Redundant Position Sensing Using Motor Drive Variable Estimation

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Solution Overview

Problem

Conventional multi-chip position sensors for motors are complex, expensive, and prone to simultaneous faults due to spatial and functional proximity, compromising safety in safety-critical applications.

Innovation Solution

A position sensor system comprising a primary sensor for direct position detection and a secondary sensor for indirect position estimation based on drive motor variables, providing redundant paths for position determination.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If multi-chip position sensors are used for redundant position detection, then reliability is improved, but device complexity and cost increase

Engineering Contradiction:

Improveredundant position detection reliabilityVSAvoidmulti-chip sensor complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The position detection function is segmented into two independent paths: a primary sensor path using a position sensor and a secondary sensor path using sensorless control. This segmentation allows each path to be simpler while collectively providing redundancy, avoiding the complexity of multi-chip sensors.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The control system is designed to perform both primary position detection (using position sensor data) and secondary position estimation (using sensorless control algorithms) within a single integrated system. This multi-functionality eliminates the need for separate multi-chip sensor assemblies while maintaining redundant detection capability.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Reliability

If multi-chip position sensors are used for redundant position detection, then reliability is improved, but cost increases

Engineering Contradiction:

Improveredundant position detection reliabilityVSAvoidmanufacturing cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

Instead of using expensive duplicate position sensor chips, the system creates a functional copy of position detection capability through sensorless control algorithms that estimate position from motor drive variables. This virtual copy is significantly cheaper while providing the required redundancy.

Inventive Principle:

Principle #26Copying

Solution Approach 2:

The secondary sensor path uses inexpensive measurements of motor drive variables (current, voltage, frequency) that are already available in the control system. These measurements serve as a low-cost redundant detection mechanism without requiring additional expensive sensor components.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

3Reliability

If multiple chips are integrated in a position sensor, then redundant detection is achieved, but susceptibility to simultaneous faults increases

Engineering Contradiction:

Improveredundant detection capabilityVSAvoidsimultaneous fault susceptibility

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The redundant detection system is segmented into spatially separated components: a physical position sensor and a virtual sensor through algorithmic estimation. This physical and functional separation ensures that faults affecting one path (e.g., sensor hardware failures) do not simultaneously affect the other path (e.g., control algorithm calculations), thereby reducing common mode failure risk.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The control unit acts as an intermediary that processes data from both the primary position sensor and the secondary sensorless control path. It reconciles and validates position information from both independent sources, providing a bridge between the physical sensor and the algorithmic estimation while maintaining fault isolation.

Inventive Principle:

Principle #24Intermediary (Mediator)

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

Ensures reliable position determination even if one sensor fails, reducing costs and complexity while maintaining safety in safety-critical applications.

Implementation Method 1

The primary sensor is a position sensor which has at least one of the following sensor elements: a magneto-resistive element, a Hall effect sensor, an optical sensor, a resistance sensor

Methodology Applied

Scientific EffectMagnetic field sensing: Magnetic Field

Implementation Method 2

The secondary sensor determines (or estimates) the position of the movable element on the basis of at least one of the following variables: a voltage signal for the drive motor, a current signal for the drive motor, an electromagnetic field caused by the drive motor

Methodology Applied

Scientific EffectElectromagnetic field detection: Electromagnetic Induction

Data Source

PatentUS20250321122A1Position Sensor and Method for Redundantly Determining a Position

Publication Date: 2025.10.16 KNORR BREMSE SYSTEME FUER NUTZFAHIZEUGE GMBH

AI summary

A position sensor for redundantly determining a position of an element which is able to be moved by a drive motor includes a primary sensor and a secondary sensor. The primary sensor is designed to sense the position of the movable element directly. The secondary sensor is designed to deduce the position of the movable element from at least one secondary measurement, the secondary measurement being based on a drive variable of the drive motor.