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Automatic panel benders of Salvagnini Maschinenbau GmbH enable high-quality and high-efficient production of sheet metal components. To achieve the steadily increasing requirements on precision, a model-based adaptive concept has been developed controlling the complete production process as a digital twin, from CAD data to the final sheet metal part. First, an overview of the underlying simulation models with different levels of detail is given. The models consider the elastoplastic deformation of the metal sheets as well as the elastic machine components and mechatronic models of the powertrain. Secondly, an overview is given of the adaptive production concept allowing the real-time adaption of the machine to changing process parameters like material properties. Finally, all production steps are controlled by a digital twin based on this model-based adaptive strategy. The paper demonstrates the successful transfer of scientific results to an industrial application.

Um den steigenden Anforderungen an moderne Produktionsmaschinen hinsichtlich Präzision und Qualität bei optimaler Ressourceneffizienz gerecht zu werden, sind neue Konzepte zur Reduktion des Material- und Energieverbrauchs bei deren Herstellung notwendig. In dieser Arbeit wird eine empirisch begründete Strategie zur Gewichts- und Energiereduktion in Blechbiegeautomaten vorgestellt, bei der mittels Topologie-Optimierung eine Leichtbau-Ausführung geometrisch komplexer und bewegter Maschinenteile erzielt wird. Diese Strategie wurde bei dreidimensionalen Maschinenrahmen der Maschinenfamilie „Lean Panel Bender“ der Salvagnini Maschinenbau GmbH erfolgreich angewendet und erbrachte gegenüber älteren Ausführungen große Einsparungen an Gewicht, Fertigungs- und Transportkosten sowie beim Energieverbrauch. So ist eine sowohl kostengünstige als auch hochpräzise Herstellung komplex geformter Blechprodukte möglich, sowohl bei Losgröße 1 als auch in der Serie

Nachfolgend werden einige wissenschaftliche Aspekte der Echtzeit-Materialerkennungsstrategie MAC diskutiert, die in der neuen Maschinenfamilie LEAN PANEL BENDER der Firma Salvagnini Maschinenbau realisiert ist und die eine hochprazise und hocheffiziente Herstellung von komplex geformten Blechprodukten sowohl bei Losgrose 1 als auch in der Serie erlaubt.

This paper is concerned with the dynamics of hyperelastic solids and structures. We seek for a smart control actuation that produces a desired (prescribed) displacement field in the presence of transient imposed forces. In the literature, this problem is denoted as displacement tracking, or also as shape morphing problem. One talks about shape control, when the displacements to be tracked do vanish. In the present paper, it is assumed that the control actuation is provided by imposed eigenstrains, e.g., by the electric field in piezoelectric actuators, or by thermal actuators, or via analogous physical effects, such as magneto-striction or pre-stress. Structures with a controlled eigenstrain-type actuation belong to the class of smart structures. The action of the eigenstrains can be conveniently characterized by actuation stresses. Our theoretical derivations are performed in the framework of the theory of small incremental dynamic deformations superimposed upon a statically pre-deformed configuration of a hyperelastic solid or structure. We particularly ask for a distribution of incremental actuation stresses, such that the incremental displacements follow exactly a prescribed trajectory field, despite the imposed incremental forces are present. An exact solution of this problem is presented under the assumption that the actuation stresses can be tailored freely and applied everywhere within the body. Extending a Neumann-type solution strategy, it is shown that the actuation stresses due to the distributed control eigenstrains must satisfy certain quasi-static equilibrium conditions, where auxiliary body-forces and auxiliary surface tractions are to be taken into account. The latter auxiliary loading can be directly computed from the imposed forces and from the desired displacement field to be tracked. Hence, despite the problem is a dynamic one, a straightforward computation of proper actuator distributions can be obtained in the framework of quasi-static equilibrium conditions. Necessary conditions for the functioning of this concept are presented. Particularly, it must be required that the intermediate configuration is infinitesimally superstable. Previous results of our group for the case of shape control and displacement tracking in linear elastic structures are included as special cases. The high potential of the solution is demonstrated via Finite Element computations for an irregularly shaped four-corner plate in a state of plain strain.

In the present article, we analyze a d36-effect piezoelectric torsion transducer following the Saint-Venant torsion theory taking the electrical field into account. A representation of the stress function, the electric potential, and the warping function are derived and solved with finite differences. Then, the one-dimensional governing equations at the structural beam level, including the constitutive relations as well as the balance equations for the dynamics of the transducer, are presented. The axial moment and the total charge are computed as functions of the rate of twist and the applied potential difference. As an example, a cantilevered transducer is studied.

Model-based control of mechatronic systems requires excellent knowledge about the physical behavior of each component. For several types of components of a system, e.g. mechanical or electrical ones, the dynamic behavior can be described by means of a mathematic model consisting of a set of differential equations, difference equations and/or algebraic constraint equations. The knowledge of a realistic mathematic model and its parameter values is essential to represent the behaviour of a mechatronic system. Frequently it is hard or impossible to obtain all required values of the model parameters from the producer, so an appropriate parameter estimation technique is required to compute missing parameters. A manifold of parameter identification techniques can be found in the literature, but their suitability depends on the mathematic model. Previous work dealt with the automatic assembly of mathematical models of serial and parallel robots with drives and controllers within the dynamic multibody simulation code HOTINT as fully-fledged mechatronic simulation. Several parameters of such robot models were identified successfully by our embedded algorithm. The present work proposes an improved version of the identification algorithm with higher performance. The quality of the identified parameter values and the computation effort are compared with another standard technique.

SUMMARY This paper is concerned with active control of torsional vibrations in laminated rods by piezoelectric shear sensors and actuators. A piezoelectric layer can be used as a sensor by utilizing the direct piezoelectric effect, measuring either the charge on short-circuited electrodes or the voltage on open electrodes. On the other hand, the converse piezoelectric effect enables actuation by applying an electric potential difference to the electrodes of a piezoelectric layer. The sensor and actuator equations are formulated in the framework of an extended Saint-Venant torsion theory considering additional cross-sectional warping due to piezoelectric eigenstrains. A solution of the shape control problem for torsional vibrations is presented, i.e. the necessary distribution of actuation strains in order to completely compensate vibrations caused by external excitations. For the case, in which the external excitations are not known exactly, a feedback control solution is presented using one piezoelectric layer as a sensor and a second one as an actuator. For the examples of a rectangular and a circular cross-section, the theoretical results are validated by three-dimensional finite element computations, showing a very good coincidence. Copyright © 2011 John Wiley & Sons, Ltd.

In this paper, the piezoelectric compensation of torsional vibrations in rods caused by external excitations is studied. As an illustrative example, a laminated rod containing piezoelectric shear actuators is assumed to be fixed at the one end, and the other end is subjected to a torsional couple; additionally, a distributed torsional couple per unit length is acting. In such a system, cross-sectional warping is known to be present. The consideration of piezoelectric eigenstrains requires an extension of Saint Venant’s theory of torsion, which is achieved by introducing an additional warping function. Using D’Alembert’s principle, the boundary value problems for Saint Venant’s warping function, the additional warping function and the torsional angle are obtained. From the latter boundary value problems, the distribution of piezoelectric actuation is derived in order to completely compensate the external excitations, i.e. an analytical solution of the corresponding shape control problem is obtained. Finally, the results are verified by means of three-dimensional finite element computations.

Dieser Beitrag beschreibt computergestutzte und messtechnische Untersuchungen, welche als eine wissenschaftliche Grundlage fur die Analyse und Entwicklung einer neuen Generation von Abkantautomaten zur Produktion von kompliziert geformten Profilen aus ebenen Blechteilen dienen. Es erfolgt einerseits eine Modellbildung unter Verwendung der Mehrkorperdynamik, um das Verhalten von starren Maschinenteilen zu modellieren, andererseits werden elastische Komponenten uber eine Diskretisierung mittels nichtlinearer Finite Elemente abgebildet. Fur die Beschreibung der Blechumformung werden Formulierungen der Plastizitatstheorie und der Kontaktmechanik herangezogen. Besonderer Wert wird auf die Verbindung dieser fortschrittlichen computergestutzten Methoden mit entsprechend konzipierten Messungen an gebauten Prototypen, sowie mit dem Expertenwissen gelegt. Methoden der Schwingungslehre und Festigkeitslehre werden interaktiv in den Untersuchungen und als Grundlage fur den Konstruktionsprozess angewendet. Im Rahmen von umfangreichen Messerien wurde eine ausgezeichnete Ubereinstimmung zwischen den Rechenergebnissen und den Versuchsergebnissen erzielt und daraus Verbesserungsvorschlage hinsichtlich des Entwurfs und des Betriebs abgeleitet. Das Studium von Detailproblemen im Rahmen von Modellverfeinerungen resultiert in neuen Erkenntnissen fur den Umformprozess.

In this paper, the application of piezoelectric vibration control in flexible multibody systems is studied and verified. Exemplarily, beam-type structures are considered that are subject to inertial and external forces. The equations of motion for three-dimensional flexible and torsional vibrations are presented considering the influence of piezoelectric actuation strains. In the framework of Bernoulli-Euler beam theory the shape control solution is derived, i.e. the distribution of actuation strains such that the flexible displacements are completely compensated. For the experimental verification, a laboratory model has been developed, in which the theoretical distribution of actuation strains is discretized by piezoelectric patches. A suitable control algorithm is implemented within a dSpace environment. Finally, the results are validated by numerical computations utilizing ABAQUS and HOTINT, and verified by experimental evaluation.

In many applications, nonlinear beams undergoing bending, axial and shear deformation are important structural elements. In the present paper, a shear deformable beam finite element is presented for such applications. Since displacements and displacement gradients are chosen as the nodal degrees of freedom, an equivalent displacement and rotation interpolation is retrieved. The definition of strain energy is based on Reissner’s nonlinear rod theory with special strain measures for axial strain, shear strain and bending strain. Furthermore, a thickness deformation is introduced by adding an according term to the virtual work of internal forces. This underlying formulation is extended for piezo-electric actuation. The obtained beam finite elements are applied to a two-link robot with two flexible arms with tip masses. Distributed and concentrated masses cause flexural vibrations, which are compensated by means of piezo-electric actuators attached to the arms. A numerical example of a highly flexible robot with piezo-electric actuation and feedforward control is presented to show the applicability of the finite element.

The present Lecture is concerned with vibrations of linear elastic solids and structures. Some part of the boundary of the structure is suffering a prescribed large rigid-body motion, while an imposed external traction is acting at the remaining part of the boundary, together with given body forces in the interior. Due to this combined loading, vibrations take place. The latter are assumed to remain small, such that the linear theory of elasticity can be applied. As an illustrative example for the type of problems in hand, we mention the flexible wing of an aircraft in flight. In this example, the rigid-body motion is defined through the motion of the comparatively stiff fuselage to which a part of the boundary of the wing is attached. The goal of the present paper is to derive a time-dependent distribution of actuating stresses produced by additional eigenstrains, such that the deformations produced by the imposed forces and the rigid-body motion are exactly compensated. This is called a shape control problem, or a deformation compensation problem. We show that the distribution of the actuating stresses for shape control must be equal to a quasi-static stress distribution that is in temporal equilibrium with the imposed forces and the inertia forces due to the rigid-body motion. Our solution thus explicitly reflects the non-uniqueness of the inverse problem under consideration. The present Lecture extends previous results by Irschik and Pichler (2001, 2004) for problems without rigid-body degrees of freedom. As a computational example, we present results for a rectangular domain in a state of plane strain under the action of a translatory support motion.

Active control of flexible vibrations by distributed piezoelectric actuators and sensors plays an increasing role in engineering, especially in light-weight structures. Exemplarily, in this contribution a rotating beam is studied which can be found in many practical applications, e.g. as robot arms or flexible manipulators in production processes. It has been intensively shown in the literature that it is possible to completely suppress the flexible vibrations by an appropriate distribution of piezoelectric actuation strains. In order to compensate the inertial forces in the considered rotating beam, a complex distribution is obtained, such that a practical realisation would be very extensive. To overcome the problem, a discrete approximation by piezoelectric patches is applied. In order to find an optimal configuration for an experimental setup, and to investigate several control strategies, a numerical simulation model has been implemented based on Bernoulli-Euler beam theory. The numerical results are verified by an experimental set-up, in which 48 piezoelectric patches have been attached on a beam with rectangular hollow cross-section. Each patch can be used either as an actuator or a sensor. Additionally, strain gauges can be used as sensors. For monitoring, acceleration sensors are used. The control system is implemented within a dSpace environment. The results show a significant reduction of the flexible vibrations. (© 2011 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)

Smart structures, which are equipped with piezoelectric actuators and sensors, and which involve automatic control, represent an important branch of Mechatronics. This paper gives a review over own research on smart structures, which has been performed during the last decade based on the principles of analogy and interdisciplinarity. The latter principles form a research strategy, which seems to be perfectly suited in order to answer the innovation request in Mechatronics, namely to decrease the time-lag between consecutive steps in the scientific development, and to keep fundamental and applied research in close co-operation. We start our report with a short excursion into the history of engineering sciences, in order to demonstrate this time-lag, where we use the history of elastic and piezoelastic plates as an example, and we discuss the notions of analogy and interdisciplinarity as means to systematically decrease the timelag. In our own work, we particularly have used an eigenstrain analogy as guideline. In the light of this analogy, various own works in the following fields are reviewed: Accurate electromechanically modeling; dynamic shape control by piezoelectric actuation and sensing; extension of dynamic shape control to closed loop control and active noise cancellation.