Coupled axisymmetric finite element model of a hydraulically amplified magnetostrictive actuator for active powertrain mounts

摘要

A coupled axisymmetric finite element model is formulated to describe the dynamic performance of a hydraulically amplified magnetostrictive actuator for active powertrain mounts. The formulation is based on the weak form representations of Maxwell's equations for electromagnetics and Navier's equation for mechanical systems coupled using a nonlinear magnetomechanical constitutive law for terbium-dysprosium-iron (Terfenol-D). Fluid structure interaction is modeled by computing a bulk fluid pressure based on the volumetric deformation of the fluid chamber and coupling the fluid pressure to the structure through traction on the boundaries encompassing the fluid. Seal friction is quantified using the LuGre friction model. The resulting model equations are coded into the commercial finite element package COMSOL, which is used for meshing and global assembly of matrices. Results show that the model accurately describes the dynamic mechanical and electrical responses of the actuator. A parametric study performed using this model reveals that the actuator's unloaded displacement can be improved by up to 140% by doubling the thickness of the fluid chamber components and reducing seal friction to a fourth of its original value. Other parameters such as permeability and conductivity of the permanent magnet and fluid bulk modulus have a minor effect on actuator performance.