Dynamic Gravity Vector Estimation Without 3D Orientation

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Solution Overview

Problem

Existing gravity vector estimation methods in portable electronic devices require substantial memory and computational resources due to the generation of a 3D orientation representation, leading to high latency and lack of robustness against accelerations.

Innovation Solution

Directly estimate a dynamic gravity vector based on gyroscope data and correct it using a linear acceleration correction factor derived from accelerometer data, bypassing the need for a 3D orientation representation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a 3D orientation representation is generated using existing gravity vector estimation methods, then the gravity vector can be estimated, but memory and computational resources are substantially increased

Engineering Contradiction:

Improvegravity vector estimation accuracyVSAvoidmemory and computational resources

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent extracts only the essential computational elements needed for gravity vector estimation, eliminating the need to generate a full 3D orientation representation. By directly estimating the gravity vector from accelerometer and gyroscope data through mathematical operations (normalization, cross products, and trigonometric calculations), the method removes unnecessary computational overhead while maintaining estimation accuracy

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

Instead of following the conventional approach of first determining 3D orientation and then deriving gravity vector from it, the patent inverts the process by directly computing the gravity vector from sensor measurements using inverse trigonometric relationships and vector mathematics, thereby bypassing the complex orientation representation step

Inventive Principle:

Principle #13The other way round (Inversion)

2Measurement precision

If a 3D orientation representation is generated using existing gravity vector estimation methods, then the gravity vector can be estimated, but execution time increases due to high latency

Engineering Contradiction:

Improvegravity vector estimation accuracyVSAvoidexecution time and latency

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent skips the intermediate step of generating a complete 3D orientation representation and rushes directly to computing the gravity vector through optimized mathematical operations. This approach bypasses redundant calculations and reduces the computational pipeline length, thereby decreasing execution time and latency

Inventive Principle:

Principle #21Skipping (Rushing through)

3Measurement precision

If a 3D orientation representation is generated using existing gravity vector estimation methods, then the gravity vector can be estimated, but robustness against accelerations is reduced

Engineering Contradiction:

Improvegravity vector estimation accuracyVSAvoidrobustness against accelerations

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent implements a dynamic correction mechanism that continuously adjusts the gravity vector estimation based on detected linear accelerations. By monitoring the magnitude of acceleration vectors and applying correction factors when linear acceleration exceeds gravitational acceleration, the method adapts to dynamic conditions and maintains robustness against various acceleration scenarios

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent incorporates a feedback loop where the estimated gravity vector is continuously validated against accelerometer measurements. When discrepancies indicate the presence of linear acceleration, correction factors are applied to refine the gravity vector estimate, ensuring robustness against external accelerations while maintaining accuracy during static conditions

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS12436624B2Dynamic gravity vector estimation for memory constrained devices

Publication Date: 2025.10.07 STMICROELECTRONICS SRL

AI summary

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.