The Structural Mechanics and Dynamics Branch has successfully demonstrated a fail-safe controller for the Fault-Tolerant Magnetic Bearing rig at the NASA Glenn Research Center. The rotor is supported by two 8-pole redundant radial bearings, and coil failing situations are simulated by manually shutting down their control current commands from the controller cockpit. The effectiveness of the controller was demonstrated when only two active coils from each radial bearing could be used (that is, 14 coils failed). These remaining two coils still levitated the rotor and spun it without losing stability or desired position up to the maximum allowable speed of 20,000 rpm.
This demonstration disproved the existing fault-tolerant control theory, which cannot solve the distribution matrix of reduced flux density for the case of just two coils. A significant amount of real-time noise levels were calculated by using a moving average (MA) filter and a programmable S-function block. Also, a centralized modal controller was demonstrated to better control the dynamic behavior over system modes. A graphical-user-interface-based control cockpit and a whirling feature to investigate gyroscopic effects were also demonstrated.
This extremely valuable demonstration could help to ease the controversial safety issue of magnetic suspension technology for advanced high-speed rotating turbomachinery in case of system faults in the main bearing components. A simple PID controller generated autonomous corrective actions for the failed coil situations without losing the load capacity to meet the NASA mission of doing things faster, better, and cheaper.
Glenn contacts: Dr. Benjamin B. Choi, 216-433-6040, Benjamin.B.Choi@grc.nasa.gov; and Andrew J. Provenza, 216-433-6025, Andrew.J.Provenza@grc.nasa.gov
Authors: Dr. Benjamin B. Choi and Andrew J. Provenza
Headquarters program office: OAT
Programs/Projects: TCT, FESS
Last updated June 6, 2001, by Nancy.L.Obryan@nasa.gov
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