METHODS AND APPARATUS FOR INCREMENTAL PREDICTION OF INPUT DEVICE MOTION

• US 20100060573A1
• Filed: 09/09/2008
• Published: 03/11/2010
• Est. Priority Date: 09/09/2008
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: MOUSSAVI, Farshid
• Granted Patent: US 8,766,915 B2
• Time in Patent Office: Days
• US Class Current: 345/158
• CPC Class Codes: G06F 3/038 Control and interface arrangements therefor, e.g. drivers or device-embedded control circuitry

Abstract

Methods and apparatus for incremental prediction of input device motion. In one embodiment, the input device comprises one or more sensors adapted to output motional data of the input device as measured at a certain period. A prediction of input device motion is generated based upon the last prediction and a weighted error in estimate determined by the sensory output. According to one embodiment, the weight is calculated as a Kalman gain. In one embodiment, once the prediction has been generated, it is provided to a display update algorithm adapted to orient a navigational object upon an associated display screen.

Claims

1. A method comprising:

predicting a position of an input device based at least in part upon a first quantity and a second quantity; and

updating a confidence value for use in a subsequent prediction, wherein the first quantity comprises at least one of a predicted position, a predicted velocity, and a predicted acceleration of the input device, and wherein the second quantity comprises an error in prediction.

2. The method of claim 1, wherein the input device comprises an accelerometer.

3. The method of claim 1, wherein the second quantity further comprises a scaling value.

4. The method of claim 3, wherein the scaling value is based at least in part upon the confidence value and a noise value.

5. The method of claim 4, wherein the noise value is based at least in part upon characteristics of the accelerometer.

6. The method of claim 4, wherein the scaling value is inversely related to the noise value.

7. The method of claim 3, wherein the second quantity comprises a product of the scaling value and the error in prediction.

8. The method of claim 7, wherein the error in prediction comprises the difference between a recorded acceleration and a predicted acceleration of the input device.

9. The method of claim 3, wherein the scaling value is calculated as a Kalman gain.

10. A method comprising:

calculating a first quantity based at least in part upon a prediction of motion of an input device;

determining a weight for a second quantity based at least in part upon a noise value and a margin of error associated with a set of prior predictions;

generating an estimate for motion of an input device for a next period based at least in part upon the first quantity, the weight, and the second quantity; and

updating the margin of error.

11. The method of claim 10, wherein the input device comprises a micro-electromechanical sensor.

12. The method of claim 10, wherein the second quantity comprises an error in estimate.

13. The method of claim 12, wherein the error in estimate comprises a difference between data recorded at the next period and data associated with the estimate of motion for the prior period.

14. The method of claim 10, wherein the weight comprises a Kalman gain.

15. The method of claim 10, wherein the weight is adapted to indicate the significance of the second quantity.

16. The method of claim 10, wherein the weight comprises a value greater than or equal to zero and less than or equal to one.

17. The method of claim 10, further comprising transmitting the estimate for motion of the input device for the next period to display update logic.

18. A computer readable medium comprising instructions which, when executed by a computer, perform a process comprising:

generating a first value, wherein the first value comprises a prediction of the position of an input device at the next period that is based at least in part upon a prediction of the position of the input device at the current period;

generating a second value, wherein the second value is based in part upon a confidence value and a noise value;

generating a third value, wherein the third value comprises a sum of the first value and the product of the second value and a quantity related to a set of measurements for the next period; and

updating the confidence value.

19. The computer readable medium of claim 18, wherein the input device comprises a force sensor.

20. The computer readable medium of claim 18, wherein the noise value is determined from a calibration sequence associated with the input device.

21. The computer readable medium of claim 18, wherein the set of measurements comprise a measured acceleration of the input device.

22. The computer readable medium of claim 21, wherein the set of measurements comprise a measured velocity of the input device.

23. The computer readable medium of claim 18, wherein the second value and the noise value are inversely proportional.

24. The computer readable medium of claim 18, wherein the second value comprises a value derived from a Kalman filter.

25. An apparatus comprising:

a first module adapted to predict a position of an input device at a second period based at least in part upon a predicted position of the input device at a first period;

a second module adapted to determine a weight to assign an error in prediction based at least in part upon an expected amount of noise and a variance;

a third module adapted to predict the position of the input device at the second period based at least in part upon output from the first and second modules; and

a fourth module adapted to update the variance.

26. The apparatus of claim 25, wherein the input device comprises an accelerometer.

27. The apparatus of claim 25, wherein the weight comprises a Kalman gain.

28. The apparatus of claim 25, further comprising a fifth module adapted to transmit the output of the third module to display update logic.

29. The apparatus of claim 25, wherein the expected amount of noise is determined from results of a calibration sequence associated with the input device.

30. The apparatus of claim 25, wherein the expected amount of noise is based at least in part upon characteristics of the input device.

31. The apparatus of claim 25, wherein the third module is further adapted to predict the position of the input device by adding the output from the first module to the product of the output from the second module with an error in prediction.

32. The apparatus of claim 31, wherein the error in prediction comprises the difference between data recorded at the second period and data estimated at the first period.

33. An input device comprising:

a first module adapted to generate a first value indicating acceleration of the input device at a current period;

a second module adapted to store a second value indicating a prediction of motion of the input device for a prior period; and

a third module adapted to generate a third value indicating a prediction of motion of the input device for the current period, wherein the third value is based at least in part upon the first value and the second value.

34. The input device of claim 33, wherein the first module comprises a micro-electromechanical accelerometer.

35. The input device of claim 33, wherein the second module comprises a memory module.

36. The input device of claim 33, wherein the third value is based at least in part upon a sum of the second value and a first quantity, wherein the first quantity comprises the difference between the first value and the second value.

37. The input device of claim 36, wherein the first quantity is scaled by a fourth value, wherein the fourth value is based at least in part upon a margin of error and an amount of noise associated with the first module.

38. The input device of claim 37, wherein the fourth value comprises a Kalman gain.

39. The input device of claim 37 further comprising a fourth module adapted to update the margin of error after the third value has been generated.

40. The input device of claim 33 further comprising a fourth module adapted to transmit the third value to display update logic.