A Friction Model-Based Frequency Response Analysis for Frictional Servo Systems

This paper presents a friction model-based frequency response analysis (FRA) method, which gives a precise linear mechanical dynamics model to design effective controllers and analyze accurate control characteristics for frictional servo systems. As well known, frequency-domain identification approaches using a sine sweep are widely used to obtain linear dynamics. However, nonlinear friction in the mechanism varies the apparent frequency-domain characteristic of the linear dynamics due to the nonlinearity. The proposed FRA estimates effective excitation thrust for actual linear dynamics in the sine sweep movement, by means of a friction model as well as a phase delay model. Theoretical analyses show that the proposed FRA can identify the correct linear dynamics, preventing influence of nonlinear friction as well as phase delay properties included in a plant system. The effectiveness of the proposed FRA is verified through theoretical analyses and experiments both in frequency and time domains, in comparison to two conventional FRA methods.