Conventional Electromagnetic Actuators Research Articles

Disturbance Observer-Based Robust Controller for a Multiple-Electromagnets Actuator

This paper proposes a disturbance observer (DOB)-based robust controller to improve the control performance of an electromagnetic actuator (EMA) with multiple electromagnets by compensating for the uncertainties caused by magnetic fields' nonlinearity and unmodeled magnetic properties. Conventional EMAs have been widely researched, but control strategies are limited to linearized magnetic field models based solely on intrinsic magnetic field strength. Thus, we designed a DOB-based double-loop feedback controller to extend the nominal feedback controller based on linearized magnetic field models. The DOB-based controller compensates for the unmodeled uncertainties and nonlinearities of multiple electromagnetic fields and improves performance in combination with the robustness of a conventional control scheme. The designed controller works as a force compensator for the target object and can widen the region of interest (ROI) of the given conventional EMA system without scale-up design. Experimental results demonstrate that the proposed DOB-based controller improves the trajectory tracking error by 58.2% within the target ROI. Finally, the robustness of the proposed DOB-based controller for extended ROI is validated through a comparison with other control methods, which may increase the usefulness of the conventional EMA system.

Toward Flexible Actuator Design for Electromagnetic Flanging of Sheet and Tube Metal

This paper proposed a new flexible actuator for electromagnetic forming processes, which combined a solenoid coil with a field shaper to tailor the distribution of the pulsed magnetic field. The leading contribution of our proposal is the flexible control of Lorentz force for forming sheet and tube metal workpieces by using the same actuator, which is difficult for the conventional electromagnetic actuator. To validate the feasibility of the proposal, the principle, design procedure, and realization of the actuator were firstly analyzed and discussed. On this basis, the forming experiments were then carried out, in which multi-step discharge processes were adopted to ensure forming quality control. Accordingly, the experimental results showed that the maximum die-fitting gaps of the flanged sheet and tube were within 0.3 mm, verifying the feasibility of the proposed actuator.

Analysis of a Serial/Parallel Type of Electromagnetic Actuator.

This paper describes the design and analysis of a small-sized and high thrust electromagnetic actuator. The proposed actuator is supposed to be used for application control of the hotmelt adhesive. The hotmelt has different characteristics for each material and the electromagnetic actuator is required variable characteristics. However, the problem seems to lie in the fact that it is necessary to remake another mold again to change the characteristics of the conventional electromagnetic actuator. Therefore, this paper presents small-sized electromagnetic actuator called a basic model that can stack it in the axial direction or in the radial direction. As the analysis comparison at the same size, the characteristics of conventional two serial model which stack two basic models in the axial direction and proposed three serial models have been compared by three-dimensional finite element method. In the proposed model, characteristics have been improved by reducing the core volume and increasing the number of stacks in the basic model from the viewpoint of magnetic flux density. In addition, various electromagnetic actuators that stack basic models in the axial direction or in the radial direction have been analyzed. The analysis results have been clearly shown as characteristics mapping and it has indicated that the proposed electromagnetic actuator can be constructed easily by stacking the basic model.

Flexural Deflection Prediction of Piezo-Composite Unimorph Actuator Using Material Orthotropy and Nonlinearity of Piezoelectric Material Layer

Layered piezo-composite unimorph actuators have been studied by many research teams to provide active vibration control of thin-walled aerospace structures, control the shapes of aircraft wing airfoils, and control the fins of small missiles, because they require less space and provide better frequency responses than conventional electro-magnetic motor actuator systems. However, due to the limited actuation strains of conventional piezo-composite unimorph actuators with poly-crystalline piezoelectric ceramic layers, they have not been implemented effectively as actuators for small aerospace vehicles. In this study, a lightweight piezo-composite unimorph actuator (LIPCA-S2) was manufactured and analyzed to predict its flexural actuation displacement. It was found that the actuated tip displacement of a piezo-composite cantilever could be predicted accurately using the proposed prediction model based on the nonlinear properties of the piezoelectric strain coefficient and elastic modulus of a piezoelectric single crystal.

The Performance of a Novel Latching-Type Electromagnetic Actuator for Single-Port Laparoscopic Surgery

This paper reports on the performance evaluation of a novel latching-type electromagnetic actuator which is designed to be embedded at selected joints along single-port laparoscopic surgical instruments (SLS). The aim of this actuator is to allow these instruments to become articulated with a push of a button in order to provide the optimum angulation required during SLS operations. This new actuator is comprised of electromagnetic coil elements, soft magnetic frames and a permanent magnet. Unlike conventional electromagnetic actuators, latching-type electromagnetic actuators could maintain their positions at either end of the actuation stroke without any power application requirement. In the current design, magnetic attraction forces initiated between the permanent magnet and the magnetic frame are utilised to lock the position of the actuator whilst a certain angulation position of the actuator is achieved as a result of the magnetic repulsion forces established between the permanent magnet and the coil elements. The performance of the new actuator in terms of the output force, maximum angulation and patient’s safety, was evaluated experimentally and the results were found to compare well with those acquired numerically using finite element methods. This actuator was seen to exhibit sufficient actuation forces and hence, it was capable of providing adaptable angulation characteristics for SLS tools. Finally, thermal evaluation of the actuator’s operation was conducted, which was found to be within safety limits specified by clinicians.

Miniaturized twin-legged robot with an electromagnetic oscillatory actuator

There have been many studies on the moving mechanism of micro robots, such as stick-slip, inchworm like motion, and impact drive. Novel actuators like lead zirconate titanate (PZT), Shape Memory Alloy (SMA), magnetostrictive materials, electromagnetic actuators, electoractive polymers, ultrasonic linear motors, and dielectric elastomers are utilized to realize the moving mechanism. The use of a conventional electromagnetic actuator is unfavorable, because of a few drawbacks, such as generation of stray magnetic fields, hard to miniaturize to the millimeter scale because of 3D integration and a scaling law, and power consumption to maintain a certain position. This research presents a micro robot that uses an electromagnetic actuator customized and developed for micro robot. The electromagnetic actuator is designed from a Brushless Direct Current (BLDC) motor to overcome the drawbacks mentioned above. The developed robot is composed of two electromagnetic actuators. The overall size of the robot is 20 mm × 11 mm × 9 mm (length × height × width) and the weight is 3 g. The developed robot is able to move bidirectionally with a maximum moving speed of 15.76 mm·s−1 (0.79 body-length per second). The optimal conditions of an input signal are calculated theoretically and verified with experiments.

Novel and compact thermomagnetic actuator using temperature-sensitive magnetic materials

This paper describes the structure and characteristics of a novel compact actuator that uses a combination of temperature-sensitive magnetic materials (TSMMs) and permanent magnets (PMs). The actuator has the potential to generate a large force per volume, while the absence of a coil structure makes it easy to downsize. The structure and driving principles of the actuator were determined to exploit the advantages of this combination, and thrust force characteristics were examined through numerical analysis. The thrust force generated was measured based on the temperature of the TSMMs. The temperature characteristics were investigated experimentally and theoretically. In addition to thrust force, the energy consumption was experimentally examined with respect to the TSMM temperature. The results indicate that the proposed actuator performed better than a conventional electromagnetic actuator in generating a large continuous thrust force.

Design of natural frequency adjustable electromagnetic actuator and active vibration control test

An important issue in inertia electromagnetic actuator is that the best performance of device is limited to a very narrow bandwidth around the natural frequency. In order to overcome this issue of the conventional inertia electromagnetic actuator, an inertia electromagnetic actuator capable of adjusting the natural frequency is introduced. This paper presents theoretical investigation, design method, and experimental tests of the natural frequency adjustable electromagnetic actuator. The optimal design scheme is obtained by using ANSOFT software and experimental tests are conducted to examine the practical property of natural frequency adjustable electromagnetic actuator. Following the results obtained by property experiments, a series of active vibration control tests are carried out and experimentally verified that although the measured natural frequencies at different positions cannot satisfy the theoretical values perfectly, natural frequency adjustable electromagnetic actuator still works very well at test frequencies and reduces the vibration from 18.3 dB to 11.3 dB at frequency of 26.25 Hz.

Electromagnetic biaxial vector scanner using radial magnetic field.

We present an electromagnetic biaxial vector-graphic scanning micromirror. In contrast to conventional electromagnetic actuators using linear magnetic field, proposed device utilizes a radial magnetic field and uniquely designed current paths to enable the 2 degree-of-freedom scanning motion. As the radial field is generated by concentrically assembled magnets placed under the scanner die, large driving torque can be generated without the aid of hermetic packaging and relatively small device volume can be achieved. Mechanical half scan angle of 6.43° and 4.20° have been achieved at DC current of 250mA and 350mA for horizontal and vertical scans, respectively. Forced actuation along both scan axes has been realized by feedback control.

Genetic Algorithm-Based Design Optimization of Electromagnetic Valve Actuators in Combustion Engines

In this research, the design of a new electromagnetic engine valve in the limited space of combustion engine is optimized by multidisciplinary simulation using MATLAB and Maxwell. An electromagnetic engine valve actuator using a permanent magnet is a new actuator concept for overcoming the inherent drawbacks of the conventional solenoid-driven electromagnetic engine valve actuator, such as high power consumption and so on. This study aims to maximize the vibration frequency of the armature to reduce the transition time of the engine valve. The higher performance of the new actuator is demonstrated by dynamic finite element analysis.

Effects of Magnetic Pole Design on Orientation Torque for a Spherical Motor

This paper investigates the effect of pole layouts of permanent magnets (PMs) and electromagnets (EMs) on inclination torque of a multidegrees of freedom (DOFs) spherical motor (SM). Unlike conventional electromagnetic actuators capable of controlling a single DOF motion in spinning, the SM offers a unique ability to control orientation of a spinning rotor. Although the motor offers such attractive feature, it is essential to generate torque to maintain at a desired orientation. However, it is challenging to design the motor enhancing the orientation torque due to a limited number and space for PMs and EMs involved in orientation motion unlike spinning. This paper presented a new design of the SM maximizing inclination torque by evaluating the number of PMs and materials of structure such as iron and aluminum. Then, the torque of the proposed designs has been compared by results from a numerical finite-element method technique as well as an experiment. Finally, dynamics and control simulations are demonstrated to ensure the effective enhancement of the proposed SM.

A piezoelectric single-crystal ultrasonic microactuator for driving optics

At the millimeter scale, the motions or force out puts generated by conventional piezoelectric, magnetostrictive, photostrictive, or electromagnetic actuators are very limited. Here, we report a piezoelectric ultrasonic microactuator (size: 1.5 × 1.5 × 5 mm, weight: 0.1 g) made of PIN-PMN-PT single crystal. The actuator converts its high-frequency microscopic displacements (nanometer to micrometer scale) into a macro scopic, centimeter-scale linear movement of a slider via frictional force, resulting in a speed up to 50 mm/s and a very high unit volume direct driving force of 26 mN/mm(3) (which is ~100 times higher than a voice coil motor and ~4 times higher than a piezoceramic ultrasonic motor). This work shows the feasibility of using piezoelectric single-crystal-based ultrasonic microactuator for miniature drive of optics in next-generation mobiles and cameras.

多段磁極式電磁比例アクチュエータの試作研究（第３報，アーマチャの寸法諸元が性能に及ぼす影響）

This study deals with a newly proposed electro-magnetic proportional actuator for hydraulic control valves, in which multi poles are arranged in a row. The force produced by this actuator is more than 2.5 times as large as that of conventional proportional electro-magnetic actuators of solenoid type. Performances of this actuator have been reported in previous papers. In this paper, influences of dimensions such as clearance between stator and armature, thickness of the armature and length of the top land of the armature are investigated experimentally. It becomes clear that the produced force increases with reduction in the clearance between stator and armature. Moreover, influences of the thickness of the armature are not so large as long as the length of the top land is smaller than 40% of the thickness of the armature. The results in this paper will be profitable for designing the actuator.

Simulation of muscle characteristics using an electromagnetic actuator

To accurately predict human body motion during a vehicle crash, active and passive characteristics of a muscle must be expressed. The crash test dummy presently used only expresses the passive characteristics of a muscle by using springs, so it has limited accuracy in predicting human body motion of current crash test dummies. In this paper, a muscle activation system composed of an electromagnetic actuator and a tensile spring is proposed to resolve such limitation of the current crash test dummy. The proposed actuator reproduces the active characteristics of a muscle. Because the flux path of the actuator is designed by reluctance path modulation using an electromagnet and two permanent magnets, the actuator improves upon non-linearity and power consumption of a conventional electromagnetic actuator. The tensile spring is adopted to resolve the short moving range of the actuator, to increase the bandwidth limit of the muscle activation system, and to reproduce the passive characteristics of a muscle. Tests reproducing the force-length and force-velocity characteristics of a muscle were carried out to verify the performance of the developed muscle activation system. The experimental results showed that the muscle activation system successfully reproduced the force-length and force-velocity characteristics of a muscle.

단순 원판형 평면 3자유도 액추에이터 설계

A disk-type 3-DOF actuator which has new principle and very simple structure is proposed. Also it utilizes the relation of bias and control fluxes produced by permanent magnets and coils, respectively, like other conventional electromagnetic actuators, but its main feature is that both the coils and permanent magnets are fixed in the stator, which makes it easy to design the shape of moving part. Operating principle is that a moving disk is driven by reaction force of Lorentz force acting on the fixed equivalent coil. Simple analytic approach and FEM analysis are performed to determine the design parameters so as to increase the driving force and distance. And some experimental results show the feasibility of the proposed actuator.

Using Self-Sensing Techniques to Produce a Small, Robust, Inexpensive Rheometer

Abstract Self-sensing is the technique of using a transducer to both actuate and sense concurrently, therefore eliminating the need for separate sensors. A sensorless rheometer could be much smaller, simpler and more robust than traditional designs. One application where such a rheometer would be desired is the in-situ measurement of curing bone cement in orthopaedic surgery. A set of equations was developed that models the relationship between force, motion and back-e.m.f. generation for a class of electromagnetic actuators. This enables velocity, displacement and force to be self-sensed from voltage measurements only. This self-sensing was validated on a conventional linear electromagnetic actuator, and a small rotary moving magnet device, which was designed to be a small self-sensing rheometer. The accuracy of the estimation was assessed and shown to compare favourably with measured data. The actuators were then used to construct simple rheometers to measure bone cement. Rheological models were used to calculate storage and loss moduli and dynamic viscosity from the self-sensed values of displacement, velocity and torque. The accuracy of these self-sensing rheometers was verified against a traditional rheometer using a silicone fluid and a polyethylene oxide solution. The self-sensing rheometers were used to characterise acrylic bone cements during curing, reinforcing and extending upon previous results. The elimination of sensors meant that it was possible to produce a small, inexpensive rheometer with a very simple structure. This indicates there is potential to develop small rheo-transducers for certain applications.

Electrostatic Torsion Mirror for Optical Disk Drives

A new electrostatic torsion mirror with a silicon/silicon structure has been developed for optical disk drives. It positions the beam spot accurately on an optical disk 1),2). This mirror is mounted on a 3.8 x 4.5 mm chip and weighs approximately 25 mg. Thus, downsizing of optical heads can be realized by using this torsion mirror. This torsion mirror is composed of an elliptic mirror plate, twin supporting beams, and a pair of driving electrodes. The forms of these elements define the mechanical parameters of this torsion mirror: natural frequency and damping ratio. These mechanical parameters are designed to satisfy the specifications for a high-frequency positioning of the optical beam spot. Experimental frequency responses showed that a test model had a second modal mechanical frequency of over 50 kHz, and the characteristics were in good agreement with the designed values. This torsion mirror will make possible more accurate spot positioning than can be achieved using conventional electromagnetic actuators.

映像情報ストレージ技術 光ヘッド用Ｓｉ偏向ミラーの設計

A new electrostatic torsion mirror with a silicon/silicon structure has been developed for optical heads. It positions the beam spot accurately on an optical disk having a high track density. This torsion mirror is composed of a hexagonal mirror plate, twin supporting beams, and a pair of driving electrodes. The natural frequency of mirror rotation is defined by the moment of inertia of the mirror plate and the stiffness of the beams. The squeeze effect between the mirror plate and the electrodes generates the damping force. These mechanical parameters are designed to satisfy the specifications for a high-frequency positioning of the beam spot. Experimental frequency responses showed that a test model had a second modal mechanical frequency of over 50 kHz, and the characteristics were in good agreement with the designed values. This torsion mirror will make possible more accurate spot positioning than can be achieved using conventional electromagnetic actuators.