Vehicle Steering Device Fail-Safe via Partial Sensor Redundancy

Solution Overview

Problem

Vehicle steering systems with mechanically separated steering and rotation mechanisms face challenges in achieving fail-safe functions due to potential communication failures between ECUs, leading to increased manufacturing costs from excessive redundancy.

Innovation Solution

A vehicle steering device configuration with a reaction force device, a drive device, a first control unit, a second control unit, and multiple rudder angle sensors, where the second control unit sets a detected steering angle and transmits it to the first control unit, allowing continued operation even if the communication system fails, thus achieving fail-safe functions with a simple configuration.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If multiple redundant components (sensors, control systems, communication systems) are provided to achieve fail-safe functions, then system reliability is improved, but manufacturing cost increases

Engineering Contradiction:

Improvefail-safe functionVSAvoidmanufacturing cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent applies partial redundancy by providing multiple rudder angle sensors (excessive in detection capability) while maintaining a single communication system (partial in communication redundancy). This selective application of redundancy achieves fail-safe steering angle detection without fully redundant communication paths, thereby improving reliability while controlling manufacturing costs.

Inventive Principle:

Principle #16Partial or excessive action

2Adaptability or versatility

If the steering mechanism and rotation mechanism are controlled by different ECUs, then system modularity is improved, but communication failure risk increases

Engineering Contradiction:

Improvesystem modularityVSAvoidcommunication failure risk

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent introduces an intermediary approach where the communication system transmits steering angle information between ECUs, and multiple rudder angle sensors provide redundant detection capability. This intermediary redundancy layer mitigates communication failure risk while preserving the modular architecture's adaptability benefits.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Ease of manufacture

If redundancy is minimized to reduce manufacturing cost, then ease of manufacture is improved, but system reliability deteriorates

Engineering Contradiction:

Improvemanufacturing costVSAvoidfail-safe function

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent applies partial redundancy by providing multiple rudder angle sensors (excessive in detection capability) while maintaining a single communication system (partial in communication redundancy). This selective application of redundancy achieves fail-safe steering angle detection without fully redundant communication paths, thereby improving reliability while controlling manufacturing costs.

Inventive Principle:

Principle #16Partial or excessive action

Data Source

PatentUS11975771B2Vehicle steering device

Publication Date: 2024.05.07 NSK LTD

AI summary

A vehicle steering device includes a reaction force device, a drive device, a first ECU configured to control the reaction force device, a second ECU configured to control the drive device, a first rudder angle sensor and a second rudder angle sensor each configured to detect a steering angle of a wheel and output the detected steering angle to the second ECU, and a communication line that transmits at least one of steering angles of the wheel as detected values of the first rudder angle sensor and the second rudder angle sensor from the second ECU to the first ECU.