自动清洗纽带入口反旋强化的动力矩计算方法研究及其应用

运用动量矩定理建立了入口反旋强化纽带的自动清洗动力矩计算式。应用该计算式进行了以自转动力矩强化为目标的结构设计和优化试验及其工程应用研究,获得了重要的结果。其中2030型反旋强化轴承座的冲推力矩使2 000 mm长的纽带自转力矩增大235%,能够显著地降低纽带自转流速要求,并且阻力只有1.5 kPa,结构简单,成本低廉。该技术适于在0.9 m/s左右流速的传热设备中推广应用,尤其在传热管长度不大时效果更为显著。     

高转速制导弹药中惯性测量组合的研究

针对现有陀螺仪的量程无法用于高转速制导弹药轴向角速度测量的缺点,提出了一种适合于高转速制导弹药的2陀螺和4加速度计的惯性测量组合配置方案,根据加速度计的输出公式,得出载体质心处的线加速度和角速度的解算公式。最后,以方位误差为基础,对该方案进行了仿真,得到了相应的误差曲线。     

Computer-aided modeling of dielectric and ferroelectric properties

In this article the concept of charges fluctuating in double well potentials is used as a basis for a quantitative computer calculation of interactions between permanent dipoles. Numerical calculations are of advantage, because the dipole-dipole interaction energy can exceed the thermal energy. In this case nonlinearities can arise, which are difficult to treat analytically. Furthermore, a numerical recalculation of the Lorentz field resulting from induced dipoles has been carried out. Within the Lorentz calculation of the local field, two models are used in juxtaposed position: a discrete model, which takes account of dipoles inside a conceptual sphere, and a continuum model, which treats the dipoles outside this sphere as a continuum. Using both models the local field at the center dipole of the sphere is calculated. It is shown that several dielectric and ferroelectric properties can be calculated using very simple model assumptions     

永磁同步电动机混沌运动的完全精确线性化控

永磁同步电动机在一定条件下或参数处于某特定区域会发生混沌现象,这影响了电动机运行的性能。根据微分几何理论,利用完全精确线性化的方法,设计出控制混沌的控制律。该方法以转子角速度为控制变量,通过电动机的非线性反馈进行解耦,转子角速度可以根据跟踪设定其稳定点。这个控制律可以使系统稳定在某一平衡点,而且这个平衡点不是唯一的,这样可以根据情况设定平衡点,满足了实际需要。实验仿真表明,利用完全精确线性化的可以使系统消除混沌,达到了新的平衡,这证实了控制律的有效性。     

Feedback control in ancient water and mechanical clocks

Attention is focused on Ktesibios' water clock and the outstanding mechanical clocks based on the crown wheel escapement that first appeared in Europe at the end of the thirteenth century. Specifially, block diagrams and the related equations are derived for both the Ktesibios and the verge and foliot clock. The essential role of feedback for controlling the speed of such devices is pointed out. In particular, each mechanical clock discussed can be regarded as a sampled-feedback control system. This explains why the average angular velocity of the wheel would be constant even in the absence of friction. The operation of the verge and foliot clock is compared to that of the pendulum clock built by Ch. Huygens in the seventeenth century     

面向PDR定位系统的多层感知机IMU阵列数据融合方法

为提高低成本惯性测量单元(intertial measurement unit, IMU)阵列的行人航位推算(pedestrian dead reckoning, PDR)定位精度,首次提出了采用多层感知机(multi-layer perceptron, MLP)实现低成本IMU阵列数据融合的算法,通过将自主设计的IMU阵列和高精度IMU同步运动来获得IMU阵列的测量数据(包括三轴加速度和三轴角速度)和高精度IMU的测量数据,以高精度IMU的测量数据作为标签,利用MLP将IMU阵列的测量数据融合,预测出物体的实际加速度和角速度,并用定位算法进行验证。在定位实验中,使用MLP融合后的预测数据的PDR定位精度比使用单个IMU测量数据的PDR定位精度提高了33.9%;比使用简单平均处理的IMU阵列测量数据的PDR定位精度提高了20.8%;比使用最小二乘法融合的IMU阵列测量数据的PDR定位精度提高了11.6%,证明了本文所提出方法的可行性和有效性。     

Adaptive robust output feedback control for attitude tracking of quadrotor unmanned aerial vehicles

This work proposes a new adaptive robust output feedback control method for attitude reference tracking of a quadrotor unmanned aerial vehicle without using the angular velocity measurements. By using the K-filters well known in the adaptive control community, the necessity of velocity measurements or estimating is avoided. The attitude system model is transformed into a second-order model where the angular velocity measurements are not involved. However, the model includes mismatched uncertainties which should be estimated and compensated by the disturbance observers (DOBs). The controller is designed in a backstepping manner, and the dynamic surface technique is adopted to avoid the explosion of the controller complexity. For each Euler angle axis, the prescribed performance control technique is adopted to ensure a prescribed performance, the lumped disturbance is compensated by a DOB, and furthermore an adaptive law is introduced to adaptively update the corresponding uncertain inertia parameter which affects the control performance significantly. The control performance of the overall control system is analyzed rigorously from the viewpoint of input-to-state practical stability. In addition, it is shown how the adaptive laws contribute to improving the control performance. And simulation examples are provided to demonstrate the performance of the proposed method.     

无角速度测量的姿态跟踪动态PD控制

针对太阳帆板展开过程中存在系统切换和外部未知干扰的航天器姿态跟踪控制问题,提出了角速度可测和角速度不可测的姿态跟踪自适应动态比例微分(PD)控制器。本文先设计自适应更新律补偿外部复合干扰,提出了姿态角及角速度全状态可测的自适应PD控制器;接着针对角速度不可量测,基于无源控制理论给出估算角速度的动态观测器,提出一种仅有姿态角跟踪误差信息的变增益动态PD控制器,并理论证明了闭环系统的全局渐近稳定性;数值仿真验证了变增益动态PD控制器对太阳帆板展开过程中,航天器的姿态跟踪控制的鲁棒性和有效性。     

Development and qualitative assessment of the GAME/sup Cycle/ exercise system

Increased physical activity is important for reducing the risk of cardiovascular disease. However, among people with disabilities, inactivity is prevalent. In order to encourage exercise among members of this group, an exercise system combining arm ergometry with video gaming, called the GAME/sup Cycle/ was previously developed. User input was received through an arm crank ergometer on a swivel, with the angular velocity of the ergometer resistance wheel controlling one axis and rotation of ergometer about the swivel controlling the other. The purpose of this study was to detail the algorithms used in this device and present novel features included in a second generation of the GAME/sup Cycle/. The features include a wheel on base, a steering return mechanism, and wireless fire buttons. A focus group of clinicians (n=8), wheelchair users (n=8), and clinician wheelchair users (n=2) was conducted to evaluate the features of the GAME/sup Cycle/. The focus group suggested improvements to the steering mechanism and to reduce vibration in the system. However, the focus group enjoyed the GAME/sup Cycle/ and felt that it would encourage exercise among persons with disabilities.     

Development and qualitative assessment of the GAME(Cycle) exercise system.

Increased physical activity is important for reducing the risk of cardiovascular disease. However, among people with disabilities, inactivity is prevalent. In order to encourage exercise among members of this group, an exercise system combining arm ergometry with video gaming, called the GAME(Cycle) was previously developed. User input was received through an arm crank ergometer on a swivel, with the angular velocity of the ergometer resistance wheel controlling one axis and rotation of ergometer about the swivel controlling the other. The purpose of this study was to detail the algorithms used in this device and present novel features included in a second generation of the GAME(Cycle). The features include a wheel on base, a steering return mechanism, and wireless fire buttons. A focus group of clinicians (n = 8), wheelchair users (n = 8), and clinician wheelchair users (n = 2) was conducted to evaluate the features of the GAME(Cycle). The focus group suggested improvements to the steering mechanism and to reduce vibration in the system. However, the focus group enjoyed the GAME(Cycle) and felt that it would encourage exercise among persons with disabilities.     

High-accuracy magnetic position encoder concept

Position sensors based on the detection of magnetic flux densities by Hall sensors or magnetoresistors are used in automotive applications for crankshaft and camshaft position sensing, which are needed for engine control. This paper identifies the limitations of traditional designs, which introduce an angular error between the position signal pulse and the actual location of the corresponding triggering feature on the sensor target wheel. It proposes a solution ensuring that the position signal pulse coincides with a point of symmetry in the triggering target wheel feature, thus eliminating the angular error. Two interesting implementations are described in this paper. One of them is analyzed in full detail, and a methodology for its design is provided. In particular, specific design rules are derived which link some of the design parameters to relevant dimensional specifications. These rules are established on the basis of a geometrical method developed for this particular type of problem which necessitates the calculation of flux densities in a few specific locations, namely, where the sensing elements are located. The overall approach, including these design rules, is validated by finite-element analysis, as well as by experimental data     

一种压电式球形加速度计的设计与分析

研究一种压电式球形加速度计,基于压电原理将作用在压力传感器上的压力信号转化成电信号,通过数据采集模块采集三维轴线上6个压力传感器的受力数据,然后计算出球体所受的合力,并根据牛顿第二定律解算出球体加速度.给出了球形加速度计的设计原理,建立了球形加速度计在三维空间上的数学模型,分析了球形加速度计的误差模型,并提出了一种基于Kalman滤波的动态数据处理方法.实际测量结果表明,球形加速度计的设计过程简单可行,动态数据处理方法能够有效剔除测量中的野值点.     

电磁场对高速运动电荷的作用力-洛伦兹力公式的新形式

百年以前,由洛伦兹建立的电磁场对电荷的作用力公式－－洛伦和公式,是在低速情况下得到的,后来被推广到了任意运动速度,本文根据一般电磁场理论信了运动电荷的电磁场特性,认为该公式只适用于低速情况,对高速运动电荷不再适用。并在此基础上导出了适用于任意速度的新的洛伦兹力公式,它在低速情况下转化为通常的洛伦兹力公式。     

用流速对数律研究附壁射流区的壁面阻力

依据Myers和前人对附壁射流区流速分布的实测资料以及附壁射流区边界层发展的经验公式,研究了附壁射流区的壁面局部阻力系数、阻力系数、平均壁面阻力系数和壁面阻力的变化规律,提出了附壁射流区流速分布的对数律公式,给出了壁面局部阻力系数C_f'与U_mδ/v的关系,C_f'和壁面阻力系数C_f与跃前断面雷诺数Re_1和相对距离x/h_1的关系,给出了壁面阻力和平均壁面阻力系数的计算方法。通过与Myers的试验资料进行对比,表明了本文给出的公式适用范围大、计算方法简单、精度高。     

The unification of the Lorentz and Coulomb gauges ofelectromagnetic theory

The Lorentz and Coulomb gauges of electromagnetic field theory are shown to be special cases of the same gauge, denoted in this paper as the velocity gauge since it specifies the divergence of the vector potential in terms of the velocity of propagation of the scalar potential. This velocity is the speed of light for the Lorentz gauge and infinite for the Coulomb gauge. With the velocity gauge, the selection of a gauge can be explained in physical terms-the specification of the velocity of propagation of the scalar potential-which engineering students might find more intuitive than a suspiciously arbitrary choice made for mathematical convenience     

基于ARM的角位移测量系统研制

为了实现角位移的高精度测量,研制了一种基于ARM的角位移测量系统.该系统以ARM9处理器S3C2410为核心,一方面控制旋转编码器采集角位移信号;另一方面通过USB接口与计算机通信,实现命令与数据的传输.在上位机利用C#编写应用程序,绘制并显示角位移、角速度和角加速度曲线.通过实验证明,该系统能快速准确对旋转体运行状况...     

淹没植被浅水明渠流的非对数流速分布规律

随着对生态环境的日益重视,有关植被的水力学研究近年来进展迅速.对于淹没植被,现有的研究一般认为植被表层水流仍满足对数分布.但在浅水情况下,表层水流流速明显偏离对数规律.本文首先通过改变表层水深、植被杆径和密度,开展了淹没植被浅水明渠流多工况水槽实验,并运用激光多普勒测速仪对垂线流速分布进行了测量;然后结合Prandtl...     

The Interpretation of Train Rolling Resistance from Fundamental Mechanics

Past efforts in railway improvement have focused on increased train stability and ride quality for safe and smooth operations at higher speed. The question of energy consumption has rarely been considered. In view of projections of higher fuel costs and increased rail traffic volume, energy effects caused by improved train resistance should be considered. First-order expressions for the rolling resistance of freight trains on level tangent track were derived from the basic principles of physics and engineering. The average power dissipated by the suspension system was obtained from a linear model of the track train system. Hysteresis in the soil is computed using basic principles of soil mechanics. Losses due to wheel rolling friction, imposed wheel sliding, and bearings were estimated from simple engineering and considerations. Rolling resistance as would be measured in coast down or drawbar pull tests on level tangent track is found to depend strongly on the quality of the track as well as weight and speed. On good track, most of the rolling resistance is due to bearing resistance, while on poor track, suspension losses predominate. Empirical expressions such as the Davis formula, which have been used in the past by the railroad industry, are unable to describe train rolling resistance adequately because of the way in which they are parameterized. Some of the parameter values obtained from fits to experimental data do not carry the physical meaning with which they were traditionally associated.     

薄壁装配单元并联结构设计及性能分析

薄壁件由于结构复杂刚性差且精度要求高,薄壁件装配主要由人工完成。存在自动化程度低、产品良率低、效率差、严重依赖工人的技术水平的问题。为了提高产品质量和生产效率,急需采用自动化装配设备。薄壁件的装配单元需要根据在线测量数据分类匹配装配,采用传统的工业机器人,占用较大的工作空间,并联机器人结构柔性,占用空间小,本文设计提出一种薄壁件自动化分拣装配单元设计方案,来代替传统人工分拣与装配的生产方式。首先根据薄壁件分类装配功能需求,设计了并联结构,建立了并联结构的动力学模型和运动学模型;分析了并联结构快速运动时速度及加速度的变化规律,3条主动臂和中间支链的角度数据曲线变化平稳,没有发生突变,角速度和角加速度相对平稳,保证了测量相机工作精度,并联机构的稳定性满足设计要求;动平台的位移曲线与预定轨迹重合,结果显示所设计的机构可以满足功能要求。该结构工作空间小,可以实现薄壁件装配的自动化,保证了产品的质量。     

一种无差拍直接转矩控制方法

针对现有的感应电动机无差拍直接转矩控制方法计算比较复杂,且计算得到的两个控制电压与控制对象磁链和转矩不是一一对应的问题,提出了一种在定子磁场定向的同步旋转坐标系下进行无差拍直接转矩控制计算方法.由d轴磁链方程推导出磁链无差拍控制电压的计算式;利用和定子磁链相垂直的q轴电流方程,推导出转矩控制电压计算式.计算出的电压矢量由空间电压矢量脉宽调制方法实现.这种方法计算简单,不需要解二次方程,分离的磁链和转矩控制计算有利于控制安排.对采用这种方法的直接转矩控制系统进行仿真表明,系统转矩控制和磁链控制响应快,对参数的变化不敏感.