Further Results on Active Magnetic Bearing Control with Input Saturation

We study the low-bias stabilization of active magnetic bearings (AMBs) subject to voltage saturation based on a recently proposed model for the AMB switching mode of operation. Using a forwarding-like approach, we construct a stabilizing controller of arbitrarily small amplitude and a control-Lyapunov function for the AMB dynamics. We illustrate our construction using a numerical example.Comment: 9 pages, 2 figures. IEEE Transactions on Control Systems Technology, accepted for publication in January 200

Minimization of power losses in active magnetic bearing control

A solution to the problem of AMB control with reduced electrical power losses will be presented in this thesis. The proposed control solution will be founded on the integrator backstepping technique, which decouples the rotor stabilization problem from the bias flux design problem. It further allows for the easy redesign of the control law to compensate for uncertainties in the AMB system. A class of nonlinear controllers will be developed that reduces the AMB power losses in comparison to standard fixed-bias controllers, while containing no control singularity. Control laws will be presented for the standard AMB operating mode where both electromagnets are active at all times, as well as for the “energy-saving” operating mode where only a single electromagnet is active at any given time. The main contribution of this work is the development of a smart bias flux, and function of the rotor position and velocity. General conditions motivated by physical and mathematical properties are developed for the functional form of the bias, ensuring the reduction of power losses and the avoidance control singularities without affecting the closed-loop system stability. Simulation results also illustrate the interesting role the smart bias plays in stabilizing the rotor. Note that while the power loss discussion in this thesis is focused on ohmic losses, the proposed control strategies also help reduce eddy current- and hysteresis-induced losses due to their proportionality to the magnetic flux

Experimental validation of a smart-bias active magnetic bearing controller

Active magnetic bearings (AMBs) are being increasingly employed in the aerospace industry in a variety of devices including compressors, turbines, pumps, and flywheels. One application of great interest to future space missions is the Integrated Power and Attitude Control System (IPACS). The IPACS consists of an arrangement of flywheels that integrates the energy storage and attitude control functions into a single system; thereby, reducing the spacecraft mass, volume, launching cost, and maintenance. Like any energy storage system, flywheels need to be operated with low power losses. AMBs are ideally suited for flywheels because they eliminate mechanical losses (friction). Nevertheless, AMBs are subject to electrical losses, which are proportional to the bias flux. We recently developed an innovative solution to the problem of AMB control with reduced electrical power losses. The controller incorporates a smart, time-varying bias flux that reduces power losses without affecting the rotor stabilization. The novelty of the smart-bias controller strongly motivated the pursuit of the next step in this research – an experimental validation. To that end, the objectives of this project were: · Design and build an experimental AMB test rig. · Conduct tests to validate the smart-bias controller and its power-loss reduction mechanism in comparison to a standard constant-bias AMB controller. The experimental results show that the smart-bias controller clearly reduces the electrical power losses and energy dissipation of the AMB system in comparison to the constant-bias approach, without significantly affecting the stabilization performance. These results confirm, in a qualitative manner, the theoretical and numerical results obtained earlier

A conventional point of view on active magnetic bearings

Active magnetic bearings used in rotating machinery should be designed as locally controlled, independent devices similar to other types of bearings. The functions of control electronics and power amplifiers can be simply and explicitly related to general bearing properties such as load capacity, stiffness, and damping. The dynamics of a rotor and its supporting active magnetic bearings are analyzed in a modified conventional method with an extended state vector containing the bearing state variables

Further results on active magnetic bearing control with input saturation

We study the low-bias stabilization of active magnetic bearings (AMBs) subject to voltage saturation based on a recently proposed model for the AMB switching mode of operation. Using a forwarding-like approach, we construct a stabilizing controller of arbitrarily small amplitude and a control-Lyapunov function for the AMB dynamics. We illustrate our construction using a numerical example. © 2006 IEEE

Realization of coordination technology of hierarchical systems in design of active magnetic bearings system

A cybernetic technology of mechatronic design of active magnetic bearings systems (AMB) originated from theory of systems is suggested in the paper. Traditional models of artificial intelligence and mathematics do not allow describing mechatronic systems being designed on all its levels in one common formal basis. They do not describe the systems structure (the set of dynamic subsystems with their interactions), their control units, and do not treat them as dynamic objects operating in some environment. They do not describe the environment structure either. Therefore, the coordination technology of hierarchical systems has been chosen as a theoretical means for realization of design and control. The theoretical basis of the given coordination technology is briefly considered. An example of technology realization in conceptual and detailed design of AMB system is also presented

Fadaptive Backstepping Control of Active Magnetic Bearings

A new control methodology, adaptive backstepping control (ABC), is applied to a linearized model of an active magnetic bearing (AMB). Our control objective is to regulate the deviation of the magnetic bearing from its equilibrium position in the presence of an external disturbance. The control approach is based on adaptive backstepping control, which is a combination of a recursive Lyapunov controller and adaptive laws. In this thesis, two types of adaptive backstepping methods are used. The first method is based on full-state feedback, for which all three states in the linearized AMB model (velocity, position, and current) are used to construct the control law. The second method is adaptive observer-based backstepping control (AOBC) where only one feedback signal (position) is employed. An exponentially convergent estimator is developed for the second adaptive controller to observe other states. It is proved that the adaptive backstepping controlled AMB system is asymptotically stable around the system\u27s equilibrium point. Simulation results demonstrate fast and stable system response. They also verify the effectiveness and robustness of the adaptive backstepping control methods against external disturbances and system parameter variation

Magnetic Bearings

The term magnetic bearings refers to devices that provide stable suspension of a rotor. Because of the contact-less motion of the rotor, magnetic bearings offer many advantages for various applications. Commercial applications include compressors, centrifuges, high-speed turbines, energy-storage flywheels, high-precision machine tools, etc. Magnetic bearings are a typical mechatronic product. Thus, a great deal of knowledge is necessary for its design, construction and operation. This book is a collection of writings on magnetic bearings, presented in fragments and divided into six chapters. Hopefully, this book will provide not only an introduction but also a number of key aspects of magnetic bearings theory and applications. Last but not least, the presented content is free, which is of great importance, especially for young researcher and engineers in the field

Reduced order modeling and sliding mode control of active magnetic bearing

Due to the accelerated growth in the field of power electronics and controller design techniques, the usage of the active magnetic bearing has picked up in industries. Active magnetic bearing helps the rotor to rotate freely without any physical contact. In brief, this paper develops a model of an active magnetic bearing using the finite element method, and its associated reduced order model, followed by the development of a robust control strategy. COMSOL software is used to perform three-dimensional simulation of an active magnetic bearing system. The state space system matrices are extracted from the finite element method, and a linear time-invariant state-space system is generated in MATLAB. Since the original system is large, the reduced order model is constructed. Then, based upon the reduced order model, a sliding mode control is designed to improve the regulation performance of an active magnetic bearing under unmodeled uncertainties. The stability analysis of closed-loop reduced order model with unmodeled uncertainties guarantees the finite time convergence of system states using Lyapunov theory. Further, it is proved that the same control law will also provide satisfactory performance for the original model using the reduced order model as an observer. The numerical simulation is carried out to illustrate the effective performance of the proposed controller for the reduced model as well as the original model with multiple initial conditions. The proposed work offers an alternative approach of using the reduced order model instead of the original model for the controller design of an active magnetic bearing.This publication was made possible by Qatar University High Impact Research Grant # [QUHI-CENG-19/20-2] from the Qatar University. The publication charges are funded by the Qatar National Library, Doha, Qatar.Scopu

International Symposium on Magnetic Suspension Technology, Part 1

The goal of the symposium was to examine the state of technology of all areas of magnetic suspension and to review related recent developments in sensors and controls approaches, superconducting magnet technology, and design/implementation practices. The symposium included 17 technical sessions in which 55 papers were presented. The technical session covered the areas of bearings, sensors and controls, microgravity and vibration isolation, superconductivity, manufacturing applications, wind tunnel magnetic suspension systems, magnetically levitated trains (MAGLEV), space applications, and large gap magnetic suspension systems