Experimental analysis and simulation of nonlinear microscopic behavior of ball screw mechanism for ultra-precision positioning

In this paper, microscopic behavior of a preloaded ball screw supported by ball bearings is discussed based on experimental results and simulation. An experimental apparatus is specially designed and constructed to independently measure the torques of ball screw, ball bearings supporting the screw shaft and driving motor. It is clarified experimentally that the nonlinear microscopic behavior of a positioning mechanism driven by a ball screw is affected not only by the ball screw itself, but also considerably by the ball bearings supporting the screw shaft. Moreover, the ball screw and the ball bearing have their own properties within the deferent limit of the elastic region, and their contribution ratios to the total apparent property of the mechanism change in a complicated manner according to the driving range. To demonstrate the elastic property, a simulation model for the nonlinear microscopic behavior is proposed using a viscous-elastic-plastic model, and procedure of identifying the model parameters is shown. The simulation results on micro-step positioning agree with the experimental results, and the availability of the simulation model proposed is verified. Moreover, the simulation model obtained is compared with previous analytical models of nonlinearity based on elliptic contact under torsion, and the advantage of the proposed model is demonstrated.