Performance of gain-tuned harmonic drive torque sensor under loadand speed conditions

Addresses the topic of torque sensing by using strain gauges, which are cemented directly onto the flexspline of a harmonic drive gear reducer. Conventionally, two or four strain gauges are used to reduce the ripple signal, which is generated by the gear operation. However, our analysis shows that an odd number of strain gauges is more suitable for the ripple compensation. The method does not need online calculations and reduces the needed accuracy of the strain gauges positioning, so it can be practically implemented. Two techniques to define the gains are presented in the paper. One is based on a mathematical model of the fluctuation signal, and the other employs a heuristic approach. Practical results show effectiveness and usefulness of the proposed method. We present the new method and evaluate its performance under load torque and rotational speed conditions. No significant deterioration of the performance under load torque and at various rotational speeds was confirmed     

Optically—powered Optical Fiber Pressure Sensor of Diffused Silicon

In this paper an optically-powered optical fiber sensor for pressure mea-surement is introduced.Differential strain gauges of diffused silicon are emploped as sensing elements and a micro-consumption circuit is used in the probe.Pulse width modulation and pulse position modulation are adopted for signal processing.     

温度补偿型光纤光栅加速度传感探头结构设计

采用可调光纤F-P滤波器技术设计了一种光纤光栅加速度传感系统。提出了一种温度补偿型光纤光栅加速度传感探头,探头弹性系统主要有惯性质量块、双弹簧片、钢管等组成。探头采用不受力光纤光栅法进行了温度补偿。该探头具有结构简单,不受电磁干扰,不受光路功率波动和相位噪声影响等优点,且能自动进行温度补偿。     

基于FBG的飞机起落架载荷测试技术研究

针对某型飞机起落架三向载荷的监测需求,提出了一种采用光纤光栅(Fiber Bragg Grating,FBG)传感和多元线性回归相结合的起落架载荷测试方法。通过对起落架进行有限元仿真分析,得到了不同载荷作用下起落架的应变分布,根据应变分布特征确定FBG应变传感器的布片位置,形成应变传感网络。在此基础上,进行了主起落架地面静态载荷标定试验,并通过多元线性回归的方法形成应变-载荷计算方程组,最后对载荷计算方程组进行了验证性试验。研究结果表明,基于FBG的起落架载荷测试方法能有效反算起落架的三向载荷,反算得到的载荷与施加载荷的相对误差在5%以内,满足实际工程应用需求。     

Active damping of drive train oscillations for an electrically driven vehicle

A problem encountered with electrically driven vehicles are resonances in the drive train caused by elasticity and gear play. Disadvantageous effects caused by this are noticeable vibrations and high mechanical stresses due to torque oscillations. The oscillations can be damped using a control structure consisting of a nonlinear observer to estimate the torque in the gear and a controller, which computes a damping torque signal that is added to the driver's demand. The control algorithm was implemented in the existing motor control unit without any additional hardware cost. The controller was successfully tested in a test vehicle. The resonances can essentially be eliminated. The controller copes satisfactorily with the backlash problem.     

Enhancing the Sensitivity of Percolative Graphene Films for Flexible and Transparent Pressure Sensor Arrays

Flexible and transparent pressure sensor arrays can find applications in many places such as touch panels, artificial skin, or human motion detection. However, conventional strain gauges are rigid and opaque and are not suitable for such applications. Graphene‐based percolative strain gauges can overcome these challenges but currently are still in the infancy of their development. In this work, the performance of graphene‐based percolative strain gauges is investigated and guidelines to improve the durability and sensitivity of graphene films as sensing elements are developed. It is found that the gauge factor depends on the initial resistance of the graphene film. For the same film resistance, it is found that graphene flake size and film morphology also play a role in determining the gauge factor. Increasing the flake–flake resistance through assembly of surfactant molecules between graphene flakes provides an additional route to enhance the gauge factor. Furthermore, encapsulating the percolative film in micrometer‐thin Poly(methyl methacrylate) does not disrupt the sensing process but significantly improves the sensor's durability. Finally, thus enhanced graphene strain gauges are integrated into flexible and transparent pressure sensor arrays that exhibit high reproducibility and sensitivity.     

Fiber optic sensors focus on smart systems

Materials with structurally integrated fiber-optic sensors, the first step toward smart structures, which continuously monitor their own vibration, internal strain and deformation, temperature, and structural integrity are described. It is shown that the Fabry-Perot fiber-optic strain sensor has capabilities that far exceed those of conventional foil strain gauges, which holds the promise of responding to acoustic emission signals while simultaneously tracking the high loads likely to be encountered in practical structures such as aircraft wings. The same sensing system may be able to monitor the degree of cure during fabrication of thermoset composite structures. The fabrication and characterization of such all-fiber, intrinsic Fabry-Perot strain sensors are discussed. Passive and active homodyne signal recovery techniques used in the fiber-optic sensor systems are also described     

Suppression of polarisation-induced signal fluctuation in optic distributed sensing system based on stimulated Brillouin scattering

A new scheme capable of suppressing polarisation sensitivity in the Brillouin optical time domain analysis distributed sensing system is demonstrated. The polarisation-induced signal fluctuation is suppressed from >+300 μϵ(which causes measurement to fail) to +50 μϵ by introducing a cost-effective polarisation diversity scheme on the pump light. Stable distributed strain measurement along a 1.2 km singlemode fibre is achieved. This scheme needs no active component and the strain measurement time is only 3s.     

基于Boost电路与卡尔曼滤波的无刷直流电机转矩脉动抑制方法研究

无刷直流电机最大的问题是会产生转矩脉动,针对这一问题,设计采用一种Boost变换器与卡尔曼滤波相结合的方法,通过Boost变换器提高母线电压补偿换相时电流的跌落,卡尔曼滤波获得更精准的转速信号,减小电动机的转矩脉动。在Matlab/Simulink环境下搭建系统模型进行仿真,并结合实验验证,结果证明本文所提出方法能够有效的降低转矩脉动。     

基于超声电机的力矩补偿装置控制方法研究

为补偿卫星载荷运动产生的干扰力矩,设计了一种基于超声电机的力矩补偿机构。基于传统控制策略的比例、积分、微分(PID)闭环负反馈控制系统调速效果难以令人满意,在这种情况下建立了系统的数学模型,设计了基于模糊PI控制的闭环调速控制系统,并与传统的PI控制进行了对比。根据干扰力矩的给定形式,设计了飞轮运行的正弦速度给定曲线,仿真结果表明,该方法能够有效补偿载荷干扰力矩。此外,设计了以数字信号处理器(DSP)芯片为核心的硬件驱动控制电路,并进行了实验验证。结果表明,该算法比传统的PI控制效果更好,速度曲线跟踪精度明显提升。     

Sensors for Applications in Magnetic Resonance Environments

This paper analyzes sensing methods compatible with magnetic resonance imaging (MRI) and functional MRI (fMRI) reported in the literature, and presents the three generations of MR-compatible force/torque sensors we have developed for robotic systems to interact with human motion. Conventional sensors such as camera-based measurement systems, strain gauges or commercial force/torque sensors, and optical encoders may be used, if placed sufficiently away from the imaging region and equipped with adequate shielding and filtering in order to minimize electromagnetic interference caused by electric cables, the transducer, and electronics of surrounding equipment. However, electromagnetic interference can be avoided by using light transmission over optical fibers, in which case sensitive and noisy electronic components can be placed outside the MR room, and the MR compatibility issue is restricted to the used materials. Good performance can be obtained with sensing elements made from materials adapted to the location of use, combined with reflected or differential light intensity measurement over optical fibers. We have developed various force and position sensors based on this principle, ranging from MR Safe (for a definition and discussion of the terms MR Safe and MR Conditional, see Gassert , IEEE Eng. Med. Biol. Mag., pp. 12--14, May/Jun. 2008) milled polymer probes to MR Conditional assemblies combining beryllium copper blades with a polymer body, as well as smaller aluminum probes realized through a combination of milling and electric discharge machining. It appears that, in contrast to actuators, good performance is not in tradeoff with MR compatibility.     

激光辐照层合板的数值模拟与试验对比

对激光辐照复合材料层合板的应力应变进行模拟分析,获得了应力应变场分布及其变化规律。数值模拟首先获得试件各点随激光辐照时间变化的温度场,然后将温度场导入并分析了试件的热应力和热应变。结果显示：沿纤维方向应力由中心的最大拉应力过渡到距光斑边缘约5 mm处的最大压应力后逐渐减小;垂直纤维方向应力在光斑内及其附近均是压应力;Mises应力在光斑中心处最大并随各位置到中心距离的增大而减小。热冲击使各点应力在辐照初期产生波动,光强越大,波动的时间点越早。为了验证数值分析模型,在激光辐照的复合材料层合板正面光斑周围粘贴应变片,用动态应变仪测试多点的应变并与数值结果进行对比,数值模拟应变与实测应变吻合较好,最大相对误差为18.4%。     

Finite-element model-based fault diagnosis, a case study of a ceramic pressure sensor structure

Finite-element (FE) analysis is an efficient aid in the design optimisation of modern electronic devices. Simulation tools have dramatically reduced the product design cycle. The model validated with actual prototypes can also be used for other purposes such as failure analysis, fatigue prediction, reliability studies, etc. In this paper we present a case study of application of FE model in fault localisation in ceramic pressure sensor structures. The sensing elements are thick-film resistors acting as strain gauges, which translate the strain into an electrical signal. In the design phase, FE analysis was used to analyse the sensitivity of the thick-film resistors to the applied pressure. The same model was used for non-destructive fault diagnosis and troubleshooting of the prototype series. Selected examples illustrate the approach. FE model can also be used in the production test process. Since simulations are rather time consuming, quick fault localisation can be performed by a fault dictionary while in-depth diagnosis is performed by FE analysis.     

基于霍尔传感器的转速与转向测量方法

采用两路霍尔传感器作为敏感元件,测量传动齿轮两个齿尖之间的转动时间,并以脉冲信号的方式传输给单片机,单片机可由脉冲信号的时间和相位差计算传动齿轮的转速和判断转动方向。     

基于MEMS的力传感器薄膜应变计加工工艺

提出了在铝合金基体上磁控溅射80Ni20Cr薄膜电阻应变计的加工工艺,说明了其工艺的实现步骤。采用低弹性模量的铝合金制作力传感器的弹性体可以提高力/力矩传感器的灵敏度。提出了一种适合MEMS加工的全平面的力/力矩传感器弹性体结构。并介绍了薄膜电阻应变计构成的微型六维力传感器和薄膜厚度的测量手段。通过实验证实,此种薄膜工艺的应用提高了力传感器的测量精度。     

曲轴转速波动对某柴油机正时齿轮系动力学特性的影响

为了研究曲轴转速波动对正时齿轮动力学性能的影响,分别建立曲轴动力学模型与正时齿轮系动力学模型,在测试的基础上,研究了齿轮啮合冲击力随转速波动的变化规律,以及曲轴加装减振器前后的齿轮系冲击力与频域啮合力的变化。研究表明:随着转速的增加,转速的波动幅度增大,齿轮的最大冲击力增大,转速从1 000 r/m到3 000 r/m时,曲轴齿轮所受最大冲击力增大了近5倍。曲轴加装减振器后,各个齿轮冲击力平均减小了60%。曲轴的转速波动是导致该柴油机正时齿轮受到高冲击载荷的主要原因。     

Etched fibers as strain gauges

A class of optical fiber intensity sensors that do not require the use of external structures to impose perturbations on fibers is presented. The topological structures are formed directly onto the fiber cladding. The geometry of the features is defined photolithographically and the structures are formed by chemical etching. The etched fiber sensing elements have been fabricated and tested as strain sensors. Depending on the amount of the cladding material removed and the symmetry of the etched structure, the measured gauge factor of the etched fiber strain sensors may be larger than 100. The responses of the optical fiber strain gauges are linear, repeatable, have a high cyclic endurance and no measurable hysteresis. These sensors can be used to monitor a strain as large as 0.4%     

Improved torque fidelity in harmonic drive sensors through the union of two existing strategies

The torsional compliance of harmonic drives lends itself to torque sensing, but the elliptical wave generator in harmonic drives introduces a spatially dependent local torque ripple on the flexspline of harmonic drives. It is difficult to extract the applied torque signal from this local torque ripple if the applied torque is sensed at the flexspline of the harmonic drive. Previous methods have used spatially offset Wheatstone bridges or gain tuning to attenuate torque ripple. The authors have found that combining both of these techniques through a different wiring configuration can attenuate local torque ripple to /spl plusmn/0.5 N/spl middot/m, a better ripple reduction than either method alone. This local ripple reduction is adequate for large-range torque applications, but is not adequate for precision torque applications.     

基于光纤光栅的传动齿轮模态分析

利用光纤光栅传感器实现了基于快速应变响应的传动齿轮模态分析。基于波分复用技术组建光纤光栅传感网络,根据光纤光栅的应变响应数据完成齿轮的应变模态分析,并与基于声压传感器的齿轮试验模态分析结果进行对比,固有频率相对误差小于0.1%。为了实现光纤光栅传感器的快速应变采集,搭建了一套光纤光栅快速解调仪。该解调仪是基于体相位解调的单通道快速解调仪,采样速率最高为35kHz,使用LabVIEW编写了光纤光栅信号采集和解调软件。基于光纤光栅的齿轮应变模态分析方法附加质量小,比传统加速度传感器测量结果更准确,能够适应小型齿轮箱内部复杂和恶劣的测量环境,具有一定的应用价值。