Study of a Mini-Actuator with Permanent Magnets

MATEC Web of Conferences

The article presents a comparative study regarding the design and experimental results for a miniature electromagnetic actuator with a modified design comparing with the classical type, including a mobile array of micromagnets and a fixed coil in two configurations (planar spiral multi-layered and cylindrical). Previous work on design, modeling and simulation of this type of actuator indicated the optimum design and conducted to dimensions and material parameters. Different types of actuators were produced and experimentally tested, showing good results but also some drawbacks. Three of these design solutions are presented together with the static voltage-deflection and electrical impedances curves, experimentally derived. The results confirmed the feasibility of two actuating solution, showing good linearity and possibility to control the position at h accuracy and indicated improving directions.

The production of magnetic forces in a magnetic actuator is the focus of the present analysis. Magnetic circuit analysis is used to investigate the direction as well as the expected order of magnitude of the force that attracts the armature into the central portion of a stationary core. A sequence of finite-element based solutions is used to investigate magnetic saturation and to determine the forcedisplacement characteristic. The analytical approach is based on the principle of virtual work and Ampère's law. The force calculations based on numerical field solutions employ the methods of weighted Maxwell stress tensor and the classical virtual work. The more accurate field-derived solutions are used to explain the limitations of the analytical calculations. At the end, an alternative approach to compute the force numerically is proposed. This method is based on the principle of virtual work, but only one field solution is required.

Sensors and Actuators A: Physical, 2015

The force (F) and the power consumption (P) of a magnetic actuator are modeled, measured and optimized in the context of developing micro-actuators for large arrays, such as in portable tactile displays for the visually impaired. We present a novel analytical approach complemented with finite element simulation (FEM) and experiment validation, showing that the optimization process can be performed considering a single figure of merit F/ √ P. The magnetic actuator is a disc-shaped permanent magnet displaced by planar microcoil. Numerous design parameters are evaluated, including the width and separation of the coil traces, the trace thickness, number of turns and the maximum and minimum radius of the coil. We obtained experimental values of F/ √ P ranging from 2 to 12 mN/ √ W using up to 2-layer coils of both microfabricated and commercial printed circuit board (PCB) technologies. This performance can be further improved by a factor of two by adopting a 6-layer technology. The method can be applied to a wide range of electromagnetic actuators.

COMPEL: The International Journal for Computation and Mathematics in Electrical and Electronic Engineering, 2011

Purpose-The purpose of this paper is to investigate the accuracy of different force calculation methods and their impact on mechanical deformations. For this purpose, a micrometer scaled actuator is considered, which consists of a micro-coil and of a permanent magnet (PM) embedded in a deformable elastomeric layer. Design/methodology/approach-For the magnetic field evaluation a hybrid numerical approach (finite element method/boundary element method (FEM/BEM) coupling and a FEM/BEM/Biot-Savart approach) is used, whereas FEM is implemented for the mechanical deformation analysis. Furthermore, for the magneto-mechanical coupling several force calculation methods, namely the Maxwell stress tensor, the virtual work approach and the equivalent magnetic sources methods, are considered and compared to each other and to laboratory measurements. Findings-The numerically evaluated magnetic forces and the measured ones are in good accordance with each other with respect to the normal force acting on the PM. Nevertheless, depending on the used method the tangential force components differ from each other, which leads to slightly different mechanical deformations. Research limitations/implications-Since the force calculations are compared to measurement data, it is possible to give a suggestion about their applicability. The mechanical behavior of the actuator due to the acting forces is solely calculated and therefore only an assumption concerning the deformation can be given. Originality/value-A new kind of micrometer scaled actuator is numerically investigated by using two different hybrid approaches for the magnetic field evaluation. Based on those, the results of several force calculation methods are compared to measurement data. Furthermore, a subsequent structural analysis is performed, which shows slightly different mechanical deformations depending on the used force calculation method.

2008

This paper analytically calculates the magnetic propulsion force of the cylindrical micro-robot using permanent magnetic material and soft magnetic material operated under the Helmholtz and the Maxwell coils. And the analytical results of magnetic force are compared with those by the finite element method. It shows that the proposed analytical method predicts the magnetic force accurately. It also shows that the pre-existing magnetization of permanent magnetic material of a micro-robot generates much bigger magnetic propulsion force than that of soft magnetic material. The micro-robot with soft magnetic material always needs the Helmholtz coil to generate the magnetization of soft magnetic material. This may make the motion control of a micro-robot with soft magnetic material complicated, because the Helmholtz coil affects the magnetic force and magnetic torque of soft magnetic material at the same time.

2009

The reality of the design area, concerning mechanic and mechatronical systems, demands clearly the importance of keeping constant advances in development and improvement of structures, and consequently, accurate analysis and tests more representative

IEEE Transactions on Magnetics, 2000

Journal of Microelectromechanical Systems, 1999

Integrated permanent magnet microactuators have been fabricated using micromachined polymer magnets. The hard magnetic material utilized is a polymer composite, consisting of magnetically hard ceramic ferrite powder imbedded in a commercial epoxy resin to a volume loading of 80%. The magnets have the form of thin disks approximately 4 mm in diameter and 90 m in thickness. These disks have been magnetized in the thickness direction, and even in this geometrically unfavorable direction showed typical permanent magnet behavior with an intrinsic coercivity H ci of 4000 Oe (320 kA/m) and a residual induction Br of 600 Gauss (60 mT). Cantilever beam-type magnetic actuators carrying a screen-printed disk magnet on their free ends have been fabricated on an epoxy board. A planar coil on the opposite side of the substrate is used to drive the beams vertically. The actuators exhibit hard magnetic behavior allowing both attraction and repulsion by reversing the current direction. Static and dynamic testing of the magnetic actuators have been performed. The experimental data are compared with theoretical results obtained from both finite element simulations and analytical models. Good agreement is obtained between simulation and experiment. [273]

The paper presents simulation of the dynamics of a permanent magnet linear actuator with soft magnetic mover and relatively long stroke-60 mm. The simulation is carried out using decoupled approach where the magnetic field problem is solved separately from the electric circuit and mechanical motion problems. The obtained results are compared with experiment.

RSM2013 Proc. 2013, Langkawi, Malaysia

In this work, a theoretical analysis on the magnetic force generation of micro-actuator driven by planar microcoil is reported. The actuator design is optimized to increase the magnetic force and flux density that is useful for mechanical membrane deformation of an actuator. Therefore, this work is focused on the design and simulation of actuator material and structure using a finite element analysis method. As the results, the obtained magnetic force of maximum 11.4 mN has been observed for the actuator design having coil geometry of width w = 100 μm, space s =100 μm, turn N = 20 and thickness t =20 μm with NdFeB as magnet material. Hence, the optimized design geometry of the coil can be used as reference for the fabrication of electromagnetic actuator for micropump application.