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A simplified quasi-static computational model for self-sensing applications of magnetostrictive actuators based on terfenol-D rods is presented. Paths and angle changes in the magnetic moments rotation of Tb0.3Dy0.7Fe2 alloy are studied as functions of compressive stress and magnetic field, and then used to determine the magnetization in its actuation. Then sensing of magnetic induction picked from a driving coil in an actuator is derived. The model is quick and efficient to solve moments rotation and its magnetization. Sensing results of compressive stress and magnetostriction calculated by the model are in good agreement with experiments and will be helpful in the design and control of self-sensing applications in actuators. [ABSTRACT FROM AUTHOR]

The self-bias magnetoelectric (ME) sensor is designed, fabricated, and characterized for detecting weak ac magnetic-field. The two different magnetostrictive materials produce the gradient of magnetization, resulting in an internal magnetic field and a strong ME response. At zero-biased dc magnetic field, a low-frequency ME voltage coefficient (dVME/dHac) of 22.11 mV/Oe is achieved, which is 17.69 times higher than that of the previous magnets/0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 (PMN-PT) sensor. Furthermore, the ME voltage coefficient reaches 2.73 V/Oe at resonance. The induced ME voltage shows an excellent linear relationship to ac magnetic field when field amplitude varies from ∼10-7 Oe to 1 Oe. [ABSTRACT FROM AUTHOR]

A hybrid nonlinear optimal control design is experimentally implemented on a magnetostrictive Terfenol-D actuator to illustrate enhanced tracking control at relatively high speed. The control design employs a homogenized energy model to quantify rate-dependent nonlinear and hysteretic ferromagnetic switching behavior. The homogenized energy model is incorporated into a finite-dimensional nonlinear optimal control design to directly compensate for the nonlinear and hysteretic magnetostrictive constitutive behavior of the Terfenol-D actuator. Additionally, robustness to operating uncertainties is addressed by incorporating proportional-integral (PI) perturbation feedback around the optimal open loop response. Experimental results illustrate significant improvements in tracking control in comparison to PI control. Accurate displacement tracking is achieved for sinusoidal reference displacements at frequencies up to 1 kHz using the hybrid nonlinear control design, whereas tracking errors become significant for the PI controller for frequencies equal to or greater than 500 Hz. [ABSTRACT FROM AUTHOR]

Many active materials exhibit nonlinearities and hysteresis when driven at field levels necessary to meet stringent performance criteria in high performance applications. This often requires nonlinear control designs to effectively compensate for the nonlinear, hysteretic, field-coupled material behavior. In this paper, an optimal control design is developed to accurately track a reference signal using magnetostrictive transducers. The methodology can be directly extended to transducers employing piezoelectric materials or shape memory alloys due to the unified nature of the constitutive model employed in the control design. The constitutive model is based on a framework that combines energy analysis at lattice length scales with stochastic homogenization techniques to predict macroscopic material behavior. The constitutive model is incorporated into a finite element representation of the magnetostrictive transducer, which provides the framework for developing the finite-dimensional nonlinear control design. The control design includes an open loop nonlinear component computed off-line with perturbation feedback around the optimal state trajectory. Estimation of immeasurable states is achieved using a Kalman filter. It is shown that when operating in a highly nonlinear regime and as the frequency increases, significant performance enhancements are achieved relative to conventional proportional-integral control. [ABSTRACT FROM AUTHOR]

This paper presents a bidirectional wireless swimming microrobot that has been developed, analyzed, and experimentally tested. The robot is developed based on fin beating propulsion, using giant magnetostrictive films for head and tail fins. An innovative drive approach, using separate second order resonance frequencies of the head and tail fins to generate forward and backward thrusts, is proposed and implemented on a bidirectional swimming microrobot prototype. Dynamic model of the proposed microrobot has been derived based on theoretical analysis. Simulation and experimental results have demonstrated the feasibility of the proposed drive approach and design. The developed swimming microrobot features a low driving frequency, low power consumption, and a large range of swimming speed in both the forward and backward directions. [ABSTRACT FROM AUTHOR]