Methods and apparatus for incremental prediction of input device motion

• US 8,766,915 B2
• Filed: 09/09/2008
• Issued: 07/01/2014
• Est. Priority Date: 09/09/2008
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Moussavi, Farshid
• Primary Examiner(s): Boddie, William
• Assistant Examiner(s): Edwards, Carolyn R
• Application Number:
  US12/207,452
• Publication Number:
  US 20100060573A1
• Time in Patent Office: 2,121 Days
• Field of Search: 345156-178, 702/141
• 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, using one or more processors, a position of an input device based at least in part upon a first quantity and a second quantity, where an initial prediction of the position at a next period is generated based upon an updated prediction of the position for a current period and a proxy for an acceleration input;

updating, using the one or more processors, a confidence value for use in a subsequent prediction, wherein the first quantity includes a predicted velocity of the input device, and wherein the second quantity includes an error in the predicted velocity, where the error in the predicted velocity is determined by subtracting the predicted velocity from a measured value of velocity determined from vibrational signals; and

resetting a margin of error of values associated with predicting the position of the input device when the velocity of the input device reaches a predefined threshold.

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 an 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. An apparatus comprising:

a printed circuit board including;

one or more sensors;

one or more processors;

memory configured for storing instructions, which, when executed by the one or more processors, causes the one or more processors to perform operations comprising;

predicting, using one or more processors, a position of an input device based at least in part upon a first quantity and a second quantity, where an initial prediction of the position at a next period is generated based upon an updated prediction of the position for a current period and a proxy for an acceleration input;

updating, using the one or more processors, a confidence value for use in a subsequent prediction, wherein the first quantity includes a predicted velocity of the input device, and wherein the second quantity includes an error in the predicted velocity, where the error in the predicted velocity is determined by subtracting the predicted velocity from a measured value of velocity determined from vibrational signals; and

resetting a margin of error of values associated with predicting the position of the input device when a velocity of the input device reaches a predefined threshold.

11. The apparatus of claim 10, wherein the one or more sensors includes an accelerometer.

12. The apparatus of claim 10, wherein the second quantity further comprises a scaling value that is based at least in part upon the confidence value and a noise value.

13. The apparatus of claim 10, further comprising a circuit to transmit the output of the one or more processors to display update logic.

14. The apparatus of claim 10, wherein the noise value is determined from results of a calibration sequence associated with the one or more sensors.

15. The apparatus of claim 10, wherein the noise value is based at least in part upon characteristics of the one or more sensors.