Innovative Flow Servovalve with Redundant Stack Actuator for Pitch Actuation Application

Inhalt:
In the frame of Cleansky “Open Rotor” project managed by Safran Aircraft Engines (SAE), Zodiac Hydraulics (ZH) has developed a new concept of servovalve. ZH present here some of the results of this innovative project. Various technological bricks have been evaluated and combined, in order to optimize the mass and the functional parameters of the equipment which consists of a two-stage jet-pipe flow servovalve with a 17-4 PH steel additive manufacturing body. The displacement of the jet is performed by a redundant high temperature stack piezo actuator manufactured by Physik Instrumente (PI). A specific mobile assembly was designed to allow the mechanical amplification of the displacement and the hydraulic supply of the jet. The advantages of this kind of actuation as compared to the commonly used electro-magnetic torque motor are mostly the increased vibration tolerance of the device, the improvement of the bandwidth, the decreased number of spare parts and magnetic effects immunity. The feedback loop includes an LVDT sensor fixed to the servovalve spool (in order to perform a flow control through the spool position) and laboratory electronic boards. The servovalve itself (hydraulic device including the piezo actuator without the laboratory boards) can operate in nominal conditions with environment and fluid temperature ranging from -10deg C to 130deg C. The servovalve technological readiness level was assessed at TRL4 (Component and/or breadboard validation in laboratory environment) by SAE and ZH.