Today in the production of internal combustion engines it is possible to make pistons as well as cylinders, for all
practical purposes, perfectly round.
The negative consequences of the subsequent assembly processes and operation of the engine is that the
cylinders and pistons are deformed, resulting in a loss of power and an increase in fuel consumption.
This problem can be solved by using an adaptronic tool, which can machine the cylinder to a predetermined nonround
geometry, which will deform to the required geometry during assembly and operation of the engine.
The article describes the actuatory effect of the tool in conjunction with its measuring and controlling algorithms.
The adaptronic tool consists out the basic tool body and three axially-staggered floating cutter groups, these
cutter groups consist out of guides, actuators and honing stones. The selective expansion of the tool is realised by
3 piezoelectric multilayer-actuators deployed in a series - parallel arrangement.
It is also possible to superimpose actuator expansion on the conventional expansion. A process matrix is created
during the processing of the required and actual contour data in a technology module.
This is then transferred over an interface to the machine controller where it is finally processed and the setting
values for the piezoelectric actuators are derived, after which an amplifier generates the appropriate actuator
voltages. A slip ring system on the driveshaft is used to transfer the electricity to the actuators in the machining
The functioning of the adaptronic form-honing tool and process were demonstrated with numerous experiments.
The tool provides the required degrees of freedom to generate a contour that correspond to the inverse compound
contour of assembled and operational engines.
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.
The most important project in sheet metal forming is streamlining the material flow since each rejects increases production costs. Using the multipoint cushion device together with an elastic blankholder makes it possible to actively manipulate the material flow in the flange range. This allows major enhancements in the deformation ratio, especially with the novel high strength materials in car body production. State-of-the-art is multiple draw pins to initiate the force on selected points on the blankholder. Admittedly, the cushion plate does not allow optimum force allocation because it is situated between hydraulic pressure rollers and draw pins. Replacing selected draw pins with piezoactuators for generating high forces allows systematic control of the force progression at critical forming areas during sheet draw-in. The system, consisting of the piezostack actuator, dynamometer and components for force initiation, was built as a compact unit with low resilience with the intension of using the inherent sensory properties of the piezostack actuator to measure force. Applying this principle throughout allows a reduction of hydraulic components which eventually lead to a less expensive one- point cushion device.
Initial finding have already been arrived at in the context of a research project at the Fraunhofer Institute for Machine Tools and Forming Technology in Chemnitz, Germany in cooperation with a partner from the automobile industry. A draw pin was replaced ad hoc with a highly durable piezoactuator integrated in a force control cycle. The force progression during the sheet draw-in could be accurately adjusted according to a predetermined master curve. The master curve was taken up in the unregulated process and represents the quality criteria of a formed useable part. The real-time MATLAB Simulink XPC- Target simulation tool was used to develop an adjustment strategy that connects the specific signals of the press control (such as the tappet path, the die cushion position and the die cushion force) with the reference force (i.e., the master curve) and the actual force of the piezoactuator.
The structural advantages of parallel kinematic mechanisms for highly dynamic motions are undisputed. The mass values to be moved are essentially determined by the structure of the end effector platform. The accuracy of machines with parallel kinematic drive concepts is decisively defined by the joint and feed unit assemblies. Statical (except in hexapods) and dynamical bending and torsional loads limit the shape of the strut geometry. As a rule, an increase in volume to enhance stiffness at the same times results in an increase in weight and thus worse dynamic characteristics. Active compensation and damping elements provide an alternative to passively increasing stiffness by geometries fitted to load. An active compensation of torsion is aimed at achieving a high "virtual" torsional stiffness of the whole drive unit by means of a compensation drive which is based on piezoelectric actuators. The compensation drive works autonomously and measures and corrects the appearing torsional deformation in a self-controlled manner, independent of the end effector platform' s position in the working space adjusting feed units.