This dissertation is concerned with the position and vibration control of flexible articulated space robots consisting of a rigid platform, two flexible arms, and a rigid end-effector carrying a payload, all components being serially connected through revolute joints. The mission is to carry a payload over a prescribed trajectory in the inertial space, while suppressing the elastic vibration of the arms and the rigid-body perturbations. The equations of motion governing the robot dynamics are derived by means of Lagrangian mechanics and they include actuator dynamics. Based on the assumption that the elastic deformations and the rigid-body perturbations are small relative to the nominal trajectory-following rigid-body motions, a perturbation approach is adopted to separate the equations into nonlinear rigid-body equations and linear perturbation equations. The nominal trajectory is planned to conserve the limited actuator resources and keep the platform attitude stationary, by eliminating the inherent kinematic redundancy of the manipulator. By assuming perfect sensing, i.e., all the states are completely accessible, two kinds of controls are designed in discrete-time. First, a feedforward control is designed to minimize the persistent disturbance resulting from the nominal motions. Next, a feedback control is synthesized based on the Linear Quadratic Regulator (LQR) theory with a prescribed degree of stability to make the system stable and further enhance the disturbance-rejection performances. These controls are subsequently applied to the case in which only the sensor outputs are available, and they are noisy. A finite number of sensors is assumed. A Kalman filter is designed to estimate the state on the assumption of zeromean Gaussian white plant and measurement noise. In the real situation, controls are applied to the original plant rather than the linearized model, so that the Linear Quadratic Gaussian (LQG) control combined with robustness recovery methods is tested on the plant. Due to difficulties in implementing a Kalman filter, a Maximum Likelihood Estimator (MLE) is proposed. A numerical example illustrates the approach. / Ph. D.

A novel material transport system is presented that uses 'swarms' of small autonomous mobile robots to collectively lift and move palletized loads. The robots are relatively unsophisticated in design and have no advanced sensory or communications capability. There is no central or supervisory controller directing the robots. Each robot must be able react to its environment autonomously, yet cooperate within a team of similarly designed robots. Reactive and behavior-based principles are the basis of the system design. Although the entire material transport scenario is presented in this thesis in the context of a reactive behavior-based control architecture, emphasis is placed on developing a single behavior that allows the robots to move a loaded pallet once it has been lifted by a team of robots. Toward this goal, a centralized control scheme is derived that directs the actions of the robots while underneath a loaded pallet. It is shown that this approach produces an 'optimal' distribution of work among the robots. Alternatively, a distributed control scheme is derived that allows each robot to autonomously assist in moving a palletized load. This approach assumes a team of robots is capable of electing a leader and uses the dynamics of a caster as the basis for the development of a control law. Both the central and distributed control schemes are verified via computer simulation. / Master of Science

The focus of this work is the real-time prediction and compensation of static deflections in robotic manipulator arms. A general manipulator deflection model is developed based on static beam theory and robot kinematics. An optimization technique is proposed to determine the stiffness of the manipulator components using end-effector deflection measurements. Strategies for incorporating this modeling approach into a manipulator controller are also presented along with the results of a successful application of this research. This work is an extension of previous manipulator deflection research. Multiple pairs of torsional stiffness elements and beam elements are used to model complex link and joint geometries whereas previous models only used a single beam per manipulator link. In addition, the modeling algorithms and stiffness characterization methods are general and may be applied directly to any serial manipulator. Also, the optimization techniques used to characterize a manipulator's stiffness provide a more accurate and flexible approach than previous analytical methods. The deflection model was successfully tested using a nuclear steam generator service manipulator. Since this manipulator is considerably more flexible than common industrial robots, it serves as a near worst-case test for deflection modeling. The end effector was found to deflect as much as 1.5 inches due to the weight of the links and joints. The deflection model was able to compensate for 94% of the end-effector deflection, allowing the manipulator to perform tasks requiring a positioning accuracy of 0.09 inches. The algorithms for flexible forward and inverse kinematics as well as trajectory generation were incorporated directly into the manipulator controller code. These modules were capable of running in real-time with little computational expense. / Master of Science

Modifications were made to the control model for torque generation in the Air Force Articulated Total Body (ATS) simulation computer program. Limb motion stability was improved by introducing integral control in the existing feedback control equation. Motion studies were performed using a Merlin robot model to determine control equation gains for single and multi-joint rotations up to 180 degrees. The robotic motion was made to resemble coordinated angular motion profiles that had previously been determined for similar human arm motion. The control equation gains for the six joints examined were added to the input description as a tabular set of data, which the program could access depending on the joint target angles prescribed by the user. Simultaneous multi-joint rotations were also studied using the same controlling values as were used for single joint rotations. These numbers produced accurate results for all joint rotations, as long as either the shoulder or elbow joints were held at their initial angular positions. The errors produced when the target angles for both the shoulder and elbow were non-zero were less than two degrees of arc. / Master of Science

Orientador: José Geraldo Trani Brandão / Banca: Francisco José Grandinetti / Banca: Anselmo Monteiro Ilkiu / Resumo: O estudo de um modelo matemático completo, incluindo os servos atuadores, a dinâmica do corpo rígido e o planejamento e geração de trajetórias do manipulador robótico cilíndrico, é um indispensável ponto de partida para aplicações de simulação das juntas e controle de movimentos. As equações cinemáticas obtidas pelas técnicas da Matriz de Transformação Homogênea e Matriz de Transformação Inversa são a solução para a geração de trajetórias, as quais podem ser feitas no espaço cartesiano ou no espaço das juntas e também possibilitam gerar o volume de trabalho do manipulador, que é de grande interesse para a especificação de determinada configuração em aplicações ou tarefas específicas. As equações de movimento foram derivadas usando a formulação Lagrangiana para predizer o comportamento do manipulador quanto à influência da geometria e os parâmetros de massa do manipulador. / Abstract: The study of a complete mathematical model including the servos actuators, the dynamics of the body rigid and the planning and generation of the manipulator's cylindrical robotic trajectories is an indispensable starting point for applications of simulation of the joints and control of movements. The Kinematic equations obtained by the techniques Homogeneous Transformation Matrix and Inverse Transformation Matrix make is the solution for generation of trajectories that can be done in the cartesian space or in the space of the joints and they also make possible to generate the volume of the manipulator's work that is of great interest for specification certain configuration in applications or specific tasks. The movement equations were derived using the formulation Lagrangiana to predict the manipulator's behavior as for the influence of the geometry and the parameters of the manipulator's mass. / Mestre

The capacity of humankind to mimic fish-like locomotion for engineering applications depends mainly on the availability of suitable actuators. Researchers have recently focused on developing robotic fish using smart materials, particularly Ionic Polymer-Metal Composites (IPMCs), as a compliant, noise-free, and scalable alternative to conventional motor-based propulsion systems. In this thesis, we investigate fish-like self propulsion using flexible bimorphs made of Macro-Fiber Composite (MFC) piezoelectric laminates. Similar to IPMCs, MFCs also exhibit high efficiency in size, energy consumption, and noise reduction. In addition, MFCs offer large dynamic forces in bending actuation, strong electromechanical coupling as well as both low-frequency and high-frequency performance capabilities. The experimental component of the presented work focuses on the characterization of an MFC bimorph propulsor for thrust generation in a quiescent fluid as well as the development of a preliminary robotic fish prototype incorporating a microcontroller and a printed-circuit-board (PCB) amplifier to generate high actuation voltage for battery-powered free locomotion. From the theoretical standpoint, a reliable modeling framework that couples the actuator dynamics, hydroelasticity, and fish locomotion theory is essential to both design and control of robotic fish. Therefore, a distributed-parameter electroelastic model with fluid effects and actuator dynamics is coupled with the elongated body theory. Both in-air and underwater experiments are performed to verify the incorporation of hydrodynamic effects in the linear actuation regime. For electroelastically nonlinear actuation levels, experimentally obtained underwater vibration response is coupled with the elongated body theory to predict the thrust output. Experiments are conducted to validate the electrohydroelastic modeling approach employed in this work and to characterize the performance of an MFC bimorph propulsor. Finally, a wireless battery-powered preliminary robotic fish prototype is developed and tested in free locomotion at different frequency and voltage levels.

The locomotion of organisms whether by running, flying, or swimming is the result of multiple degree-of-freedom nervous and musculoskeletal systems interacting with an environment that often flows and deforms in response to movement. A major challenge in biology is to understand the locomotion of organisms that crawl or burrow within terrestrial substrates like sand, soil, and muddy sediments that display both solid and fluid-like behavior. In such materials, validated theories such as the Navier-Stokes equations for fluids do not exist, and visualization techniques (such as particle image velocimetry in fluids) are nearly nonexistent. In this dissertation we integrated biological experiment, numerical simulation, and a physical robot model to reveal principles of undulatory locomotion in granular media. First, we used high speed x-ray imaging techniques to reveal how a desert dwelling lizard, the sandfish, swims within dry granular media without limb use by propagating a single period sinusoidal traveling wave along its body, resulting in a wave efficiency, the ratio of its average forward speed to wave speed, of approximately 0.5. The wave efficiency was independent of the media preparation (loosely and tightly packed). We compared this observation against two complementary modeling approaches: a numerical model of the sandfish coupled to a discrete particle simulation of the granular medium, and an undulatory robot which was designed to swim within granular media. We used these mechanical models to vary the ratio of undulation amplitude (A) to wavelength (λ) and demonstrated that an optimal condition for sand-swimming exists which results from competition between A and λ. The animal simulation and robot model, predicted that for a single period sinusoidal wave, maximal speed occurs for A/ λ = 0.2, the same kinematics used by the sandfish. Inspired by the tapered head shape of the sandfish lizard, we showed that the lift forces and hence vertical position of the robot as it moves forward within granular media can be varied by designing an appropriate head shape and controlling its angle of attack, in a similar way to flaps or wings moving in fluids. These results support the biological hypotheses which propose that morphological adaptations of desert dwelling organisms aid in their subsurface locomotion. This work also demonstrates that the discovery of biological principles of high performance locomotion within sand can help create the next generation of biophysically inspired robots that could explore potentially hazardous complex flowing environments.

Personal robots with autonomy, mobility, and manipulation capabilities have the potential to dramatically improve quality of life for various user populations, such as older adults and individuals with motor impairments. Unfortunately, unstructured environments present many challenges that hinder robot deployment in ordinary homes. This thesis seeks to address some of these challenges through a new robotic sensing modality that leverages a small amount of environmental augmentation in the form of Ultra High Frequency (UHF) Radio-Frequency Identification (RFID) tags. Previous research has demonstrated the utility of infrastructure tags (affixed to walls) for robot localization; in this thesis, we specifically focus on tagging objects. Owing to their low-cost and passive (battery-free) operation, users can apply UHF RFID tags to hundreds of objects throughout their homes. The tags provide two valuable properties for robots: a unique identifier and receive signal strength indicator (RSSI, the strength of a tag's response). This thesis explores robot behaviors and radio frequency perception techniques using robot-mounted UHF RFID readers that enable a robot to efficiently discover, locate, and interact with UHF RFID tags applied to objects and people of interest. The behaviors and algorithms explicitly rely on the robot's mobility and manipulation capabilities to provide multiple opportunistic views of the complex electromagnetic landscape inside a home environment. The electromagnetic properties of RFID tags change when applied to common household objects. Objects can have varied material properties, can be placed in diverse orientations, and be relocated to completely new environments. We present a new class of optimization-based techniques for RFID sensing that are robust to the variation in tag performance caused by these complexities. We discuss a hybrid global-local search algorithm where a robot employing long-range directional antennas searches for tagged objects by maximizing expected RSSI measurements; that is, the robot attempts to position itself (1) near a desired tagged object and (2) oriented towards it. The robot first performs a sparse, global RFID search to locate a pose in the neighborhood of the tagged object, followed by a series of local search behaviors (bearing estimation and RFID servoing) to refine the robot's state within the local basin of attraction. We report on RFID search experiments performed in Georgia Tech's Aware Home (a real home). Our optimization-based approach yields superior performance compared to state of the art tag localization algorithms, does not require RF sensor models, is easy to implement, and generalizes to other short-range RFID sensor systems embedded in a robot's end effector. We demonstrate proof of concept applications, such as medication delivery and multi-sensor fusion, using these techniques. Through our experimental results, we show that UHF RFID is a complementary sensing modality that can assist robots in unstructured human environments.

The ability of robotic units to navigate various terrains is critical to the advancement of robotic operation in real world environments. Next generation robots will need to adapt to their environment in order to accomplish tasks that are either too hazardous, too time consuming, or physically impossible for human-beings. Such tasks may include accurate and rapid explorations of various planets or potentially dangerous areas on planet Earth. This research investigates a navigation control methodology for a wheel-legged robot based on active vision. The method presented is designed to control the reconfigurability of the robot (i.e. control the usage of the wheels and legs), depending upon the obstacle/terrain, based on perception. Surface estimation for robot reconfigurability is implemented using a region growing method and a characterization and traversability assessment generated from camera data. As a result, a mathematical approach that directs necessary navigation behavior is implemented to control robot mobility. The hybrid wheeled-legged rover possesses a four-legged or six-legged walking system as well as a four-wheeled mobility system.

Orientadores: Helder Anibal Hermini, Jose Manoel Balthazar / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Meêanica / Made available in DSpace on 2018-08-04T10:09:17Z (GMT). No. of bitstreams: 1 Pires_LeoSantana_M.pdf: 9313372 bytes, checksum: a9469afaba08752e7ef419dc781fe926 (MD5) Previous issue date: 2005 / Resumo: Uma aproximação unificada para projeto e controle de manipuladores robóticos que retenha todas as não linearidades inerentes na dinâmica é desenvolvido para uma configuração robô-motor considerado como um sistema interagente. Este projeto de sistema interagente, baseado no modelo de teoria de controle de desacoplagem não-linear de Beekmann, desacopla a configuração robô-motor para os subsistemas robô, motor e interação cm série. Esta aproximação está em contraste ao tratamento convencional do motor como uma pura fonte dc torque c o negligenciamento da interação dinâmica entre a junta do robô e o motor, e ao desconsiderar a formulação não-linear / Abstract: A unified approach to a robotic controI design, which retains all the nonlinearities inherent in the dynamics, is developed for the motor-robot configuration considered as an imeracting system. This control system design, based on the Beekmann model's nonlinear decoupling control theory with arbitrary pole placement, decouples the motor-robot configuration into robot, motor, and series compliance (interaction) subsystems. This approch is in contrast to the conventional treatment of the motor as apure torque source and the neglect of dynamic interactions between the robot joint and the motor drive mechanism and not consider the nonlinear formulation / Mestrado / Projeto Mecanico e Mecanica dos Solidos / Mestre em Engenharia Mecânica