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A consortium of researchers from Harvard University ( Roger Brockett , Howard Stone ), University of Maryland ( P. S. Krishnaprasad , Stuart Antman, John Baras ) and Boston University ( John Baillieul , Tom Bifano ) has been selected as the recepient of a new award for research under the Multidisciplinary University Research Initiatives (MURI 97) Program of the Army Research Office, on the topic of DESIGN AND CONTROL OF SMART STRUCTURES . The award to the consortium is at the level of $1 million per year for 3 years with the option of an additional 2 years. The start date is May 1, 1997. A kick-off meeting for the Center will be held at Harvard University on August 18 and 19. The effort, directed by Prof. Roger Brockett will include research in: nonlinear modeling, simulation and control of magnetostrictive materials (e.g Terfenol), electrostrictive materials (e.g. PMN), and other materials used in smart actuators; problems of control of deformable bodies with embedded smart materials using electromagnetic fields; communication and networking considerations in the integrated design of smart composites; computation and design tools for smart actuators and sensors; fluid-structure interactions; and design, fabrication and testing of arrays of MEMS structures (arrays of microvalves and electrostatically deformable structures). Of central interest to the research team are issues of coupling elastomechanics and fluid mechanics with electrophysical influences such as piezo-electric effects, magnetostrictive effects, and electrocapillary forces. The team will explore the highly nonlinear equations governing the relevant phenomena and develop control-oriented approaches to exploit and manipulate these effects in engineering applications. The experimental efforts on fluid-related problems will include studies of MEMS for control of flow over airfoils, fabrication of parallel arrays of microvalves for flow control on small scales and the solution of prototypical problems.

Resume of Tasks

1.Research on Very Small-Scale Servo Systems

Sensing and actuation devices on length scales of millimeter and smaller will be considered in large arrays, and communication and hierarchical control issues will be treated. Nonlinear problems in MEMS devices such as snap-through instabilities, hysteresis, thermal conditioning etc. will be attacked from the viewpoint of local control.

2. Modeling for Sensing and Control:

Diverse fundamental physical models of magnetoelastic and piezoelastic materials will be treated from rigorous, modern, mathematical viewpoints. Methods for reduction of nonlinear partial differential equations into low order ordinary differential equations capturing the essential physics will be developed. Methods for stability analysis, and feedback stabilization will be developed. Problems involving frequency dependent hysteresis will be attacked from rigorous physical understanding coupled with experimental characterization. The tools created here will be useful in the design of millimeter scale and larger scale actuators and sensors.

3. Systems of Embedded Micro-actuators for the Control of Flow over Airfoils and in Arrays of Microvalves

Models of fluid flow over lifting surfaces will be used to capture sufficient detail to control flow separation. Hybrid control (combining gross pitch motions with coordinated motions of microactuators) strategies will be developed. A modular ducted flow experiment will serve as a testbed. The needed MEMS sensor/actuator arrays will be fabricated using the Smart-MUMPS process at MCNC. This will enable integration of control electronics with actuators.

4. Issues in the Control of Fluids on Small Length Scales

Mechanisms of fluid transport based on (i) direct boundary actuation, (ii) thermal effects exploiting bubbles, (iii) electro-osmotic flows, (iv) streaming based on rectification of oscillatory flows, (v) electrocapillarity, and (vi) electro/magneto-rheological effects will be investigated. Fundamental mathematical analysis will be carried out.

5. The Communications Theory of Very Large-Scale Device Networks

Quantized actuator concepts needing low local bandwidth will be investigated in the formation of effective sensor-actuator networks. Tradeoffs between network bandwidth and control performance will be analyzed.

6. Numerical Methods and CAD

Numerical integrators for geometrically nonlinear models will be developed (especially for magnetostrictive materials). Tools for systematic model reduction will be developed and implemented in software based on scripting languages. Field visualization algorithms and tools will be developed, to support actuator design and optimization.

Education and Training

The Center will foster the advanced research training of pre-doctoral and post-doctoral researchers through inter-university collaboration, collaboration with industry partners and with national labs.

Points of Contact

The Center Director is Roger W. Brockett (An Wang Professor of Electrical Engineering and Computer Science at Harvard University). Co-Directors are P.S. Krishnaprasad (Professor of Electrical Engineering and Institute for Systems Research at the University of Maryland, College Park), and John Baillieul (Professor of Aerospace and Mechanical Engineering and of Manufacturing Engineering at Boston University). Contact information: Brockett (email:, brockett@hrl.harvard.edu tel: 617-495-3922); Krishnaprasad (email: krishna@isr.umd,edu , tel: 301-405-6843); Baillieul (email: johnb@enga.bu.edu , tel: 617-353-9848).
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