Comparison of different repetitive control architectures: synthesis and comparison. Application to VSI Converters

Repetitive control is one of the most used control approaches to deal with periodic references/disturbances. It owes its properties to the inclusion of an internal model in the controller that corresponds to a periodic signal generator. However, there exist many different ways to include this internal model. This work presents a description of the different schemes by means of which repetitive control can be implemented. A complete analytic analysis and comparison is performed together with controller synthesis guidance. The voltage source inverter controller experimental results are included to illustrative conceptual developmentsPeer ReviewedPostprint (published version

Adaptive control of plants with input saturation: an approach for performance improvement

In this work, a new method for adaptive control of plants with input saturation is presented. The new anti-windup scheme can be shown to result in bounded closed-loop states under certain conditions on the plant and the initial closed-loop states. As an improvement in comparison to existing methods in adaptive control, a new degree of freedom is introduced in the control scheme. It allows to improve the closed-loop response when actually encountering input saturation without changing the closed-loop performance for unconstrained inputs.Diese Arbeit präsentiert eine neue Methode für die adaptive Regelung von Strecken mit Stellgrößenbegrenzung. Für das neue anti-windup Verfahren wird gezeigt, dass die Zustände des Regelkreises begrenzt bleiben, wenn dessen initiale Werte und die Regelstrecke bestimmte Bedingungen erfüllen. Eine Verbesserung im Vergleich zu existierenden Methoden wird durch die Einführung eines zusätzlichen Freiheitsgrades erzielt. Dieser erlaubt die Verbesserung der Regelgüte des geschlossenen Regelkreises, wenn das Eingangssignal sich in der Limitierung befindet, ohne diese sonst zu verändern

Learning and Reacting with Inaccurate Prediction: Applications to Autonomous Excavation

Motivated by autonomous excavation, this work investigates solutions to a class of problem where disturbance prediction is critical to overcoming poor performance of a feedback controller, but where the disturbance prediction is intrinsically inaccurate. Poor feedback controller performance is related to a fundamental control problem: there is only a limited amount of disturbance rejection that feedback compensation can provide. It is known, however, that predictive action can improve the disturbance rejection of a control system beyond the limitations of feedback. While prediction is desirable, the problem in excavation is that disturbance predictions are prone to error due to the variability and complexity of soil-tool interaction forces. This work proposes the use of iterative learning control to map the repetitive components of excavation forces into feedforward commands. Although feedforward action shows useful to improve excavation performance, the non-repetitive nature of soil-tool interaction forces is a source of inaccurate predictions. To explicitly address the use of imperfect predictive compensation, a disturbance observer is used to estimate the prediction error. To quantify inaccuracy in prediction, a feedforward model of excavation disturbances is interpreted as a communication channel that transmits corrupted disturbance previews, for which metrics based on the sensitivity function exist. During field trials the proposed method demonstrated the ability to iteratively achieve a desired dig geometry, independent of the initial feasibility of the excavation passes in relation to actuator saturation. Predictive commands adapted to different soil conditions and passes were repeated autonomously until a pre-specified finish quality of the trench was achieved. Evidence of improvement in disturbance rejection is presented as a comparison of sensitivity functions of systems with and without the use of predictive disturbance compensation

Paresthesia

Paresthesias are spontaneous or evoked abnormal sensations of tingling, burning, pricking, or numbness of a person's skin with no apparent long-term physical effect. Patients generally describe a lancinating or burning pain, often associated with allodynia and hyperalgesia. The manifestation of paresthesia can be transient or chronic. Transient paresthesia can be a symptom of hyperventilation syndrome or a panic attack, and chronic paresthesia can be a result of poor circulation, nerve irritation, neuropathy, or many other conditions and causes. This book is written by authors that are respected in their countries as well as worldwide. Each chapter is written so that everyone can understand, treat and improve the lives of each patient

Feasible, Robust and Reliable Automation and Control for Autonomous Systems

The Special Issue book focuses on highlighting current research and developments in the automation and control field for autonomous systems as well as showcasing state-of-the-art control strategy approaches for autonomous platforms. The book is co-edited by distinguished international control system experts currently based in Sweden, the United States of America, and the United Kingdom, with contributions from reputable researchers from China, Austria, France, the United States of America, Poland, and Hungary, among many others. The editors believe the ten articles published within this Special Issue will be highly appealing to control-systems-related researchers in applications typified in the fields of ground, aerial, maritime vehicles, and robotics as well as industrial audiences

Recent Advances in Robust Control

Robust control has been a topic of active research in the last three decades culminating in H_2/H_\infty and \mu design methods followed by research on parametric robustness, initially motivated by Kharitonov's theorem, the extension to non-linear time delay systems, and other more recent methods. The two volumes of Recent Advances in Robust Control give a selective overview of recent theoretical developments and present selected application examples. The volumes comprise 39 contributions covering various theoretical aspects as well as different application areas. The first volume covers selected problems in the theory of robust control and its application to robotic and electromechanical systems. The second volume is dedicated to special topics in robust control and problem specific solutions. Recent Advances in Robust Control will be a valuable reference for those interested in the recent theoretical advances and for researchers working in the broad field of robotics and mechatronics

THE EFFECTS OF CONSECUTIVE SOFTBALL WINDMILL PITCHES ON COORDINATION PATTERNS AND VARIABILITY, MUSCULAR STRENGTH, AND PITCHING PERFORMANCE

Upper and lower extremity musculoskeletal injuries occur at a similar rate in softball pitchers. Most of these injuries can be considered chronic in nature, which may result in symptoms being treated instead of considering the underlying mechanism for injury. Previous literature has primarily focused on discrete values such as joint ranges and kinematic peaks. The primary purpose was to examine inter-segmental and intra-limb coordination of the softball windmill pitch throughout a simulated game of softball and to determine if variability of these patterns change throughout multiple pitch counts. The secondary purpose is to identify if a difference between pre-pitching and post-pitching strength can be detected to determine if muscular fatigue, as defined by the inability to sustain the expected power output around a joint, has occurred. Pitching performance, defined as pitch velocity and accuracy, were also assessed. A total of 14 softball pitchers (17.9±2.3 years, 166.4±8.67 cm, 72.3±12.6 kg) successfully completed all strength assessments and pitching sequence. Pitchers completed strength assessments of the at baseline and immediately after a pitching sequence consisting of 105 fastballs. Vector coding was used to measure coordination and variability of Drive Leg Thigh v Pelvis, Pelvis v Torso, Pelvis v Humerus and Humerus v Forearm. Paired t-test or Wilcoxon Signed Ranks test was used to determine change in muscular strength. One-way repeated measures analysis of variance was performed to establish if differences in pitch velocity or accuracy varied between innings. Appropriate order parameter to encapsulate the behavior of the windmill pitch could not be established due to lack of fatigue or incorrect coordinative structures measured. Results demonstrated a significant increase in stride leg knee extension and trunk flexion peak torque, as percent body weight, after consecutive pitches. Differences were seen in pitch velocity but not accuracy across innings. While this study did not demonstrate the negative effects of consecutive pitching that were expected, results can provide a foundation for future research into windmill pitch mechanics to assist with injury prevention and performance optimization

The application of sliding mode observers to fault detection and isolation for multilevel converters

Multilevel converters have received significant interest recently as a result of their high power capability and good power quality. However due to the large number of sensitive components including power semiconductor devices and capacitors used in such circuits there is a high likelihood of component failures. This thesis considers one of the most promising multilevel topologies---the modular multilevel converter (MMC). Several methods are presented to detect and locate open-circuit faults in the power semiconductor devices in an MMC. These methods are based on sliding mode observers (SMOs). The signals used in the proposed methods are already available as measurement inputs to the control system and no additional measurement elements are required. An experimental MMC rig has been designed and built to validate these fault detection and isolation methods. The methods can be used with other multilevel converter topologies employing similar analysis and principles

Enhanced recording paradigms and advanced analyses of peripheral nerve fibers SPiike software

[eng] The aim of this work is to investigate the human nociceptive system at the peripheral level. Researchers are still debating how the pain perception arises from this very intricate network. The human perception is the most elusive part of our knowledge since different subsystems are involved. The external information such as noxious stimuli must be processed at the peripheral level and through signal cascades and transduction this signal must reach the brain. At the brain level the information is processed and some decisions are taken, such as the well-known fight-or-flight response. In the introduction, the author describes how the human nociceptive system works and in which way the noxious stimulus is converted into a signal understandable by the brain. Several cortical and subcortical areas are involved in this signal processing and going deeper in this assembly line the information becomes more abstracted. The whole pathway is fundamental for pain perception, however some diseases start at the peripheral level. This in turn makes wrong signals reaching the brain. The brain is then processing information that are not real and the responses do not suit with the needs. Therefore, the peripheral system must be investigated and understood firstly, since some central diseases may have a peripheral component as well. With this purpose in mind the microneurography technique has been used. This technique has got some complexity and a computer-aided system must be implemented. The hardware aims to filter out the noisy signal and perform recording and stimulation of the neural fibers. The software is instead used to make the stimulation and recording as automatic as possible in a way that researchers do not have to deal with a lot of parameters and steps to carry out this powerful but also time consuming technique. Some software are already available in the market however even if they work fine with slow conduction fibers such as C-fibers they cannot cope with faster neurons (e.g. Aδ fibers). The aim of this work is to create a software (i.e. SPiike) able to stimulate and record every type of fibers implementing advanced analysis technique as well. Furthermore, considering that some in vivo experiments have been pursued within the project to check the functionality of the software, more specifically in rats and mice, the comparison between human nociceptors and mouse nociceptors is depicted in this section. In the method section, the experimental approach is described step by step. This is composed by several systems that work together for the stimulation, recording and analysis of the neural fibers. The control and acquisition module is composed by the software and a data acquisition board that trigger the stimulator and record the filtered signal. The stimulation module is composed by a stimulator that can be tuned as wish through dedicated knobs. Then the stimulus is delivered to the animal model (or the human patient) and the signal is recorded though a microelectrode inserted into the sciatic nerve. The amplification module is filtering out the noisy signal and is feeding a audio monitor for helping the researcher during the insertion of the electrode inside the nerve and it provides support during the whole experiment giving insights on fiber discharges. In this section the whole setup is described in details as well as the devices needed for the recording. Furthermore, the software development that is the core of this project is described as well, with all the considerations that must be considered during coding. Indeed, the flow chart must be followed methodically in order to minimize bugs and errors that may arise in the final product. Thus a description of the compiler and the Matlab IDE is given along with system and software requirements for the making of the SPiike software. Eventually the explanation of embedded functionalities and capabilities of SPiike is depicted in the final part of this section. This software is indeed able to stimulate slow conducting fibers as well as faster ones, and enhanced analysis techniques such as supervised machine learning are implemented. In the results section, the graphical user interface of the Spiike software is reveled. It resembles the one of another software already available in the market, with a filtered signal and a raster plot embedded on it. However, this software is more user-friendly and it accounts with icons and drop-down menus that enhance the experience of the users during the use of the tool, making their interactions smooth and intuitive. The SPiike software is subdivide into two different tools, a recording module and a analysis module. The former allows the stimulation and recording of neural fibers with a stimulation frequency up to 1000Hz and some online analysis can be conducted to have insights on fibers type and behavior. The analysis module is instead a more powerful analysis environment that can retrieve the dataset recorded with the other module or with the LabChart software. Advanced analysis techniques are implemented in this module, this is meant to speed up fiber classification and analysis. Conclusion and discussion provide a overview on some results. These will be compared to those obtainable through other software available in the market. In this section, pros and cons of the new implemented software, SPiike, will be described as well