A unified approach to the design and development of distributed control software is presented. This method is the result of a 'tight' integration between a formal method for concurrent systems (CSP) and a structured method for distributed control system (DARTS). The work presented in this thesis does not seek to extend the semantic model of CSP nor to design a specific control algorithm, rather, efforts are made to apply the existing specification and verification techniques to enhance the formality of the well established and case-proven structured counterparts that benefits are captured from both methods. As a methodology is the central aim, the suggested approach is a first step towards a complete unified software development environment, which engineers can follow from organising design ideas to system implementation with proven correctness. The thesis develops a set of parameterised CSP predicates for expressing concurrency and communication together with a corresponding set of generic processes to reflect these specified behaviours. These generic processes are formal building blocks for generating system implementations at different levels of abstraction. Utilisation of DARTS criteria and the parameterised CSP objects frame the refinement strategies. Also, mappings of generic processes to pictorial representations are suggested which enable easy assimilation of the evolving designs. Applicability of the approach is demonstrated through a high level software design of a highperformance robot control system where its suitability is shown via requirement specifications, properties verification and implementation of salient behaviours using generic building blocks. Although verification often means rigorous mathematical reasoning, the thesis presents a proof assistant the Causality Diagram Evaluation Tool to automate the manipulation of CSP processes according to the defined algebraic laws. It is shown to be of value in reasoning with designs and implementations of the robot system. It is found that the analysis facility and the graphical interpretation of communication provided by the tool allow effective analysis and manipulation of early designs. The results derived from specifying essential design details, from transforming highly abstracted implementation models, and from investigation of system behaviours through formal reasoning and simulation conclude that formal methods, in particular CSP, has a niche value in enhancing software reliability at the sub-system level as well as providing a better underpinning to the structured method DARTS. The end product is a method to generate a correct and unambiguous document of the system concerned that is amenable to a direct implementation.

This thesis presents advances in the state-of-the-art in legged locomotion through the development of bounding and galloping gaits as well as new modes of hybrid wheeled-leg modes of locomotion. Two four-legged running robots, Scout II and PAW, are examined, the latter of which is distinguished by actuated wheels at the ends of its legs. / First, hybrid modes of locomotion are demonstrated which use legs to dynamically reposition wheels at specific locations with respect to the body. These modes improve the stability and tire-wear of turning and braking manoeuvres and allow pitch-controlled slope ascent and descent in a wheeled-leg vehicle such as the PAW robot. / Second, through hip actuation, passive leg compliance and controlled wheel action it is possible to make the same vehicle run using a dynamically stable legged gait called the bound. Experimental evidence of this is presented and compared to similar experiments on the same robot with mechanically blocked wheels, a 3D simulation of the same, as well as bounding on a completely different quadrupedal robot, Scout II. While a casual observer finds no difference in blocked-wheel and active wheel control modes, detailed examination of the gaits reveals lower speeds and efficiency as well as decreased repeatability when the wheels are actively controlled. / A new method of forward speed control is presented for the bounding gait using liftoff, as opposed to touchdown, leg angles. The liftoff angle method of speed control is shown to be particularly suited to fine-tuning of certain gait performance indices. / Third, the underactuated bounding gait is extended to demonstrate, for the first time, that robotic galloping is possible and that it can be achieved in two underactuated quad-rupedal robots and with varying levels of decoupled control. In the Scout II robot the front leg pair and rear leg pairs function independently; while in the PAW robot galloping is achieved with no controlled coupling between any of the four legs. The rotary gallop gait demonstrated by both robots is characterized by a significant yaw component and is compared to another bound-derived turning gait which uses liftoff angles to produce yaw. In particular, the correspondence of lead leg to yaw direction in both cases is found to match results from biology. In contrast, while it is thought that animals pivot about their lead leg to turn, the rotary gallop demonstrated by these robots shows that yaw occurs primarily in the leg behind the lead leg.

The first part of this thesis documents experimental investigation into the use of vision for wheeled robot navigation problems. Specifically, using a video camera as a source of feedback to control a wheeled robot toward a static and a moving object in an environment in real-time. The wheeled robot control algorithms are dependent on information from a vision system and an estimator. The vision system design consists of a pan video camera and a visual gaze algorithm which attempts to search and continuously maintain an object of interest within limited camera field of view. Several vision-based algorithms are presented to recognize simple objects of interest in an environment and to calculate relevant parameters required by the control algorithms. An estimator is designed for state estimation of the motion of an object using visual measurements. The estimator uses noisy measurements of relative bearing to an object and object's size on an image plane formed by perspective projection. These measurements can be obtained from the vision system. A set of algorithms have been designed and experimentally investigated using a pan video camera and two wheeled robots in real-time in a laboratory setting. Experimental results and discussion are presented on the performance of the vision-based control algorithms where a wheeled robot successfully approached an object in various motions. The second part of this thesis investigates the coordination problem of flocking in multi-robot system using concepts from graph theory. New control laws are presented for flocking motion of groups of mobile robots based on several leaders. Simulation results are provided to illustrate the control laws and its applications.

Thesis (M. S.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Howard, Ayanna; Committee Member: Egerstedt, Magnus; Committee Member: Vela, Patricio. Part of the SMARTech Electronic Thesis and Dissertation Collection.

Adaptive control of a nonlinear time varying (NTV) plant, such as a robotic manipulator, is intended to tolerate the unmodeled disturbances and the uncertain parameters of the dynamic model. Most of the previous research has been focused on NTV plants with bounded and "slowly-varying" plant terms. Almost all adaptive controllers require persistent excitations to guarantee stable tracking in the presence of unmodeled disturbances. The new adaptive controllers developed in this work provide stable and robust performance without persistent excitations and the "slowly-varying" assumption. Moreover, the uncertainties of a NTV plant model are not required to be bounded. This allows one to treat some potentially unbounded dynamics as disturbances. Stability and robustness analysis of adaptive controllers under the relaxed conditions is an essential part of this study. A major problem arising in robotic control is parameter uncertainty. The linear parameterization approach is also implemented in this work to deal with the parameter uncertainty. An innovative algorithm for determining the manipulator "regressor" (a coefficient matrix in parameter-linearized form of robot dynamics) is developed. Based on this algorithm a robust self-tuning controller is designed. The control law is proved to be robust with respect to parameter errors and disturbances. The robustness of the controller relaxes the requirement for the parameter estimator, and leads to a stable system without persistent excitations. / Graduate

Orientador: João Maurício Rosário / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica / Made available in DSpace on 2018-08-16T10:12:15Z (GMT). No. of bitstreams: 1 Moretti_Mariana_M.pdf: 12180551 bytes, checksum: 7061efe63e86e5ba1b21c21253c1ee35 (MD5) Previous issue date: 2010 / Resumo: Uma nova proposta de modelo dinâmico da Plataforma de Stewart é apresentada neste trabalho. Enquanto a cinemática inversa é usada para posicionar cada um dos seis braços do robô, o vetor de força que atua em seus deslocamentos é dado pelo torque de motores elétricos. A inércia em cada um dos pontos de apoio é aproximada por uma rigidez mecânica associada ao modulo de Young. Ainda, foi implementado um modelo dinâmico que usa a aproximação de Newton-Euler, amplamente aplicada na dinâmica inversa de robôs seriais, para o caso deste robô paralelo. Em ambas as abordagens, as equações foram implementadas em Matlab/SimulinkTM, e os resultados das simulações foram apresentados para validação das aproximações / Abstract: A new proposal for a dynamic model of the Stewart platform is presented. While the inverse kinematics is used to position each of the six arms of the robot, the vector of force acting on the displacement is given by the torque of electric motors. The inertia in each of the support points is approximated by a mechanical stiffness associated with the Young modulus. Still, it was implemented a dynamic model that uses the Newton-Euler approach, widely applied in the inverse dynamics of serial robots, for the case of this parallel robot. In both approaches, the equations were implemented in Matlab/SimulinkTM, and the simulation results were presented for validation of the approaches / Mestrado / Mecanica dos Sólidos e Projeto Mecanico / Mestre em Engenharia Mecânica

M.Ing. / Parts feeding devices or feeders are used in automated assembly systems to deliver correctly oriented parts to the assembly station workhead. These devices play an important operational role since feeding is one of the major operations involved in an automated assembly process. However they account for much of the cost of an automated assembly system because most of the engineering time spent to develop such a system is used to devise a means of feeding the components in the correct orientation for the assembly process. This thesis describes the implementation of an integrated and computer controlled feeding and transfer system. The system consists of a vibratory bowl feeder for selecting, orienting and feeding parts and a flat conveyor belt for transferring parts to a prescribed location. The work focusses mainly on the design and analysis of the bowl feeder, on the mechanical and information interfacing aspects of the integration problem and on the control of the system. Sensing and electronic control circuits were also built to complete the system. The system implemented is to be integrated at a later stage with an industrial robot for handling purposes. Therefore, some issues related to the handling of parts from the conveyor belt by the robot are also discussed. Experimental results show that the recommendable operating frequency for the vibratory feeder is close to the value predicted by theoretical analysis. Several concurrent activities with critical time constraints and different periods were involved in the system, making the control more difficult due to the limited control capabilities of Visual basic, an easy to learn programming language used to implement the control program and the relatively slow speed of the computer used Nevertheless, it was observed that for feed rates close to 3 parts/min, the program developed performs well regarding the random control of the flow rate of parts on the conveyor, parts position and speed profiles obtained compare satisfactorily with the corresponding theoretical profiles. Recommendations for the integration of the robot to the system are made.

No description available.

This dissertation is concerned with a space robot consisting of a rigid platform, two articulated flexible arms and a rigid end-effector. The task is to ferry some payload and to dock smoothly with an orbiting target whose motion is either known or not known a priori. The dynamical equations for planar motion of the space robot are derived by means of Lagrange’s equations. They are then separated into two sets of equations suitable for rigid-body maneuver control design and vibration suppression control design. A perturbation method is used when the target motion is known a priori and direct partitioning is used when the target motion is not known. Both approaches are under the assumption that maneuver motions are much larger than elastic motions. As far as the rigid-body maneuver control is concerned, optimal trajectory planning is carried out off-line by means of the global optimization method under the assumption that the target motion is known a priori. In contrast, when the target motion is not known a priori, on-line feedback tracking control is carried out by means of an algorithm based on Liapunov-like methodology and using on-line measurements of the target motion. As far as the vibration suppression control is concerned, the use of the piezoelectric sensor/actuator pairs dispersed along the flexible arms is proposed. Collocated sensors/actuators for vibration control exhibit good performance. The actuators are designed to compensate for the disturbances caused by the rigid-body maneuver and to realize the LQR feedback control. Assuming that the number of actuators along each flexible arm is equal to the number of modes used to model the beam, the LQR control design is based on a linear time-varying system without persistent disturbances. Problems related to the digital implementation of the control algorithms are also discussed. Some undesirable effects, such as the bursting phenomenon and even system instability, can occur if the control algorithms are realized in discrete-time. To prevent these problems, the modified discrete-time control schemes are developed. Numerical examples are used to demonstrate the control algorithms. / Ph. D.

A distributed paradigm is proposed for behavior-based control of a homogeneous collection of autonomous mobile robots in the lifting and lowering processes of payload transportation. Unlike previous applications of behavior-based control to payload transportation, we examine control of a payload in a vertical plane. Others before have examined moving payloads on a horizontal surface through pushing actions; we demonstrate an ability to both raise and lower a pallet, despite the fact that no robots have a rigid grasp of the pallet. This control paradigm uses parallel behavior pathways within the individual robot and minimal emergent specialization between robots to control both pallet translation and rotation, while maintaining a strong tolerance to environmental uncertainties and changes. We stress simple, feasible methodologies over complex, optimal methodologies, although we show that with some global self-organization of the collective, the feasible solutions approach and become optimal solutions. These mobile robots demonstrate an ability to function in unforeseen environments and with inaccurate sensor data. They also demonstrate an ability to learn their place, or role, within the collective. The robots must learn their relative roles because they possess no predetermined knowledge about pallet mass, pallet inertia, collective size, or their positions relative to the pallet's center of gravity. All of this is achieved using memoryless, behavior-based control algorithms with minimal inter-agent communication. / Master of Science