Research On Mechatronic Coupling Of Ball Screw Servo Feed System

Servo feed system is an important part of machine tools, its performance directlyaffect machining precision and efficiency and it’s of great importance improving theirproperties. As a kind of typical mechatronic system, the conventional design methodhas been used in designing servo feed systems which design mechanical structure andcontrol subsystem separately and assemble them when finished. Nevertheless thefunction of servo feed system is a consequence of mutual effect of control subsystemand mechanical subsystem which means there must be some coupling effects in thesetwo subsystems which affect the performance of the whole system. If the couplingeffects can be considered in the design phase, apparent advantages can be found inimproving system performance and working efficiency.First, this paper built a theoretical model of ball screw drive system under theassumption of rigid body of table, screw, nut and so on. Of cause, the ‘rigid body’ hereisn’t meaning that there isn’t any elastic deformation in these components, it meansthat these components deform only in z direction in the coordinate system. By buildingthis model, effects of structure parameters, control parameters and their combinationson servo feed system’s contour err ratio, magnitude margin and bandwidth wereconsidered.Considering the limitations of the theoretical model, such as unable to take lateraldeformation of screw, vibration and mass distribution into consideration, this paperbuilt a finite element model of ball screw drive system. In the FEM model, bearingassembly and nut were not built in solid elements, they were defined by MATRIX27elements based on theoretical calculations in this paper. This will avoid contactscenario which is highly nonlinear and computing-cost. After that, a classic PIDcontroller was integrated into this FEM model. Based on this model, effects of massand their distribution on table were taken into consideration.Finally, an apparatus based on a5-axis modern CNC machine tool developed byHarbin Institute of technology was designed to research the effects of mass distributionof feed table on the system performance, according which the simulation results ofFEM model were verified.