Ruijin Wang

Bio: Ruijin Wang is an academic researcher from Hangzhou Dianzi University. The author has contributed to research in topics: Hysteresis & Bearing (mechanical). The author has an hindex of 2, co-authored 3 publications receiving 13 citations.

A new hysteresis modeling and optimization for piezoelectric actuators based on asymmetric Prandtl-Ishlinskii model

Abstract: Piezoelectric actuators are core components in micromanipulation systems in the field of biomedicine. The asymmetrical hysteresis of piezoelectric actuators greatly affects its performance, and the existing asymmetric hysteresis models are either inaccurate or complicated. In this paper, an accurate and simple asymmetric hysteresis model is proposed based on the Prandtl-Ishlinskii (PI) model. Firstly, the Play operator is modified to be asymmetric to enhance its flexibility, and the influence of parameters on the operator is analyzed. Secondly, the Asymmetric Prandtl-Ishlinskii (API) model is proposed based on the asymmetric Play operator and verified by experiment. Compared with several existing models, the API model can describe the asymmetric hysteresis in a more accurate and simple manner under the same conditions. Thirdly, the parameters of the API model are optimized. Compared with the unoptimized API model, the optimized one can reduce the number of parameters and maintain high accuracy. Furthermore, the influence of the order on accuracy is discussed, and a guidance for selection of the order is provided. Last but not least, the optimized API model is used to compensate for the hysteresis. The experimental results show that the compensator based on this model can effectively suppress the hysteresis of the piezoelectric actuator.

Research on Asymmetric Hysteresis Modeling and Compensation of Piezoelectric Actuators with PMPI Model.

Abstract: Because of fast frequency response, high stiffness, and displacement resolution, the piezoelectric actuators (PEAs) are widely used in micro/nano driving field. However, the hysteresis nonlinearity behavior of the PEAs affects seriously the further improvement of manufacturing accuracy. In this paper, we focus on the modeling of asymmetric hysteresis behavior and compensation of PEAs. First, a polynomial-modified Prandtl-Ishlinskii (PMPI) model is proposed for the asymmetric hysteresis behavior. Compared with classical Prandtl-Ishlinskii (PI) model, the PMPI model can be used to describe both symmetric and asymmetric hysteresis. Then, the congruency property of PMPI model is analyzed and verified. Next, based on the PMPI model, the inverse model (I-M) compensator is designed for hysteresis compensation. The stability of the I-M compensator is analyzed. Finally, the simulation and experiment are carried out to verify the accuracy of the PMPI model and the I-M compensator. The results implied that the PMPI model can effectively describe the asymmetric hysteresis, and the I-M compensator can well suppress the hysteresis characteristics of PEAs.

Air flotation main shaft axial dynamic stiffness adaptive device based on micro disturbance and method thereof

Abstract: The invention discloses an air flotation main shaft axial dynamic stiffness adaptive device based on micro disturbance and a method thereof. At present, the stiffness of an air floating main shaft cannot be adjusted in real time during machining. The air flotation main shaft axial dynamic stiffness adaptive device comprises a frame, the main shaft, a radial bearing I, a radial bearing II, an air flotation thrust bearing I, an air flotation thrust bearing II, a cylindrical piezoelectric ceramic actuator and a micro-displacement capacitance sensor. According to the air flotation main shaft axialdynamic stiffness adaptive device based on the micro disturbance and the method thereof, the dynamic stiffness of the main shaft is changed under the action of the micro disturbance by utilizing theair flotation bearing, the axial vibration amplitude of the air flotation main shaft is measured through the micro-displacement capacitance sensor, whether the dynamic stiffness of the air flotation thrust bearing meets the machining requirement or not is indirectly obtained, and if the dynamic stiffness is not met, so that the cylindrical piezoelectric ceramic actuator is driven to drive the airflotation thrust bearing to generate micro-amplitude vibration. By changing the vibration frequency, the dynamic stiffness of the air flotation thrust bearing is changed, and the self-adaptive onlineadjustment of the axial dynamic stiffness of the main shaft is realized.

Modeling and Compensation for Asymmetrical and Dynamic Hysteresis of Piezoelectric Actuators Using a Dynamic Delay Prandtl-Ishlinskii Model.

Abstract: Piezoelectric actuators are widely used in micro- and nano-manufacturing and precision machining due to their superior performance. However, there are complex hysteresis nonlinear phenomena in piezoelectric actuators. In particular, the inherent hysteresis can be affected by the input frequency, and it sometimes exhibits asymmetrical characteristic. The existing dynamic hysteresis model is inaccurate in describing hysteresis of piezoelectric actuators at high frequency. In this paper, a Dynamic Delay Prandtl–Ishlinskii (DDPI) model is proposed to describe the asymmetrical and dynamic characteristics of piezoelectric actuators. First, the shape of the Delay Play operator is discussed under two delay coefficients. Then, the accuracy of the DDPI model is verified by experiments. Next, to compensate the asymmetrical and dynamic hysteresis, the compensator is designed based on the Inverse Dynamic Delay Prandtl–Ishlinskii (IDDPI) model. The effectiveness of the inverse compensator was verified by experiments. The results show that the DDPI model can accurately describe the asymmetrical and dynamic hysteresis, and the compensator can effectively suppress the hysteresis of the piezoelectric actuator. This research will be beneficial to extend the application of piezoelectric actuators.

Temperature-dependent asymmetric Prandtl-Ishlinskii hysteresis model for piezoelectric actuators

Abstract: Abstract A temperature-dependent asymmetric Prandtl-Ishlinskii (TAPI) model is developed to describe changes in hysteresis curves with respect to temperature found in the displacement curves vs. input voltage of a piezoelectric actuator (PEA). The proposed modeling scheme considers nonlinearities in an idealized capacitor term in the electromechanical model of the PEA to introduce both asymmetry and temperature dependence in the model. The developed model has the advantage of incorporating asymmetric and thermal effects in a hysteresis-free region of the model which simplifies inversion of the model as well as parameter determination. A parameter identification scheme is described to simplify model identification, even for a large number of thresholds, based on the advantages of the classical Prandtl-Ishlinskii model. The TAPI model is verified experimentally and a compensator is designed to demonstrate that the PEA output is effectively linearized throughout the temperature range.

Advanced Trajectory Control for Piezoelectric Actuators Based on Robust Control Combined with Artificial Neural Networks

Abstract: In applications where high precision in micro- and nanopositioning is required, piezoelectric actuators (PEA) are an optimal micromechatronic choice. However, the accuracy of these devices is affected by a natural phenomenon called “hysteresis” that even increases the instability of the system. This anomaly can be counteracted through a material re-shape or by the design of a control strategy. Through this research, a novel control design has been developed; the structure contemplates an artificial neural network (ANN) feedforward to contract the non-linearities and a robust close-loop compensator to reduce the unmodelled dynamics, uncertainties and perturbations. The proposed scheme was embedded in a dSpace control platform with a Thorlabs PEA; the parameters were tuned online through specific metrics. The outcomes were compared with a conventional proportional-integral-derivative (PID) controller in terms of control signal and tracking performance. The experimental gathered results showed that the advanced proposed strategy had a superior accuracy and chattering reduction.

Research on Precision Blanking Process Design of Micro Gear Based on Piezoelectric Actuator.

Abstract: In order to process micro scale parts more conveniently, especially the micro parts with complex shape, a new micro blanking equipment based on piezoelectric ceramic driving is proposed in this paper. Compared with other large precision machining equipment, the equipment cost has been greatly reduced. Using displacement sensor to detect the change of output displacement and feedback control piezoelectric actuator to control the change of relevant parameters, the control precision is high. The micro gear parts with diameter less than 2 mm are obtained through the blanking experiment on the experimental equipment. From the relationship between the obtained time and the punch output force, output displacement and die adjustment, it can be seen that the designed equipment has good processing performance and can complete the blanking forming of micro parts well.

Temperature-dependent asymmetric Prandtl-Ishlinskii hysteresis model for piezoelectric actuators

Abstract: A temperature-dependent asymmetric Prandtl-Ishlinskii (TAPI) model is developed to describe changes in hysteresis curves with respect to temperature found in the displacement curves vs. input voltage of a piezoelectric actuator (PEA). The proposed modeling scheme considers nonlinearities in an idealized capacitor term in the electromechanical model of the PEA to introduce both asymmetry and temperature dependence in the model. The developed model has the advantage of incorporating asymmetric and thermal effects in a hysteresis-free region of the model which simplifies inversion of the model as well as parameter determination. A parameter identification scheme is described to simplify model identification, even for a large number of thresholds, based on the advantages of the classical Prandtl-Ishlinskii model. The TAPI model is verified experimentally and a compensator is designed to demonstrate that the PEA output is effectively linearized throughout the temperature range.