Modeling and analysis on stick-slip friction course of spherical micromanipulator

3-DOFs rotations of spherical micromanipulator were achieved by relative displacement and frictions between the ruby balls and the micro-ball on the top of piezoelectric tubes. The stick-slip effects existed in this friction movement. The two-mass-oscillator equivalent engineering model of the spherical micromanipulator was established under the condition of simplifying spherical higher pair joints. The stick-slip course was divided into four phases and the dynamics models of phases were set up based on equivalent engineering model and LuGre friction model. The parameter feature curves were analyzed by numerical simulation. The experiments were also done, and the validity of the analysis was further proved by the results.