基于畸变偏移矢量的结构光区域标定

针对结构光测量系统直接标定法存在的物像映射模型全局适用性差问题,提出了一种基于畸变模型的分区域标定方法。首先,用张正友平面标定法则估计相机的线性成像投影矩阵。然后,将该矩阵作为初值,通过最小二乘法求解相机的畸变参数。最后,根据畸变偏移矢量分布规律划分出图像子区间并进行标定。在相同场景中的实验结果表明,相比全局直接标定方法,本方法在X方向和Y方向的标定精度分别提升了37.40%和56.20%,在结构光测量领域具有广泛的适用性。

射频板条CO_2激光器整形光路自适应调节研究

为了解决射频板条CO2激光器因安装或腔镜热畸变造成的光路偏移问题,采用外光路偏移补偿的方法对其进行校正。研究了基于压电陶瓷的偏移补偿装置,设计了压电陶瓷驱动电路,并分析了控制精度和自适应控制方法。结果表明,通过偏移补偿装置,激光输出功率在任何占空比下均可达到或超过标准参考功率值,并通过对比有无自适应调节,激光输出功率最大相差100W,且可保持激光输出功率在2h运行中波动小于2%。此项研究可保证激光器高效运行,提高激光器的输出功率和模式的稳定性,具有较大的实用价值。

The stationary phase analysis of the Kirchhoff-type d emigrated field

In the literature,stationary phase analysis of Kirchhoff-type demigrated fields is carried out mainly under the following two conditions：（1） The considered isochrone and the target reflector are tangential to each other;（2） The spatial duration of the wavelet of the depthmigrated image is short.For the isochrones that are not tangential to the target reflector and for the depth-migrated images that have a large spatial duration,the published stationary phase equation for the demigrated field will become invalid.For performing the stationary phase analysis of the Kirchhoff-type demigrated field under the conditions that the considered isochrone and the target reflector are not tangential to each other and that the spatial duration of the wavelet of the depth-migrated image is not short（the general conditions）,I derive the formulas for the factors appearing in the stationary phase formula in two dimensions,from which I find that for different isochrones the horizontal coordinates of the stationary point of the depth difference function are different.Also,the equation for the Kirchhoff-type demigrated field consists of two parts.One is the true-amplitude demigrated signal and the other is the amplitude distortion factor.From these facts the following two conclusions can be drawn：（1） A demigrated signal is composed of many depth-migrated images and one depth-migrated image trace provides only one sample to the demigrated signal;and（2） The amplitude distortion effect is an effect inherent in the Kirchhoff-type demigration and cannot be eliminated during demigration.If this effect should be eliminated,one should do an amplitude correction after demigration.

Simplified Method of Valence Band Offset Calculation at Strained Layer Heterojunction

The average bond energy method is popularized and applied to study band offsets at strained layer heterojunctions. By careful examination of hydrostatic and uniaxial strain actions on the band offset parameter Emv,it is found that the average band offset parameter Emv,av=Em-Ev, av remains basically unchanged under different strain conditions. Therefore, provided the band offset parameter before strain Emv,0 of bulk material is calculated, and the experiment values of deformation potential b and spin-orbit （SO） splitting energy △0 are quoted, the Emv at strained layer can be obtained by a simple and convenient algebraic calculation. Thus the valence band offset △Ev at strained layer heterojunction can also be predicted conveniently. This simplified calculation method is characterized by decreased calculation amount and increased conviction due to use as many as possible the experiment values.

Study on Valence Band Offsets atStrained Heterojunctions

A method, which can predict the valence band offsets at strained layer heterojunctions under different strain situations only by calculating band structures and deformation parameters of the bulk materials, is suggested. The applicability of this method is verified by calculation of the valence band offsets at strained layer heterojuntions ,such as InP/InAs, InP/GaP, GaAs/InAs, GaP/GaAs and AlAs/InAs with various strain conditions.

Multiple target implementation for a doubly fed induction generator based on direct power control under unbalanced and distorted grid voltage

This paper presents a multiple target implementation technique for a doubly fed induction generator （DFIG） under unbalanced and distorted grid voltage based on direct power control （DPC）. Based on the mathematical model of DFIG under unbalanced and distorted voltage, the proportional and integral （PI） regulator is adopted to regulate the DFIG average active and reactive powers, while the vector P1 （VPI） resonant regulator is used to achieve three alternative control targets： （1） balanced and sinusoidal stator current; （2） smooth instantaneous stator active and reactive powers; （3） smooth electromagnetic torque and instantaneous stator reactive power. The major advantage of the proposed control strategy over the conventional method is that neither negative and harmonic sequence decomposition of grid voltage nor complicated control reference calculation is required. The insensitivity of the proposed control strategy to DFIG parameter deviation is analyzed. Finally, the DFIG experimental system is developed to validate the availability of the proposed DPC strategy under unbalanced and distorted grid voltage,