Position Detection Device for Steer-by-Wire Systems

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Solution Overview

Problem

Existing rotation angle detection devices for electric power steering systems face challenges in accurately detecting rotations due to mechanical tooth skipping, which can lead to incorrect angle calculations.

Innovation Solution

A position detection device comprising a first positional sensor mounted on a reference portion and a second positional sensor mounted on a detection target movable relative to the reference portion, with a controller calculating the position of the detection target based on the detection values from both sensors, allowing direct position detection without gears or belts.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If mechanical transmission components (gears or belts) are used to connect the motor and steering wheel, then the motor can drive the steering wheel, but mechanical tooth skipping occurs leading to incorrect angle detection

Engineering Contradiction:

Improvemotor-driven steering capabilityVSAvoidrotation angle detection accuracy

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent replaces the mechanical transmission system (gears or belts) with a direct magnetic coupling system. A magnet is attached to the motor shaft and a positional sensor detects its position directly, eliminating mechanical transmission components that cause tooth skipping and detection errors.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces a magnet as an intermediary between the motor shaft and the positional sensor. The magnet serves as a non-contact mediator that transmits rotational position information from the motor to the sensor without mechanical contact, preventing tooth skipping issues.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Device complexity

If a single positional sensor is used to detect motor position, then the structure is simple, but the detection accuracy is insufficient

Engineering Contradiction:

Improvesensor system structureVSAvoidposition detection accuracy

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The patent divides the detection system into two independent positional sensors instead of using one sensor. Each sensor detects the position of the magnet at different locations, and the controller integrates both detection values to calculate the motor shaft position, improving overall detection accuracy.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS12325476B2Position detection device

Publication Date: 2025.06.10 DENSO CORP

AI summary

A position detection device includes a first positional sensor mounted on a reference portion, and a second positional sensor mounted on a detection target that is movable relative to the reference portion. A controller calculates a position of the detection target based on a detection value of the first positional sensor and a detection value of the second positional sensor. The position detection device may be applied to a steer-by-wire system for a vehicle. The reference portion may be a fixed portion of the vehicle, and the detection target may be a steering wheel or a vehicle wheel of the vehicle. The controller may calculate a steering angle of the steering wheel or a turning angle of the vehicle wheel as the position of the detection target.