脉冲编码激励超声扩频测距系统性能分析
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摘要
多路超声测距系统中主要存在两个问题,一是超声串扰,二是有效测距范围与测距分辨率的矛盾。为解决这两个问题,将扩频技术与编码应用到超声测距领域,在超声测距系统的发射端使用合适的扩频编码序列激励换能器,在接收端对回声信号进行相关运算以捕获渡越时间。每个超声换能器的激励序列所包含的编码信息都是唯一的,因此超声测距系统可以识别出所接收到的回声信号是哪个超声换能器发出的,从而有效的消除超声串扰。扩频测距方法的应用使得超声测距系统既可以获得较大的测距范围,又可保持较高的距离分辨率。
本文基于超声扩频编码测距原理,选择了适用于超声测距系统的6种伪随机二进制编码:m序列,混沌序列,Gold序列,Balanced Gold序列,Legendre序列和Hall序列。介绍每种编码的定义,简要分析各自的特性,并给出了具体的序列产生方法。
将这6种编码与3种常用的二值数字调制方式,即二值幅移键控(BASK)、二值频移键控(BFSK)和二值相移键控(BPSK)相结合,构造了18种(每种含8个)脉冲编码数字调制激励序列。为了评价这18种激励序列在超声测距应用中性能的优劣,合理设置了3个有效的评价指标,即回声序列相关度、激励序列与回声序列的能量/能量效率和回声序列相关函数的主瓣宽度。
基于所构造的18种激励序列,首先进行了超声测距仿真研究,并对仿真结果在上述3个评价指标方面的性能进行了合理的分析;接着设计了超声信号发射接收模块和电源模块,优化了超声测距系统,并在此基础上进行了真实的超声测距系统性能分析实验;最后将实验结果与仿真研究的分析结果进行对比验证,提出了适用于扩频超声测距系统的编码种类和调制方式。
There exist two major problems in a multi-channel ultrasonic ranging system, one is the crosstalk phenomenon, and the other is contradiction between effective ranging distance and ranging resolution. To solve the two problems, spread-spectrum technology and coding method are applied to the ultrasonic ranging field. The pulse-code-modulation sequences are used to drive the ultrasonic transmitting device and the correlation method is adopted to calculate the TOF (time of flight) at the receiving end. Since the information encoded in the excitation sequence is unique for each transducer, the multi-channel ultrasonic ranging system can identify the source transducer of the echo sequence and the crosstalk phenomenon can be eliminated then. The spread-spectrum technology can enable the ultrasonic ranging system to own a longer effective ranging distance using long excitation sequences and to improve the ranging resolution.
Based on ultrasonic spread spectrum coding ranging theory, six kinds of pseudo-random binary codes, i.e., m sequence, chaos sequence, Gold sequence, balanced Gold sequence, Legendre sequence and Hall sequence, are chosen for the multi-channel ultrasonic ranging system. Their definitions are introduced, the characteristics are analyzed briefly and the concrete generation procedures are presented.
The six kinds of codes combined with three types of binary modulation technique, i.e., BASK (binary amplitude shift keying), BFSK (binary frequency shift keying) and BPSK (binary phase shift keying), are used to construct eighteen kinds (each kind includes eight different sequences) of pulse-coded digital-modulation excitation sequences. Three indexes, which are correlation degree of echo sequences, energy/energy efficiency of excitation and echo sequences, and main-lobe width of correlation function, are set to evaluate the performances of each excitation sequence.
On basis of the eighteen kinds of excitation sequences, further research work has been done. Firstly, the simulation experiments are performed and the results are analyzed using the three evaluation indexes. Secondly, the ultrasonic transmitting-receiving circuit and the power module are designed to improve the structure of the ultrasonic ranging system, and ultrasonic ranging experiments are performed on this platform. Finally, analysis results of the real experiments are compared with those of the simulation experiments, and the suitable codes and modulation modes are proposed for ultrasonic spread-spectrum ranging systems.
本文基于超声扩频编码测距原理,选择了适用于超声测距系统的6种伪随机二进制编码:m序列,混沌序列,Gold序列,Balanced Gold序列,Legendre序列和Hall序列。介绍每种编码的定义,简要分析各自的特性,并给出了具体的序列产生方法。
将这6种编码与3种常用的二值数字调制方式,即二值幅移键控(BASK)、二值频移键控(BFSK)和二值相移键控(BPSK)相结合,构造了18种(每种含8个)脉冲编码数字调制激励序列。为了评价这18种激励序列在超声测距应用中性能的优劣,合理设置了3个有效的评价指标,即回声序列相关度、激励序列与回声序列的能量/能量效率和回声序列相关函数的主瓣宽度。
基于所构造的18种激励序列,首先进行了超声测距仿真研究,并对仿真结果在上述3个评价指标方面的性能进行了合理的分析;接着设计了超声信号发射接收模块和电源模块,优化了超声测距系统,并在此基础上进行了真实的超声测距系统性能分析实验;最后将实验结果与仿真研究的分析结果进行对比验证,提出了适用于扩频超声测距系统的编码种类和调制方式。
There exist two major problems in a multi-channel ultrasonic ranging system, one is the crosstalk phenomenon, and the other is contradiction between effective ranging distance and ranging resolution. To solve the two problems, spread-spectrum technology and coding method are applied to the ultrasonic ranging field. The pulse-code-modulation sequences are used to drive the ultrasonic transmitting device and the correlation method is adopted to calculate the TOF (time of flight) at the receiving end. Since the information encoded in the excitation sequence is unique for each transducer, the multi-channel ultrasonic ranging system can identify the source transducer of the echo sequence and the crosstalk phenomenon can be eliminated then. The spread-spectrum technology can enable the ultrasonic ranging system to own a longer effective ranging distance using long excitation sequences and to improve the ranging resolution.
Based on ultrasonic spread spectrum coding ranging theory, six kinds of pseudo-random binary codes, i.e., m sequence, chaos sequence, Gold sequence, balanced Gold sequence, Legendre sequence and Hall sequence, are chosen for the multi-channel ultrasonic ranging system. Their definitions are introduced, the characteristics are analyzed briefly and the concrete generation procedures are presented.
The six kinds of codes combined with three types of binary modulation technique, i.e., BASK (binary amplitude shift keying), BFSK (binary frequency shift keying) and BPSK (binary phase shift keying), are used to construct eighteen kinds (each kind includes eight different sequences) of pulse-coded digital-modulation excitation sequences. Three indexes, which are correlation degree of echo sequences, energy/energy efficiency of excitation and echo sequences, and main-lobe width of correlation function, are set to evaluate the performances of each excitation sequence.
On basis of the eighteen kinds of excitation sequences, further research work has been done. Firstly, the simulation experiments are performed and the results are analyzed using the three evaluation indexes. Secondly, the ultrasonic transmitting-receiving circuit and the power module are designed to improve the structure of the ultrasonic ranging system, and ultrasonic ranging experiments are performed on this platform. Finally, analysis results of the real experiments are compared with those of the simulation experiments, and the suitable codes and modulation modes are proposed for ultrasonic spread-spectrum ranging systems.
引文
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[2] S. A. Kick, J. A. Simmons, Automatic gain control in the bat's sonar receiver and the neuroethology of echolocation, The Journal of neuroscience, 1984, 4(11): 2725~2737
[3]李茂山,超声波测距原理及实践技术,实用测试技术,1994, 1(12): 12~20
[4] W. W. L. Au, K. J. Benoit-Bird, Automatic gain control in the echolocation system of dolphins, Nature, 2003, 423(19): 861~863
[5]时振栋,黎安尧,王晦光,电磁波的应用,北京:高等教育出版社,1990
[6]程晓畅,王跃科,伪随机码超声扩频测距发射与接收电路设计,声学与电子工程,2007, (1): 42~45
[7] J. Borenstein, Y. Koren, Error eliminating rapid ultrasonic firing for mobile robot obstacle avoidance, Robotics and Automation, IEEE Transactions on, 1995, 11(1): 132~138
[8] K. W. J?rg, M. Berg, Sophisticated mobile robot sonar sensing with pseudo-random codes, Robotics and Autonomous Systems, 1998, 25(3~4): 241~251
[9]滕艳菲,陈尚松,超声波测距精度的研究,国外电子测量技术,2006, 25(2): 23~25
[10]赵广涛,程荫杭,基于超声波传感器的测距系统设计,传感器与仪器仪表,2006, 22(1-1): 129~131
[11]杨俊,邢克飞,杨波,基于FPGA的扩频测距快速捕获方法研究,电子器件,2003, 26(4): 406~409
[12] S. Shoval, J. Borenstein, Using coded signals to benefit from ultrasonic sensor crosstalk in mobile robot obstacle avoidance, Robotics and Automation, 2001(3), 2879~2884
[13] C. M. Elias, An ultrasonic pseudorandom signal correlation system, IEEE Transactions on Sonics and Ultrasonics, 1980, 27(1): 1~7
[14] S. Ohyama, H. Iwasawa, S. I. Ko, et al., 3D attitude measurement by means of spread spectrum modulated ultrasonic wave, SICE-ICASE International Joint Conference, 2007, 28(4), 2802 ~ 2807
[15]á. Hernández, J. Ure?a, D. Hernanz, et al, Real-time implementation of an efficient Golay correlator (EGC) applied to ultrasonic sensorial systems, Microprocessors and Microsystems, 2003, 27(8): 397~406
[16] A. Hernandez, J. Urena, J. J. Garcia, et al, Ultrasonic ranging sensor using simultaneous emissions from different transducers, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control, 2004, 51(12): 1660~1670
[17]程晓畅,苏绍景,王跃科,伪随机码超声扩频测距系统设计与算法,测试技术学报,2007, 21(1): 79~83
[18] F. Alvarez, J. Urena, M. Mazo, et al, Complementary sets of sequences-based coding for ultrasonic array sensor, 2004 IEEE Sensor Array and Multichannel Signal Processing Workshop, 2004, 211~215.
[19] C. De Marziani, J. Urena, A. Hernandez, et al, Modular Architecture for Efficient Generation and Correlation of Complementary Set of Sequences, Signal Processing, IEEE Transactions on Signal Processing, 2007, 55(5): 2323~2337
[20] Z. X. Ding, P. A. Payne, A new Golay code system for ultrasonic pulse echo measurements, Measurement Science and Technology, 1990, 1(2): 158~165
[21] V. Diaz, J. Urena, M. Mazo, et al., Using Golay complementary sequences for multi-mode ultrasonic operation, Emerging Technologies and Factory Automation, 1999, (1), 599~604
[22] A. Hernandez, J. Urena, M. Mazo, et al., Reduction of blind zone in ultrasonic transmitter/receiver transducers, Sensors and Actuators, 2007, 133(1): 96~103
[23]姚凤娟,基于混沌脉冲序列宽度调制的超声串扰抑制方法研究,[硕士学位论文],天津:天津大学,2007
[24]梁琼,用于消除超声串扰的编码与调制方法研究,[硕士学位论文],天津:天津大学,2007
[25]姚振静,超声扩频测距脉冲编码激励与渡越时间估计,[硕士学位论文],天津:天津大学,2010
[26]兰少莹,无串扰超声测距系统编码激励与回波处理,[硕士学位论文],天津:天津大学,2008
[27]时德钢,刘晔,超声波测距仪的研究,计算机测量与控制,2002, 10(7): 480~482
[28]姜道连,宁延一,用AT89C2051设计超声波测距仪,国外电子元器件,2000, (12): 31~34
[29]冯红亮,肖定国,徐春广,脉冲超声传感器激发/接收电路设计,仪表技术与传感器,2003, 11
[30]彭涵阳,无串扰超声测距系统的激励方法及基于FPGA的设计与实现,[硕士学位论文],天津:天津大学,2010
[31]林圃,无串扰超声测距系统硬件电路设计与建模,[硕士学位论文],天津:天津大学,2008
[32]李根旺,无串扰超声测距系统硬件设计与激励方法,[硕士学位论文],天津:天津大学,2009
[33]戚征,伪随机序列,数学的实践与认识,1972, (4): 26~45
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