2nd International Conference Dynamic Simulation in Vehicle Engineering, May 2012, Engineering Center Steyr, St. Valentin.

Transcription

1 2nd International Conference Dynamic Simulation in Vehicle Engineering, May 2012, Engineering Center Steyr, St. Valentin 1 Smart Structures Hans Irschik, M. Krommer, M. Nader, J. Schöftner, Ch. Zehetner, Yu. Vetyukov The present paper gives a review on the research on smart structures based on piezoceramics, which has been performed at the Institute of Technical Mechanics of the Johannes Kepler University Linz, Austria, during the last twenty years. Particularly, own contributions in the following fields are reviewed: Accurate electromechanically coupled structural modeling; dynamic shape control by piezoelectric actuation and sensing; sensor networks for measuring structural behaviour and damage. Support of research in the framework of the COMET-K2 Austrian Center of Competence in Mechatronics is gratefully acknowledged. hans.irschik@jku.at

2 A novel fundamental result of eigenstrain-theory (1) 2 Edelstein, W. and Gurtin, M. E. Uniqueness theorems in the linear dynamic theory of anisotropic viscoelastic solids. Arch. Rat. Mech. Anal, 1964 Irschik, H. and Pichler, U.: An extension of Neumann's method for shape control of force-induced elastic vibrations by eigenstrains. International Journal of Solids and Structures, Displacement tracking problem: Assume that the initial past history, the geometrical and mech. parameters, the body forces and the boundary data are known. Seek a transient field of tensorial actuator-stresses, such that the displacement u satisfies the following relation u = z everywhere in the viscoelastic body and for all times, where z is a given, sufficiently smooth diesplacement field ( displacement field, which shall be tracked ). Irschik, H., Krommer, M.: American Soc. Mechanical Eng., Paper No. DETC , 2005

3 A novel fundamental result of eigenstrain-theory (2) 3 Consistency: a) Initial past histories of u and z are equal. b) The kinematic b.cs. of u and z are equal. Solution: An eigenstrain-actuation represents a solution of the dynamic displacement tracking problem, if the actuator tensor satisfies the following equilibrium condition at all times and everywhere: Div S A + b * = 0!B s : S A n = s * with b * = b! z s * = s (G 0 [sym!z] + + Div (G 0 [sym "z] + G(s) [sym!z (t s)] ds) 0 " 0 " G(s) [sym!z (t s)] ds) n Irschik, H., Krommer, M.: American Soc. Mechanical Eng., Paper No. DETC , 2005

4 Numerical example for Shape Control (1) 4 Numerical example for Shape Control: Zero-Tracking: z = 0 Plane strain Computation of quasi-static stress by ABAQUS (525 plane strain elements of type CPE4R ) Thermal Actuation (anisotropic heat conduction) H. Irschik, U. Pichler: Dynamic Shape Control of Solids and Structures by Thermal Expansion Strains (Plenary Lecture, Fourth International Congress on Thermal Stresses, Japan, 2001) Journal of Thermal Stresses 2002

5 Numerical example for Shape Control (2) 5 Frequency response Jump response Collocated Actuators and Sensors ( Natural output ): M. Krommer, H. Irschik: Sensor and actuator design for displacement control of continuous systems, Smart Structures and Systems, 2007 Results: H. Irschik, U. Pichler: J. Thermal Stresses, 2002

6 Piezoelectric Sensors and Actuators (1) 6 Piezoelectricity:...The generation of electric charge in a substance by a mechanical stress that changes its shape, and a proportional change in the shape of a substance when voltage is applied. Encyclopædia Britannica Actuators:... change in the shape of a substance when voltage is applied. Sensors:... the generation of electric charge in a substance by a mechanical stress Li.t: H. Jaffe: Piezoelectricity, Encyclopædia Britannica, 1972

7 Piezoelectric Sensors and Actuators (2) 7 The young brothers Jacques and Pierre Curie announced their discovery of the piezoelectric effect to the French Academy of Science on 2 August Yet, the use of the phenomenon outside the laboratory began only 35 years after its discovery during the first world war. Technological applications were not a main concern in the early study of piezoelectricity. S. Katzir A modern application: Piezo-Injectors Piezo-Stack: Deutscher Zukunftspreis des Bundespräsidenten 2005 (seitens Siemens: Prof. H. Meixner): "Piezo-Injektoren: Neue Technik für saubere und sparsame Diesel- und Benzinmotoren" Einspritzdüse: Lit.: S. Katzir: The Discovery of the Piezoelectric Effect, Arch. History of Exact Sciences, 2003

8 Piezoelectric Sensors and Actuators (3) 8 Pizoelectric Elements for integration in vibrating mechanical structures: Piezoelectric fiber (30 µm ) Quelle für Keramik: Invent (DLR); für Fasermodule: Fraunhofer Institut für Silikatforschung, Würzburg

9 Compensation of cantilever vibrations (1): 9 Additional actuators produce eigenstrains: Thermal, Piezoelectric, Magnetostrictive, Active tendons... Galileo Galilei: Discorsi e demostrazioni matematiche, intorno a due nuovo scienze, Leyden 1638 Galileos cantilever: First systematic study of simple structural elements Shape Control seeks for actuator distributions (shaped actuators), which can compensate strains and vibrations due to given forces or rigid body motions, if possible, completely. Abb.: I. Szabo, Geschichte der mechanischen Prinzipien, Bikhäuser 1987

10 Compensation of cantilever vibrations (2): 10 q T =!µ u(!! t ) u(t)! x " S( x ) = $ 1# % & L ' 2 Compute quasi-static parts of mechanical stresses (bending moments!) due to inertial forces. This yields theoretical piezoactuaor distribution as a quadratic function in space. Irschik, H., Krommer, M., Pichler U.: Int. J. Appl. Electromagnetics Mechanics, 2003

11 Compensation of cantilever vibrations (3): 11 Realization of piezo-actuation: PZT (Blei-Zirkonat-Titanat) on aluminium-substrate Continuous distribution: Piezoelectric Patches:

12 Compensation of cantilever vibrations (4): 12 Distribution of piezoelectric patches: Distribution of patches such that auxiliary loading of conjungate beam forms a region-wise selfequilibrating system (Mohr s Analogy). Nader, M., von Garssen, H.-G., Irschik, H., in Proc. SMART'03, Polish Academy of Sciences 2004

13 Compensation of cantilever vibrations (4): 13 3D-Finite-Element computation as a first validation: Piezo-Actuation: Distribution according beam-theory FE-computation: coupled, threedimensional (3D) solid elements Diss. M. Nader, JKU Linz 2007, Trauner Verl. Univ. 2008

14 Compensation of cantilever vibrations (5): 14 Realization of concepts of automatic control: Uncertainties: mech. system-parameters electr. system-parameters time-evolution of excitation Feedforward: Measurement of disturbance; identification of plant; Feedback: disturbancecontrol with loop-shaping Diss. M. Nader, JKU Linz 2007, Trauner Verl. Univ. 2008

15 Compensation of cantilever vibrations (6): 15 Experimental validation (Laboratory): Support-excitation by Piezo-Stack Vibration compensation by Piezo-Patches:

16 Compensation of cantilever vibrations (7): 16

17 Compensation of cantilever vibrations (8): 17 Excitation by band-limited noise; compensation in a frequency band including first and second eigenfrequency Harmonic, resonant excitation in first eigenfrequency; time-domain M. Nader: Compensation of Vibrations in Smart Structures: Shape Control, Experimental Realization and Feedback Control, Dissertation, JKU Linz 2007, Trauner Verlag Universität, Reihe C, Technik u. Naturwissenschaften, Vol. 54, 2008

18 Vibration-compensation in thin shells with a complex shape (Funnel of a MRT) (1) 18 Problem: Vibrations of the funnel: Heavy noise-load for patients and personal (above 80 db); passive damping not sufficient.

19 Vibration-compensation in thin shells with a complex shape (2) 19 Application of strategy developed for beams and plates to the complex funnel:

20 Vibration-compensation in thin shells with a complex shape (3) 20 Computation of quasi- static stresses (here: 1. invariant of stress-tensor) due to inertial forces by FE > Theoretical actuator-distribution > Discretization by piezo-patches Lit. on patch-placement: H. Irschik et al., in Proc. US-Europe Workshop Sensors Smart Structures Technology, London, J. Wiley 2003

21 Active noise-chancellation in ventilation ducts (1) 21 Goal: Automatic reduction of the noise produced by ventilation devices Straight ducts: Sew-Eurodrive Stiftung Studienpreis 2006 (TU-Karlsruhe): Master- Thesis D. Huber, JKU-Linz, 2006

22 Active noise-chancellation in ventilation ducts (2) 22 Example: Aktive Active noise-chancellation in a heat ventilation air conditioning device of a car: Piezo-Actuators for generating anti-noise by exciting vibrations in the light-weighted solid shell of the duct

23 Work in the last years (exemplary): Actuator and Sensor-Networks for Displacement-Tracking 23 Example: Frame (upper floor horizontally movable) with patch-network; tracking of second Eigenmode of clamped-clamped beam M. Krommer, H. Irschik, M. Zellhofer: Design of Actuator Networks for Dynamic Displacement Tracking of Beams, Mech. Advanced Materials Structures, 2008

24 A general concept for strain-type sensors (1) H. Irschik, M. Krommer, Y. Vetyukov, On the Use of Piezoelectric Sensors in Structural Mechanics: Some Novel Strategies., Sensors 10, 2010

25 A general concept for strain-type sensors (2)

26 A general concept for strain-type sensors (3)

27 Some experimental results

28 Sensor network design (1) M. Krommer, M. Zellhofer, K.-H. Heilbrunner: Strain-type Sensor Networks for Structural Monitoring of Beam-type Structures. Journal of Intelligent Material Systems and Structures, 20, 2009.

29 Sensor network design (2)

30 Sensor network design (3)

31 Sensor network design (4)

32 Sensor network design (5)

33 Sensor network design (6) Thank you for your kind attention!