Shape memory alloys (SMA) like Nickel-Titanium possess a very high mechanical energy density in relation to
conventional drives. Fiber reinforced plastics (FRP) will be increasingly applied to create lightweight structures.
Combining both innovative materials will evolve synergy effects. Due to functional integration of SMA sheets into a
base of FRP it is possible to realize adaptive composites for resource-efficient constructions as for instance flaps or
spoilers on cars. For this purpose the interaction between SMA as an actuator and FRP as a return spring need to be
designed in a suitable way. The computation of such structures is complex because of its non-linear (SMA) and
anisotropic (FRP) mechanical behavior. Therefore, a structural simulation model based on the finite element method was
developed by means of the software ANSYS. Based on that simulation model it is possible to determine proper
geometrical parameters for a composite made of SMA and FRP to perform a certain mechanism. The material properties
of SMA or FRP could also be varied to investigate their influence. For exemplary components it could be shown that the
stress-strain behavior is computable.
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 presents a mechatronic strategy for active reduction of vibrations on machine tool struts or car shafts. The
active structure is built from a carbon fiber composite with embedded piezofiber actuators that are composed of
piezopatches based on the Macro Fiber Composite (MFC) technology, licensed by NASA and produced by Smart
Material GmbH in Dresden, Germany. The structure of these actuators allows separate or selectively combined bending
and torsion, meaning that both bending and torsion vibrations can be actively absorbed. Initial simulation work was
done with a finite element model (ANSYS). This paper describes how state space models are generated out of a
structure based on the finite element model and how controller codes are integrated into finite element models for
transient analysis and the model-based control design. Finally, it showcases initial experimental findings and provides
an outlook for damping multi-mode resonances with a parallel combination of resonant controllers.
This paper reports a numerical and experimental study on a new multi mode vibration reduction concept for struts of machine tools or shafts of automotives. The example described in detail validates this new concept for high dynamic parallel kinematic struts. The structural advantages of parallel kinematic mechanisms are undisputed. However statical and dynamical bending and torsional loads must be considered during the design process of the structure and thus effect the shape of the strut geometry. The here described new actuator concept for multi mode vibration reduction is to influence these bending and torsional loads. It uses piezopatches based on the MFC technology licensed by NASA. Initial simulation and experimental tests were done at an one side clamped aluminium beam with applicated 45°-MFC's on both sides. Simulation results show, that driving the piezos in opposite direction leads to a bending deflection of the beam, driving them in the same phase leads to a torsional deflection of the aluminium beam. Experimental measurements confirm the simulation results. The benefit we get is a decreased number of actuators for multimode vibration reduction. Likewise these actuators allow the separation or selective combination of bending and torsion. This new actuation concept is not limited on beams. Further simulations for cylindrical struts result in a design of a MFC-ring with eight segments with changing fiber orientation for separation of bending and torsion on struts and shafts. The selective controlled activation of each of the segments leads to bending in x-direction, bending in y-direction or torsion.
This paper reports an experimental study on active vibration reduction for automotive shafts with the use of piezoelectric material. The work focuses on an axle of an Audi A2. The demand in the automobile sector for higher comfort in the vehicle is of a great importance alongside the requirements of lighter weight and low fuel consumption. These requirements are typically in conflict with each other. One solution is the use of intelligent materials instead of viscoelastic materials and proof mass absorbers. These solutions are quite heavy especially at low frequencies. Active vibration control and piezoelectric devices are advantageous in this application due to their low mass to performance ratio. Our research study explores the use of such piezoelectric devices for an axle. In conjunction with electronics it will reduce vibrations in the first natural bending mode of the axle. Laboratory tests simulated the condition present in the road. At first a stationary set up was used, then a simulated disturbance was input at the attachment points of the shaft. Finally, a test with rotating shaft was performed. Piezoelectric devices (custom QuickPacks from ACX, a Division of Cymer) were used as sensors and as actuators to properly control the axle during the different operating conditions. The power consumption of each actuator pair was less than 20W. The work described here details the test setup, the control strategy, the hardware implementation as well as the test results obtained.