Self-Calibrating Magnetic Angle Sensor for Shaft Misalignment

Solution Overview

Problem

Magnetic sensors used to calculate the angle of a rotating shaft in motors suffer from misalignment errors due to manufacturing tolerances, leading to inaccurate angle calculations and the need for large memory-intensive look-up tables for calibration.

Innovation Solution

An integrated circuit with multiple orthogonally-arranged magnetic sensors that self-calibrate by determining interim rotation matrices and a calibration matrix to correct for misalignment, eliminating the need for manual calibration and large look-up tables.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If manual calibration using large look-up tables is used, then measurement precision is improved, but device complexity and memory requirements increase

Engineering Contradiction:

Improveangle calculation accuracyVSAvoidsystem complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The angle sensor performs self-calibration automatically by executing a calibration routine that determines rotation matrices and compensation values without external intervention. The sensor uses its own sensor values during rotation to compute calibration parameters, eliminating the need for manual calibration procedures and large look-up tables while maintaining high measurement precision.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The system changes the approach from storing pre-computed calibration data in large memory structures to dynamically computing calibration parameters (rotation matrices and compensation values) during operation. This transforms the calibration process from a static memory-intensive approach to a dynamic calculation-based approach, reducing memory requirements while maintaining accuracy.

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If manual calibration using large look-up tables is used, then measurement precision is improved, but manufacturing cost increases

Engineering Contradiction:

Improveangle calculation accuracyVSAvoidmanufacturing cost

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The angle sensor performs self-calibration automatically by executing a calibration routine that determines rotation matrices and compensation values without external intervention. The sensor uses its own sensor values during rotation to compute calibration parameters, eliminating the need for manual calibration procedures and large look-up tables while maintaining high measurement precision.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The system changes the approach from storing pre-computed calibration data in large memory structures to dynamically computing calibration parameters (rotation matrices and compensation values) during operation. This transforms the calibration process from a static memory-intensive approach to a dynamic calculation-based approach, reducing memory requirements while maintaining accuracy.

Inventive Principle:

Principle #35Parameter changes

3Device complexity

If self-calibration using rotation matrices is used, then device complexity is reduced, but measurement precision may worsen due to computational approximations

Engineering Contradiction:

Improvesystem complexityVSAvoidangle calculation accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The calibration routine uses feedback from the sensor's own measurements during rotation to iteratively determine accurate rotation matrices and compensation values. By continuously monitoring sensor values and adjusting calibration parameters based on actual rotational behavior, the system achieves high measurement precision through computationally efficient feedback-driven optimization rather than relying on complex pre-stored lookup tables.

Inventive Principle:

Principle #23Feedback

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

Accurately calculates the angle of a rotating shaft without manual calibration, reducing system complexity and cost by minimizing memory requirements.

Implementation Method 1

A magnet positioned on the rotating shaft rotates with the shaft, and the magnetic sensors sense the rotating magnetic field of the magnet.

Methodology Applied

Scientific EffectMagnetic field sensing: Magnetic Field

Data Source

PatentUS20250271284A1Self-calibrating angle sensor

Publication Date: 2025.08.28 TEXAS INSTRUMENTS INC

AI summary

An integrated circuit (IC) includes first, second, and third magnetic sensors. An analog-to-digital converter (ADC) has an input coupled to the first, second, and third magnetic sensors, and has an output. A digital circuit has an input coupled to the output of the ADC. The digital circuit is configured to obtain first digital sensor values from the ADC, determine interim rotation matrices for rotation of the first digital sensor values, and determine a calibration matrix based on the interim rotation matrices.