Method and system for combining sensor data

Abstract

A method and system for combining data obtained by sensors, having particular application in the field of navigation systems, are disclosed. The techniques provide significant improvement over state-of-the-art Markovian methods that use statistical noise filters such as Kalman filters to filter data by comparing instantaneous data with the corresponding instantaneous estimates from a model. In contrast, the techniques disclosed herein use multiple time periods of various lengths to process multiple sensor data streams, in order to combine sensor measurements with motion models at a given time epoch with greater confidence and accuracy than is possible with traditional “single epoch” methods. The techniques provide particular benefit when the first and/or second sensors are low-cost sensors (for example as seen in smart phones) which are typically of low quality and have large inherent biases.

1 . A method of computing a navigation solution comprising:
 receiving data from a first sensor over a first time period and data from a second sensor over a second time period;   determining at least one zero velocity period within the first sensor data and/or second sensor data;   analyzing the first sensor data and/or second sensor data during the at least one zero velocity period;   altering first sensor data and/or second sensor data that violates the at least one zero velocity period to produce corrected first sensor data and/or corrected second sensor data; and   compute a navigation solution at a time instant within the first and second time periods using the corrected first sensor data and/or corrected second sensor data.   
     
     
         2 . The method of  claim 1  further comprising creating a motion model using the GNSS data and/or IMU data. 
     
     
         3 . The method of  claim 2  further comprising correcting the motion model using the corrected GNSS data and/or the corrected IMU data. 
     
     
         4 . The method of  claim 1  wherein a duration of the first time period is equal to or is different from a duration of the second time period. 
     
     
         5 . The method of  claim 1  wherein a duration of the first time period overlaps a duration of the second time period. 
     
     
         6 . The method of  claim 1  wherein altering comprises resetting velocity measurements to zero within the GNSS data during the at least one zero velocity period. 
     
     
         7 . The method of  claim 1  wherein altering comprises determining biases of one or more IMU sensors of the IMU during the at least one zero velocity period and altering the IMU data using the determined biases. 
     
     
         8 . The method of  claim 1  wherein the first and second time periods extend into the future and the past with respect to the time instant. 
     
     
         9 . The method of  claim 1  wherein the corrected GNSS and/or corrected IMU data is used to constrain the navigation solution. 
     
     
         10 . A method of  claim 1  wherein the first sensor is a GNSS receiver and the second sensor is an inertial measurement unit (IMU). 
     
     
         11 . A method of computing a navigation solution comprising:
 receiving global navigation satellite system (GNSS) data over a first time period and inertial measurement unit (IMU) data over a second time period;   determining at least one zero velocity period within the GNSS data and IMU data;   analyzing the first sensor data and/or second sensor data during the at least one zero velocity period;   altering GNSS data and IMU data that violates the at least one zero velocity period to produce corrected GNSS data and corrected IMU data; and   compute a navigation solution at a time instant within the first and second time periods using the corrected GNSS data and corrected IMU data.   
     
     
         12 . The method of  claim 11  further comprising creating a motion model using the GNSS data and IMU data. 
     
     
         13 . The method of  claim 12  further comprising correcting the motion model using the corrected GNSS data and the corrected IMU data. 
     
     
         14 . The method of  claim 11  wherein a duration of the first time period is equal to or different from a duration of the second time period. 
     
     
         15 . The method of  claim 11  wherein a duration of the first time period overlaps a duration of the second time period. 
     
     
         16 . The method of  claim 11  wherein altering comprises resetting velocity measurements to zero within the GNSS data during the at least one zero velocity period. 
     
     
         17 . The method of  claim 11  wherein altering comprises determining biases of one or more IMU sensors of the IMU during the at least one zero velocity periods and altering the IMU data using the determined biases. 
     
     
         18 . The method of  claim 11  wherein the first and second time periods extend into the future and the past with respect to the time instant. 
     
     
         19 . The method of  claim 11  wherein the corrected GNSS and corrected IMU data is used to constrain the navigation solution.