the elements of the alternative activity decomposition provided in DPs.

Once the 4-level decomposition is established for the Basic Profile, we can map this decomposition with the 15504 Exemplar Process Assessment Model. Thus, subactivities play an equivalent role than 15504 Base Practices. Hence, within PM and SI processes, each activity will be assessed at Capability Level 1 on the basis of two Process Performance Indicators: Sub-activities and Work Product. This is an answer element to research question 1 -regarding using ISO 29110 for progress monitoring and performance evaluation -because evidence of performance of the sub-activities, and the presence of work products with their expected work product characteristics, provide objective evidence of the achievement of the purpose of the activities.

Performing a Basic Profile Assessment.

The ISO/IEC 15504 distinguishes between two different classes of indicators: indicators of process performance -related to the Base Practices and Work Products, and indicators of process capability -related to the management practices. BPs and WPs are the heart and the soul of a software lifecycle and the minimal maturity level of a VSE imply to perform a suitable set of BPs and WPs. Management practices relate to the process attributes grouped into capability levels 2-5. Process capability determination seem not suitable from a VSE point of view: the return on investment is too long, the recommendations are highly complex, and process improvement projects require a large investments in terms of budget, timeframe and resources.

A lot of work has been done in relation to tailoring process assessment for VSEs, mainly by reducing the number of processes assessed [START_REF] Kuvaja | TAPISTRY-A Software Process Improvement Approach Tailored for Small Enterprises[END_REF], the number of conceivable capability levels [START_REF] Pino | Assessment methodology for software process improvement in small organizations[END_REF], or the burden of the assessment task [START_REF] Habra | Initiating software process improvement in very small enterprises Experience with a light assessment tool[END_REF]. A base practice is a work performance that addresses the purpose of a particular process (an activity). Base practices are described at an abstract level, identifying "what" should be done without specifying "how". Consistently performing base practices associated with a process / activity will help the consistent achievement of its purpose. While DPs are providing a step-by-step guide for each DP, we can use it as a guide to "how" implement the activity. That is another answer element to research question 1 because it provides VSEs with a way of doing activities, motivating them to achieve activities at Capability Level 1.

4

Competency Assessment Model

Overview

This section is intended to examine research question 2 and presents some potential resolving issues. This work proposes an alternative way of assessing capability, profiled from the ISO/IEC 15504 for the capability level 1, but based on competency assessment for higher capability levels. In our opinion, frontier between the VSEas an organization -maturity and VSE employees' proficiency is thin and porous. VSE strength and weakness are closely related to its staff performance and it may be reasonable to suggest that assessing employees' proficiency will give a good indication of VSE performance so long as the competency assessment framework is closely related to VSE business and needs. Therefore, this is the proposal we put forward for answering to research question 2 and the results proposed in the rest of this paper need to be validated through several studies.

Reference Models

Models Architecture.

The European e-Competence Framework is based on a four-dimensional approach, based on competence areas (dimension 1) and competences (dimension 2). Dimension 3 provides level assignments that are appropriate to each competence. Dimension 4 provides short sample of knowledge and skills.

Dimension 1 is composed of 5 e-Competence areas that reflect the ICT Business process and its main sub-processes, from a broad perspective. Dimension 1 is mapped to 12207 Process Group, to 15504 Process Group and to 29110 Processes (because they have a very broad scope). Dimension 2 identifies and describes a set of key e-Competences for each area. We established the mapping between e-Competences and Life Cycle Processes by comparing the e-Competences titles, generic descriptions and skill examples with the Processes titles, purposes and activities and tasks (12207) or Base Practices (15504). We reduced the e-CF to the software perspective because it is the scope of the ISO/IEC 12207 standard. Dimension 4 is populated with samples of knowledge and skills related to e-Competences in dimension 2. They are provided to add value and context and are not intended to be exhaustive. Conversely, Base Practices are supporting the process and are exhaustive. Accordingly Base Practices and sub-activities cannot be mapped with skills but all these concepts form the third level of the reference models. In next sections, we will see that an exhaustive list of skills within a role is essential to competency assessment.

Activities and e-Competences.

There are different views of what the ICT profession is and no common agreement regarding a shared body of knowledge, especially for VSEs. The purpose of the ISO/IEC 29110 Basic Profile is to provide the minimal subset of ISO/IEC 12207 processes, thus we may use this to obtain a minimal subset of e-Competences for a VSE. The complete mapping between e-Competences and ISO/IEC 12207 processes provides us with a starting point upon we established a mapping between ISO/IEC 29110 activities and e-Competences. We produced the mapping between e-Competences and ISO/IEC 29110 activities by carefully comparing the e-Competences titles and generic descriptions with the activities descriptions. To clarify ambiguities, it was necessary to compare the scope of skills examples in Dimension 4 with tasks lists of activities and the corresponding DP materials. The mapping is at http://29110.univbrest.fr/en.nexus/index.php/E-C_Mapping.

4.3

Using the e-CF for ISO/IEC 29110 Rationale.

In section 2.1, we stated that process capability indicators are too far from day-today VSE concerns and we proposed to focus on job profiles. Job profiles or roles "add to job descriptions by including additional job related components such as mission, main tasks, accountability, requested deliverables, Key Performance Indicator's etc. In this context a job profile provides a comprehensive description written and formal of a job [START_REF]European ICT Professional Profiles[END_REF]". Job profiles establish the link between an organization processes and employees' competencies. Our proposition is that VSE employees should be motivated by competencies assessment and will accept the long return of investment, the high complexity and the required commitment and effort because they will be the main beneficiaries of this assessment.

Roles and Job Profiles.

Roles are defined inside ISO/IEC 29110 activities description [START_REF]SE --Lifecycle profiles for VSEs --Part 5-1-2: Management and engineering guide: Basic profile. ISO[END_REF], as function to be performed by project team members. Different roles are: PM Project Manager, TL Technical Leader, AN Analyst, DES Designer, and PR Programmer. A single person may play several roles and several persons may assume one role. Roles competencies are drafted [START_REF]SE --Lifecycle profiles for VSEs --Part 5-1-2: Management and engineering guide: Basic profile. ISO[END_REF]. Thus, it was straightforward to establish the pivotal place of roles between software activities and competences, http://29110.univbrest.fr/en.nexus/index.php/Roles_and_e-C.

As a response to the huge number of ICT profile frameworks and profile descriptions, the CEN Workshop Agreement "European ICT Profile" defines a number of representative ICT profiles covering the full ICT business. Each profile defines a mission statement, a list of required e-competences to carry the mission, a list of deliverables, a list of tasks and some Key Performance Indicators (KPI). There are four ICT profiles that correspond to the five 29110 roles. The associated e-competences with the required proficiency level are presented in Table 1.

Proficiency Level.

Proficiency can be defined as a level of being capable or proficient in a specific knowledge, skill domain expertise or competence [8] and is related to job performance. Proficiency indicates a degree of mastery that allows an individual to function independently in her/his job. In the e-CF, proficiency levels are described along three facets [8]: Autonomy ranging between "Responding to instructions" and "Making personal choices"; Context complexity ranging between "Structured-Predictable situations" and "Unpredictable-Unstructured situations"; Behavior ranging between "Ability to apply" and "Ability to conceive".

Completing the e-CF Dimension 4.

Roles competencies shall be completed with their required proficiency level. Once an e-Competence required within a role, it is possible to establish an exhaustive list of knowledge and skills. However, a detailed description of required skills is missing in the e-CF but is needed to be able to assess the proficiency level. Establishing Basic Profile roles and specializing required e-Competences knowledge and skills is an exhaustive work that will be proposed to the WG24, and may provide a new part of ISO/IEC 29110 for each profile, dedicated to roles and competencies.

Our pragmatic approach is to define e-Competences skills within a role, but a useful synthesis will be to gather all knowledge and skills related to the same e-Competence through the different Basic Profile roles, in order to have at one's disposal a centralized definition of each e-Competence related to the Basic Profile. Proficiency levels are related to job performance and as mentioned in previous section proficiency levels are described along three facets: Autonomy, Context complexity, and Behavior. Despite the detailed skills added to e-competences, the scope is still very broad and we need to go further in details to understand the proficiency level and our proposal is to add outcomes to each skill of each e-competences. Outcomes are worded in operational terms. 4) with the team proficiency level (Table 5). The correlation is working well for the SI.3 Design activity, except for team B. The correlation is not working for all teams with the SI.4 Construction activity that is not surprising because development is probably the most unpredictable activity. The correlation is working roughly for the SI.5 Integration activity, but we suspect that B.3.6 and B.3.7 form only a part of the set of skills required to perform the Integration tasks.

This case study is still encouraging; however three issues require further work. To reduce the complexity, we worked within a unique role but the association between activities and skills should work through the different Basic Profile roles. The second issue is related to the proficiency level assessment that has to be more objectively defined. The third issue is concerned with the graduation of different skills that are not of equal importance for a given activity and we should probably weight the skills with a coefficient. Resolving these issues requires us to build the complete model and to validate it through several pilot studies in VSEs.

Perspectives and Conclusion

The next major step will be to develop the approach for all ISO/IEC 29110 roles and validate each role through a series of pilot projects in VSEs. The aim of our research was to contribute to an exemplar Process Assessment Model (PAM) suitable for VSEs, related to a Process Reference Model (PRM) of the Basic Profile. The exemplar PAM expands the Basic Profile PRM by adding the definition and use of assessment indicators. We proposed to add an additional level to the ISO/IEC 29110 by dividing each activity in sub-activity playing a role similar to ISO/IEC 15504 Base Practices. These sub-activities were extracted of the different Deployment Package provided by a network of VSE support centers. Sub-activities and Work Products will be used as process performance indicators and permit a VSE to be assessed at Capability Level 1.

For higher capability levels, we proposed to replace process capability determination with competency proficiency level assessment. Proficiency indicates a degree of mastery that allows an individual to function independently in the performance of a specific knowledge application, skill domain, expertise or competence.

We proposed to add to the ISO/IEC 29110 roles definition a set of e-Competences mobilized with their required proficiency level. Then we established an exhaustive list of skills for each e-Competence and we associated a set of outcomes to each skill of each e-Competence. Self-rating is devoted to VSE employees and proficiency level determination will be performed by external assessors. We made the proposal that as main beneficiaries of competency assessment, they will accept to self-assess each outcome on a classical N-P-L-F scale, conducting to rate each skill. Through an external assessment, VSE employees will contribute to establish a proficiency level for each e-Competence that will replace process capability determination. It is assumed that it provides an indication of the VSE organizational maturity, but this has to be proven through several case studies.

Fig. 1 .

 1 Fig. 1. Structure of 15504, 12207, 29110 standards and of their relationships.

  In relation to the capstone project, the life cycle processes were extracted from ISO/IEC 29110. The schedule is roughly: one week for architectural design (including the problem understanding), one week for detailed design, two weeks of development (including end-user documentation), and one day for qualifying the software. Hence, teams are concerned with three ISO/IEC 29110 activities: Design, Construction, Integration and Tests. We assessed each team's activity capability level using the standard ISO/IEC 15504 scheme. Capability level 1 is measured with the PA 1.1 Process performance attribute. Capability level 2 is measured with the PA 2.1 Performance management attribute and the PA 2.2 Work product management attribute.

3 Process Assessment Model 3.1 A Process Reference Model for VSEs ISO/IEC 12207 and 15504.

	ISO/IEC 12207:2008 Clause 7 describes software-specific processes in terms of
	Title, Purpose, Outcomes, Activities and Tasks. ISO/IEC 15504:2004 separates pro-
	cess and capability levels in two dimensions

Table 1 .

 1 Profiles based on e-CF 3.0

	ICT Profile Title	e-Competences 3.0	Le vel
		A.4. Product / Service Planning		4
		E.2. Project and Portfolio Management		4
	Project Manager (PM)	E.3. Risk Management		4
		E.4. Relationship Management		3
		E.7 Business Change Management		3
				4
		A.5. Architecture Design		4-
	System Architect (TL)	A.7. Technology Watching B.1. Design and Development	5	4-
		B.2. System Integration	5
				4
				3
	System Analyst (AN / DES)	A.6. Application Design E.5. Process Improvement B.1. Design and Development	4	3-3-
			4
		B.1. Design and Development		3
		B.2. System Integration		2
	Developer (PR)	B.3. Testing		2
		B.5. Documentation production		3
		C.4. Problem Management		3
	4

.4 Performing a Proficiency Level Assessment Rationale.

  While proficiency assessment is performed within a role, it allows the VSE to select the adequate skills from the whole framework. For instance, if programmers do not hold the test process, B.3 Testing will be reduced to skills B.3.6 and B.3.7.

Table 4 .

 4 Teams' proficiency assessment.

Table 5 .

 5 Table 5 presents the assessment results. Teams' processes assessment.

		A	B	C	D	E	F
	SI.3 SW Architectural and Detailed Design
	PA 2.1	N	N	N	P	P	L
	PA 2.2	P	P	P	L	L	L
	PA 1.1	P	P	L	L	F	L
	SI.4 SW Construction
	PA 2.1	N	N	N	P	P	P
	PA 2.2	P	P	P	P	P	P
	PA 1.1	P	L	L	L	F	F
	SI.5 SW Integration and Tests
	PA 2.1	N	N	N	P	P	L
	PA 2.2	P	P	L	L	L	L
	PA 1.1	P	L	L	L	F	F
	We may correlate the capability level achieved by a team (Table

Competence Reference Framework.

Table 2 presents excerpts of the framework for the skills of e-Competence B.1. Design and Development. Each skill has a purpose and a set of outcomes, expressed in term of "be able to know" or "to be able to do". Each skill is described as a set of cohesive outcomes. Our rating scheme is based on the assessment of each VSE employee about her/his achievement of outcomes. We use the N-P-L-F scale of ISO/IEC 15504. When an employee states that an outcome is Largely and Fully achieved, he/she is supposed to accompany the rating by objective evidence, generally a product that he/she produced or contributed to. When all outcomes of a general goal are rated at L or F, the skill should be rated at the same rating.

Rating Proficiency Level.

When all skills of an e-competence are rated at L or F, the e-competence is considered to be achieved, but the proficiency level needs to be established. The e-CF uses a 5-point ordinal scale from e-1 to e-5 (e-5 is rarely used). Due to an alignment with European Community directives, level 2 is divided in 2 sub-levels: 2-A and 2-B.

The hypothesis is made that VSE employees will commit in a self-assessment. As mentioned in this section overview, the hypothesis is also made that assessing employees' competencies provide a correct indication of the VSE maturity as long as process and competency framework are correctly aligned. Challenges of this approach are related to provide a straightforward competency framework with a lightweight competency assessment approach and a precise and correct alignment between process models and competency framework.

A Case Study

We trialed this approach through the PR role mobilizing For each skill, each self-assessed their achievement of outcomes on the N-P-L-F scale. In order to get averages, numerical values are associated with N-P-L-F values -don't know: 0%, N: 15%, P: 50%, L: 85%, F: 100%. A skill is valued with the average of its outcomes values. We gathered values for each team, where each team's general goal value is the average of its members' values. Table 3 presents the assessment for the 6 teams and the whole set of attendees; the last line is the overall average, and represents teams' self-esteem. Team average is roughly the same, except for team B that is probably over-estimating itself. 0,22 0,59 0,15 0,15 0,24 0,24 0,28 B.3.7 Report tests 0,22 0,29 0,38 0,27 0,33 0,33 0,30 B.5.4 Documentation 0,33 0,29 0,15 0,62 0,20 0,24 0,30 Team avg. 0,31 0,49 0,32 0,34 0,32 0,36 0,36 During the training session, we collected individual observations from attendees regarding autonomy, context complexity and behavior. The autonomy of each attendee was the easiest thing to observe. Behavior observations were mostly performed while reviewing the work products issued by teams; hence it was more difficult to assign it individually. Context complexity was not relevant in this case, because all teams are developing the same software from the same requirements specification. Nevertheless, using the self-assessment, and our observations, we assessed each attendee's skill at a proficiency level 1, 2-A or 2-B. Table 4 presents this proficiency assessment with (x,y,z) where x is the number of team members at level 1; y at level 2-A and z at level 2-B.