Linear electric actuators are electromagnetic devices capable of producing directly (without any linkages, etc.) progressive unidirectional or oscillatory short-stroke motion. The motion occurs because of the electromagnetic force developed in the actuator. Linear electric generators are also linear motion electromagnetic devices which transform short-stroke oscillatory motion mechanical energy into single-phase ac electrical energy. Just as a rotary electric machine may operate either as a motor or as a generator, a linear motion electromagnetic device may be designed to work either as an actuator or as a generator. From this standpoint, linear electric actuators and generators are the counterparts of a corresponding rotary electric machine. In general, however, linear electric machines have been associated with long linear progressive motion, such as in transportation and similar applications.

Whereas primitive linear electric machines have been in existence for a long time, since the 1960s there has been a great deal of interest in linear machines for various applications—especially transportation. Several books and numerous papers have been published on the subject in the recent past. However, the literature on linear electric actuators and generators is relatively sparse. Clearly, the potential applications of these devices are too numerous to mention here. Judged from the present trend, it would suffice to say that the field of linear actuators and generators may lead to an industry of “linear motion control” with a large worldwide market.