Development of a new high specific power piezoelectric actuator

Open Access
Loverich, Jacob Joseph
Graduate Program:
Mechanical Engineering
Doctor of Philosophy
Document Type:
Date of Defense:
September 24, 2004
Committee Members:
  • Gary Hugo Koopmann, Committee Chair
  • George A Lesieutre, Committee Chair
  • Eric M Mockensturm, Committee Member
  • Christopher Rahn, Committee Member
  • piezoelectric
  • actuator
  • active material
  • feed screw
  • motion accumulation
Lightweight and powerful (high specific power) electromechanical actuators are essential components for applications such as articulating aircraft flight control surfaces. Fundamental limitations of conventional electromagnetic actuators necessitate the pursuit of new actuation concepts for improved performance. This dissertation explores a novel high specific power density actuator concept based on exploiting the high energy density actuation capacity of piezoelectric materials. The main challenge in developing piezoelectric actuators is harnessing a piezoelectric material’s low-displacement and high-force electric field-induced actuation characteristics to perform large-displacement application-based actuation. In this dissertation, a piezoelectric actuation concept is presented that uses a new feed-screw motion accumulation technique. The feed-screw concept involves accumulating high frequency actuation strokes of a piezoelectric stack (driving element) by intermittently rotating nuts on an output feed-screw. Compared to existing piezoelectric actuator technology, significant features of the feed-screw concept include reversible and robust actuation capability, simple power electronics, and a rigid power-off self-locking state. A prototype feed-screw actuator (developed for a morphing aircraft structure project) demonstrated a 1235 lb blocked force, 29 W peak power output, and 6.1 W/kg specific power. To improve upon the prototype actuator’s 6.1 W/kg specific power, a mathematical model was developed as a design optimization tool. The model is significant because it accounts for nonlinear, nut-screw contact stiffness, and both pre-sliding stiffness and rate-dependent friction behavior. Design optimization results indicate that the feed-screw actuator could potentially achieve a 195 W/kg specific power—a level that is more than double that of a similar size electromagnetic actuator (100% duty cycle).