Adaptronics

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Adaptive Systems ( portmanteau of adap tive and electronics electronics ) is an interdisciplinary science that deals with the development of adaptive (self-adjusting), actively reacting mechanical structure systems is concerned. In contrast to mechatronics , the actuators used in adaptronics are integrated directly into the force flow and use the elastomechanical properties of the materials used .

Meaning and history

Adaptronics has been researched in the USA since the early 1980s under the term Smart Structures or Smart Materials , initially with the aim of realizing variable, i.e. H. adaptable satellite structures for the SDI project.

For example, the active control of the shape of reflectors or the vibrations and deformations of frameworks were examined . The aim was to actively compensate for the effects of changing environmental conditions on the mechanical structures (for example the thermomechanical stresses on the lightweight structures as a result of the highly variable solar radiation in the earth's shadow or in the case of direct irradiation or the changes in mechanical properties of the aging satellite structures during long periods of operation).

In Germany , the focus was on this technological approach - initially in the field of basic research and then applied R&D - about 10 years later . Various experts attribute a rapidly increasing role in modern products to smart material systems and adaptronics. Due to the inherent complexity of the technology, they would mean that it would be more difficult to copy the products and that high-tech locations would have a competitive edge . As an obstacle to the widespread commercial use of adaptronics, series users in particular often cite excessively high costs for adaptronics components and the resulting adaptronics end products. However, great progress has been made in this area in recent years, also thanks to related technology developments and products such as u. G. Piezo diesel direct injection.

Multifunctional basic materials

Most of the materials used in adaptronic systems can be used both as actuators and sensors . In this sense, these materials have two functions. Since the idea of ​​adaptronics involves direct mechanical intervention in structures, which consists of integrating the materials into the mechanical load paths of structures, the actuator and sensor functions are supplemented by this third, mechanically load-bearing function. As a result, the basic materials preferably used in adaptronics are also called multifunctional.

These multifunctional materials are characterized by the fact that they convert electrical , thermal or other energy into mechanical energy . Consequently, these materials are also called transducer materials or energy converters, in Anglo-Saxon also transducers . In adaptronics, especially those transducer materials are used in which the non-mechanical form of energy (for example the electrical) can be technically controlled or evaluated particularly well.

With certain of these materials, this energy conversion can take place reciprocally in both directions. The best-known and much-cited example is the piezoelectricity of certain materials. In these, the action of mechanical pressure leads to a shift of electrical dipoles and the formation of electrical charges on electrodes attached to the piezo . The resulting electrical voltage can be detected and evaluated by sensors. Application examples for this piezoelectric effect in everyday life are electric lighters, in the technical field piezoelectric sensors such as force, acceleration or strain sensors. The inverse piezoelectric effect, which corresponds to a deformation of the piezo material as a result of the application of an electrical voltage, is used as an actuator. This effect is used in acoustic generators as loudspeaker tweeters, signal generators, etc. In addition, a wide variety of actuator designs for generating positions and vibrations are available on the commercial market.

In addition to the piezo materials, the most common materials in adaptronics are the so-called shape memory alloys . These are usually activated thermally, but also magnetically in certain alloy compositions. The thermal shape memory alloys are used in surgery for stents which are intended to expand and keep open blood vessels and which are activated by body heat. In addition, they are used - usually in wire form - for compact, simple actuators (for example the Bowden cable principle ) or for switching, sometimes very fast locking systems. The latter, for example, is currently being developed for reversible car crash actuators as a supplement to airbags - advantage: the shape memory material can be reversibly controlled, compared to pyrotechnic airbag actuators, and can thus be used repeatedly and thus for pre-crash applications.

Further, magnetostrictive materials used, for example, as actuators in sonars of ships or in adaptive vibration absorbers . In addition, fluids are used that change their viscosity through the application of electrical ( electrorheological fluids ) or magnetic fields ( magnetorheological fluids ) . These fluids are used, for example, in hydraulics and in shock absorbers in vehicle construction or sports equipment.

Functional principle and application examples

In order to demonstrate the functional principle of adaptronics and to develop new processes and methods, bars with bonded piezo film actuators, also called piezo patches, are often used. Here vibrations of the beam can be greatly reduced by suitable control of the piezo patches. The transfer to applications such as skin areas of machine cladding, noise protection cabins, facade elements such as windows , rotor blades of helicopters, booms in robotics and vertical stabilizers of military aircraft is quite obvious and an ongoing part of application-oriented research. Purely as an actuator, this principle of the piezo bending beam is used, for example, in textile machines with high numbers and a very long service life.

Another typical demonstration object is a water glass with an adaptronic interface underneath, which in turn is mounted on a vibrating substructure. If the actuators built into the interface are controlled appropriately, the water in the glass can be kept calm despite the interfering vibrations acting under it and the interface. This example can be equated with an actively deformable screw connection. Application examples are active bearings for the assembly of machines on foundations (e.g. machines in factories or ship units that are supposed to work with low vibration and interference), the connection of clamping plates with sensitive structures mounted on them in the laboratory , the storage of sensitive optical components or the connection the body on a car chassis . This is also used in the development of adaptive structures . Discrete actuators such as B. Piezo multilayer used. Actuators of this type are currently very well known as mass products from the field of piezo diesel injection technology. Here, too, a very high, proven reliability of the actuators is of great importance.

Requirements for the adaptronic system development

In addition to competence in the field of materials, sensor and especially actuator design such as structural mechanics and mostly structural dynamics - this to achieve the adaptronic mechanical target function, for example for the active control of vibrations, noise or deformation - is essential for the efficient design and implementation of such a system especially the modeling and simulation of components and especially complex systems is essential. This simulation must bring together the various system components such as actuators, sensors, mechanical structure, electronics such as filtering, control code and the mechanical environmental conditions that affect them. Methods and tools from the FEM ( Finite Element Method ), MKS ( multi-body simulation ), CACE (Computer Aided Control Engineering) or RCP ( Rapid Control Prototyping ), EDA ( Electronic Design Automation ), CAD (computer -aided design) as well as the EMA (Experimental Modal Analysis ), the TPA (Transfer Path Analysis, see transfer function ), the operational vibration analysis and many others. The simulation is used for system analysis, testing and evaluation of possible solution concepts such as performance assessment. Since the adaptronics is principally aimed at the integration of functions into the mechanical load paths, it is important to take into account the strong feedback of the various system components among each other in the simulation. In order to optimize the effort for the modeling, simulation and thus the design of the adaptronic systems - as already indicated above with the methods and tools - the use of both numerical and experimental methods and procedures for modeling is recommended. In addition, competencies in control engineering, electronics, code design, system integration , manufacturing and processing technology and reliability are of essential importance for adaptronics.

This in particular also against the background of the implementation of a system that is particularly optimized for the respective application. A large-scale technical solution, such as that used in the automotive sector , will be assessed differently than a special solution in plant construction or space travel. In addition to the fulfillment of the target function and the achievable performance of an adaptronic system, the reproducible costs and reliability will always be decisive. The use of cost-intensive, powerful control electronics with maximum system performance and special functions for a high-end special application will be desirable if this results in decisive salable advantages in the end product, but cannot be argued for a mass product in the consumer sector.

Adaptronics project teams are very often made up of scientists and engineers in mechanical engineering from various fields of application and in mechanics, construction, lightweight construction, materials science, control engineering, electrical engineering, computer science, physics, and mathematics.

Remarks

  1. A load path is the "path" that the force takes in the event of an impact.

literature

Web links

Individual evidence

  1. Johannes Michael Sinapius: Adaptronics. Principles - functional materials - functional elements - target areas with research examples . Springer Vieweg, Braunschweig 2018, ISBN 978-3-662-55883-6 .