223 research outputs found

    Inverse dynamics of underactuated flexible mechanical systems governed by quasi-linear hyperbolic partial differential equations

    Get PDF
    Diese Arbeit befasst sich mit der inversen Dynamik unteraktuierter, flexibler, mechanischer Systeme, welche durch quasi-lineare hyperbolische partielle Differentialgleichungen beschrieben werden können. Diese Gleichungnen, sind zeitlich veränderlichen Dirichlet-Randbedingungen unterworfen, welche durch unbekannte, räumlich disjunkte, also nicht kollokierte Neumann-Randbedingungen erzwungen werden. Die zugrundeliegenden Gleichungen werden zunächst abstrakt hergeleitet, bevor verschiedene mechanische Systeme vorgestellt werden können, die mit der eingangs postulierten Formulierung übereinstimmen. Hierzu werden geometrisch exakte Theorien hergeleitet, welche in der Lage sind große Bewegungen schlanker Strukturen wie Seile und Balken, aber auch ganz allgemein, dreidimensionaler Festkörper zu beschreiben. In der Regel werden Anfangs-Randwertprobleme, die in der nichtlinearen Strukturdynamik auftreten, durch Anwendung einer sequentiellen Diskretisierung in Raum und Zeit gelöst. Diese Verfahren basieren für gewöhnlich auf einer räumlichen Diskretisierung mit finiten Elementen, gefolgt von einer geeigneten zeitlichen Diskretisierung, welche meist auf finiten Differenzen beruht. Ein kurzer Überblick über derartige sequentielle Integrationsverfahren für das vorliegende Anfangs-Randwertproblem wird zunächst anhand der direkten Formulierung des Problems gegeben werden. D.h. es wird zunächst das reine Neumann-Randproblem betrachtet, bevor anschließend ganz allgemein, verschiedene Möglichkeiten zur Einbindung etwaiger Dirichlet-Randbedingungen diskutiert werden. Darauf aufbauend wird das Problem der inversen Dynamik im Kontext räumlich diskreter mechanischer Systeme, welche rheonom-holonomen Servo-Bindungen unterliegen, eingeführt. Eine ausführliche Untersuchung dieser Art von gebundenen Systemen soll die grundlegenden Unterschiede zwischen Servo-Bindungen und klassischen Kontakt-Bindungen herausarbeiten. Die daraus resultierenden Folgen für die Entwicklung geeigneter numerisch stabiler Integrationsverfahren können dabei ebenfalls angesprochen werden, bevor zahlreich ausgewählte Beispiele vorgestellt werden können. Aufgrund der sehr eingeschränkten Anwendbarkeit der sequentiellen Lösung der inversen Dynamik in Raum und Zeit, wird eine eingehende Analyse des vorliegenden Anfangs-Randwertproblems unternommen. Vor allem durch die Freilegung der hyperbolischen Struktur der zugrundeliegenden partiellen Differentialgleichungen werden sich weitere Einblicke in das vorliegende Problem erhofft. Die Erforschung der daraus resultierenden Mechanismen der Wellenausbreitung in kontinuierlichen Strukturen öffnet die Tür zur Entwicklung numerisch stabiler Integrationsverfahren für die inverse Dynamik. So kann unter anderem eine Methode vorgestellt werden, die auf der Integration der partiellen Differentialgleichungen entlang charakteristischer Mannigfaltigkeiten beruht. Dies regt zu der Entwicklung neuartiger Galerkinverfahren an, die ebenfalls in dieser Arbeit vorgestellt werden können. Diese neu entwickelten Methoden können anschlie\ss end auf die Steuerung verschiedener mechanischer Systeme angewendet werden. Darüber hinaus können die neuartigen Integrationsverfahren auch auf flexible Mehrkörpersysteme übertragen werden. Angeführt seien hier beispielsweise die kooperative Steuerung eines an mehreren flexiblen Seilen aufgehängten starren Körpers oder die Steuerung des Endeffektors eines flexiblen mehrgliedrigen Schwenkarms. Ausgewählte numerische Beispiele verdeutlichen die Relevanz der hier vorgeschlagenen, in Raum und Zeit simultanen Integration des vorliegenden Anfangs-Randwertproblems

    Improving Automated Operations of Heavy-Duty Manipulators with Modular Model-Based Control Design

    Get PDF
    The rapid development of robotization and automation in mobile working machines aims to increase productivity and safety in many industrial sectors. In heavy-duty applications, hydraulically actuated manipulators are the common solution due to their large power-to-weight ratio. As hydraulic systems can exhibit nonlinear dynamic behavior, automated operations with closed-loop control become challenging. In industrial applications, the dexterity of operations for manipulators is ensured by providing interfaces to equip product variants with different tool attachments. By considering these domain-specific tool attachments for heavy-duty hydraulic manipulators (HHMs), the autonomous robotic operating development for all product variants might be a time-consuming process. This thesis aims to develop a modular nonlinear model-based (NMB) control method for HHMs to enable systematic NMB model reuse and control system modularity across different HHM product variants with actuators and tool attachments. Equally importantly, the properties of NMB control are used to improve the high-performance control for multi degrees-of-freedom robotic HHMs, as rigorously stability-guaranteed control systems have been shown to provide superior performance. To achieve these objectives, four research problems (RPs) on HHM controls are addressed. The RPs are focused on damping control methods in underactuated tool attachments, compensating for static actuator nonlinearities, and, equally significantly, improving overall control performance. The fourth RP is introduced for hydraulic series elastic actuators (HSEAs) in HHM applications, which can be regarded as supplementing NMB control with the aim of improving force controllability. Six publications are presented to investigate the RPs in this thesis. The control development focus was on modular NMB control design for HHMs equipped with different actuators and tool attachments consisting of passive and actuated joints. The designed control methods were demonstrated on a full-size HHM and a novel HSEA concept in a heavy-duty experimental setup. The results verified that modular control design for HHM systems can be used to decrease the modifications required to use the manipulator with different tool attachments and floating-base environments

    Estimation of an unknown disturbance of a waste shredder using an L-delay inverse model

    Get PDF
    In this work, a model-based system is developed for off-line estimation of an unknown disturbance of a waste shredder, utilizing the dynamic model of the shredder’s rotor and experimental data obtained from the shredder. During shredding, waste material generates an unknown resisting torque on the shredder’s rotor, which can be interpreted as an unknown disturbance input to the system. The application target is TANA shark 440-series industrial waste shredder of Finnish environmental technology company Tana Oy. The data used in the estimation includes pressure and rotational speed measurements, and reference values of hydraulic motors’ displacements. To perform the estimation, a linear state-space model of the hydraulic motors, gearboxes and rotor is constructed. The torques of hydraulic motors are inputs of the state-space model, and their values are computed based on pressure and rotational speed measurement, along with the reference values of the motors’ displacements. For the actual unknown disturbance estimation, a 1-delay inverse state-space model is derived from the rotor’s state-space model. This inverse model estimates the unknown disturbance input to the shredder using rotor speed measurement and calculated hydraulic motor torques. The unknown disturbance estimation result is validated using test data collected without material feed to the shredder, resulting in a zero disturbance input. The validation reveals an issue with the calculation of the hydraulic motor torques: the pressure without waste load is too low to determine mechanical efficiencies, leading to highly inaccurate torque calculations. An estimation conducted with a rough linear extrapolation of efficiency indicates that, on a large scale, estimating zero disturbance is moderately successful. However, due to inaccurate input signals, significant deviations from zero are observed in the result, especially during the transient phase of the rotor’s rotation. It is also concluded that identifying possible rotor model parameter changes due to operating conditions is challenging, due to uncertainty in the model’s input signals. In the future, tests performed with a test bench machine allow better evaluation of the accuracy of calculated hydraulic motor torques and the accuracy of non-zero unknown torque estimation. The sensitivity of the estimation result to changes in measurement data and rotor model parameters is investigated using simulation-based sensitivity analysis. The sensitivity analysis yields a clear outcome: the estimation result is several times more sensitive to changes in measurements used for calculating hydraulic motor torques than to changes in the rotor dynamic model parameters. Based on the sensitivity analysis, it is concluded that errors in the estimation result are most likely due to inaccuracies in the pressure measurements. The work proposes that placing the pressure sensors directly on the input and output sides of the hydraulic motors would enhance the accuracy of torque computation and thereby would also improve the accuracy of unknown disturbance estimation.Tässä työssä kehitetään mallipohjainen järjestelmä teollisen jäterepijän tuntemattoman häiriön off-line estimointiin käyttäen repijän roottorin dynaamista mallia sekä repijästä saatavaa kokeellista dataa. Revinnän aikana jäte aiheuttaa tuntemattoman suuruisen, repijän roottorin pyörintää vastustavan väännön, joka voidaan tulkita systeemin tuntemattomaksi häiriöinputiksi. Sovelluskohteena on suomalaisen ympäristöteknologiayritys Tana Oy:n TANA Shark 440-sarjan teollinen jäterepijä. Estimoinnissa repijästä hyödynnettävä data sisältää paine- ja pyörimisnopeusmittaukset sekä hydraulimoottorien kierrostilavuuksien asetusarvot. Estimointia varten työssä muodostetaan repijän hydraulimoottoreista, vaihdelaatikoista sekä roottorista lineaarinen tilamalli. Hydraulimoottorien vääntömomentit ovat tilamallin inputeina, joiden arvot lasketaan perustuen paine- ja pyörimisnopeusmittauksiin sekä moottorien kierrostilavuuksien asetusarvoon. Varsinaista tuntemattoman häiriön estimointia varten työssä muodostetaan roottorin tilamallista 1-viiveellinen inverssi tilamalli, joka estimoi repijän tuntemattoman häiriöinputin roottorin nopeusmittauksen sekä hydraulimoottorien laskettujen vääntömomenttien perusteella. Tuntemattoman häiriön estimointitulosta validoidaan käyttämällä testidataa, joka on kerätty ilman materiaalisyötettä, eli häiriöinputin arvo on nolla. Validoinnissa huomataan ongelma hydraulimoottorien vääntömomentin laskennassa: paine jää ilman jätekuormitusta niin alhaiselle tasolle, ettei moottorien mekaanisen hyötysuhteen arvoja ole määritelty. Tämän seurauksena vääntömomentin laskenta on hyvin epätarkkaa. Karkealla lineaarisella hyötysuhteen ekstrapoloinnilla suoritetun estimoinnin tulos osoittaa, että suuressa kuvassa nollahäiriön estimointi onnistuu kohtalaisesti, mutta epätarkkojen inputsignaalien johdosta tuloksessa esiintyy merkittäviä poikkamia nollasta, varsinkin roottorin pyörimisen transienttivaiheissa. Työssä todetaan, että mahdollisten toimintapisteestä johtuvien roottorimallin parametrien muutosten identifiointi on hankalaa, sillä myös mallin inputsignaalit sisältävät epävarmuutta. Tulevaisuudessa testipenkkilaitteella tehtävillä kokeilla kyetään paremmin arvioimaan hydraulimoottorien vääntömomentin laskennan tarkkuutta sekä nollasta poikkeavan tuntemattoman vastusväännön estimoinnin tarkkuutta. Estimointituloksen herkkyyttä mittausdatojen sekä roottorimallin parametrien muutoksille tutkitaan simulointipohjaisella herkkyysanalyysillä. Herkkyysanalyysi tuottaa selvän tuloksen: estimointitulos on moninkertaisesti herkempi muutoksille hydraulimoottorien vääntömomentin laskennassa käytettävissä mittausdatoissa kuin roottorin dynaamisen mallin parametreissa. Herkkyysanalyysin tuloksien perusteella todetaan, että estimointituloksen virheet ovat suurimmalla todennäköisyydellä peräisin painemittauksissa esiintyvistä epätarkkuuksista. Työssä todetaan, että paineantureiden sijoittaminen suoraan hydraulimoottoreiden tulo- ja lähtöpuolelle parantaisi vääntömomenttien laskennan ja sitä kautta myös tuntemattoman häiriön estimoinnin tarkkuutta

    PhD students´day FMST 2023

    Get PDF
    The authors gave oral presentations of their work online as part of a Doctoral Students’ Day held on 15 June 2023, and they reflect the challenging work done by the students and their supervisors in the fields of metallurgy, materials engineering and management. There are 82 contributions in total, covering a range of areas – metallurgical technology, thermal engineering and fuels in industry, chemical metallurgy, nanotechnology, materials science and engineering, and industrial systems management. This represents a cross-section of the diverse topics investigated by doctoral students at the faculty, and it will provide a guide for Master’s graduates in these or similar disciplines who are interested in pursuing their scientific careers further, whether they are from the faculty here in Ostrava or engineering faculties elsewhere in the Czech Republic. The quality of the contributions varies: some are of average quality, but many reach a standard comparable with research articles published in established journals focusing on disciplines of materials technology. The diversity of topics, and in some cases the excellence of the contributions, with logical structure and clearly formulated conclusions, reflect the high standard of the doctoral programme at the faculty.Ostrav

    Exploring Animal Behavior Through Sound: Volume 1

    Get PDF
    This open-access book empowers its readers to explore the acoustic world of animals. By listening to the sounds of nature, we can study animal behavior, distribution, and demographics; their habitat characteristics and needs; and the effects of noise. Sound recording is an efficient and affordable tool, independent of daylight and weather; and recorders may be left in place for many months at a time, continuously collecting data on animals and their environment. This book builds the skills and knowledge necessary to collect and interpret acoustic data from terrestrial and marine environments. Beginning with a history of sound recording, the chapters provide an overview of off-the-shelf recording equipment and analysis tools (including automated signal detectors and statistical methods); audiometric methods; acoustic terminology, quantities, and units; sound propagation in air and under water; soundscapes of terrestrial and marine habitats; animal acoustic and vibrational communication; echolocation; and the effects of noise. This book will be useful to students and researchers of animal ecology who wish to add acoustics to their toolbox, as well as to environmental managers in industry and government

    Multi-Robot Systems: Challenges, Trends and Applications

    Get PDF
    This book is a printed edition of the Special Issue entitled “Multi-Robot Systems: Challenges, Trends, and Applications” that was published in Applied Sciences. This Special Issue collected seventeen high-quality papers that discuss the main challenges of multi-robot systems, present the trends to address these issues, and report various relevant applications. Some of the topics addressed by these papers are robot swarms, mission planning, robot teaming, machine learning, immersive technologies, search and rescue, and social robotics

    Multibody Systems with Flexible Elements

    Get PDF
    Multibody systems with flexible elements represent mechanical systems composed of many elastic (and rigid) interconnected bodies meeting a functional, technical, or biological assembly. The displacement of each or some of the elements of the system is generally large and cannot be neglected in mechanical modeling. The study of these multibody systems covers many industrial fields, but also has applications in medicine, sports, and art. The systematic treatment of the dynamic behavior of interconnected bodies has led to an important number of formalisms for multibody systems within mechanics. At present, this formalism is used in large engineering fields, especially robotics and vehicle dynamics. The formalism of multibody systems offers a means of algorithmic analysis, assisted by computers, and a means of simulating and optimizing an arbitrary movement of a possibly high number of elastic bodies in the connection. The domain where researchers apply these methods are robotics, simulations of the dynamics of vehicles, biomechanics, aerospace engineering (helicopters and the behavior of cars in a gravitational field), internal combustion engines, gearboxes, transmissions, mechanisms, the cellulose industry, simulation of particle behavior (granulated particles and molecules), dynamic simulation, military applications, computer games, medicine, and rehabilitation

    A Robust Offline Precomputed Optimal Feedforward Control Action for the Real Time Feedback/Feedforward Control of Double Pendulum Gantry Cranes

    Get PDF
    none1openvalentina orsiniOrsini, Valentin

    Mechanical Engineering

    Get PDF
    The book substantially offers the latest progresses about the important topics of the "Mechanical Engineering" to readers. It includes twenty-eight excellent studies prepared using state-of-art methodologies by professional researchers from different countries. The sections in the book comprise of the following titles: power transmission system, manufacturing processes and system analysis, thermo-fluid systems, simulations and computer applications, and new approaches in mechanical engineering education and organization systems
    corecore