Design And Implementation Of Ranging System Based On Angle Compensation

With the rapid development of the IoT,more and more services are based on indoor positioning.Ranging is the basis of indoor positioning and has a significant impact on positioning accuracy.RSSI ranging technology is based on the law that the received signal strength changes with distance.However,when the wireless signal propagates in the actual environment,it is affected by the environmental interference a lot,which will result in a large ranging error.Therefore,reducing RSSI fluctuations and reducing the impact of environmental factors on RSSI are keys to indoor ranging.Aiming at the characteristics that the RSSI value in the actual environment is easily affected by the outside world,especially the influence of the antenna angle on the RSSI value,a high-precision RSSI ranging system based on the magnetometer angle compensation is designed in this paper.Firstly,a 2.4 GHz wireless communication module with a three-axis magnetometer as the ranging node device is designed in this paper.The absolute angle of the geomagnetic north can be obtained by the three-axis magnetometer node device and this angle value will be used in the following ranging algorithm to compensate the RSSI.Then,the RSSI values of different antenna angles are actually collected,and the ranging model at each angle is fitted.After comparison analysis,it is found that the RMSE of the third-order polynomial ranging model is 26.5% higher than that of the shadow logarithmic ranging model.The cubic polynomial ranging model is used as the distance measurement model of this subject,and a database corresponding to the angle and ranging model is constructed,then the ranging model is saved to the node device.Finally,in the actual ranging test,the unknown node firstly uses the mean smoothing filter to filter out the large fluctuation RSSI value,and the angled compensation is performed on the filtered RSSI value according to the angle information of the unknown node and the anchor node,and the nearest neighboring distance measuring model is selected.The improved Newton method is used to solve the ranging model to obtain the estimated distance.In general,the accuracy of the range-based ranging system based on angle compensation is 83.9% higher than that of the traditional shadow logarithmic ranging model.In this paper,the NORDIC 52832 RF chip and LIS2 MDL magnetometer are used to design a ranging system,which is used to verify the hardware platform and improved ranging algorithm within 12 meters.The experimental data shows that the average error of the ranging within the range of 12 meters is 0.745 meters and can meet the requirements of indoor position.