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This article presents the design, optimization, and testing of a new rotating electromagnetic field generation system for actuating magnetic microrobots. Its unique feature lies in that the proposed six-coil electromagnetic actuation system produces a uniform rotating magnetic field with a large 3-D workspace, which is enabled by conducting an architectural optimization of the system in consideration of both electric issues and geometry constraints. To maintain a low working temperature, each coil is fabricated with silicone grease for filling the gap among the copper wires and integrated with a water cooling fan for reducing the effect of coil heating. An analytical model is established to determine the dominant structural parameters, which are optimally tuned by resorting to genetic algorithm (GA) to achieve the best actuation performance. A prototype magnetic field generation system is developed for experimental testing. Experimental studies are carried out by driving various magnetic microrobots, including helical microswimmers and microparticles. Results indicate that the developed system can effectively actuate the microrobots with precision motion tracking, validating the effectiveness of the developed rotating magnetic field generation system. [ABSTRACT FROM AUTHOR]

Magnetic parameters necessary to obtain the highest variation of permeability during the phase transition in Ni2FeGa glass-coated microwire are studied. It is shown that the martensitic transformation in glass-coated microwires is accompanied with a huge variation of permeability due to the different anisotropy of martensitic and austenitic phase. Variation of permeability can be adjusted up to 1600% by application of properly selected amplitude of excitation magnetic field. The highest variation of permeability was obtained for the field of 2.6 Oe, in which the permeability of austenite shows maximum, while permeability of martensite is still low. [ABSTRACT FROM AUTHOR]

This paper develops an approximate analytical model to describe the magnetic fluxes, forces, and armature reaction in cylindrical voice coil actuators and related electric machines. Magnetic flux is assumed to either lie in an inner region of the actuator and parallel to its axis, or in an outer region of the actuator and oriented radially. A differential reluctance model is derived for this set of assumptions, with a structure and solution set similar to those involved in extended-surface heat transfer (“fins”) and lossy transmission lines. Particular solutions for the force constant, motor constant, coil inductance, and variable-reluctance force are found for a symmetric motor with opposed axial permanent magnets on either side of an iron flux concentrator. The model results for this topology are validated using finite-element analysis and experimental measurements from a prototype. [ABSTRACT FROM AUTHOR]

This paper presents a miniature autofocus (AF) voice coil motor (VCM) actuator with retaining force in a restricted space that can be applied in an optical AF apparatus. A position encoder consisting of a permanent magnet (PM) and a Hall-effect sensor is used to detect magnetic signals; the displacement of the AF VCM actuator can be obtained from the encoder, thus enabling closed-loop control. The proposed miniature AF VCM actuator consists of a high-permeability magnetoconductive plate and a PM on another side to generate a retaining force when the exciting current is switched off. Using a 3-D finite-element analysis simulation and the Maxwell stress tensor method, the electromagnetic Lorentz force within a movable displacement was determined to be ∼16 mN. Blur caused by variable force and load disturbance was observed in images captured during AF operation. This adaptive fuzzy proportional-integral–derivative (PID) control approach compensates for the nonuniform friction, disturbance variation, and even load changes of the movable part of the AF VCM actuator that occur when a subject is photographed in various positions. The adaption mechanism reduced control effort, despite the variable force and load disturbance, and exhibited fast dynamic performance and minimal steady-state error. [ABSTRACT FROM AUTHOR]

This paper presents an inductance derivative estimation method of linear switched reluctance actuator (LSRA) employing tracking-differentiating technology. The inductance of LSRA is highly nonlinear and varies with phase current and translator position. To achieve direct force control, the derivative of inductance must be estimated to generate required phase currents. The inductance profile of LSRA is obtained from finite element analysis calculation. Tracking differentiator is introduced to track the inductance and its derivative for further control purpose. A simple Proportional-Integral control with compensation unit using the estimated inductance derivative is used to examine the effectiveness of the estimation of inductance derivative. [ABSTRACT FROM AUTHOR]

This paper presents a comparison of several three-degrees-of-freedom (DoFs) semispherical actuator topologies, which can mimic a shoulder joint of an actuated support system. A semianalytical model is applied to determine the torque performance as function of the position. Hence, the current distribution through the coils with minimized ohmic losses can be determined. The performed topology comparison is based on the average power dissipation and on a set of torque and range of motion requirements. [ABSTRACT FROM AUTHOR]

Overall optimization of electromechanical aerospace actuators requires a multiobjective analysis to account for both performance and efficiency, while considering technical costs, due to the conflicting nature of the respective criteria. This paper introduces a particular multiobjective, population-based optimization methodology, using the differential evolution algorithm combined with manufacturing cost and motor–clean–interface related constraints. A magnetic equivalent circuit model is implemented and integrated in the process to account for flux leakage effects. The methodology presents stable convergence characteristics and has been applied to further extend previous work regarding the optimization of a fractional slot concentrated winding surface mounted permanent magnet motor. The resultant motor design has been validated through a prototype and experimental results illustrated its suitability for aerospace actuation. [ABSTRACT FROM AUTHOR]

Gas-atomized Fe-4, 6wt.%Al powders were annealed in a damp hydrogen atmosphere with a dew point of 0 ^\circ\C and -17\ ^\circ\C in order to cover the powder surface with a high electrical resistivity layer of Al2O3 and then compressed into cores. The powders should be oxidized at a temperature higher than 800 ^\circ\C in order to oxidize the aluminum alone on the surface of powder, as confirmed by simulation using the STANJAN program. An Al-rich layer, i.e., an Al2O3 layer, was formed on the surface of the Fe-Al powder, as confirmed by SEM. Loss of the cores made from the selectively oxidized powders was much lower than those of the cores with phosphate coats, so the selectively oxidized powder can be used to fabricate electrical actuators with high levels of performance. [ABSTRACT FROM AUTHOR]

We have studied a cylindrical moving coil linear DC motor to ink jet shuttle printer that make it possible to print with high speed, high resolution and low power consumption. The actuator is supposed to be driven using resonance of spring plates which are placed at the end of the permanent magnet and the armature respectively. However, the permanent magnet and armature of the actuator did not resonated at the same frequency and the spring coefficient changed because these were fixed to the supports by screws. At present, a new support mechanism is being made. [ABSTRACT FROM PUBLISHER]

A liquid hydrogen pump was developed as an important part of a fuel system for a hydrogen engine. However, it is possible that ambient heat enters the liquid hydrogen in the tank. In order to solve this problem, a new compact liquid hydrogen pump is proposed by using a linear oscillatory actuator (LOA). This paper reports the basic characteristics of a LOA for liquid hydrogen pump. The structure of the LOA is described first, and then the structure of the liquid hydrogen pump by using LOA is described. As a result of experiments, when the delivery pressure is 1 MPa, this pump was operated with the required stroke (15 mm) up to 1.8 Hz when using water. In case of using liquid nitrogen, with a delivery pressure of 0.8 MPa, this pump was operated up to 5.2 Hz. [ABSTRACT FROM PUBLISHER]

A resonant magnetostrictive motor was built and tested. Its stator modules are made of a ring and two Terfenol-D linear actuators. Two resonant modes of the modules (a translation mode and a flexure mode) are coupled in order to produce elliptical vibrations which are used to transmit motion to two rotors by friction. A low rotating speed of 100/spl deg//s, and a torque of about 2 Nm were reached. Our goal was to show that Terfenol-D can be used for making high torque motors and that resonance can be beneficial for that purpose and for improving efficiency. [ABSTRACT FROM PUBLISHER]