Modeling and Design of a Double-Sided Linear Motor with Halbach Array for Low-Vibration and High-Acceleration Applications

In this paper, Amperian current and magnetic charge models of permanent magnets are integrated into a hybrid approach to develop a comprehensive analytical modeling for designing a slotless double-sided linear motor with an arbitrary Halbach array. Unlike the conventional methods that treat magnets as sources for Poisson's equations, the solution is reduced to Laplace's equations, with magnets being represented as boundary conditions. The proposed hybrid approach reduces the complexity of of the problem, requiring the solution for only two or three regions compared to a large number of regions if either Amperian currents or magnetic charges were utilized. The magnetic fields and potentials within distinct regions, along with machine quantities such as shear stress, force-angle characteristics, torque profile, attraction force, misalignment force, and back-EMF, are derived, comprehensively analyzed, and compared to FEM results for accuracy validation. Finally, a thorough sensitivity analysis and design consideration of a linear stage for high acceleration and low vibration applications is discussed

Optimization of an Air Core Dual Halbach Array Axial Flux Rim Drive for Electric Aircraft

The anticipated development of the on-demand-mobility (ODM) market has accelerated the development of electric aircraft. Most proposed electric aircraft have propulsion systems that consist of fans directly driven by electric motors. The lower complexity of these propulsion systems opens the door to more custom propulsion system designs that are tailored to a given aircraft and its mission. This paper represents initial steps in the development of an electric propulsion system design code. A proof of concept version of the code is presented. The proof of concept version of the code is for the design of an axial flux rim driven propulsion system. NASA's all electric aircraft X-57, is used as a case study for this design code. The results of this case study are used to discuss the feasibility and potential benefits of using an axial flux rim driven propulsor on X-57. The final result of the case study shows a potential 4km increase in range over the current design

Rotating Magnetometry For Terrestrial And Extraterrestrial Subsurface Explorations

Signaling and sensing with rotating magnet sources have both Terrestrial and Extraterrestrial applications. The dual spinning magnet unit presented in this paper is a simple, lightweight solution to help understand soil densities and locate water and ice pockets, for example, on Mars. Traditional magnetic telemetry systems that use energy-inefficient large induction coils and antennas as sources and receivers are not practical for extraterrestrial and remote field sensing applications. The recent proliferation of strong rare-earth permanent magnets and high-sensitivity magnetometers enables alternative magnetic telemetry system concepts with significantly more compact formats and lower energy consumption. There are also terrestrial applications, for example, subterranean objects such as underground infrastructure and unexploded ordnances (UXO) that are often unmapped and difficult to find on Earth. Current ground penetrating radar units are expensive, large, and heavy. The research presented explores the viability and possibility to develop a unit that will induce an oscillating magnetic field with controllable shape to reliably locate buried ferromagnetic and non-ferromagnetic objects while remaining lightweight and cost effective. A Dual Rotating Magnet (DRM) design is presented. Experiments and numerical simulations assess the system for terrestrial and extraterrestrial detection of: 1) differences in soil densities, 2) water and ice pockets at shallow depths in the subsurface, and 3) subterranean ferromagnetic and non-ferromagnetic objects of interest

DESIGN AND CONTROL OF A HIGH-PRECISION PERMANENT-MAGNET AC MOTOR USING A HALBACH MAGNET ARRAY

This work presents, designs, models, and tests a two-phase permanent-magnet (PM) external-rotor AC motor utilizing a Halbach array for the purpose of precision positioning. The motor is made up of twelve coils and nine pitches of the Halbach array and controlled through the use of a National Instruments data acquisition (DAQ) board paired with MATLAB’s DAQ toolbox. The motor makes uses of the Halbach array and the lack of any ferromagnetic materials in the system to ensure the internal magnetic field is sinusoidal. The motor takes advantage of this fact to generate a torque that is independent of both the rotor position and current distribution. Whereas most PM motors rely on the requirement that the coil windings are sinusoidally distributed, this motor is able to compensate for not having sinusoidally distributed coil windings by instead adjusting the current phase vector based on rotor positioning. After characterizing the motor and through the utilization of data collected during the normal operation of the motor, and several procedures designed to account for discrepancies in the timing of the DAQ board’s clocks, the response of the three embedded Halleffect sensors were mapped to the position of the rotor. Linear sections of this mapping were then used to control the position of the rotor down to an accuracy of just a few hundred thousandths of a degree. Additionally, due to the inherent nature and stability of the system, the only controller required to achieve these results is a PID controller

2D positioning control system for the planar motion of a nanopositioning platform

A novel nanopositioning platform (referred as NanoPla) in development has been designed to achieve nanometre resolution in a large working range of 50 mm × 50 mm. Two-dimensional (2D) movement is performed by four custom-made Halbach linear motors, and a 2D laser system provides positioning feedback, while the moving part of the platform is levitating and unguided. For control hardware, this work proposes the use of a commercial generic solution, in contrast to other systems where the control hardware and software are specifically designed for that purpose. In a previous paper based on this research, the control system of one linear motor implemented in selected commercial hardware was presented. In this study, the developed control system is extended to the four motors of the nanopositioning platform to generate 2D planar movement in the whole working range of the nanopositioning platform. In addition, the positioning uncertainty of the control system is assessed. The obtained results satisfy the working requirements of the NanoPla, achieving a positioning uncertainty of ±0.5 µm along the whole working range

Positioning Control System for a Large Range 2D Platform with Submicrometre Accuracy for Metrological and Manufacturing Applications

The importance of nanotechnology in the world of Science and Technology has rapidly increased over recent decades, demanding positioning systems capable of providing accurate positioning in large working ranges. In this line of research, a nanopositioning platform, the NanoPla, has been developed at the University of Zaragoza. The NanoPla has a large working range of 50 mm × 50 mm and submicrometre accuracy. The NanoPla actuators are four Halbach linear motors and it implements planar motion. In addition, a 2D plane mirror laser interferometer system works as positioning sensor. One of the targets of the NanoPla is to implement commercial devices when possible. Therefore, a commercial control hardware designed for generic three phase motors has been selected to control and drive the Halbach linear motors.This thesis develops 2D positioning control strategy for large range accurate positioning systems and implements it in the NanoPla. The developed control system coordinates the performance of the four Halbach linear motors and integrates the 2D laser system positioning feedback. In order to improve the positioning accuracy, a self calibration procedure for the characterisation of the geometrical errors of the 2D laser system is proposed. The contributors to the final NanoPla positioning errors are analysed and the final positioning uncertainty (k=2) of the 2D control system is calculated to be ±0.5 µm. The resultant uncertainty is much lower than the NanoPla required positioning accuracy, broadening its applicability scope.<br /

A Dual-Stack Coaxial Magnetic Gear for a Wave Energy Conversion Generator

This paper presents the electromagnetic and mechanical design and analyses of a 7.67:1 gear ratio magnetic gear for a wave energy converter demonstrator. A 2-D and 3-D magnetostatic finite element analysis (FEA) was conducted to maximize the mass torque density. To increase torque without increasing the diameter a unique dual-stack rotor topology was used along with a twelve-segment per pole-pair inner rotor Halbach array and a four-segment per pole-pair outer rotor Halbach topology. The eddy current loss within the magnetic gear was mitigated by using laminated magnets and a low-loss electrical steel. The experimentally tested magnetic gear had a peak torque of 1796.8 N∙m which corresponds to an active region volumetric and mass torque density of 221.1 N∙m/L and 105.74 N∙m/kg, respectively. The efficiency at rated speed and maximum torque was measured to be 95%. A new in-plane eddy current loss mechanism was identified as being a primary reason for the measured electrical losses being higher than initially calculated

A Review of Transverse Flux Machines Topologies and Design

High torque and power density are unique merits of transverse flux machines (TFMs). TFMs are particularly suitable for use in direct-drive systems, that is, those power systems with no gearbox between the electric machine and the prime mover or load. Variable speed wind turbines and in-wheel traction seem to be great-potential applications for TFMs. Nevertheless, the cogging torque, efficiency, power factor and manufacturing of TFMs should still be improved. In this paper, a comprehensive review of TFMs topologies and design is made, dealing with TFM applications, topologies, operation, design and modeling

Numerical and Experimental Analysis of Magnetic Gears

Like mechanical gears, magnetic gears convert power between low-speed, hightorque rotation and high-speed, low-torque rotation. This work compares various magnetic gear designs and topologies, introduces an approach for evaluating their dynamic behavior, and describes a prototype’s design, fabrication, and test results. Significant differences are illustrated between the designs minimizing cost and those minimizing volume, especially regarding the usage of permanent magnet material. Axial flux coaxial magnetic gears can outperform their radial flux counterparts at form factors with outer radii much larger than the axial length, but axial flux gears suffer from large forces on the rotors. Cycloidal magnetic gears achieve higher torque densities at high gear ratios than coaxial magnetic gears, but cycloidal magnetic gears perform worse at low gear ratios and suffer from increased mechanical complexity and large forces on the bearings. For coaxial magnetic gears, the torque density and efficiency of a single-stage reduce significantly as the gear ratio increases; however, a high gear ratio can be achieved with less reduction in torque density if magnetic gears are connected in series to form a multistage magnetic gearbox. Alternatively, a compound differential coaxial magnetic gear can be formed from two single-stage coaxial magnetic gears and can achieve a very high gear ratio, but it suffers from circulating power, which results in poor efficiencies. The gear ratio significantly impacts the dynamic behavior of magnetically geared systems. This dynamic behavior can be evaluated by separating the system’s motion into rigid body motion and fixed center motion and by applying the conservation of energy principle to the torque angle reference frame. Halbach arrays and air cores can significantly increase a magnetic gear’s torque density with respect to mass, when used together. To further explore this concept, a prototype magnetic gear with Halbach arrays and air cores was designed, fabricated, and tested. The prototype showed good agreement with simulation regarding slip torque and gear ratio. The prototype achieved a mass competitive with some similarly rated commercially available mechanical gears and also achieved a favorable projected efficiency compared to these mechanical gears