APPARATUS AND METHODOLOGY FOR CALIBRATION OF A GYROSCOPE AND A COMPASS INCLUDED IN A HANDHELD DEVICE

• US 20110178707A1
• Filed: 01/21/2010
• Published: 07/21/2011
• Est. Priority Date: 01/21/2010
• Status: Active Grant

• Current Assignee: Invensense Incorporated (TDK Corporation)
• Original Assignee: Invensense Incorporated (TDK Corporation)
• Inventors: Lin, Shang Hung, Sachs, David
• Granted Patent: US 8,326,533 B2
• Time in Patent Office: Days
• US Class Current: 701/216
• CPC Class Codes: G01C 17/38 Testing, calibrating, or compensating of compasses
• CPC Class Codes: G01C 19/00 Gyroscopes; Turn-sensitive devices using vibrating masses; Turn-sensitive devices without moving masses; Measuring angular rate using gyroscopic effects
• CPC Class Codes: G01C 25/005 initial alignment, calibration or starting-up of inertial devices

Abstract

Novel techniques for estimating compass and gyroscope biases for handheld devices are disclosed. The handheld devices can include wireless phones, navigational devices and video gaming systems. The compass bias can be determined by causing a small movement of the handheld device and comparing the data obtained from the compass with the data obtained from the gyroscope. The gyroscope bias can be determined by obtaining a quaternion based angular velocity term of the handheld device when the accelerometer and compass data are reliable, and then comparing the angular velocity term to with the gyro data estimate the gyro bias. When the compass and/or the accelerometer data are unreliable, a previously determined quaternion angular velocity term is used, which was determined when the compass and the accelerometer were providing reliable data. The gyroscope bias can also be determined by measuring gyroscope biases at various temperatures in a non-factory setting, and storing that data in a memory, and using the data to estimate gyro biases when the accelerometer and/or the compass data are unreliable.

Claims

1. A method for a handheld device, comprising:

rotating the handheld device through an angle;

receiving rotation information from a gyroscope;

receiving rotation information from a compass;

comparing the information received from the gyroscope with the information received from the compass;

determining a compass bias from the comparison; and

correcting the compass bias.

2. The method of claim 1, wherein:

the information received from the compass includes a first magnetic vector information for a first handheld device position and a second magnetic vector information for a second handheld device position;

wherein

the first and second positions define an angle of rotation of the handheld device for which the gyroscope data is integrated.

3. The method of claim 1, wherein the rotation is caused by an unintentional hand jitter.

4. The method of claim 1, wherein the compass bias is caused by a metal device or a magnetic field external to the compass.

5. The method of claim 1, further comprising:

correcting a magnetic field spike caused by a wireless device.

6. The method of claim 1, further comprising:

adjusting the compass sensitivity value based on the comparison.

7. The method of claim 1, further comprising:

receiving rotation information from an accelerometer;

determining a first angular velocity term for the handheld device by using the rotation information received from the compass, the accelerometer and the gyroscope;

comparing the information received from the gyroscope with the first angular velocity term; and

using the result of the comparison to determine a gyroscope bias.

8. The method of claim 7, wherein:

comparing the information received from the gyroscope with the first angular velocity term if the information received from the accelerometer and compass is reliable; and

comparing the information received from the gyroscope with a second angular velocity term stored in a memory if the information received from the accelerometer or the compass is unreliable;

wherein,

the second angular velocity term includes an angular velocity term that was determined when the information received from the accelerometer and compass was reliable.

9. A method for calibrating a gyroscope implemented in a handheld device, comprising:

having the handheld device in a non-factory setting;

having an environment in which the handheld device is not subject to a strong linear acceleration;

having an environment in which the handheld device is not subject to a rapidly changing magnetic field;

having an environment in which the temperature is changing;

measuring gyroscope biases at various temperature values; and

storing the measurements and temperature values in a table in a memory.

10. A method of claim 9, further comprising:

using the table to determine a gyroscope bias in an environment in which an accelerometer data is unreliable.

11. A method of claim 9, further comprising:

using the table to determine a gyroscope bias in an environment in which a compass data is unreliable.

12. A handheld consumer electronics device comprising:

a gyroscope;

a compass;

a processor programmed to receive information from the gyroscope and the compass; and

the processor programmed to determine a compass bias by comparing a rotation information received from the gyroscope with a rotation information received from the compass;

wherein,

the rotation information is generated by rotating the handheld device through an angle.

13. The handheld device of claim 12, wherein:

the information received from the compass includes a first magnetic vector information for a first handheld device position and a second magnetic vector information for a second handheld device position;

wherein

the first and second positions define an integrated gyroscope angle.

14. The handheld device of claim 12, further comprising:

an accelerometer;

the processor programmed to receive rotation information from the accelerometer; and

the processor programmed to determine a first angular velocity term for the handheld device by using the rotation information received from the compass, the accelerometer and the gyroscope;

the processor programmed to compare the information received from the gyroscope with the first angular velocity term; and

the processor programmed to use the result of the comparison to determine a gyroscope bias.

15. The handheld device of claim 14, wherein:

the processor programmed to compare the information received from the gyroscope with the first angular velocity term if the information received from the accelerometer and compass is reliable; and

the processor programmed to compare the information received from the gyroscope with a second angular velocity term stored in a memory if the information received from the accelerometer or the compass is unreliable;

wherein,

the second angular velocity term includes an angular velocity term that was determined when the information received from the accelerometer and compass was reliable.

16. The handheld device of claim 12, further comprising:

the processor programmed to adjust the compass sensitivity value based on comparing rotation information received from the gyroscope with the rotation information received from the compass.

17. The handheld device of claim 12, further comprising:

a measurement circuit for measuring gyroscope biases at various temperature values; and

a memory for storing the measurements and temperature values in a table;

wherein,

the processor is programmed to use the table to estimate the gyroscope bias if the compass or accelerometer data are unreliable.

18. The handheld device of claim 12, further comprising:

a wireless phone including a navigation system coupled to a global positioning system;

an electronic display;

wherein,

the electronic display for displaying a user'"'"'s position in real time.

19. The handheld device of claim 12, further comprising:

an electronic display;

the processor programmed to recognize a user'"'"'s signature;

wherein,

the user can make a signature by moving of the handheld device in the air; and

the electronic display for displaying the trajectory of the movement of the handheld device in real time.

20. The handheld device of claim 19, further comprising:

the handheld device is remotely coupled to a database;

wherein,

the database includes a library of signatures; and

the library is used for authenticating the user'"'"'s signature.