Hydraulically Amplified Terfenol-D Actuator for Adaptive Powertrain Mounts

Abstract

A magnetostrictive actuator with a stroke of ±1 mm and a blocked force of ±25 N has been developed based on a Terfenol-D driver and a hydraulic stroke amplification mechanism. A mechanical model for this magneto-hydraulic actuator (MHA) is formulated by combining linear piezomagnetic relations for Terfenol-D and a lumped parameter mechanical system model describing the system vibrations. Friction at the fluid seals is described by the LuGre model. The model accurately describes the frequency-domain behavior of the actuator in mechanically-blocked and mechanically-free conditions. The MHA is benchmarked against a commercial electromagnetic driver used in active powertrain mounts in terms of mechanical performance (blocked force and unloaded displacement) and electrical power consumption. Measurements show that the MHA achieves more than twice the frequency bandwidth of the commercial device in the free displacement response, along with comparable static displacements. The commercial device produces higher blocked forces in the frequency range of 10 Hz to 120 Hz beyond which the generated forces are comparable up to 400 Hz. Spectral analysis reveals significant second order components in the commercial actuator displacement response which are absent in the MHA. Further, the MHA achieves superior performance than the commercial actuator operated at maximum current (6 A) with power consumption identical to that of the commercial actuator operated at minimum current (4 A).

Review of magnetostrictive materials for structural vibration control

“…For instance, the engine vibrations ranges from 20Hz to 400Hz, depending on the number of cylinders, the engine speed, and the stroke number [52]. Commercial electrodynamic engine mount actuators can provide a stroke in the millimeter range with a narrow frequency range up to 110 Hz [53]. By arranging several actuators in particular patterns, multiple degrees of freedom (DOFs) vibration control platforms have been developed.…”

“…Hybrid magnetostrictive actuators incorporated with (a) a lever mechanism[51] and (b) a hydraulic cylinder[53].…”

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

“…Evans and Dapino [17] presented a fully coupled dynamic model for 3D magnetostrictive transducers simultaneously incorporating the effects of eddy currents, structural dynamics, and flux leakage on transducer performance. This paper couples the weak form equations presented by Evans and Dapino [18] with a nonlinear energy-averaged constitutive model for Terfenol-D to describe the response of the magneto-hydraulic mount actuator developed by Chakrabarti and Dapino [7]. In order to exploit the axisymmetric geometry of the device, the equations are reduced to a 2D axisymmetric form.…”

“…The former design is more attractive for its simplicity while the latter is more efficient as the displacement of the smart material driver is not degraded by the compliance of the mount. Chakrabarti and Dapino [7] followed the second design principle and combined a magnetostrictive Terfenol-D driver with a sealed hydraulic amplification mechanism. The resulting actuator exhibits superior gain-bandwidth characteristics and less power consumption than a commercial electromagnetic mount actuator used for benchmarking.…”

Bias Magnetic Field of Stack Giant Magnetostrictive Actuator: Design, Analysis, and Optimization

“…For instance, Joshi and Kadoli developed a DC biased GMA with two concentric coils; inductance for both coils with GMM core is, respectively, 16.45 mH and 18.3 mH, the flux leakage of outer coil reaches 12%, and overall radius of outer coil is 4.1 times that of GMM rod [8]. On the other hand, providing bias field through PM requires no electrical power and therefore is more preferred in recent developments [9,10]. However, unlike the DC bias method, bias field from PM cannot be easily tailored, weaker magnets tend to fail their purpose while stronger ones drive GMM to saturation, and it is always challenging to find magnets of appropriate remanent flux density, size, and shape.…”