Research Of Pedestrian Independent Positioning Technology Based On Distributed Multi-Node Micro Sensors

For the strong autonomy in the indoor environment,inertial positioning technologies based on microsensor have been research focus in the fields of academia and industry.Pedestrian Dead Reckoning(PDR)algorithms have been extensively researched and applied to inertial positioning technologies.Since the accuracy of the traditional PDR algorithm was limited by gait and step-length,and the absence of step-height,trajectories of pedestrian cannot be reckoned directly.In this thesis,a pedestrian autonomous positioning scheme based on distributed multi-node micro sensors is proposed to solve the above-mentioned problems.The distributed multi-node micro sensors have been built by analyzing motion characteristics of lower extremity for pedestrian.For three different movements,the corresponding gait detecting algorithm,estimating algorithms for step-length and step-height are proposed.By optimizing the gait,step-length parameters and adding the parameter for step-height,the PDR algorithm is improved based on distributed multi-node system,which improves the positioning accuracy of pedestrian in three-dimensional space.Firstly,subsection-rigid motion model is established by analyzing motion characteristics of lower extremity for pedestrian,and a distributed multi-node system is built based on this model.For the deterministic error and the random noise,an error compensation algorithm based on least mean square(LMS)and batch gradient descent is proposed,which effectively improves the measuring accuracy and output stability of nodes and provides a stable and reliable foundation for subsequent work.Then,for three different movements of flat-walking,upstairs and downstairs,the corresponding detecting algorithms are proposed to detect the three gait events of heel-strike,double full-support and toe-off.According to the results,the gait cycles of the three movements are obtained,and the estimating algorithms for step-lenght and step-height based on the fusing multi-node are proposed,which can optimize the step-length and realize the real-time measurement of step-height.The experimental results show that the detecting accuracy of gait events is greater than 99.65%,the relative mean error of step-length for flat-walking is 0.96%,the relative mean error of step-length and step-height for upstairs are 6.69% and 1.59%,respectively,the relative mean error of step-length and step-height for downstairs are 12.15% and 1.84%,respectively.Finally,according to the gait,step-legth and the step-height mentioned above,the improved PDR algorithm is proposed based on distributed multi-node system,and trajectories of pedestrian can be reckoned in three-dimensional space.The experimental results show that the closed-loop mean error of trajectories in the two-dimensional plane is 0.71%,and the open-loop mean error is 0.85%.In the three-dimensional space,the closed-loop mean error and the open-loop mean error of trajectories are 0.78% and 5.77%,respectively.