Philipp Zagar, Rudolf Scheidl,
"A piezo-electrically actuated valve for hydraulic exoskeleton drives ? modelling and measurement of a prototype"
: Proceedings of the 2022 IEEE Global Fluid Power Society PhD Symposium, October 12-14 2022, Napoli, Italy., 2022
A piezo-electrically actuated valve for hydraulic exoskeleton drives ? modelling and measurement of a prototype
Sprache des Titels:
Proceedings of the 2022 IEEE Global Fluid Power Society PhD Symposium, October 12-14 2022, Napoli, Italy.
This paper deals with the development of a prototypefor a piezo-electrically actuated hydraulic spool valve whichshall be used as a low-power, miniaturized hydraulic valve fore.g. exoskeleton applications where size, weight and efficiencyplays a crucial role. The two main ideas of the hydraulic valveare (i) using a buckling beam as an element which amplifies thedisplacement of the piezo stack and provides bistable behaviorand (ii) introducing a resonant mechanical system consistingof the valve?s spool and two springs which is excited by thecoupling to the piezo stack. The resulting valve is a bistable,piezo-electrically switched hydraulic 4/2-valve. The paper firstexplains the valve concept and the design of the valve prototype.A mathematical model for the piezoelectric actuator is derivedby using higher order beam theory. A Ritz-Ansatz is introducedto get approximate expressions for the beam displacement andwhich proves to predict measurements very well. In a nextstep, the model is extended to describe the complete system.This system consists of a lumped, quasi-static piezo stack modelwhich is coupled to the approximated beam solution, equationsof motion of the spool and hydraulics. Numerical simulationsprove the working principle of the valve and give insights ofhow parameters such as the spring stiffness affect the switchingtime and the pressure built-up at the output of the valve.