Dynamic properties of feed drive significantly influence precision of path control. Common simulation models of feed drives simplify mechanical structure of the machine tool to two mass models, in which reduced masses of the feed drive mechanical part and machine frame are connected with a spring. However, such way of modelling does not consider both the dynamic properties of machine frame and does not allow searching for the most effective setup and optimization of the feed drive and choice of its components in the early design phase.
It is obvious, that each of the components in the drive inclusive the machine frame has to be modelled properly in order to relevantly simulate the behaviour of a real machine. Appropriate complex model of machine mechanical structure is a key component of coupled mechatronical models, which include the interaction of machine structure with servodrive loops and by means of which dynamic properties of the drive can be predicted, relevant tests of drive control performed and implementation of new functionalities, like e.g. smart filtering, feedforwarding or algorithms for path generation investigated. Recently, more approaches to advanced feed drive coupled modelling are developed by various research workers. In the advanced models, mechanical structure of the machine is represented either with rigid Multi-Body Systems (MBS), reduced FEM description of the whole structure or flexible Multi-Body Systems. The last strategy makes use of seprate FEM modelling of each of the machine compliant parts, which are in specialized software environment linked together by means of flexible kinematical joints, thanks to which long movements can be simulated. However, MBS-like simulation of long movements can also be achieved based on one general FEM model of the whole machine tool.
Author: Ing. Matej Sulitka, PhD. www.rcmt.cvut.cz
