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1

Mobile robot visual homing by vector pre-assigned mechanism

Ji X., Zhu Q., Wang J., Cai C., Ma J.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2019

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Vol. 67, nr 2

213--227

EN

In this paper, we present an optimization mechanism for two popular landmark-based mobile robot visual homing algorithms (ALV and HiSS), called vector pre-assigned mechanism (VPM). VPM contains two branches, both of which can promote the homing performance effectively. In addition, to make the landmark distribution satisfy the equal distance assumption, a landmark optimization strategy is proposed based on imaging principle of the panoramic vision. Experiments on both panoramic image database and a real mobile robot have confirmed the effectiveness of the proposed methods.

2

A machine learning-based mobile robot visual homing approach

Zhu Q., Ji X., Wang J., Cai C.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2018

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Vol. 66, nr 5

621--634

EN

Visual homing enables mobile robots to move towards a previously visited location solely based on panoramic vision sensors. In this paper, a SIFT-based visual homing approach incorporating machine learning is presented. The proposed approach can reduce the impact of inaccurate landmarks on the performance, and generate more precise home direction with simple model. The effectiveness of the proposed approach is verified on both panoramic image databases and actual mobile robot, experimental results reveal that compared to some traditional visual homing methods, the proposed approach exhibits better homing performance and adaptability in both static and dynamic environments.

3

Rotor Displacement Estimation for MB Sensorless Control

Zhu Z., Sun Y., Huang Y., Ji X.

Przegląd Elektrotechniczny

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2012

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R. 88, nr 1b

141-145

EN

This paper presents an on-line recursive least squares support vector machine(O-RLS-SVM)-based displacement estimator for magnetic bearings (MBs). The basic premise of the method is that an O-RLS-SVM forms an efficient mapping structure for a nonlinear MB. Through the measurement of phase flux linkages and currents, the O-RLS-SVM is able to estimate the rotor displacement; thereby it facilitates the elimination of the rotor displacement sensor. Simulation results show that the estimator has high estimation precision and favourable operation efficiency.

PL

W artykule przedstawiono system estymacji położenia wirniku w maszynach z poduszką magnetyczną. System nie wymaga czujników – miarą położenia wirnika są przesunięcia fazowe prądu i strumienia magnetycznego.

4

Displacement Self-sensing of Bearingless Switched Reluctance Motors Based on LS-SVM

Zhu Z., Sun Y., Huang Y., Ji X.

Przegląd Elektrotechniczny

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2012

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R. 88, nr 12a

310-313

EN

To achieve the rotor radial displacement self-sensing for a bearingless switched reluctance motor (BSRM), a new displacement estimation method using least squares support vector machine (LS-SVM) was proposed. Firstly, the working principle and mathematic of a 3-phase 12/8 pole BSRM was introduced in brief. Then taking advantage of LS-SVM with better solution for small-sample learning problem and strong generalization ability, two LS-SVMs were trained off-line to obtain two efficient nonlinear mapping structures to express the dynamic behavior of BSRM. The LSSVM training data set is comprised of representative experimental data with current {i | i = (isa1, isa2, ima)} and rotor position θ as inputs and the corresponding displacements {D | D=(α , β )}as outputs. As well as giving a detailed explanation of the new method, simulation and experimental results were presented. It shows that the proposed LS-SVM-based displacement self-sensing method has high precision and operation efficiency.

PL

W artykule przedstawiono uczący się estymator przesunięcia dla bezłożyskowego silnika o przełączanej reluktancji (BSRM), wykorzystujący metodę LS-SVM (ang. Least Square Support Vector Machines). Opisano zasadę działania i model matematyczny silnika BSRM 3- fazowego 12/8 biegunowego. W celu uzyskania efektywnej struktury mapowania nieliniowego do określenia stanów dynamicznych, zastosowano dwa algorytmy, które zostały nauczone offline. Estymator poddano weryfikacji symulacyjnej i eksperymentalnej.

5

Higher-order space charge field effects on the self-deflection of bright screening spatial solitons in two-photon photorefractive crystals

Jiang Q., Su Y., Ji X.

Optica Applicata

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2010

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Vol. 40, nr 2

481--490

EN

We investigate the effects of higher-order space charge field on the self-deflection of bright screening spatial solitons due to two-photon photorefractive effects by a numerical method under steady-state conditions. The expression for an induced space charge electric field including higher-order space charge field terms is obtained. Numerical results indicate that bright screening solitons undergo self-deflection process during propagation, and the solitons always bend in the opposite direction of the c axis of the crystal. The self-deflection of bright screening solitons can experience considerable increase especially in the regime of high bias field strengths. Relevant examples are provided.

6

Investigation on resonant laser ablation spectrum of Fe in 281.5-285.5 nm wavelength region

Ma J., Ji X., Cui Z.

Optica Applicata

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2008

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Vol. 38, nr 2

405-411

EN

Laser ablation of solid Ti samples has been studied using a tunable pulsed dye laser. Six resonant laser ablation (RLA) spectral lines of Fe in the Ti sample are firstly measured in the 281.5-285.5 nm wavelength region. The initial state of the RLA spectral lines is a5F, the resonant states are z5H0, x5P0 and y5G0, respectively. The influence of laser power density on the intensities of RLA spectrum is discussed. The relationship between the laser wavelength and the photo-ionization cross sections of the resonant state 5G0 is analyzed.