优化伪随机脉冲位置调制序列激励的无串扰超声测距系统

Noncrosstalk Ultrasonic Range System with Optimized Pseudorandom Pulse Position Modulation (PPPM) Sequence Excitation

超声测距系统中多路换能器同时工作存在的串扰会导致错误的距离测量和降低系统的工作效率。为消除此串扰,提出了伪随机脉冲位置调制(PPPM)法用于构造超声发射序列。PPPM序列中脉宽固定,脉冲位置由伪随机数序列调制。为获得尖锐的自相关函数和平坦的互相关函数,对四种常用的同余法产生的伪随机数进行了定量检验,并选定统计特性最好的乘加同余法用于构造PPPM序列。为提高超声测距系统实时性,采用遗传算法优化较短的PPPM序列中脉冲之间的间隔范围。将所提方法用于多路Polaroid600系列静电型换能器构成的超声测距系统,实验验证了所提方法的可行性。

Crosstalk among multiple transducers working together can result in false distance measurement and decrease the work efficiency of ultrasonic range system. To eliminate the ultrasonic crosstalk, Pseudorandom Pulse Position Modulation （PPPM） method is proposed to construct ultrasonic transmission sequence. The pulse width in PPPM sequence is fixed, while the pulse position is modulated using pseudorandom numbers. To obtain sharp autocorrelation functions and flat cross-correlation functions, four commonly used congruence methods are quantitatively analyzed, and the multiplicative-additional congruential method, for its best statistic characteristics, is chosen for the PPPM sequences. A genetic algorithm is adopted to optimize the duration range between pulses in PPPM sequence in order to enhance the real-time performance of the ultrasonic range system. Experiments using Polaroid 600 series electrostatic transducers validate the feasibility of the proposed method.