DYNAMIC OFFSET CALIBRATION

• US 20130218505A1
• Filed: 02/05/2013
• Published: 08/22/2013
• Est. Priority Date: 02/07/2012
• Status: Active Grant

• Current Assignee: Movella Incorporated (Movella Holdings, Inc.)
• Original Assignee: mCube, Inc.
• Inventors: Bhandari, Sanjay, Kelly, Joe
• Granted Patent: US 10,324,108 B2
• Time in Patent Office: Days
• US Class Current: 702/104
• CPC Class Codes: G01C 21/08 involving use of the magnetic field of the earth
• CPC Class Codes: G01C 21/10 by using measurements of speed or acceleration G01C21/24, G01C21/26 take precedence
• CPC Class Codes: G01C 25/005 initial alignment, calibration or starting-up of inertial devices
• CPC Class Codes: G01P 15/135 by making use of contacts which are actuated by a movable inertial mass
• CPC Class Codes: G01P 15/14 by making use of gyroscopes gyroscopes per se G01C19/00
• CPC Class Codes: G01P 15/18 in two or more dimensions
• CPC Class Codes: G01P 21/00 Testing or calibrating of apparatus or devices covered by the preceding groups

Abstract

A hand-held processor system for processing data from an integrated MEMS device disposed within a hand-held computer system and method. A dynamic offset correction (DOC) process computes 3-axis accelerometer biases without needing to know the orientation of the device. Arbitrary output biases can be corrected to ensure consistent performance A system of linear equations is formed using basic observations of gravity measurements by an acceleration measuring device, conditioned upon constraints in data quality, degree of sensed motion, duration, and time separation. This system of equations is modified and solved when appropriate geometric diversity conditions are met.

Claims

1. A micro-processor, on-chip logic, or software implemented method for processing data from an integrated MEMS device disposed within a hand-held computer system programmed to perform the method, the method comprising:

sensing, by the MEMS sensor disposed within the computer system, calibration data measurements; and

determining, with a processor disposed within the computer system, computed offset data for the MEMS sensor through a dynamic offset correction (DOC) process using the calibration data measurements.

2. The method of claim 1 wherein the sensing of the calibration data measurements comprises sensing X, Y, and Z axis sensor data in one or more static orientations for a predetermined time period;

wherein the calibration data measurements includes a plurality of valid data points, and wherein the DOC process comprises building an N×

3 matrix including the plurality of valid data points and using an Ordinary Least Squares method.

3. The method of claim 1 wherein the calibration data measurements includes at least four desired data points, and wherein the DOC process comprises building a 3×

3 matrix including the at least four desired data points.

4. The method of claim 1 wherein the DOC process is initiated by a user performing a predetermined maneuver with the hand-held computer system;

wherein the predetermined maneuver comprises a motion of the user retrieving the hand-held computer system from a first user position, holding the computer system at a second user position, holding the computer system at a third and then fourth user position.

5. The method of claim 1 wherein the DOC process is configured as a background DOC process that constantly runs until predetermined calibration conditions are met;

wherein the predetermined calibration conditions include time period conditions, stationary conditions, geometric diversity conditions, or data limit conditions.

6. The method of claim 5 wherein the conditions of time period, stationary conditions, geometric diversity conditions, or data limit conditions are modified over time to improve accuracy after an initial period of convergence or completion using less stringent conditions.

7. The method of claim 1 further comprising a user-initiated calibration process including sensing, by the MEMS sensor, user-initiated calibration data measurements as the user places the hand-held computer system on a level surface and presses a button, or as the user performs a figure 8 maneuver, and determining, by the processor, user-initiated computed offset data using the user-initiated calibration data measurements.

8. The method of claim 1 wherein the MEMS sensor comprises a MEMS accelerometer and the integrated MEMS device comprises an integrated 3-axis MEMS accelerometer, or a 6-axis MEMS inertial sensing device including the MEMS accelerometer and a MEMS gyroscope, or 6-axis device including the MEMS accelerometer and a MEMS magnetometer.

9. A hand-held inertial sensor system for processing data from an integrated MEMS device disposed within the hand-held inertial sensor system, the system comprising:

a housing;

a tangible memory for storing a plurality of executable instructions;

an integrated MEMS device disposed within the housing, the integrated MEMS device including a MEMS sensor;

a processor disposed within the housing and coupled to the tangible memory and the integrated MEMS device, wherein the processor is programmed to perform a plurality of functions by the plurality of executable instructions;

wherein the plurality of executable instructions comprise;

executable code that programs the processor to sense, by the MEMS sensor disposed within the computer system, calibration data measurements; and

executable code that programs the processor to determine, with a processor disposed within the computer system, computed offset data for the MEMS sensor through a dynamic offset correction (DOC) process using the calibration data measurements.

10. The system of claim 9 wherein the executable code that programs the processor to sense calibration data measurements comprises:

executable code that programs the processor to sense, by the MEMS sensor, X, Y, and Z axis sensor data in at least four static orientations for a predetermined time period.

11. The system of claim 9 wherein the executable code that programs the processor to sense, by the MEMS sensor, the calibration data measurements comprises:

executable code that programs the processor to sense, by the MEMS sensor, a plurality of valid data points,

and wherein the executable code that programs the processor to determine the computed offset data comprises;

executable code that programs the processor to perform the DOC process, wherein the DOC process comprises building an N×

3 matrix including the plurality of valid data points and using an Ordinary Least Squares method.

12. The system of claim 9 wherein the executable code that programs the processor to sense, by the MEMS sensor, the calibration data measurements comprises:

executable code that programs the processor to sense, by the MEMS sensor, at least four desired data points,

and wherein the executable code that programs the processor to determine computed offset data comprises;

executable code that programs the processor to perform the DOC process, wherein the DOC process comprises building a 3×

3 matrix including the at least four desired data points.

13. The system of claim 9 wherein the plurality of executable instructions comprise:

executable code that programs the processor to initiate the DOC process in response to a user performing a predetermined maneuver with the hand-held computer system,

executable code that programs the processor to run the DOC process constantly as a background DOC process until time period conditions, stationary conditions, geometric diversity conditions, or data limit conditions are met, or

executable code that programs the processor to initiate the DOC process in response to a user performing, with the hand-held computer system, a motion of the user retrieving the hand-held computer system from a first user position, holding the computer system at a second user position, holding the computer system at a third user position, and then returning the computer system to the first user position.

14. The system of claim 9 wherein the plurality of executable instructions comprise:

executable code that programs the processor to sense, by the MEMS sensor, user-initiated calibration data measurements as the user places the hand-held computer system on a level surface and presses a button, or as the user performs a figure 8 maneuver, and determining, by the processor, user-initiated computed offset data using the user-initiated calibration data measurements.

15. The system of claim 9 wherein the MEMS sensor comprises a MEMS accelerometer and the integrated MEMS device comprises

an integrated 6-axis MEMS inertial sensing device including the MEMS accelerometer and a MEMS gyroscope,

an integrated 6-axis MEMS inertial sensing device including the MEMS accelerometer and a Magnetometer, or

an integrated 9-axis or 10-axis inertial sensing device including the MEMS accelerometer and a MEMS gyroscope, a magnetometer, and a pressure sensor.

16. A system comprising a micro-processor, on-chip logic for processing data from an integrated MEMS device disposed within a hand-held computer system, the system comprising:

a sense module configured for sensing, by the MEMS sensor disposed within the computer system, calibration data measurements; and

a correction module configured for determining, with a processor disposed within the computer system, computed offset data for the MEMS sensor through a dynamic offset correction (DOC) process using the calibration data measurements.

17. The system of claim 16 wherein the sensing of the calibration data measurements comprises sensing X, Y, and Z axis sensor data in one or more static orientations for a predetermined time period;

wherein the calibration data measurements includes a plurality of valid data points, and wherein the DOC process comprises building an N×

3 matrix including the plurality of valid data points and using an Ordinary Least Squares method.

18. The system of claim 16 wherein the calibration data measurements includes at least four desired data points, and wherein the DOC process comprises building a 3×

3 matrix including the at least four desired data points.

19. The system of claim 16 wherein the DOC process is initiated by a user performing a predetermined maneuver with the hand-held computer system;

wherein the predetermined maneuver comprises a motion of the user retrieving the hand-held computer system from a first user position, holding the computer system at a second user position, holding the computer system at a third and then fourth user position.

20. The system of claim 16 wherein the DOC process is configured as a background DOC process that constantly runs until predetermined calibration conditions are met;

wherein the predetermined calibration conditions include time period conditions, stationary conditions, geometric diversity conditions, or data limit conditions.

21. The system of claim 20 wherein the conditions of time period, stationary conditions, geometric diversity conditions, or data limit conditions are modified over time to improve accuracy after an initial period of convergence or completion using less stringent conditions.

22. The system of claim 16 further comprising a user-initiated calibration process including sensing, by the MEMS sensor, user-initiated calibration data measurements as the user places the hand-held computer system on a level surface and presses a button, or as the user performs a figure 8 maneuver, and determining, by the processor, user-initiated computed offset data using the user-initiated calibration data measurements.

23. The system of claim 16 wherein the MEMS sensor comprises a MEMS accelerometer and the integrated MEMS device comprises an integrated 3-axis MEMS accelerometer, or a 6-axis MEMS inertial sensing device including the MEMS accelerometer and a MEMS gyroscope, or 6-axis device including the MEMS accelerometer and a MEMS magnetometer.