张武军+司峻峰+黄晓林

摘 要： 与硬币自动识别相关的硬币电磁参数称为硬币的机读特征。传统的硬币机读特征识别方法具有检测参数温飘大、一致性差、检测参数单一等缺陷。在此采用相关检测方法对硬币机读特征检测线圈的复阻抗变化进行检测，从而获得检硬币机读特征。检测系统采用DDS的正交激励信号具有波生波形良好，频率、相位和幅值稳定的有点。采用相关检测方法，电路从本质上改善了对硬币差异形成的微弱信号的捕获能力，有利于实现硬币机读特征的在线检测。利用双联对置涡流传感器能有效地克服温漂和提高信号的动态范围，每枚硬币可以检测两次，通过数据处理后可以获得更加准确的结果。结果表明该系统能够检测出微小的硬币机读特征差异，具有良好的稳定性和可重复性。

关键词： 复阻抗； 双联对置涡流传感器； 相敏检测； 硬币机读特征

中图分类号： TN919?34 文献标识码： A 文章编号： 1004?373X（2014）04?0138?05

System based on dual opposed sensor for detecting machine?readable features of coins

ZHANG Wu?jun1， SI Jun?feng2， HUANG xiao?lin2

（1. Nanjing CBPM Great Wall Financial Equipment Co.， Ltd， Nanjing 210029， China；

2. School of Electronic Science & Engineering， Nanjing University， Nanjing 210093， China ）

Abstract： Coins electromagnetic parameters related to automatic coin recognition are called coin machine readable features. Traditional method of automatic coin recognition has big defection temperature drift， poor consistency， sole detecting parameter and so on. In this paper， the method to detect complex impedance variation of coin machine readable feature detecting coil is proposed in this paper. The detecting system can generate orthogonal excitation signal， which has perfect waveform， and stable frequency， phase and amplitude. By the relevant detection method， the circuit can essentially improve the ability to capture the weak signal formed by the difference between coins. It is conducive to the realization of online detection for coin machine readable features. The system can effectively overcome the temperature drift and improve the dynamic range of signal by using dual opposed eddy current sensor. Every coin can be detected twice， thus more accurate results can be obtained by data processing. The testing results show that the system can detect the tiny difference of coin machine readable feature， and has good stability and repeatability.

Keywords： complex impedance； dual opposed eddy current sensor； phase sensitive detection； coin machine?readable feature

0 引 言

硬币作为辅币具有流通周期长，易于自动售货与找零等优点，以美国、日本和德国为代表的发达国家已基本实现辅币的硬币化。辅币的硬币化使得硬币的自动识别成为流通过程中不可缺少的一个环节。硬币识别所涉及电磁参数的规范化成为实际问题[1]。

从硬币识别分类的原理上看，当某一类硬币被用于识别的电磁参数的一致性越好，与其他硬币电磁特征上的差异越大，这类硬币就也容易被识别。电磁特征越不容易被复制，这类硬币的防伪特征就越好。……