Navigation and guidance of mobile robots towards steady or maneuvering objects (targets) is one of the most important areas of robotics that has attracted a lot of attention in recent decades. However, in most of the existing methods, both the line-of-sight angle (bearing) and the relative distance (range) are assumed to be available for navigation and guidance algorithms. There is also a relatively large body of research on navigation and guidance with bearings-only measurements. In contrast, only a few results on navigation and guidance towards an unknown target using range-only measurements have been published. Various problems of navigation, guidance, location estimation and target tracking based on range-only measurements often arise in new wireless networks related applications. Recent advances in these applications allow us to use inexpensive transponders and receivers for range-only measurements which provide information in dynamic and noisy environments without the necessity of line-of-sight. To take advantage of these sensors, algorithms must be developed for range-only navigation. The main part of this thesis is concerned with the problem of real-time navigation and guidance of Wheeled Mobile Robots (WMRs) towards an unknown stationary or moving target using range-only measurements. The range can be estimated using the signal strength and the robust extended Kalman filtering. Several similar algorithms for navigation and guidance termed Equiangular Navigation and Guidance (ENG) laws are proposed and mathematically rigorous proofs of convergence and stability of the proposed guidance laws are given. The experimental investigation into the use of range data for a WMR navigation is documented and the results and discussions on the performance of the proposed guidance strategies are presented, where a wheeled robot successfully approach a stationary or follow a maneuvering target. In order to safely navigate and reliably operate in populated environments, ENG is then modified into Augmented-ENG (AENG), which enables the robot to approach a stationary target or follow an unpredictable maneuvering object in an unknown environment, while keeping a safe distance from the target, and simultaneously preserving a safety margin from the obstacles. Furthermore, we propose and experimentally investigate a new biologically inspired method for local obstacle avoidance and give the mathematically rigorous proof of the idea. In order for the robot to avoid collision and bypass the enroute obstacles in this method, the angle between the instantaneous moving direction of the robot and a reference point on the surface of the obstacle is kept constant. The proposed idea is combined with the ENG law, which leads to a reliable and fast long-range navigation. The performance of both navigation strategy and local obstacle avoidance techniques are confirmed with computer simulations and several experiments with ActivMedia Pioneer 3-DX wheeled robots. The second part of the thesis investigates some challenging problems in the area of wheeled robot navigation. We first address the problem of bearing-only guidance of an autonomous vehicle following a moving target with smaller minimum turning radius compared to that of the follower and propose a simple and constructive navigation law. In compliance with the increasing research on decentralized control laws for groups of mobile autonomous robots, we consider the problems of decentralized navigation of network of WMRs with limited communication and decentralized stabilization of formation of WMRs. New control laws are presented and simulation results are provided to illustrate the control laws and their applications.

Navigation and guidance of mobile robots towards steady or maneuvering objects (targets) is one of the most important areas of robotics that has attracted a lot of attention in recent decades. However, in most of the existing methods, both the line-of-sight angle (bearing) and the relative distance (range) are assumed to be available for navigation and guidance algorithms. There is also a relatively large body of research on navigation and guidance with bearings-only measurements. In contrast, only a few results on navigation and guidance towards an unknown target using range-only measurements have been published. Various problems of navigation, guidance, location estimation and target tracking based on range-only measurements often arise in new wireless networks related applications. Recent advances in these applications allow us to use inexpensive transponders and receivers for range-only measurements which provide information in dynamic and noisy environments without the necessity of line-of-sight. To take advantage of these sensors, algorithms must be developed for range-only navigation. The main part of this thesis is concerned with the problem of real-time navigation and guidance of Wheeled Mobile Robots (WMRs) towards an unknown stationary or moving target using range-only measurements. The range can be estimated using the signal strength and the robust extended Kalman filtering. Several similar algorithms for navigation and guidance termed Equiangular Navigation and Guidance (ENG) laws are proposed and mathematically rigorous proofs of convergence and stability of the proposed guidance laws are given. The experimental investigation into the use of range data for a WMR navigation is documented and the results and discussions on the performance of the proposed guidance strategies are presented, where a wheeled robot successfully approach a stationary or follow a maneuvering target. In order to safely navigate and reliably operate in populated environments, ENG is then modified into Augmented-ENG (AENG), which enables the robot to approach a stationary target or follow an unpredictable maneuvering object in an unknown environment, while keeping a safe distance from the target, and simultaneously preserving a safety margin from the obstacles. Furthermore, we propose and experimentally investigate a new biologically inspired method for local obstacle avoidance and give the mathematically rigorous proof of the idea. In order for the robot to avoid collision and bypass the enroute obstacles in this method, the angle between the instantaneous moving direction of the robot and a reference point on the surface of the obstacle is kept constant. The proposed idea is combined with the ENG law, which leads to a reliable and fast long-range navigation. The performance of both navigation strategy and local obstacle avoidance techniques are confirmed with computer simulations and several experiments with ActivMedia Pioneer 3-DX wheeled robots. The second part of the thesis investigates some challenging problems in the area of wheeled robot navigation. We first address the problem of bearing-only guidance of an autonomous vehicle following a moving target with smaller minimum turning radius compared to that of the follower and propose a simple and constructive navigation law. In compliance with the increasing research on decentralized control laws for groups of mobile autonomous robots, we consider the problems of decentralized navigation of network of WMRs with limited communication and decentralized stabilization of formation of WMRs. New control laws are presented and simulation results are provided to illustrate the control laws and their applications.

Cooperative control of multi-agent systems (MASs) has been intensively investigated in the past decade. The task is always complicated for an individual agent, but can be achieved by collectively operating a group of agents in a reliable, economic and efficient way. Although a lot of efforts are being spent on improving MAS performances, much progress has yet to be developed on different aspects. This thesis aims to solve problems in the consensus control of multiple quadrotors and/or mobile robots considering irregular sampling controls, heterogeneous agent dynamics and the presence of model uncertainties and disturbances. The thesis proceeds with Chapter 1 by providing the literature review of the state-of-the-art development in the consensus control of MASs. Chapter 2 introduces experimental setups of the laboratory involving two-wheeled mobile robots (2WMRs), quadrotors, positioning systems and inter-vehicle communications. All of the developed theoretical results in Chapters 3-6 are experimentally verified on the platform. Then it is followed by two main parts: Irregular sampling consensus control methods (Chapter 3 and 4) and cooperative control of heterogeneous MASs (Chapter 5 and 6). Chapter 3 focuses on the non-uniform sampling consensus control for a group of 2WMRs, and Chapter 4 studies the event-based rendezvous control for a group of asynchronous robots with time-varying communication delays. Chapter 5 concentrates on cooperative control methods for a heterogeneous MAS consisting of quadrotors and 2WMRs. Chapter 6 focuses on the design of a quadrotor flight controller which is robust to various adverse factors such as model uncertainties and external disturbances. The developed controller is further applied to the consensus control of the heterogeneous MAS. Specifically, Chapter 3 studies synchronized and non-periodical sampling consensus control methods for a group of 2WMRs. The directed and switching communication topologies among the network are considered in the controller design. The 2WMR is an underactuated system, which implies that it can not generate independent x and y accelerations in the two-dimensional plane. The rendezvous control methods are proposed for 2WMRs. The algebraic graph theory and stochastic matrix analysis are employed to conduct the convergence analysis. Although the samplings in the work of Chapter 3 are aperiodic, one feature is that local clocks of agents are required to be synchronized. Challenges arise in the practical control of distributed MASs, especially in the scenario that the global clock is lacking. Moreover, frequent samplings can result in redundant information transmissions when the communication bandwidth is limited. To address these problems, Chapter 4 investigates an event-based rendezvous control method for a group of asynchronous MAS with time-varying communication delays. Integral-type triggering conditions for each robot are adopted to be checked periodically. If the triggering condition is satisfied at one checking instant, the agent samples and broadcasts the state to the neighbors with a bounded communication delay. Then an algorithm is provided for driving 2WMRs to asymptotically reach rendezvous. The convergence analysis is conducted through Lyapunov approaches. Most of the theoretical works on cooperative control are focused on controlling agents with identical dynamics. However, in certain realistic scenarios, some complex missions require the cooperation of different types of agent dynamics such as surveillance, search and rescue, etc. Tasks can be carried out with higher efficiency by employing both the autonomous ground vehicles and unmanned aerial vehicles. To achieve better performance for MASs, in Chapter 5, distributed cooperative control methods for a heterogeneous MAS consisting of quadrotors and 2WMRs are developed. Consensus conditions are provided, and the theoretical results are experimentally verified. Many existing quadrotor control methods need exact model parameters of the quadrotor. In reality, when a quadrotor is conducting some tasks with extra payloads or with unexpected damages to the model structure, errors in parameters could result in the failure of the flight. External disturbances also inevitably affect the flight performance. To move a step further towards practical applications, in Chapter 6, a robust quadrotor flight controller using Integral Sliding Mode Control (ISMC) technique is investigated. In experiments, an extra payload with the position and mass unknown, is attached to destroy the accuracy of the model and to add disturbances. The designed controller significantly rejects negative effects caused by the payload during the flight. This controller is also successfully applied to an MAS consisting of a quadrotor and 2WMRs. / Graduate

京都大学 / 新制・課程博士 / 博士(工学) / 甲第23884号 / 工博第4971号 / 新制||工||1776(附属図書館) / 京都大学大学院工学研究科機械理工学専攻 / (主査)教授 小森 雅晴, 教授 松野 文俊, 教授 藤本 健治 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

Yes / This paper proposes a novel trajectory tracking control approach for nonholonomic wheeled mobile robots. In this approach, the integration of feed-forward and feedback controls is presented to design the kinematic controller of wheeled mobile robots, where the control law is constructed on the basis of Lyapunov stability theory, for generating the precisely desired velocity as the input of the dynamic model of wheeled mobile robots; a proportional-integral-derivative based membrane controller is introduced to design the dynamic controller of wheeled mobile robots to make the actual velocity follow the desired velocity command. The proposed approach is defined by using an enzymatic numerical membrane system to integrate two proportional-integral-derivative controllers, where neural networks and experts’ knowledge are applied to tune parameters. Extensive experiments conducted on the simulated wheeled mobile robots show the effectiveness of this approach. / The work of XW and GZ is supported by the National Natural Science Foundation of China (61170016, 61373047). The work of MG, FI and RL was supported by a grant of the Romanian National Authority for Scientific Research, CNCS-UEFISCDI (project number: PN-II-ID-PCE-2011-3-0688).

In order to operate safely and naturally in human-centered environments, robots need to respond compliantly to force and contact interactions. While advanced robotic torsos and arms have been built that successfully achieve this, a somewhat neglected research area is the construction of compliant wheeled mobile bases. This thesis describes the mechatronics behind Trikey, a holonomic wheeled mobile base employing torque sensing at each of its three omni wheels so that it can detect and respond gracefully to force interactions. Trikey's mechanical design, kinematic and dynamic models, and control architecture are described, as well as simple experiments demonstrating compliant control. Trikey is designed to support a force-controlled humanoid upper body, and eventually, the two will be controlled together using whole-body control algorithms that utilize the external and internal dynamics of the entire system. / text

Nesta dissertação é apresentado um estudo comparativo entre seis controladores H \'infinito\' não lineares aplicados em um robô móvel com rodas. Três estratégias de controle são avaliadas. Na primeira, o modelo do robô é considerado completamente conhecido. Na segunda, o modelo matemático é considerado desconhecido e é realizada uma estimativa baseada em métodos inteligentes. E finalmente, na terceira estratégia, o modelo nominal é conhecido e técnicas inteligentes são usadas para estimar somente incertezas paramétricas do robô. As técnicas inteligentes usadas são baseadas em redes neurais e em lógica fuzzy. Esses controladores são resolvidos através de desigualdades matriciais lineares (DMLs) e equações algébricas de Riccati. Todos os resultados obtidos são baseados em dados experimentais. / This dissertation is present a comparative study between six nonlinear H \'infinity\' controllers applied to a wheeled mobile robot. Three control strategies are adopted. In the first, the model of the robot is considered completely known. In the second, the mathematical model is considered unknown and is accomplished an estimate based on intelligent methods. And finally, in the third strategy, the nominal model is known and intelligent techniques are used only to estimate parametric uncertainties of the robot. The intelligent techniques used are based in neural networks and in fuzzy logic. These controllers are solved via linear matrix inequalities (LMIs) and algebraic Riccati equations. All results obtained are based in experimental data.

Nesta dissertação é apresentado um estudo comparativo entre seis controladores H \'infinito\' não lineares aplicados em um robô móvel com rodas. Três estratégias de controle são avaliadas. Na primeira, o modelo do robô é considerado completamente conhecido. Na segunda, o modelo matemático é considerado desconhecido e é realizada uma estimativa baseada em métodos inteligentes. E finalmente, na terceira estratégia, o modelo nominal é conhecido e técnicas inteligentes são usadas para estimar somente incertezas paramétricas do robô. As técnicas inteligentes usadas são baseadas em redes neurais e em lógica fuzzy. Esses controladores são resolvidos através de desigualdades matriciais lineares (DMLs) e equações algébricas de Riccati. Todos os resultados obtidos são baseados em dados experimentais. / This dissertation is present a comparative study between six nonlinear H \'infinity\' controllers applied to a wheeled mobile robot. Three control strategies are adopted. In the first, the model of the robot is considered completely known. In the second, the mathematical model is considered unknown and is accomplished an estimate based on intelligent methods. And finally, in the third strategy, the nominal model is known and intelligent techniques are used only to estimate parametric uncertainties of the robot. The intelligent techniques used are based in neural networks and in fuzzy logic. These controllers are solved via linear matrix inequalities (LMIs) and algebraic Riccati equations. All results obtained are based in experimental data.

A wheeled mobile robot (WMR) will move on uneven terrain without slip if the length of the axle connecting two wheels can change or for a fixed length axle the wheels are allowed to tilt in a lateral direction. In this work, we consider a three-wheeled mobile robot with torus shaped wheels capable of lateral tilting. Due to the requirement of lateral tilting a two degree of freedom (DOF) suspension, one for maintaining contact with terrain and one for lateral tilting, is assumed to connect the wheels to the WMR body. Six concepts of two DOF suspension mechanisms are proposed. A WMR with these suspension mechanisms are modeled and two kinds of simulations, namely, direct kinematic analysis and inverse kinematic analysis are performed on several uneven terrains with and without suspension. Slip velocity, the path followed and the lateral tilt angle are estimated as a function of time. The force-angle stability measure is used to check the tip-over instability of the WMR on uneven terrain. It is shown that without the two DOF suspensions and with the wheels not allowed to tilt laterally, the WMR is not capable of traversing uneven terrains without large slip. When the wheels are allowed to tilt laterally with a two DOF suspension, the wheeled mobile robot slips very little. Based on least slip and less deviation from desired path, it is shown that the two best possible suspension mechanisms are the SFTA suspension and D4Bar suspension. Two prototype of three-wheeled mobile robot with these suspensions are fabricated using some components from a readily available commercial kit and with especially designed and manufactured wheels with the two degrees of freedom suspension. Simulations on an uneven terrain verify that the three-wheeled mobile robot can traverse uneven terrains with very little slip for three representative paths, namely a straight line, a circular arc and a path representing a lane change. Experiments with the two prototypes on physically constructed uneven terrain, very similar to the one used for simulation, confirm that the slip is significantly reduced with the two degree of freedom suspensions. The path of the centre of mass of the WMRs, projected on uneven surface, and the error from the desired path is presented for all the three representative paths. The simulation and experimental results clearly show that the three wheeled mobile robot with the novel two DOF suspension mechanisms can traverse uneven terrain with low slip.

This diploma thesis deals with a design and construction of a two-wheeled mobile robot. In order to prepare a high-quality project, a testing carriage has been constructed serving as a basis of useful information for the final design and construction. Beside introduction and conclusion, the diploma thesis consists of four main parts. While the first part of the thesis briefly introduces the field of robotics, the theoretical part focuses both on particular components necessary for the robot's construction as well as the Segway vehicle which served as an inspiration for the robot's functionality. After characteristics of a testing carriage, attention is devoted to individual methods of stabilization, with several different types of sensors being used. Furthermore, the chapter on mechanical design examines choice of devices and their position and provides a scheme for their construction. The electrical design follows afterwards, describing circuits that were considered optimal for the designed wiring. The forth part of the diploma thesis concentrates on the construction of a two-wheeled carriage and covers following topics: construction of mechanical components, production of electric boards, programmatic equipment of the carriage and its implementation, testing of the carriage and finally also an evaluation of achieved results.