基于虚拟样机技术的四足机器人静态稳定步态规划

针对现有技术文献中广泛使用的多种静态稳定步态中速度稳定性与稳定裕度不可兼得的通病,在随动质心的静态步态基础上,利用参数化坐标变换矩阵方法规划出一种四足机器人前进过程中质心以曲线轨迹移动的静态步态方法,使该步态方法以连续性速度运动的过程中保证一定稳定裕度。通过D-H法求得四足机器人的逆运动学坐标变换矩阵,分别在三维空间中对四足机器人的四组足端轨迹方程进行规划,并带入MATLAB软件后以逆运动学方程计算出关节夹角驱动方程,利用步态规划图求出机器人四条腿各自对应的夹角驱动方程以及机体质心轨迹方程。最后在MSC.ADAMS软件中建立四足机器人虚拟样机并对规划的步态进行虚拟仿真,仿真结果验证了该步态对提升四足机器人对于速度连续性以及稳定裕度的提升。     

基于倒立摆模型的四足机器人对角步态规划

为提高点着地四足机器人在匀速对角小跑过程中的动态稳定性,将对角小跑过程简化为一个倒立摆模型。针对四足机器人对角小跑过程中由于重心无法始终处于支撑对角线上所引起的翻转,在此模型中转换为由于重心引起的摆动角误差。采用虚位移原理对机器人摆动角的变化进行分析,确定不同重心运动变化对摆动角误差的影响并找到合适的重心起始位置,理论上能够使摆动角的误差为零。动态仿真实验验证了所提出的对角步态规划能够使四足机器人实现稳定的对角小跑的有效性。     

一种新的双足机器人模型设计与相关研究

针对双足机器人最简模型在行走过程中出现摆动腿足部擦地的问题,提出了一种通过摆动腿膝关节弯曲达到摆动腿缩短的新模型。当摆动腿开始摆动时,摆动腿膝关节弯曲锁定,摆动腿缩短;当摆动腿摆动到最大位置时,膝关节解锁,摆动腿伸直再锁定,此后摆动腿回摆,系统变为直腿模型。采用脚后跟冲击控制,在摆动腿落地前,拖后的支撑腿与地面接触处施加一指向髋关节的瞬时冲击力,冲击力可以减小摆动腿着地时能量的损耗,同时驱动被动机器人向前行走。设计了迭代学习控制算法,找到极限环与不动点,实现不同给定期望步长跟踪的冲击力的计算。仿真结果表明,迭代学习控制可以有效的实现不同期望步长的跟踪,可以很快的找到机器人系统的不动点,通过收敛的相平面,得到稳定的极限环,保证了机器人行走过程稳定。     

基于梯度下降和二分法的移动机器人轨迹规划方法

轨迹规划是移动焊接机器人轨迹控制的基础,是该系统中重要的组成部分。为了提高多关节移动焊接机器人轨迹规划的效率和精确性,同时考虑到多关节焊接机器人的运动特性提出了一种梯度下降法和二分法结合的轨迹规划方法。移动焊接机器人由机械杆和机器人移动平台组成,由于移动平台提供移动性使得移动焊接机器人相对固定的机械臂有更大的工作空间。近年来,此类系统的研究已在经学术界和工业界迅猛发展。论文首先建立移动焊接机器人的运动学模型,并且阐述梯度下降法和二分法结合算法的设计步骤。然后,采用典型的正弦波形作为焊缝轨迹,通过仿真验证该方法的应用前景和可行性。     

液压四足机器人的实时分散解耦控制

针对液压驱动四足机器人单腿协调性难以保证的问题,开发了一种实时分散解耦控制系统：基于PC-Based控制系统架构,在RTX环境下模块化了实时控制子任务,并对多任务的处理进行了实时调度,搭建出了机器人的实时分散控制系统框架;针对单腿系统设计了基于PID神经元网络的广义解耦控制算法,并将其嵌入到整体程序框架中,实现了多腿联动的分散解耦控制。物理样机实验表明开发的控制系统能够满足分散解耦控制算法的实时性要求,提高了四足机器人运动的协调性,进而保证其连续稳定地行走,具有一定的独创性与实用价值。     

液压驱动型四足机器人电液伺服控制系统仿真建模与实验分析

复杂的作业环境和艰巨的作业任务使液压驱动型四足机器人对其伺服系统的精度、速度和力量均比一般机器人在普通情况下有更高的要求。为掌握液压驱动型四足机器人在多种路况下行走时各液压缸的受力情况以及液压系统内流量、压力的变化情况,需要对其虚拟样机进行机械动力系统和液压伺服系统的联合仿真,定性分析电液伺服系统位置、速度等被控对象的特性,并分析PID控制器在四足机器人伺服控制方面的特性与不足。针对传统控制算法在四足机器人控制存在的短板问题,设计了一种非对称前馈补偿模糊自适应PID算法,并利用物理样机进行了实际验证。实验结果为四足机器人电液伺服控制系统硬件、软件和控制算法的设计与优化指明了方向,还为研究四足机器人平稳步态控制策略提供了决策依据和数据支持。     

下肢负重外骨骼机器人的初步设计

研究设计了一种能够增强人体负重的下肢外骨骼机器人,该负重外骨骼机器人具有8个自由度,可实现髋关节的外展与内收、屈/伸运动;膝关节的屈/伸运动以及踝关节的弯曲运动。根据人体步态分析研究出各个关节的运动角度范围,结合目标负重进行结构优化设计。对机器人的结构进行简化,建立了外骨骼机器人的连杆模型,根据其几何关系,采用D-H准则对外骨骼机器人进行了数学建模。以计算机、六轴运动控制卡和STM32为核心构建了控制系统,结合ZMP(Zero Moment Point)零力矩点稳定性判据及三次样条插值进行了步态规划,并将此步态规划应用于样机上。样机实验结果表明,此结构能够满足不同体型的人进行穿戴,并能够根据规划的步态轻松行走,验证了其结构和控制系统的合理性。     

双足机器人下楼梯动作的设计与生成

上下楼梯是人们典型,常见的动作,研究其动作生成算法是实现稳定步态的重要保证;以双足机器人为研究对象,以下楼梯动作为例,基于重复变换的上体重心移动法提出双足机器人下楼梯动作的设计方法;通过仿真生成了3种典型模式的下楼梯动作过程,评价了下楼梯过程中各关节的角度变化,力矩变化和稳定性,讨论了楼梯参数变化对机器人各关节负担的影响;仿真结果表明,通过改变下楼梯的方式,可以减轻下楼梯对腿部损伤关节的负担,提高安全性,实现稳定的下楼梯动作;为福祉,康复医疗教育提供依据。     

光子晶体传输特性的时域精细积分法分析

将精细积分法应用于时域有限差分法中,提出了一种求解光子晶体传输特性的时域精细积分法,并对其计算精度及稳定性进行了分析.从一阶麦克斯韦方程出发,在空间上采用Yee元胞进行差分离散,结合吸收边界条件及激励源表达式将方程整理为标准的一阶常微分方程组形式.通过时间步长的精细划分和指数矩阵的加法定理,在时间上利用精细积分法对齐次微分方程进行积分求解,并结合激励向量的特解得到空间离散的场分量,最终通过傅里叶变换求得方程的解.利用时域精细积分法对光子晶体进行了实例计算,并将其结果分别与时域有限差分法和四阶龙格库塔法在精度、稳定性等方面进行了比较,结果表明时域精细积分法具有更高的计算精度,并且克服了时域有限差分法以及四阶龙格库塔法在计算稳定性上对时间步长的限制.提出的方法具有精确、稳定的特点,为光子晶体传输特性的研究提供了一种新的有效的分析方法.     

上行与下行人腿膝部受力问题分析

腿部运动是人体活动的最基本方式,人腿的上行与下行是人体活动的核心组成要件。本文理清了腿关节受力与基本腿部运动的关联因素,围绕人腿上下行运动建立简化模型,推导出实际过程腿部的运动状态与受力间的稳定态方程,从而以明确的数据说明腿部上下行活动中的受力量化问题。同时,结合膝部损伤问题,文中提出了缓解腿部损伤的方法;通过本文所建构的下肢运动模型,有助于推动人们对下肢健康运动方式的理解和认识,并引发同类问题的迁移性思考,所讨论模型可在步行式机器人的入门认识方面引发有价值的讨论。     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Femtosecond Transform-Limited Pulse Generation by Compensating for the Linear Chirp of SPM Spectra in Dispersion Shifted Fibers

A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.     

Hybrid Wavelength and Code Division Multiple Access in Optical Networks

A review of schemes for multiple access in fiber optic networks shows that a hybrid of wavelength and code division multiple access (WCDMA) combines the best features of both. In particular, the hybrid scheme retains the large information carrying capacity of wavelength division multiple access (WDMA) and flexibility of code division multiple access (CDMA). In this paper WDMA, optical CDMA (OCDMA), and WCDMA networks are discussed. In OCDMA networks, concept of incoherent and coherent coding including inverse decoding and matched filter is introduced. The delay performance of both WDMA and WCDMA networks, under the simple suboptimum access protocols based on cyclic search, is computed. It has been shown quantitatively that tuning delay significantly affects the delay performance of both WDMA and WCDMA networks. Futhermore, delay performance of WCDMA networks is always better than the WDMA networks for the same tuning delay, load, and number of users.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Sorting of bending magnets for the SSRF booster

The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.     

Measurement of nonlinear coefficient of optical fiber based on small chirped soliton transmission

We measure the waveform and phase curves of short optical pulses before and after transmission over different lengths of fibers by use of the pulse analyzer with the frequency-resolved optical gating (FROG),and numerically simulate pulse evolution under the experimental conditions.The nonlinear coefficient of the fiber is given by comparing the experimental results with the numerical ones.Difference between the experiment and numerical simulation is analyzed.     

Resonance scattering of canonical elastic shells in absorbing fluid medium

Resonance scattering of elastic spherical shell and cylindrical shell while the surrounding fluid medium has absorption is studied. The normal mode solution derived using exact elastic theory and the separation of variables is still applicable. However, the scattering form function has to be modified for the absorbing medium, otherwise the unreasonable result would be obtained. The backscattering form function in the absorbing medium is redefined, and the form function of elastic spherical and cylindrical shell with vacuum or solid matter filled is calculated in various absorption conditions. The results show that the absorption of surrounding fluid leads to notable attenuation of the coincidence resonances in the mid-frequency, but it has a little influence on the low-frequency resonance scattering induced by the filler inside the shell.     

Single-beam self-referenced phase-sensitive surface plasmon resonance sensor with high detection resolution

A versatile and low-cost single-beam self-referenced phase-sensitive surface plasmon resonance(SPR)sensing system with ultra-high resolution performance is presented.The system exhibits a root-mean-square phase fluctuation of ±0.0028.over a period of 45 min.i.e.a resolution of±5.2×10-9 refractive index units.The enhanced performance has been achieved through the incorporation of three design elements:a true single-beam configuration enabling complete self-referencing so that only the phase change associated with SPR gets detected,a differential measurement scheme to eliminate spurious signals not related to the sensor response,and the elimination of retardation drifts by incorporating temperature stabilization in the liquid crystal phase modulato .Our design should bring the detection sensitivity of non-labeling SPR biosensing closer to that achievable by conventional fluorescence-based techniques.     

Influences of SiO2 protective layers and annealing on the laser-induced damage threshold of Ta2O5 films

Ta2O5 films are prepared on BK7 substrates with conventional electron beam evaporation deposition.The effects of SiO2 protective layers and annealing on the laser-induced damage threshold (LIDT) of the films are investigated.The results show that SiO2 protective layers exert little influence on the electric field intensity(EFI)distribution,microstructure and microdefect density but increase the absorption slightly.Annealing iS effective on decreasing the microdefect density and the absorption of the films.Both SiO2 protective layers and annealing are beneficial to the damage resistance of the films and the latter is more effective to improve the LIDT.Moreover,the maximal LIDT of Ta2O5 films is achieved by the combination of SiO2 protective layers and annealing.