Approaches to control of the large angle magnetic suspension test fixture

The Large Angle Magnetic Suspension Test Fixture is a five degree-of-freedom system, developed and built at NASA Langley Research Center. It is intended for study of control techniques in magnetic suspension systems with large angular capabilities. In this study, steps have been taken to prove the system in practice, using the existing hardware. A classical control approach, using dual phase advance compensators, is applied in simulation and hardware. A single decoupled degree-of-freedom of the system is stabilized and controlled in simulation. The procedure is then employed for all five degrees-of-freedom. The design and implementation of an analog and a digital controller are described. Results from simulation and the actual system are compared and analyzed. The ability to the system to sustain suspension over a large angular range has been proven in hardware

De-Centralized and Centralized Control for Realistic EMS Maglev Systems

A comparative study of de-centralized and centralized controllers when used with real EMS Maglev Systems is introduced. This comparison is divided into two parts. Part I is concerned with numerical simulation and experimental testing on a two ton six-magnet EMS Maglev vehicle. Levitation and lateral control with these controllers individually and when including flux feedback control in combination with these controllers to enhance stability are introduced. The centralized controller is better than the de-centralized one when the system is exposed to a lateral disturbing force such as wind gusts. The flux feedback control when combined with de-centralized or centralized controllers does improve the stability and is more resistant and robust with respect to the air gap variations. Part II is concerned with the study of Maglev vehicle-girder dynamic interaction system and the comparison between these two controllers on this typical system based on performance and ride quality achieved. Numerical simulations of the ODU EMS Maglev vehicle interacting with girder are conducted with these two different controllers. The de-centralized and centralized control for EMS Maglev systems that interact with a flexible girder provides similar ride quality

Full-order observer design for a class of port-Hamiltonian systems

We consider a special class of port-Hamiltonian systems for which we propose a design methodology for constructing globally exponentially stable full-order observers using a passivity based approach. The essential idea is to make the augmented system consisting of the plant and the observer dynamics to become strictly passive with respect to an invariant manifold defined on the extended state-space, on which the state estimation error is zero. We first introduce the concept of passivity of a system with respect to a manifold by defining a new input and output on the extended state-space and then perform a partial state feedback passivation which leads to the construction of the observer. We then illustrate this observer design procedure on two physical examples, the magnetic levitation system and the inverted pendulum on the cart system. (C) 2010 Elsevier Ltd. All rights reserved.</p

Symmetry in Electromagnetism

Electromagnetism plays a crucial role in basic and applied physics research. The discovery of electromagnetism as the unifying theory for electricity and magnetism represents a cornerstone in modern physics. Symmetry was crucial to the concept of unification: electromagnetism was soon formulated as a gauge theory in which local phase symmetry explained its mathematical formulation. This early connection between symmetry and electromagnetism shows that a symmetry-based approach to many electromagnetic phenomena is recurrent, even today. Moreover, many recent technological advances are based on the control of electromagnetic radiation in nearly all its spectra and scales, the manipulation of matter–radiation interactions with unprecedented levels of sophistication, or new generations of electromagnetic materials. This is a fertile field for applications and for basic understanding in which symmetry, as in the past, bridges apparently unrelated phenomena―from condensed matter to high-energy physics. In this book, we present modern contributions in which symmetry proves its value as a key tool. From dual-symmetry electrodynamics to applications to sustainable smart buildings, or magnetocardiography, we can find a plentiful crop, full of exciting examples of modern approaches to electromagnetism. In all cases, symmetry sheds light on the theoretical and applied works presented in this book

Modeling and control of electromechanical systems

The material presented in the these notes covers the sessions Modelling of electromechanical systems, Passive control theory I and Passive control theory II of the II EURON/GEOPLEX Summer School on Modelling and Control of Complex Dynamical Systems. We start with a general description of what an electromechanical system is from a network modelling point of view. Next, a general formulation in terms of PHDS is introduced, and some of the previous electromechanical systems are rewritten in this formalism. Power converters, which are variable structure systems (VSS), can also be given a PHDS form. We conclude the modelling part of these lectures with a rather complex example, showing the interconnection of subsystems from several domains, namely an arrangement to temporally store the surplus energy in a section of a metropolitan transportation system based on dc motor vehicles, using either arrays of supercapacitors or an electric powered flywheel. The second part of the lectures addresses control of PHD systems. We first present the idea of control as power connection of a plant and a controller. Next we discuss how to circumvent this obstacle and present the basic ideas of Interconnection and Damping Assignment (IDA) passivity-based control of PHD systems

Decoupling Control of a Disc-type Rotor Magnetic Bearing

A disc-type rotor magnetic bearing with 3-pole magnet is considered in the paper. Based on analysing magnetic forces acting on the rotor, a coupling mechanism is identified, and a coordinate transformation is formulated to decouple acting forces. Thanks to the transformation, control design is straightforward for each control channel. The goal of the design is to keep the rotor at its desired equilibrium in the presence of disturbance and parameters variation. To achieve this goal, the controller is designed in discrete-time domain based on the linearized model first. Then, the disturbance is compensated by employing the one step delay technique. The validity and robustness of the controller are verified by various numerical simulations in which both linearized model and original nonlinear model are used

Magnetically levitated planar actuator with moving magnets

Mechanical systems with multiple degrees of freedom typically consist of several one degree-of-freedom electromechanical actuators. Most of these electromechanical actuators have a standard, often integrated, commutation (i.e. linearization and decoupling) algorithm deriving the actuator inputs which result in convenient control properties and relatively simple actuator constraints. Instead of using several one degree-of-freedom actuators, it is sometimes advantageous to combine multiple degrees of freedom in one actuator to meet the ever more demanding performance specifications. Due to the integration of the degrees of freedom, the resulting commutation and control algorithms are more complex. Therefore, the involvement of control engineering during an early stage of the design phase of this class of actuators is of paramount importance. One of the main contributions of this thesis is a novel commutation algorithm for multiple degree-of-freedom actuators and the analysis of its design implications. A magnetically levitated planar actuator is an example of a multiple degree of freedom electromechanical actuator. This is an alternative to xy-drives, which are constructed of stacked linear motors, in high-precision industrial applications. The translator of these planar actuators is suspended above the stator with no support other than magnetic fields. Because of the active magnetic bearing the translator needs to be controlled in all six mechanical degrees of freedom. This thesis presents the dynamics, commutation and control design of a contactless, magnetically levitated, planar actuator with moving magnets. The planar actuator consists of a stationary coil array, above which a translator consisting of an array of permanent magnets is levitated. The main advantage of this actuator is that no cables from the stator to the translator are required. Only coils below the surface of the magnet array effectively contribute to its levitation and propulsion. Therefore, the set of active coils is switched depending on the position of the translator in the xy-plane. The switching in combination with the contactless translator, in principle, allows for infinite stroke in the xy-plane. A model-based commutation and control approach is used throughout this thesis using a real-time analytical model of the ironless planar actuator. The realtime model is based on the analytical solutions to the Lorentz force and torque integrals. Due to the integration of propulsion in the xy-plane with an active magnetic bearing, standard decoupling schemes for synchronous machines cannot be applied to the planar actuator to linearize and decouple the force and the torque components. Therefore, a novel commutation algorithm has been derived which inverts the fully analytical mapping of the force and torque exerted by the set of active coils as a function of the coil currents and the position and orientation of the translator. Additionally, the developed commutation algorithm presents an optimal solution in the sense that it guarantees minimal dissipation of energy. Another important contribution of this thesis is the introduction of smooth position dependent weighing functions in the commutation algorithm. These functions enable smooth switching between different active coil sets, enabling, in principle, an unlimited stroke in the xy-plane. The resulting current waveform through each individually excited active coil is non-sinusoidal. The model-based approach, in combination with the novel commutation algorithm, resulted in a method to evaluate/design controllable topologies. Using this method several stator coil topologies are discussed in this thesis. Due to the changing amount of active coils when switching between active coil sets, the actuator constraints (i.e. performance) depend on the xy-position of the translator. An analysis of the achievable acceleration as a function of the position of the translator and the current amplifier constraints is given. Moreover, the dynamical behavior of the decoupled system is analyzed for small errors and a stabilizing control structure has been derived. One of the derived coil topologies called the Herringbone Pattern Planar Actuator (HPPA) has been analyzed into more detail and it has been manufactured. The stator of the actuator consists of a total of 84 coils, of which between 15 and 24 coils are simultaneously used for the propulsion and levitation of the translator. The real-time model, the dynamic behavior and the commutation algorithm have been experimentally verified using this fully-operational actuator. The 6-DOF contactless, magnetically levitated, planar actuator with moving magnets (HPPA) has been designed and tested and is now operating successfully according to all initial design and performance specifications

An LQR controller design approach for a Large Gap Magnetic Suspension System (LGMSS)

Two control approaches for a Large Gap Magnetic Suspension System (LGMSS) are investigated and numerical results are presented. The approaches are based on Linear Quadratic Regulator (LQR) control theory and include a nonzero set point regulator with constant disturbance input and an integral feedback regulator. The LGMSS provides five degree of freedom control of a cylindrical suspended element which is composed of permanent magnet material. The magnetic actuators are air core electromagnets mounted in a planar way