Study of a linear actuator with a hybrid core using sensorless position control.

• Study of a tubular linear actuator with a hybrid core (permanent magnet and ferromagnetic core) to increase force density. • Sensorless position detection using the variation of the coil current ripple with the variation of the core position. • Actuator prototype composed by a coil fed by a buck DC-DC converter. • Positioning control strategy experimentally tested for constant position and constant load force. In this paper, a study of a tubular linear actuator with a hybrid core is presented. Through a finite-element analysis software and force measurements, it is shown that, by using a hybrid core combining a permanent magnet and a ferromagnetic material, a higher force density can be achieved in relation of that achieved by using a ferromagnetic core alone. Also, by keeping the ferromagnetic part, the sensorless detection of the core position is possible. A simple position control strategy is proposed, using the inductance variation to indirectly detect the position of the core, in which the duty cycle of the PWM voltage is changed to compensate variations of position or load force. In order to experimentally test the linear motor with hybrid core and the proposed control strategy, a prototype and a control circuit were built. The experimental results clearly demonstrate the advantages and applicability of the hybrid core in linear actuators. [ABSTRACT FROM AUTHOR]