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In recent years, there has been considerable interest in the design and development of smart structural systems. The field of smart structures is one of several areas of engineering where knowledge, which has been heretofore compartmentalized in several different engineering disciplines, must be integrated into a single functional unit because the application crosses disciplinary boundaries. A successful understanding of the concept of a smart structure depends on an in-depth appreciation of the fields of smart materials, mechanics of materials, mechanical vibrations, structural analysis, and control-structure interactions. One must also understand how system modeling and control design methodologies interact when applied to the design of structural systems that will contain built-in control, sensory, and diagnostic elements. The vast potential of smart structures has stimulated the engineering community in the development of new products and systems to be used in such applications as automobiles, aircraft, space-based structures, earthquake-resistant buildings, and industrial machinery. The primary objective of our effort is to integrate research results with curriculum development for the benefit of students in civil, electrical, mechanical, aerospace engineering, and engineering mechanics. The curriculum development objectives are (i) the introduction of emerging technologies into the senior undergraduate and graduate curriculum, (ii) the development of multidisciplinary educational experiences, and (iii) the enhancement of design components of curriculum and capstone design projects. We have developed a two-course sequence integrated with a multidisciplinary laboratory in smart structures. The titles of the courses are "Introduction to Smart Structures" and "Intelligent Control of Smart Structures." These two courses were team taught with one instructor each from the departments of electrical engineering and mechanical engineering. We have also developed a set of laboratory experiments and team design projects for these courses. We wish to share our experience in teaching these multidisciplinary courses in smart structures.
Active vibration control of structural systems has several applications in areas such as space, aircraft, automotive and civil engineering structures. These structures typically have several closely-spaced lightly-damped vibration modes. The structures that incorporate smart materials for sensors and actuators, structural identification techniques to obtain mathematical models, and active control methodologies to improve the vibrational response are referred to as smart structures. These structures have the ability to beneficially respond to internal and external simulations through the sensing, controlling and actuating of the systems response. The design and implementation of smart structures necessitate the integration of (i) smart sensors and actuators, (ii) microelectronics, (iii) structural modeling and design, (iv) intelligent control techniques, and (v) fabrication techniques. The field of smart structures is one of several areas of engineering where knowledge is distributed in several engineering disciplines and requires integration into a single functional unit. The vast potential of smart structures has stimulated the engineering community in the development of new products and systems to be used in such applications as automobiles, aircraft, space-based structures, earthquake resistant buildings, and industrial machinery. The University of Missouri-Rolla has been quite successful in recent years in obtaining the support of the National Science Foundation and the Army Research Office for conducting research on smart structures. One of the objectives of our project was to integrate research results with curriculum development in the cross-disciplinary area of smart structures for the benefit of students in electrical, mechanical, aerospace, civil engineering and engineering mechanics.
In the fall of 1993, the National Science Foundation awarded a grant to the University of Missouri-Rolla to develop a two-course sequence in the smart structures area. We have developed courses entitled "Introduction to smart structures" and "Intelligent Control of Smart Structures" under this program. We have also developed a set of multidisciplinary laboratory experiments and team design projects for these courses. These courses were team taught with one instructor each from the departments of electrical engineering and mechanical and aerospace engineering. This paper provide a summary of the curriculum development aspects of our project.
The curriculum development objectives were (i) introduction of smart structures concepts to senior undergraduate and graduate students, (ii) development of interdisciplinary educational experiences for students working in teams involving students from different disciplines, and (iii) the enhancement of the design component of curriculum and capstone design projects. We developed a two-course sequence integrated with a multidisciplinary laboratory in smart structures. These course were jointly taught with one instructor from the Department of Electrical Engineering and one from the Department of Mechanical and Aerospace Engineering. So far we have taught these courses two times and gained valuable experience in teaching multidisciplinary courses.
The primary objective of the first course was to integrate standard undergraduate topics in mechanics and linear systems with research results to provide the necessary introduction to the basic smart structures concepts. The first course was entitled "Introduction to Smart Structures" and was open to both senior undergraduate and graduate students. The syllabus for the first course is given below:
(i) Overview of Smart Structures (1 week)
General introduction to the types of smart structures, commonly used actuators and sensors. This is a qualitative presentation that includes an introduction to the laboratory.
(ii) Remedial Work (3 weeks)
After the first week, the students were divided into two groups for remedial work. The EE students were given a brief survey of such ME topics as mechanics of materials, finite element methods, and introduction to mechanical vibrations. The remedial work for the students whose background was not in electrical engineering consisted of a review of Fourier transforms, linear systems, controller design methods, basics of sampling selection and data acquisition systems.
(iii) Sensors and Actuators (3 weeks)
Shape memory alloys, piezoelectric (PZT), polyvinylidene fluoride (PVDF) film, LVDT's, laser probes for velocity and surface deformation measurements, and fiber optic sensors.
(iv) Advanced Topics in Mechanical Vibrations (2 weeks)
Vibration of beams and plates, finite element models, state variable formulation of multidegree-of-freedom systems. A procedure was then formulated showing how to include the effects of a PZT actuators in the finite element model of beams and plates.
(v) Composite Structures (2 weeks)
Basic introduction to the terminology and techniques of manufacture of composites, discussion of mathematical models of composites, discussion of mathematical models of composites with a comparison to the corresponding mathematics of plates and beams.
(vi) System Identification Methods (2 weeks)
Analysis of the sampling operation and frequency spectrum of the sample signal. Signal energy and spectral density, direct FFT methods for system identification methods. Introduction to eigensystem realization algorithms for structural identification.
(vii) Control of Smart Structures (2 weeks)
Use of standard control design techniques and standard MATLAB control design software using position and velocity feedback, various control compensation strategies, LQR and LQG/LTR designs. Emphasis is on the comparison of the various designs and also on the effects of errors in modeling and sensor placement.
The second course, entitled "Control of Smart Structures," was taught following the first course. The objective of this course was to introduce the concepts for the development of real-time controllers for lightly-damped smart structural systems. This course was also open to graduate students from the departments of electrical, civil, and mechanical and aerospace engineering and engineering mechanics. The syllabus for this course is as follows:
(i) Introduction to Smart Sensors and Actuators (2 weeks)
Review of sensors and actuators made of piezoelectric materials, electrostrictive and magnetostrictive materials, electro-rheological fluids, shape memory alloys, and fiber optic sensors.
(ii) Modeling of Smart Structural Systems (4 weeks)
Modeling of structures embedded or surface mounted with piezoelectric and shape memory alloy materials and finite element modeling of composite structures. Structural identification methods. Modeling of constrained layered damping systems.
(iii) Active Vibration Control Systems (2 weeks)
Equation of motion and modal analysis, mode controllability and observability, independent modal space control and optimal quadratic regulator problems.
(iv) Adaptive Control Systems (2 weeks)
Introduction, adaptive control based on identification, model reference adaptive control, selftuning regulators, gain scheduling methods, and applications to lightly damped smart structural systems.
(v) Neural Networks for Smart Structures (2 weeks)
Review of basic concepts of neural networks, learning algorithms, adaptive control using neural networks and neural network based control algorithms.
(vi) Case Studies (2 weeks)
Detailed case studies incorporating all aspects of modeling and control design strategies.
The laboratory experiments were designed primarily to enhance the student's understanding of the theoretical concepts involved rather than to train them in a particular laboratory procedure or technique. The experiments were designed to be conducted by teams that had at least one electrical and one mechanical engineering student as a member. The idea was that the electrical engineering student would be more familiar with the use of such standard laboratory equipment as digital voltmeters, signal generators, oscilloscopes, and signal analyzers, while the mechanical engineering students would be more familiar with the mechanical vibrations, finite element modeling, and measurement of stress and strain in structural systems. They were expected to submit a team report on each of the experiments. The list of the experiments is given below:
First Course: "Introduction to Smart Structures"
Second Course "Control of Smart Structures "
One of the objectives of our project was to provide capstone design projects to senior undergraduate students. We developed a list of multidisciplinary design topics in the smart structures area and encouraged the students to work on some of these topics. A representative list of the topics for capstone design projects is given below:
The general reaction of the students was very positive. They enjoyed the experimental work and liked the multidisciplinary nature of the materials. The student comments are summarized as follows:
The availability of advanced undergraduate and graduate level courses provided an excellent opportunity for training future scientists and engineers in the multidisciplinary area of smart structures. These course provided an opportunity to expand the course offerings into the multidisciplinary environment. They also helped us to recruit students to conduct research in the area of smart structures. The interactions among the faculty and students from the various participating departments helped us to enhance our research capabilities in this area. The availability of experimental facilities in the smart structures area provided hands-on experience to the students in the multidisciplinary set up. These facilities provided a unique opportunity to demonstrate the capabilities and limitations of the smart structural systems. One of the criticisms of the students was the nonavailability of good class notes and text books in this area. We developed detailed class notes and distributed them to the students. The faculty members involved in the course and laboratory development also enjoyed the multidisciplinary nature of the course material and student participation.
This research is supported by a grant from the National Science Foundation under Combined Research and Curriculum Development program (Grant #EEC-9315199). The support and technical interests of Drs. Win Aung and Mary Poats are gratefully acknowledged.
1. V. Rao, "Combined Research-Curriculurn Development in Smart Structures," NSF Workshop on 'Project Impact: Disseminating Innovation in Undergraduate Education.' Washington, D.C., May 1994.
2. L.R. Koval, V. Rao and F. Kern, "Combined Research-Curriculum Development in Smart Structures," Fifth International Conference on Adaptive Structures, Sendai, Japan, December 1994.
3. V. Rao and R. Damle, "Identification and Control of Smart Structures Using Neural Networks: A Survey," Proceedings of the IEEE 33rd Conference on Decision and Control, Lake Buena Vista, FL, December 1994, pp. 91-96.
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5. M.L. Hill, P. Chrissos, L.R. Koval, V.S. Rao and F. Kern, "Control of Sound Transmission into a Closed Cavity Using Smart Structures," Proceedings of the l995 North American Conference on Smart Structures and Materials, San Diego, CA, Feb.-March 1995.
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