Shuliang Lei

Large motion tracking control for thrust magnetic bearings with fuzzy logic, sliding mode, and direct linearization

Abstract Conventional use of magnetic bearings relies on a zero reference to keep the rotor centered in the radial and axial axes. This paper compares different control methods developed for the alternate control task of tracking an axial dynamic target. Controllers based on fuzzy logic, sliding mode, and direct linearization were designed to meet this task. Performance criteria, such as maximum axial displacement, minimum phase lag and I 2 R power losses were compared for each controller. The large motion, tracking problem for a rotor has utility in applications where dynamic seal clearances are required. This has a variety of potential applications in turbo-machinery, such as active stall control.

Hierarchical fuzzy logic control of a double inverted pendulum

This paper uses dynamical hierarchical control to stabilize a double inverted pendulum. Hamiltons principle is introduced to build the dynamic model of the system. The double inverted pendulum is decomposed into subsystems. Fuzzy logic controllers are designed for each subsystem at the lower level of the hierarchy. At the higher level a fuzzy logic based coordinator is developed to supervise the complete system. Computer simulation using the Matlab fuzzy logic Toolbox compares the fuzzy logic controller with conventional state feedback control and shows the advantages of employing FLC as well as the advantage of the hierarchical control.

Fuzzy Logic Intelligent Control System of Magnetic Bearings

This paper presents a fuzzy logic based intelligent control system applied to magnetic bearings. The core in the expert system is fuzzy logic controllers with Mamdani architecture. The fuzzy logic controllers for rub detection and automatic gain scheduling were implemented. The expert system not only provides a means to capture the run time data of the magnetic bearings, to process and monitor the parameters, and to diagnose malfunctions, but also protects the magnetic bearings from rub anomaly and implements the control on a real time basis.

Fail Safe, High Temperature Magnetic Bearings

This paper contributes to the magnetic bearing literature in two distinct areas: high temperature and redundant actuation. Design considerations and test results are given for the first published combined 538°C (1000°F)-high speed rotating test performance of a magnetic bearing. Secondly, a significant extension of the flux isolation based, redundant actuator control algorithm is proposed to eliminate the prior deficiency of changing position stiffness after failure. The benefit of the novel extension was not experimentally demonstrated due to a high active stiffness requirement. In addition, test results are given for actuator failure tests at 399°C (750°F), 12,500rpm. Finally, simulation results are presented confirming the experimental data and validating the redundant control algorithm.Copyright

An approach to synthesis and approximation of stable fuzzy logic controllers

This paper studies the method for synthesizing stable fuzzy controllers and the approximation in terms of Mamdani model to stabilize nonlinear systems. A stability criterion for determining the feedback control coefficients is given based on Takagi-Sugeno model. It is shown that by suitably partitioning the universe of discourse of the output membership functions, the defuzzified function surface can have at most limited number of points equal to those of a given surface. This result is then used to approximate a controller via Mamdani model and an algorithm for deriving such a stable fuzzy logic controller is detailed. An inverted pendulum is taken as example to demonstrate the methodology developed in this paper.

MAGNETIC BEARING DEVELOPMENT FOR SUPPORT OF SATELLITE FLYWHEELS

The use of magnetic bearings (MB) for support of space based flywheels can provide significant improvement in efficiency due to reduction in drag torque. A NASA supported program directed through the Texas A&M Center for Space Power has been formed to advance the technology of MB’s for satellite flywheel applications. The five areas of the program are: (a) Magnetic Field Simulation, (b) MB controller Development, (c) Electromechanical Rotordynamics Modeling, (d) Testing and (e) Technology Exchange. Planned innovations in these tasks include eddy current drag torque and power loss determination including moving conductor effects, digital (DSP) based control for high speed operation, MATLAB-based coupled flexible rotor/controller/actuator electromechanical model with fuzzy logic nonlinear control, and ultra high speed>100 krpm measurement of drag torque. The paper examines these areas and provides an overview of the project.

Real Time Digital Control of Magnetic Bearings with Microprocessors

This paper presents the work on the real time implementation of digital controllers applied to magnetic bearings to levitate high speed rotor systems. Microprocessor is employed for digital signal processing. The control loop consists of PID controller, tracking and fixed notch filters, lead compensators, and feedforward stage, etc. The controller is implemented with TI TMS320C67 processor incorporated with LabVIEW data acquisition and graphical user interface. Digital signal processing techniques including bilinear transformation, frequency pre-warping, digital filter design and I/O communications are applied to implement the control rule. The real time controller has been successfully applied to the levitations of a revolver test rig in Vibration Control Lab at Texas A&M and the energy storage flywheel system used by industries for vehicles

Flywheel magnetic suspension developments

The authors provide an overview of many areas of the flywheel magnetic suspension (MS) R&D being performed at the Texas A&M Vibration Control and Electromechanics Lab (TAMU-VCEL). This includes system response prediction, actuator optimization and redundancy, controller realizations and stages, sensor enhancements and backup bearing reliability.

Fail Safe, High Temperature Magnetic Bearing for High Efficiency Gas Turbine Engine Applications

This paper contributes to the magnetic bearing literature in two distinct areas: high temperature and redundant actuation. Design considerations test results are given for the first published combined 538°C (1000°F)-high speed rotating test performance of a magnetic bearing. Secondly, a significant extension of the flux isolation based, redundant actuator control algorithm is proposed to eliminate the prior deficiency of changing position stiffness after failure.Copyright

Implementation of Magnetic Suspension Control With FPGA

This paper presents a methodology for an alternative implementation of DSP-based controllers typically used for magnetic bearing (MB) levitation and control on FPGA hardware. The approach takes s-domain transfer functions of the controller components and discretizes them using z-transform conversions into discrete time domain expressions. These expressions, which are essentially digital IIR filters, are synthesized and implemented to obtain downloadable bit-stream using Xilinx ISE software packages. In the example presented, the executable code was sent to configure the two FPGAs for control. An equivalent PD with notch filter FPGA-based controller was constructed to replicate an existing two-axis DSP controller used to control a radial magnetic bearing on a vertical rotor in the Dynamic Spin Rig Facility at NASA Glenn Research Center. The FPGA controller was successfully demonstrated on the NASA hardware.