基于并联机构的六维加速度传感器的方案设计及建模研究

提出一种新的基于并联机构的压电式六维加速度传感器的设计方案,即用并联机构充当传感器的弹性体结构,压电陶瓷同时充当传感器的敏感元件和并联机构的移动副,弹性球铰链代替传统的球面副.分别在质量块、外壳及地面上固结坐标系,基于多体系统理论推导两两之间位姿关系的解析表达式.运用牛顿-欧拉法建立系统的动力学方程,通过引入辅助角速度并用四元数来描述旋转矩阵和角速度矢量,将其转化成两个一阶常微分方程组的初值问题,并运用改进的欧拉算法进行求解,实现了六维加速度的完全解耦.针对四元数的违约问题,运用矩阵广义逆理论提出了一种有效的可重复运行的修正算法.利用建立的解耦模型及其算法对实例进行了求解,数据处理总时间小于采样点时间跨度,且理论计算值与ADAMS仿真数据吻合得很好;另外,通过试验进一步验证了设计方案的合理性以及数学模型的可靠性.     

充气膜结构零应力态求解

充气膜结构分析全过程包括9个状态和7个分析过程,零应力态是结构分析与设计的基础,将结构数值分析态和实际物理态有机联系起来。该文首次提出了一种从弹性平衡态到零应力态的逆解析数值分析方法,非线性协调矩阵广义逆法。首先,用膜线单元模拟膜面,将膜结构转化成为网格结构,由弹性平衡态预张力和材料参数,计算膜线无应力长度和伸长量;然后,基于杆系结构平衡矩阵理论和小变形假定,建立体系的协调方程,由协调矩阵M-P广义逆求解节点位移,逆向叠加求出新状态位形。根据新位形计算膜线张力向量和节点不平衡力向量,迭代求解零应力态。根据该算法,用MATLAB编制了计算程序。算例分析验证了该方法的正确性和高效性。该文对充气膜结构设计具有重要理论意义和实际指导价值。     

三维力传感器静态解耦算法的研究与应用

介绍了三维腕力传感器维间耦合基本原理,并建立了耦合误差模型,阐述了传感器静态标定的基本方法。对传统的基于求解矩阵广义逆的静态解耦算法中容易产生病态矩阵,进而影响解耦稳定性和精度的问题进行了研究。提出了基于耦合误差建模的静态解耦算法。对十字梁型三维腕力传感器进行静态标定试验,使用2种解耦算法对标定数据进行分析。试验结果表明,基于耦合误差建模的静态解耦算法具有高可靠性和高解耦精度,且能够反应各维力之间的耦合关系。     

Stewart式六维力传感器轻量化设计

空间复合力测量是空间感知技术的重要发展方向之一。六维力传感器作为主要的空间复合力测量装置,被广泛应用于火箭发动机推力测试、航天器对接等领域。目前,轻量化已成为六维力传感器的主要研究方向之一,但由于其设计指标多且各项指标间存在相互制约,故采用理论推导、数值仿真及实验验证相结合的方法进行研究。首先,利用螺旋理论建立Stewart式六维力传感器在理想条件下的力映射模型,通过求解综合性能目标函数来确定其各向同性度理论最优时的结构参数。然后,利用ABAQUS有限元分析软件构建Stewart式六维力传感器仿真模型,并对其初始样机的质量、刚度、强度和灵敏度进行了详细分析;在此基础上,分析了上、下加载盘主要结构参数对传感器质量、刚度和强度的影响,进而对加载盘结构参数进行了优化并设计了一种具有正四面体特征的半球形减重结构,实现了传感器的轻量化设计。最后,对优化后Stewart式六维力传感器的性能进行了仿真分析和实验验证。结果表明,基于多目标参数优化结合数值仿真、实验验证可有效提高设计效率和降低设计成本;所设计的减重结构可有效改善Stewart式六维力传感器的质量分布和提高其质量利用率,优化后传感器的质量减小了17.65%且综合性能优异。研究结果可为六维力传感器的轻量化设计和综合性能优化提供参考。     

基于独立分量分析的六维力传感器标定矩阵的校正

为了提高六维力传感器的测量精度,提出了一种基于独立分量分析(ICA)的静态标定方法。作用在上平台的各维力经过六维力传感器后形成混合信号,该方法先对混合信号进行ICA分解,即将其分离成独立的分量,再结合理想源信号恢复出各维真实作用力的排序和幅值,最后得出校正后的标定矩阵。仿真结果表明,校正后的标定矩阵更接近标准的标定矩阵,从而提高了六维力传感器的测量精度。     

杆梁组合结构的有限元分析

杆梁组合结构能够充分发挥建筑材料的物理性质,是工程中常用的一种结构形式,由于杆和梁单元的自由度不同,给这类组合结构的理论分析带来了困难。该研究针对杆梁组合结构内力分析过程中刚度矩阵的集成问题,基于不同类型结构构件间的连接关系建立了关联表,推导了基于关联表的结构整体刚度矩阵与单元刚度矩阵各元素之间的对应关系,建立了基于关联表的结构整体分析模型。算例分析的结果表明,该文所采用的关联表方法能够有效地处理杆梁组合结构的受力分析问题,此方法对于解决具有不同自由度数的单元的组合结构分析问题提供了简便可靠的思路。     

带肋局部双层网壳的失稳特征研究

应用几何非线性有限元理论,考虑大位移和轴力对刚度的影响,采用广义增量法,建立杆、梁、特殊梁(一端刚接一端铰接)组合适宜局部双层网壳构造特点的数值分析方法。对带肋局部双层网壳的稳定性状进行了深入分析,研究了刚度矩阵特征值、增广平衡矩阵最小奇异值、广义载荷等结构特征参数在第一临界点和后屈曲路径的变化特点,同时分析了结构参数、边界条件、解析模型的影响。根据分析结果,可得到对工程应用有指导意义的结论。     

组合构件双重非线性分析模型研究与应用

以超高层建筑中当前广泛应用的杆系组合构件为研究对象,采用三维空间梁单元对其进行复杂受力状态下的双重非线性分析。为贴近实际工程同时简化计算,首先根据有限元方法和最小势能原理建立单元考虑几何非线性的弹性切线刚度矩阵;然后通过划分截面广义应变将单元截面刚度矩阵分离为弹性刚度矩阵与塑性刚度矩阵,在假定广义应变增量分布状态基础上,基于纤维模型法推导出单元塑性刚度矩阵;最后将考虑几何非线性的弹性刚度矩阵与塑性刚度矩阵集合成整体刚度矩阵,根据构件自身特性选取合理材料本构关系及数值计算方法进行构件非线性受力分析。数值分析结果表明,该文模型与方法概念清晰、计算精度高,还可应用于钢筋混凝土构件的受力性能非线性分析。     

冗余驱动2SPR-2RPU并联机构的运动静力学 及奇异性研究

针对打磨、抛光等重载机器人的应用需求,提出了一种新型冗余驱动2SPR-2RPU并联机构。运用螺旋理论计算了2SPR-2RPU并联机构的自由度,并求解了其运动学逆解与速度雅克比矩阵。全面考虑2SPR-2RPU并联机构自身重力因素,利用拆杆法对该机构进行静力学分析,并建立了其静力学模型。针对机构驱动冗余的特点,运用拉格朗日乘数法,以驱动力最小为目标构造函数,对驱动力进行分配求解,获得2SPR-2RPU并联机构在给定运动轨迹下的驱动力变化趋势。根据速度雅克比矩阵对2SPR-2RPU并联机构的奇异性进行分析,结果表明该机构没有运动学正解奇异和运动学反解奇异,但具有2个运动学混合奇异,且2个混合奇异位形可通过合理设计机构杆件尺寸进行规避。研究结果可为实际工程应用中冗余驱动并联机构的研究提供一定的理论基础。     

重载并联六维力传感器及静态标定

针对传感器重载小尺寸需求,提出一种具有混合分支的重载并联六维力传感器,分析了其结构特点和测量原理。搭建了重载并联六维力传感器标定系统,为改善维间耦合及制造误差等对测量精度产生的影响,从标定算法及模型优化方面对其进行了研究。分别利用最小二乘法和BP神经网络算法对加载实验数据进行了处理,分析结果表明BP神经网络算法要明显优于最小二乘法,并通过数据随机分组测试验证了结果的正确性。基于BP神经网络,提出了一种基于人工鱼群算法的BP神经网络算法,并采用优化后的BP神经网络标定算法对实验数据进行了计算分析,结果表明优化后的BP神经网络计算结果较好且稳定,不易陷入局部极值。     

Superstructured fiber-optic contact force sensor with minimal cosensitivity to temperature and axial strain

In this work a new superstructured, in-fiber Bragg grating (FBG)-based, contact force sensor is presented that is based on birefringent D-shape optical fiber. The sensor superstructure comprises a polyimide sheath, a stress-concentrating feature, and an alignment feature that repeatably orients the sensor with respect to contact forces. A combination of plane elasticity and strain-optic models is used to predict sensor performance in terms of sensitivity to contact force and axial strain. Model predictions are validated through experimental calibration and indicate contact force, axial strain, and temperature sensitivities of 169.6 pm/(N/mm), 0.01 pm/με, and -1.12 pm/°C in terms of spectral separation. The sensor addresses challenges associated with contact force sensors that are based on FBGs in birefringent fiber, FBGs in conventional optical fiber, and tilted FBGs. Relative to other birefringent fiber sensors, the sensor has contact force sensitivity comparable to the highest sensitivity of commercially available birefringent fibers and, unlike other birefringent fiber sensors, is self-aligning with respect to contact forces. Unlike sensors based on Bragg gratings in conventional fiber and tilted Bragg gratings, the sensor has minimal cosensitivity to both axial strain and changes in temperature.     

Development of 6-axis force/moment sensor for a humanoid robot's foot

The development of a 6-axis force/moment sensor considering adult weight for an intelligent foot of humanoid robot is described. To walk on uneven terrain safely, the foot should perceive the applied forces F_X, F_Y and F_Z and moments M_X, M_Y and M_Z to itself and control itself using the forces and moments. The applied forces and moments should be measured from a 6-axis force/moment sensor attached to the foot, which is composed of F_X, F_Y, F_Z, M_X, M_Y and M_Z sensors in a body. Each sensor has different rated loads because the applied forces and moments to foot in walking are different. Therefore one of the important tasks in developing the sensor is to design each sensor with the different rated loads and the same rated output. A 6-axis force/moment sensor for a humanoid robot's foot was developed using parallel plate-beams. The structure of the sensor was newly modelled, and the sensing elements (plate-beams) of the sensor were designed using theoretical analysis. Then, the 6-axis force/moment sensor was fabricated by attaching strain gauges on the sensing elements, and the characteristic test of the developed sensor was carried out. The rated outputs from the theoretical analysis agree well with that from the characteristic test.     

骨折创伤断面微型二维力传感器研制

针对骨折创伤断面轴向压力和径向剪切力的实时精确测量要求,设计了基于E型圆膜片式结构弹性体的微型二维力传感器,建立了传感器弹性体应变的理论分析模型。根据理论分析模型对传感器弹性体的主要结构尺寸进行了优化,设计了弹性体上应变片的贴片位置和组桥方式。对传感器进行了标定实验,获得了标定数据。标定实验结果表明：传感器灵敏度为2.9 MPa/N,轴向力满量程非线性误差为1.1783%,径向力满量程非线性误差为1.0416%。     

Micro-electro-discharge machining as microsensor fabrication technology

This paper presents the design and fabrication of three miniaturized mechanical sensors to demonstrate the three-dimensional machining capabilities of micro-electro-discharge machining (EDM). The first sensor is an inertial bi-axial inclination sensor. The displacement of an inertial mass is measured optically by means of a two-dimensional position sensitive device (PSD). The machining freedom of micro-EDM makes it possible to produce both sensor and housing in one monolithic structure. The second sensor is an inertial uni-axial inclination sensor, which demonstrates the compatibility of the micro-EDM technology with the conventional photolithographic micromachining technologies. The mechanical structure of the sensor is machined by micro-EDM and the capacitive sensing part is produced by lithography. The aim of the integration is to set up a hybrid technology, which inherits the benefits of both micro-EDM and photolithography. The third miniaturized sensor is a three-component force sensor. The mechanical structure of the force sensor converts forces into displacements, which are measured optically. The mechanical structure of the force sensor is produced by wire-EDM and micro-EDM.     

六维力传感器静态标定系统误差分析

介绍了六维力传感器静态标定系统的构成,分析了标定系统的误差来源,建立了综合误差模型,并针对该误差模型提出了减小误差、提高测量精度的措施。分析结果表明,该静态标定系统的MZ通道的满量程误差为2.48%,其余通道均在2%以下。加载力的方向偏差是六维力传感器标定系统误差的主要来源,标定时应该使用高精度的方向校准设备,减小力的加载误差。     

A resonant accelerometer with two-stage microleverage mechanisms fabricated by SOI-MEMS technology

We present the design, fabrication, and testing of a push-pull differential resonant accelerometer with double-ended-tuning-fork (DETF) as the inertial force sensor. The accelerometer is fabricated with the silicon-on-insulator microelectromechanical systems (MEMS) technology that bridges surface micromachining and bulk micromachining by integrating the 50-/spl mu/m-thick high-aspect ratio MEMS structure with the standard circuit foundry process. Two DETF resonators serve as the force sensor measuring the acceleration through a frequency shift caused by the inertial force acting as axial loading. Two-stage microleverage mechanisms with an amplification factor of 80 are designed for force amplification to increase the overall sensitivity to 160 Hz/g, which is confirmed by the experimental value of 158 Hz/g. Trans-resistance amplifiers are designed and integrated on the same chip for output signal amplification and processing. The 50-/spl mu/m thickness of the high-aspect ratio MEMS structure has no effect on the amplification factor of the mechanism but contributes to a greater capacitance force; therefore, the resonator can be actuated by a much lower ac voltage comparing to the 2-/spl mu/m-thick DETF resonators. The testing results agree with the designed sensitivity for static acceleration.     

基于变轴力和定轴力试验对比的钢筋混凝土柱恢复力滞回特性研究

在讨论了框架柱在地震作用下轴力变化规律的基础上,通过由变轴力柱和定轴力柱的低周交变加载试验获得的恢复力滞回曲线对比,给出了用各个“轴力变化半周”的“等效滞回轴力”修正恢复力骨架曲线,和用“等效累积滞回轴力”随时间步长调整累积强度退化系数从而修正恢复力滞回曲线的再加载刚度的建议。该建议能更有效、更方便地反映轴力变化的整个历程对变轴力柱恢复特征的影响,有利于提高钢筋混凝土杆系结构非弹性地震反应分析的有效性。     

Stochastic surface effects in nanobeam sensors

This work analyzes the statistical properties of nanobeam deflections due to stochastic surface stresses, induced by the surface adsorption/desorption of surrounding particles. A mechanical model for a heterogeneous nanobeam is first introduced. The model considers combined axial forces and bending moments due to non-uniform surface effects. Then, local surface interactions are statistically derived from the Langmuir interaction model and their corresponding stochastic surface stresses are introduced. Two types of nanobeam sensor are studied: a cantilever beam with pure surface bending effect and a clamped beam with mixed surface force and bending moment effects. The advantages of each type are discussed. The deflection statistics are found analytically and validated by Monte Carlo simulations. An analytical relation between the adsorption/desorption rates and the maximum deflection variance is found.