A Pedestrian Dead Reckoning System Based On Integrated Navigation For The Elderly In Indoors

The elderly are prone to falling and getting lost,especially in unknown buildings.If no one else can ask for help,it may have serious consequences.Based on this,the paper studies a dead reckoning system for the elderly.It could realize the positioning of the elderly in real-time.GPS is unavailable in indoors.Due to the effect of shielding,the positioning errors are very big.And it is unable to get where the elderly are.The objective of this paper is to propose a trajectory estimation system for the elderly in indoors.And it is an integrated na'vigation system without external information.Not only is it low cost,it's also easy to wear.The estimation methods of step detection,step length and heading direction are researched.The output of gyro can calculate attitude angle,but the drift error will increase with time.In this work,a complementary filtering algorithm is proposed,which combines magnetometer,accelerometer and gyroscope to estimate attitude angle.In the case of magnetic field interference,an algorithm is proposed,which can improve attitude angle accuracy.A threshold is set to rule out false positives,and the threshold value depends on the acceleration.This method is suitable for walking,running,going upstairs and downstairs.The step length estimation algorithm is part of a pedestrian dead reckoning system.In the study,the elderly's step length depends on their height.The PDR algorithm can only estimate the elderly position in two-dimensional space.In order to estimate the elderly position in three dimensions,it is necessary to combine barometer data.Finally,the heading angle,steps and floor information are sent to the smart phone via WIFI.The real-time positioning and tracking are displayed on the mobile phone.In this work,the selection of hardware module and the algorithm programming of the system are finished.The test device is installed in front of the waist of the elderly.Experiments have been carried out to test this system.And the results show that the system can complete the following functions such as heading angle estimation,step detection,_step estimation and floor judgment.According to the experiment results,the system can achieve 5.78%of heading angle error,-3.13%of positioning error and 0.94%of height error in indoors.The PDR system is able to estimate the pedestrian position accurately in the environment of flat and upstairs.And the accuracy of the system is acceptable in measuring displacement of the elderly.