Stability Analysis Of Flexible Rotor Supported By Active Hybrid Bearing With Fuzzy Logic-Based Control

The classic film hydrodynamic bearing is a passive device, and its design does not consider the adaptive capacity to change with operation conditions. The film journal bearing coupling with servo valve, fuzzy PD controller, and sensor, called active hybrid bearing with fuzzy logic–based control (AHBF), can accept controllable orifice flow to produce active force for reducing the rotor vibration. The AHBF is modeled as a couple of four parts: controller, servo valve, orifice flow, and film. The orifice flow is modeled as the series of a servo valve, capillary restrictor, and gap restrictor. The spool motion of the servo valve is modeled as a second-order transfer function and controlled by the fuzzy PD controller. The governing equation of film pressure is a modified Reynolds equation containing the orifice flow. The results indicate that the proportional coefficient significantly affects the bearing load capacity and the max increment of the minimum film thickness can be 271%. The dynamic coefficients of the AHBF are calculated using the orbit analysis method. The results indicate that the stiffness and damping of the bearing can be increased by up to 403% and 74% under active control. Compared with passive operation, the amplitude of the unbalance respone at the bearing can be reduced by 67% in active control operation. In conclusion, the AHBF has better static and dynamic characteristics than hydrodynamic bearing. Besides, the rotor supported by the AHBF has lower vibration than passive operation.