Method and Apparatus for Determination of Misalignment Between Device and Pedestrian

• US 20150354951A1
• Filed: 01/21/2014
• Published: 12/10/2015
• Est. Priority Date: 01/21/2013
• Status: Active Grant

• Current Assignee: Trusted Positioning Inc. (TDK Corporation)
• Original Assignee: Trusted Positioning Inc. (TDK Corporation)
• Inventors: Chang, Hsiu-Wen, Georgy, Jacques, Syed, Zainab, Goodall, Christopher, Ali, Abdelrahman
• Granted Patent: US 10,371,516 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G01B 21/24 for testing alignment of axes
• CPC Class Codes: G01C 21/185 for gravity
• CPC Class Codes: G01P 15/18 in two or more dimensions
• CPC Class Codes: G06F 3/0346 with detection of the device orientation or free movement in a 3D space, e.g. 3D mice, 6-DOF [six degrees of freedom] pointers using gyroscopes, accelerometers or tilt-sensors

Abstract

The present disclosure relates to a method and apparatus for determining the misalignment between a device and a pedestrian, wherein the pedestrian can carry, hold, or use the device in different orientations in a constrained or unconstrained manner, and wherein the device comprises a sensor assembly. The sensors in the device may be for example, accelerometers, gyroscopes, magnetometers, barometer among others. The sensors have a corresponding frame for the sensors'"'"' axes. The misalignment between the device and the pedestrian means the misalignment between the frame of the sensor assembly in the device and the frame of the pedestrian. The present method and apparatus can work whether in the presence or in the absence of absolute navigational information updates (such as, for example, Global Navigation Satellite System (GNSS) or WiFi positioning).

Claims

1. A method for determining misalignment between a device and a pedestrian, wherein the device comprises a tri-axial accelerometer, the method comprising the steps of:

a) calculating a plurality of levelled accelerometer readings from readings of the tri-axial accelerometer by transforming the tri-axial accelerometer readings into a levelled vertical accelerometer reading component and first and second horizontal acceleration components;

b) generating a vertical acceleration component from the levelled vertical accelerometer reading component;

c) calculating an along-track angle

d) determining a use case of the device;

e) detecting if a 180 degrees error in the along-track angle is present based on the use case; and

f) calculating a misalignment angle from the along-track angle and, if present, the 180 degrees error.

2. The method of claim 1, wherein calculating an along-track angle comprises applying a maximum possible variance technique on the first and second horizontal acceleration components.

3. The method of claim 1, wherein calculating an along-track angle comprises the steps of:

a) applying a Principal Component Analysis on the first and second horizontal acceleration components;

b) calculating an along-track angle using outputs of the Principal Component Analysis; and

c) transforming the horizontal acceleration components using the along-track angle to generate an along-track acceleration component and a cross-track acceleration component;

wherein step e) of claim 1 further comprises detecting if the 180 degrees error in the along-track angle is present based on the use case, the along-track acceleration component and the vertical acceleration component.

4. The method of claim 1, wherein calculating an along-track angle comprises the steps of:

a) applying a Principal Component Analysis on the first and second horizontal acceleration components;

b) calculating an along-track angle using outputs of the Principal Component Analysis; and

c) transforming the horizontal acceleration components using the along-track angle to generate an along-track acceleration component and a cross-track acceleration component;

wherein step e) of claim 1 further comprises detecting if the 180 degrees error in the along-track angle is present based on the use case, the along-track acceleration component and the vertical acceleration component, or declaring no decision; and

wherein step f) of claim 1 further comprises calculating the misalignment angle, in case e) does not declare no decision, from the along-track angle and, if present, the 180 degrees error.

5. The method of one of claims 3 or 4, wherein the detection if a 180 degrees error is present in the along-track angle is further based on one or more of the following components selected from:

the cross-track acceleration component, the magnitude of the first and second horizontal acceleration components, or the magnitude of the first and second horizontal and the vertical acceleration components.

6. The method of claim 4, wherein if the method declares no decision, then further using buffered information to calculate the misalignment angle.

7. The method of any one of claims 2, 3, 4, 5, or 6, wherein the method may further comprise enhancing the misalignment angle using self-contained information.

8. The method of any one of claims 2, 3, 4, 5, 6, or 7, wherein the method may further comprise enhancing the calculated misalignment angle from absolute navigational information.

9. The method of any one of claims 2, 3, 4, 5, 6, 7, or 8, wherein the method may further comprise calculating a standard deviation for the calculated misalignment angle.

11. The device of claim 1, wherein the processor is operative to calculate an along-track angle by applying a maximum possible variance technique on the first and second acceleration components.

10. A device portable by a pedestrian, the device comprising:

a) a tri-axial accelerometer; and

b) a processor, coupled to receive readings from the tri-axial accelerometer, and operative to determine the misalignment between the device and the pedestrian, wherein the processor is operative to;

i) calculate a plurality of levelled accelerometer readings from readings of the tri-axial accelerometer by transforming the tri-axial accelerometer readings into a levelled vertical accelerometer reading component and first and second horizontal acceleration components;

ii) generate a vertical acceleration component from the levelled vertical accelerometer reading component;

iii) calculate an along-track angle,

iv) determine a use case of the device;

v) determine if a 180 degrees error in the along-track angle is present based on the use case; and

vi) calculate a misalignment angle from the along-track angle and, if present, the 180 degrees error.