Electromagnetic fields and interactions in 3D cylindrical structures : modeling and application

The demand for more efficient and compact actuation systems results in a search for new electromagnetic actuator configurations. To obtain actuators that meet these challenging specifications, accurate modeling of the electromagnetic fields is often a prerequisite. To date, analytical modeling techniques are widely used to predict electromagnetic fields in classical rotary and linear machines represented in two dimensional coordinate systems. This thesis presents the extension of an analytical modeling technique to predict the 3D field distribution in new cylindrical actuator configurations. One specific technique that is used to analyze and design electromagnetic devices is based on Fourier series to describe sources and the resultingmagnetic fields. In this research, the harmonic modeling technique is extended to describe electromagnetic fields due to presence of permanent magnets in regular and irregular shaped 3D cylindrical structures. The researched modeling technique can be applied to current-free cylindrical problems exhibiting periodicity or a soft-magnetic boundary in the axial direction. The cylindrical structure can posses either circumferential slots, axial slots or rectangular cavities. The assignment and a method to solve the various boundary conditions are discussed in a generic manner to enable model application to a wide range of 3D cylindrical structures. The magnetic field solutions are provided, and the model implementation is presented in matrix form. Model validation is presented by means of a comparison of the magnetic fields in a cylindrical structure with a rectangular cavity calculated using the analytical model and a finite element model. To calculate the magnetic interactions, e.g., attraction and cogging forces due to permanent magnets, the Maxwell stress tensor is analytically evaluated. The harmonic magnetic field solution is used in this evaluation resulting in compact force equations describing the 3D force components between concentric cylinders

Generalized harmonic modeling technique for 2D electromagnetic problems : applied to the design of a direct-drive active suspension system

The introduction of permanent magnets has significantly improved the performance and efficiency of advanced actuation systems. The demand for these systems in the industry is increasing and the specifications are becoming more challenging. Accurate and fast modeling of the electromagnetic phenomena is therefore required during the design stage to allow for multi-objective optimization of various topologies. This thesis presents a generalized technique to design and analyze 2D electromagnetic problems based on harmonic modeling. Therefore, the prior art is extended and unified to create a methodology which can be applied to almost any problem in the Cartesian, polar and axisymmetric coordinate system. This generalization allows for the automatic solving of complicated boundary value problems within a very short computation time. This method can be applied to a broad class of classical machines, however, more advanced and complex electromagnetic actuation systems can be designed or analyzed as well. The newly developed framework, based on the generalized harmonic modeling technique, is extensively demonstrated on slotted tubular permanent magnet actuators. As such, numerous tubular topologies, magnetization and winding configurations are analyzed. Additionally, force profiles, emf waveforms and synchronous inductances are accurately predicted. The results are within approximately 5 % of the non-linear finite element analysis including the slotted stator effects. A unique passive damping solution is integrated within the tubular permanent magnet actuator using eddy current damping. This is achieved by inserting conductive rings in the stator slot openings to provide a passive damping force without compromising the tubular actuator’s performance. This novel idea of integrating conductive rings is secured in a patent. A method to calculate the damping ratio due to these conductive rings is presented where the position, velocity and temperature dependencies are shown. The developed framework is applied to the design and optimization of a directdrive electromagnetic active suspension system for passenger cars. This innovative solution is an alternative for currently applied active hydraulic or pneumatic suspension systems for improvement of the comfort and handling of a vehicle. The electromagnetic system provides an improved bandwidth which is typically 20 times higher together with a power consumption which is approximately five times lower. As such, the proposed system eliminates two of the major drawbacks that prevented the widespread commercial breakthrough of active suspension systems. The direct-drive electromagnetic suspension system is composed of a coil spring in parallel with a tubular permanent magnet actuator with integrated eddy current damping. The coil spring supports the sprung mass while the tubular actuator either consumes, by applying direct-drive vertical forces, or regenerates energy. The applied tubular actuator is designed using a non-linear constrained optimization algorithm in combination with the developed analytical framework. This ensured the design with the highest force density together with low power consumption. In case of a power breakdown, the integrated eddy current damping in the slot openings of this tubular actuator, together with the passive coil spring, creates a passive suspension system to guarantee fail-safe operation. To validate the performance of the novel proof-of-concept electromagnetic suspension system, a prototype is constructed and a full-scale quarter car test setup is developed which mimics the vehicle corner of a BMW 530i. Consequently, controllers are designed for the active suspension strut for improvement of either comfort or handling. Finally, the suspension system is installed as a front suspension in a BMW 530i test vehicle. Both the extensive experimental laboratory and on-road tests prove the capability of the novel direct-drive electromagnetic active suspension system. Furthermore, it demonstrates the applicability of the developed modeling technique for design and optimization of electromagnetic actuators and devices

THREE-DIMENSIONAL STEADY STATE AND TRANSIENT EDDY CURRENT MODELING

Maglev transportation using electrodynamic wheels is a promising new technology aimed at providing a low cost, high-speed and environmental friendly mode of transportation. In this technology, Halbach permanent magnet rotors, termed electrodynamic wheels, are simultaneously rotated and translationally moved above a conductive non-magnetic guideway. The time-changing magnetic field created in the airgap between the rotors and guideway induces eddy currents in the guideway which in turn interact with the magnetic rotor field to produce suspension and propulsion or braking forces which are required for maglev transportation. This technology offers an integrated suspension and propulsion system. In this dissertation the eddy current distribution in the conductive guideway has been modeled in three-dimension. An approach for the computation of the static magnetic fields due to the Halbach rotor has been presented using novel magnetic charge sheet concept. Finite element models have been developed to study the steady state and transient eddy current field distribution. Three analytic models have been developed to compute the electromagnetic forces and torque acting on the rotor as well as joule loss in the guideway. The models include the heave, translational and rotational motion of the magnetic rotor for dynamic simulation. The developed analytic and finite element models are highly generic and thus can be applied to any magnetic source. The developed finite element models have been validated by comparing it with commercial finite element software and previously developed boundary coupled steady state finite element model. Commercial finite element software and two experimental setups have been used to verify the developed analytic models. Computational efficiency of the presented models has been compared with the previously developed finite element model and commercial software. Good performance of the developed models has been achieved

Dynamics and Control of Flexure-based Large Range Nanopositioning Systems.

The objective of this thesis is to demonstrate desktop-size and cost-effective flexure-based multi-axis nanopositioning capability over a motion range of several millimeters per axis. Increasing the motion range will overcome one of the main drawbacks of existing nanopositioning systems, thereby significantly improving the coverage area in nanometrology and nanomanufacturing applications. A single-axis nanopositioning system, comprising a symmetric double parallelogram flexure bearing and a traditional-architecture moving magnet actuator, is designed, fabricated, and tested. A figure of merit for the actuator is derived and shown to directly impact the system-level trade-offs in terms of range, resolution, bandwidth, and temperature rise. While linear feedback controllers provide good positioning performance for point-to-point commands, the tracking error for dynamic commands prove to be inadequate due to the nonlinearities in the actuator and its driver. To overcome this, an iterative learning controller is implemented in conjunction with linear feedback to reduce the periodic component of the tracking error by more than two orders of magnitude. Experimental results demonstrate 10 nm RMS tracking error over 8 mm motion range in response to a 2 Hz bandlimited triangular command. For the XY nanopositioning system, a lumped-parameter model of an existing XY flexure bearing is developed in order to understand the unexplained variation observed in the transfer function zeros over the operating range of motion. It is shown that the kinematic coupling, due to geometric nonlinearities in the beam mechanics, and small dimensional asymmetry, due to manufacturing tolerances, may conspire to produce complex-conjugate nonminimum phase zeros at certain operating points in the system's workspace. This phenomenon significantly restricts the overall performance of the feedback control system. After intentional use of large asymmetry is employed to overcome this problem, independent feedback and iterative learning controllers are implemented along each axis. Experimental results demonstrate 20 nm RMS radial tracking error while traversing a 2 mm diameter circle at 2 Hz.PHDMechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/107086/1/parmar_1.pd

Magnetically levitated hysteresis motor driven linear stage for in-vacuum transportation tasks

This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2019Cataloged from PDF version of thesis.Includes bibliographical references (pages 241-246).This thesis presents a new in-vacuum reticle transportation mechanism for extreme ultraviolet (EUV) photolithography machines. In the photolithography process, the reticle is a quartz plate that contains a pattern of the integrated circuit, which needs to be transported between a storage position and the exposure stage. In next-generation EUV lithography machines, the reticle handling system must satisfy the following requirements: (1) transport the reticle through a distance of 2 meters, (2) the height of the mechanism needs to be within 100 mm, (3) operate in vacuum, and (4) satisfy ultra-tight contamination requirements. To fulfill these requirements, a conventional robotic reticle handler is inadequate. In this work, we designed, built, and tested a magnetically-levitated linear stage prototype, targeting at the reticle transportation application. Compared with robot manipulators, linear stages typically require less volume for long-distance transportation tasks.Magnetic suspension is used to eliminate mechanical contact and thereby avoid particle generation that can contaminate the reticle. The stage's linear motion is driven by linear hysteresis motors, which allows using solid-steel motor secondaries on the moving stage. This is desirable for in-vacuum operation, since permanent magnets can out-gas in high vacuum when not encapsulated. The magnetic suspension of the stage is achieved using a novel linear bearingless slice motor design, where the stage's magnetic suspension in three degrees of freedom, including vertical, pitch, and roll, are achieved passively. This compact design effectively reduces the number of sensors and actuators being used. The prototype system has successfully levitated the moving stage. The resonance frequency of the passively levitated degrees of freedom is approximately 10 Hz, and the suspension bandwidth of the actively-controlled degrees of freedom is about 60 Hz.The stage's maximum thrust force is 5.8 N under a 2.5 A current amplitude, which corresponds to a stage acceleration of 1200 M/s². This is able to satisfy the acceleration requirement for reticle transportation task. The stage was tested to track a reticle handling reference trajectory, where the maximum position tracking error of our linear stage is 50 [mu]m. The stage's lateral displacements during motion is below 50 [mu]m, which is well below making mechanical contact to the side walls. To our knowledge, this work represents the first study of linear hysteresis motors, and the first linear bearingless slice motor design. Hysteresis motors are a type of electric machine that operates using the magnetic hysteresis effect of the secondary material. Since the magnetization in the rotor lags behind the external field, a thrust force/torque can be generated.In prior usage, hysteresis motors have been operated in open-loop, which makes them unsuitable for applications where dynamic performance is critical. As a part of this thesis work, we also studied the modeling and closed-loop torque and position control for hysteresis motors. The proposed control method was tested with three rotary hysteresis motors, including two custom-made motors of different rotor materials and one off-the-shelf hysteresis motor. Experimental results show that position control for all three motors can reach a bandwidth of 130 Hz. To our best knowledge, this is the first work that enabled high-bandwidth torque and position control for hysteresis motors, which allows this motor to be used for servo applications.Sponsored by ASMLby Lei Zhou.Ph. D.Ph.D. Massachusetts Institute of Technology, Department of Mechanical Engineerin

Power transmission systems: from traditional to magnetic gearboxes

L'abstract è presente nell'allegato / the abstract is in the attachmen

Design definition of a mechanical capacitor

A design study and analyses of a 10 kW-hr, 15 kW mechanical capacitor system was studied. It was determined that magnetically supported wheels constructed of advanced composites have the potential for high energy density and high power density. Structural concepts are analyzed that yield the highest energy density of any structural design yet reported. Particular attention was paid to the problem of 'friction' caused by magnetic and I to the second power R losses in the suspension and motor-generator subsystems, and low design friction levels have been achieved. The potentially long shelf life of this system, and the absence of wearing parts, provide superior performance over conventional flywheels supported with mechanical bearings. Costs and economies of energy storage wheels were reviewed briefly