Active Fault Tolerant Control of an Unmanned Surface Vehicle

Zhixiang Liu,Youmin Zhang,Chi Yuan 제어로봇시스템학회 2015 제어로봇시스템학회 국제학술대회 논문집 Vol.2015 No.10

This paper presents an active fault tolerant control methodology with application to an unmanned surface vehicle (USV). Firstly, an augmented linear quadratic regulator (LQR) scheme is developed to guarantee the desired control performance and stability of USV in the absence of actuator faults. Secondly, an additional control mechanism incorporating a fault estimator and an adaptive fault compensator are synthesized to asymptotically stabilize the closedloop system in the event of actuator faults. Based on a nonlinear USV model, simulation results validated the effectiveness of the proposed control approach in either the absence or presence of actuator faults.

Efficient degradation of methylene blue dye by catalytic oxidation using the Na_8Nb_6O_19.13H_2O/H_2O-2 system

Chengtang Liu,Huaming Li,Hui Xu,Ling Liu,Li Xu,Zhixiang Ye 한국화학공학회 2011 Korean Journal of Chemical Engineering Vol.28 No.4

Na_8Nb_6O_19.13H_2O particles were synthesized by a simple hydrothermal method. The catalysts were characterized by X-ray diffraction (XRD), scanning electronic microscopy (SEM) and thermogravimetric and differential scanning (TG-DSC). The XRD and TG-DSC analyses indicated that Na_8Nb_6O_19.13H-2O was an intermediate hexaniobate during the preparation of NaNbO_3 powders. Methylene blue (MB) dye degradation using Na_8Nb_6O_19.13H_2O/H_2O_2,Nb_2O_5/H_2O_2 and NaNbO_3/H_2O_2 systems were investigated, respectively. Among the catalytic oxidation systems, Na_8Nb_6O_19·13H_2O showed the highest activity for degradation of MB in the presence of H_2O_2. The results indicated that the dye degradation efficiency could be 93.5% at 30 ℃ after 60 min in the presence of the Na_8Nb_6O_19·13H_2O/H_2O-2 system. It was also found that the degradation of MB over the catalytic systems followed pseudo-first-order kinetics, and the degradation rate was 0.02376 min−1 in the Na_8Nb_6O_19.13H_2O/H_2O_2 system, which was higher than that in the Nb_2O_5/H_2O_2and NaNbO_3/H_2O_2 systems. A possible mechanism for MB catalytic oxidation degradation using the Na_8Nb_6O_19.13H-2O/H_2O_2 system was proposed.

Experimental study on the influence of Reynolds number and roll angle on train aerodynamics

Zhixiang Huang,Wenhui Li,Tanghong Liu,Li Chen 한국풍공학회 2022 Wind and Structures, An International Journal (WAS Vol.35 No.2

When the rolling stocks run on the curve, the external rail has to be lifted to a certain level to balance the centrifugal force acting on the train body. Under such a situation, passengers may feel uncomfortable, and the slanted vehicle has the potential overturning risks at high speed. This paper conducted a wind tunnel test in an annular wind tunnel with φ=3.2 m based on a 1/20th scaled high-speed train (HST) model. The sensitivity of Reynolds effects ranging from Re = 0.37×106 to Re = 1.45×106 was tested based on the incoming wind from U=30 m/s to U=113 m/s. The wind speed covers the range from incompressible to compressible. The impact of roll angle ranging from γ=0° to γ=4° on train aerodynamics was tested. In addition, the boundary layer development was also analyzed under different wind speeds. The results indicate that drag and lift aerodynamic coefficients gradually stabilized and converged over U=70 m/s, which could be regeared as the self-similarity region. Similarly, the thickness of the boundary layer on the floor gradually decreased with the wind speed increase, and little changed over U=80 m/s. The rolling moment of the head and tail cars increased with the roll angle from γ=0° to γ=4°. However, the potential overturning risks of the head car are higher than the tail car with the increase of the roll angle. This study is significant in providing a reference for the overturning assessment of HST.

Second Order Impulsive Neutral Functional Differential Inclusions

Liu, Yicheng,Li, Zhixiang Department of Mathematics 2008 Kyungpook mathematical journal Vol.48 No.1

In this paper, we investigate the existence of solutions of second order impulsive neutral functional differential inclusions which the nonlinearity F admits convex and non-convex values. Some results under weaker conditions are presented. Our results extend previous ones. The methods rely on a fixed point theorem for condensing multivalued maps and Schaefer's fixed point theorem combined with lower semi-continuous multivalued operators with decomposable values.

COMPONENT RESISTANCE PREDICTION IN COMPOUND CHANNELS

LIU XINGNIAN,ZHANG ZHIXIANG,YANG KEJUN,CAO SHUYOU 한국수자원학회 2005 한국수자원학회 학술대회 Vol.2005 No.1

Immobilization and Performance of Penicillin G Acylase on Magnetic Ni_0.7Co_0.3Fe₂O₄@SiO₂-CHO Nanocomposites

( Zhixiang Lv ),( Qingmei Yu ),( Zhou Wang ),( Ruijiang Liu ) 한국미생물생명공학회(구 한국산업미생물학회) 2019 Journal of microbiology and biotechnology Vol.29 No.6

Magnetic Ni_0.7Co_0.3Fe₂O₄ nanoparticles that were prepared via the rapid combustion process were functionalized and modified to obtain magnetic Ni_0.7Co_0.3Fe2O₄@SiO₂-CHO nanocomposites, on which penicillin G acylase (PGA) was covalently immobilized. Selections of immobilization concentration and time of fixation were explored. Catalytic performance of immobilized PGA was characterized. The free PGA had greatest activity at pH 8.0 and 45 ℃ while immobilized PGA’s a ctivities p eaked at p H 7.5 and 4 5 ℃. Immobilized PGA had better thermal stability than free PGA at the range of 30-50 ℃ for different time intervals. The activity of free PGA would be 0 and that of immobilized PGA still retained some activities at 60 ℃ after 2 h. V_max and K_m of immobilized PGA were 1.55 mol/min and 0.15 mol/l, respectively. Free PGA’s V_max and K_m separately were 0.74 mol/min and 0.028 mol/l. Immobilized PGA displayed more than 50% activity after 10 successive cycles. We concluded that immobilized PGA with magnetic Ni_0.7Co_0.3Fe₂O₄@SiO₂-CHO nanocomposites could become a novel example for the immobilization of other amidohydrolases.

An Analysis of the Uneven Tool Electrode Wear Mechanism in the Micro-electrical Discharge Machining Process

Zhixiang Zou,Xiaoyu Zhang,Kangcheung Chan,Tai-Man Yue,Zhongning Guo,Can Weng,Jiangwen Liu 한국정밀공학회 2023 International Journal of Precision Engineering and Vol.10 No.6

Micro-electrical discharge machining (micro-EDM) has an issue of uneven tool electrode wear that seriously affects the micro-hole accuracy. However, the mechanism of uneven tool electrode wear remains unclear. In this study, the uneven tool electrode wear mechanism has been studied both theoretically and experimentally. It was first discovered that the ultrafine debris particles produced by the EDM spark play a critical role in uneven tool electrode wear. A theoretical model was established to reveal the movement and the distribution of the debris by employing Einstein’s tea leaf paradox i.e., classic secondary flow theory and the electrophoretic theory. According to this model, when the polarity is positive, the ultrafine debris aggregates gradually and adheres onto the bottom of the micro-hole, thereby a debris layer of a parabolic profile is formed progressively. This dynamic debris layer shields the material to be removed by the EDM spark. As a result, the tip of the tool electrode is unevenly worn into a conical concavity shape. Conversely, under negative polarity, the tip of the tool electrode is unevenly worn into a conical shape. A set of experiments was performed to verify the model and the results agreed well with the predicted phenomena. Subsequently, a novel approach is proposed to eliminate the uneven tool electrode wear by reversing pulse polarity in a repetitive manner. Using this method, uneven tool electrode wear can be avoided and high accuracy micro-holes without the features of a cone and/or conical concavity can be obtained.

New PWM predictive control suitable for low carrier ratio of permanent magnet synchronous motor drive systems

Lu, Jinnan,Liu, Zhixiang,Zeng, Wei,Ren, Ze The Korean Institute of Power Electronics 2021 JOURNAL OF POWER ELECTRONICS Vol.21 No.6

The drive inverters for high-power motors often need to reduce the carrier ratio (usually by reducing the lower switching frequency) to increase its capacity. However, the low carrier ratio results in motor control performance degradation. In this paper, an inverter and a permanent magnet synchronous motor (PMSM) are integrated to establish a unified prediction model with the delay caused by sampling and modulation that cannot be ignored under a low carrier ratio. Based on this model, a new PWM predictive control suitable for low carrier ratio (PPC-LCR) is proposed, which has better stability, dynamic performance, model accuracy and robustness under a low carrier ratio. To further enhance the control accuracy of the proposed strategy, prediction errors by parameter mismatch are analyzed, and a correction method of feedbacking the last beat prediction error is proposed to compensate for model error and parameter mismatch. Finally, experimental results are presented to support theoretical analysis and the proposed strategy.

Airflow over low-sloped gable roof buildings: Wind tunnel experiment and CFD simulations

Ruizhou Cao,Zhixiang Yu,Zhixiang Liu,Xiaoxiao Chen,Fu Zhu 한국풍공학회 2020 Wind and Structures, An International Journal (WAS Vol.31 No.4

In this study, the impact of roof slope on the flow characteristics over low-sloped gable roofs was investigated using steady computational fluid dynamics (CFD) simulations based on a k- SST turbulence model. A measurement database of the flow field over a scaled model of 15° was created using particle image velocimetry (PIV). Sensitivity analyses for the grid resolutions and turbulence models were performed. Among the three common Reynolds-averaged Navier-Stokes equations (RANS) models, the k- SST model exhibited a better performance, followed by the RNG model and then the realizable k- model. Next, the flow properties over the differently sloped (0° to 25°) building models were determined. It was found that the effect of roof slope on the flow characteristics was identified by changing the position and size of the separation bubbles, 15° was found to be approximately the sensitive slope at which the distribution of the separation bubbles changed significantly. Additionally, it is suggested additional attention focused on the distributions of the negative pressure on the windward surfaces (especially "5" ° and "10" ° roofs) and the possible snow redistribution on the leeward surfaces.

Low Frequency Current Ripple Mitigation of Two Stage Three-Phase PEMFC Generation Systems

Deng, Huiwen,Li, Qi,Liu, Zhixiang,Li, Lun,Chen, Weirong The Korean Institute of Power Electronics 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.6

This paper presents a two stage three-phase proton exchange membrane fuel cell (PEMFC) generation system. When the system is connected to a three-phase load, it is very sensitive to the characteristics and type of the load. Especially unbalanced three-phase loads, which result in a pulsating power that is twice the output frequency at the inverter output, and cause the dc-link to generate low frequency ripples. This penetrates to the fuel cell side through the front-end dc-dc converter, which makes the fuel cell work in an unsafe condition and degrades its lifespan. In this paper, the generation and propagation mechanism of low frequency ripple is analyzed and its impact on fuel cells is presented based on the PEMFC output characteristics model. Then a novel method to evaluate low frequency current ripple control capability is investigated. Moreover, a control scheme with bandpass filter inserted into the current feed-forward path, and ripple duty ratio compensation based on current mode control with notch filter is also proposed to achieve low frequency ripple suppression and dynamic characteristics improvement during load transients. Finally, different control methods are verified and compared by simulation and experimental results.