Control Method of Heavy Hydrostatic Thrust Bearing

Abstract

A hybrid fuzzy control scheme was applied to improve the rigidity of hydrostatic thrust bearing. The bearing oil film control was realized by coupling oil film thickness of four controllable chambers. The chamber flow can be regulated by electro hydraulic servo valve-control variable pump according to the surface roughness, load, cutting force, and thermal effects of worktable. The nonlinear hybrid controller developed was composed of a classical PID controller and a fuzzy controller based on self-adjusting modifying factor, and feed-forward compensation was added. A fuzzy switching mode was employed to avoid the undesirable disturbances caused by the switchover between the two control methods. By simulations and experiments on an electro-hydraulic servo test bench the feasibility of the control scheme was validated by comparison with a PID and a conventional fuzzy control. The research results show that the hybrid fuzzy controller exhibit good dynamic and steady quality, eliminate oil film lubrication failure and be broadly applied in high precision heavy machine tool.