Theoretical and practical development of control approaches for redundantly actuated parallel kinematic machines

Die konsequente Weiterentwicklung parallelkinematischer Maschinen (PKM) führt auf eine strukturelle Erweiterung in Form einer Antriebsredundanz. Die wesentlichen Vorteile der Antriebsredundanz sind beispielsweise die Kompensation von Singularitäten im Arbeitsraum, eine erhöhte Endeffektor-Steifigkeit und eine optimale Verteilung der Antriebskräfte. Redundant angetriebene PKM (RA-PKM) sind darum prädestiniert für hochdynamische Pick-and-Place-Bewegungsaufgaben und neue Maschinenkonzepte. Die vorliegende Arbeit befasst sich mit der Frage, welche Konzepte und Verfahren für die Regelung der RA-PKM geeignet sind. Dabei zeigt sich, dass die Beschreibung in Endeffektor-Koordinaten, die Verwendung eines Störgrößenbeobachters auf der Basis des generalisierten Impulses sowie eine modellprädiktive Regelung sehr gute Ergebnisse hinsichtlich der Genauigkeit und des Implementierungs- und Rechenaufwandes ergeben. Dies gilt insbesondere, wenn große Reibkräfte z. B. in den Antrieben zu berücksichtigen sind. Deshalb ist dieses Verfahren für die industrielle Anwendung besonders geeignet. Da für alle hier betrachteten Regelungsverfahren ein mathematisches Modell erforderlich ist, nimmt die Beschreibung der Bewegungsgleichungen in unterschiedlichen Koordinaten einen breiten Raum der Arbeit ein. Es werden die Vor- und Nachteile der verschiedenen Beschreibungsformen wie z. B. die verschiedenen Arten der Singularitäten und die Eliminierung der Zwangskräfte mit Hilfe von Orthogonalprojektionen ausführlich dargestellt. Dabei wurde ein neuartiger Zugang für die Projektion der Bewegungsgleichungen in Endeffektor-Koordinaten hergeleitet. Als erstes Regelungskonzept wird die dezentrale Regelung betrachtet. Es wird gezeigt, wie die hier üblicherweise auftretenden antagonistischen Kräfte mit Hilfe eines Filters kompensiert werden können. Im Anschluss daran wird die große Klasse der modellbasierten Regelungen in den unterschiedlichen Koordinaten untersucht, wobei ein sogenannter Computed Torque Regler (CTC), d. h. die Verwendung einer Vorsteuerung in Form der inversen Dynamik, und ein Augmented PD-Regler (APD) zum Einsatz kommen. Die Gelenkgeschwindigkeiten werden mit Hilfe eines High-Gain-Beobachters und die Störgrößen mit Hilfe eines Störgrößenbeobachters rekonstruiert. Zum Schluss wird die schon erwähnte nichtlineare modellprädiktive Regelung in Endeffektor-Koordinaten beschrieben, wobei der zukünftige Trajektorienfehler durch eine optimale Stellgröße minimiert wird. Die resultierende Reglerstruktur hat die Form eines klassischen APD-Reglers mit variablen Verstärkungen. Die Reglereinstellung erfolgt durch die Prädiktion vollkommen automatisch. Die entwickelten Regler und Methoden wurden anhand eines ebenen Mechanismus mit zwei Freiheitsgraden unter Verwendung industrieller Torque-Motoren erprobt.The consistent further development of parallel kinematics machines (PKM) lead to a structural extension in terms of actuation redundancy. The major advantages of redundant actuation are for example the compensation of singularities in workspace, an increased end-effector stiffness and an optimal distribution of the control forces. Therefore redundantly actuated PKM (RA-PKM) are intended for high speed pick-and-place tasks and new machine concepts. This research work addresses the question which concepts and methods are qualified for the control of RA-PKM. It has been found that a formulation of motion equations in end-effector coordinates, the use of a disturbance observer based on the general momentum as well as a model predictive controller lead to very well results in terms of accuracy, implementation and computing time. This applies particularly, if large friction losses as they occur in drives, have to be taken into account. Therefore this method is particularly suitable for industrial applications. Since a mathematical model is needed for all proposed control schemes, the determination of motion equations in terms of different coordinate formulations makes up a large part of this report. The advantages and disadvantages, such as the different types of singularities and the elimination of constraint forces by means of orthogonal projections are elaborated. Although a novel approach for the projection of motion equations in terms of end effector coordinates is derived. At first, the decentralized control scheme is considered. It will be shown that antagonistic Forces which are inherent to the control-scheme can be compensated by means of a filter. Afterwards, the large class of model-based control schemes is reviewed in which a so called computed torque controller (CTC), i.e. the use of a feed-forward control in the form of the inverse dynamics, and an augmented PD (APD) controller are used. The joint velocities where observed by means of a high gain observer and the disturbances by means of a disturbance observer. Finally, the already mentioned nonlinear model predictive control scheme in terms of end-effector coordinates which minimizes the future trajectory error due to an optimal actuating variable is described. The resulting approach can be structurally incorporated into an APD controller with variable gains. The controller setup is an automated process due to the prediction. The proposed control schemes and methods where experimentally validated by means of a two degree of freedom planar mechanism with industrial torque motors

Modeling, analysis and control of robot-object nonsmooth underactuated Lagrangian systems: A tutorial overview and perspectives

International audienceSo-called robot-object Lagrangian systems consist of a class of nonsmooth underactuated complementarity Lagrangian systems, with a specific structure: an "object" and a "robot". Only the robot is actuated. The object dynamics can thus be controlled only through the action of the contact Lagrange multipliers, which represent the interaction forces between the robot and the object. Juggling, walking, running, hopping machines, robotic systems that manipulate objects, tapping, pushing systems, kinematic chains with joint clearance, crawling, climbing robots, some cable-driven manipulators, and some circuits with set-valued nonsmooth components, belong this class. This article aims at presenting their main features, then many application examples which belong to the robot-object class, then reviewing the main tools and control strategies which have been proposed in the Automatic Control and in the Robotics literature. Some comments and open issues conclude the article

Collected Works of Kirovohrad National Technical University Machinery in agricultural production, industry machine building, automation

У збірнику представлені статті, присвячені проблемам проектування та експлуатації сільськогосподарської техніки, технології виробництва, енергозбереження, автоматизації в промисловості та сільському господарстві. Наведені практичні рекомендації до використання результатів досліджень у галузях народного господарства. Збірник є фаховим виданням, в якому публікуються основні результати наукових досліджень вчених, аспірантів університету, а також інших навчальних закладів та промислових підприємств України. Збірник розрахований на наукових, науково-технічних працівників різних галузей науки та техніки, ВНЗ, здобувачів вчених ступенів і звань

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

Vibration, Control and Stability of Dynamical Systems

From Preface: This is the fourteenth time when the conference “Dynamical Systems: Theory and Applications” gathers a numerous group of outstanding scientists and engineers, who deal with widely understood problems of theoretical and applied dynamics. Organization of the conference would not have been possible without a great effort of the staff of the Department of Automation, Biomechanics and Mechatronics. The patronage over the conference has been taken by the Committee of Mechanics of the Polish Academy of Sciences and Ministry of Science and Higher Education of Poland. It is a great pleasure that our invitation has been accepted by recording in the history of our conference number of people, including good colleagues and friends as well as a large group of researchers and scientists, who decided to participate in the conference for the first time. With proud and satisfaction we welcomed over 180 persons from 31 countries all over the world. They decided to share the results of their research and many years experiences in a discipline of dynamical systems by submitting many very interesting papers. This year, the DSTA Conference Proceedings were split into three volumes entitled “Dynamical Systems” with respective subtitles: Vibration, Control and Stability of Dynamical Systems; Mathematical and Numerical Aspects of Dynamical System Analysis and Engineering Dynamics and Life Sciences. Additionally, there will be also published two volumes of Springer Proceedings in Mathematics and Statistics entitled “Dynamical Systems in Theoretical Perspective” and “Dynamical Systems in Applications”