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ROMAC Rotating Machinery and Controls Laboratory |
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Magnetic Bearings Chatter Control with Active Magnetic Bearing Student,: Min Chen Advisor: Carl R. Knopse Project Start Date: September 1999 Sponsor: National Science Foundation Project Objectives: Develop a controller using active magnetic bearing in the cutting process to achieve high metal removal rates free from chatter. The magnetic bearing control must be tuned for the particular parameters of the cutting condition as well as the delay. This may be achieved via the use of the new control synthesis techniques of implicit gain scheduling. Progress in the Past Year: We built an experiment rig with a magnetic actuator for the chatter control experiment. Every part of the rig was tested and modeled. Simulations of the models match well with the experiment results. Now the experiment rig is running stably with a PD controller. controllers are also synthesized based on model uncertainties and performance requests. This experiment rig will be much helpful in the studying cutting dynamics and controller performance evaluation. Self-Sensing Magnetic Bearings Student: Dominick Montie Advisor: Eric Maslen Project Start Date: Fall, 1993 Report Numbers: 387, 397, 414 Project Objectives: The objective of this research is to develop a high-performance method of rotor position estimation using the magnetic actuator itself, without the use of discrete position sensors. The primary benefits of this technology are increased reliability and decreased space requirements. Increased reliability is achieved by reduced wire and part count in the bearing environment, as well as incorporation with actuator fault tolerance1. Decreased space requirements (primarily axial rotor length) result from eliminating the necessary rotor sections used as position sensor targets. This has the added benefit of reducing rotor flexibility and the control effort and complexity needed to compensate for these dynamics. Progress in the Past Year: Our test rig consists of a rigid rotor supported by two axial magnetic bearings and one thrust bearing. For spin tests, we use an air turbine flexibly coupled to the shaft. Our signal processing circuitry used for the position estimation is implemented in analog electronics. Last fall, we designed and built modular printed circuit boards to increase electronics ruggedness and adaptability, and to decrease signal noise. This spring, we successfully implemented our self-sensing method on both axes of one axial bearing with the rotor spinning at 60,000 RPM1. Our current theoretical efforts are focused on characterizing the effect of actual hardware nonlinearities on achievable estimator performance. 1See our project web page (http://www.people.virginia.edu/~dtm7e/research.html) for a downloadable version of a technical paper which provides a detailed discussion of this.
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