基于EC-TDOA和ZigBee技术的室内超声波定位系统

目的研究室内定位方法机理，解决室内目标高精度定位的问题．方法设计了一种基于测距的室内定位系统，该系统采用测量射频信号和超声波信号到达时间差的方法测距并引入校正因子减小测距误差，通过极大似然估计定位方法计算目标位置，运用ZigBee制作节点模块组成网络实现对室内目标的定位．结果在测距实验中，EC-TDOA测距结果的误差小于0．02cm，满足测距精度要求．在定位实验中，最大定位误差和平均定位误差分别为4．3cm和1．64cm，而定位误差在2．5cm以内的比例达到90％．定位频率为20Hz，满足实时定位的要求．结论系统在室内环境中实现对超声波信号覆盖范围内移动节点的定位，通过测距校正有效提高定位精度．系统具有较强的容错性和自适应性．

Precise Ultrasonic Indoor EC-TDOA and Positioning System Based on ZigBee Technology

Aiming at the need of indoor positioning, the existing theories of indoor positioning is studied and the problem of high precision positioning of indoor target is being solved. This paper designs a range-based indoor positioning system. The measurement method based on time difference of RF signal and the ultrasonic signal arrival is used to measure the distance. Correction factors are introduced to reduce the ranging error. Maximum Likelihood Estimation positioning algorithm is applied to calculate the position of targets. The indoor position is achieved by means of ZigBee network node modules. In ranging experiments, EC- TDOA ranging error is less than 0.02 cm, meeting ranging accuracy demand. In positioning experiments, the maximum positioning error and the average positioning error are 4.3 cm and l. 64 cm respectively, and the proportion of the positioning error within 2. 5 cm reaches 90%. Positioning frequency is 20 Hz, satisfying the requirements of real-time positioning. The system can locate mobile nodes in coverage of the ultrasonic signal in indoor environment, and the positioning accuracy is improved effectively by a distance correction. The system possesses strong fault tolerance and adaptability.