Modal-based model reduction and vibration control for uncertain piezoelectric flexible structures

Xu Yalan,Chen Jianjun 국제구조공학회 2008 Structural Engineering and Mechanics, An Int'l Jou Vol.29 No.5

In piezoelectric flexible structures, the contribution of vibration modes to the dynamic response of system may change with the location of piezoelectric actuator patches, which means that the ability of actuators to control vibration modes should be taken into account in the development of modal reduction model. The spatial H2 norm of modes, which serves as a measure of the intensity of modes to system dynamical response, is used to pick up the modes included in the reduction model. Based on the reduction model, the paper develops the state-space representation for uncertain flexible tructures with piezoelectric material as non-collocated actuators/sensors in the modal space, taking into account uncertainties due to modal parameters variation and unmodeled residual modes. In order to suppress the vibration of the structure, a dynamic output feedback control law is designed by imultaneously considering the conflicting performance specifications, such as robust stability, transient response requirement, disturbance rejection, actuator saturation constraints. Based on linear matrix inequality, the vibration control design is converted into a linear convex optimization problem. The simulation results show how the influence of vibration modes on the dynamical response of structure varies with the location of piezoelectric actuators, why the uncertainties should be considered in the reductiom model to avoid exciting high-frequency modes in the non-collcated vibration control, and the possiblity that the conflicting performance specifications are dealt with simultaneously.

Fuzzy control for geometrically nonlinear vibration of piezoelectric flexible plates

Xu, Yalan,Chen, Jianjun Techno-Press 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.43 No.2

This paper presents a LMI(linear matrix inequality)-based fuzzy approach of modeling and active vibration control of geometrically nonlinear flexible plates with piezoelectric materials as actuators and sensors. The large-amplitude vibration characteristics and dynamic partial differential equation of a piezoelectric flexible rectangular thin plate structure are obtained by using generalized Fourier series and numerical integral. Takagi-Sugeno (T-S) fuzzy model is employed to approximate the nonlinear structural system, which combines the fuzzy inference rule with the local linear state space model. A robust fuzzy dynamic output feedback control law based on the T-S fuzzy model is designed by the parallel distributed compensation (PDC) technique, and stability analysis and disturbance rejection problems are guaranteed by LMI method. The simulation result shows that the fuzzy dynamic output feedback controller based on a two-rule T-S fuzzy model performs well, and the vibration of plate structure with geometrical nonlinearity is suppressed, which is less complex in computation and can be practically implemented.

Numerical investigation of supercavity geometry and gas leakage behavior for the ventilated supercavities with the twin-vortex and the re-entrant jet modes

Xu Haiyu,Luo Kai,Dang Jianjun,Li Daijin,Huang Chuang 대한조선학회 2021 International Journal of Naval Architecture and Oc Vol.13 No.1

To investigate the supercavity geometry and gas flow structure for the supercavities with two closure types under the different flow conditions, an inhomogeneous multiphase model with the SST turbulence model was established, and validated by experimental results. The results show that two distinct regions exist inside the supercavity, which include the downstream flow region along the gas-water interface and the reverse flow region. For the twin-vortex supercavity, the internal gas leaks from the supercavity boundary by two paths: the supercavity surface and the two-vortex tubes. Increasing Froude number leads to more internal gas stripped from the supercavity surface. Two types of gas loss exist for the reentrant jet supercavity with high Froude number, one type is the steady process of gas loss, and the major gas-leaking path is the supercavity surface rather than supercavity closure region. The other type is the unsteady periodic ejection, and the gas cluster of periodic ejection is merely a small part of the gas stored inside the supercavity.

Investigation of dynamic characteristics of planetary gear stage in wind turbine considering voltage dip

Jianjun Tan,Caichao Zhu,Chaosheng Song,Xiangyang Xu,Zi Wang 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.9

The transient variation of electrical parameters makes system loads fluctuate and reduces bearing capacity when the grid voltage dips. This work proposes an electromechanical coupling dynamic model of the wind turbine drivetrain to build a dynamic interconnection between the electric and drivetrain subsystems. The drivetrain subsystem that includes an improved model of the planetary gear stage is developed and validated. This improved model considers the carrier and planet bearing clearances, the connection relationship among the carrier, main shaft, and planets as well as the flexibilities of the main shaft and parallel stage shafts. The influences of the carrier bearing clearances, non-torque load and planet position angle on planet bearing loads are investigated under the low-voltage ride through (LVRT) event. The results indicate that as the LVRT occurs, the planet bearing loads reduce below the minimum requisite with a high, fluctuating system speed; considering the bearing clearances, the impacts occur in the planet bearing in the minimum load zone followed by significant stress variation; the non-torque load suppresses the planet bearing impacts in a limited range of carrier bearing clearance; the planet position angle has a significant effect on the planet bearing impacts because of the asymmetry of load and structure of the planetary gear stage.

Modal-based mixed vibration control for uncertain piezoelectric flexible structures

Yalan Xu,Yu Qian,Jianjun Chen,Gangbing Song 국제구조공학회 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.55 No.1

H-infinity norm relates to the maximum in the frequency response function and H-infinity control method focuses on the case that the vibration is excited at the fundamental frequency, while 2-norm relates to the output energy of systems with the input of pulses or white noises and 2-norm control method weighs the overall vibration performance of systems. The trade-off between the performance in frequency-domain and that in time-domain may be achieved by integrating two indices in the mixed vibration control method. Based on the linear fractional state space representation in the modal space for a piezoelectric flexible structure with uncertain modal parameters and un-modeled residual high-frequency modes, a mixed dynamic output feedback control design method is proposed to suppress the structural vibration. Using the linear matrix inequality (LMI) technique, the initial populations are generated by the designing of robust control laws with different H-infinity performance indices before the robust 2-norm performance index of the closed-loop system is included in the fitness function of optimization. A flexible beam structure with a piezoelectric sensor and a piezoelectric actuator are used as the subject for numerical studies. Compared with the velocity feedback control method, the numerical simulation results show the effectiveness of the proposed method.

Fire Resistance Numerical Simulation of Extended End-Plate Steel Connection Joints with Different Strengthening Strategies under Fire

Jixiang Xu,Jianjun Wang,Jianping Han,Zhaolong Han,Jiahuang Tu,Zhanjie Li 대한토목학회 2022 KSCE JOURNAL OF CIVIL ENGINEERING Vol.26 No.4

The aim of this paper is to investigate the bolted end-plate beam to column (BEBC) joints with different strengthening strategies under fire through a parametric study by using a validated computational model. The current studies are mainly more focused on the mechanical behavior of a certain kind of reinforced or unreinforced BEBC joints at either room or fire alone, limiting investigations are available for a comprehensive stiffening strategy study of the BEBC joints under fire. Therefore, there is a need in improving the performance of BEBC joints with different stiffening strategies, the fire resistance comparison of these BEBC joints with different strengthening strategies under fire is of great interest. The analyses of the fire resistance behavior of the stiffened or unstiffened BEBC joints under fire were conducted by using a developed model that was established and validated by using the existing test results. A parametric study was conducted for BEBC joints with web stiffeners, end-plate stiffeners and web and end-plate stiffeners together under fire using the validated computational model. In order to better compare the fire resistance of BEBC joints with different strengthening strategies under a fire, 24 finite element models were established by considering different strengthening strategies and end-plate thicknesses. The results on different strengthening strategies and the end-plate thicknesses revealed the major impact of web stiffeners and end-plate web stiffener together, and the sensitivities of end-plate thickness for unreinforced BEBC joints. For the fire resistance of unreinforced and stiffened BEBC joints, the findings herein can provide a valuable reference for potential design recommendations.

Modal-based model reduction and vibration control for uncertain piezoelectric flexible structures

Yalan, Xu,Jianjun, Chen Techno-Press 2008 Structural Engineering and Mechanics, An Int'l Jou Vol.29 No.5

In piezoelectric flexible structures, the contribution of vibration modes to the dynamic response of system may change with the location of piezoelectric actuator patches, which means that the ability of actuators to control vibration modes should be taken into account in the development of modal reduction model. The spatial $H_2$ norm of modes, which serves as a measure of the intensity of modes to system dynamical response, is used to pick up the modes included in the reduction model. Based on the reduction model, the paper develops the state-space representation for uncertain flexible tructures with piezoelectric material as non-collocated actuators/sensors in the modal space, taking into account uncertainties due to modal parameters variation and unmodeled residual modes. In order to suppress the vibration of the structure, a dynamic output feedback control law is designed by imultaneously considering the conflicting performance specifications, such as robust stability, transient response requirement, disturbance rejection, actuator saturation constraints. Based on linear matrix inequality, the vibration control design is converted into a linear convex optimization problem. The simulation results show how the influence of vibration modes on the dynamical response of structure varies with the location of piezoelectric actuators, why the uncertainties should be considered in the reductiom model to avoid exciting high-frequency modes in the non-collcated vibration control, and the possiblity that the conflicting performance specifications are dealt with simultaneously.

Fuzzy control for geometrically nonlinear vibration of piezoelectric flexible plates

Yalan Xu,Jianjun Chen 국제구조공학회 2012 Structural Engineering and Mechanics, An Int'l Jou Vol.43 No.2

This paper presents a LMI(linear matrix inequality)-based fuzzy approach of modeling and active vibration control of geometrically nonlinear flexible plates with piezoelectric materials as actuators and sensors. The large-amplitude vibration characteristics and dynamic partial differential equation of a piezoelectric flexible rectangular thin plate structure are obtained by using generalized Fourier series and numerical integral. Takagi-Sugeno (T-S) fuzzy model is employed to approximate the nonlinear structural system, which combines the fuzzy inference rule with the local linear state space model. A robust fuzzy dynamic output feedback control law based on the T-S fuzzy model is designed by the parallel distributed compensation (PDC) technique, and stability analysis and disturbance rejection problems are guaranteed by LMI method. The simulation result shows that the fuzzy dynamic output feedback controller based on a two-rule T-S fuzzy model performs well, and the vibration of plate structure with geometrical nonlinearity is suppressed, which is less complex in computation and can be practically implemented.

Current Decoupling Scheme of Three-Phase Inverter with Complex Coefficient Controller

Zheng Xinxin,Xu Jianjun,Shi Jingkui,Huang Wenxin,Li Qiyue 대한전기학회 2022 Journal of Electrical Engineering & Technology Vol.17 No.6

In the control of three-phase system, AC signals are always changed into DC signals by synchronous coordinate transformation. A decoupling control scheme in the dq synchronous reference frame (SRF) is proposed to realize active and reactive current decoupling of three-phase inverter. The complex vector control model is established in SRF. Diff erent from the model established in static reference frame, the SRF control model can refl ect the coupling characteristic of the active and reactive current. As a result, the PI controller with complex coeffi cient can be applied to realize current decoupling. In this paper, the coupling characteristic of three-phase system is analyzed. A novel complex PI controller design method is proposed based on the SRF control model and the coeffi cients are calculated. And its implementation in the control loop is given. Compared with existing PI controllers with real or complex coeffi cients, the proposed complex PI controller can realize completely the decoupling of the active and reactive current in three-phase system. Besides, the control scheme can make current loop fulfi ll the expected symmetrical bandwidth, so as to realize a higher eff ective set-off frequency. As a result, the inverter can achieve well dynamic performance. Finally, the simulation and experimental results are given to verify the theoretical analysis.

The Research on network Losses Allocation of Power Market based on Improved REI Network Numerical Equivalence

Lei Shi,Jianjun Xu,Limei Yan 보안공학연구지원센터 2016 International Journal of u- and e- Service, Scienc Vol.9 No.11

The main purpose of this paper is how to allocate network losses of power market, and takes this as objective function of this paper. Then we have conducted an in-depth analysis and discussion to the commonly-used algorithm of network losses allocation of each country. On this basis, we have chosen power flow tracking algorithm, and carried on in-depth analysis, then found out the shortcomings and areas for improvement. For the shortcomings, we have introduced REI network numerical equivalence method, and applied it to the improved power flow tracing algorithm of this paper. Moreover, we have verified four-node and three-machine nine-node network system, and proved the rationality of the model. Therefore, the proposed method in this paper was applied to bidirectional network losses allocation model. Generator and load undertook network losses of each electronic component according to certain proportion. In this paper, complex power flow tracing algorithm was applied to four-node system and the western U.S. power grid WSCC three-machine nine-node system, verifying the validity and correctness of this algorithm.