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3 Machine Dynamics Problems

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Vibrations in Electrical Tools

100%

Eiber A. , Yan S.

Machine Dynamics Problems

2001

tom Vol. 25, No. 3/4

55-64

In handheld electrical tools like grinding machines a high rotation speed of the motor is needed to get the demanded power and a low weight. A gear reduces the rotation of the working speed of grinding or cutting tool. Important demands from the user are low weight and a limited vibration level of the tool's housing to avoid the white-finger-syndrome. To fulfil these requirements, an analysis of the dynamical behaviour has to be carried out. Models based on the Multibody Systems approach are used including the elastic shaft with the armature lamination core, the commutator and the winding. The adjacent structures of the rotor like compliant bearings, gear and carbon brushes are also considered to describe their dynamical interaction with the rotor. In order to get the belonging parameters and to evaulate the dynamical properties of the handheld tools measurements using contactless Laser-Doppler-Vibrometry and accelerometers have been conducted. Simulations and measurements show strogly coupled vibrations between the rotor structure itself and the djacent structures. Mechanisms for failures in the wires of armature and communication sparkling causing burn-out of carbon brushes as weel as high vibration level could be found and eliminated.

Middle Ear Reconstructions : A Mechanical View

100%

Eiber A. , Freitag H. G.

Machine Dynamics Problems

2000

tom Vol. 24, No. 1

63-77

For the development of optimal passive and active middle ear implants a precise mathematical description of hearing process is necessary. Mechanical models are suitable for a proper description of the sound transfer through the middle ear. They offer a clear insight into the complex dynamical behavior and allow a physical interpretation of the phenomena. The procedures and the powerful tools developed for machine dynamics can be successfully applied to the problems in hearing. In a first step the problems are analyzed from the mechanical point of view. Based on three-dimensional mechanical models the normal and impaired hearing is described. Depending on the particular investigation different models have to be generated to give a precise answer. Two realizations of active hearing aids are considered as examples. It is shown, how the frequency-dependent transfer functions are influenced by changing the driving principle and some desing parameters like additional mass attached to the ossicles, position and orientation of the actuator and coupling conditions.

A Mechatronic Solution Design and Experience with Large Gearless Mill Drives

70%

Kümmlee H. , Möhle A. , Meinke P. , Eiber A. , Koch E.

Machine Dynamics Problems

2001

tom Vol. 25, No. 3/4

107-120

In the mineral processing industry the use of large gearless cycloconverter drive systems for SAG-Mills has become more and more common in the recent years. Very high power ratings with excellent dynamic performance and high efficiency over a wide speed range allow advanced optimization of the process. The design of such large mill drive systems requires modern simulation tools to verify the system behavior. An optimized design must take into account the mechatronic interaction between all individual mechanical and electrical components. Calculation methods and related design targes must be defined in a very early stage of the project to allow simultaneous engineering.