Y T Liu

Bio: Y T Liu is an academic researcher. The author has contributed to research in topics: Hysteresis & Plant. The author has an hindex of 1, co-authored 1 publications receiving 10 citations.

Research on giant magnetostrictive micro-displacement actuator with self-adaptive control algorithm

Abstract: Giant magnetostrictive micro-displacement actuator has some unique characteristics, such as big output torque and high precision localization which can be in the nanometer scale. Because the relation between input magnetic field and output strain of giant magnetostrictive micro-displacement actuator exhibits hysteresis and eddy flow, the actuator has to be controlled and used in low input frequency mode or in static mode. When the actuator is controlled with a high input frequency (above 100 Hz), the output strain will exhibit strong nonlinearity. This paper found hysteresis and nonlinearity dynamic transfer function of the actuator based on Jiles-Atherton hysteresis model. The output strain of Jiles-Atherton hystersis model can reflect real output of actuator corresponding to the real input magnetic field, and this has been verified by experiment. Against the nonlinearity generated by hysteresis and eddy flow in this paper, the output strain of actuator is used for feedback to control system, and the control system adopted self-adaptive control algorithm, the ideal input and output model of actuator is used for a reference model and a hysteresis transfer function for the actuator real model. Through experiment, it has been verified that this algorithm can improve the dynamic frequency of the giant magnetostrictive micro-displacement actuator and guarantee high precision localization and linearity between the input magnetic field and output strain of the actuator at the same time.

Dynamic modeling and adaptive vibration control study for giant magnetostrictive actuators

Abstract: Giant magnetostrictive actuators (GMA) used in vibration control and high precision positioning control have been studied widely in last decade. Recently, although many researchers commit themselves to modeling giant magnetostrictive actuators, there is still lack of simplified model of analyzing nonlinear properties to deal with the problems on active vibration control with giant magnetostrictive actuators. In this paper, a nonlinear constitutive model of a giant magnetostrictive actuator is put forward for the application of effectively suppressing vibration. The nonlinear constitutive model is established not only by combining linear constitutive equations with the Bouc–Wen equations but also by using Hamilton's principle and the assumed mode method to analyze the hysteresis phenomena and quadric frequency property in the giant magnetostrictive actuator. In addition, a minimum variance self-turning regulator (MVSTR) is incorporated into the design of a controller, which may be used in suppressing low frequency (≤5 Hz) and micron-level (≤5 μm) disturbances. In the end of this paper, some simulations are performed in LABVIEW and experimental control tests are implemented using a giant magnetostrictive actuator prototype. Both the numerical simulations and experimental tests results show that the amplitudes of disturbances may be reduced up to no less than 90% averagely in the whole sampling processes. This proves that the giant magnetostrictive actuator has not only the capacity of controlling low-frequency and micro-level vibration but also the notable effectiveness of active control by the adaptive regulator. Moreover, the minimum variance self-tuning regulator is testified as a feasible controller for vibration control in the paper.

Research of giant magnetostrictive actuator’s nonlinear dynamic behaviours

Abstract: The multi-coupled nonlinear factors existing in the giant magnetostrictive actuator (GMA) have a serious impact on its output characteristics. If the structural parameters are not properly designed, it is easy to fall into the nonlinear instability, which has seriously hindered its application in many important fields. The electric–magnetic-machine coupled dynamic mathematical model for GMA is established according to J-A dynamic hysteresis model, ampere circuit law, nonlinear quadratic domain model and structure dynamics equation. Nonlinear dynamic analysis method is applied to study the nonlinear dynamic behaviour of the key structure parameters to reveal their influence on the system stability. The design principle of structural parameters is obtained by studying stability of GMA, which provides theoretical basis and technical support for the structural stability design.

Research on Control Strategy in Giant Magnetostrictive Actuator Based on Lyapunov Stability

Abstract: The output characteristics of giant magnetostrictive actuator (GMA) are affected by many nonlinear factors, such as hysteresis, load, driving frequency and so on, which would lead to lower positioning precision, poorer repeatability, and even fall into nonlinear instability especially in complex dynamic environment. First, the accurate dynamic mathematical model for GMA is established after analyzing its working principle. Then, the inverse model feed-forward compensation fuzzy PD control based on Lyapunov stability is put forward and applied into the GMA control system. The experiment results indicate that Lyapunov direct method that is integrated into inverse model feed-forward compensation fuzzy PD controller can effectively improve the dynamic output features especially in the complex dynamic environment, reduce the root mean square error from 1.275 to 0.332 and maximum error rate from 26.89% to 7.12%, which not only greatly improve performance and expand the application domain of GMA, but also have very important theoretical significance and high application value in modeling and control approach for some hysteresis systems.

Monte Carlo technique based geometrical tolerance distribution method for large high-speed rotary equipment

Abstract: The present invention provides a Monte Carlo technique based geometrical tolerance distribution method for large high-speed rotary equipment, and belongs to mechanical tolerance distribution technology. The method comprises: analyzing a propagation process of positioning and orientation tolerances of radial and axial measurement planes of large high-speed rotary equipment; determining a propagation relationship of center coordinates after n-level equipment assembly; obtaining relationships between equipment eccentricity and positioning and orientation tolerances and rotation angles of rotors of each level after the assembly; creating radial eccentricity and axial perpendicularity data of the large high-speed rotary equipment of each level according to a Monte Carlo method; drawing a distribution function to solve a probability density function; and obtaining a probability relationship between radial eccentricity and an axial perpendicularity tolerance of the large high-speed rotary equipment of each level and a final coaxiality tolerance of the multi-level equipment, thereby implementing tolerance distribution of the large high-speed rotary equipment.

Probability density technology based geometrical tolerance distribution method for large high-speed rotary equipment

Abstract: The present invention provides a probability density technology based geometrical tolerance distribution method for large high-speed rotary equipment, and belongs to mechanical tolerance distribution technology The method comprises: analyzing a propagation process of positioning and orientation tolerances of radial and axial measurement planes of large high-speed rotary equipment; determining a propagation relationship of center coordinates after n-level equipment assembly; obtaining relationships between equipment eccentricity and positioning and orientation tolerances and rotation angles of equipment of each level after the assembly; obtaining probability density of a coaxiality tolerance of the n-level equipment according to a target function of the coaxiality tolerance; and finally, obtaining a probability relationship between radial eccentricity and an axial perpendicularity tolerance of the large high-speed rotary equipment of each level and a final coaxiality tolerance of the multi-level equipment, thereby implementing tolerance distribution of the large high-speed rotary equipment