The second phase of the synthesis and processing of intelligent cost effective structures (SPICES II) program sought to identify high payoff areas for both naval and aerospace military systems and to evaluate military systems and to evaluate the benefits of smart materials incorporation based on their ability to redefine the mission scenario of the candidate platforms in their respective theaters of operation. The SPICES II consortium, consisting of The Boeing Company, Electric Boat Corporation, United Technologies Research Center, and Pennsylvania State University, surveyed the state-of-the-art in smart structures and evaluated potential applications to military aircraft, marine and propulsion systems components and missions. Eleven baseline platforms comprising a wide variety of missions were chosen for evaluation. Each platform was examined in its field of operation for areas which can be improved using smart materials insertion. Over 250 smart materials applications were proposed to enhance the platforms. The applications were examined and, when possible, quantitatively analyzed for their effect on mission performance. The applications were then ranked for payoff, risk, and time frame for development and demonstration. Details of the efforts made in the SPICES II program pertaining to smart structure applications on military and transport aircraft will be presented. A brief discussion of the core technologies will be followed by presentation of the criteria used in ranking each application. Thereafter, a selection of the higher ranking proposed concepts are presented in detail.

A comparison of active smart structure - piezoelectric control system and aerodynamic active systems for vibration alleviation and elastic mode damping of a military aircraft structure is presented. The vibration alleviation systems which are operative at flight in turbulence or during maneuvers at high incidence corresponding to severe buffeting conditions are under investigation by DASA as a part of research study on advanced aircraft structures. The active systems for elastic mode damping are designed as digital systems to provide vibration alleviation and have an interface to the flight control system (FCS) or are directly part of the FCS. The sensor concept of all different systems is the same as the sensor concept used for the FCS with the corresponding benefits of redundancy and safety. The design of systems and the comparisons of system properties are based on open and closed loop response calculations, performed with the dynamic model of the total aircraft including coupling of flight mechanics, structural dynamics, FCS dynamics and hydraulic actuator or piezo-actuator dynamics. Aerodynamic systems, like active foreplane and flap concepts, rudder and auxiliary rudder concepts, and piezoelectric systems, like piezo interface at the interconnection fin to rear fuselage and integrated piezo concepts are compared. Besides the essential effects on flexible aircraft mode stability and vibration alleviation factors system complexity and safety aspects are described.

Buffeting is an aeroelastic phenomenon that plagues high performance aircraft, especially those with twin vertical tails. Unsteady cortices emanate form wing/fuselage leading edge extensions when these aircraft maneuver at high angles of attack. These aircraft are designed such that the vortices shed while maneuvering at high angels of attack and improve the lift-to-drag ratio of the aircraft. With proper placement and sizing of the vertical tails, this improvement may be maintained without adverse effects to the tails. However, there are tail locations and angels of attack where these vortices burst and immerse the vertical tails in their wake inducing severe structural vibrations. The resulting buffet loads and severe vertical tail response because an airframe life and maintenance concern as life cycle costs increased. Several passive methods have been investigated to reduce the buffeting of these vertical tails with limited success. As demonstrated through analyses, wind-tunnel investigations, and full-scale ground tests, active control system offer a promising solution to alleviate buffet induced strain and increase the fatigue life of vertical tails. A collaborative research project including the US, Canada, and Australia is in place to demonstrate active buffet load alleviation systems on military aircraft. The present paper provides details on this collaborative project and other research efforts to reduce the buffeting response of vertical tails in fighter aircraft.

Different concepts to damp structural vibrations of the vertical tail of fighter aircraft are reported. The various requirements for a vertical tail bias an integrated approach for the design. Several active vibrations suppression concepts had been investigated during the preparatory phase of a research program shared by Daimler-Benz Aerospace Military Aircraft (Dasa), Daimler-Benz Forschung (DBF) and Deutsche Forschungsandstalt fuer Luftund Raumfahrt (DLR). Now in the main phase of the programme, four concepts were finally chosen: two concepts with aerodynamic control surfaces and two concepts with piezoelectric components. One piezo concept approach will be described rigorously, the other concepts are briefly addressed. In the Dasa concept, thin surface piezo actuators are set out carefully to flatten the dynamic portion of the combined static and dynamic maximum bending moment loading case directly in the shell structure. The second piezo concept by DLR involves pre-loaded lead zirconate titanate (PZT)-block actuators at host structure fixtures. To this end a research apparatus was designed and built as a full scale simplified fin box with carbon fiber reinformed plastic skins and an aluminium stringer-rib substructure restrained by relevant aircraft fixtures. It constitutes a benchmark 3D-structural impedance. The engineering design incorporates 7kg of PZT surface actuators. The structural system then should be excited to more than 15mm tip displacement amplitude. This prepares the final step to total A/C integration. Typical analysis methods using cyclic thermal analogies adapted to induced load levels are compared. Commercial approaches leading onto basic state space model interpretation wrt. actuator sizing and positioning, structural integrity constraints, FE-validation and testing are described. Both piezoelectric strategies are aimed at straight open-loop performance related to concept weight penalty and input electric power. The required actuators, power and integration are then enhanced to specification standards. An adapted qualification program plan is used to improve analytical read across, specifications, manufacturing decisions, handling requirements. The next research goals are outlined.

The adaptive neural control of aeroelastic response (ANCAR) and the affordable loads and dynamics independent research and development (IRAD) programs at the Boeing Company jointly examined using neural network based active control technology for alleviating undesirable vibration and aeroelastic response in a scale model aircraft vertical tail. The potential benefits of adaptive control includes reducing aeroelastic response associated with buffet and atmospheric turbulence, increasing flutter margins, and reducing response associated with nonlinear phenomenon like limit cycle oscillations. By reducing vibration levels and thus loads, aircraft structures can have lower acquisition cost, reduced maintenance, and extended lifetimes. Wind tunnel tests were undertaken on a rigid 15% scale aircraft in Boeing's mini-speed wind tunnel, which is used for testing at very low air speeds up to 80 mph. The model included a dynamically scaled flexible fail consisting of an aluminum spar with balsa wood cross sections with a hydraulically powered rudder. Neural predictive control was used to actuate the vertical tail rudder in response to strain gauge feedback to alleviate buffeting effects. First mode RMS strain reduction of 50% was achieved. The neural predictive control system was developed and implemented by the Boeing Company to provide an intelligent, adaptive control architecture for smart structures applications with automated synthesis, self-optimization, real-time adaptation, nonlinear control, and fault tolerance capabilities. It is designed to solve complex control problems though a process of automated synthesis, eliminating costly control design and surpassing it in many instances by accounting for real world non-linearities.

Civil transport airplanes fly with fixed geometry wings optimized only for one design point described by altitude, Mach number and airplane weight. These parameters vary continuously during flight, to which means the wing geometry seldom is optimal. According to aerodynamic investigations a chordwide variation of the wing camber leads to improvements in operational flexibility, buffet boundaries and performance resulting in reduction of fuel consumption. A spanwise differential camber variation allows to gain control over spanwise lift distributions reducing wing root bending moments. This paper describes the design of flexible Fowler flaps for an adaptive wing to be used in civil transport aircraft that allows both a chordwise as well as spanwise differential camber variation during flight. Since both lower and upper skins are flexed by active ribs, the camber variation is achieved with a smooth contour and without any additional gaps.

Acoustic fatigue is due to very high intensity excitation as a result of pressure waves caused by either engine/or aerodynamic effects. Currently a large portion of the F/A-18 fleet has suffered from acoustic fatigue cracking in skin panel on the lower external surface of the inlet nacelle. There has been a long history of cracking in this region, which is attributed to fatigue caused by acoustic excitation of the panel during the operation of the aircraft. Efforts to alleviate these fatigue crack growth with traditional boron/epoxy patches was not successful. This paper seek to select a set of damping material suitable for the reinforcement/damping treatment to alleviate the acoustic fatigue damage of the nacelle panel of the F/A-18 aircraft. This experimental study will address the relevance of constrained layer damping reducing the incidence of acoustic fatigue problems in the nacelle region.

Up to now experimental and theoretical research on active structures for aerospace applications has put the focus mainly on surface bonded actuators. Simultaneously peizoceramics became the major type of actuating device being investigated for smart structures.In this context various techniques of insulating, bonding and operating these actuators have been developed. However, especially with regard to actuators only a few investigations have dealt with embedding of these components into the load bearing structure so far. With increasing shares of fiber- reinforced plastics applied in aerospace products the option of integrating the actuation capability into the components should be reconsidered during the design process. This paper deals with different aspects related to the integration of piezoceramic actuators into fiber reinforced aerospace structures. An outline of the basic possibilities of either bonding an actuator to the structure's surface or embedding it into the composite is given while the emphasis is put on different aspects related to the latter technology. Subsequently recent efforts at Daimler-Benz Aerospace Dornier concerning aircraft components with surface bonded actuators are presented. Design considerations regarding embedded piezoceramic actuators are discussed. Finally some techniques of non-destructive testing applicable to structures with surface bonded as well as embedded piezoelectric actuators are described.

The increasing demand for global communications and limitations on RF communications bandwidth has driven several constellations to baseline laser cross-links between the satellites within their constellations. The use of laser communications over a long distance dictates the need for accurate pointing and jitter suppression in order to maintain signal continuity. Vibrations upon a satellite bus or orbit come from several sources including: momentum systems, flexible appendages, motors and cryocoolers. Attenuation of these vibrations requires a combination of disturbance reduction, disturbance isolation, payload isolation, input command shaping, appendage damping and passive/active bus structural control. This paper addresses these techniques in a systems approach to satellite structural control. Experimental results from a representative flexible satellite truss structure using a series of integral D-Strut structural dampers is presented. The passive damping system is used to reduce resonant amplification of disturbances on precision optical equipment jitter. The use of different combinations of longitudinal, transverse and diagonal dampers is discussed to achieve specific modal damping. In addition, the design of the integral truss dampers is discussed along with their application to satellite bus construction.

The results of an initial investigation in the use of smart material system for automobiles are presented. For this work, a smart material system is defined as a network of embedded electromechanical devices that are able to sense and affect their environment and autonomously adapt to changes in operating conditions. The development of smart material system for production vehicles has the potential for compact, lightweight subsystems that reduce vehicle weight and improve vehicle performance. This paper presents an overview of current technology and how it contrasts with the development of highly integrated smart material systems. Automotive design requirements are examined to highlight practical constraints associated with integrating smart material technology into automobiles. Representative examples of a embedded sensor-actuator system for camless engines and a smart automotive seat are presented to illustrate the design concepts.

In this paper we focus on the special problem encountered during the damping of structurally stiff automotive sheet metal panes. These structurally stiff panels exhibit high amplitude low frequency vibrations along with medium frequency damping problem. Due to the wide frequency range desired for vibration suppression, passive damping is considered for these stiff panels. A classical automotive sheet panel is forced to vibrate by a shaker and the frequency-response-function (FRF) between the frame and the sheet panel is measured. The low-frequency FRFs along with the overall damping loss for the medium frequency range are presented. Unlike conventional damping materials, the new 'structural damping layer' (SDL) utilizes the inelastic collision and friction damping mechanisms, SDL exhibits comparable or better damping performance over the extensional dampers on structurally stiff sheet panels. Moreover, these SDL materials exhibit interesting temperature and acceleration dependence characteristics.

This paper presents an analysis of the fiber optic weight- in-motion (WIM) smart sensor situation. Based on the interrelationship between technology and needs, the analysis is divided into three parts. The first part reflects WIM equipment development, such as piezo-electric sensors, and some of the pitfalls encountered in WIM measurements that led to fiber optic sensor utilization. With a chronological approach, the second part reviews the various optical principles that have been developed to measure dynamic weight. Since 1986, three techniques have been fully tested on actual highways. On the one hand, the simplest one based on light attenuation in multimode fibers as suitable for counting. On the other hand, speckle analysis at the end of a multimode fiber allowed a better strain and deformation determination. Finally, the sophisticated polarimetric configuration seemed to be more powerful and led to impressive findings such as dynamic phenomenon observation. The third and last part of this paper reviews some of the future needs for WIM systems, and the ongoing developments in the intelligent transportation system (ITS) field. Then, the factual report derived from this analysis shows that despite their tremendous potential, fiber optic sensors are almost nonexistent in current ITS worldwide developments.

Noise emission suppression problem is more and more absorbing mechanical designers' efforts, in the recent times. It is not only a matter of comfort, but also of people exposure noise limits. A significant step has been moved in Europe with the issue of the EU Green Paper: Future Noise Policy. Impact on external and internal environment is requested to be considered in industrial and civil design. Low frequency disturbances are hard to be treated by classical passive methods. Active noise control presents great potentialities. In the last years, significant improvements have been attained in the field of interior acoustics, with particular reference to aircraft. Microphones and loudspeakers - based active systems have been put on the market, while interesting alternatives have been proved to be effective, implementing Smart Materials and Structures related concepts. The authors of this paper and of its continuation have been working for a long time inside the themes related to the noise control in aircraft cabins. Thin-walled beams have a certain importance; they are representative of fuselage range. This document deals with the design and the specifications definition, concerning a system addressed to the minimization of the vibration level of, or the sound power level radiated by , a general structure; in the specific case, a thin-walled beam was selected as test article, fully representative of general complex elements. The structure is identified and characterized through its experimental response. The set-up for the active control measurements is then described in detail; the acquired transfer functions have been elaborated to predict the performance of the real active control system.

Sound radiation is not only matter of comfort, but also of people's exposure noise limits. Public demand about the life quality is leading to produce laws and standards able to preserve people's health. The authors have been working for a long time in the field of Smart Structures, with the development of different hardware systems devoted to the characterization of implemented active devices and to their guidance. On the basis of what developed in the phase 1 of the research, a feed-forward controller has been developed, aimed at reducing the vibration field of, or the sound radiated by, generic elastic structures. Piezo-ceramic patches are used as actuators and accelerometers as sensors, so avoiding the use of microphones. In the specific case, a thin-walled beam has been referred to as representative of complex elements in general architectures and single tone excitations have been investigated. Key features of the controller: its capability in identifying the disturbance and following its frequency and amplitude variations; the frequency independence of the 90° phase shifter analog section. The application here presented deals with the band around 100 Hz, specifically interesting for human annoyance problems, a range where passive noise reduction systems are ineffective.

This paper describes a Smart Spindle Unit (SSU) integrated with Ingersoll's Horizontal Octahedral Hexapod Machine for providing active chatter suppression during milling operations.Fabrication of actuator and sensor components and integration of those components into the SSU will be described in detail. The SSU has a hydrostatically supported spindle cartridge. This cartridge can be moved in directions orthogonal to the axis of rotation of the spindle by using four electrostrictive actuator/force sensor assemblies. Tool tip vibration is sensed by strain gages located at the root of the tool. These measurements are transmitted off the rotating spindle by frequency modulated radio transmissions which are captured by a demodulating receiver and then converted to the non-rotating coordinate system of the actuators. Displacement sensors located on the spindle housing will also be used to monitor motion of the outer bearing race during operation. A model based DSP controller will be used to drive the actuators which will dynamically stiffen tool tip motion thus suppressing chatter during milling operations.

This paper addresses dynamics and control issues encountered in development of a smart spindle unit (SSU) for suppressing chatter in milling operations. The SSU comprises a suite of strain, displacement and force sensors coupled to four, high-force, electrostrictive ceramic actuators through a digital control processor. The operating principles of the SSU are discussed, and salient dynamics of the SSU and generic milling tools are explored in this context. Dynamic characteristics measured using the SSU sensors are presented and discussed relative to their influence on chatter and control of chatter.

In the last decade smart technologies have become enablers that cut across traditional boundaries in materials science and engineering. Here we define smart to mean embedded actuation, sensing, and control logic in a tightly coupled feedback loop. While multiple successes have been achieved in the laboratory, we have yet to see the general applicability of smart devices to real aircraft systems. The NASA Aircraft Morphing program is an attempt to couple research across a wide range of disciplines to integrate smart technologies into high payoff aircraft applications. The program bridges research in seven individual disciplines and combines the effort into activities in three primary program thrusts. System studies are used to assess the highest-payoff program objectives, and specific research activities are defined to address the technologies required for development of smart aircraft systems. In this paper we address the overall program goals and programmatic structure, and discuss the challenges associated with bringing the technologies to fruition.

An overview of smart structures research currently underway a the NASA Langley Research Center in the areas of aeroservoelasticity and structural dynamics is presented. Analytical and experimental results, plans, potential technology pay-offs, and challenges are discussed. The goal of this research is to develop the enabling technologies to actively and passively control aircraft and rotorcraft vibration and loads using smart devices. These enabling technologies and related research efforts include developing experimentally validated finite element and aeroservoelastic modeling techniques; conducting bench experimental test to assess feasibility and understand system trade-offs; and conducting large-scale wind-tunnel of rotor blades using interdigitated electrode piezoelectric composites and active control of flutter, and gust and buffeting responses using discrete piezoelectric patches. In addition, NASA Langley is an active participant in the DARPA/Air Force Research Laboratory/NASA/Northrop Grumman Smart Wing program which is assessing aerodynamic performance benefits using smart materials.

The paper summarizes active flow control projects currently underway at the NASA Langley Research Center. Technology development is being pursued within a multidisciplinary, cooperative approach, involving the classical disciplines of fluid mechanics, structural mechanics, material science, acoustics, and stability and control theory. Complementing the companion papers in this session, the present paper will focus on projects that have the goal of extending the state- of-the-art in the measurement, prediction, and control of unsteady, nonlinear aerodynamics. Toward this goal, innovative actuators, micro and macro sensors, and control strategies are considered for high payoff flow control applications. The target payoffs are outlined within each section below. Validation of the approaches range from bench-top experiments to wind-tunnel experiments to flight tests. Obtaining correlations for future actuator and sensor designs are implicit in the discussion. The products of the demonstration projects and design tool development from the fundamental NASA R and D level technology will then be transferred to the Applied Research components within NASA, DOD, and US Industry.

Mechatronic design implies the consideration of integrated mechanical, electrical, and local control characteristics in electromechanical device design. In this paper, mechatronic development of actuation device concepts for active aircraft aerodynamic flow control are presented and discussed. The devices are intended to be embedded in aircraft aerodynamic surfaces to provide zero-net-momentum jets or additional flow-vorticity to control boundary layers and flow- separation. Two synthetic jet device prototypes and one vorticity-on-demand prototype currently in development are described in the paper. The aspects of actuation materials, design approaches to generating jets and vorticity, and the integration of miniaturized electronics are stressed.

This paper represents an initial study on the use of quasi- static shape change devices in aircraft maneuvering. The macroscopic effects and requirements for these devices in flight control are the focus of this study. Groups of devices are postulated to replace the conventional leading- edge flap (LEF) and the all-moving wing tip (AMT) on the tailless LMTAS-ICE configuration. The maximum quasi-static shape changes are 13.8% and 7.7% of the wing section thickness for the LEF and AMT replacement devices, respectively. A computational fluid dynamics panel code is used to determine the control effectiveness of groups of these devices. A preliminary design of a wings-leveler autopilot is presented. Initial evaluation at 0.6 Mach at 15,000 ft. altitude is made through batch simulation. Results show small disturbance stability is achieved, however, an increase in surface deflection is needed to offset five degrees of sideslip. This only applied to the specific device group studied, encouraging future research on optimal device placement.

Strain actuators, used to induce a relative structural displacement, are most effective when integrally embedded into the host structure. The paper summarizes progress and challenges in the field of embedding smart materials into structures. The difficulties of embedding active elements within composite structures are described from a system design perspective. Issues associated with the application of strain actuators in primary aircraft structure are discussed. Development of new embedding technology to combat the difficulties with high strain applications is advocated.

Reported herein is an overview of the research being conducted within the materials division at NASA Langley Research Center on the development of smart material technologies for advanced airframe systems. The research is a part of the Aircraft Morphing Program which is a new six- year research program to develop smart components for self- adaptive airframe systems. The fundamental areas of materials research within the program are computational materials; advanced piezoelectric materials; advanced fiber optic sensing techniques; and fabrication of integrated composite structures. This paper presents a portion of the ongoing research in each of these areas of materials research.

Piezocomposite SmartPanels, consisting of 1-3 actuators and pressure sensors and net-shape PZT accelerometers in a large area, low profile panel, have been fabricated and evaluated. Single layer and two-layer 100 x 100 mm and 250 x 250 mm SmartPanels have been tested for actuator authority, surface displacement uniformity, sensor-actuator coupling, and surface vibration reduction. Single layer SmartPanels have demonstrated a broad band 20 dB underwater surface vibration reduction. Current development activities include electronics integration for surface mounted SmartPanels and investigation of SmartPads in hybrid active-passive vibration isolation mounts. SmartPanels draw upon PZT injection molding technology, which is used to produce cost- effective and robust 1-3 piezocomposite materials. The piezocomposites are used extensively for SonoPanel transducers in a number of sensor and actuator applications. SonoPanels are qualified for US Navy applications, based on successful completion of pressure and shock tests, and are available in sizes up to 750 x 750 mm. Applications and performance for SmartPanels and SonoPanels are descried, including multi-element arrays, velocity sensors, and underwater vibration and noise reduction devices.

This paper describes ongoing design and fabrication work on a vortex wake control system for submarines that employs SMA-actuated devices. Previous work has described the theoretical basis and feasibility studies for this system, which is based on a novel wake control scheme known as vortex leveraging. The critical item in the realization of this system is a Smart Vortex Leveraging Tab (SVLT), whose design and fabrication is the principal focus of this work. This paper outlines the background of the effort and the design principles involved, but will chiefly deal with three closely interrelated topics; the hydrodynamic design requirements and control surface layout for the vortex leveraging system; the detail design and fabrication techniques being used in the construction of a prototype SVLT; and the test planning and experiment design process currently underway for test of both the overall vortex leveraging concept and SVLT device itself.

The Smart Structures for Rotor Control (SSRC) is a consortium under the Defense Advanced Research Projects Agency (DARPA) Smart Structures program. Phase I of the program was administered by the Air Force Office of Scientific Research, with Boeing Seattle as the consortium administrator, and MIT, PSU and Boeing Helicopters as the other principal consortium members. Phase II, renamed Smart Materials and Structures Demonstration Consortium (SMSDC), is a combination of the proposed Phase II efforts of SSRC and the Boeing MESA Smart Materials Actuated Rotor Technology (SMART) program. This paper summarizes the SSRC efforts, introduces the SMSDC program, and provides a framework for the relationships between specific SSRC technical papers in this conference. The SSRC objectives were to research smart structure methods to achieve reduced rotorcraft vibration, reduce acoustic noise, and increased performance. The SSRC program includes dynamic piezoelectric actuation of flaps on the rotor blades, distributed dynamic piezo actuation of the rotor twist, and quasi-steady rotor twist control using shape memory alloys. The objective of Phase II is then to fly a rotorcraft to demonstrate such a system.

An airfoil with a TERFENOL-D powered smart trailing edge is being developed to minimize drag during transonic cruise. TERFENOL-D linear motors move segmented flaps that continuously modify the trailing-edge shape for optimum performance. The system is mechanized to maintain smooth upper-surface shapes.The flap sizes and geometric parameters are being optimized with a modified simulated annealing technique. A full potential solver coupled to an integral boundary-layer method is used to simulate the aerodynamics. Average drag improvements over the lift-coefficient range are 16 counts at Mach 0.815 and 46 counts at Mach 0.726. The result of the optimization are checked for validity and flow separation with a higher-fidelity Navier-Stokes solver. A proof-of-concept TERFENOL-D elastic-wave linear motor has been built, and provides 1.5 in. strokes at the required speed of roughly 1 in./min. The motor is currently being used to power an engineering model of the smart trailing edge. Mathematical models and testing are being employed to investigate geometric, magnetic, and electronic design improvements which have the potential to significantly improve motor performance.

An active vibration suppression system (AVSS) was designed and flight tested on a B-1B aircraft aft fuselage skin panel subjected to engine noise and unsteady flow induced vibrations. This was the first time an AVSS was successfully demonstrated in flight on a high performance combat aircraft. The purpose of the feasibility test was to confirm that an AVSS could significantly reduce structural vibrations and still survive in an aircraft service environment with a severe acoustic field. The system used piezo-ceramic (PLZT) patch type actuators developed by the Rockwell Corporation, that demonstrated superior performance relative to commercial PZT's. The active system using H- infinity control laws was developed to maximize the force generated by each PLZT actuator and to minimize the micro- processor processing time and control system instabilities. PLZT coupon tests were used to determine the size, shape, and thickness of the PLZT and to test epoxies and the epoxy bonding thickness that will give the best performance under the flight environmental conditions. Three micro-processing boards were considered to minimize the processing time and two boards were tested before the final selection was made. The hardware were designed, wired, and tested in a laboratory acoustic tunnel on a flat plate and on a curved panel that simulated the B-1B aft fuselage panel. The laboratory test showed the PLZT patches could drive the curved panel to similar g levels as on the aircraft. The lab tests also showed the response of the first mode could be eliminated with the active controller. The resulting system design was installed and flight tested on a B-1B aircraft aft fuselage skin panel that is subjected to jet noise. The system was successful in reducing the fundamental panel vibration modes as much as 79 percent for the takeoff conditions and about 46 percent for transonic flight conditions, with 25 percent response reductions for a higher order mode. The paper presents a discussion of the control system development and the active vibration suppression system performance.

A comparative review of actuation technologies is presented. Innovative mechanisms ideas that combine high force and deflection are described. Flexible smart actuators are obtained utilizing real time adaptive biomorphic controls. Such flexible smart actuators constitute an enabling technology for a variety of biomorphic systems ranging from small, agile biomorphic explorers that emulate biological mobility to much larger humanoid or anthropomorphic system. Due to their potential ability to explore difficult, hard- to-find terrain, biomorphic explorers are promising for a variety for application in law enforcement, hazardous environment inspection, toxic waster avoidance/elimination, law enforcement, hazardous environment inspection, toxic waste avoidance/elimination, law enforcement, and search/rescue in disaster areas such as earthquake sites. The control mechanisms used for the actuators are based on biological principles. For example, a neurally inspired controller provides a mapping between the current state of the robot and a target internal configuration. Innovative fordable advanced mobility mechanisms in combination with multipod techniques inspired by peristalsis in an earthworm robot are described. Flexible actuators offer the versatility of both shape control as well as mobility attribute control.

Ceramics injection molding technology is being adapted for the fabrication of net shape piezoelectric actuators of lead zirconate titanate (PZT) and lead magnesium niobate (PMN). INjection molding offers low cost, high quality actuator components with a high degree of part-of-part reproducibility. Configurations under investigation include a proprietary high displacement linear element, air acoustic actuators, tube array actuators, benders, and various multilayer designs. Applications include conformable unidirectional patches for active noise and vibration control, high displacement bender actuators for active vortex generators and synthetic jets, high force-high displacement actuators for rotorblade flaps, and air acoustic actuators for active noise reduction.

Optical fiber sensors, because of their small size, low weight, extremely high information carrying capability, immunity to electromagnetic interference, and large operational temperature range, provide numerous advantages over conventional electrically based sensors. Fiber-based sensors have found numerous applications in industry for process control, and more recently for monitoring the health of advanced civil structures. This paper presents preliminary results from optical fiber sensor designs for monitoring acceleration and magnetic field.

Smart materials and structures offer significant commercial potential beyond their intended aerospace uses. ITN Energy Systems has been aggressively pursuing the commercialization to shape memory alloys, and present herein several product development case studies. We also provide recommendations for material improvements which would enhance marketability of shape memory and other smart materials systems.

The ambient air ingested through the inlet of a gas turbine is first compressed by an axial compressor followed by further compression in a centrifugal compressor and then fed into the combustion chamber where ignition and expansion take place to produce the engine thrust. The axial compressor typically has five or more stages which consist of revolving blades and stators and the overall performance of the turbine is strongly affected by the compressor efficiency. When the turbine is turned on, to accommodate the rapid initial increase in the compressor blade length due to centrifugal force, the cold turbine has a built in clearance between the turbine blade tip and the casing. As the turbine reached its operating temperature there is a further increase in the blade length due to thermal expansion and, at the same time, the diameter of the casing increases. The net result is that when these various components have reached their equilibrium temperatures, the initial cold build clearance is reduced, but there remains a residual clearance. The magnitude of this clearance has a direct effect on the compressor efficiency and can be stated as: Δη/Δ CLR equals 0.5 where η is efficiency and CLR is the tip clearance. The concept of adaptive tip clearance control is based on the ability of a shape memory alloy ring to shrink to a predetermined diameter when heated to the temperature of a particular stage, and thus reducing the tip clearance. The ring is fabricated from a CuAlNi shape memory alloy and is mounted in the casing so as to be coaxial with the rotating blades of the particular stage. When cold, the ring dimensions are such as to provide the required cold build clearance, but when at operating temperature the reduced diameter creates a very small tip clearance. The clearance provided by this concept is much smaller than the clearance normally obtained for a turbine of the size being studied.

Prevailing torque lock nuts are divided into classes which relate to their temperature of use, and for temperatures up to 250 degrees F the most commonly employed locking device is a nylon insert. Although manufacturers of these devices claim that they are reusable, the Air Force requires that once removed, this type of lock nut must be replaced. An approach to a lock nut which has installation and removal torque's which conform to MIL specifications and can be reused many times is based on a castleated nut whose fingers are confined by a shape memory alloy ring. When installed on a male threaded component, the ring is forced open against the shape memory ring restraint, producing the frictional force inhibiting nut loosening from vibration and shock. Pseudoelastic nickel titanium rings were shown to perform well, but the temperature range for pseudoelasticity is limited to about 40°C. MIL specifications require that the locking characteristics be uniform from -51 to +71°C. Linear superelastic behavior can be generated in a NiTi alloy by cold work, and in this form strains up to 4% are fully recoverable over a wider temperature range: from -100 to +200°C. The square cross section rings employed on the smaller nut sizes, e.g. 1/4", 5/16" and 3/8" require precise dimensional control creating a difficult machining problem since the NiTi family of alloys are notoriously difficult to machine. An alternative titanium based alloy, developed for medical devices and contains no nickel, and was successfully substituted. Nut design and locking torque characteristics of nuts subjected to vibration and shock will be described.

A basic step in the monitoring of health of any structure is detection of damage levels and location of the damage in the system. Several damage detection schemes have been proposed in recent years. Published applications of these methods are typically for simplified models of realistic structures. This leaves open the question of the accuracy and efficiency of the available damage detection methods when applied to large and complex structural models. This paper will investigate the accuracy of different damage detection techniques to complex structural models. A typical multi- jointed steel bridge, which is damaged by cracks of different sizes, is considered. The damage will be simulated analytically in the structural model, and the damage detection algorithms will be applied to both the damaged and the undamaged structures. Three damage detection algorithms are investigated, namely the change of stiffness, the change of flexibility and the damage index methods. Some modifications and extensions of the change of stiffness and change of flexibility methods were incorporated in this study. These extensions helped inaccurate comparisons between different methods. It was found that all three algorithms produced adequate damage detection results. More analytical studies are recommended. Also, experimental testing for complex structures is recommended.

This paper presents an analysis of fiber distributed sensors applied to power cable fault management, and proposes a more suitable solution for the future. In tomorrow's fast-paced deregulated environment, exploiting new technologies for competitive advantage has become a major incentive in the power business delivery. In power lines, the main parameters that need real time checking are temperature, partial discharges, and mechanical forces. If unchecked, these parameters can seriously damage the insulation system of high-voltage power apparatus and them reduce their life expectancy. This paper deals with these three parameters and presents today's state-of-the-art. The first part analyzes the current situation by pointing out the most commonly used technique for temperature measurement: the anti Stokes Raman back-scattering method. The simple fact that the principle is based on natural or spontaneous light emission as a function of temperature make it work. However, the low signal and its slow response does not allow partial discharge considerations. The second part reviews a new more powerful technique that allows both force and temperature measurements. The principle is based on forward time division multiplexing with a two-guiding region fiber. With a view to emphasizing a specific parameter among the others, distributed temperature sensors using stimulated light amplification in rare earth-doped optical fibers are proposed. If applied, this technique would generate a more usable signal for both temperature measurement and rapid change. All in all, this paper gives a fair insight into power cable total fault management.

A low-cost high-speed demodulation system based on a fiber grating spectral filter has been developed to support strain and temperature sensing in composite panels. This system has also been used to support high-speed impacts on composite panels. This paper will describe the system, its current state of development, and some of the applications it is supporting.

A need exists to gather data form diverse sources for the purposes of system analysis and control. Many of these data sources are located in environments where power is unavailable, and space is at a premium. These environmental constraints coupled with market pressures that dictate rapid, costs effective installation establish the need for wireless data collection. Wireless systems redefine the term 'remote sensing.' This type of sensory information is thought of as non-intrusive and can be acquired at a location that is remote from the data source. This collection of data at a point remote from the source can be advantageous due to environment, access, or sociopolitical conditions. Remote sensing has many advantages from both a technical and commercial perspective. Highway bridge analysis using conventional methods can require several weeks of sensor and wire placement. As much as 6 miles of wire may be used to connect the sensors to get analytical results on one structure. High performance aircraft testing using hardwired sensors may require as much as 9 months of tedious wiring before tests can begin. At the conclusion of the tests, the wire must be removed so the aircraft can be returned to service. Using wireless remote sensing, these tasks can be performed in fractions of the previous time due to the dramatic reduction in wiring. Further, wireless technology can enable sensors to be placed at locations previously inaccessible due to space limitations.

Structural health monitoring (SHM) technology provides a means to significantly reduce life cycle of aerospace vehicles by eliminating unnecessary inspections, minimizing inspection complexity, and providing accurate diagnostics and prognostics to support vehicle life extension. In order to accomplish this, a comprehensive SHM system will need to acquire data from a wide variety of diverse sensors including strain gages, accelerometers, acoustic emission sensors, crack growth gages, corrosion sensors, and piezoelectric transducers. Significant amounts of computer processing will then be required to convert this raw sensor data into meaningful information which indicates both the diagnostics of the current structural integrity as well as the prognostics necessary for planning and managing the future health of the structure in a cost effective manner. This paper provides a description of the key types of information processing technologies required in an effective SHM system. These include artificial intelligence techniques such as neural networks, expert systems, and fuzzy logic for nonlinear modeling, pattern recognition, and complex decision making; signal processing techniques such as Fourier and wavelet transforms for spectral analysis and feature extraction; statistical algorithms for optimal detection, estimation, prediction, and fusion; and a wide variety of other algorithms for data analysis and visualization. The intent of this paper is to provide an overview of the role of information processing for SHM, discuss various technologies which can contribute to accomplishing this role, and present some example applications of information processing for SHM implemented at the Boeing Company.

The performance of smart structures is a complex interaction between active and passive components. Active components, even when non-activated, can have an impact on structural performance and, conversely, structural characteristics of passive components can have a measurable impact on active component performance. The present work is an evaluation of the structural characteristics of an active panel designed for acoustic quieting. The support structure is included in the panel design as evaluated. Finite element methods are used to determine the active panel-support structure response. Two conditions are considered; a hollow unfilled support structure and the same structure filled with a polymer compound. Finite element models were defined so that stiffness values corresponding to the center of individual pistons could be determined. Superelement techniques were used to define mass and stiffness values representative of the combined active and support structure at the center of each piston. Results of interest obtained from the analysis include mode shapes, natural frequencies, and equivalent spring stuffiness for use in structural response models to represent the support structure. The effects on plate motion on piston performance cannot be obtained from this analysis, however mass and stiffness matrices for use in an integrated system model to determine piston head velocities can be obtained from this work.

The purpose of this paper is to present the preliminary experimental results on the influence of vibration confinement on the optimization of sensor and actuator placement in smart structures. Previous studies have indicated that vibration confinement may have significant effects on the optimal location of sensors and actuators. Three types of structures, beam, plate, and cylinder structures, are examined in this paper. Two criteria based on an observability/controllability measure and actuator power requirements are used to evaluate the sensor/actuator performance. Based on our experimental results, it is clear that confinement has a significant impact on the optimization of sensors and actuators.

This paper presents the result of an experimental study to investigate the potential advantages of using passive vibration confinement over conventional active vibration control methods, as well as to investigate the benefits of using the two methods simultaneously. The general approach is to compare the result of actively controlling vibrations in a beam which sees various degrees of modal confinement. Vibration confinement is carried out passively, and the comparison is based on control effort required as well as vibration control performance achieved. To date, there has been a significant amount of work in the area of vibration confinement, or mode localization, but the focus has been primarily either 1) that it is an interesting phenomenon which exists in structures or 2) that it can be produced in structures through active, passive, or hybrid means to achieve some end such as vibration control. This paper presents an experimental follow-up to an earlier numerical study which directly compared confinement techniques to conventional active vibration control methods, and showed how confinement can be used to enhance conventional vibration control. Although not as dramatic, the result presented in this paper clearly support that study and show that passive vibration confinement can enhance active control through both performance and energy consumption.

Ultrasonic technology applications have been researched in a wide range of fields, from sonochemistry and industrial cleaning to medical tools and agriculture. However, the largest limitation in many of these applications is the inability of existing technology to provide a single transducer with sufficient power to make important laboratory sonochemical processes commercially successful. TERFENOL-D magnetostrictive material technology enables a next-generation high power ultrasonic transducer. Until very recently, generating high power at high frequency has been unexplored territory for giant magnetostrictive materials. But the unique attributes of these materials, such as energy density and thermal handling capabilities, are being used to develop a wide variety of transducers, devices and systems for existing as well as new ultrasonic applications. These unique material attributes combine with novel magnetic field generation, transducer, acoustic transmission and coupling concepts to meet the challenges of power, size, thermal, efficiency and reliability requirements of transducers and system for many ultrasonic applications. Polymer processing and curing, enhanced oil and gas recovery, seed sonication, surgical tools, and beer foaming are just some of the many applications where ultrasonic magnetostrictive technologies are overcoming barriers to provide improved solutions.

The unique attributes of magnetostrictive materials have been used to develop a wide variety of electromechanical transducers and devices. Most of these applications have been at or above room temperature. However, many applications at cryogenic temperatures also require high authority, high precision, efficient actuation. Other technologies, including all piezoelectric systems, tend to be inoperable or impractical and unreliable at cryogenic temperatures. Magnetostrictive materials have already demonstrated improved performance at low temperature down to near absolute zero with strains as high as 1% possible. These unique material attributes combine with novel magnetic field generation, transducer and mechanism concepts to meet the challenges of resolution, size, weight, power, thermal and reliability requirements of actuators for many cryogenic applications. Positioning and shaping optics in space, cryogen valving and pumping, heat switches, industrial processing, and active vibration control are just some examples of the many commercial, military and space applications where cryogenic magnetostrictive technologies are overcoming barriers to provide solutions.

This paper describes the development and testing of a 3KV, 400 ma piezo drive switching amplifier. This amplifier is used to drive Piezo Fiber Composite material embedded in a 1/6 scale CH-47 blade. This amplifier will allow higher harmonic control of the blade thus reducing rotor craft vibration and noise. The amplifier recycles reactive energy required to drive piezo material allowing for an efficient amplifier design. A multi level topology is used allowing solid state switching devices with voltage rating of half the output drive voltage. The amplifier modular design allows easy migration to the power levels required to drive a full size CH-47 blade. This work was done in conjunction with the Smart Structures for Rotor Craft Control in support of DARPA/AFOSR.

In this paper, the power flow between stacked electrostrictor actuators and a pulse-width-modulated switching amplifier is analyzed. The amplifier and actuator are components of a smart skin whose function is underwater acoustic echo cancellation. An integrated model is developed with includes a dynamic structural model of the actuator, a dynamic model of the power electronics and a nonlinear electromechanical coupling mechanism of the electrostrictor actuation materials.Using a linearized model, the mechanical admittance of the actuator seen by an external force is analyzed. An outer acoustic control loop is shown to modify this mechanical admittance and optimize the power coupling between the actuator and an external fluid medium by impedance matching. Effective power flow occurs only when the frequency of the external force is within the bandwidth of the amplifier.

Electroheological (ER) fluids have electrically controllable stiffness, heat transfer and flow properties. Since their invention in 1947, they have been proposed for a variety of applications involving the electrical control of systems such as hydraulic valves, clutches, heat exchangers and suspension systems. Previous approaches to application of ER fluids have been hampered by the relatively slow, strongly time-dependent, non-linear behavior of these fluid systems. The effects of electric field activation history, temperature and humidity also contribute to wide variation in 'open-loop' sped and strength of response. Successful application of ER fluids to engineering systems requires fast, precise control of the internal micro-scale fluid state which yields the controllable macro-scale properties to be exploited. This work presents a 'closed-loop', laser- sensing, feedback control approach of ER fluid state which allows for higher initial field strengths to speed ER response while lowering the level of applied electric field to exactly that level required to maintain a specified level of ER fluid viscosity, stiffness, thermal conductivity or radiative energy transmissibility. The key to the work is a laser-based optical sensor of fluid internal state. An analytical model for both the ER fluid and control systems are developed which predicts ER fluid system response as controlled field drive is varied. Predicted ER fluid responses from the analytical model are then compared with laboratory measured responses for a prototype feedback controlled ER fluid system. Laser sensing and feedback allows the us of these fluids in a wide variety of applications where the lack of fast, precise control limited their past use. The ability to quickly and precisely control ER fluid response may make possible the applications of ER fluids promised since their invention 5 decades ago. When compared against conventional 'open-loop' fluid control methods, laboratory tests of 'closed-loop' feedback control demonstrate ER fluid response both 30 times faster with 30 times more precision than previously possible.

A finite element method for the analysis of thermal deflection and random response is presented for shape memory alloy (SMA) fiber reinforced composite plates subjected to thermal and acoustic loads. The formulation considers the temperature dependent nonlinear material properties of SMAs, the initial deflection and initial stresses, and the geometrical nonlinearity of large thermal deflections. A two-step solution procedure for the combined thermal and acoustic loading is employed consisting of an incremental method for the material nonlinearities and a Newton-Raphson iteration method for prediction of panel responses. Examples are given to show that it is feasible to eliminate the large thermal deflection completely and to reduce the dynamic random response within a given operating temperature range with the proper percentages of SMA volume fraction, prestrain and alloy composition.

An integrated and automated smart structures approach for structural health monitoring applications is presented. This approach, called Active Damage Interrogation (ADI), utilizes an array of piezoelectric transducers attached to or embedded within the structure for both actuation and sensing. The ADI system actively interrogates the structure via broadband excitation of multiple actuators across a desired frequency range. The structure's vibration signature is the characterized by computing the transfer functions between each actuator/sensor pair, and compared to the baseline signature. Statistical analysis of the transfer function deviations from the baseline is used to detect, localize, and assess the severity of damage in the structure. Experimental results of applying the ADI system for local area damage detection in a MD Explorer rotorcraft composite flexbeam are presented. The performance of the system in detecting and localizing internal delaminations created by low velocity impacts is quantified. The results obtained thus far indicate considerable promise for integrated structural health monitoring of aerospace vehicles, leading to the practice of condition-based maintenance and consequent reduction in vehicle life cycle costs.

A magnetostrictive wire-bonding clamp for use in semiconductor packaging applications has been developed by Mechatronic Technology Co. Semiconductor industry trends, requiring high process throughput on increasing lead count packaging, make the magnetostrictive material Terfenol-D a candidate for this application. To construct this small, lightweight device, small samples of Terfenol-D were prepared by ETREMA Products, Inc. This paper reports the initial design, mathematical modeling, and experiments related to this initial prototype.

In magnetorheological finishing (MRF) the mechanical energy for material removal is generated by the hydrodynamic flow of a magnetorheological (MR) polishing suspension through a converging gap that is formed by a workpiece surface and a moving rigid wall. In addition to causing material removal, MRF also reduces the surface micro roughness of optical materials to ≤ 10 Å rms. Shape errors are corrected to a fraction of a wavelength of light and subsurface damage is removed. A theoretical analysis of MRF, based on Bingham lubrication theory, illustrates that the formation of a core attached to the moving wall results in dramatically high stress on the workpiece surface. A correlation between the shear stress on the workpiece surface and materials removal is obtained.

Practical applications of smart structure technology to active acoustic noise control demand high performance at low cost. Typically, performance increase achieved by reducing control system latency are expensive. Furthermore, sonar echo cancellation is concerned with a wide frequency range for which linear time-invariant (LTI) controllers provide inadequate performance, and no direct error measurement is available to drive adaptive controllers. Real-time estimators of the cancellation error have been proposed to enable the use of adaptive controllers, however this significantly increases the system cost. In this paper, we introduce a frequency scheduled control architecture for echo cancellation which achieves adaptive control performance at LTI control prices, by exploiting the narrow instantaneous bandwidth commonly associated with individual sonar pings.