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Demodulation of acoustic telemetry binary phase shift keying signal based on high-order Duffing system

Chinese Physics B 2016年第10期25卷 69-75页

作者：燕并男刘崇新倪骏康赵亮 School of Electrical Engineering Xi'an Jiaotong University College of Electrical Engineering School of Xi'an Shiyou University Xi'an Thermal Power Research Institute Co.Ltd

In order to grasp the downhole situation immediately, logging while drilling(LWD) technology is adopted. One of the LWD technologies, called acoustic telemetry, can be successfully applied to modern drilling. It is critical for acoustic telemetry technology that the signal is successfully transmitted to the ground. In this paper, binary phase shift keying(BPSK) is used to modulate carrier waves for the transmission and a new BPSK demodulation scheme based on Duffing chaos is investigated. Firstly, a high-order system is given in order to enhance the signal detection capability and it is realized through building a virtual circuit using an electronic workbench(EWB). Secondly, a new BPSK demodulation scheme is proposed based on the intermittent chaos phenomena of the new Duffing system. Finally, a system variable crossing zero-point equidistance method is proposed to obtain the phase difference between the system and the BPSK signal. Then it is determined that the digital signal transmitted from the bottom of the well is ‘0’ or ‘1’. The simulation results show that the demodulation method is feasible.

关键词： acoustic telemetry BPSK demodulation Duffing system

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Seasonal movements of American horseshoe crabs Limulus polyphemus in the Great Bay Estuary,New Hampshire (USA)

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Current Zoology 2010年第5期56卷 587-598页

作者： Susanne Y SCHALLER Christopher C.CHABOT Winsor H.WATSON Ⅲ Department of Biological Sciences University of New Hampshire Department of Biology Plymouth State University

The goal of this study was to determine the year round movement patterns of American horseshoe crabs, Limulus polyphemus, in the Great Bay Estuary, New Hampshire （USA） by using acoustic telemetry to track the movements of 37 adult Limulus, for periods ranging from 2 to 31 months. During the winter （December-March） horseshoe crabs moved very little. In the spring, when water temperatures exceeded II^C, horseshoe crabs moved at least 1 km further up into the estuary to shallower subtidal areas about a month prior to spawning. The mean distance traveled during spring migrations was 2.6 ＋ 0.5 （n=20） km up the estuary. Mating occurred in May and June and during these months animals spent most of their time in shallow subtidal areas adjacent to mating beaches. In the summer （July-Augnst）, animals moved 1.5 ± 0.5 （n=26） km down the estuary, towards the ocean, and ranged widely, using extensive portions of the estuary. In the fall （September-November） movement was more limited （0.5 ± 0.5 km; n = 24） while animals settled into wintering locations, where they remained until spring. The mean annual linear range for all animals was 4.5 ± 0.3 km （n =35） and the maximum distance traveled by an individual horseshoe crab within one year was 9.2 km. There was no evidence that any of the horseshoe crabs tracked during this study left the estuary

关键词： Limuluspolyphemus acoustic telemetry Horseshoe crab Tracking Estuary Home range

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Improved Methods for acoustic Transmission along the Drill String and Other Periodic Media

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稀有金属材料与工程 2006年第A3期35卷 495-498页

作者： Cheng Li Tianhuai Ding Dept. of Precision Instruments and Mechanology Tsinghua University Beijing 100084 China

acoustic telemetry along the drill string helps to know the physical and chemical characteristics of the formation and drilling fluid.A time-domain algorithm is developed for the propagation of one-dimensional axial stress waves with the inner and outer viscous *** algorithm simulates the passbands,stopbands and spikes due to the presence of the discontinuous boundaries of drill *** the effects of transmitted pulses and transceivers on acoustic transmission are *** simulated results show that the raised cosine pulses and optimal placements of transceivers improve system ***,dual PZT receivers can exclude signals propagating in a direction opposite to the transmitted signals. It is obvious that the uses of the available modeling and signal processing techniques can make the drill string as a waveguide for transmitting information at high data rates.

关键词： formation characteristics drill string acoustic telemetry well logging signal processing

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Study and simulation on the characteristics of drill string channel for acoustic waves

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Journal of Energy and Power Engineering 2007年第1期1卷 41-48,62页

作者： GAO De-li WANG De-gui LI Cheng China University of Petroleum-Beijing Beijing 102249 China Tsinghua University Beijing 100084 China

Traditional wireless MWD telemetry systems such as mud pulse and electromagnetic telemetry are limited due to low carrier frequencies. The first acoustic telemetry system was studied as part of a drill stem testing system in 2000, but there are some problems limited it to using for information transmission in drilling. In the paper, we study and simulation on the drill string channel characteristics. Based on the transmission equation of longitudinal wave in periodic drill string channel, we get a geometrical model for drill string channel. Two aspects are studied. Firstly, the equation for dispersion is established analyze and simulate the influence of length and cross-section to dispersion. Secondly, we introduce finite-difference for analyzing of transient response. Simulate transient response of drill string channel by changing the geometrical-characters of drill string. The paper gets characteristics of channel dispersion and signal attenuation, and useful for the choosing of best passband for carrier frequency. It is valuable for the acoustic telemetry to use for drilling applications.

关键词： acoustic telemetry longitudinal wave dispersion finite-difference transient response

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