Attitude estimation for pedestrian navigation using low cost mems accelerometer in mobile applications, and processing methods, apparatus and systems

Abstract

A user-heading determining system ( 10 ) for pedestrian use includes a multiple-axis accelerometer ( 110 ) having acceleration sensors; a device-heading sensor circuit ( 115 ) physically situated in a fixed relationship to the accelerometer ( 110 ); an electronic circuit ( 100 ) operable to generate signals representing components of acceleration sensed by the accelerometer ( 110 ) sensors, and to electronically process at least some part of the signals to produce an estimation of attitude of a user motion with respect to the accelerometer, and further to combine the attitude estimation ( 750 , α) with a device heading estimation ( 770 , Ψ) responsive to the device-heading sensor circuit, to produce a user heading estimation ( 780 ); and an electronic display ( 190 ) responsive to the electronic circuit ( 100 ) to display information at least in part based on the user heading estimation. Other systems, circuits and processes are also disclosed.

What is claimed is: 
     
         1 . A process responsive to an accelerometer and a device-heading sensor unit, the process comprising:
 generating signals representing components of acceleration acquired from the accelerometer;   electronically processing at least some part of the signals to produce walking step signals and an estimation of attitude of a user motion with respect to the accelerometer, and further to combine the attitude estimation with a device heading estimation responsive to the device-heading sensor unit, to produce a user heading estimation; and   portably displaying a visual path of walking jointly based on the walking step signals, attitude estimation and device heading estimation.   
     
     
         2 . The process claimed in  claim 1  including:
 electronically rotating through various rotations the at least part of the signals, 
 estimating a parameter of the signals related to variance, and 
 estimating a vertical direction and a lateral user direction where the parameter is substantially maximum and where it is substantially minimum respectively. 
 
     
     
         3 . The process claimed in  claim 2  in which the estimation of attitude is based on estimating direction of user motion substantially perpendicular to both the aforethe vertical direction and lateral user direction. 
     
     
         4 . The process claimed in  claim 2  in which the processing includes executing a vector-average on the at least part of the signals whereby to determine a direction related to gravity, and using such determination to resolve an up/down sense of the vertical direction. 
     
     
         5 . The process claimed in  claim 2  including detecting a sense of a leading or lagging relation between acceleration in the vertical direction and acceleration in a forward direction, and resolving whether the user motion is forward or backward using the detected sense of the relation. 
     
     
         6 . The process claimed in  claim 2  including monitoring for a phase difference between acceleration in the vertical direction and acceleration in a forward direction, and processing in different motion monitoring modes depending on the comparison. 
     
     
         7 . The process claimed in  claim 1  in which the processing includes vector-averaging on the at least part of the signals to estimate a direction related to gravity. 
     
     
         8 . The process claimed in  claim 7  in which the processing includes:
 electronically searching in a horizontal plane substantially perpendicular to the estimated direction related to gravity, 
 rotating the at least part of the signals and estimating a parameter related to variance, and 
 generating a forward direction of user motion at the rotation direction where such parameter corresponds to a maximum variance. 
 
     
     
         9 . The process claimed in  claim 8  in which the processing includes estimating the attitude by electronically deriving an angle in the horizontal plane between the forward direction and a sensor axis direction in the horizontal plane. 
     
     
         10 . The process claimed in  claim 1  in which the processing includes filtering the respective acceleration component signals prior to the attitude estimating using a filtering selected from the group consisting of: 1) sliding window correlating, 2) integrating, 3) bandpass filtering passing human motion frequencies, 4) polynomial filtering smoothing human motion frequencies. 
     
     
         11 . The system claimed in  claim 1  in which the processing includes electronically estimating a direction related to gravity and electronically executing a search in a plane substantially perpendicular to the estimated direction related to gravity, rotating the at least part of the signals and estimating a parameter related to variance, and determining a particular direction of motion with respect to the accelerometer as a direction along which such parameter is minimized. 
     
     
         12 . The system claimed in  claim 11  in which the processing includes electronically estimating the attitude using that direction along which the parameter is minimized.