Heading estimation for determining a user's location

Patent metadata

Field	Value
Publication number	US-9803982-B2
Application number	US-201414426604-A
Country	US
Kind code	B2
Filing date	Apr 28, 2014
Priority date	Apr 28, 2014
Publication date	Oct 31, 2017
Grant date	Oct 31, 2017

Abstract

Technologies for determining a user's location by a mobile computing device include detecting, based on sensed inertial characteristics of the mobile computing device, that a user of the mobile computing device has taken a physical step in a direction. The mobile computing device determines a directional heading of the mobile computing device in the direction and a variation of an orientation of the mobile computing device relative to a previous orientation of the mobile computing device at a previous physical step of the user based on the sensed inertial characteristics. The mobile computing device further applies a Kalman filter to determine a heading of the user based on the determined directional heading of the mobile computing device and the variation of the orientation and determines an estimated location of the user based on the user's determined heading, an estimated step length of the user, and a previous location of the user at the previous physical step.

First claim

The invention claimed is:

1. A mobile computing device for determining a user's location, the mobile computing device comprising:
a plurality of inertial sensors to sense inertial characteristics of the mobile computing device;
a sensor processing module to detect that a user of the mobile computing device has taken a physical step in a direction based on the inertial characteristics of the mobile computing device sensed by the plurality of inertial sensors;
a raw heading estimation module to determine a directional heading of the mobile computing device in the direction and a variation of an orientation of the mobile computing device relative to a previous orientation of the mobile computing device at a previous physical step of the user based on the sensed inertial characteristics;
a Kalman filter module to apply a Kalman filter to determine a heading of the user based on the determined directional heading and the variation of the orientation of the mobile computing device; and
a location determination module to determine an estimated location of the user based on the determined heading of the user, an estimated step length of the user, and a previous location of the user at the previous physical step.

2. The mobile computing device of claim 1 , wherein to detect that the user has taken a physical step, determine the directional heading of the mobile computing device and the variation of the orientation of the mobile computing device, apply the Kalman filter to determine the heading of the user, and determine the estimated location of the user comprises to:
detect that the user has taken a physical step, determine the directional heading of the mobile computing device and the variation of the orientation of the mobile computing device, apply the Kalman filter to determine the heading of the user, and determine the estimated location of the user for each of a plurality of sequential physical steps taken by the user.

3. The mobile computing device of claim 2 , further comprising a motion management module to (i) determine whether the mobile computing device has been tilted in a non-horizontal direction in response to a detection that the user has taken the physical step and (ii) ignore the detected physical step in response to a determination that the mobile computing device has been tilted in the non-horizontal direction.

4. The mobile computing device of claim 2 , further comprising a motion management module to (i) determine whether the mobile computing device has been rotated along a horizontal plane by an amount exceeding a reference threshold and (ii) reinitialize the Kalman filter in response to a determination that the mobile computing device has been rotated along the horizontal plane by an amount exceeding the reference threshold.

5. The mobile computing device of claim 4 , wherein the reference threshold is ninety degrees of rotation.

6. The mobile computing device of claim 4 , wherein to reinitialize the Kalman filter comprises to increase a state covariance of the Kalman filter to increase the Kalman filter's tolerance in error.

7. The mobile computing device of claim 2 , further comprising a location refinement module to refine the determined estimated location of the user in response to a determination that (i) the Kalman filter has been reinitialized and (ii) a number of physical steps taken by the user subsequent to reinitialization of the Kalman filter exceeds a reference threshold.

8. The mobile computing device of claim 7 , wherein to refine the determined estimated location comprises to:
update, in response to a determination that the number of physical steps taken by the user subsequent to the reinitialization has reached the reference threshold, the user's heading for each of the physical steps subsequent to the reinitialization up to the step at which the user reached the reference threshold based on the determined heading at the step at which the user reached the reference threshold; and
recalculate the estimated location of the user based on the user's updated heading.

9. The mobile computing device of claim 2 , wherein to apply the Kalman filter comprises to apply a linear Kalman filter having a state transition function, x k =x k−1 +O k −O k−1 +ε k , and a measurement function, y k =x k +δ k , wherein:
x k is the determined heading of the user at step k,
O k is an orientation of the mobile computing device at step k,
ε k is a state transition error at step k,
y k is the determined directional heading of the mobile computing device at step k, and
δ k is a measurement error associated with integration of an acceleration of the mobile computing device at step k.

10. The mobile computing device of claim 2 , wherein to apply the Kalman filter comprises to apply a linear Kalman filter having a state transition function, x k =H k −H k−1 =O k −O k−1 +ε k , and a measurement function, y k =x k +H k−1 +δ k , wherein:
H k is an estimated heading of the user at step k,
x k is an estimated heading change at step k,
O k is an orientation of the mobile computing device at step k,
ε k is a state transition error at step k,
y k is the determined directional heading of the mobile computing device at step k, and
δ k is a measurement error associated with integration of an acceleration of the mobile computing device at step k.

11. The mobile computing device of claim 1 , wherein to determine a directional heading of the mobile computing device in the direction comprises to determine a velocity of the mobile computing device in the direction.

12. The mobile computing device of claim 11 , wherein to determine the velocity of the mobile computing device in the direction comprises to:
sense an acceleration of the mobile computing device with an inertial sensor of the plurality of inertial sensors;
convert the sensed acceleration from a frame of reference of the inertial sensor to an acceleration in Earth's frame of reference; and
determine a velocity of the mobile computing device in the direction based on the acceleration in Earth's frame of reference.

13. The mobile computing device of claim 12 , wherein to determine the velocity of the mobile computing device in the direction comprises to:
determine a rotation matrix mapping the frame of reference of the inertial sensor to Earth's frame of reference;
apply the determined rotation matrix to the sensed acceleration to determine an acceleration of the mobile computing device in Earth's frame of reference;
integrate the acceleration in Earth's frame of reference to determine a velocity in Earth's frame of reference; and
project the determined velocity in Earth's frame of reference onto a horizontal plane on which the user physically stepped.

14. One or more machine-readable storage media comprising a plurality of instructions stored thereon that, in response to execution by a mobile computing device, cause the mobile computing device to:
detect, based on sensed inertial characteristics of the mobile computing device, that a user of the mobile computing device has taken a physical step in a direction;
determine a directional heading of the mobile computing device in the direction and a variation of an orientation of the mobile computing device relative to a previous orientation of the mobile computing device at a previous physical step of the user based on the sensed inertial characteristics;
apply a Kalman filter to determine a heading of the user based on the determined directional heading of the user and the variation of the orientation of the mobile computing device; and
determine an estimated location of the user based on the determine

Assignees

• Intel Corp
• Han Ke
• Ding Ke
• Ma Jingyi
• Huang Yuhuan

Inventors

• Han Ke
• Ding Ke
• Ma Jingyi
• Huang Yuhuan

Classifications

• G01C21/183 Primary

  Compensation of inertial measurements, e.g. for temperature effects · CPC title

• G01C21/16 Primary

  by integrating acceleration or speed, i.e. inertial navigation · CPC title