A magnetostrictive reaction mass actuator possessing a large force to weight ratio has recently been developed at SatCon Technology Corporation. Achieving such high performance requires adequate modeling of this multidisciplinary device. The developed models allow performance optimization to be accomplished through parameter selection and control design.At the 1996 smart materials conference, the modeling and design issues associated with this actuator were discussed. Since that time, additional experiments and optimization have been performed that validate the proposed modeling. These experiments include validation of the thermal modeling and dynamic model validation through control experimentation. In addition to these results, a discussion of the trade-offs in terms of eddy current, controller, and thermal requirements, will be presented.
SatCon is developing linear and rotary motors that rely on the peristaltic motion ofa Terfenol-D element along a tight-fitting channel. Magnetostrictive inchworm motors offer extended or unlimited travel, as well as those attributes normally associated with magnetostrictive actuators: high force and torque densities, quick response, and fme resolution motion. Unlike Kiesewetter's cylindrical design, the Terfenol-D element is a rectangular slab placed between two tight-fitting plates that are spring-loaded to maintain proper contact in spite of wear. Also, the excitation coils do not enclose the Terfenol-D element, allowing extension ofthe concept to rotary motors. A model for inchworm performance has been developed, based on observations of a prototype linear inchworm motor. Speed is approximately the product of peak magnetostrictive strain and phase velocity of the magnetic field, but is reduced by the fmite extent ofthe contact zone between the Terfenol-D and the plates. As a result, speed drops with load, since magnetostrictive strain is reduced and the contact zone grows longer with increasing applied load. The speed was limited by the skin effect present in the Terfenol-D element. A second prototype employs composite Terfenol-D with its high resistivity, in order to permit operation at higher speeds. SatCon is also developing a rotary motor and making improvements to the design of linear motors.
A magnetostrictive peristaltic motor, similar to an INCHWORM® motor, was designed, built, and tested, using Terfenol-D® as the active element. Unlike the Kiesewetter motor, which uses a rod of Terfenol-D in a closely fitting cylindrical channel, in our design the Terfenol-D is in the form of a flat slab, held between two spring-loaded plates. With this configuration the motor is not affected by wear of the Terfenol-D surface. In order to avoid eddy currents, we used laminated Terfenol-D. Operating at 1600 Hz with a peak field of 430 oersteds, the speed at no load was observed to be 12 mm/sec, which is 65% of the theoretical value (the peak strain times the peristaltic phase velocity), probably because the surface flatness of the Terfenol-D slab was only a few times smaller than the height of the peristaltic bumps. The measured stalling force was 90 newtons, corresponding to 350 kPa load stress in the Terfenol-D, only 3.5% of the peak strain times the stiffness of the Terfenol-D. This force was in almost exact agreement with a model which took into account the force from the spring-loaded plates (needed to avoid slippage), the transverse stiffness of the Terfenol-D slab, and the finite bending stiffness of the stator. The model can be used to design optimized motors with improved force capability. We tried using composite Terfenol-D, consisting of Terfenol-D particles in an epoxy binder, but the speed and stalling force were lower, perhaps because it did not have a very uniform distribution of particles, and was not machined as flat as the laminated Terfenol-D. The motor was driven by a specially designed 3-phase power inverter and digital controller, and the large reactive power inherent in this kind of motor was reduced by putting it in series with resonant capacitors.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.