Potential of manipulating the damping properties of parallel kinematic machine tools

Parallel kinematics with a higher end-effector degree of freedom such as hexapods and pentapods consist of a large number of joints and slender struts. However, it is only possible to create comparably low levelsof bearing and strut bending stiffness atreasonable expense due to the limited construction space. That means that these structures are very susceptible to vibration. Even in the low-frequency range they have a large number of relevant eigenmodes that are only dampened slightly. Simultaneously, it is difficult to analyze vibrational properties due to coupled eigenmodes, which also makes it difficult to discover ways to remedy this situation. This article will take the example of a pentapod to analyze the dynamic properties of slightly dampened parallel kinematics by simulation to study potential means of manipulating it. This will include a description of the model formation of the mechanical system. The article will also address ways of reducing model size and using various simulation environments to boost analysis efficiency. Finally, both passive and active strategies will be studied and evaluated for boosting damping. Amongst others it could be shown that it is not necessary to damp every of the five kinematic chains to achieve effective improvement of the system damping behaviour.