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unilogo University of Stuttgart
Institute of Engineering and Computational Mechanics

Modular, autonomous adaptive compensation of vibrations
in machine-tools with truss structures


Project Description

The growing demand for highly productive machine tools, which are able to move rapidly and accurately along a prescribed trajectory, results in the development of new machine types such as parallel and hybrid kinematics and accompanying the use of new technologies such as linear drives and lightweight constructions. Together with these new concepts different motion control strategies are needed as the use of nonlinear differential equations of motion becomes necessary due to the high velocities and large movements of the machine. Moreover, the usual assumption of independently controllable drives becomes questionable. Furthermore, due to the lightweight structures and the desired high dynamics the elastic properties of machine components become important. Hence, hierarchical controllers combining nonlinear control with methods of active vibration damping are a promising concept to achieve the desired system performance.

The here examined system is a high performance machine tool with linear drives and lightweight strucutures for processing of plate-like workpieces, e.g. milling of large wooden plates). The machine tool has been build at the Institute of Machine Tools at the University of Stuttgart, Germany. It is a hybrid kinematic consisting of a scissors-like parallel part for the motion in the xy-plane and a serial axle for the motion in z-direction.

The scope of the project is to develop - based on an elastic multibody system model - a control concept for active vibration damping, which is going to be implemented at the machine tool in addition to the position control system. Before the actual implementation simulation studies are carried out in order to understand the vibrational behaviour of system and to efficiently test the effects of different control concepts as modal, wave- or flatness-based strategies. Together with nonlinear position controllers (e.g. flatness-based) in a hierarchical control concept the active vibration damping is an interesting concept to improve the overall system performance. The project is a cooperation between the Institut for Machine Tools (IfW) of Prof. Heisel and the Institute for Engineering and Computational Mechanics. Experimental works are conducted at the IFW, modelling, simulation and the various controller designs at the Institute for Engineering and Computational Mechanics.

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