磁制导AGV实验装置的研制

为满足机械工程及自动化专业实验教学的需要,研制了磁制导AGV实验装置。介绍了该装置的总体结构、制导原理、控制系统和软件。实践表明,该装置柔性好,可靠性高,制作费用低。

基于磁检测的AGV导引新方法

利用磁阻传感器作为磁导引路径的检测元件,实现了准确的磁路径定位,在此基础上实现了磁导引。详细介绍了磁检测方法、导引原理以及控制方案。当AGV产生一定范围的位置偏差时(水平偏移不大于±5cm,角度偏转不大于±25°),该方法可以准确的检测并计算出位置偏差并进行相应控制。实验结果表明,该磁导引方式定位准确且易于实现。

A practical robust nonlinear controller for maglev levitation system

In order to explore the precise dynamic response of the maglev train and verify the validity of proposed controller,a maglev guideway-electromagnet-air spring-cabin coupled model is developed in the first step.Based on the coupled model,the stresses of the modules are analyzed,and it is pointed out that the inherent nonlinearity,the inner coupling,misalignments between the sensors and actuators,and external disturbances are the main issues that should be considered for the maglev engineering.Furthermore,a feedback linearization controller based on the mathematical model of a maglev module is derived,in which the nonlinearity,coupling and misalignments are taken into account.Then,to attenuate the effect of external disturbances,a disturbance observer is proposed and the dynamics of the estimation error is analyzed using the input-to-state stability theory.It shows that the error is negligible under a low-frequency disturbance.However,at the high-frequency range,the error is unacceptable and the disturbances can not be compensated in time,which lead to over designed fluctuations of levitation gap,even a clash between the upper surface of electromagnet and lower surface of guideway.To solve this problem,a novel nonlinear acceleration feedback is put forward to enhancing the attenuation ability of fast varying disturbances.Finally,numerical comparisons show that the proposed controller outperforms the traditional feedback linearization controller and maintains good robustness under disturbances.

A study of EV induction motor controller based on rotor flux oriented control

Induction motor is a multi-parameter, non-linear and strong coupling system, which requires efficient control algorithms. In this paper, rotor flux oriented control （FOC） algorithm based on voltage source inverter-fed is deduced in detail, including stator voltage compensation, closed-loop PI parameters＇ calculation of torque and rotor flux. FOC＇ s Simulink model is setup to simulate torque and rotor flux＇s response. At last, the experimental results are shown.

An Extended Extrinsic Mechanism for Anomalous Hall Effect

The extrinsic mechanism for anomalous Hall effect in ferromagnets is extended to include the contributions both from spin-orbit-dependent impurity scattering and from the spin-orbit coupling induced by external electric fields. The results obtained suggest that, within the framework of the extrinsic mechanisms, the anomalous Hall current in a ferromagnet may also contain a substantial amount of dissipationless contribution independent of impurity scattering. After the contribution from the spin-orbit coupling induced by external electric fields is included, the total anomalous Hall conductivity is about two times larger than that due to soin-orbit dependent impurity scatterings.

Dependences of spin polarization on the control parameters in the spin-polarized injection through the magnetic p-n junction

Effective spin-polarized injection from magnetic semiconductor （MS） to nonmagnetic semiconductor （NMS） has been highlighted in recent years. In this paper we study theoretically the dependence of nonequilibrium spin polarization （NESP） in NMS during spin-polarized injection through the magnetic p-n junction. Based on the theory in semiconductor physics, a model is established and the boundary conditions are determined in the case of no external spin-polarized injection and low bias. The control parameters that may influence the NESP in NMS are indicated by calculating the distribution of spin polarization. They are the doping concentrations, the equilibrium spin polarization in MS and the bias. The effective spin-polarized injection can be realized more easily by optimizing the above parameters.

Induced polarization in a 2.5D marine controlled source electromagnetic field based on the adaptive finite-element method

The induced polarization （IP） in rocks and minerals is of significance to the marine controlled-source electromagnetic （CSEM） field. We propose an adaptive finite-element algorithm for the 2.5D frequency-domain forward modeling of marine CSEM that considers the induced polarization. The geoelectrical model is discretized using an unstructured triangular elemental grid that accommodates the complex topography and geoelectrical structures. We use the Cole-Cole model to describe the IP and develop a complex resistivity forward modeling algorithm. We compare the simulation results with published 1D model results and subsequently calculate the electromagnetic field for variable azimuth sources, IP parameters, and topography. Finally, we analyze the IP effect on the marine CSEM field and show that IP of oil reservoirs and topography affects the marine CSEM electromagnetic field.

Spin filtering magnetic modulation and spin-polarization switching in hybrid ferromagnet/semiconductor structures

Electron spin-polarization modulation with a ferromagnetic strip of in-plane magnetization is analyzed in a hybrid ferromagnet/semiconductor filter device.The dependencies of electron spin-polarization on the strip’s magnetization strength,width and position have been systematically investigated.A novel magnetic control spin-polarization switch is proposed by inserting a ferromagnetic metal(FM)strip eccentric in relation to off the center of the spin filter,which produces the first energy level spin-polarization reversal.It is believed to be of significant importance for the realization of semiconductor spintronics multiple-value logic devices.

Electromagnetically Induced Transparency and Absorption of A Monochromatic Light Controlled by a Radio Frequency Field

Electromagnetically induced transparency and absorption of a monochromatic light controlled by a radio frequency field in the cold multi-Zeeman-sublevel atoms are theoretically investigated. These Zeeman sublevels are coupled by a radio frequency （RF） field. Both electrom^gnetically induced transparency and electromagnetically induced absorption can be obtained by tuning the frequency of RF field for both the linear polarization and elliptical polarization monochromatic lights. When the transfer of coherence via spontaneous emission from the excited state to the ground state is considered, electromagnetically induced absorption can be changed into electromagnetically induced transparency with the change of intensity of radio field. The transparency windows controlled by the RF field can have potential applications in the magnetic-field measurement and quantum information processing.

Titanium doped kagome superconductor CsV_(3-x)Ti_(x)Sb_(5)and two distinct phases

The vanadium-based kagome superconductor CsV_(3)Sb_(5) has attracted tremendous attention due to its unexcepted anomalous Hall effect(AHE),charge density waves(CDWs),nematicity,and a pseudogap pair density wave(PDW)coexisting with unconventional strong-coupling superconductivity.The origins of CDWs,unconventional superconductivity,and their correlation with different electronic states in this kagome system are of great significance,but so far,are still under debate.Chemical doping in the kagome layer provides one of the most direct ways to reveal the intrinsic physics,but remains unexplored.Here,we report,for the first time,the synthesis of Ti-substituted CsV_(3)Sb_(5) single crystals and its rich phase diagram mapping the evolution of intertwining electronic states.The Ti atoms directly substitute for V in the kagome layers.CsV_(3-x)Ti_(x)Sb_(5) shows two distinct superconductivity phases upon substitution.The Ti slightly-substituted phase displays an unconventional V-shaped superconductivity gap,coexisting with weakening CDW,PDW,AHE,and nematicity.The Ti highly-substituted phase has a U-shaped superconductivity gap concomitant with a short-range rotation symmetry breaking CDW,while long-range CDW,twofold symmetry of in-plane resistivity,AHE,and PDW are absent.Furthermore,we also demonstrate the chemical substitution of V atoms with other elements such as Cr and Nb,showing a different modulation on the superconductivity phases and CDWs.These findings open up a way to synthesise a new family of doped CsV_(3)Sb_(5) materials,and further represent a new platform for tuning the different correlated electronic states and superconducting pairing in kagome superconductors.

Uniform wurtzite MnSe nanocrystals with surface-dependent magnetic behavior

Manganese selenide （MnSe） possesses unique magnetic properties as an important magnetic semiconductor, but the synthesis and properties of MnSe nanocrystals are less developed compared to other semiconductor nanocrystals because of the inability to obtain high-quality MnSe, especially in the metastable wurtzite structure. Here, we have successfully fabricated wurtzite MnSe nanocrystals via a colloidal approach which affords uniform crystal sizes and tailored shapes. The selective binding strength of the amine surfactant is the determining factor in shape-control and shape-evolution. Bullet-shapes could be transformed into shuttle-shapes if part of the oleylamine in the reaction solution was replaced by trioctylamine, and tetrapod-shaped nanocrystals could be formed in trioctylamine systems. The three-dimensional （3D） structure of the bullet-shaped nanorods has been demonstrated by the advanced transmission electron microscope （TEM） 3D-tomography technology. High-resolution TEM （HRTEM） and electron energy-loss spectroscopy （EELS） show that planar-defect structures such as stacking faults and twinning along the [001] direction arise during the growth of bullet-shapes. On the basis of careful HRTEM observations, we propose a ＂quadra-twin core＂ growth mechanism for the formation of wurtzite MnSe nanotetrapods. Furthermore, the wurtzite MnSe nanocrystals show low- temperature surface spin-glass behavior due to their noncompensated surface spins and the blocking temperatures increase from 8.4 K to 18.5 K with increasing surface area/volume ratio of the nanocrystals. Our results provide a systematic study of wurtzite MnSe nanocrystals.