As known, the electrical induced strain of conventional piezoceramic materials is limited by 0.12 % (2 kV/mm), which
often requires strain transformation designs, like levers, in order to meet application needs. High fabrication accuracy
and low tolerances are crucial points in mechanical manufacturing causing high device costs.
Therefore, we developed a piezoelectric composite actuator with inherent stress - strain transformation. Basically,
piezoceramic sheets are laminated with spring steel of a certain curvature, which can be realised by a comparatively
simple fabrication technique. The working diagram of these composite bow actuators showed a high level of
performance adaptable to a wide range of applications. The authors established the value chain covering the
piezoceramic formulation, the processing technology and the design in view of optimum system performance.
The paper presents an overview of the design principles, simulation and various aspect of fabrication technology
including lamination, sintering and polarization. The new devices are useable in different sectors, for example in
automotive industry as solid state transducer or as the active part in injectors. Moreover, the composite bow actuators
may find application in microsystems technology, micro optics and micro fluidics as well as vibration dampers. The
composite bow actuators can be used as single component transducer, as well as multi-bow actuator in series or parallel
combination on demand.
This paper examines the possibility of constructing deformable mirrors for adaptive optics with a large number of degrees of freedom from silicon wafers with bimorph piezoelectric actuation. The mirror may be used on its own, or as a segment of a larger mirror. The typical size of one segment is 100 to 200 mm; the production process relies on silicon wafers and thick film piezoelectric material deposition technology; it is able to lead to an actuation pitch of the order of 5 mm, and the manufacturing costs appear to grow only slowly with the number of degrees of freedom in the adaptive optics.
This paper examines the possibility of constructing deformable mirrors for adaptive optics with a large number
of degrees of freedom, by assembling segmented silicon mirrors with bimorph piezoelectric actuation. The
production process relies on silicon wafers and thick film PZT deposition technology; it is able to lead to an
actuation pitch of the order of 5 mm, and the manufacturing costs appear to grow only slowly (linearly or less)
with the number of degrees of freedom in the adaptive optics.
Developed at NASA Langley Research Center during the late 90's, the Macro Fiber Composites (MFC) are manufactured by Smart Material Corp. in a full-scale production, today. Numerous research projects have proven the concept of using the MFC in vibration and noise control applications, as well as for health monitoring, morphing of structures and energy harvesting. Because basic performance parameters of products are considerably improved, like for example energy economy, precision and comfort, a widespread use of active structures is expected in the next future. Different MFC types are commercially available meeting already the requirements of a variety of applications. The migration from research projects to high volume, cost effective commercial applications has generated additional need for new MFC designs, electronics on microcontroller and chip level, and system design tools, as well. In this paper, we give an overview of recent progress in the development of the MFC transducers and MFC systems technology.
The mission of the Fraunhofer Gesellschaft, one of the biggest research facilities in Germany, is to identify technologies with a high impact potential for commercial applications and to take all necessary steps to successfully promote them by performing cooperative industrial research activities. One of these technologies is called smart structures, also known as adaptive structures. Most recently, Fraunhofer decided to strategically extend its portfolio to include this technology and summarize its R&D activities in the FIT (Fraunhofer Innovation Topics) ADAPTRONIK. To improve Fraunhofer's competencies in adaptronics, especially with respect to system design and implementation, the Fraunhofer internal project MAVO FASPAS was launched in 2003. Now, after 3 years of work, the project comes to a close. This article discusses some major project results.
This paper gives a summary on advanced piezocomposite transducers and the perspective of their applications in the field of smart structures, health monitoring and diagnostics. At present, three different low profile piezocomposite actuator types are commercially available. The designs are arising from the R&D work at MIT in the years 1991/92 funded by the US Department of Defence. Smart Material is manufacturing Macro Fiber Composites (MFC), licensed by NASA in a full-scale production. A new MFC- design using the 3-1 coupling has been developed, recently. It allows for the reduction of drive voltage down to 360 V. Fraunhofer IKTS focused its development on custom shape composites making use of PZT tubes and plates. New actuator devices for active interfaces have been introduced for the first time. All piezocomposite design forms show different performance data, which are summarised in the present paper to provide design engineers with necessary informations in view of intended applications.
The Fraunhofer Gesellschaft is the largest organization for applied research in Europe, having a staff of some 12,700, predominantly qualified scientists and engineers, with an annual research budget of over one billion euros. One of its current internal Market-oriented strategic preliminary research (MaVo) projects is FASPAS (Function Consolidated Adaptive Structures Combining Piezo and Software Technologies for Autonomous Systems) which aims to promote adaptive structure technology for commercial exploitation within the current main research fields of the participating FhIs, namely automotive and machine tools engineering. Under the project management of the Fraunhofer-Institute Structural Durability and System Reliability LBF the six Fraunhofer Institutes LBF, IWU, IKTS, ISC, AiS and IIS bring together their competences ranging from material sciences to system reliability, in order to clarify unanswered questions. The predominant goal is to develop and validate methods and tools to establish a closed, modular development chain for the design and realization of such active structures which shall be useful in its width and depth, i.e. for specific R&D achievements such as the actuator development (depth) as well as the complete system design and realization (width). FASPAS focuses on the development of systems and on the following scientific topics: 1) on design and manufacturing technology for piezo components as integrable actuator/sensor semi-finished modules, 2) on development and transducer module integration of miniaturized electronics for charge generating sensor systems, 3) on the development of methods to analyze system reliability of active structures, 4) on the development of autonomous software structures for flexible, low cost electronics hardware for bulk production and 5) on the construction and validation of the complete, cost-effective development chain of function consolidated structures through application oriented demonstration structures. The research work will be oriented towards active vibration control for existing components on the basis of highly integrated, both, more or less established and highly innovative piezoelectric actuator and sensor systems in compact, cost-effective and robust design combined with advanced controllers. Within the presentation the project work will be shown using the example of one demonstration structure which is a robust interface, here for being integrated within an automotive spring strut system. The interface is designed as a modular, scalable subsystem. Being such, it can be used for similar scenarios in different technology areas e.g. for active mounting of vibration-inducing aggregates. The interface design allows for controlling uniaxial vibrations (z-direction) as well as tilting (normal to the uniaxial effect) and wobbling (rotating around the z-axis).
The development of a new technology for the manufacturing of adaptive structures on the basis of thin monolithic peizoceramic wafers is an important goal of the German industrial project 'Adaptronik'. Partners from automotive-, space-, medical-, engineering- and optical industry participate in this project to enable new adaptive solutions for their applications. Due to the extreme brittleness of the piezoceramic material the manufacturing of these structures is still very demanding. Very often cracks in the piezoceramic material make the structure useless. This problem becomes serious when large scale structures with many actuators and sensor are considered. To come to more reliable results the use of encapsulated piezoceramic actuators and sensor came into focus. With respect to the great variety of different requirements given by the industrial partners the use of standardized solutions was not feasible. The goal was to develop new elements with improved performance parameters that can easily be adapted to different applications. Due to a modular concept, the developed multifunctional elements can be designed to meet a great variety of different structures was developed. A first step to adapt this technology to prototype structures has been done by the development of special encapsulated patches for an adaptive lightweight satellite mirror.
The field of 'Adaptronics' combines sensor and actuator effects with electronics. The components furnished with adaptronics shall sense relevant properties and shall adapt in an intelligent way - they shall 'feel, thick and act'. For instance, one application is the active vibration compensation of dynamically stressed structures. So far, adaptronics utilizes actuators - and partly also sensors - in the mm size range which posses a substantial stiffness. If such actuators/sensors were to be integrated into light weight structures - e.g. an carbon fiber reinforced aeroplane part or a glass fiber reinforced robot arm - the light weight structures would be severely affected in their advantageous properties. If however, these specific properties are to be maintained, the actuators/sensors have to feature a small volume and stiffness. The micro manufacturing of such systems is an activity of the Fraunhofer Institute IFAM. The approach chosen includes the utilization of piezo electric fibers in the diameter range from 20 micrometers - 200 micrometers . The micro systems consist of many fibers being contacted by interdigitized electrodes made of electrically conductive adhesives. In addition, structural adhesives and casting polymers are used. These actuator/sensor modules can be both applied onto structures, or integrated into structures. The performance of the different modules will be compared. An interesting approach for the use of sensor/actuator modules especially in prepreg fiber reinforced plastics is to also make the PZT fiber modules in a prepreg state. The presentation will feature the latest result of the developments regarding both, the manufacture and the performance of cured as well as prepreg modules.
Piezoceramic thin fibers and sheets of the same nominal chemical composition represent the active materials basis applied in the industrial research project 'Adaptronik' in Germany. Research activities and latest results concerning these Piezoceramic materials are discussed in the paper. Especially, progress has been attained in the PZT fiber technology. Fibers of complex chemical compositions have been prepared by a sol-gel process with diameters smaller than 20 micrometers showing a porefree microstructure with grains of 2-4 micrometers in diameter. The piezoelectric charge constant d33 was nearly doubled in comparison to the undoped PZT fibers. Ceramic sheets have been supplied by CeramTec AG. The integration of PZT-fibers and -sheets into light weight structures made of glass or carbon fiber reinforced composites, may be realized via functional modules, which are tailored as robust sensing, actuating or damping components. The effective properties of these modules are deduced to provide a reliable database in view of the design and the operation of adaptive structures. Additionally, the preparation of 1-3 composites consisting of PZT-fibers and epoxy polymer was successful. This step opens new potentials for the design of advanced ultrasonic transducers. An aspect ration of 30 of the PZT phase in the transducers represents one of the outstanding features.