Research On Outdoor/indoor Continuous Positioning System Based On Multi-sensor Fusion

Many traffic occasions such as tunnel,subway station and underground parking require accurate and continuous positioning.Despite the broad range of positioning,navigation and timing services offered by the Global Positioning System(GPS),its signals are vulnerable to interference,leading to a degraded performance or even unavailability.Inertial Navigation System(INS)is an autonomous navigation method that is immune to outside interference.The trajectory estimation is mainly performed by the motion data of inertial sensors such as an accelerometer and a gyroscope.This method is very accurate in the short term,but its error accumulates over time.The magnetometer + Inertial Measurement Unit(IMU)combination is one of the commonly used indoor positioning methods.The direction provided by the magnetometer effectively corrects the error of inertial navigation.However,magnetometers are susceptible to interference from the surrounding environment,resulting in severely reduced accuracy.The methods of outdoor positioning and indoor positioning have been improved and innovated.This paper takes GPS receiver,magnetometer and IMU as research objects.The methods of accuracy error in outdoor positioning and indoor positioning have been improved and innovated,respectively.An embedded mobile platform was proposed to achieve precise positioning in continuous indoor and outdoor scenes.The main research results are as follows:(1)In order to reduce noise in the GPS signal,an effective method is to use Kalman filtering based on the integration of GPS receiver and IMU.The combined value of the GPS receiver and the IMU is taken as the observation value,and the positioning prediction is performed based on the theoretical value in the motion model.The results show that the error between the overall positioning trajectory and the real trajectory is within 3 meters.(2)For the magnetometer to be susceptible to environmental interference,this paper analyzes the error in the process of collecting data,and proposes a method to calculate the heading angle using a magnetometer.The method can dynamically calculate and correct the heading angle of the mobile platform in the working environment.The results show that the proposed method of calculating heading angle by magnetometer can better resist interference.Compared with the uncorrected heading angle,the corrected results can be improved 60% accuracy,and the effect is more obvious when the interference is larger.(3)A mobile terminal platform was built for the outdoor/indoor positioning needs.It contains a GPS receiver,a magnetometer and an IMU.It uses GPS and INS for positioning outdoors.When entering indoors,the positioning is updated by the heading angle and acceleration which provided by the magnetometer and the IMU respectively.In addition,during the work process,the processor needs to process the large amount of data obtained from these sensors.The platform hardware adopts ARM+DSP dual-core processor.An embedded Linux operating system is established on the ARM part.It controls procedure and obtains the related data.The DSP part is responsible for the data filtering and positioning algorithm.The results show that the system has a good performance in terms of control and stability.