Stiffness of the elastic system in a servo-valve torque motor

Abstract

This article investigates the stiffness of the elastic system in a servo-valve torque motor. A suitable stiffness of the elastic system is necessary because a too low stiffness results in unstable equilibrium while a high stiffness requires a high electric input current. Therefore, designers require an exact estimate of the stiffness of the elastic structure. This article shows that classic beam theory can be used as a design tool for torque motors that have a flexure tube of aspect ratio of about 3 or larger. The beam theory and a finite element method (FEM) analysis are compared with experiments; if the aspect ratio is less than 3, the beam theory induces considerable error and FEM analysis becomes a necessary tool for estimating the elastic characteristics. The benefit of the beam theory is that it can give compact expressions for deflection of the flapper and rotation angle of the armature.