VELOCITY STABILIZATION FOR ACCELEROMETER BASED INPUT DEVICES

• US 20100026623A1
• Filed: 07/30/2008
• Published: 02/04/2010
• Est. Priority Date: 07/30/2008
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: MOUSSAVI, Farshid
• Granted Patent: US 8,933,875 B2
• Time in Patent Office: Days
• US Class Current: 345/156
• CPC Class Codes: G06F 3/03543 Mice or pucks G06F3/03541 takes precedence
• CPC Class Codes: G06F 3/0383 Signal control means within the pointing device

Abstract

A method and apparatus for reducing or eliminating tracking errors associated with accelerometer-based input devices. The method and apparatus calculates a velocity of the input device; determines if the calculated velocity indicates a motion tracking error; and ignores the calculated velocity if the motion tracking error is indicated.

Claims

1. A method for compensating for motion tracking errors associated with an electronic input device, the method comprising:

calculating a velocity of the electronic input device;

determining if the calculated velocity indicates a motion tracking error; and

ignoring the calculated velocity if the motion tracking error is indicated.

2. The method of claim 1 wherein the motion tracking error comprises a drift error.

3. The method of claim 2 wherein the act of determining comprises:

calculating an average velocity of the input device for a given time period;

determining if the average velocity is below a first threshold; and

determining if a magnitude of a calculated velocity at the end of the given time period exceeds a second threshold, wherein if the magnitude does not exceed the second threshold, the drift error is indicated.

4. The method of claim 1 wherein the motion tracking error comprises a kickback error.

5. The method of claim 4 wherein the act of determining comprises:

determining if the input device is decelerating;

determining if the input device has changed direction; and

if it is determined that the input device is decelerating and has changed direction, determining if a magnitude of the calculated velocity of the input device is greater than a predetermined threshold, wherein if the magnitude is not greater than the threshold, the kickback error is indicated.

6. The method of claim 1 wherein the calculated velocity is calculated from acceleration measurements.

7. An electronic input device, comprising:

a motion sensor for generating a signal indicative of a velocity of the electronic input device; and

a processor, coupled to the motion sensor, operable to receive the signal and determine if the velocity indicates a motion tracking error, wherein if the motion tracking error is indicated the processor is further operable to set the velocity of the input device to zero.

8. The electronic input device of claim 7 wherein the motion tracking error comprises a drift error.

9. The device of claim 8 wherein the processor is further operable to:

calculate an average of velocity of the input device for a given time period;

determine if the average velocity is below a first threshold; and

determine if a magnitude of a calculated velocity at the end of the given time period exceeds a second threshold, wherein if the magnitude does not exceed the second threshold, the drift error is indicated.

10. The device of claim 7 wherein the motion tracking error comprises a kickback error.

11. The device of claim 10 wherein the processing element is further operable to:

determine if the input device is decelerating;

determine if the velocity of the input device has changed direction; and

if it is determined that the input device is decelerating and has changed direction, determine if a magnitude of a calculated velocity of the input device is greater than a predetermined threshold, wherein if the magnitude is not greater than the threshold, the kickback error is indicated.

12. The device of claim 7 wherein the motion sensor comprises a MEMS accelerometer.

13. A system for tracking the motion of an electronic input device, comprising:

a motion sensor contained within a housing of the electronic input device for generating a signal indicative of a velocity of the electronic input device;

a processor, coupled to the motion sensor, operable to receive the signal and determine if the velocity indicates a motion tracking error, and to ignore the velocity if the motion tracking error is indicated;

a computing device having a display screen for displaying an object controlled by the input device; and

a peripheral interface for coupling the electronic input device to the computing device.

14. The system of claim 13 wherein the processor is contained within the housing of the electronic input device.

15. The system of claim 13 wherein the processor is contained within a housing of the computing device.

16. The system of claim 13 wherein the motion tracking error comprises a drift error.

17. The system of claim 16 wherein the processor is further operable to:

calculate an average velocity of the input device for a given time period;

determine if the average velocity is below a first threshold; and

if the average velocity is below the first threshold, determine if a magnitude of a calculated velocity at the end of the given time period exceeds a second threshold, wherein if the magnitude does not exceed the second threshold, the drift error is indicated.

18. The system of claim 13 wherein the motion tracking error comprises a kickback error.

19. The system of claim 18 wherein the processor is further operable to:

determine if the input device is decelerating;

determine if the input device has changed direction; and

if it is determined that the input device is decelerating and has changed direction, determine if a magnitude of a calculated velocity of the input device is greater than a predetermined threshold, wherein if the magnitude is not greater than the threshold, the kickback error is indicated.

20. The system of claim 13 wherein the motion sensor comprises a MEMS accelerometer.

21. A computer readable medium for storing computer executable instructions that when executed perform a method for compensating for tracking errors of an electronic input device, the method comprising:

receiving a signal indicative of a velocity of the electronic input device;

determining if the velocity indicates a motion tracking error; and

ignoring the velocity if the motion tracking error is indicated.

22. The computer readable medium of claim 21 wherein the motion tracking error comprises a drift error.

23. The computer readable medium of claim 22 wherein the act of determining comprises:

calculating an average velocity of the input device for a given time period;

determining if the average velocity is below a first threshold; and

if the average velocity if below the first threshold, determining if a magnitude of a calculated velocity at the end of the given time period exceeds a second threshold, wherein if the magnitude does not exceed the second threshold, the drift error is indicated.

24. The computer readable medium of claim 21 wherein the motion tracking error comprises a kickback error.

25. The computer readable medium of claim 25 wherein the act of determining comprises:

determining if the input device is decelerating;

determining if the input device has changed direction; and

if it is determined that the input device is decelerating and has changed direction, determining if a magnitude of a calculated velocity of the input device is greater than a predetermined threshold, wherein if the magnitude is not greater than the threshold, the kickback error is indicated.