Device State Estimation With Body-Fixed Assumption

• US 20170059601A1
• Filed: 09/02/2015
• Published: 03/02/2017
• Est. Priority Date: 09/02/2015
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Miller, Isaac Thomas
• Granted Patent: US 10,895,626 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G01S 19/14 specially adapted for specific applications
• CPC Class Codes: G01S 19/52 Determining velocity
• CPC Class Codes: G01S 5/0294 Trajectory determination or predictive filtering, e.g. target tracking or Kalman filtering

Abstract

Systems, methods, devices and computer-readable storage mediums are disclosed for device state estimation with body-fixed assumption. In some implementations, a method comprises: determining, by a device, a rotational velocity of a user of the device based on a sensor signal; determining, by the device, user speed; determining, by the device, user acceleration based on the user speed and the rotational velocity of the user; and updating a user state estimator based on the user acceleration.

Claims

1. A method comprising:

determining, by a device, a rotational velocity of a user of the device based on a sensor signal;

determining, by the device, user speed;

determining, by the device, user acceleration based on the device speed and the rotational velocity of the user; and

updating a user state estimator based on the user acceleration.

2. The method of claim 1, wherein determining the rotational velocity of the user, further comprises:

determining a rotational rate of the user in a reference coordinate frame;

determining a unit tangent vector to a path in the reference coordinate frame that the user is traveling along; and

determining the rotational velocity of the user based on a cross product of the rotational rate of the user and the unit tangent vector.

3. The method of claim 2, wherein the rotational rate of the user is determined based on the sensor signal.

4. The method of claim 3, wherein the rotational rate of the user is determined based on detecting and subtracting out a periodic rotation component of the sensor signal that is due to a swinging limb of the user such that the remaining sensor signal is due to the rotation of the user.

5. The method of claim 1, wherein the user speed is estimated by the user state estimator.

6. The method of claim 1, wherein user acceleration based on the user speed and the rotational rate of the user is determined by the formula,

=s·

(_user×

_v),

where is a user acceleration vector, _user is the rotational rate of the user, s is user speed and _v is a unit tangent vector to a path that the user is traveling along.

7. The method of claim 1, wherein the user acceleration is used to update a user state estimator between measurement time epochs.

8. The method of claim 5, wherein the update occurs at time indicated by a trigger signal or schedule based on a periodicity feature detected in the sensor signal.

9. A device comprising:

one or more sensors;

one or more processors;

memory coupled to the one or more processors and configured to store instructions, which, when executed by the one or more processors, causes the one or more processors to perform operations comprising;

determining, by a device, a rotational velocity of a user of the device based on a sensor signal;

determining, by the device, user speed;

determining, by the device, user acceleration based on the user speed and the rotational velocity of the user; and

updating a user state estimator based on the user acceleration.

10. The device of claim 9, wherein determining the rotational velocity of the user, further comprises:

determining a rotational rate of the user in a reference coordinate frame;

determining a unit tangent vector to a path in the reference coordinate frame that the user is traveling along; and

determining the rotational velocity of the user based on a cross product of the rotational rate of the user and the unit tangent vector.

11. The device of claim 10, wherein the rotational rate of the user is determined based on the sensor signal.

12. The device of claim 11, wherein the rotational rate of the user is determined based on detecting and subtracting out a periodic rotation component of the sensor signal that is due to a swinging limb of the user such that the remaining sensor signal is due to the rotation of the user.

13. The device of claim 9, wherein the user speed is estimated by the user state estimator.

14. The device of claim 9, wherein user acceleration based on the user speed and the rotational rate of the user is determined by the formula,

=s·

(_user×

_v),

where is a user acceleration vector, is the rotational rate of the user, s is user speed and ^v is a unit tangent vector to a path that the user is traveling along.

15. The device of claim 9, wherein the user acceleration is used to update a user state estimator between measurement time epochs.

16. The device of claim 15, wherein the update occurs at time indicated by a trigger signal or schedule based on a periodicity feature detected in the sensor signal.

17. Anon-transitory, computer-readable storage medium storing instructions, which, when executed by one or more processors of a device, causes the one or more processors to perform operations comprising:

determining, by the device, a rotational velocity of a user of the device based on a sensor signal;

determining, by the device, user speed;

determining, by the device, user acceleration based on the device speed and the rotational velocity of the user; and

updating a user state estimator based on the user acceleration.

18. The non-transitory, computer-readable storage medium of claim 17, wherein determining the rotational velocity of the user, further comprises:

determining a rotational rate of the user in a reference coordinate frame;

determining a unit tangent vector to a path in the reference coordinate frame that the user is traveling along; and

determining the rotational velocity of the user based on a cross product of the rotational rate of the user and the unit tangent vector.

19. The non-transitory, computer-readable storage medium of claim 18, wherein the rotational rate of the user is determined based on the sensor signal.

20. The non-transitory, computer-readable storage medium of claim 19, wherein the rotational rate of the user is determined based on detecting and subtracting out a periodic rotation component of the sensor signal that is due to a swinging limb of the user such that the remaining sensor signal is due to the rotation of the user.