Adaptronic concept

The scope of the application of adaptronic structures or systems can be restricted as the spectrum of influential scientific disciplines. Almost each scientific field covers applications, whose technical benefit and business management utility can be improved by realizing adaptronic concepts. While the need for efficient multifunctional materials certainly originates in the high-technology area, the scope of application is by no means exclusively confined to this field. For example, multifunctional adjusting elements of shape memory alloys are successfully applied for the automatic control of ventilation flaps in greenhouses. 

However, even products resulting from highly specialized materials are only partially needed for the realization of efficient adaptronic concepts. Simple adaptive systems, with a minimal number of elements in motion, are of special importance in a surrounding field, where the protection against shortfalls is a decisive factor and where little or no well-trained staff are available for the removal of technically complex problems. The broad range of applications covers a number of areas where adaptronic concepts have been intensively pursued and partially have already been translated into concrete action. The specific interest shown in a particular line of business is a result... 

This section focuses on the application of adaptronic concepts in machine tools and manufacturing plants. Such concepts are applied to improve the performance of the machines. Experts agree that machine tools of high performance stand out because of their excellent product quality, high processing speed, as well as reliability and flexibility when different tools and materials must be processed. 

In the following, the author will introduce some implementation examples for each of the above mentioned fields of research and development, illustrating the potential of adaptronic concepts for different machine tools and manufacturing methods. Naturally, this section cannot be exhaustive, but rather must be limited to methods of cutting manufacturing. Since many of the implementation examples are not process specific, this section will provide the reader with a good overview on the state of the art, and he will find many suggestions that will help him to develop his own concepts. 

Functional qualities can, however, only be used in terms of adaptronics if there is success in combining the specific release phenomena with the respective desired functions. What is therefore required in the conception of multifunctional elements (level II) is the release and specific use of the material-inherent options. For this purpose it is necessary to make use of release phenomena of a physical, chemical or biological nature on material in such a way that, as necessary, several effects can be combined by taking well-directed action. For example, the application of electrorheological fluids... 

Materials represent the essential basis for all multifunctional effects. The conception of multifunctional elements is therefore mainly based on the made-to-measure production of functional materials, wherein several functions are interlinked at a molecular level. However, the fact that this is not sufficient in all cases is clearly shown by taking adaptronic shock absorbers as an example, because some effects can only be produced if several materials are combined in suitable interconnected layers or other compounds. 

Adaptronics as an overall concept for the development of adaptronic structures and systems is still a young discipline, which was only able to establish itself a few years ago. On the other hand, the research in the fields of multifunctional materials and multifunctional elements, which are the basic elements of adaptronics, started much earlier. The origins of adaptronics under a different name - go back to the early 1980s. Early progress came from the arms research sector, especially from various air forces. 

In 1992, the first govermnent funded projects were incorporated by the German Ministry of Research and Technology in its material research program. These projects initially concentrated on the improvement of pure material functions. However, it quickly proved necessary to enlarge the basic area of materials and to develop integrated concepts for multifunctional adaptive structures or systems in terms of adaptronics. In this context the objective was the application-orientated optimization of functional materials and their functional integration in a system. 

The efficiency and proper positioning of actuators and sensors in adaptronic systems can be analysed using the concepts of controllabihty and observability. To make the basic ideas more clear, adaptronic structures are taken as an example. Loosely speaking, controllability and observabihty also mean that the actuator force and sensor vectors are not orthogonal and preferably parallel to the relevant vector (e. g. natural mode) or state to be controlled or observed. 

Adaptronics and control can be implemented at different points or subsystems. In order to evaluate possible concepts from a system point of view, an overall end to end model is established. The elements of such an integrated simulation model are shown in Fig. 5.3. In the left part the reduced structure (dynamics) model together with control laws are used for assessing the effects of active damping introduced by adaptronics as described below. The right part contains the optical submodel together with the telescope drives. 

Among several applications in space and machine tools, a nice application has been developed using this concept the active damping of a ski [19]. The first flexural vibration mode of the ski occurring at 14 Hz is actively damped (the initial quality factor of 100 is decreased down to 10) through a piezo actuator and an accelerometer (Fig. 6.26a). A special filter is necessary to avoid instabilities coming from the high order vibration modes. The piezo actuator is mounted in front of the shoe and the accelerometer is mounted at the top of the ski. This implementation is an important step to the adaptronic application, in which it is foreseen to adapt the quality factor of the ski as a function of the snow hardness. 

Since the early days of adaptronics aeronautics and space travel has been a most significant player in driving adaptronics ahead. A large amount of work was done along concept studies which ended up in partially even showing hardware demonstration at full scale very recently. Adaptronics in aeronautics can be split into the following areas of activity ... 

Adaptronics for rotorcraft was very much driven by concepts in the early 1990s looking at rotor blade twist to improve aerodynamic performance as well as reduction of the negative drawbacks of lead lag damping. Individual blade control has become key in rotorcraft technology and it became quickly... 

One adaptronic approach to reduce torsional vibrations was to integrate actuators within the diagonal stiffening struts of the car underbody (Fig. 8.24) [150,151]. Different actuators have been investigated, piezoceramic stacks, hydraulic cylinders and hydraulic muscles. Control approaches like adaptive feed-forward and feedback were implemented and significant vibration reductions were achieved (Fig. 8.24). To commercialize this affirmative active concept system cost, size, complexity and power consumption must be further reduced. 

So far, adaptronic systems have mainly been applied in aeronautics and space travel, see Sect. 8.1, but hardly ever in commercial machine tools and manufacturing plants, which means that most of the concepts and experiences described here result from research projects conducted at institutions of higher learning. For many years, these institutions have applied such systems in their experimental set-ups. 

Active Damping and Reduction of Structural Oscillations. Under this heading, the research groups develop fundamental concepts of optimized positioning and integrating adaptronic components (actuators, sensors) in machine tool structures. Research focuses on approaches and implementations that will reduce structure-born noise by means of control techniques. 

The concept of active control - a first step to adaptronics in civil structures - is an attempt to make structures behaviour more like aircraft, machinery, or human beings in the sense that they can be made adaptive or responsive to external loads. 

---