SINGLE POINT OFFSET CALIBRATION FOR INERTIAL SENSORS

• US 20140012531A1
• Filed: 07/05/2013
• Published: 01/09/2014
• Est. Priority Date: 07/06/2012
• Status: Active Grant

• Current Assignee: Movella Incorporated (Movella Holdings, Inc.)
• Original Assignee: mCube, Inc.
• Inventors: BHANDARI, Sanjay, KELLY, Joe
• Granted Patent: US 9,594,095 B2
• Time in Patent Office: Days
• US Class Current: 702/104
• CPC Class Codes: G01C 25/005 initial alignment, calibration or starting-up of inertial devices
• 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 (Micro-Electro-Mechanical-Systems) device disposed within a hand-held computer system and methods therefor. The Single Point Offset Correction (SPOC) process computes offset values to calibrate MEMS sensors using a single set of data measurements at an orientation without dynamic perturbation, and without requiring advance knowledge of orientation of the device. Arbitrary output biases, which are known to be dominant on a single axis, can be corrected to ensure consistent performance. The SPOC process provides a simple method to effectively calibrate a MEMS sensor without requiring extensive system resources. This process can be enhanced by additional estimations of sensor offsets using the set of data measurements or by use of rule-based empirical gain factors.

Claims

1. A micro-processor, on-chip logic, or software implemented method for processing data from a MEMS (Micro-Electro-Mechanical-Systems) sensor 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, a single calibration data measurement point; and

determining, with a processor disposed within the computer system, computed offset data for the MEMS sensor through a Single Point Offset Correction (SPOC) process using the single calibration data measurement point.

2. The method of claim 1 wherein wherein the sensing of the single calibration data measurement point comprises sensing a set of X, Y, and Z axis sensor data in one static orientation for a predetermined time period;

and

wherein the X, Y, and Z axis sensor data are denoted as X_m, Y_m, and Z_m, respectively.

3. The method of claim 2 wherein the one static orientation includes an orientation without dynamic perturbation.

4. The method of claim 2 wherein the SPOC process comprises determining an offset value of the computed offset data via the following equation:

Offset Dependent Error=1 g²−

(X_m²+Y_m²+Z_m²), where g=9.8 m/s².

5. The method of claim 4 further comprising applying the offset value to the a single axis of the MEMS sensor assumed to have the worst errors.

6. The method of claim 4 wherein the SPOC process comprises:

determining rule-based empirical gain factors using the single calibration data measurement point and a priori error statistic of an axis of the component; and

applying the rule-based empirical gain factors to the computed offset data and applying the computed offset data to the X, Y, or Z axis of the MEMS sensor.

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

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

8. The method of claim 7 wherein time period conditions, stationary conditions, or data limit conditions are modified over time to improve accuracy after an initial period of convergence or completion using less stringent conditions.

9. The method of claim 1 wherein the MEMS sensor comprises a MEMS accelerometer, a MEMS gyrometer, or other MEMS inertial sensor.

10. The method of claim 1 wherein the SPOC process includes determining self-test based actuation and measurement information.

11. A hand-held inertial sensor system for processing data from an integrated MEMS (Micro-Electro-Mechanical-Systems) 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 comprises;

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

executable code that programs the processor to determine, with the processor disposed within the computer system, computed offset data for the MEMS sensor through a Single Point Offset Correction (SPOC) process using the single calibration data measurement point.

12. The system of claim 11 wherein the executable code that programs the processor to sense the single calibration data measurement point comprises:

executable code that programs the processor to sense, by the MEMS sensor, a set of X, Y, and Z axis sensor data in one static orientation for a predetermined time period; and

wherein the X, Y, and Z axis sensor data are denoted as X_m, Y_m, and Z_m, respectively.

13. The system of claim 12 wherein the executable code that programs the processor to sense the single calibration data measurement point comprises:

executable code that programs the processor to sense, by the MEMS sensor, the set of X, Y, and Z axis sensor data in a static orientation without dynamic perturbation.

14. The system of claim 12 wherein the executable code that programs the processor to determine the computed offset data using the SPOC process comprises:

executable code that programs the processor to determine an offset dependent squared-error value of the computed offset data via the following equation;

Offset Dependent Error=1 g²−

(X_m²+Y_m²+Z_m²), where g=9.8 m/s².

15. The system of claim 14 wherein the plurality of executable instructions comprises:

executable code that programs the processor to apply the offset value to the Z axis of the MEMS sensor.

16. The system of claim 14 wherein the executable code that programs the processor to determine the computed offset data using the SPOC process comprises:

executable code that programs the processor to determine rule-based empirical gain factors using the single calibration data measurement point; and

executable code that programs the processor to apply the rule-based empirical factors to the computed offset data and applying the computed offset data to the X, Y, or Z axis of the MEMS sensor.

17. The system of claim 12 wherein the plurality of executable instructions comprise:

executable code that programs the processor to initiate the SPOC process in response to a user, developer, or manufacturer command;

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

executable code that programs the processor to initiate the SPOC process.

18. The system of claim 12 wherein the plurality of executable instructions comprises executable code that programs the processor to determine self-test based actuation and measurement information.

19. A system for processing data from a MEMS (Micro-Electro-Mechanical-Systems) sensor 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, a single calibration data measurement point; and

a correction module configured for determining, with a processor disposed within the computer system, computed offset data for the MEMS sensor through a Single Point Offset Correction (SPOC) process using the single calibration data measurement point.

20. The system of claim 19 wherein the sense module is configured to sense a set of X, Y, and Z axis sensor data in one static orientation for a predetermined time period;

and

wherein the X, Y, and Z axis sensor data are denoted as X_m, Y_m, and Z_m, respectively.

21. The system of claim 20 wherein correction module comprises executable code that programs the processor to sense, by the MEMS sensor, the set of X, Y, and Z axis sensor data in a static orientation without dynamic perturbation.

22. The system of claim 20 wherein the correction module is configured to determine an offset value of the computed offset data via the SPOC process using the following equation:

Offset dependent squared-error=1 g²−

(X_m²+Y_m²+Z_m²), where g=9.8 m/s².

23. The system of claim 22 wherein the correction module is configured to apply the offset value to a single axis of the MEMS sensor.

24. The system of claim 20 wherein the correction module is configured to determine rule-based empirical factors via the SPOC process using the single calibration data measurement point;

and

wherein the correction module is configured to apply the rule-based empirical gain factors to the computed offset data and apply the computed offset data to the X, Y, or Z axis of the MEMS sensor.