Since the early 1970s, structures that can react automatically to a change in external loads or boundary conditions have been investigated in the USA. Mainly the aerospace industry was interested in these developments, as they lead to economic lightweight structures. In the last few years, sustainability and economical lightweight structures have played a major role in construction, which is why adaptive systems are becoming the focus of research. There are various application fields where adaptive systems offer efficient solutions. Mainly the aims are to influence design-decisive peak loads, to homogenize stress states and to reduce deformations.
Adaptivity of structures describes the ability to react automatically to a change in external loads or boundary conditions. This reaction can be carried out in various ways, e.g. changes of geometry, forces or material properties, which can be made by actuators. The control of the actuators requires a sensor system, which is able to detect the effects of the changes on the load-bearing structure. Thereupon a controlled reaction of the actuator system can be executed in order to configure the load-bearing structure optimally for the prevailing situation.
Characterization of adaptive structures
Crucial for the work with adaptive systems is the definition of what an adaptive system exactly is. The required terminology, which is quite different in the fields of mechanical-, control- and civil-engineering, has to be brought together. In order to compare different designs, objective measures to value an adaptive system are needed. They can be calculated using redundancy contributions, gramian controllability matrices or similar. These matrices contain information, which can be used for an optimized placement of actuators in the structure. This is a crucial point in the assessment of the performance of an adaptive structure. Using a suitable actuator placement and control, e.g. stiffness-governed design tasks can be transferred into strength-governed tasks. For example, in the design of high-rise or wide spanned structures, the design decisive results can be deformations or accelerations in the structure. A well-designed adaptive structure is able to manipulate those quantities in order to reduce the amount of matter significantly, which is needed in the primary structure to comply with constraints.
Modelling of the actuation
The focus in this research area is the modelling and simulation of adaptive systems. To carry out an exact analysis, which represents the behaviour of the adaptive structure realistically, the actuators, sensors and control technology must be integrated into the model. This is also beneficial in the development of algorithms that control the system. Towards an efficient simulation of adaptive structures using the finite element method, suitable finite actuator elements are defined.
Teilprojekt B01 - Charakterisierung, Modellierung und Reduktion adaptiver Tragwerke
German Research Foundation (DFG), Collaborative Research Centre SFB 1244 "Adaptive Hüllen und Strukturen für die gebaute Umwelt von morgen", GEPRIS project number 324663295
Institute of Engineering and Computational Mechanics (ITM), University of Stuttgart
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