Suppression of Thrust Fluctuation of a New Ironless Tubular Permanent Magnet Synchronous Linear Motor Based on the Halbach Array

The air gap magnetic field (AGMF) is the key factor in determining the ironless tubular permanent magnet synchronous linear motor (ITPMSLM). The distortion of its waveform causes thrust fluctuation during the operation of the motor, resulting in poor machining accuracy of the machine tool. To solve this problem, this paper proposes a new chamfered permanent magnet structure (CPMS) to improve its performance. First, the equivalent magnetic charge method is used to analyze the AGMF, and the analytical expressions of the no-load back EMF and thrust of the new motor are obtained. Second, the AGMF of six kinds of CPMS is analyzed by the Fourier coefficient. Taking the minimum harmonic distortion rate as the optimization objective, the CPMS that makes the AGMF waveform reach the best sinusoidal property is obtained and the no-load back EMF and thrust of the new motor are analyzed. Then, the new motor is compared with the ITPMSLM of rectangle permanent magnet structures (RPMS). Finally, according to the CPMS, the test prototype is built and tested under different working conditions. The research results show that when the outer circumference is 45o chamfered, the ratio of permanent magnet thickness h2 to the chamfered thickness h1 is 0.8; the sinusoidal property of AGMF is the best, and this structure can effectively reduce the motor thrust fluctuation rates to less than 0.01%, which verifies the effectiveness of the CPMS in improving the sinusoidal property in the AGMF and restraining the thrust fluctuation of the ITPMLSM.

Analysis of the Influence of Ferromagnetic Material on the Output Characteristics of Halbach Array Energy-Harvesting Structure

Due to the particular arrangement of permanent magnets, a Halbach array has an significant effect of magnetism and magnetic self-shielding. It can stretch the magnetic lines on one side of the magnetic field to obtain an ideal sinusoidal unilateral magnetic field. It has a wide application range in the field of energy harvesting. In practical applications, magnetic induction intensity of each point in magnetic field is not only related to the induced current and conductor but also related to the permeability of the medium (also known as a magnetic medium) in the magnetic field. Permeability is the physical quantity that represents the magnetism of the magnetic medium, which indicates the resistance of magnetic flux or the ability of magnetic lines to be connected in the magnetic field after coil flows through current in space or in the core space. When the permeability is much greater than one, it is a ferromagnetic material. Adding a ferromagnetic material in a magnetic field can increase the magnetic induction intensity B. Iron sheet is a good magnetic material, and it is easy to magnetize to generate an additional magnetic field to strengthen the original magnetic field, and it is easy to obtain at low cost. In this paper, in order to explore the influence of ferromagnetic material on the magnetic field and energy harvesting efficiency of the Halbach array energy harvesting structure, iron sheets are installed on the periphery of the Halbach array rotor. Iron sheet has excellent magnetic permeability. Through simulation, angle between iron sheet and Halbach array, radian size of iron sheet itself and distance between iron sheet and Halbach array can all have different effects on the magnetic field of the Halbach array. It shows that adding iron sheets as a magnetic medium could indeed change the magnetic field distribution of the Halbach array and increase energy harvesting efficiency. In this paper, a Halbach array can be used to provide electrical power for passive wireless low-power devices.

A comparative study on the performance of SSDR coreless AFPM generators with conventional and Halbach magnet arrays

An axial flux permanent magnet (AFPM) generator is known to be a good candidate for both low- and high-speed applications. In this paper, a comprehensive comparison of four coreless AFPM generators is presented with conventional and Halbach magnet arrangement combined with iron and ironless rotor (epoxy). With the same coreless stator structure, four different AFPM generators with different rotor magnet arrangement and materials are compared in terms of voltage, current, power, machine weight, and power density. The analytical design approach is first presented and is subsequently validated using ANSYS Maxwell electromagnetic finite element analysis (FEA) software. Results show that AFPM machine with fully coreless topology using Halbach array with epoxy rotor can deliver similar power density but has a lower cost compared to conventional magnet array with iron rotor. Hence, this topology is favorable for low power low cost applications.

Magnetic field and electromagnetic performance analysis of permanent magnet machines with segmented Halbach array

Purpose This study aims to accurately calculate the magnetic field distribution, which is a prerequisite for pre-design and optimization of electromagnetic performance. Accurate calculation of magnetic field distribution is a prerequisite for pre-design and optimization. Design/methodology/approach This paper proposes an analytical model of permanent magnet machines with segmented Halbach array (SHA-PMMs) to predict the magnetic field distribution and electromagnetic performance. The field problem is divided into four subdomains, i.e. permanent magnet, air-gap, stator slot and slot opening. The Poisson’s equation or Laplace’s equation of magnetic vector potential for each subdomain is solved. The field’s solution is obtained by applying the boundary conditions. The electromagnetic performances, such as magnetic flux density, unbalanced magnetic force, cogging torque and electromagnetic torque, are analytically predicted. Then, the influence of design parameters on the torque is explored by using the analytical model. Findings The finite element analysis and prototype experiments verify the analytical model’s accuracy. Adjusting the design parameters, e.g. segments per pole and air-gap length, can effectively increase the electromagnetic torque and simultaneously reduce the torque ripple. Originality/value The main contribution of this paper is to develop an accurate magnetic field analytical model of the SHA-PMMs. It can precisely describe complex topology, e.g. arbitrary segmented Halbach array and semi-closed slots, etc., and can quickly predict the magnetic field distribution and electromagnetic performance simultaneously.

Design Optimization and Comparison of Cylindrical Electromagnetic Vibration Energy Harvesters

Investigating the coil–magnet structure plays a significant role in the design process of the electromagnetic energy harvester due to the effect on the harvester’s performance. In this paper, the performance of four different electromagnetic vibration energy harvesters with cylindrical shapes constrained in the same volume were under investigation. The utilized structures are (i) two opposite polarized magnets spaced by a mild steel; (ii) a Halbach array with three magnets and one coil; (iii) a Halbach array with five magnets and one coil; and (iv) a Halbach array with five magnets and three coils. We utilized a completely automatic optimization procedure with the help of an optimization algorithm implemented in Python, supported by simulations in ANSYS Maxwell and MATLAB Simulink to obtain the maximum output power for each configuration. The simulation results show that the Halbach array with three magnets and one coil is the best for configurations with the Halbach array. Additionally, among all configurations, the harvester with two opposing magnets provides the highest output power and volume power density, while the Halbach array with three magnets and one coil provides the highest mass power density. The paper also demonstrates limitations of using the electromagnetic coupling coefficient as a metric for harvester optimization, if the ultimate goal is maximization of output power.

Design and Construction of a Chamber Enabling the Observation of Living Cells in the Field of a Constant Magnetic Force

The aim of the work was to design and construct a microscopic stage that enables the observation of biological cells in a magnetic field with a constant magnetic force. Regarding the requirements for biological observations in the magnetic field, construction was based on the standard automatic stage of an optical microscope ZEISS Axio Observer, and the main challenge was to design a set of magnets which were the source of a field in which the magnetic force was constant in the observation zone. Another challenge was to design a magnet arrangement producing a weak magnetic field to manipulate the cells without harming them. The Halbach array of magnets was constructed using permanent cubic neodymium magnets mounted on a 3D printed polymer ring. Four sets of magnets were used, differing in their dimensions, namely, 20, 15, 12, and 10 mm. The polymer rings were designed to resist magnetic forces and to keep their shape undisturbed when working under biological conditions. To check the usability of the constructs, experiments with magnetic microparticles were executed. Magnetic microparticles were placed under the microscope and their movement was observed to find the acting magnetic force.

Vibration Analysis of Hub Motor Based on ANSYS

The hub motor is designed with multidirectional excitation and Halbach Array, which includes inner rotor, left and right stator, outer stator, encoder and rotary transformer. The rotor consists of an axial disk and a top ring. The rotor’s permanent magnets are affixed to the left and right sides of the disk and to the outside of the top ring. The permanent magnets on the rotor adopt a Halbach Array. The three stators have not the iron core and they are arranged outside the rotor to form a three-way closed loop. The motor has high power density, high torque density, low heating, strong adaptability and no cogging effect. It is suitable for electric car control. On this basis, the dynamic equation of the hub motor is established, the vibration mode of the rotor system is analysed, when the inner rotor’s speed is 18000rpm. By use of the solid model, the hub-rotor’s accurate dynamics solution can be obtained. In the future, the effect of vertical coupling vibration will be investigated for its ride comfort and safety.