基于无线传感网络和超声波的室内定位系统的设计与实现

Design and implementation of an indoor localization system based on wireless sensor networks and ultrasonic

研究一种基于无线传感网络(WSN)和超声波的室内定位系统的设计与实现.该系统利用超声波在空间飞行的时间和速度,求出定位节点到各个锚节点的距离;然后利用三边测量的定位方法求出定位目标节点的坐标.这种定位系统利用包络检测方法,通过检测超声波包络的最大值点计算超声波的到达时间.考虑实际电路系统中存在噪声的情况,实际检测到的最大值点都会在真实值左右波动,从而降低了系统的稳定性和精度.针对该问题,采用数字锁相放大,通过仿真和实际应用实验与现有方法进行对比.对比结果表明,该方法能有效减少噪声和干扰的影响,极大地提高系统的定位精度和系统的抗干扰能力,在不考虑超声波反射的情况下,距离测量误差能够达到2 mm,数据的标准差最大值达到0.15 mm,相对于目前研究领域的最高值0.3 mm,降低了50%.

The design and implementation of an indoor location system based on wireless sensor networks（WSN）and ultrasonic are studied. The distance between the locating object and the anchor node is calculated using time of flight（To F） and velocity of ultrasonic. Then the trilateration localization is applied to compute coordinates. The envelope detection method is used to measure To F, which treats the highest value point of the envelope signal as the arrival time. Considering the effect of noise in the actual circuit, the measured value will fluctuate at the actual peak, it affects the stability and precision of the system. The digital lock-in amplifying technique is adopted in this paper, the result of experiment and simulation show that this method can reduce the effects of noise and interference, and improve greatly the positioning accuracy and the capacity of anti-jamming compared with the existing methods. Without considering the ultrasonic radiation, the distance measurement error is within 2 mm, and the standard deviation is less than 0.15 mm in the experiments, which is reduced about 50 % comparing with the best result achieved currently 0.3 mm.