ReFlex 2


Real-Time Simulation for Flexible Mulit-Body Systems for Machine Control

Exzellenzinitiative SimTech (DFG)

Laufzeit: Oktober 2011 - September 2013


Advanced control concepts are technically capable of providing good disturbance rejection for low damped machines mechatronically, but they have often been rejected by the manufacturing industry because of the strong theoretical background and expert knowledge which is required for their application to practical problems.

A more intuitive approach employs knowledge of a machine’s varying instantaneous properties as scheduling input to controllers with variable parameters. To minimise the effort for acquiring information about the instantaneous properties through measurement and storing the resulting large amounts of data on a machine control, the actual project uses simulation models. Today, simulation models are typically created during the design of a machine. These models are used in the project for the instantaneous calculation of the actual machine behaviour by integrating them into the control device. Several steps to calculate the machine behaviour have been investigated. The developed method contains the following steps: componentwise finite element (FE) model creation, import and configuration on real-time modeller, efficient calculation of instantaneous machine model, system behaviour identification via eigenvalue calculation and trajectory adaptation for vibration suppression.

All methods have been improved to the needs of efficient calculations within the control cycle on a common control device. It can be shown on an example, that a highly efficient calculation of machine properties on the control device can be achieved with almost sufficient accuracy for linear motions. Today it is possible to use this information for a parameterization of advanced trajectory algorithms which suppress effectively vibrations for a machine with no external forces i.e. laser cutters or high bay racking. Future work will have to deal with an improvement of the accuracy, integration of rotary axes and the inclusion of external forces in to the model.

In the prior work modelling techniques have been focussed on the modelling of long distance travels, since all production machines have linear axis. This has been chosen, due to the difficult requirements of linear axes modelling. However, to achieve full modelling abilities, it is necessary to orient the work towards the modelling of rotary axes. Production machines as well as robots use rotary axes. Particularly the robots have the problem of high compliance, whereas the new technique can help to decrease vibrational effects during movements.

The prior work has shown, that especially for linear axes coupling only the classical modal reduction technique can be used to achieve efficient model identification. Nonetheless, one model reduction technique has not been observed practically, whose development has made lots of progress in the last years. These are the so called singular value decomposition (SVD) methods. Here the reduced basis method or the balanced truncation seems to be of favourable for the actual method. Together with the expert on this field Prof. (jun.) Dr.-Ing. Haasdonk from SimTech PN6 and his colleagues, the methods shall be tested, which may be suitable for the here explained techniques.

Typical production machines are used to change the geometry of workpieces. There are milling machines, lathes or drilling machines, which have to apply forces to the workpiece to achieve the geometrical change. Other machines can do this without any external forces like laser cutters or spraying machines. So far in this project only machines, which do not apply forces, have been considered. The method which has been developed in the first funding period cannot integrate external forces so far. In this work packages the method shall be adapted to integrate external forces to the model.