基于光谱信息散度与光谱角匹配的高光谱解混算法

针对采用线性逆卷积(LD)算法进行端元初选过程中,端元子集中存在相似端元光谱,影响解混精度的问题,提出了一种基于光谱信息散度(SID)与光谱角匹配(SAM)算法的端元子集优选光谱解混算法。通过在端元进行二次选择时,采用以光谱信息散度和光谱角(SID-SA)混合法准则作为最相似端元选择的判据,去除相似端元,降低相似端元对解混精度的影响。实验结果表明,基于SID与SAM的高光谱解混算法将重构影像的均方根误差(RMSE)降低到0.0104,该方法比传统方法提高了端元的选择精度,减少了丰度估计误差,误差分布更加均匀。     

多方向振动测试的石英挠性加速度计高阶误差系数辨识

高精度的误差系数可准确评价加速度计的精度与性能,从石英挠性加速度计误差模型入手,对其进行多方向振动测试试验,利用总体最小二乘（TLS）算法辨识加速度计模型方程中的高阶误差系数,建立较高精度的加速度计数学误差模型。为验证算法的有效性及所实施试验的可靠性,和传统重力场多点测试辨识加速度计参数方法作对比,同时,提出误差系数和决定系数两个指标来评价振动测试的辨识效果。结果表明：采用多方向振动测试结合总体最小二乘算法方案所辨识出加速度计高阶误系数精度较高,在实践中具有较好的借鉴意义。     

基于VC的远程文件操作的研究与实现

远程文件操作是远程控制系统的重要内容。它是指控制端利用信道向受控端发出文件操作指令,以达到控制受控端文件的目的。该操作关键在于受控端突破防火墙与控制端连接,文章主要探讨了远程文件操作的工作原理及具体实现。     

基于非线性动力学的水电机组操作油管振动故障研究

贯流式机组操作油管与受油器浮动瓦碰摩现象会引起操作油管的异常振动，导致漏油、窜油现象，为更好地保证水电机组的安全运行，在考虑水电机组运行过程中常见频发性故障的情况下，建立包含定转子电磁激励影响和操作油管不对中故障的操作油管-转子振动碰摩的动力学模型及微分方程，采用数值积分法对操作油管径向振动随油管不对中量、励磁电流大小和定子刚度系数等参数变化的非线性动力学特征进行分析，使用时域波形图、频谱、轴心轨迹图、庞加莱截面图和分岔图等多种手段表征系统耦合故障下的动力学响应，发现碰撞摩擦、不平衡磁拉力等因素对机组振动的影响较大，相关研究可为工程实际中多故障源激励耦合造成机组异常运行、停机等现象提供耦合故障类型诊断思路。     

光栅数显装置的非线性补偿方法研究

以提高光栅测量系统的精度为目的,提出一种基于光栅数显装置的非线性补偿方法。采用实时误差分离技术来对光栅测量误差进行修正的,通过采样点建立误差修正的数学模型,根据数学模型实现对任意测量值的误差修正。实验结果表明,该方法可有效解决由光栅本身的制造误差、光电转换部分误差及外界环境的振动、温度变化等因素带来影响光栅测量系统精度的问题,从而可大幅度地提高光栅测量系统的精度,而且这种补偿方法不但算法简单方便且经济成本较低,完全能够满足大部分光栅测量系统对于测量精度的要求。     

陀螺寻北仪基座扰动的一种补偿方法

为了减小基座扰动对寻北精度的影响,首先分析了基座扰动引起的寻北误差,推导了基座扰动与寻北误差之间的关系表达式,并提出通过增加隔振基座和选择采样时间来减小基座扰动引起寻北误差的方法,通过卡车振动试验,证明该方法可以较好地减小基座扰动对寻北精度的影响.     

基于VC的远程文件操作的研究与实现

远程文件操作是远程控制系统的重要内容。它是指控制端利用信道向受控端发出文件操作指令，以达到控制受控端文件的目的。该操作关键在于受控端突破防火墙与控制端连接，文章主要探讨了远程文件操作的工作原理及具体实现。     

适用于MEMS振动陀螺仪的相位读出自校准方法

相比于传统陀螺仪,MEMS振动陀螺仪具有体积小、质量轻、功耗低、价格低廉等优势,但是由于其本身结构的局限性和工艺加工水平的限制,其在性能上还处于低精度陀螺仪的行列。目前已有若干MEMS自校准方案可以应用于MEMS振动陀螺仪以提高其精度指标,然而已有的技术存在着只能消除某一种因素对精度的影响、需要高精度转台系统支撑或者校准的灵敏度不高等不足。为解决上述问题,设计并提出了一种基于相位读出的MEMS振动陀螺仪自校准方案,该方案能消除工艺误差、器件老化、外部环境变化对陀螺仪精度的影响,而且该方案不需要高精度转台系统支撑、能够消除绝大部分因素对精度的影响、校准的灵敏度更高。实验仿真结果表明,该方案能实现MEMS振动陀螺仪的自校准,提高测量精度,扩大MEMS振动陀螺仪的适用范围。     

基于小波多尺度分析的光纤陀螺振动误差分析与建模

针对振动环境对光纤陀螺性能的影响,对某型号的光纤陀螺进行了线振动实验并对实验结果进行了Allan方差分析。利用小波多尺度变换提取了光纤陀螺误差模型中的各误差项,分析并验证了零漂及噪声误差与Allan方差分析误差系数中的量化噪声、角度随机游走以及零偏误差与误差系数中的零偏稳定性、速率随机游走、速率斜坡之间的对应关系。随后利用RBF神经网络对小波多尺度分析提取的零偏误差建立模型并进行了补偿。仿真结果表明,本文提出的方法有效减小了振动环境下各误差项对光纤陀螺性能的影响, Allan方差分析结果中的五个误差系数均有较大下降,其中两项误差系数下降了一个数量级及以上,极大提高了光纤陀螺在振动环境下的输出精度,对光纤陀螺在振动环境下的误差研究具有重要指导意义。     

基于小波多尺度变换的光纤陀螺振动误差分析与补偿

针对振动环境对光纤陀螺性能的影响,对某型号的光纤陀螺进行了线振动实验并对实验结果进行了Allan方差分析。利用小波多尺度变换提取了光纤陀螺误差模型中的各误差项,分析并验证了零漂及噪声误差与Allan方差分析误差系数中的量化噪声、角度随机游走以及零偏误差与误差系数中的零偏稳定性、速率随机游走、速率斜坡之间的对应关系。随后利用RBF神经网络对小波多尺度分析提取的零偏误差建立模型并进行了补偿。仿真结果表明,本文提出的方法有效减小了振动环境下各误差项对光纤陀螺性能的影响,Allan方差分析结果中的五个误差系数均有较大下降,其中两项误差系数下降了一个数量级及以上,极大提高了光纤陀螺在振动环境下的输出精度,对光纤陀螺在振动环境下的误差研究具有重要指导意义。     

Command shaping control for micro-milling operations

Micro milling requires both high speed and high accuracy in order to economically produce parts with features on the scale of 1 μm. Micro mills are smaller and more flexible than traditional large-scale machines. Therefore, vibration of the machine structure is a significant problem. Given that micro milling requires high positioning precision, even small vibrations in the controller dynamics are problematic. The small-scale operation has considerably lower tool/workpiece interaction forces than traditional-scale milling. These low cutting forces have minimal effect on the machine structural response. Therefore, the dominant dynamic factor in exciting vibration can be the machine tool motion, rather than the workpiece/tool interaction. Given this realization, properly shaping the motions of the micro mill is a promising approach to reduce vibration. This paper presents a nonlinear command-shaping technique to reduce the vibrations of a micro mill that can be implemented with a standard CNC controller. The robustness of this technique to modeling errors and disturbances is investigated. Theoretical proofs and experimental demonstrations of the command-shaping technique are presented. The improved performance from the command shaping enables higher throughput and improved accuracy of the micro mill.     

基于ANSYS的机床模态分析

振动现象是机床设计中所面临的问题之一,它能造成加工误差,影响零件的加工精度。模态分析主要用于确定结构或机器部件的振动特性。本文建立了某型立铣床床身的三维有限元模型,并利用大型有限元分析软件ANSYS进行了模态分析,得出了床身前十阶固有频率和振型。     

Post-effects of long-term hand vibration on visuo-manual performance in a tracking task

Movement precision and performance time were evaluated through a visuo-manual tracking task performed before and after 10-min hand vibration exposure. Constant displacement amplitude vibration of 0.2 and 0.3 mm peak to peak at 90, 150, 300 Hz were applied to the hand z-axis by a vertical handle. During exposure a grip force of 5% MVC was exerted for 5 s and then relaxed for 25 s while maintaining fingers-handle contact. The tracking task consisted in moving a ring (phi = 9 mm) attached to a thin rod held between the index finger and thumb along a zig-zagged wire (phi = 3.7 mm). Alterations of tracking errors (ring-wire contact) and tracking time were analysed as a function of the vibration parameters. The tasks were performed by ten healthy participants. Vibration induced a significant increase in tracking errors (ring-wire contact) and a significant decrease in tracking time. These impairments decayed with time after vibration exposure. The recovery period was > 5 min but < 10 min with the exception of 90 Hz vibration, for which recovery could be > 10 min. The number of tracking errors was neither influenced by vibration frequency nor by amplitude. The tracking time decreased as frequency increased and recovery was related to the displacement amplitude. The subjective rating of the performance on a visual analogue scale indicated that the subjects tended to perceive the task as being easier after vibration exposure. Vibration applied to the non-dominant hand while the participant performed the tracking task had no effect. These results show that vibration similar to hand-tool vibration affects precision and velocity control of visually guided hand movements. Furthermore, these performance decrements were not consciously perceived.     

Bandgap analysis of a tunable elastic-metamaterial-based vibration absorber with electromagnetic stiffness

Vibration is a mechanical phenomenon and exists throughout society. The vibrations in daily life would cause emotional discomfort as well as physical fatigue. Vibration even can give a life threat depending on its magnitude. Vibration is one of the significantly important factors to consider for the safety of the overall society, and therefore study of vibration reduction is indispensable. This paper presents a novel tunable electromagnetic vibration absorber based on an elastic metamaterial. The electromagnetic vibration absorber is a lattice structure dynamic model comprising elastic metamaterial unit cells having negative refractive index property and interconnected by springs. To verify the tunability of the elastic-metamaterial-based vibration absorber, the electromagnetic stiffness change in a finite element (FE) model of the electromagnet was analyzed through a parametric study of the air gap size, internal composition of the electromagnet, and amount of current. The conditions under which the electromagnet generates the highest electromagnetic stiffness were also explored. Each different value of electromagnetic stiffness obtained from the parametric studies was used for FE analysis of the dynamic model to investigate the influence on bandgap variations. The results reveal that the variation of electromagnetic stiffness has an effect on the location and bandwidth of bandgap. Moreover, vibration reduction was achieved due to the structural aspects of the dynamic model and the negative refractive index property of the elastic metamaterial. It is demonstrated that the elastic metamaterial vibration absorber is tunable in real time with the change of electromagnetic stiffness and has vibration reduction effect in various frequency ranges.

     

ACTIVE VIBRATION ISOLATION FOR A LONG RANGE SCANNING TUNNELING MICROSCOPE

Vibration isolation or control is critical for the optimum operation of the Molecular Measuring Machine (M³), a high‐resolution, length‐metrology instrument at the National Institute of Standards and Technology. This paper describes the extension of the M3 Mallock isolation suspension from passive to six degrees‐of‐freedom (DOF) active vibration isolation. System modeling is presented, and experimental system identification is carried out for the purpose of model verification. The paper then compares the vibration isolation performance achieved using a classical proportional‐integral‐derivative (PID) controller versus that achieved using a modified, model‐based, Linear‐Quadratic‐Gaussian (LQG) controller. Attenuation of 3 dB to 15 dB is achieved within the active vibration isolation control bandwidth, and images taken with the M³ scanning tunneling microscope (STM) probe show improved performance.     

柔性机械臂的双时间尺度组合控制

本文研究柔性机械臂的轨迹跟踪和振动抑制问题. 首先, 利用Lagrange法和假设模态法建立柔性机械臂的动态模型, 进而利用奇异摄动理论得到柔性机械臂的双时间尺度模型. 然后, 基于慢时间尺度模型利用滑模控制理论设计轨迹跟踪控制器; 借助于快时间尺度模型利用自适应动态规划设计参数不精确已知情况下的最优振动抑制控制器; 将二者相结合, 构造双时间尺度组合控制器, 利用奇异摄动理论证明闭环系统稳定. 最后, 在Matlab/Simulink环境下进行实验, 与现有方法相比, 本文设计的控制器对柔性振动具有更好的振动抑制效果, 跟踪精度更高.     

无陀螺大挠性多体卫星的自抗扰姿态控制

研究了最近提出的非线性自抗扰控制器在大挠性多体卫星姿态控制中的应用问题。在无陀螺测量情况下 ,提出了一种自抗扰姿态控制器 ,并与使用于某挠性卫星的有陀螺测量的古典PID姿态控制器 ,从鲁棒性、干扰抑制、动静态性能指标和振动抑制等方面进行了比较。在考虑了反作用轮和敏感器的实际非线性和敏感器噪声影响情况下 ,仿真表明 :自抗扰姿态控制器 ,除在振动抑制和控制误差精度方面略差外 ,其它各方面均优于古典PID姿态控制器。该文提出的自抗扰姿态控制器 ,在无陀螺或陀螺故障下 ,实现挠性多体卫星的高精度高稳定度姿态控制 ,具有实际的应用价值     

Model Predictive Control of a Flexible Links Mechanism

Vibration suppression in flexible link manipulator is a recurring problem in most robotic applications. Solving this problem would allow to increase many times both the operative speed and the accuracy of manipulators. In this paper an innovative controller for flexible-links mechanism based on MPC (Model Predictive Control) with constraints is proposed. So far this kind of controller has been employed almost exclusively for controlling slow processes, like chemical plants, but the authors’ aim is to show that this approach can be successfully adapted to plants whose dynamical behavior is both nonlinear and fast changing. The effectiveness of this control system will be compared to the performance obtained with a classical industrial control. The reference mechanism chosen to evaluate the effectiveness of this control strategy is a four-link closed loop planar mechanism laying on the horizontal plane driven by a torque-controlled electric actuator.     

基于参数自学习的无人车越野环境跟踪控制方法

针对无人车在越野环境下难以高速、高精度地跟踪复杂路况的问题,设计了一种参数自学习的前馈补偿控制器,与模型预测控制方法构成前馈-反馈的控制结构。在该控制结构中,前馈控制根据实时状态的跟踪误差在线更新学习系数,有效考虑车辆高速运动过程中无法精确建模的非线性动力学特性以及复杂路况不断变化的曲率和路面条件等的影响,在保证稳定性的同时快速减小跟踪误差。在越野场景进行了高速的S型与直角弯路径跟踪实车实验来验证参数自学习控制器的有效性,结果表明,所设计的参数自学习控制器相比传统的模型预测控制器跟踪误差和横摆都较小,在跟踪精度和车辆稳定性上都有较大改善。     

轴向运动弦线横向振动控制的Lyapunov方法

研究轴向运动弦线和作动器组成的耦合系统的横向振动控制．此系统被作动器分成未控和受控两部分,通过作用在作动器上的控制力对受控部分进行主动控制．分析未控弦线的横向振动的有界性．采用Lyapunov方法获得控制规律,并证实受控弦线横向振动的指数稳定性．在初始扰动和激励力作用下,通过数值仿真证实控制规律的有效性．