Enhanced Nonlinear PID Controller for Positioning Control of Maglev System

Magnetic levitation (maglev) is a way of using electromagnetic fields to levitate objects without any noise or the need for petrol or air. Due to its highly nonlinear and unstable behavior, numerous control solutions have been proposed to overcome it. However, most of them still acquire precise dynamic model parameters, or deep understanding of control theory. To account the complexity in the design procedure, a practical controller consists of classical and modern control approaches are proposed. This chapter presents a practical controller for high positioning performance of a magnetic levitation system. Three strategies of the proposed controller where the PI-PD controller is to enhance transient response, the model-based feedforward control (FF) is incorporated with the PI-PD controller to enhance the overshoot reduction characteristic in attaining a better transient response, and lastly the disturbance compensator (Kz) is integrated as an additional feedback element to reduce the sensitivity function magnitude for robustness enhancement. The proposed controller - FF PI-PD + Kz has a simple and straightforward design procedure. The usefulness of the proposed controller is evaluated experimentally

Controller Design for Magnetic Levitation System

Magnetic Levitation is a method by which an object is suspended in air by means of magnetic force. Earnshaw stated that static arrangements of magnet cannot levitate a body. The exception comes in case of diamagnetic and superconducting materials and by controlling magnetic field by control method. Diamagnetic materials or superconducting materials when placed in magnetic field produce magnetic field in opposite direction. Here the problem of controlling the magnetic field by control method is taken up to levitate a metal hollow sphere. The control problem is to supply controlled current to coil such that the magnetic force on the levitated body and gravitational force acting on it are exactly equal. Thus the magnetic levitation system is inherently unstable without any control action. It is desirable to not only levitate the object but also at desired position or continuously track a desired path. Here a linear and two nonlinear controllers are designed for magnetic levitation system. First a robust adaptive backstepping controller is designed for the system and simulated. The simulation results shows tracking error less than 0.0001m. The immeasurable state present is estimated by Kreisselmeier filter. The Kreisselmeier filter is a nonlinear estimator as well as preserves the output feedback form. However the control output is too high. To counteract the above problem Nesic backstepping controller is designed for the system by taking Euler approximate model of the system. The controller output is well within the range of 0.5~1 voltage. The reference tracking is also verified in simulation and the tracking error comes in range of 0.00015m. A linear controller is also designed for MagLev system as the region of operation of magnetic levitation setup is too small. A two degree freedom (2DOF) PID controller is designed satisfying a desired characteristics equation. The controller parameters are obtained by pole placement technique. The 2DOF PID controller is simulated and experimentally validated and it is seen that better result are obtained in 2DOF PID than 1DOF PID controller

Adaptive Control

Adaptive control has been a remarkable field for industrial and academic research since 1950s. Since more and more adaptive algorithms are applied in various control applications, it is becoming very important for practical implementation. As it can be confirmed from the increasing number of conferences and journals on adaptive control topics, it is certain that the adaptive control is a significant guidance for technology development.The authors the chapters in this book are professionals in their areas and their recent research results are presented in this book which will also provide new ideas for improved performance of various control application problems

Deterministic Artificial Intelligence

Kirchhoff’s laws give a mathematical description of electromechanics. Similarly, translational motion mechanics obey Newton’s laws, while rotational motion mechanics comply with Euler’s moment equations, a set of three nonlinear, coupled differential equations. Nonlinearities complicate the mathematical treatment of the seemingly simple action of rotating, and these complications lead to a robust lineage of research culminating here with a text on the ability to make rigid bodies in rotation become self-aware, and even learn. This book is meant for basic scientifically inclined readers commencing with a first chapter on the basics of stochastic artificial intelligence to bridge readers to very advanced topics of deterministic artificial intelligence, espoused in the book with applications to both electromechanics (e.g. the forced van der Pol equation) and also motion mechanics (i.e. Euler’s moment equations). The reader will learn how to bestow self-awareness and express optimal learning methods for the self-aware object (e.g. robot) that require no tuning and no interaction with humans for autonomous operation. The topics learned from reading this text will prepare students and faculty to investigate interesting problems of mechanics. It is the fondest hope of the editor and authors that readers enjoy the book

FLUX-PINNED DYNAMICAL SYSTEMS WITH APPLICATION TO SPACEFLIGHT

Technology enables space exploration and scientific discovery. At this amazing intersection of time, new software and hardware capabilities give rise to daring robotic exploration and autonomy. Close-proximity operations for spacecraft is a particularly critical portion of any robotic mission that enables many types of maneuvers, such as docking and capture, formation flying, and on-orbit assembly. These dynamic maneuvers then enable different missions, like sample return, spacecraft construction larger than a single rocket faring, and deep-space operations. Commonly, spacecraft dynamic control uses thrusters for position and attitude control, which rely on active sensing and consumable propellant. The development of other dynamic control techniques opens new capabilities and system advantages, and further offers a more diverse technological trade space for system optimization. This research comprehensively investigates the utilization of flux-pinning physics to manipulate spacecraft dynamics. Flux-pinned interfaces differ from conventional dynamic control through its passive and compliant behavior. These unique characteristics are extremely attractive for certain applications, but flux-pinned technology must mature considerably before adoption for spaceflight missions. A dynamic capture and docking maneuver in an upcoming mission concept, Mars Sample Return, motivates the technology design. This body of work as much as possible follows a progression from cradle to grave. A flux-pinning theoretical dynamics model and a system architecture are presented to specify general capabilities of such a spacecraft system. Different analyses on stability, state sensitivity, backwards reachability result from a physics-based dynamics model. An extensive literature review and basic science experiments inform a theoretical dynamics model about the incorporation of physical parameters when simulating realistic dynamics. A series of testbeds enable experimentation and precise investigation of flux-pinned interface capabilities in the context of docking and capture. The testbeds ranged from the simplest expression of dynamics, in a single degree of freedom, to a flight traceable expression, in all six degrees of freedom. Experiments from these testbeds define and characterize system level capabilities specific to flux-pinned capture. Data collected from these experiments then supports development of a predictive dynamics model of the hardware system. Various system identification methods aid in creating a dynamics model that accurately predicts the dynamics observed during experiments. Several objective metrics are considered to evaluate the model fidelity. The types of system identification methods are separated into analytical methods and numerical methods. The analytical method involves parameter estimation in a physics-based model. Numerical methods involve Taylor expansion, bag of functions, symbolic regression, and neural networks. Theoretical extensions towards verification further develops neural network approximation methods, driving at safe, real-time system identification

Design and Optimal Control of a Magnet Assisted Scanning Stage for Precise and Energy Efficient Positioning

Scanning stages are characterized by repeated back and forth motions and are widely used in advanced manufacturing processes like photo-lithography, laser-scribing, inspection, metrology, 3D printing, and precision parts assembly, many of which are closely related to the semiconductor (i.e., integrated circuit) manufacturing industry. In order to deliver more high- performance semiconductor chips, i.e., to keep up with predictions made by Moore’s Law, the scanning stages employed by the industry need to move faster while maintaining nanometer-level precision. Achieving these two goals simultaneously requires extensive use of thermal and vibration-induced error mitigation methods, because the motors, and subsequently the surrounding stage components, become heated and flexible parts of scanning stages are easily excited by their aggressive motions (with high acceleration/deceleration). Most of the available solutions tackle the heat and vibration mitigation problems separately, even though the two problems originate from one source, i.e., the large inertial loads generated by the scanning stage’s actuators. Much benefit (e.g., size and cost reductions) can be achieved by considering the two problems simultaneously by addressing their root cause. This dissertation proposes a design-based approach to simultaneously mitigate thermal and vibration-induced errors of scanning stages. Exploiting the repeated back-and-forth motions of scanning, permanent magnet (PM) based assist devices are designed to provide assist force needed during the motion reversal portions of scanning trajectories. The PM-based assist devices store the kinetic energy of the moving table during deceleration and release the stored energy when the table accelerates. Consequently, the force requirements of the primary actuator decrease, thus lowering its heat generation due to copper (resistive) losses. Moreover, the reaction forces borne by the PM assistive devices are channeled to the ground, bypassing the vibration isolated base upon which the scanning stage rests, thus reducing unwanted vibration. To increase the force density of the PMs, a 2D Halbach arrangement is adopted in a prototype scanning stage. Moreover, an efficient and low-cost servo system, optimized for versatility, is integrated into the scanning stage for automatic positioning of the PMs. The designed magnet assisted scanning stage is an over-actuated system, meaning that it has more control inputs than outputs. For the best utilization of its actuators, a feedforward approach for optimal allocation of control efforts to its actuators is developed. The stage, controlled with the optimal feedforward control inputs, achieves significant reductions of actuator heat and vibration-induced errors when applied to typical scanning motions used in semiconductor manufacturing (silicon wafer processing). To further improve the positioning accuracy of the stage, an Iterative Learning Control (ILC) approach for over-actuated systems is developed, exploiting the repeated motion of scanning stages. The optimal ILC update law is designed, considering model and input force uncertainties, for robust monotonic convergence of tracking errors, and the resultant control force is efficiently allocated to multiple actuators. Applied to the magnet assisted scanning stage, the proposed ILC approach additionally reduces tracking errors arising from the mismatch between the model and actual system, thus significantly improving the positioning accuracy of the stage.PHDMechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/149847/1/yydkyoon_1.pd

Third International Symposium on Magnetic Suspension Technology

In order to examine the state of technology of all areas of magnetic suspension and to review recent developments in sensors, controls, superconducting magnet technology, and design/implementation practices, the Third International Symposium on Magnetic Suspension Technology was held at the Holiday Inn Capital Plaza in Tallahassee, Florida on 13-15 Dec. 1995. The symposium included 19 sessions in which a total of 55 papers were presented. The technical sessions covered the areas of bearings, superconductivity, vibration isolation, maglev, controls, space applications, general applications, bearing/actuator design, modeling, precision applications, electromagnetic launch and hypersonic maglev, applications of superconductivity, and sensors