A System of Autonomously Flying Helicopters for Load Transportation

Die Arbeit beschreibt Entwurf, Umsetzung und Validierung eines autonomen Lastentransportsystems, welches auf Basis mehrerer Modellhubschrauber realisiert wurde. Abhängig von den Anforderungen der zu transportierenden Last kann die Anzahl der verwendeten Hubschrauber individuell angepasst werden. Die präsentierten Modelle und Regler wurden durch Computersimulationen und reale Flugversuche verifiziert. Zwei nichtlineare Modelle werden präsentiert: Ein Model für Konfigurationen bestehend aus einem Helikopter und einer Last (single-lift) und eines für Konfigurationen bestehend aus zwei bzw. mehreren Helikoptern und einer Last (dual- und multi-lift). Neben diesen komplexen Modellen werden vereinfachte Modelle vorgestellt, die für den Reglerentwurf verwendet werden. Ein generischer Orientierungsregler wird entwickelt, der für die Regelung aller beschriebenen Transportkonfigurationen verwendet werden kann. Durch die Nutzung dieses Reglers vereinfacht sich der Entwurf der Translationsregler erheblich. Drei Translationsregler werden beschrieben: Ein Regler für single-lift Konfigurationen, der eine aktive Unterdrückung von Lastschwingungen erlaubt, und ein verteilter Regler für multi-lift Konfigurationen. Weiterhin wird ein dual-lift Regler präsentiert, der eine Kombination der anderen Regler darstellt. Die Regler für dual- und multi-lift Konfigurationen verwenden keine mechanischen Hilfskonstrukte wie Abstandshalter. Die Position der Last wird durch die Orientierung des Seils, gemessen nahe dem Helikopterrumpf, bestimmt. Externe Störungen wie Windstöße können eine Eigenschwingung des Seils anregen, welche die ermittelte Lastposition verfälscht. Die Eigenschwingung des Seils sowie der Einfluss der verwendeten Messeinrichtung werden analysiert. Auf Basis dieser Analyse wird ein Lastbeobachter entwickelt und in mehreren Experimenten verifiziert. Dieser Lastbeobachter ist von essentieller Wichtigkeit für den sicheren Betrieb des Lastentransportsystems, insbesondere bei schlechten Wetterbedingungen. Die entwickelten nichtlinearen Modelle des Systems wie auch die Regler der single- und multi-lift Konfigurationen wurden durch Flugversuche validiert. Dabei hat das System bewiesen, dass es auch bei sehr schlechten Wetterbedingungen einsetzbar iThis work covers the design, realization and validation of an autonomous load transportation system, utilizing several small size helicopters. The number of participating helicopters is configurable for the described system, depending on the requirements of the transported load. The presented models and controllers have been validated in computer simulation and flight experiments. Two non-linear models are presented: One model covers single-lift and one model covers dual- and multi-lift configurations. Simplified models are introduced beside the complex models, which are utilized for the translation controller design. A generic orientation controller is presented, which is applicable for the control of all presented slung load configurations. The utilization of this controller significantly simplifies the design of the translation controllers. The independence from the actual slung load configuration is achieved through measurement of the rope force vector in the rope attachment point, which is located on the helicopter fuselage. Three translation controllers are described: A controller for single-lift configurations, which allows the active compensation of load oscillations and a distributed controller for multi-lift configurations. A dual-lift translation controller is presented, which resembles a combination of single- and multi-lift translation controller. The presented controllers for dual- or multi-lift configurations do not utilize auxiliary constructs, like spreader-bars. The position of the load is estimated from the measured orientation of the rope, close to the helicopter fuselage. External disturbances, like wind gusts, are able to stimulate internal oscillations of the rope, which disturb the estimated load position. The internal motion of the rope as well as the influence of the used measurement device are analyzed and a flexible rope model is presented. Based on the results a load motion observer is developed and validated in several experiments. This load motion observer is essential for the safe operation of the slung load system, especially during bad weather conditions. The derived non-linear models of the system as well as the proposed controllers for single- and multi-lift configurations have been validated in flight experiments. The system has been proven to be operable even in presence of adverse weather conditions

Control Methods for Improving Tracking Accuracy and Disturbance Rejection in Ball Screw Feed Drives

This thesis studies in detail the dynamics of ball screw feed drives and expands understanding of the factors that impose limitations on their performance. This knowledge is then used for developing control strategies that provide adequate command following and disturbance rejection. High performance control strategies proposed in this thesis are designed for, and implemented on, a custom-made ball screw drive. A hybrid Finite Element (FE) model for the ball screw drive is developed and coded in Matlab programming language. This FE model is employed for prediction of natural frequencies, mode shapes, and Frequency Response Functions (FRFs) of the ball screw setup. The accuracy of FRFs predicted for the ball screw mechanism alone is validated against the experimental measurements obtained through impact hammer testing. Next, the FE model for the entire test setup is validated. The dynamic characteristics of the actuator current controller are also modeled. In addition, the modal parameters of the mechanical structure are extracted from measured FRFs, which include the effects of current loop dynamics. To ensure adequate command following and disturbance rejection, three motion controllers with active vibration damping capability are developed. The first is based on the sensor averaging concept which facilitates position control of the rigid body dynamics. Active damping is added to suppress vibrations. To achieve satisfactory steady state response, integral action over the tracking error is included. The stability analysis and tuning procedure for this controller is presented together with experimental results that prove the effectiveness of this method in high-speed tracking and cutting applications. The second design uses the pole placement technique to move the real component of two of the oscillatory poles further to the left along the real axis. This yields a faster rigid body response with less vibration. However, the time delay from the current loop dynamics imposes a limitation on how much the poles can be shifted to the left without jeopardizing the system’s stability. To overcome this issue, a lead filter is designed to recover the system phase at the crossover frequency. When designing the Pole Placement Controller (PPC) and the lead filter concurrently, the objective is to minimize the load side disturbance response against the disturbances. This controller is also tested in high-speed tracking and cutting experiments. The third control method is developed around the idea of using the pole placement technique for active damping of not only the first mode of vibration, but also the second and third modes as well. A Kalman filter is designed to estimate a state vector for the system, from the control input and the position measurements obtained from the rotary and linear encoders. The state estimates are then fed back to the PPC controller. Although for this control design, promising results in terms of disturbance rejection are obtained in simulations, the Nyquist stability analysis shows that the closed loop system has poor stability margins. To improve the stability margins, the McFarlane-Glover robustness optimization method is attempted, and as a result, the stability margins are improved, but at the cost of degraded performance. The practical implementation of the third controller, was, unfortunately, not successful. This thesis concludes by addressing the problem of harmonic disturbance rejection in ball screw drives. It is shown that for cases where a ball screw drive is subject to high-frequency disturbances, the dynamic positioning accuracy of the ball screw drive can be improved significantly by adopting an additional control scheme known as Adaptive Feedforward Cancellation (AFC). Details of parameter tuning and stability analysis for AFC are presented. At the end, successful implementation and effectiveness of AFC is demonstrated in applications involving time periodic or space periodic disturbances. The conclusions drawn about the effectiveness of the AFC are based on results obtained from the high-speed tracking and end-milling experiments

International Symposium on Magnetic Suspension Technology, Part 1

The goal of the symposium was to examine the state of technology of all areas of magnetic suspension and to review related recent developments in sensors and controls approaches, superconducting magnet technology, and design/implementation practices. The symposium included 17 technical sessions in which 55 papers were presented. The technical session covered the areas of bearings, sensors and controls, microgravity and vibration isolation, superconductivity, manufacturing applications, wind tunnel magnetic suspension systems, magnetically levitated trains (MAGLEV), space applications, and large gap magnetic suspension systems

Resource-aware motion control:feedforward, learning, and feedback

Controllers with new sampling schemes improve motion systems’ performanc

From plain visualisation to vibration sensing: using a camera to control the flexibilities in the ITER remote handling equipment

Thermonuclear fusion is expected to play a key role in the energy market during the second half of this century, reaching 20% of the electricity generation by 2100. For many years, fusion scientists and engineers have been developing the various technologies required to build nuclear power stations allowing a sustained fusion reaction. To the maximum possible extent, maintenance operations in fusion reactors are performed manually by qualified workers in full accordance with the "as low as reasonably achievable" (ALARA) principle. However, the option of hands-on maintenance becomes impractical, difficult or simply impossible in many circumstances, such as high biological dose rates. In this case, maintenance tasks will be performed with remote handling (RH) techniques. The International Thermonuclear Experimental Reactor ITER, to be commissioned in southern France around 2025, will be the first fusion experiment producing more power from fusion than energy necessary to heat the plasma. Its main objective is “to demonstrate the scientific and technological feasibility of fusion power for peaceful purposes”. However ITER represents an unequalled challenge in terms of RH system design, since it will be much more demanding and complex than any other remote maintenance system previously designed. The introduction of man-in-the-loop capabilities in the robotic systems designed for ITER maintenance would provide useful assistance during inspection, i.e. by providing the operator the ability and flexibility to locate and examine unplanned targets, or during handling operations, i.e. by making peg-in-hole tasks easier. Unfortunately, most transmission technologies able to withstand the very specific and extreme environmental conditions existing inside a fusion reactor are based on gears, screws, cables and chains, which make the whole system very flexible and subject to vibrations. This effect is further increased as structural parts of the maintenance equipment are generally lightweight and slender structures due to the size and the arduous accessibility to the reactor. Several methodologies aiming at avoiding or limiting the effects of vibrations on RH system performance have been investigated over the past decade. These methods often rely on the use of vibration sensors such as accelerometers. However, reviewing market shows that there is no commercial off-the-shelf (COTS) accelerometer that meets the very specific requirements for vibration sensing in the ITER in-vessel RH equipment (resilience to high total integrated dose, high sensitivity). The customisation and qualification of existing products or investigation of new concepts might be considered. However, these options would inevitably involve high development costs. While an extensive amount of work has been published on the modelling and control of flexible manipulators in the 1980s and 1990s, the possibility to use vision devices to stabilise an oscillating robotic arm has only been considered very recently and this promising solution has not been discussed at length. In parallel, recent developments on machine vision systems in nuclear environment have been very encouraging. Although they do not deal directly with vibration sensing, they open up new prospects in the use of radiation tolerant cameras. This thesis aims to demonstrate that vibration control of remote maintenance equipment operating in harsh environments such as ITER can be achieved without considering any extra sensor besides the embarked rad-hardened cameras that will inevitably be used to provide real-time visual feedback to the operators. In other words it is proposed to consider the radiation-tolerant vision devices as full sensors providing quantitative data that can be processed by the control scheme and not only as plain video feedback providing qualitative information. The work conducted within the present thesis has confirmed that methods based on the tracking of visual features from an unknown environment are effective candidates for the real-time control of vibrations. Oscillations induced at the end effector are estimated by exploiting a simple physical model of the manipulator. Using a camera mounted in an eye-in-hand configuration, this model is adjusted using direct measurement of the tip oscillations with respect to the static environment. The primary contribution of this thesis consists of implementing a markerless tracker to determine the velocity of a tip-mounted camera in an untrimmed environment in order to stabilise an oscillating long-reach robotic arm. In particular, this method implies modifying an existing online interaction matrix estimator to make it self-adjustable and deriving a multimode dynamic model of a flexible rotating beam. An innovative vision-based method using sinusoidal regression to sense low-frequency oscillations is also proposed and tested. Finally, the problem of online estimation of the image capture delay for visual servoing applications with high dynamics is addressed and an original approach based on the concept of cross-correlation is presented and experimentally validated

Adaptive Control

Adaptive control has been a remarkable field for industrial and academic research since 1950s. Since more and more adaptive algorithms are applied in various control applications, it is becoming very important for practical implementation. As it can be confirmed from the increasing number of conferences and journals on adaptive control topics, it is certain that the adaptive control is a significant guidance for technology development.The authors the chapters in this book are professionals in their areas and their recent research results are presented in this book which will also provide new ideas for improved performance of various control application problems

Robot Manipulators

Robot manipulators are developing more in the direction of industrial robots than of human workers. Recently, the applications of robot manipulators are spreading their focus, for example Da Vinci as a medical robot, ASIMO as a humanoid robot and so on. There are many research topics within the field of robot manipulators, e.g. motion planning, cooperation with a human, and fusion with external sensors like vision, haptic and force, etc. Moreover, these include both technical problems in the industry and theoretical problems in the academic fields. This book is a collection of papers presenting the latest research issues from around the world

An energy based formalism for state estimation and motion control

This work presents an energy based state estimation formalism for a class of dynamical systems with inaccessible/unknown outputs and systems at which sensor utilization is costly, impractical or measurements can not be taken. The physical interactions among most of the dynamical subsystems represented mathematically in terms of Dirac structures allow power exchange through the power ports of these subsystems. Power exchange is conceptually considered as information exchange among the dynamical subsystems and further utilized to develop a natural feedback-like information from a class of dynamical systems with inaccessible/unknown outputs. The feedback-like information is utilized in realizing state observers for this class of dynamical systems. Necessary and sufficient conditions for observability are studied. In addition, estimation error asymptotic convergence stability of the proposed energy based state variable observer is proved for systems with linear and nonlinear dynamics. Robustness of the asymptotic convergence stability is analyzed over a range of parameter deviations, model uncertainties and unknown initial conditions. The proposed energy based state estimation formalism allows realization of the motion and force control from measurements taken from a single subsystem within the entire dynamical system. This in turn allows measurements to be taken from this single subsystem, whereas the rest of the dynamical system is kept free from measurements. Experiments are conducted on dynamical systems with single input and multiple inaccessible outputs in order to verify the validity of the proposed energy based state estimation and control formalism

Volume 1 – Symposium

We are pleased to present the conference proceedings for the 12th edition of the International Fluid Power Conference (IFK). The IFK is one of the world’s most significant scientific conferences on fluid power control technology and systems. It offers a common platform for the presentation and discussion of trends and innovations to manufacturers, users and scientists. The Chair of Fluid-Mechatronic Systems at the TU Dresden is organizing and hosting the IFK for the sixth time. Supporting hosts are the Fluid Power Association of the German Engineering Federation (VDMA), Dresdner Verein zur Förderung der Fluidtechnik e. V. (DVF) and GWT-TUD GmbH. The organization and the conference location alternates every two years between the Chair of Fluid-Mechatronic Systems in Dresden and the Institute for Fluid Power Drives and Systems in Aachen. The symposium on the first day is dedicated to presentations focused on methodology and fundamental research. The two following conference days offer a wide variety of application and technology orientated papers about the latest state of the art in fluid power. It is this combination that makes the IFK a unique and excellent forum for the exchange of academic research and industrial application experience. A simultaneously ongoing exhibition offers the possibility to get product information and to have individual talks with manufacturers. The theme of the 12th IFK is “Fluid Power – Future Technology”, covering topics that enable the development of 5G-ready, cost-efficient and demand-driven structures, as well as individual decentralized drives. Another topic is the real-time data exchange that allows the application of numerous predictive maintenance strategies, which will significantly increase the availability of fluid power systems and their elements and ensure their improved lifetime performance. We create an atmosphere for casual exchange by offering a vast frame and cultural program. This includes a get-together, a conference banquet, laboratory festivities and some physical activities such as jogging in Dresden’s old town.:Group A: Materials Group B: System design & integration Group C: Novel system solutions Group D: Additive manufacturing Group E: Components Group F: Intelligent control Group G: Fluids Group H | K: Pumps Group I | L: Mobile applications Group J: Fundamental

Proceedings of the ECCOMAS Thematic Conference on Multibody Dynamics 2015

This volume contains the full papers accepted for presentation at the ECCOMAS Thematic Conference on Multibody Dynamics 2015 held in the Barcelona School of Industrial Engineering, Universitat Politècnica de Catalunya, on June 29 - July 2, 2015. The ECCOMAS Thematic Conference on Multibody Dynamics is an international meeting held once every two years in a European country. Continuing the very successful series of past conferences that have been organized in Lisbon (2003), Madrid (2005), Milan (2007), Warsaw (2009), Brussels (2011) and Zagreb (2013); this edition will once again serve as a meeting point for the international researchers, scientists and experts from academia, research laboratories and industry working in the area of multibody dynamics. Applications are related to many fields of contemporary engineering, such as vehicle and railway systems, aeronautical and space vehicles, robotic manipulators, mechatronic and autonomous systems, smart structures, biomechanical systems and nanotechnologies. The topics of the conference include, but are not restricted to: ● Formulations and Numerical Methods ● Efficient Methods and Real-Time Applications ● Flexible Multibody Dynamics ● Contact Dynamics and Constraints ● Multiphysics and Coupled Problems ● Control and Optimization ● Software Development and Computer Technology ● Aerospace and Maritime Applications ● Biomechanics ● Railroad Vehicle Dynamics ● Road Vehicle Dynamics ● Robotics ● Benchmark ProblemsPostprint (published version