Giant magnetostrictive materials (GMMs) have broad application prospects in the field of servo valves, but the giant magnetostrictive actuator (GMA) has problems such as large loss and severe heat generation, which affect the output effect and accuracy. To solve these problems, this paper designs a stacked giant magnetostrictive actuator (SGMA) and analyzes the magnetic circuit and magnetic field distribution of the SGMA. Based on the magnetic field analysis and the Jiles–Atherton model, we analyze the SGMA magnetization model, simplify the traditional model, and give a solution for the simplified model using the Runge–Kutta method. We analyze the eddy current loss of the SGMA, and according to Bessel’s equation and the Kelvin function, we calculate the relationship among eddy current loss, GMM rod radius, and magnetic field frequency. By analyzing the inherent hysteresis of GMMs, a hysteresis loss model of the SGMA is established in this paper. We also calculate the coil impedance and obtain the coil loss model. Based on the loss model, the SGMA cooling system is designed. Based on the above analysis, we design a SGMA prototype, set-up the corresponding experimental platform, and conduct the necessary experiments. The experimental results show that the SGMA responds well to different signals, but as frequency increases, attenuation, deformation, and hysteresis become more pronounced, which verifies the amplitude and phase changes caused by various losses in the theoretical analysis. The experiment also observes the temperature rise of the oil-cooled SGMA at different frequencies, indicating that the cooling system can effectively control the temperature change of the SGMA, which validates the foregoing analysis.
199 earthquake records with reliable information are selected from the PEER and NIED firstly, and the Seismo Signal software is applied to correct the baseline of original earthquake records. Then the basic characteristics and strength parameters under near-fault/far-field long-period ground motions and common ground motions are compared. Moreover, the influence on basic strength parameters affected by earthquake magnitude, rupture distance (or epicenter distance) and site condition under near-fault/far-field long-period ground motions is analyzed one by one. Study results are obtained as follows: Near-fault earthquake has high amplitude intensity and short strong-shock duration, and its energy release process is concentrated in a short time. A Far-field earthquake has a small peak of acceleration, velocity, displacement and long strong-shock duration, and its energy release process is mild. The strength parameter index PGV/PGA under long-period ground motions is beyond 0.2, and its frequency distribution is concentrated within the low-frequency band (0.1-1.0 Hz) while the frequency distribution of common ground motions is concentrated within a relatively high-frequency band (1.0-2.3 Hz); The strength parameter indexes , , , and under near-fault earthquake are greater than those under far-field earthquake. For a near-fault earthquake, the parameter index PGA decreases, and the strong-shock duration increases with the earthquake magnitude from 6.6 to 7.3, while the parameter index PGA, PGV decreases and PGV/PGA, strong-shock duration increase with the increases of rupture distance. Site-soil condition is the key factor affecting the basic strength parameter index under far-field earthquake, and the PGA, PGV parameter indexes increase under far-field earthquake with the site soil condition from class C to D and E. It is suggested to be related to the effect of filtering out high-frequency components and amplifying low-frequency components in soft site-soil.
Giant magnetostrictive rotary actuators (GMRAs) can realize rotary motion in large scale and with high precision. A series of rectangular voltage signals organized in strict order exerted on GMRA helps its clamping mechanism and driving mechanism complete specific actions such as clamping, loosening, and actuating, thus leading to the stepping output of the rotor. In order to describe the overall performance of GMRA, an angular displacement model is established, which can be divided into four parts, namely, the current model, magnetic field model, output force model, and vibration model. The experimental results indicate that the established model agrees well with the actual performance of GMRA in operating conditions. After that, utilizing the established model, simulations are conducted to analyze the angular response of GMRA. According to the simulation results, the order of driving signals is optimized, making the maximum driving frequency rise from 160 Hz to 210 Hz, while the peak angular speed of GMRA reaches 70.77 mrad/s. The modeling and optimization methods proposed in this paper can be helpful for the structural optimization and controller design of GMRA as well.
Giant magnetostrictive actuators (GMA) are widely used in the field of servo valves, but the displacement of GMA is limited, which renders meeting the requirements of large flow direct-drive electro-hydraulic servo valves (DDV) difficult. In order to solve these problems, this study proposes a double-row bow-type micro-displacement amplifier (DBMA), used to increase output displacement of GMA to meet the requirements. This study, by static analysis, analyzes the force of a flexure hinge based on theoretical mechanics and material mechanics, derives the stiffness matrix of the flexure hinge by the influence coefficient method, establishes the pseudo-rigid model, and derives the amplification ratio of a DBMA. Also, by kinetic analysis, using Castigliano’s second theorem, a formula of equivalent stiffness and natural frequency of DBMA were derived and the influences of different parameters on them were analyzed, respectively. After that, we analyzed the amplifier using finite element method (FEM) simulation software and verified the model by manufacturing a prototype and building a test system. Theoretical calculations and experimental results showed that the amplification ratio of the DBMA fluctuated between 15.43 and 16.25. The natural frequency was about 305 Hz to 314 Hz and the response bandwidth was up to 300 Hz. The error among the theoretical, simulated, and experimental values was within 8%, supporting the accuracy of the model.
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