Control of a direct-drive servo-valve actuated by a linear amplified piezoelectric actuator for aeronautic applications

In direct-drive servo-valves, the motion of the spool controlling the direction of the hydraulic fluid flow is directly controlled by an electrical motor. Owing to the small stroke needed, it is possible to use a linear amplified piezoelectric actuator directly connected to the spool. The aim of this paper is to investigate how to design the power and control electronics of a direct-drive servo-valve based on a linear amplified piezoelectric actuator in order to take full advantage of such a motor. In particular, it will be shown that the voltage applied on the piezoelectric stacks may be successfully controlled by use of four-quadrant choppers with the benefits that the injected electrical charge stored in their capacity can be recovered. This leads to the low consumption scheme presented which can be easily fed by a boost converter from the aircraft 28 VDC.