基于Hopkinson杆和人工神经网络的三轴冲击力传感器同步解耦标定方法

三分量冲击力载荷的同步激励与输入输出间的精准建模是三轴冲击力传感器标定所面临的主要挑战。为了实现对三轴冲击力传感器的有效标定,使其能够准确测量空间中的三维冲击力载荷。首先,基于Hopkinson杆与矢量分解原理建立了一种高幅值（104 N量级）、窄脉宽（10?4 s量级）可计量三分量冲击力载荷的同步激励方法,实现了对三轴冲击力传感器的同步加载。然后,基于最小二乘原理与矩阵微分构建了三轴冲击力传感器的线性标定模型,并通过改变子弹结构与冲击气压揭示了线性解耦标定模型中传感器主灵敏度系数与轴间耦合灵敏度系数并非固定常数而均与冲击力载荷脉冲构型（幅值、脉宽）相关的冲击特性。最后,将能够反映载荷构型信息的传感器各轴输出电压脉冲的幅值与脉宽作为影响因素,并以神经元的形式添加到人工神经网络（artificial neural network, ANN）的输入层,建立了基于ANN的三轴冲击力传感器输出电压与输入载荷间的代理模型,实现了数据驱动的三轴冲击力传感器非线性解耦标定。结果表明,相对最小二乘模型,ANN标定精度更高,采用ANN进行三轴冲击力传感器标定具有可行性和有效性。     

Analysis of deadweight oscillation in a deadweight force machine using a build-up system

This paper describes a build-up system that measures the deadweight oscillation in a deadweight force machine. When a build-up system is calibrated using a deadweight machine, the oscillating signal components of force transducers in the build-up system are strongly related to the motion of deadweight. The authors have, therefore, proposed a model based on the analysis of oscillating signals of force transducers to measure the deadweight oscillation. The analysis of the force transducer signals and the displacement sensor signals shows the validity of the proposed model. The authors have also investigated the behavior of deadweight motion for a deadweight force machine of 498 kN using the proposed model.     

连续体覆冰导线模型的舞动实验研究

建立了适合连续体覆冰导线舞动实验的专用风洞,以连续体单跨覆冰单导线模型为实验对象,采用激光传感器测量了导线不同位置处的位移响应,得到了导线在不同风速下的舞动振型,利用力传感器得到了导线舞动时的动张力。结果表明:覆冰导线在来流风场作用下进行舞动,在随风速增大的过程中先后经历了两个大幅舞动阶段,一阶模态和二阶模态在两个阶段中分别被激发;动张力幅值与舞动幅值基本成正比,动张力频率包含导线模型舞动频率的一倍频和二倍频。在大风速时,导线模型的舞动为多阶模态的耦合振动,在舞动过程中无固定的波峰和结点。     

混凝土框架结构内力测量传感器研制

研制了一种可用于混凝土结构试验中测量柱底截面轴向力、剪力和弯矩的内力测量传感器。该传感器主要由加载板、基座、4根竖向测力杆和2根水平测力杆组成。使用时,柱底截面的内力通过加载板传递给6根测力杆,根据6根测力杆的结果,通过力平衡方程可以计算实际加载的轴向力、剪力和弯矩的大小。对该传感器进行了4种工况下的标定试验。结果表明,传感器的测量误差满足框架结构内力测量精度要求。将该传感器应用到单层两跨的钢筋混凝土框架推覆试验中,获得了整个试验过程中构件的内力时程。     

Investigation of the performance of an ischial load-bearing leg brace

Partition of loads between the human leg and its protective brace was investigated during the normal walking stride of a patient fitted with a conventional ischial weight-bearing leg brace. Strain-gage force transducers were designed and installed to measure loads in the brace, and a strain-gage force plate was built to measure the floor reaction of the patient's footstep. The load measured by the force plate is equal to the total load carried by the leg and the brace, and it was resolved into components along axes fixed with respect to the leg and compared with the force carried by the leg brace to determine the distribution of the load between the brace and leg. Curves of force in three orthogonal directions and torque about the vertical axis of the leg are presented and discussed.     

动载实验中压电晶体应力量计的设计与应用

各种压电器件广泛用于电子工业、信息传输、医学诊断等许多领域,以实现能量转换、传感、驱动、频率控制等功能. 特别地,压电晶体以其高频响的压电效应,在动载实验中用于动态应力的测试. 利用其特有的各向异性特性,通过设计特殊的切型方向,可以实现对不同应力的测试. 本文通过分析各向异性晶体的特性,从压电效应的基本原理出发,导出了利用各向异性晶体作为剪应力量计的设计思想,并给出了两种典型的动态剪应力计:17.705°Y 切石英和165.44°Y 切铌酸锂晶体.      

Base strain effects on force measurements

Force transducers directly interact with their environment. In this study, a force transducer is attached to the midpoint of a free-free beam and is used to measure the force on a rigid mass that vibrates with the beam. The ratio of force to mass times acceleration is measured for several different masses over a frequency range that includes the first four odd natural frequencies of the beam. Then the force transducer is mounted so that the beam's strain is isolated from the transducer. The tests are repeated. The results dramatically illustrate the effects of base strain on the force measurements. A simple theoretical model is developed that explains the vertical axis shift in the calibration curve. Paper was presented at SEM 1994 Spring Conference and Exhibits.     

Strain-gage installations for adverse environments

Seven projects in which resistance-type bonded strain gages were used in adverse environments are described. The projects involved: (1) force measurements in a 10^?10 torr vacuum, (2) load measurements over a temperature range of 75 to 300° F, (3) displacement measurements in a nonconductive fluid at 500° F, (4) dynamic displacement measurements in an electric field, (5) strain measurements in air at 600° F, (6) dynamic displacement and strain measurements to ?320°F, and (7) strain measurements in water at pressures up to 2500 psi and temperatures up to 300° F. This report provides detailed information about the gage installations, the transducers used and the performance obtained.     

DESIGN AND APPLICATIONS OF PIEZOELECTRIC CRYSTALS TRANSDUCER IN DYNAMIC EXPERIMENTS

各种压电器件广泛用于电子工业、信息传输、医学诊断等许多领域,以实现能量转换、传感、驱动、频率控制等功能. 特别地,压电晶体以其高频响的压电效应,在动载实验中用于动态应力的测试. 利用其特有的各向异性特性,通过设计特殊的切型方向,可以实现对不同应力的测试. 本文通过分析各向异性晶体的特性,从压电效应的基本原理出发,导出了利用各向异性晶体作为剪应力量计的设计思想,并给出了两种典型的动态剪应力计:17.705°Y 切石英和165.44°Y 切铌酸锂晶体.     

Impact-force source and impact-force calibrator

A pendulum-force transducer called an impact-force source has been developed which can serve two purposes. The impact-force source can be used to accurately calibrate other force transducers dynamically and can also be used to supply a known and repeatable impact half-sine-type force for impact studies. The magnitude and duration of the impact force produced by the impact-force source can be varied by changing certain physical parameters of the force source. A simple design procedure was developed to determine the values of the parameters of the force source. Experiments were conducted to test the limitations of the impact-force source in its use as a dynamic-force calibrator and as a known source of impact force. The results of these experiments indicate that the force source could be a useful laboratory instrumentation tool.     

S型测力传感器的动态特性与标定

本文对 S 型测力传感器的动态特性进行了研究。采用模态分析测量技术,测定了传感器的固有频率、模态质量、模态刚度、模态阻尼和阻尼比,并以动画形式显示了其主振型.作出激振力与传感器应变片输出信号的传递函数幅频和相频特性曲线,可简便地确定传感器工作频率范围及相应的误差。     

Direct measurements of controlled aerodynamic forces on a wire-suspended axisymmetric body

A novel in-line miniature force transducer is developed for direct measurements of the net aerodynamic forces and moments on a bluff body. The force transducers are integrated into each of the eight mounting wires that are utilized for suspension of an axisymmetric model in a wind tunnel having minimal wake interference. The aerodynamic forces and moments on the model are altered by induced active local attachment of the separated base flow. Fluidic control is effected by an array of four integrated aft-facing synthetic jet actuators that emanate from narrow, azimuthally segmented slots, equally distributed around the perimeter of the circular tail end. The jet orifices are embedded within a small backward-facing step that extends into a Coanda surface. The altered flow dynamics associated with both quasi-steady and transitory asymmetric activation of the flow control effect is characterized by direct force and PIV measurements.     

Reliability analysis of ultrasonic power transducers

Ultrasonic power transducers are commonly used in applications like cleaning, plastics welding or sonochemistry. Typically, the design of transducers for new applications is a tedious iterative process of design, prototype construction and tests. The transducers must fulfill the needs and restrictions of the specific application, as otherwise the transducer might be oversized or fail during operation. While reliability has been studied worldwide intensively in the case of piezoelectric multilayer actuators—driven by car industry which now uses such actuators in their fuel injection systems—nearly no literature is available for the reliability of ultrasonic power transducers. As well, manufacturers seldom present data about aging or lifetime of their components. To enhance the knowledge about typical failure mechanisms of ultrasonic power transducers under different load conditions, our contribution—as a first step—reports on a theoretical study on the reliability of common known ultrasonic transducers and gives some examples of typical failures and their influence on the characteristics of the transducer.     

Lateral pull-in instability of electrostatic MEMS transducers employing repulsive force

Nonlinear Dynamics - We report on the lateral pull-in in capacitive MEMS transducers that employ a repulsive electrostatic force. The moving element in this system undergoes motion in two...     

DETERMINATION OF QUADRICEPS FORCES IN SQUAT AND ITS APPLICATION IN CONTACT PRESSURE ANALYSIS OF KNEE JOINT

While the quadriceps muscles of human body are quite important to the daily activities of knee joints,the determination of quadriceps forces poses significant challenges since it cannot be measured in ...     

Design considerations and calibration of stress transducers for soil

Strain gage pressure transducers are most frequently used for soil stress state determinations. Their construction, rugged and mechanically resistant, enables them to measure stresses within a wide range (up to 500 kPa) in harsh conditions. Output signals are easily readable and stable. The accuracy of the measurements, however, depends upon proper design and calibration before use in soil. This paper contains information on design considerations and results from calibration tests of transducers of two membrane diameters: 20 and 30 mm. The calibration test stand, as well as calibration procedures, are described in detail. For calibration tests, natural soils were used, as well as steel balls, to simulate the effect of the aggregated structures of arable soils and grain materials. The calibration method considered different soil types as well as soil water content. Soil and its water content were found to have an effect on output scale factor.     

An <Emphasis Type="Italic">In Situ</Emphasis> Ultrasonic Technique for Simultaneous Measurement of Longitudinal and Shear Wave Speeds in Solids

Ultrasonic wave speed measurements are widely used to infer the elastic properties of solids. In the standard method, longitudinal and shear transducers are used separately to measure the corresponding wave speeds in a material. A new experimental method is introduced for simultaneously measuring the longitudinal and the shear wave speeds using a single set of longitudinal or shear transducers. The method can also be used to measure the wave speeds in situ during deformation by placing the transducers along the loading axis. The transducers are housed in a specially designed fixture such that they are not subjected to loading. The technique is demonstrated by performing uniaxial compression experiments on fully dense isotropic solids (where the wave speeds are not expected to change during deformation) and in polymeric foams (where the wave speeds are affected by damage).     

Inertial effects of quartz force transducers embedded in a split Hopkinson pressure bar

An aluminum split Hopkinson pressure bar is instrumented with quartz force transducers and used to test low impedance materials. Two transducers are used, one at the interface between the specimen and the incident bar and the other at the interface between the specimen and the transmitter bar. It is shown that the stress measured by the incident bar gage often contains a substantial acceleration component, i.e., a significant portion of the signal recorded by the gage is due to its own inertia and not representative of the stress within the sample. Attempts are made to actively compensate for this with measurements of the acceleration of the gage. This is done in three ways: (i) by differentiation of the interface velocity, as determined by a standard strain gage analysis; (ii) by a more direct determination of acceleration, using a measurement of the strain gradient within the bar; (iii) by adding a compensation crystal and mass to the gage to remove the inertial component from the output. It is shown that all three techniques successfully mitigate inertial effects.