REAL-TIME ESTIMATION OF TEMPERATURE DISTRIBUTION IN A BALL-SCREW SYSTEM

A ball screw is usually preloaded for high rigidity and accuracy, thus increasing the frictional resistance. Subsequently its temperatures a nd positioning error are significantly raised. When it comes to high s peed or high precision, this thermal error becomes more serious and do minates the total error. In this paper, two-dimensional temperature di stributions of a ball-screw system preloaded in the axial direction ar e estimated at various moving velocities and stop times by the finite element method (FEM). The thermal behavior of the ball screw was measu red for comparison with the data estimated by FEM. The comparison show s that the pattern of temperature increase and the temperature distrib ution of the ball screw in a steady state are well estimated, whereas the absolute values of the temperature are not well estimated in spite of a long computation time. Therefore a modified lumped method is pro posed for the real-time estimation of the temperature distribution for the ball screw. This method, after compensation for heat transfer coe fficients, estimates the temperature more exactly than FEM within seve ral milliseconds, which makes practical implementation feasible. (C) 1 997 Elsevier Science Ltd.