Modeling and Frictional Behaviours Analysis of Digital Servo Stepping Hydraulic Cylinder System

To analyze the frictional behaviours of hydraulic seals of a kind of digital servo stepping hydraulic cylinder used in 6-Dof motion simulator, the mathematical model, including 2-phase hybrid stepping motor, slide valve and mechanical feedback mechanism, and valve-controlled asymmetric cylinder, is set up. Friction observer is constructed based on LuGre friction model and applied in the numerical simulation. Simulation results show that hydraulic seals made of polyurethane materials may cause creeping and dithering motions in low velocity.