Adaptronics 2011 Lecture 1

Fundamentals of ActiveStructural Control

Prof. Dr.-Ing. Tamara Nestorovićwww.rub.de/mas

Adaptronics

Prof. Dr.-Ing. Tamara Nestorović

Ruhr-University Bochum, Mechanics of Adaptive Systems

Building IA, Room 01/128

E-mail: [email protected]; www.rub.de/mas

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Recommended literature and links• Lecture Notes – Course slides (final version will be updated in Blackboard in the end of

the course)

• Matlab online Helpdesk and Tutorialshttp://www.mathworks.com/academia/student_center/tutorials/http://www.mathworks.com/academia/student_center/tutorials/mltutorial_launchpad.html#http://www.mathworks.com/academia/student_center/tutorials/sltutorial_launchpad.htmlhttp://www.mathworks.com/academia/student_center/tutorials/controls-tutorial-launchpad.htmlhttp://www.mathworks.com/access/helpdesk/help/helpdesk.html

• Fuller C. R., Elliott S. J., Nelson P. A.: Active Control of Vibration, Academic Press Ltd, London, 1996

• Franklin G. F., Powell J. D., Emami-Naeini A.: Feedback Control of Dynamic Systems, second edition, Addison-Wesley Publishing Company, 1991

• Franklin G. F., Powell J. D., Workman M. L.: Digital Control of Dynamic Systems, third edition, Addison-Wesley Longman, Inc., 1998

• Richard J. Vaccaro: Digital Control, A State-Space Approach, McGraw-Hill Inc., 1995

• Preumont A.: Vibration Control of Active Structures: An Introduction, Kluwer Academic Publishers, Dordrecht, Boston, London, 1997



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Active Structural Control – Motivation

Motivation for development of smart structures andactive structural control:

Growing interest and application possibilities in a broad field of engineering, such as automotive industry, civil engineering,aero-space industry, robotics, mechatronics, etc.

Overall design of smart systems(modeling, control, simulation, experimental testing, implementation)

Possibility for investigation in early development phaseswhen real system or a prototype is not available

Cost reduction (material, space, energy savings) through optimization



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Active Structural Control – Tasks

Smart structural control challenges and tasks:

- to achieve desired behavior and stabile smart structures in a noisyenvironment or in the presence of excitations

- a need to design a robust and stable control systemusing minimal prior knowledge about the controlled plant

- solution of different optimization problems,e.g. vibration suppression and noise control:

- active vibration control AVC,- active noise control ANC,- active structural acoustic control ASAC

- design and application of control laws for the vibration and noise suppression of piezoelectric smart structures



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Smart Structures and Adaptronics - Terms

Terms

Several terms are used to denote structures and systems with ability to adapt themselves to changing environmental conditions.

Most often used terms

- English terminology:smart structures, intelligent structures, adaptive structures,active structures;

- German terminology: adaptronics, adaptronic systems (Adaptronik)



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Smart Structures and Adaptronics - Definitions

Definitions

Definition suggested by the Fraunhofer SocietySource: http://www.fraunhofer.de/fhg/research/index/perspektiven_4.jsp

Under the term smart structures or adaptronics one can understand structures which enable a direct actively controlled adaptation of mechanical properties in accordance to changing environmental operating conditions through integrated functionalities within the structure itself.



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Smart Structures and Adaptronics - DefinitionsDefinition of DLR – Deutsches Zentrum für Luft- und Raumfahrt (Leitprojekt Adaptronik),Source: http://www.mechatronik-portal.de/mechatronik_definition.php

Adaptronics stands for a field of technology which provides a new class of so-called intelligent structures. This concept imposes the development of adaptive systems, which are able to adapt to different operating conditions through autonomous self-regulating mechanisms. The premise for that is an optimal integration of sensors and actuators based on new active functional materials (like e.g. piezoelectric fibers or films) as well as of adaptive controllers. These active materials play at the same time the carrying or supporting role of mechanical structure, as well as the the actuating/sensing role, and therefore they are multi-functional.



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Structure of smart systems

Comparison of different structural systems

noiseless vibrationinstable

Excitations

adaptive

- vibration elimination- stable- lightweight- integrated controller

Adaptive controller

Excitations

adaptive

Goal:- vibration elimination- stable- lightweight- external controller

Passivestructure

Excitations

Passivestructure

Controller

SensorsActuators active

Excitations

less noiseless vibrationstable, heavy



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Examples of Adaptive Structures and SystemsICE bogie



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+

+

+

Hierarchy of Smart Structures and Systems



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Development of active structures – goals and tasks

GoalsIncreasing the efficiency, safety and comfort by: active vibration suppression active noise attenuation active shape control active position control health monitoring noise reduction

Development tasks structure conform integrated

actuator / sensor systems

discrete real-time controllers

up-to-date design andoptimization methods



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What are we studying in the field of active vibration and noise control?









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Multi-functional materials:

• Piezo ceramics

• Shape memory alloys (SMA)

• Electrorheological fluids (ERF)










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Controller design:

• Optimal LQ control(SISO and MIMO control systems)

• LQ controller with additionaldynamics

• Adaptive control (MRAC)










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• Modeling of adaptive structures: FE approach Experimental identification

• Optimal placement of actuators and sensors



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actuators

sensorsactuatorsdisturbances

-101030507090

110

0 25 50 75 100

Frequency [Hz]

Ampl

itude

[dB

]controlled uncontrolled

Examples of active structural control – automotive



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Examples of active structural control – medical solutions

actuators

sen sors

d isturbance

20

40

60

80

100

120

0 20 40 60 80Frequency [Hz]

Ampli

tude [

dB]

controlled uncontrolled

Piezoelectric films cut down noise generated by the MRI scanner



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Example:Vibration suppression using control techniques

Example of an actively controlled piezoelectric beam structure

Basic elements of an active structural system



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Classification of control lawsModel-based control: - FE-Model

- Model identificationAdaptive controllers: - Model Reference Adaptive Control (MRAC)

- Self-tuning regulators (STR)Classification of model-based controller design techniques

Model-based Controller

Linear Time-Invariant Controller (LTI)

Output FeedbackState Feedback

DiscreteContinuousDigital Tracking

Systems

LQR-ControllerPole Placement

LQR-ControllerPole Placement

Disturbance RejectionReference Model Design

Disturbance Cancellation

Nonlinear Controller PID Control

Documents

Adaptronics 2011 Lecture 1