Modeling of pivot friction using relay function and estimation of its frictional parameters

One way of modeling frictional effects that arise from pivot ball bearing in rotary disk drive actuator requires a special experimental setup. In this paper, a revised model from two-slope and three-slope model with omission of first slopes from both position and velocity feedback and an addition of relay, is presented. The hysteresis characteristics of ball bearing are much more accurately described by a relay added on the velocity feedback. For parametrization, a mathematical description of the frictional relay is obtained, and both linear and nonlinear terms in the friction model are treated simultaneously by using conventional recursive-least-square method incorporating a new technique that extracts V_th threshold parameter. The effectiveness of the new friction model is tested by a parameter estimation scheme, and simulation and experiment of the estimation algorithm are also demonstrated for overall performance