Robust intelligent modeling for giant magnetostrictive actuators with rate-dependent hysteresis

Purpose–This paper proposes a robust modeling method of a giant magnetostrictive actuator which has a rate-dependent nonlinear property.Design/methodology/approach–It is known in statistics that the Least Wilcoxon learning method developed using Wilcoxon norm is robust against outliers.Thus,it is used in the paper to determine the consequence parameters of the fuzzy rules to reduce the sensitiveness to the outliers in the input-output data.The proposed method partitions the input space adaptively according to the distribution of samples and the partition is irrelative to the dimension of the input data set.Findings–The proposed modeling method can effectively construct a unique dynamic model that describes the rate-dependent hysteresis in a given frequency range with respect to different single-frequency and multi-frequency input signals no matter whether there exist outliers in the training set or not.Simulation results demonstrate that the proposed method is effective and insensitive against the outliers.Originality/value–The main contributions of this paper are:first,an intelligent modeling method is proposed to deal with the rate-dependent hysteresis presented in the giant magnetostrictive actuator and the modeling precision can fulfill the requirement of engineering,such as the online modeling issue in the active vibration control;and second,the proposed method can handle the outliers in the input-output data effectively.

Structure design and characteristics analysis of a cylindrical giant magnetostrictive actuator for ball screw preload

In order to achieve automatic adjustment of the double-nut ball screw preload, a magnetostrictive ball screw preload system is proposed. A new cylindrical giant magnetostrictive actuator （CGMA）, which is the core component of the preload system, is developed using giant magnetostrictive material （GMM） with a hole. The pretightening force of the CGMA is determined by testing. And the magnetic circuit analysis method is introduced to calculate magnetic field intensity of the actuator with a ball screw shaft. To suppress the thermal effects on the magnetostrictive outputs, an oil cooling method which can directly cool the heat source is adopted. A CGMA test platform is established and the static and dynamic output characteristics are respectively studied. The experimental results indicate that the CGMA has good linearity and no double-frequency effect under the bias magnetic field and the output accuracy of the CGMA is significantly improved with cooling measures. Although the output decreased with screw shaft through the actuator, the performance of CGMA meets the design requirements for ball screw preload with output displacement more than 26 μm and force up to 6200 N. The development of a CGMA will provide a new approach for automatic adjustment of double-nut ball screw preload.

Research on Giant Magnetostrictive Actuator for Turning Vibration Control

Magnetostriction is a phenomenon in which a magneti c field is used to produce a change in size of some materials. This property has b een known in elements such as nickel, iron and cobalt. Because the rare-ear th alloy Terfenol-D can offer much larger strains than nickel, iron, cobalt, an d other smart materials such as piezoelectric materials, it is called giant magn etostrictive material. Making use of the giant magnetostrictive material, the gi ant magnetostrictive actuator has higher bandwidth and rapider response than oth er actuators. So it is widely used in active vibration control, especially in lo w frequency stage. In this paper, a turning vibration control system is develope d. The system has an actuator clamped in a flexor that is rigid in the feed and main cutting force directions, yet is flexible in the radial direction. The stru cture of the giant magnetostrictive actuator is developed after magnetic circuit and some structure parameter are calculated. According to the turning frequency , the transient and stable-state output of the giant magnetostrictive actuator is measured. The test result demonstrated that the actuator responses the input rapidly, and the actuator has perfect stable-state and transient output charact eristic. The characteristic includes the stable-state output linearity, repeata bility and transient delay between output displacement and input current.

Theory and experiment of observer based magnetostrictive self-sensing actuator

Giant magnetostrictive actuators (GMAs) often work in a close-loop feedback system. This system needs independent sensors which may be difficult to be fixed, besides, excessive sensors may cause more unpredicted problems in a large system. This paper aims to develop a self-sensing GMA. An observer based on piezomagnetic equations is constructed to estimate the stress and strain of the magnetostrictive material. The observer based self-sensing approach depends on the facts that the magnetic field is controllable and that the magnetic induction is measurable. Aiming at the nonlinear hysteresis in magnetization, a hys- teresis compensation observer based on Preisach model is developed. Experiment verified the availability of the observer approach, and the hysteresis compensation observer has higher tracking precision than linear observer for dynamic force sensing.

Magnetostrictive and Kinematic Model Considering the Dynamic Hysteresis and Energy Loss for GMA

Due to the influence of magnetic hysteresis and energy loss inherent in giant magnetostrictive materials （GMM）, output displacement accuracy of giant magnetostrictive actuator （GMA） can not meet the precision and ultra precision machining. Using a GMM rod as the core driving element, a GMA which may be used in the field of precision and ultra precision drive engineering is designed through modular design method. Based on the Armstrong theory and elastic Gibbs free energy theory, a nonlinear magnetostriction model which considers magnetic hysteresis and energy loss characteristics is established. Moreover, the mechanical system differential equation model for GMA is established by utilizing D＇Alembert＇s principle. Experimental results show that the model can preferably predict magnetization property, magnetic potential orientation, energy loss for GMM. It is also able to describe magnetostrictive elongation and output displacement of GMA. Research results will provide a theoretical basis for solving the dynamic magnetic hysteresis, energy loss and working precision for GMA fundamentally.

NEW KIND OF WIRELESS MICRO ROBOT ACTUATED AND CONTROLLED THROUGH OUTSIDE MAGNETIC FIELD

A new method to drive and control micro in-pipe robot by means of magneticfield outside pipe is put forward, in which wireless micro robot can move forward driven by thevibration of its legs through converting magnetic energy into mechanical one under the action ofpiezomagnetism and magnetomechanical coupling of its micro GMA, when time varied oscillatingmagnetic field with different frequency applied outside pipe. Firstly its systematical structure andoperation principle are introduced, and energy converting process from outside magnetic one intomechanical one is analyzed through setting up the magnetic and mechanical dynamic model of GMA andestablishing dynamic model of two stage amplifier of mobile earner. Robot systematical experimentsshow the correctness of the theoretical analysis and its feasibility. As a result, drive and controlmethod without cable through outside magnetic field is realized.