Magnetometer-only linear attitude estimation for bias momentum pico-satellite

Satellite attitude information is essential for pico-satellite applications requiring light-weight, low-power, and fast-computation characteristics. The objective of this study is to provide a magnetometer-only attitude estimation method for a low-altitude Earth orbit, bias momentum pico-satellite. Based on two assumptions, the spacecraft spherical symmetry and damping of body rates, a linear kinematics model of a bias momentum satellite＇s pitch axis is derived, and the linear estimation algorithm is developed. The algorithm combines the linear Kalman filter （KF） with the classic three-axis attitude determination method （TRIAD）. KF is used to estimate satellite＇s pitch axis orientation, while TRIAD is used to obtain information concerning the satellite＇s three-axis attitude. Simulation tests confirmed that the algorithm is suited to the time-varying model errors resulting from both assumptions. The estimate result keeps tracking satellite attitude motion during all damping, stable, and free rotating control stages. Compared with nonlinear algorithms, such as extended Kalman filer （EKF） and square root unscented Kalman filer （SRUKF）, the algorithm presented here has an almost equal performance in terms of convergence time and estimation accuracy, while the consumption of computing resources is much lower.     

自由漂浮双臂空间机器人基于遗传算法的最优运动规划

以多刚体动力学理论为基础,推导了自由漂浮状态双臂空间机器人系统的动量矩守恒关系,转化为系统状态方程;结合基于实数编码的遗传算法实现了双臂空间机器人姿态、关节协调运动的近似最优控制算法.通过控制双臂空间机器人的关节运动,可以同时获得载体姿态及机械臂关节期望的终了位置.仿真算例验证了算法的有效性.     

交流磁轴承支承电主轴转子系统建模

为克服现有混合磁轴承具有的缺陷,提出一种结构新颖的交流混合磁轴承作为高速电主轴的支承部件,永磁体产生偏磁磁通,电磁铁线圈产生控制磁通;介绍了该磁轴承的结构和工作原理,并基于Matlab/Simulink建立了考虑陀螺耦合的电主轴刚性转子和柔性转子四自由度的模型。     

磁线圈感应电场的无量纲化分析和定位

建立了磁刺激的一般模型 ,以了解和预测磁线圈所产生的感应电场的空间分布 .引入无量纲化分析 ,将影响感应电场强度幅度的因素分成两部分 :c(表示刺激条件 )和 E0 (表示线圈几何特性 ) .通过两种磁线圈电场强度三维分布的仿真 ,确定了磁刺激的效果和影响磁刺激聚焦性和深度的因素 .最后 ,利用本文的结论 ,讨论了在设计合理的线圈、磁刺激仪以达到理想刺激效果时确定电场强度幅度、聚焦性和深度的基本原则     

关于带式输送机软起动系统设计的讨论与建议

文章从带式输送机软起动系统的内涵与特征入手，分析了软起动的特点及软起动对带式输送机的重要性等问题。介绍了带式输送机软起动系统的设计方法与符合软起动要求的判定等。介绍了各种软起动系统的性能、特点和各自能解决的问题等。提出了适合带式输送机的软起动和过程控制的起动装置及建议。     

论理解型师生关系的建构

师生之间建立起融洽的理解型的师生关系是教学顺利开展的必要条件。理解型的师生关系是"我"与"你"的平等对话关系。教师只有树立正确的学生观,并从"道德危境"入手,在理想的沟通情境下通过与学生对话,才能达到与学生的"视野融合",真正建立起理解型的师生关系。     

基于Ackermann模型的轮毂电机四轮独立驱动电动汽车电子差速转向控制研究

对四轮独立驱动、四轮独立转向的电动车进行了电子差速控制转向研究,以电控方式控制各个车轮的转速,使车轮以不同速度转动,满足Ackermann转向模型条件,使电动车实现差速转向控制．针对左右前轮转向由各轮转向电机独立控制、左前轮转向不控制、右前轮转向不控制、左右前轮转向都不控制4种转向电机控制方案,进行整车蛇形行驶试验对比,旨在探索是否能够简化转向机构而实现电动汽车转向控制的可行性．     

Hybrid analytical resolution approach based on ambiguity function for attitude determination

When satellite navigation receivers are equipped with multiple antennas, they can deliver attitude information. In previous researches, carrier phase differencing measurement equations were built in the earth-centered, earth-fixed （ECEF） coordinate, and attitude angles could be obtained through the rotation matrix between the body frame （BF） and the local level frame （LLF）. Different from the conventional methods, a hybrid algorithm is presented to resolve attitude parameters utilizing the single differencing （SD） carrier phase equations established in LLF. Assuming that the cycle integer ambiguity is known, the measurement equations have attitude analytical resolutions by using simultaneous single difference equations for two in-view satellites. In addition, the algorithm is capable of reducing the search integer space into countable 2D discrete points and the ambiguity function method （AFM） resolves the ambiguity function within the analytical solutions space. In the case of frequency division multiple access （FDMA） for the Russian Global Orbiting Navigation Satellite System （GLONASS）, a receiver clock bias estimation is employed to evaluate its carrier phase. An evaluating variable and a weighted factor are introduced to assess the integer ambiguity initialization. By static and dynamic ground experiments, the results show that the proposed approach is effective, with enough accuracy and low computation. It can satisfy attitude determination in cases of GPS alone and combined with GLONASS.     

消极体育态度的形成及转变方法和途径

消极体育态度具有一般态度的心理学特点,它是人的内在的心理准备状态,是决定体育行为的潜在因素.消极体育态度的形成与其对体育的认识、体育活动的体验和有否相应的行为意向有关,并受到个体的生活环境和社会实践的影响.因此,只有遵循态度转变的规律,从其心理结构入手,改变体育的认识,情感和意向,优化体育活动环境,控制体育态度的影响因素,才能实现对消极体育态度的有效转变.     

正方形亥姆霍兹线圈的磁场

将正方形载流线圈视为四段载流导线,采用分段计算然后叠加的方法,导出了正方形载流线圈中心轴线上磁场分布的一般表达式.在此基础上,以圆形亥姆霍兹线圈的理论为基础,计算了正方形亥姆霍兹线圈轴线上的磁感应强度,并分析了磁场的均匀性.     

卫星运动补偿技术初步研究

在建立卫星姿态运动学方程与姿态动力学方程的基础上,设计了姿态控制器,仿真结果表明该控制系统具有较好的动态和稳态性能;结合有效载荷的两维伺服控制系统模型,提出了卫星运动补偿方案。使用高精度星敏感器与陀螺组合姿态确定的软件,在各种干扰力矩作用下,对卫星运动补偿进行了数学仿真。结果表明,该方案可以提高有效载荷光轴指向精度和指向稳定度。     

基于模糊控制的电动汽车非线性转向系统控制方法研究

针对四轮独立转向电动汽车,结合轮胎“魔术公式”模型,建立了基于阿克曼转向定理的二自由度非线性转向模型,并提出一种基于模糊策略的方法对其质心侧偏角进行控制.整车系统仿真输入为左前轮车轮转角,模糊控制器以质心侧偏角等于零为控制目标来控制左后轮转角,同时用阿克曼转向定理来调整右前轮和右后轮转角,由此实现四轮独立转向.仿真结果与传统前轮转向、传统四轮比例转向进行比较,结果表明,利用模糊控制对基于阿克曼定理所建立的非线性四轮独立转向模型的控制策略是有效的,控制效果良好.     

某型SUV制动时方向盘抖动问题研究

对某型SUV制动时方向盘抖动问题进行分析,提出了4种抖动控制方案,并运用试验的方法对方案进行优化验证。结果表明,提高大轴套损失系数和前下摆臂大轴套刚度,对制动时方向盘抖动控制改善明显。     

反对称磁垒纳米结构中的电子自旋极化效应

提出了一种反对称磁垒纳米结构,并研究了其电子自旋输运的性质。结果表明,当考虑电子自旋与非均匀磁场的相互作用时,这种磁垒纳米结构具有很强的电子自旋极化效应。而且,电子的自旋极化度与系统的结构参数密切相关,因此通过调整磁条可以调控系统中自旋极化电子的行为。     

非完整冗余空间机器人任务优先级姿态控制

针对空间机器人姿态干扰问题,本文利用非完整冗余逆运动学求解方法,首先提出了对卫星本体不产生姿态干扰的固定姿态控制雅可比矩阵的灵活度准则,其次设计了基于任务优先级的非完整冗余姿态控制算法,最后采用计算机仿真验证了算法的有效性。     

钢轨波磨处高速轮轨滚动接触行为与波磨发展的模拟研究

研究目的：为求解钢轨（短波）波磨处的高速轮轨瞬态滚动接触建立有限元模型,研究影响高速钢轨波磨发展的重要因素。削新要点：1．求解不同牵引条件下轮轨间的瞬态法和切向滚动接触问题,并考虑真实轮轨几何和钢轨波磨,最高模拟速度达500km／h;2．基于模拟结果,解释了中国高速线路上发现的钢轨波磨很快稳定下来的现象。研究方法：1．详细分析钢轨波磨处高速轮轨瞬态滚动接触的法、切向解以及由此导致的V-M等效应力和摩擦功沿轨面的波动;2．变化波磨波长、波深及重要滚动参数如速度和牵引系数等,研究它们对波磨处滚动接触行为的影响;3．对比上述有限元模型与传统多体动力模型在波磨处的法向轮轨力结果。重要结论：1．法、切向轮轨力及法、切向接触应力均随着波磨几何呈周期性波动,但相位略有差异,V-M等效应力和摩擦功的波动形式接近切向接触应力;2．牵引系数越大,波磨处V-M等效应力和摩擦功的波动范围越大;3．名义参数下,对于所研究高铁系统,波长为80mm左右、速度为250-300km／h时波磨的动态响应最大,这与现场观测相符;4．传统多体动力模型会高估钢轨波磨激励的法向轮轨力;5．钢轨波磨会逐渐稳定下来,通过速度越高进入稳定越快。     

电动机示教模型研究

通过对双线圈在磁场中受力情况的分析和磁场空间分布的定性研究,设计出双线圈直流电动机示教模型,此模型结构简单,操作方便,易于维护,可用于中学物理设计性实验教学．     

Classical angular momentum of light: A paradox and its resolution

Angular momentum carried by a classical circularly polarized electromagnetic plane wave (light) appears to be identically zero inasmuch as its linear field-momentum density is directed along wave propagation, and, therefore, the angular momentum, being the integrated moment of the linear momentum density about an axis parallel to the direction of propagation, necessarily vanishes — in detail. This, however, contradicts the established fact that circularly polarized light does carry angular momentum that remains classically non-zero. The paradox is resolved in a physically transparent manner by treating this problem as that of a transversely bounded, and hence necessarily non-trans verse, electromagnetic wave propagating along a circular waveguide, in the limit as its radius tends to infinity. We get a non-zero angular momentum that bears the correct ratio to wave energy. This angular momentum derives essentially and exactly from the boundary conditions for the geometry considered. This is an interesting example of surface terms giving a volume (bulk) contribution, much as in the entirely different context of orbital diamagnetism, which was regarded as a surprise of theoretical physics by Rudolf Peierls.[1]     

Student achievement and attitude in a satellite‐delivered high school science course

Abstract

This study investigated the effect of satellite‐delivered instruction on student achievement and attitude in a high school anatomy and physiology course. The experimental group included students from seven high schools enrolled in the satellite‐delivered course. The control group consisted of students from seven high schools in which classroom teachers provided instruction. An experimental versus control matched‐pair design was used in the study. Two hypotheses were tested using the t test for dependent samples. The findings show that there was no significant difference between the experimental group and control group in attitude toward anatomy and physiology. However, on the achievement test, the mean post‐test score of the experimental group was significantly higher than that of the control group.     

四轮驱动混合动力电动汽车牵引力控制仿真

设计了四轮驱动混合动力电动汽车的构型,并根据其驱动特性制定了牵引力控制方式和协调控制策略,最后运用Matlab/Simulink对附着系数左右分离的特殊路面进行起步与全负荷加速仿真。仿真结果表明,四轮驱动混合动力电动汽车在牵引力控制系统作用下,其驱动性能得到明显的改善,且各控制器亦能根据不同路面和行车工况进行适当调节,保证了四轮驱动混合动力电动汽车的起步加速性、通过性和车身稳定性。