Dynamic gravity vector estimation for memory constrained devices

Patent metadata

Field	Value
Publication number	US-12436624-B2
Application number	US-202418916262-A
Country	US
Kind code	B2
Filing date	Oct 15, 2024
Priority date	Nov 28, 2022
Publication date	Oct 7, 2025
Grant date	Oct 7, 2025

Abstract

A device includes a memory and processing circuitry coupled to the memory. The processing circuitry, in operation: estimates an angular rate of change and determines a rotational versor based on the rotational data; and estimates a gravity vector based on the angular rate of change and the rotational versor. The processing circuitry generates a dynamic gravity vector based on the estimated gravity vector, a correction factor and an estimated error in estimated gravity vector. The processing circuitry estimates a linear acceleration and determines an acceleration versor based on the acceleration data, and determines the correction factor based on the linear acceleration. The processing circuitry estimates the error in the estimated gravity vector based on the acceleration versor.

First claim

The invention claimed is:

1. A non-transitory computer-readable medium having contents which configure a processing device to perform a method, the method comprising:
estimating an angular rate of change based on rotational data;
determining a rotational versor based on the rotational data;
estimating a gravity vector based on the angular rate of change and the rotational versor;
estimating a linear acceleration based on acceleration data;
determining an acceleration versor based on the acceleration data;
determining a correction factor based on the linear acceleration;
estimating an error in the estimated gravity vector based on the acceleration versor;
generating a dynamic gravity vector based on the estimated gravity vector, the correction factor and the estimated error in the estimated gravity vector; and
using the dynamic gravity vector to perform an operation of a software application, wherein the gravity vector is estimated according to:

g
prop

=

g

t
-
1

⁢
cos
⁢
θ

+

(

g

t
-
1

×

w
^

)

⁢
sin
⁢
θ

+

w
^

(

g

t
-
1

·

w
^

)

⁢

(

1
-

cos
⁢
θ

)

,

where g prop is the estimated gravity vector, θ is the estimated angular rate of change, and g t-1 is a previous dynamic gravity vector.

2. The non-transitory computer-readable medium according to claim 1 , wherein the method comprises:
generating the rotational data as a rotational velocity measurements vector indicating a rotational velocity with respect to three axes of movement; and
generating the acceleration data as an acceleration measurements vector indicating acceleration along the three axes of movement.

3. The non-transitory computer-readable medium according to claim 2 , wherein the method comprises:
estimating the angular rate of change according to:

θ
=

❘
"\[LeftBracketingBar]"

w

❘
"\[RightBracketingBar]"

⁢
dtime

,

where θ is the estimated angular rate of change, |w| is a magnitude of the rotational velocity measurements vector w and dtime is a delta-time interval;
determining the rotational versor according to:

w
^

=

w

❘
"\[LeftBracketingBar]"

w

❘
"\[RightBracketingBar]"

,

where ŵ is the determined rotational versor; and
generating the dynamic gravity vector according to:

g
t

=

g
prop

-

α
⁢
e

,

where g t is the dynamic gravity vector, g prop is the estimated gravity vector, α is the correction factor, and e is an error vector.

4. The non-transitory computer-readable medium according to claim 1 , wherein the contents comprising instructions executable by the processing device.

5. A method, comprising:
generating, using a gyroscope, rotational data;
estimating an angular rate of change based on the rotational data;
determining a rotational versor based on the rotational data;
estimating a gravity vector based on the angular rate of change and the rotational versor;
generating, using an accelerometer, an acceleration measurements vector indicating acceleration along a three axes of movement;
estimating a linear acceleration based on acceleration measurements vector;
determining an acceleration versor based on the acceleration measurements vector;
determining a correction factor based on the linear acceleration;
estimating an error in the estimated gravity vector based on the acceleration versor; and
generating a dynamic gravity vector based on the estimated gravity vector, the correction factor and the estimated error in the estimated gravity vector, wherein the acceleration versor is determined according to:

a
^

=

a

❘
"\[LeftBracketingBar]"

a

❘
"\[RightBracketingBar]"

where â is the acceleration versor, a is the acceleration measurements vector and |a| is a magnitude of the acceleration measur

Assignees

• St Microelectronics Srl
• Stmicroelectronics S Rl

Inventors

• Rizzardini Federico
• Bracco Lorenzo

Classifications

• G01V7/06

  Analysis or interpretation of gravimetric records · CPC title

• G06F3/0346 Primary

  with detection of the device orientation or free movement in a three-dimensional [3D] space, e.g. 3D mice, 6-DOF [six degrees of freedom] pointers using gyroscopes, accelerometers or tilt-sensors · CPC title

• G01C21/185 Primary

  for gravity · CPC title