A new approach to test torque transducers under dynamic reference regimes

A system is proposed to test torque transducers under reference dynamic regimes, where the reference torque is provided by the application of angular acceleration to a coupled mass moment of inertia. The dynamic regimes include different angular velocity intervals, angular velocity steps and high torque rates. A basic general assembly is proposed and theoretical and practical analyses are performed to determine the primary parameters and depict components. The results show that the angular velocity and torque curves are repeatable and also that the simultaneous responses of torque and acceleration are linear. The mass moments of inertia involved in the measurement process are evaluated. The results provide a positive direction for future tests with transducers and the objective to fill the gap in the metrological traceability chain for torque measurement with dynamic tests and sensor verification.     

基于正弦力加载的力传感器动态标定技术研究

针对国内现有动态标定装置精度不高、重复性较差的问题,提出了一种基于正弦力加载的新型力传感器动态标定方法;对该标定方法做了详细介绍,阐述了该标定系统中最关键的正弦机构的工作原理;利用基于最小二乘的曲线拟合法对力传感器和位移传感器输出正弦电压的幅值进行了求解,并以此为基础,依据相应公式在LabVIEW中设计了数据处理程序,实现了对力传感器动态灵敏度的精确求解;搭建了实验平台,对Interface 1010AJ型力传感器进行了1 Hz~5 Hz的动态标定,并分析了实验结果。研究结果表明,该新型的力传感器动态标定系统具有良好的精度,其误差在1.5%内。     

Identifiability of fractional order systems using input output frequency contents

In this paper, issues related to the identifiability of a fractional order system having its input and output frequency contents are discussed. The effects of the commensurate order α in the identifiability of the model structure and model parameters are analytically studied. It is shown that both identifiabilities (model structure and model parameters) are reduced remarkably for smaller values of α. This phenomenon is observed even though the input signals are rich enough and system belongs to the model set. Our understanding is that the problem arises since differences among different members of the model set fall beyond the practically recognizable precision range. The issue is more problematic when α is smaller and measurements are noisy.     

应用递推神经网络的传感器动态建模研究

根据动态校准实验结果建立传感器的动态数学模型 ,以研究传感器的动态性能 ,是动态测试的一个重要内容。研究了递归神经网络模型在传感器动态建模中的应用。递归神经网络模型采用具有输入层、中间层、输出层的三层网络结构 ,整个网络的特性决定于相邻层间的连接权。采用递推预报误差算法训练神经网络 ,具有收敛速度快、收敛精度高的特点。由于其反馈特征 ,使得递归神经网络模型能获取系统的动态响应特性。该方法特别适用于传感器非线性动态建模 ,而且避免了传感器模型阶次的选择的困难。试验结果表明 ,应用递归神经网络对传感器进行动态建模是一种行之有效的方法     

航空齿轮传动系统的动态特性分析

建立了齿轮传动系统的动力学模型，给出了系统的运动微分方程组，分析了啮合阻尼和齿形误差对航空齿轮传动系统动态特性的影响，发现了辐板齿轮传动系统的振动规律，为航空齿轮传动系统的动态设计提供了有益的理论依据     

LL680挠性剑杆织机动态特性测试研究

针对LL680挠性剑杆织机在高速化过程中遇到的振动过大等问题,通过对其进行动态特性的测试与分析,应用NI振动测试设备以及加速度传感器,找到振动的主要振源即为织机的凸轮箱,分析机械结构在结构动力学上的薄弱环节,得到通过对织机的主要支撑部件墙板优化设计,使得固有频率有所改变、着重加强其X方向的刚度以及对振源构件的优化等措施可以达到高速化效果的结论。为LL680高速化解决提供依据与方向。     

超磁致伸缩换能器的建模方法

超磁致伸缩抉能器工作时同时受机械力场和电磁场的双重作用．特性必然受机械结构参数和电源特性的双重影响,为寻找最佳的机械结构参数和电源特性参数．必须建模研究。讨论超磁致伸缩换能器的建模方法,为换能器的设计、研究提供借鉴。     

The influence of temperature and humidity on the sensitivity of torque transducers

This paper presents a study of the effect of temperature and relative humidity on the sensitivity and the characteristics of torque transducers such as residual zero torque, reversibility and creep. Temperature and humidity coefficients of the sensitivity take positive as well as negative values. Linear dependence is found between the influence of temperature/relative humidity and the applied load. For some torque transducers, under temperature change the sensitivity has a transient overshoot reaching up to 3 times the steady amplitude. Also there is a small effect of temperature/relative humidity on the transducer’s parameters such as residual zero torque, reversibility and creep. Equations are presented to predict the effect of temperature/relative humidity changes on the sensitivity of torque transducers.     

Analysis of acousto-ultrasonic characteristics for contact-type transducers coupled to composite laminated plates

The acousto-ultrasonic (AU) input–output characteristics for contact-type transmitting and receiving transducers coupled to composite laminated plates are considered in this paper. Combining a multiple integral transform method, an ordinary discrete layer theory for the laminates and some simplifying assumptions for the electro-mechanical transduction behaviour of the transducers, an analytical solution is developed which can deal with all the wave processes involved in the AU measurement system, i.e. wave generation, wave propagation and wave reception. The spectral response of the normal contact pressure sensed by the receiving transducer due to an arbitrary input pulse excited by the transmitting transducer is obtained. To validate the new analytical–numerical spectral technique in the low-frequency regime, the results are compared with Mindlin plate theory solutions. Based on the analytical results, numerical calculations are carried out to investigate the influence of various external parameters such as frequency content of the input pulse, transmitter/receiver spacing and transducer aperture on the output of the measurement system. The results show that the presented analytical–numerical procedure is an effective tool for understanding the input–output characteristics of the AU technique for laminated plates.     

Finite element analysis of piezoelectric underwater transducers for acoustic characteristics

This paper presents a simulation technique for analyzing acoustic characteristics of piezoelectric underwater transducers. A finite element method is adopted for modeling piezoelectric coupled problems including material damping and fluid-structure interaction problems by taking system matrices in complex form. For the finite element modeling of unbounded acoustic fluid, infinite wave envelope element (IWEE) is adopted to take into account the infinite domain. An in-house finite element program is developed and technical issues for implementing the program are explained. Using the simulation program, acoustic characteristics of tonpilz transducer are analyzed in terms of modal analysis, radiated pressure distribution, pressure spectrum, transmitting-voltage response and impedance analysis along with experimental comparison. The developed simulation technique can be used for designing ultrasonic transducers in the areas of nondestructive evaluation, underwater acoustics and bioengineering. This paper was recommended for publication in revised form by Associate Editor Maenghyo Cho Jaehwan Kim received his B.S. degree in Mechanical Engineering from Inha University, in 1985. He received his M.S. degree from KAIST in 1987 and his Ph.D. degree from The Pennsylvania State University in 1995. Dr. Kim is currently a Professor of the Dept. of Mechanical Engineering at Inha University, Inchoen, Korea. He serves as an Associate Editor of Smart Materials and Structures. He is the director of Creative Research Center for EAPap Actuator supported by KOSEF. Dr. Kim’s research interests are smart materials such as piezoelectric materials, electroactive polymers and their applications including sensors, actuators, motors and MEMS devices. Heung Soo Kim received his B.S. and M.S. degrees in the Department of Aerospace Engineering from Inha University, Korea in 1997 and 1999, respectively. He obtained his Ph. D degree in the Department of Mechanical and Aerospace Engineering from Arizona State University in 2003. He is now working as an assistant professor in the School of Mechanical and Automotive Engineering, Catholic University of Daegu. His main research interests are in biomimetic actuators and sensors, structural health monitoring, smart materials and structures as applied to aerospace structures and vehicles.     

三坐标测量机动态误差补偿的研究

本文研究了三坐标测量机在高速测量过程中的动态误差。针对一移动桥式三坐标测量机,分析了其动态误差的产生原因,建立了动态误差的数学模型,对动态误差进行了全面的测量和补偿。实验证明动态误差具有一定的重复性,可用软件补偿,从而提高三坐标测量机快速测量的精度。     

超磁致伸缩换能器的建模方法

超磁致伸缩换能器工作的同时受到机械力场和电磁场的双重作用,特性必然受机械结构参数和电源特性的双重影响,为寻找最佳的机械结构参数和电源特性参数,必须建模研究。本文讨论了超磁致伸缩换能器的建模方法,为换能器的设计、研究提供借鉴。     

行星传动动态均载特性分析

从动力学角度建立2K-H型行星传动系统的计算模型.针对各构件的制造和安装误差,运用当量啮合误差原理和动力学分析方法,推导行星传动的运动微分方程,建立系统的动力学分析模型,分析系统的动态均载特性和各误差的参数变化对系统均载特性的影响,此方法计算结果与已有试验结果十分吻合.分析结果表明,浮动太阳轮对系统的均载特性有很大的改善:装配误差和安装误差共同对系统的均载特性起作用,只减少某一个误差值达不到良好的均载效果;转速对系统的均载有较大的影响.     

Dynamic characterization of multi-axis dynamometers

In this paper, we present a comprehensive technique for accurate determination of three-dimensional (3D) dynamic force measurement characteristics of multi-axis dynamometers within a broad range of frequencies. Many research and development efforts in machining science and technology rely upon being able to make precise measurements of machining forces. In micromachining and high-speed machining, cutting forces include components at frequencies significantly higher than the bandwidth of force dynamometers. Further, the machining forces are three-dimensional in nature. This paper presents a new experimental technique to determine the three-dimensional force-measurement characteristics of multi-axis dynamometers. A custom-designed artifact is used to facilitate applying impulsive forces to the dynamometer at different positions in three dimensions. Repeatable and high-quality impulse excitations are provided from a novel impact excitation system with a bandwidth above 25 kHz. The force measurement characteristics are presented within 25 kHz bandwidth using 3 × 3 force-to-force frequency response functions (F2F-FRFs), which capture both direct and dynamic cross-talk components to enable fully three-dimensional characterization. The presented approach is used to characterize the dynamic behavior of a three-axis miniature dynamometer. The effects of force-application position, artifact geometry, and dynamometer-fixturing conditions are explored. Moreover, the relationship between the force-measurement characteristics and structural dynamics of the dynamometer assembly is analyzed. It is concluded that the presented technique is effective in determining the force-measurement characteristics of multi-axis dynamometers. The changes in dynamometer assembly that affect its structural dynamics, including artifact (workpiece) geometry and especially the fixturing conditions, were seen to have a significant effect on force-measurement characteristics. Furthermore, the force-measurement characteristics were seen to change substantially with the force-application position. The presented technique provides a foundation for future compensation efforts to enable measuring forces within a broad range of frequencies.     

孔辐剪切应变式动态负荷传感器的研制

本文论证了剪切应变式负荷传感器更适用于动态负荷测量,推导出传感器的设计计算公式。用实测数据展示了孔辐剪切式负荷传感器优异的动态性能。     

Frequency agility in cognitive radios: A new measurement algorithm for optimal operative frequency selection

The wide diffusion of multimedia services delivered also on mobile terminals (smart-phone, tablets and so on), is causing a fast and continuous increasing of spectrum usage demand. Nevertheless, several studies have demonstrated that portions of radio spectrum are not in use for significant periods of time. This waste of spectrum shows the necessity to design a more flexible way to manage this resource with respect to the traditional frequency allocation policy.In this context, cognitive radios play a crucial role, because they are thought to enable such flexible spectrum allocation by suitably changing their operating frequency without interfering with other transmitters. As a consequence, they have to implement a method to dynamically select the appropriate operating frequency based on the sensing of signals from other transmitters. This capability is usually called frequency agility.Several spectrum sensing methods have been proposed in literature, whereas few studies have been focused on the development of methods for satisfying the frequency agility capability.In this framework, the paper proposes a novel measurement algorithm able to meet those requirements. It is based on two sequential steps: the former performs a preliminary spectrum sensing aimed at excluding the frequency ranges surely occupied by primary users, while the latter performs a more refined analysis, restricted to frequency intervals not excluded by the previous stage, with the aim of selecting an operating frequency for the cognitive radio terminal that minimizes potential interferences with primary users. It has been designed for operating in scenarios involving signals based on OFDM or which present spectrum shapes and slopes similar to ones shown by OFDM.A key feature of the proposal is the ability to operate even in scenarios characterized by low signal-to-noise ratios as confirmed also by the experimental campaign.     

Dynamic analysis of evaporator characteristics

An analysis of the dynamic characteristics in an evaporator was numerically performed for control and design of the refrigeration and air conditioning systems. The important factors, such as refrigerant flow rate, inlet enthalpy, inlet air velocity and air temperature, are incorporated with this analysis. An evaporator is modeled for the dynamic characteristics analysis separated into three regions which are the two-phase region, the saturated vapor region and the superheated vapor region. The basic equations of each region were derived in the continuity, heat energy equilibrium and heat transfer equations. The transfer functions of the dynamic characteristics were obtained by the linearization and Laplace transformation. The dynamic response characteristics were evaluated on the Bode diagram with the frequecy response method. These results may be used for the analysis of the dynamic characteristics and design in the total system.     

Modeling and compensation of MEMS gyroscope output data based on support vector machine

The modeling and compensation method of the angular rate error of MEMS gyro MG31-300, based on support vector machine, is described in this paper. Reference angular rates were generated by the single-axis rate turntable. The output data of MG31-300 under different input angular rates were collected and analyzed. Considering the nonlinear and random characteristics of the angular rate error, the support vector machine model is established, which uses the output voltage of gyro as the input and provides angular rate error as the output. The resolution of the angular rate error is improved by this modeling method. The result shows that the fitting error of the model was 0.0701°/s (1σ). Finally, within MG31-300 measuring range (−300°/s to 300°/s), some testing points besides the training samples were selected to testify and verify the model. The results indicate that, the support vector machine model has high precision and good generalization ability.     

客车车身前围动刚度分析及优化

基于MSC.PATRAN/NASTRAN软件建立某国产前置发动机客车车身的有限元分析模型,采用直接频率响应法,拾取前围相应点的加速度响应,通过分析得出前围共振的位置以及相应的频率段,进而以前围以及与前围直接相连的杆件的截面尺寸作为优化变量,以响应点加速度响应的幅值作为状态变量,进行频率响应优化。结果表明:该分析方法可有效进行客车车身前围动刚度优化,为实现整车动刚度的优化提供参考。