Energy-based control design for mechanical systems:Applications of the port-Hamiltonian approach

De moderne maatschappij vraagt naar robotsystemen die complexe taken kunnen uitvoeren onder verschillende omstandigheden. De steeds hogere eisen vanuit de industrie, hogere standaards en toepassingen in opkomende gebieden zoals huishoudelijke toepassingen (domotica) en mobiele robots, vereisen intelligente systemen die snel en nauwkeurig zijn. Dit proefschrift beschrijft de ontwikkeling van nieuwe regelmethoden voor niet-lineaire mechanische systemen volgens de energiegebaseerde benadering. De ontwikkelde regelmethoden bieden een oplossing om te voldoen aan de eis van snelle en nauwkeurige intelligente systemen. De ontwikkelde regelmethoden zijn geschikt voor algemene mechanische systemen, met simulaties en experimenten van een robot-manipulator

Visual Servoing of Quadrotors for Perching by Hanging From Cylindrical Objects

This paper addresses vision-based localization and servoing for quadrotors to enable autonomous perching by hanging from cylindrical structures using only a monocular camera. We focus on the problems of relative pose estimation, control, and trajectory planning for maneuvering a robot relative to cylinders with unknown orientations. We first develop a geometric model that describes the pose of the robot relative to a cylinder. Then, we derive the dynamics of the system, expressed in terms of the image features. Based on the dynamics, we present a controller which guarantees asymptotic convergence to the desired image space coordinates. Finally, we develop an effective method to plan dynamically-feasible trajectories in the image space, and we provide experimental results to demonstrate the proposed method under different operating conditions such as hovering, trajectory tracking, and perching

Control of Nonprehensile Planar Rolling Manipulation: A Passivity-Based Approach

This paper presents a new procedure to design a control law using the classical interconnection and damping assignment technique within the passivity-based port-Hamiltonian framework. The sought goal is to reduce the complexity of solving the so-called matching equations. The proposed approach is applied to two case studies of planar rolling nonprehensile manipulation, namely, the ball-and-beam and the eccentric disk-on-disk. The performance of the resulting controllers is illustrated through both simulations and experimental results, showing the applicability of the design in a real setup

Grasping, Perching, And Visual Servoing For Micro Aerial Vehicles

Micro Aerial Vehicles (MAVs) have seen a dramatic growth in the consumer market because of their ability to provide new vantage points for aerial photography and videography. However, there is little consideration for physical interaction with the environment surrounding them. Onboard manipulators are absent, and onboard perception, if existent, is used to avoid obstacles and maintain a minimum distance from them. There are many applications, however, which would benefit greatly from aerial manipulation or flight in close proximity to structures. This work is focused on facilitating these types of close interactions between quadrotors and surrounding objects. We first explore high-speed grasping, enabling a quadrotor to quickly grasp an object while moving at a high relative velocity. Next, we discuss planning and control strategies, empowering a quadrotor to perch on vertical surfaces using a downward-facing gripper. Then, we demonstrate that such interactions can be achieved using only onboard sensors by incorporating vision-based control and vision-based planning. In particular, we show how a quadrotor can use a single camera and an Inertial Measurement Unit (IMU) to perch on a cylinder. Finally, we generalize our approach to consider objects in motion, and we present relative pose estimation and planning, enabling tracking of a moving sphere using only an onboard camera and IMU

Visual Servoing in Robotics

Visual servoing is a well-known approach to guide robots using visual information. Image processing, robotics, and control theory are combined in order to control the motion of a robot depending on the visual information extracted from the images captured by one or several cameras. With respect to vision issues, a number of issues are currently being addressed by ongoing research, such as the use of different types of image features (or different types of cameras such as RGBD cameras), image processing at high velocity, and convergence properties. As shown in this book, the use of new control schemes allows the system to behave more robustly, efficiently, or compliantly, with fewer delays. Related issues such as optimal and robust approaches, direct control, path tracking, or sensor fusion are also addressed. Additionally, we can currently find visual servoing systems being applied in a number of different domains. This book considers various aspects of visual servoing systems, such as the design of new strategies for their application to parallel robots, mobile manipulators, teleoperation, and the application of this type of control system in new areas

Sensor-based formation control using a generalised rigidity framework and passivity techniques

The research in this thesis addresses the subject of sensor-based formation control for a network of autonomous agents. The task of formation control involves the stabilisation of the agents to a desired set of relative states, with the possible additional objective of manoeuvring the agents while maintaining this formation. Although the formation control challenge has been widely studied in the literature, many existing control strategies are based on full state information, and give little consideration to the sensor modalities available for the task. The focus of this thesis lies in the use of a generic arrangement of partial state measurements as can commonly be acquired by onboard sensors; for example, time-of-flight sensors can be used to measure the distances between vehicles, and onboard cameras can provide the bearing from one vehicle to each of the others. Particular aspects of the problem that are addressed in this thesis include (i) ways of modelling the formation control task, (ii) methods of analysing the system's behaviour, and (iii) the design of a formation control scheme based on generic arrangements of sensors that provide only partial position information. A key contribution in this thesis is a generalisation of the classical notion of rigidity, which considers the use of distance constraints between agents in R^2 or R^3 to specify a rigid body (or formation). This enables the concept of rigidity to be applied to agent networks involving a variety of (possibly non-Euclidean) state-spaces, with a generic set of state constraints that may, for example, include bearings between agents as well as distances. I demonstrate that this framework is very well-suited for modelling a wide variety of formation control problems (addressing goal (i) above), and I extend several fundamental results from classical rigidity theory in order to provide significant insight for system analysis (addressing goal (ii) above). To design a formation control scheme that uses generic partial position measurements (addressing goal (iii) above), I employ a modular passivity-based approach that is developed using the bondgraph modelling formalism. I illustrate how adaptive compensation can be incorporated into this design approach in order to account for the unknown position information that is not available from the onboard sensors. Although formation control is the subject of this thesis, it should be noted that the rigidity-based and passivity-based frameworks developed here are quite general and may be applied to a wide range of other problems

Rapid scan EPR spectroscopy on DNP relevant radicals

Elektronová paramagnetická resonanční (EPR) spektroskopie je fyzikálněchemická metoda sloužící pro zkoumání látek s nepárovými elektrony. Zkoumá rozdělení energií spinu nepárového elektronu v magnetickém poli a přechody mezi jednotlivými spinovými stavy vyvolané působením mikrovlnného záření. Tato bakalářská práce je zaměřena na popis EPR spektroskopie, na výpočet relaxačních časů pomocí rychlých skenů radikálů a na vývoj automatického párovacího softwaru pro skládání Gaussovských paprsků. Výsledek této práce je implementace vyvinutého softwaru, vyhodnocení jeho vlivu na kvalitu signálu a následný výpočet relaxačních časů.Electron paramagnetic resonance (EPR) spectroscopy is a Physico-chemical method used to investigate substances with unpaired electrons. It investigates the distribution of spin energies of an unpaired electron in a magnetic field and the transitions between individual spin states caused by the action of microwave radiation. This bachelor thesis is focused on the description of EPR spectroscopy, the calculation of relaxation times using the rapid scan method on radicals and the development of automatic coupling software for Gaussian beam coupling. The result of this work is the implementation of the developed software, evaluation of its influence on the signal quality and subsequent calculation of relaxation times.

Remotely-sensed atomic magnetometry

Thesis (M.S.)--Boston UniversityCoherent population trapping (CPT) effects can be realized with frequency mod- ulated lasers and compact vapor cells of alkali metals such as Rubidium-87. Using these optical resonances, one can readily measure the hyperfine separation of this three-level atom. In the presence of a magnetic field, the Zeeman effect causes magnetic sublevels of these hyperfine ground states to split; the frequency of such splitting can be measured in an ensemble of Rubidium atoms with the magnetometer we have constructed. While other groups have constructed magnetometers based on these effects, none to our knowledge have investigated the capability to measure magnetic fields remotely. Most atomic-optical magnetometers,colocate the transmit and receive optical system with the vapor cell itself or require fiber optics at the location of the cell; our free-space technique with a reflective geometry lends itself to measurement at distances greater than could be achieved with those methods. We have developed a laboratory FM laser spectrometer that interrogates CPT resonances to measure magnetic fields with the vapor cell not necessarily co-located with the spectrometer. Its intrinsic linewidth (in the presence of transit-time broadening) is less than 30 kilohertz, which allows measurements on the order of 2 microtesla. We present results concerning the accuracy of the magnetometer at about one meter of standoff distance, and describe considerations for measurements at longer distances