钻柱信道中声信号传输的接收特性分析

针对周期性管结构信道特征,构建钻柱内一维低频纵波传输的有限差分模型,应用单个加速度传感器作为声接收器,在时、频域仿真分析了换能器接收位置对声信号传输特性的影响规律。在此基础上,考虑信道内多重回波对声通信信号检测的影响,基于信道容量的分析,引入上、下行信道的单位脉冲激励响应,设计了一种基于双声接收器模式的回波噪声抑制方法,并利用倒频谱解析算法,求解接收信号中的回波信息,分析了单、双接收器工作模式下信道响应特征。数值仿真结果表明,双接收模式可有效抑制井下回波噪声,改善信噪比,从而实现更佳的信道接收性能。     

随钻数据声波NC OFDM传输及噪声抑制的研究

随着随钻测井技术的高速发展,多维立体化地层数据的实时传输变得尤为重要。针对目前传统传输方式的低速率、高成本及非实时性,提出了一种基于非连续正交频分复用调制的声波传输方式。首先,利用传输矩阵法对钻柱信道的幅频特性进行仿真,并在此基础上提出了信道估计算法以获取子信道的频率响应;然后,采用双加速度传感器阵列接收相移声波信号,通过接收信号的相关性可以有效的抑制上行传输中地面强噪声的干扰;最后设计了一套通信测试装置,对实验钻柱信道下系统传输性能进行验证。仿真及实测结果表明,该方案可以具有较高的传输速率和可靠性。     

钻柱声传输的OFDM调制方法实现

为提高油气开采过程中随钻测井(LWD)数据传输速率,针对钻柱声传输技术中因周期性边界引起的色散和多重回波问题,从数据通信的角度出发,将正交频分复用(OFDM)多载波调制技术引入声传输系统,并以钻杆为信道,采用PC机结合FPGA模块和数据采集卡的形式,搭建了数据传输实验平台。数据传输实验结果表明,基于OFDM调制方式的短节钻杆声传输方案可实现160 bit/s的传输速率,该方案同时可为后续的钻柱声传输设计与实验提供方法指导。     

一种新的基于DSP的声时延估计方法

针对传统声时延估计算法速度较慢的问题,提出了基于脉冲声源和DSP的时延估计方法.声脉冲信号可认为是脉冲信号对声信号的调制,解调出脉冲信号,利用DSP捕捉单元捕捉脉冲边沿,即可得到时延估计.该方法不需要对声信号进行数模转换,也不需要大量数据处理,速度较快.设计了系统硬件电路,通过实验验证和分析,证明了该方法能够满足高速定位的需要.     

井下工程参数测量短节设计与制造

旋转导向钻井技术能够成功实现的关键技术之一是要实时测量出近钻头处的钻井工程参数(钻压、扭矩、侧向力等)。研制了一种井下工程参数测量短节,它可连接在钻柱的不同部位随同钻柱下井,实测、记录并存储钻柱在井下不同位置的受力情况,在测量短节中安放井下电源、传感器及数据采集电路,配置了MWD数据接口,可实现数据存储和实时传输,这样就可获取到真实的井下工程参数,还可将数据用于钻柱动力学分析以验证各理论模型的准确性。介绍了测量短节的结构设计、强度校核与加工制造。     

钻柱内声传输特性的信道建模与分析

为准确获取钻柱信道内声信号传输特性,基于一维低频纵波传输理论,应用有限差分法和传递矩阵法构建了周期性管结构钻柱信道模型,引入不同接收边界、钻柱长度等实际条件进行了信道瞬态响应仿真,研究了两种建模方法在信道模型求解中的性能,并分析了空间步长对信道模型分析的影响规律.计算结果表明,两种方法均能获得通阻带交替且通带伴有谐振尖峰的梳状滤波器频谱结构;但对于较长钻柱,受网格划分与步长选取影响,有限差分法引入的数值计算误差将产生频散,并导致通带平滑且谐振尖峰数目减少,而传递矩阵法则更适用于较长或具有非周期性结构的复杂钻柱信道频域分析.     

基于FPGA的简易数字信号传输性能分析系统

基于 FPGA 产生伪随机信号和曼彻斯特编码,以 MSP430为基本功能控制单元,通过三路低通滤波器和伪随机信号信道噪声来模拟传输信道,设计了一个以数字信号发生器,模拟传输信道和数字分析电路为核心的简易数字信号传输性能分析系统,实现了数字信号传输特性测试.测试表明系统工作稳定,输入信号动态范围大,眼图清晰,达到了设计要求.     

氦光泵磁敏传感器共振信号模拟装置设计

氦光泵磁敏传感器和检测系统共同实现对磁场的测量。验证检测系统能否正常工作的传统方法是制作出整个传感器后进行调试。针对检测系统的可行性验证,设计了共振信号模拟装置。产生的磁共振信号能够模拟光学系统的功能,通过调制域测频实现了对检测系统反馈信号的实时测量。实验测试表明,该装置能够验证检测系统的可行性,其性能十分接近氦光泵磁敏传感器,并且具有测量精度高、实时性好、稳定可靠、不依赖工作环境、制作成本低等特点。     

接触网感应式有电示警无线监测装置研究

为保证接触网越区供电的电能质量,设计了一套针对接触线带电状态的感应式测量无线监测系统。系统基于COMSOL搭建静电电容空间传感器电路仿真模型,分析单线接触网电位分布特性并推导测量装置各级的电压映射关系。采用TMS320F28377最小系统板搭配OPA2171、CC2530等外围电路模块采集接触线电压信号。在模拟WiFi环境的强干扰下,提出基于HMM的算法降低ZigBee网络丢包率,并将电压数据发送至上位机,实现铁路局监控中心对接触线电压信息的远程访问。实验证明:装置精度等级高、动态范围良好,具备信道重叠时择优跳信道能力。     

多传感器测试系统设计与分析

落锤式信号发生装置已在工程中广泛应用。搭建了全自动落锤信号发生装置,通过PLC对步进电动机进行控制实现锤体的上升和下降,采用多传感器测量信号;设计结合实际的测量传感器,测试加速度、冲击力和动态压力三个参量,通过作为数据处理装置的电荷放大器,然后通过总线传输,最终在计算机处理平台LABVIEW上,对数据进行处理和显示。     

An experimental rig for near-bit force measurement and drillstring acoustic transmission of BHA

An experimental rig for near-bit force measurement and drillstring acoustic transmission of bottom-hole assembly (BHA) is designed and implemented to investigate downhole dynamic behaviors of BHA. By using a developed dynamic force sensor device with a four-straight beam strain gauge, the rig can measure axial, lateral forces and torques exerted on simulated drillstring while rotating. For the upward transmission of downhole dynamic force data, drillstring acoustic telemetry method is further analyzed by transient numerical simulation. Considering acoustic signal attenuation and transmissibility, a narrow pulse on-off keyed modulated time-delay signal transmission method is developed. The near-bit force measurement experiments of BHA are performed under different weight on bit loads, deviation angles and drill pipe combinations. The obtained force data are transmitted via acoustic waves propagating along the simulated drillstring. The results show that acoustic transmission rate is approximated 77 bit/s along 6.4-m simulated drillstring under 1-W power excitation in the laboratory.     

基于ANSYS的钻柱振动规律分析

根据牙轮钻头与井底岩石互相作用的特点,将钻柱视为一连续的管梁结构,采用ANSYS工程软件,对钻柱纵向振动规律进行了分析。结果表明:钻柱系统各阶振动固有频率相差约1Hz左右,容易出现共振。高频振动时,钻柱出现"分段振动"的特点,下部钻铤动态力显著增加;转盘转速对钻柱振动的影响较大,当接近共振点时,下部钻铤螺纹联接处动态力呈数量级增加;钻压对钻柱振型、轴向动态力的影响不大。     

基于电磁超声技术的高强度螺栓轴力测量仪

基于电磁超声技术,研制了一款手持式高强度螺栓轴力测量仪,具有非接触、无需打磨、无需耦合剂和实时测量的特点.设计了可同时激发横波和纵波的电磁超声探头,实现了双波法轴力测量,能够解决在役螺栓长度未知的问题;设计了基于FP GA的高频大功率脉冲发射模块和低噪声信号调理模块,实现了电磁超声探头的激励与超声信号的接收;设计了基于...     

Design and testing of an innovative measurement device for tyre-road contact forces

The measurement of tyre-road contact forces is the first step towards the development of new control systems for improving vehicle safety and performances. Tyre-road contact forces measurement systems are very expensive and significantly modify the unsprung masses of the vehicle as well as the rotational inertia of the tyres. Thus, vehicle dynamics results are significantly affected. As a consequence, the measured contact forces do not correspond to the contact forces under real working conditions. A new low-cost tyre-road contact forces measurement system is proposed in this paper that can be applied to passenger cars. Its working principle is based on the measurement of three deformations of the wheel rim through strain gauges. The tyre-rim assembly is thus turned into a sensor for tyre-road contact forces. The influence of the strain gauges position onto the measurement results has been assessed through finite element simulations and experimental tests. It has been proven that, for a large variety of rims, the strain gauge position that leads to high signal-to-noise ratios is almost the same. A dynamic calibration procedure has been developed in order to allow the reconstruction of contact force and torque components once per wheel turn. The capability of the developed device to correctly estimate tyre-road contact forces has been assessed, in a first stage, through indoor laboratory experimental test on an MTS Flat-Trac^® testing machine. Results show that the implemented measuring system allows to reconstruct contact forces once per wheel turn with a precision that is comparable to that of existing high-cost measurement systems. Subsequently, outdoor tests with a vehicle having all four wheels equipped with the developed measuring device have also been performed. Reliability of the measurements provided by the developed sensor has been assessed by comparing the global measured longitudinal/lateral forces and the product of the measured longitudinal/lateral accelerations times the vehicle mass. A good agreement has been found during all the performed manoeuvres.     

Experimental investigation of longitudinal-wave pulses generated by a thermoacoustic emitter

Experimental investigations of pulses of longitudinal acoustic waves generated in a metal by short laser pulses are presented. The beam pattern of acoustic radiation, the amplitudes and shapes of acoustic pulses as functions of the laser radiation intensity and laser spot dimension are discussed. The results are analyzed in terms of the model of a thermoacoustic emitter in the form of a heated disk generating a pulse of axial and radial stress through the thermoelastic and hydrodynamic mechanisms.     

Identification of the nonlinear excitation force acting on a bowed string using the dynamical responses at remote locations

For achieving realistic numerical simulations of bowed string instruments, based on physical modeling, a good understanding of the actual friction interaction phenomena is of great importance. Most work published in the field including our own has assumed that bow/string frictional forces behave according to the classical Coulomb stick-slip model, with an empirical velocity-dependent sliding friction coefficient. Indeed, the basic self-excited string motions (such as the Helmholtz regime) are well captured using such friction model. However, recent work has shown that the tribological behavior of the bow/string rosin interface is rather complex, therefore the basic velocity-dependent Coulomb model may be an over-simplistic representation of the friction force. More specifically, it was suggested that a more accurate model of the interaction force can be achieved by coupling the system dynamical equations with a thermal model which encapsulates the complex interface phenomena. In spite of the interesting work performed by Askenfelt [32], a direct measurement of the actual dynamical friction forces without disturbing the string motion is quite difficult. Therefore, in this work we develop a modal-based identification technique making use of inverse methods and optimization techniques, which enables the identification of the interface force, as well as the string self-excited motion, from the dynamical reactions measured at the string end supports. The method gives convincing results using simulated data originated from nonlinear computations of a bowed string. Furthermore, in cases where the force identifications are very sensitive to errors in the transfer function modal parameters, we suggest a method to improve the modal frequencies used for the identifications. Preliminary experimental results obtained using a basic bowing device, by which the string is excited with the stick of the bow, are then presented. Our identifications, from the two dynamical string reactions, are consistent as attested by the comparison of the two available versions of the string dynamical motion and of the friction force. Furthermore, the method seems adequate to investigate the interface force for the bowed string.     

新型扭矩—轴向力传感器标定研究

扭矩—轴向力传感器是研究复合振动攻丝过程的重要装置。在振动攻丝机上安装扭矩和轴向力传感器,可以实现扭矩和轴向力的在线测量,对研究在振动攻丝过程中扭矩和轴向力的关系具有重要意义。为了研究新设计的扭矩—轴向力传感器的基本特性,选择了标定设备和标定方法对传感器进行静态标定和动态标定,得出传感器的静态特性和动态特性指标,为进一步设计和改造传感器结构提供理论依据。     

轴/径向耦合式非接触型压电作动器的研究

提出了一种基于近场声悬浮机理的球转子压电作动器,特别设计了可分别沿轴向和径向辐射超声近场的作动器,其目的是为了实现球转子的稳定、可控悬浮和高速旋转,可将其应用到航空航天的高速电机、球轴承传动或姿态传感领域。该新型压电作动器通过轴向与径向悬浮装置的不同耦合形式来提供超声悬浮力并以非接触的方式驱动球转子,实现对球转子的灵活控制。介绍了轴/径向耦合式非接触型压电作动器的结构和工作原理,通过仿真得到了悬浮装置的声场分布形式,深入分析和阐释了球转子的悬浮和驱动机制,加工了样机,搭建了轴/径向耦合式超声悬浮型压电作动器的特性测试系统,通过非接触式激光位移传感器得到了球转子的悬浮特性,并获得了691.5r/min的转速。