1996-08-01

High Force Electric Linear Motors 961800

SatCon is developing electric machines to produce more torque or force within a given volume Some are novel multi-air gap configurations which employ the same operating principles as conventional machines Others employ smart materials As linear motors or actuators, these machines offer an alternative to hydraulicsDirect drive electric linear motors fail to match the force capability of hydraulics As a result, rotary motors have been combined with gear reducers and ball or lead screws to create a high force linear actuator This approach, although effective in many situations, is often too sluggish to employ for applications requiring rapid response and maneuvering Simply speaking the inertias of the motor and gear reducer consume an unacceptably large fraction of the force capability of these actuatorsIn response to these limitations, SatCon has conceived of a permanent magnet-based linear electric actuator which employs multiple air gaps The most basic configuration resembles a “sandwich”, where permanent magnet (PM) shuttle plates are placed between multiple wound stator plates Only the end stator plates require return iron This approach is effective in achieving high torque within a given envelope, because additional force-producing air gaps are provided without the penalty of added return iron and housingsA second approach employs a magnetostrictive material in an “inch-worm” configuration The “inch-worm” approach has been implemented with piezoelectrics for low force, high precision positioning For higher force applications, there has been limited development of magnetostrictive inch-worm devices Unlike the PM actuator, it holds its position when power is removed SatCon has developed a novel configuration of this approach which could serve as an alternative to hydraulic actuators

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