Un groupe de robots collaboratifs peut gérer des tâches qui sont difficiles, voire impossibles, à accomplir par un seul. On appelle un ensemble de robots coopérant un système multi-agents (SMA). L'interaction entre agents est un facteur clé dans la commande coopérative qui pose d'importants défis théoriques et pratiques. L'une des tâches du contrôle coopératif est le consensus dont l'objectif est de concevoir des protocoles de commande afin de parvenir à un accord entre leurs états respectifs. Cette thèse améliore la navigation pour les SMA, tout en tenant compte de certaines contraintes pratiques (modèle du robot et contraintes temporelles) dans la conception de contrôleurs coopératifs pour chaque agent, de manière décentralisée. Dans cette thèse, deux directions sont étudiées. D'une part, le taux de convergence est une spécification de performance importante pour la conception du contrôleur pour un système dynamique. La convergence rapide est toujours recherchée pour améliorer les performances et la robustesse. La plupart des algorithmes de consensus existants se concentrent sur la convergence asymptotique, où le temps d'établissement est infini. Cependant, de nombreuses applications nécessitent une convergence rapide généralement caractérisée par une stratégie de commande à temps fini. De plus, la commande à temps fini autorise certaines propriétés intéressantes, mais le temps de stabilisation dépend des conditions initiales des agents. L'objectif ici est de concevoir un protocole de consensus leader-follower à temps fixe pour les SMA décrits en temps continu. Ce problème est étudié en utilisant la théorie de la stabilisation à temps fixe, qui garantit que le temps de stabilisation est borné quelles que soient les conditions initiales. Les contrôleurs et les observateurs à modes glissants sont conçus pour que chaque agent résolve le problème du consensus à temps fixe lorsque le leader est dynamique. D'autre part, par rapport aux systèmes à temps continu, le problème du consensus dans un cadre à temps discret convient mieux aux applications pratiques en raison de la limitation des ressources de calcul pour chaque agent. Le modèle de commande prédictive (MPC) permet de gérer les contraintes de commande et d'état des systèmes. Dans cette thèse, cette méthode est appliquée pour traiter le problème du consensus en temps discret en laissant chaque agent résoudre, à chaque étape, un problème de commande optimale contraint impliquant uniquement l'état des agents voisins. Les performances de suivi sont également améliorées dans cette thèse en ajoutant de nouveaux termes à partir du MPC classique. Les contrôleurs proposés sont simulés et implémentés sur un groupe composé de plusieurs robots réels en utilisant ROS (Robotic Operating System). Dans cette thèse, quelques solutions correspondant au problème de la connexion entre plusieurs robots mobiles de manière décentralisée, du réglage des périodes d'échantillonnage et des paramètres de contrôle sont également abordées. / Nowadays, robots have become increasingly important to investigate hazardous and dangerous environments. A group of collaborating robots can often deal with tasks that are difficult, or even impossible, to be accomplished by a single robot. Multiple robots working in a cooperative manner is called as a Multi-Agent System (MAS). The interaction between agents to achieve a global task is a key in cooperative control. Cooperative control of MASs poses significant theoretical and practical challenges. One of the fundamental topics in cooperative control is the consensus where the objective is to design control protocols between agents to achieve a state agreement. This thesis improves the navigation scheme for MASs, while taking into account some practical constraints (robot model and temporal constraints) in the design of cooperative controllers for each agent, in a fully decentralized way. In this thesis, two directions are investigated. On one hand, the convergence rate is an important performance specification to design the controller for a dynamical system. As an important performance measure for the coordination control of MASs, fast convergence is always pursued to achieve better performance and robustness. Most of the existing consensus algorithms focus on asymptotic convergence, where the settling time is infinite. However, many applications require a high speed convergence generally characterized by a finite-time control strategy. Moreover, finite-time control allows some advantageous properties but the settling time depend on the initial states of agents. The objective here is to design a fixed-time leader-follower consensus protocol for MASs described in continuous-time. This problem is studied using the powerful theory of fixed-time stabilization, which guarantee that the settling time is upper bounded regardless to the initial conditions. Sliding mode controllers and sliding mode observers are designed for each agent to solve the fixed-time consensus tracking problem when the leader is dynamic. On the other hand, compared with continuous-time systems, consensus problem in a discrete-time framework is more suitable for practical applications due to the limitation of computational resources for each agent. Model Predictive Control (MPC) has the ability to handle control and state constraints for discrete-time systems. In this thesis, this method is applied to deal with the consensus problem in discrete-time by letting each agent to solve, at each step, a constrained optimal control problem involving only the state of neighboring agents. The tracking performances are also improved in this thesis by adding new terms in the classical MPC technique. The proposed controllers will be simulated and implemented on a team of multiple Mini-Lab Enova Robots using ROS (Robotic Operating System) which is an operating system for mobile robots. ROS provides not only standard operating system services but also high-level functionalities. In this thesis, some solutions corresponding to problem of connection between multiple mobile robots in a decentralized way for a wireless robotic network, of tuning of the sampling periods and control parameters are also discussed.

No description available.

Text in English with abstracts in English, Afrikaans and Venda / In this qualitative study, the research objective was to present a theoretical framework for the phenomenon of interpersonal leadership relations (denoting both the dyadic relationship between two leader/followers and the leadership communication taking place in the dyad) in knowledge-based organisational contexts. It is posited that the interpersonal leader-follower dyad (LFD) may be viewed from a systems theory perspective as a system consisting of two system parts (individuals). These individuals are labelled ‘leader/followers’ to emphasise their mutual interdependence, and to indicate that these roles may be interchangeable, based on the knowledge needs in a particular situation (in line with the tenets of shared leadership). The dyadic system is influenced by its environment, the organisational context. However, the primary focus of this study is on interpersonal leadership communication as symbolic interaction between the leader/followers in the LFD. These three systemic levels are represented as major themes in the model resulting from this study: Theme 1 – an organisational environment that supports constructive interpersonal leadership relations (ILR); Theme 2 – symbolic interaction in the LFD; and Theme 3 – personal attributes that enhance ILR. The data were collected from two convenience samples. In-depth, semi-structured interviews were conducted with participants in Sample 1, while questionnaires were used to collect data from Sample 2. In both cases, thematic analysis was used to analyse and interpret the data. The major contribution of the study is the resulting theoretical framework of ILR, which comprises a theoretically based definition of ILR; a generic model of ILR; and current guidelines for fostering constructive ILR in knowledge-based contexts, with reference to the three systemic levels. The following definition was phrased based on the study: Constructive interpersonal leadership relations (ILR) in a knowledge-based organisational context is a dyadic process of symbolic communication between two expert leader/followers who mutually influence each other and share meaning to strengthen their relationship and to collaboratively transfer and apply knowledge to achieve organisational goals. In terms of the environment, it was found that organisational leaders should actively model and promote the following: a collaborative leadership concept, workplace spirituality, cultural inclusivity, and adaptation to advancing communication technologies. Regarding symbolic interaction in the LFD, the following communication practices were found to be central to constructive ILR: active listening, supporting followers as unique individuals, respectful communication, considering followers’ input, facilitating constructive redefinition of the other leader/follower’s self, role-taking (taking the perspective of the other leader/follower’s role), awareness of attribution, conflict management through non-threatening, respectful and preferably face-to-face discussion, facilitating a sense of meaning or purpose at work for the other leader/follower, and fostering constructive relationship properties such as trust. It was found that ILR may produce system outputs into the organisation that contribute to the organisational culture and climate, job performance, employee morale and engagement, and staff retention. Personal attributes were organised into personal values and competencies that support ILR. The most important personal values were identified as honesty, love or supportiveness, respect, relationships or engagement, trust, and professional excellence. Essential competencies were identified as listening skills, emotional communication competencies (particularly self-awareness, self-reflection and attending to others’ emotions), engagement skills, conflict management skills, and multicultural competency (including generational skills). / In hierdie kwalitatiewe studie word ’n teoretiese raamwerk voorgelê vir die verskynsel ‘interpersoonlike leierskapsverhoudings‘ (verwysende na beide die diadiese verhouding tussen twee leier/volgelinge en die leierskapskommunikasie wat in die diade plaasvind) in kennisgebaseerde organisatoriese kontekste. Die uitgangspunt is dat die interpersoonlike leier-volgeling-diade (LVD) vanuit ‘n sisteemteoretiese perspektief beskou kan word as ‘n sisteem wat uit twee sisteemdele (individue) bestaan. Hierdie individue word ‘leier/volgelinge‘ genoem om hulle wedersydse interafhanklikheid te beklemtoon; en om aan te toon dat hierdie rolle uitruilbaar mag wees, afhangende van die kennisbehoeftes in ’n gegewe situasie (met verwysing na die teorie van gedeelde leierskap). As ’n sisteem word die LVD ook deur die omringende omgewing of organisatoriese konteks beïnvloed. Die primêre fokus van hierdie studie is egter op interpersoonlike leierskapskommunikasie as simboliese interaksie tussen die leier/volgelinge in die LVD. Hierdie drie sistemiese vlakke word in hierdie studie deur die hooftemas in die studie verteenwoordig en ook as sulks in die voortvloeiende model uitgebeeld: Tema 1 – ’n organisatoriese omgewing wat konstruktiewe interpersoonlike leierskapsverhoudings (ILV) ondersteun; Tema 2 – simboliese interaksie in die LVD; en Tema 3 – persoonlike eienskappe wat ILV bevorder. Die teoretiese raamwerk van ILV bestaan uit die volgende: ’n teoreties gefundeerde definisie van ILV; ’n generiese model van ILV; en ’n raamwerk van huidige riglyne vir die kweek van konstruktiewe ILV in kennisgebaseerde kontekste, met verwysing na die drie sistemiese vlakke van omgewing, diade en individuele leier/volgelinge. Die volgende definisie is op grond van die navorsingsresultate geformuleer: Konstruktiewe interpersoonlike leierskapsverhoudings (ILV) in ’n kennisgebaseerde organisatoriese konteks is ’n diadiese proses van simboliese kommunikasie tussen twee kundige leier/volgelinge wat mekaar wedersyds beïnvloed en betekenis deel om hulle verhouding te versterk en kennis samewerkend oor te dra en aan te wend om organisatoriese doelwitte te bereik. In terme van die organisatoriese omgewing is bevind dat organisatoriese leiers, veral senior leiers, die volgende aktief moet modelleer en bevorder in die organisasie: ’n samewerkende leierskapskonsep, spiritualiteit in die werkplek, kulturele insluiting, en aanpassing by vooruitgang in kommunikasietegnologie. Met verwysing na simboliese interaksie in die LVD is die volgende praktyke bevind as sentraal tot konstruktiewe ILV: aktiewe luistergedrag, die ondersteuning van volgelinge as unieke individue, respekvolle kommunikasie, die inagneming van volgelinge se insette, die fasilitering van die konstruktiewe herdefiniëring van die ander leier/volgeling se self, rol-inneming (die inneem van die rolperspektief van die ander leier/volgeling), bewustheid van attribusie, die bestuur van konflik deur nie-bedreigende, respekvolle en – waar moontlik – aangesig-tot-aangesig bespreking, die fasilitering van ’n sin van doel of betekenis by die werk vir die ander leier/volgeling, en die kweek van konstruktiewe verhoudingseienskappe (vertroue, uitruilbare leier/volgeling-rolle en wedersydse invloed is geïdentifiseer as belangrik). Dit is ook bevind dat ILV sisteemuitsette in die organisasie mag genereer wat bydra tot die organisatoriese kultuur en klimaat, werkprestasie, werknemers se moreel en betrokkenheid, en personeelbehoud. Persoonlike eienskappe is verdeel in waardes en vaardighede wat ILV ondersteun. Die belangrikste waardes is geïdentifiseer as eerlikheid, liefde, respek, verhoudings, vertroue, en professionele uitnemendheid. Die volgende vaardighede is geïdentifiseer as noodsaaklik: luistervaardighede, emosionele kommunikasievaardighede (met spesifieke verwysing na selfbewussyn, selfrefleksie en aandag aan ander se emosies), betrekkingsvaardighede, konflikbestuursvaardighede, en multi-kulturele vaardighede (wat generasievaardighede insluit). Die date is ingesamel uit twee gerieflikheidsteekproewe. Indiepte-, semi-gestruktureerde onderhoude is gevoer met Steekproef 1 (kundiges op gebiede verwant aan ILV in kennisgebaseerde kontekste), terwyl vraelyste gebruik is om data te verkry by Steekproef 2 (leier/volgelinge in kennisgebaseerde kontekste). Tematiese ontleding is in beide gevalle gebruik om die data te ontleed en te interpreteer. / Kha iyi ngudo ya u tandula ‘qualitative’, ndivho ya ṱhoḓisio yo vha u ṋetshedza mutheo wa thiyori kha sia ḽa vhushaka ha vhurangaphanḓa vhukati ha vhathu (zwine zwa amba vhushaka ha tshumisano vhukati ha vharangaphanḓa/vhatevheli vhavhili na vhudavhidzani kha vhurangaphanḓa vhune ha khou bvelela nga kha tshumisano yeneyo) kha nyimele ya tshiimiswa yo ḓitikaho nga nḓivho. Zwo sumbedziswa uri tshumisano ya murangaphanḓa-mutevheli vhukati ha vhathu (leader-follower dyad (LFD)) i nga lavheleswa u bva kha sia ḽa sisiṱeme ya thyori sa sisiṱeme ine ya vha na zwipiḓa zwivhili (vhathu). Vhathu avha vha vhidzwa ‘vharangaphanḓa/vhatevheli’ hu u itela u khwaṱhisedza u ḓitika havho nga muṅwe, na u sumbedza uri mishumo iyi i nga imelelana, zwo ḓitika nga ṱhoḓea dza nyimele yeneyo. (zwi tshi tevhedza vhatevheli vha vhurangaphanḓa uvho). Sisiṱeme ya tshumisano i ṱuṱuwedzwa nga nyimele yayo, nyimele ya tshiimiswa. Fhedziha zwa ndeme kha ngudo iyi ndi nga vhudavhidzani ha vhurangaphanḓa vhukati ha vhathu sa tshiga tsha tshumisano vhukati ha vharangaphanḓa/vhatevheli kha LFD. Maga aya mararu a sisisṱeme a imelelwa nga ṱhoho khulwane kha nḓila yo livhisaho kha ngudo iyi: Ṱhoho 1 – mupo/nyimele ya tshiimiswa i ṱuṱuwedzaho vhushaka ha vhurangaphanḓa vhu vhuedzaho vhukati ha vhathu (interpersonal leadership relations (ILR)); Ṱhoho 2 – Tshiga tsha tshumisano kha LFD; na Ṱhoho 3 – Vhuvha ha muthu vhune ha konisa ILR. Data yo kuvhanganywa u bva kha sambula dzine dza vha dza tsinisa. Mbudziso dzo ṱanḓavhuwaho, dzi sa langiho kufhindulele kha vhavhudziswa dzo itwa hu na vhadzheneli kha Sambula ya u thoma (1), ngeno khwesheya dzo shumiswa u kuvhanganya data kha Sambula 2. Kha nyimele dzoṱhe ho shumiswa ṱhaṱhuvho i re na vhushaka na ṱhoho u itela u ṱhaṱhuvha na u ṱalutshedza data. Zwine ngudo iyi ya vhuedza khazwo ndi mvelelo ya mutheo wa thyori wa ILR, ine ya vha na ṱhalutshedzo yo ḓitikaho nga thyori ya ILR, nḓila ya u angaredza ya ILR; na tsumbanḓila dza zwino u itela mbuelo ya ILR kha nyimele yo ḓitikaho nga nḓivho, zwo lavhelesa kha maga a sisiṱeme. Ṱhalutshedzo i tevhelaho yo vhekanywa zwi ḓitika nga ngudo: Vhushaka ha vhurangaphanḓa Vhuvhedzaho vhukati ha vhathu (ILR) kha nyimele ya tshiimiswa yo ḓitikaho nga nḓivho ndi maitele a tshumisano ya tshiga tsha vhudavhidzani vhukati ha vharangaphanḓa/vhatevheli vha re na nḓivho vhane vha ṱuṱuwedzana na u kovhekana zwine zwa amba u itela u khwaṱhisa vhushaka havho khathihi na u fhirisa na u shumisa nḓivho u itela u zwikelela zwipikwa zwa tshiimiswa. Zwi tshi ya nga nyimele, zwo wanala uri vharangaphanḓa vha tshiimiswa vha tea u vhumba na u ṱuṱuwedza zwi tevhelaho: muhumbulo wa tshumisano kha vhurangaphanḓa, zwa tshimuya mushumoni, u katela zwa mvelele, na u ṱanganedza u shumiswa ha thekhinoḽodzhi ya vhudavhidzani. Maelana na tshumisano nga tshiga kha LFD, maitele a vhudavhidzani a tevhelaho a wanala a one a ndeme kha ILR ire na mbuelo: u thetshelesa nga vhuronwane, u tikedza vhatevheli hu na kupfesesele kwa uri vhathu vho fhambana, vhudavhidzani ha ṱhonifho, u dzhiela nṱha mihumbulo ya vhatevheli, u ṱuṱuwedza u ṱhalutshedza nga nḓila yo fhambanaho i vhuedzaho ya vhaṅwe vharangaphanḓa/vhatevheli vha shumaho u ya nga vhone vhaṋe, u dzhia dzhenelela (u vhona nga nḓila ine vhaṅwe vharangaphanḓa/vhatevheli vha vona ngayo), u tangnedza nḓivho, ndaulo ya phambano nga kha nyambedzano i sa shushedziho, ya ṱhonifho, nga maanḓa nga nyambedzano vhathu vho livhana zwifhaṱuwo, u ṱuṱuwedza nḓivho ya ṱhalutshedzo kana ndivho ya mushumo kha vhaṅwe vharangaphanḓa/vhatevheli, u ṱuṱuwedza zwithu zwi fhaṱaho vhushaka vhu vhuedzaho u fana na u fulufhedzana. Zwo tumbulwa uri ILR i bveledza sisiṱeme ya mvelelo u vha tshiimiswa tshine tsha dzhenelela kha mvelele na vhuḓipfi, kushumele kwa mushumo, u ṱuṱuwedzea na u dzhenelela ha vhashumi, nauri vhashumi vha sa ṱuwe. U ṱanganedzea ha muthu zwo vheekanywa zwi tshi ya nga mikhwa ya muthu ene muṋe na vhukoni zwine zwa tikedza ILR. Mikhwa ya muthu ya ndemesa yo topolwa sa u fulufhedzea, lufuno, ṱhonifho kana u dzhenelela, fulufhelo, na vhukoni kha zwa phurofeshinaḽa. Vhukoni ha ndeme ho sumbedzwa sa vhukoni ha u thetshelesa, vhukoni ha vhudavhidzani ha muhumbulo (nga maanḓa u ḓiḓivha, u ḓilingulula/sedzulusa na u dzhiela nzhele vhuḓipfi ha vhaṅwe vhathu), vhukoni ha u dzhenelela, vhukoni ha ndaulo ya phambano, na vhukoni ha u dzhenelela kha mvelele nnzhi (zwi tshi katela vhukoni ha zwa murafho). / Communication Science / D. Litt. et Phil. (Communication)